阅读说明：本技术 用于发送数据和用于光收发器的方法 (Method for transmitting data and for optical transceiver ) 是由 G·弗罗克 于 2020-01-22 设计创作，主要内容包括：提出了一种在光分配网络的光源中发送数据的方法。该方法包括：获取光源的发送从非发送切换到数据发送时出现的频率失谐损害的特性；以及基于频率失谐损害的特性发送数据。(A method of transmitting data in a light source of an optical distribution network is proposed. The method comprises the following steps: acquiring characteristics of frequency detuning damage occurring when the transmission of the light source is switched from non-transmission to data transmission; and transmitting data based on the characteristics of the frequency detuning impairments.)

1. A method for transmitting data in an optical source of an optical distribution network, the method comprising the steps of:

acquiring characteristics of frequency detuning damage occurring when transmission of the light source is switched from non-transmission to data transmission; and

transmitting data based on the characteristic of the frequency detuning impairment.

2. The method of claim 1, wherein obtaining characteristics of the frequency detuned impairments comprises: data relating to the duration of the frequency detuning damage is acquired.

3. The method of claim 2, wherein the duration of the frequency detuning impairment comprises a first duration and a second duration in succession, wherein the first duration corresponds to a peak of the frequency detuning and the second duration corresponds to a decay of the frequency detuning.

4. The method of claim 2 or claim 3, wherein transmitting data based on the characteristic of the frequency detuning impairment comprises: transmitting data with a time shift, wherein the time shift is based on a duration of the frequency detuning impairment being above a predetermined threshold.

5. The method of claim 3 or claim 4, wherein the time shift is based on a combination of portions of the first and second durations for which the frequency detuning is above a predetermined threshold.

6. A method according to claim 3 or claim 4, wherein the time shift is based on an estimate of the duration between the end of the last data transmission and the next activation of the light source.

7. The method of claim 1, wherein obtaining characteristics of the frequency detuning impairment comprises obtaining an estimate of the frequency detuning impairment, and transmitting data comprises processing an optical signal carrying the data to compensate for the frequency detuning impairment based on the estimate of frequency detuning.

8. The method of claim 3 or claim 7, wherein transmitting data based on the characteristic of the frequency detuning impairment comprises: transmitting data with a time shift, wherein the time shift is based on a first duration of the frequency detuned impairment, wherein obtaining characteristics of the frequency detuned impairment comprises obtaining an estimate of the frequency detuned impairment during a second duration of the frequency detuned impairment, and wherein transmitting data further comprises processing an optical signal carrying the data to compensate for the frequency detuned impairment based on the estimate of the frequency detuned impairment.

9. A method for an optical transceiver in an optical distribution network, the method comprising:

transmitting, by a transmitting side of the optical transceiver, a second transmitted optical signal according to the method of any one of claims 1 to 8;

receiving data in an optical transceiver of an optical distribution network, wherein the receiving data comprises:

receiving a received optical signal at a receive side of the optical transceiver, wherein the received optical signal corresponds to a first transmitted optical signal carrying data transmitted by an optical source over a first transmit link comprising an optical fiber;

determining an interference component of an interference signal in the received optical signal, wherein the interference component is introduced by the transmitting side of the optical transceiver transmitting the second transmitted optical signal over a second transmit link including the optical fiber; and

processing the received optical signal based on the determined interference component to obtain an estimate of the first transmitted optical signal,

wherein determining the interference component comprises: a combination of the contribution signals introduced from the respective counter-propagating of the transmitted second transmitted optical signals is characterized.

10. The method of claim 9, further comprising the steps of: an amplitude distortion component of the interference component is determined and the amplitude distortion component is removed from the received optical signal.

11. The method according to claim 9 or claim 10, further comprising the steps of: a phase distortion component of the interference component is determined and removed from the received optical signal.

12. The method of claim 11, wherein at least one contributing signal is generated by back reflection of the transmitted second transmitted optical signal on a network node included in the second transmit link, such as a power splitter or an optical connector of the optical distribution network.

13. An apparatus comprising a processor, a memory operably coupled to the processor, and a network interface to communicate in an optical distribution network, wherein the apparatus is configured to perform the method of any of claims 1 to 8.

14. An optical transceiver of an optical distribution network, the optical transceiver comprising the apparatus of claim 13.

15. A computer program product comprising computer program code tangibly embodied in a computer-readable medium, the computer program code comprising instructions that, when provided to a computer system and executed, cause the computer to perform the method of any of claims 1 to 12.

Technical Field

The present disclosure relates to the field of optical networks, and in particular to optical access networks using optical fibers for data communications.

Background

Optical networks using optical fibers have long used network topologies such as point-to-point topologies (IEEE series), passive optical networks (e.g., g.987, G988 series), including Time and Wavelength Division Multiplexed (TWDM) Passive Optical Networks (PONs) (g.989 series) and general wavelength division multiplexed WDM-PONs (g.989 series). Light-to-point data transmission typically uses one wavelength on two fibers, each dedicated to transmission in one direction. Passive optical networks (e.g., g.987, G988 series) also use one wavelength on one fiber, with power split into multiple fibers to reach different end users. On the same Optical Distribution Network (ODN) there is usually one wavelength downstream and a different wavelength upstream. The wavelengths on the upstream and downstream are sufficiently distant from each other to provide isolation characteristics between signals carried by the two wavelengths with low complexity and low cost. PON systems may provide speeds up to 10 gigabits per second (Gbps) using NRZ modulation. TWDM PON (g.989 series) systems use multiple wavelength pairs stacked on top of each other on the same ODN. As defined by the ITU, a TWDM PON system is a multi-wavelength PON system in which each wavelength channel can be shared between multiple ONUs by employing time division multiplexing and multiple access mechanisms. Based on NRZ modulation, TWDM PON systems can provide up to 4 channels at 10Gbps line rates. In point-to-point (PtP) WDM PON (g.989 series) systems, different PON systems (possibly corresponding to different end user groups) are multiplexed and demultiplexed on the same ODN using wavelength multiplexing/demultiplexing (possibly using additional power splitters). As defined by the ITU, a PtP WDM PON system is a multi-wavelength PON system that implements point-to-point connections using one dedicated wavelength channel per ONU for the downstream direction and one dedicated wavelength channel per ONU for the upstream direction. The wavelength linking the optical terminal and the optical network unit (end user) may be selected while the system is operating in a tunable manner, i.e. tuned to a target transmission wavelength. Such wavelength-common WDM-PON systems can provide rates up to 10Gbps per line using NRZ modulation.

In 2017, a new optical transceiver, commonly referred to as a "BiDi" transceiver, was introduced on the market with the capability of transmitting data bi-directionally over a single fiber, with a maximum transmission rate of about 10 Gbps.

Since 2015-. In addition, telecommunications operators have several requirements for fronthaul optical access, including: for point-to-point communication, in contrast to IEEE traditional point-to-point technology, an uplink communication link and a downlink communication link should be provided on a unique optical fiber, i.e. a communication link is provided in each direction. In addition to this advantage, this reduces the number of optical fibers by half, which also significantly reduces the size of the housing and maintenance work.

Therefore, there is a need to limit the number of optical fibers used for data communication between a plurality of users in an optical access network, which leads to a solution and corresponding optical components that allow multiplexing a plurality of users on a single optical fiber.

Additional cost constraints also need to be considered, since it is desirable to reuse low-cost components, e.g. transceivers and multiplexer/demultiplexer devices developed for optical network technology, such as CWDM (coarse wavelength division multiplexing) or DWDM (dense wavelength division multiplexing), where bidirectional data communication signals are multiplexed for multiple users on a single optical fiber. Reusing, at least in part, such conventional techniques developed and deployed for optical networks other than optical distribution networks creates several technical challenges when used in optical access networks, particularly in view of the use of adjacent wavelengths of upstream and downstream optical signals for each user. These challenges become more pronounced and other challenges arise when considering optical access networks that use BiDi transceivers and operate at line rates in excess of 10 Gbps.

Furthermore, the transmitter side of the BiDi transceiver may be subject to impairments experienced by any light source when transmitting data, which may become more problematic as such transmitter side may be used for multiplexing data transmissions of users.

Therefore, there is a need to provide an improved scheme for operating a light source, and a network node implementing the scheme, to address the above-mentioned drawbacks and deficiencies of the conventional art in the art.

It is also desirable to provide an improved scheme for operating an optical network node, such as an optical transceiver including an optical source, and an optical transceiver implementing the scheme, to address the above-mentioned shortcomings and deficiencies of conventional techniques in the art. .

It is an object of the present disclosure to provide an improved scheme for operating an optical network node and a network node implementing the scheme.

It is another object of the present disclosure to provide an improved solution for operating a light source of an optical distribution network and an apparatus implementing the solution.

It is a further object of the present disclosure to provide an improved scheme for operating an optical transceiver of an optical distribution network and an optical transceiver implementing the scheme.

It is a further object of the present disclosure to provide an improved scheme for transmitting data in a light source and a light source implementing the scheme.

It is a further object of the present disclosure to provide an improved scheme for transmitting data in an optical transceiver and an optical transceiver implementing the scheme.

To achieve these objects and other advantages and in accordance with the purpose of the disclosure, as embodied and broadly described herein, in one aspect of the present disclosure, a method for transmitting data in a light source of an optical distribution network is proposed. The method comprises the following steps:

acquiring characteristics of frequency detuning damage occurring when transmission of the optical transceiver is switched from non-transmission to data transmission; and

data is transmitted based on the characteristics of frequency detuning impairments.

In some embodiments, obtaining the characteristic of the frequency detuned damage may include obtaining data related to a duration of the frequency detuned damage.

In some embodiments, the duration of the frequency detuning damage may include a first duration and a second duration in succession, wherein the first duration corresponds to a peak of the frequency detuning and the second duration corresponds to a decay of the frequency detuning.

In some embodiments, transmitting data based on characteristics of frequency detuning impairments may include: transmitting data with a time shift, wherein the time shift is based on a duration of the frequency detuning impairment.

In some implementations, the time shift may be based on a combination of the first duration and the portion of the second duration where the frequency detuning is above a predetermined threshold.

Disclosure of Invention

In some embodiments, the time shift may be based on an estimate of the duration between the end of the last data transmission and the next activation of the light source.

In some implementations, obtaining the characteristic of the frequency detuning impairment may include obtaining an estimate of the frequency detuning impairment, and transmitting the data may include processing the optical signal carrying the data to compensate for the frequency detuning impairment based on the estimate of the frequency detuning.

In some embodiments, transmitting data based on characteristics of frequency detuning impairments may include: transmitting data with a time shift, wherein the time shift is based on a first duration of the frequency detuning impairment, obtaining characteristics of the frequency detuning impairment may comprise: obtaining an estimate of the frequency detuning impairment during a second duration of the frequency detuning impairment, and transmitting the data may further comprise processing the data-carrying optical signal to compensate for the frequency detuning impairment based on the estimate of the frequency detuning impairment.

In another aspect of the present disclosure, a method for an optical transceiver in an optical distribution network is presented, the method comprising: transmitting, by a transmitting side of an optical transceiver, a second transmitting optical signal according to a method for transmitting data in an optical source according to the present disclosure, receiving the data in the optical transceiver of the optical distribution network, wherein the receiving includes: receiving a received optical signal at a receive side of an optical transceiver, wherein the received optical signal corresponds to a first transmit optical signal carrying data transmitted by an optical source over a first transmit link comprising an optical fiber; determining an interference component of an interference signal in the received optical signal, wherein the interference component is introduced by a transmitting side of the optical transceiver transmitting a second transmitted optical signal on a second transmission link including an optical fiber; and processing the received optical signal based on the determined interference component to obtain an estimate of the first transmitted optical signal, wherein determining the interference component comprises characterizing a combination of the contributing signals introduced from the respective back-propagation of the transmitted second transmitted optical signal.

In some embodiments, the proposed method for an optical transceiver in an optical distribution network may further include: an amplitude distortion component of the interference component is determined and the amplitude distortion component is removed from the received optical signal.

In some embodiments, the proposed method for an optical transceiver in an optical distribution network may further include: a phase distortion component of the interference component is determined and the phase distortion component is removed from the received optical signal.

In some embodiments, the at least one contributing signal is generated by back-reflection of the transmitted second transmitted optical signal on a network node (such as an optical connector or power splitter of an optical distribution network) included in the second transmit link.

In yet another aspect of the present disclosure, a method for an optical transceiver in an optical distribution network is presented, the method comprising: transmitting, by a transmitting side of an optical transceiver, a second transmission optical signal according to a method of transmitting data in an optical source of the present disclosure, receiving data in the optical transceiver of an optical distribution network, wherein the receiving includes: receiving a received optical signal at a receive side of the optical transceiver, wherein the received optical signal corresponds to a first transmitted optical signal carrying data transmitted by an optical source over a first transmit link comprising an optical fiber; determining an interference component of an interference signal in the received optical signal, wherein the interference component is introduced by a transmitting side of the optical transceiver transmitting a second transmitted optical signal on a second transmission link including an optical fiber; and processing the received optical signal based on the determined interference component to obtain an estimate of the first transmitted optical signal.

In some embodiments, the received optical signal and the second transmitted optical signal correspond to a downstream channel and an upstream channel, respectively, of a bidirectional optical signal of a plurality of bidirectional optical signals transmitted over an optical fiber using frequency multiplexing.

In some embodiments, the first transmitted optical signal and the second transmitted optical signal have adjacent carrier frequencies, wherein receiving the received optical signal comprises: the received signal is filtered to separate the bi-directional optical signal from other signals in the plurality of bi-directional optical signals.

In some embodiments, the proposed method for an optical transceiver may further comprise: an amplitude distortion component of the interference component is determined and the amplitude distortion component is removed from the received optical signal.

In some embodiments, the proposed method for an optical transceiver may further comprise: a phase distortion component of the interference component is determined and the phase distortion component is removed from the received optical signal.

Thus, the proposed compensation scheme may advantageously be designed such that only the amplitude distortion component is compensated, or both the amplitude and phase distortion components are compensated.

In some embodiments, determining the interference component may include characterizing a combination of contributing signals introduced from respective back-propagation of the transmitted second transmitted optical signal.

In some embodiments, the at least one contributing signal is generated by back-reflection of the transmitted second transmitted optical signal on a network node (such as an optical connector or power splitter of an optical distribution network) included in the second transmit link.

In one or more embodiments, determining the interference component may include: stopping transmission of all light sources except for a transmission side of the optical transceiver in the optical distribution network; transmitting a predetermined signal at a transmitting side of the optical transceiver once none of the light sources other than the optical transceiver transmits; and recording a reception signal corresponding to the transmission predetermined signal at a reception side of the optical transceiver.

In some embodiments, the determination of the interference component may include: an estimate of a first attenuation coefficient of a first signal component of the received optical signal corresponding to the transmitted first transmitted optical signal is determined.

In some embodiments, the processing of the received optical signal may include: an estimate of a second attenuation coefficient of a second signal component of the received optical signal corresponding to the transmitted second transmitted optical signal is determined.

In some embodiments, the determination of the interference component may include: an estimate of the phase shift coefficient is determined based on a first carrier frequency of the first transmitted optical signal and a second carrier frequency of the second transmitted optical signal.

In another aspect of the present disclosure, an apparatus is presented that includes a processor, a memory operably coupled to the processor, and a network interface to communicate in an optical distribution network, wherein the apparatus is configured to perform a method as presented in the present disclosure. An optical transceiver of an optical distribution network comprising such a device is also proposed.

In yet another aspect of the disclosure, a non-transitory computer readable medium encoded with executable instructions, when executed, cause an apparatus comprising a processor operably coupled with a memory to perform a method as set forth in the disclosure.

In yet another aspect of the disclosure, a computer program product comprising computer program code tangibly embodied in a computer-readable medium, the computer program code comprising instructions that when provided to a computer system and executed cause the computer to perform a method as set forth in the disclosure. In another aspect of the present disclosure, a data set is presented, for example by compression or encoding, representing a computer program as presented herein.

It should be appreciated that the present invention can be implemented and utilized in numerous ways, including but not limited to as a process, an apparatus, a system, a device, and as a method for applications now known and later developed. These and other unique features of the system disclosed herein will become more apparent from the following description and the accompanying drawings.

The present disclosure will be better understood and its numerous objects and advantages will become more apparent to those skilled in the art by reference to the following drawings taken in conjunction with the accompanying specification.

Drawings

[ FIG. 1a ]

Fig. 1a shows an example of a point-to-point topology network.

[ FIG. 1b ]

Fig. 1b shows an example of a PON topology network.

[ FIG. 2a ]

Fig. 2a illustrates a bidirectional topology using wavelength division multiplexing in accordance with one or more embodiments.

[ FIG. 2b ]

Fig. 2b shows the side-mode power contribution in the light source.

[ FIG. 2c ]

Fig. 2c illustrates frequency detuning damage to be addressed by a light source according to one or more embodiments.

[ FIG. 2d ]

Fig. 2d illustrates frequency detuning damage to be addressed by the light source according to one or more embodiments.

[ FIG. 2e ]

Fig. 2e illustrates frequency detuning damage to be addressed by the light source according to one or more embodiments.

[ FIG. 3]

Fig. 3 is a block diagram illustrating an exemplary optical transceiver in accordance with one or more embodiments.

[ FIG. 4a ]

Fig. 4a is a block diagram illustrating an exemplary data transmission process in accordance with one or more embodiments.

[ FIG. 4b ]

Fig. 4b is a block diagram illustrating an exemplary data reception process in accordance with one or more embodiments.

[ FIG. 5]

Fig. 5 illustrates an exemplary optical network in accordance with one or more embodiments.

[ FIG. 6]

Fig. 6 illustrates an exemplary reverse channel knowledge acquisition process in accordance with one or more embodiments.

[ FIG. 7]

FIG. 7 illustrates an exemplary detuning measurement process in accordance with one or more embodiments.

[ FIG. 8]

FIG. 8 illustrates exemplary impairment compensation in accordance with one or more embodiments.

[ FIG. 9]

Fig. 9 illustrates an exemplary transceiver in accordance with one or more embodiments.

Detailed Description

For simplicity and clarity of illustration, the drawing figures show a general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the discussion of the described embodiments of the invention. Furthermore, elements in the drawings figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. Some of the figures may be shown in idealized form to aid understanding, such as when structures are shown having straight lines, acute angles, and/or parallel planes, etc., which may be significantly less symmetrical and ordered under real world conditions. Like reference symbols in the various drawings indicate like elements, and similar reference symbols may, but do not necessarily, indicate similar elements.

Moreover, it should be apparent that the teachings herein may be embodied in a wide variety of forms and that any specific structure and/or function disclosed herein is merely representative. In particular, those skilled in the art will appreciate that one aspect disclosed herein may be implemented independently of any other aspects and that several aspects may be combined in various ways.

The present disclosure is described below with reference to functional, engine, block and flow diagram illustrations of methods, systems, and computer programs in accordance with one or more exemplary embodiments. Each described function, engine, block diagram, and block diagram of the flowchart illustrations may be implemented in hardware, software, firmware, middleware, microcode, or any suitable combination thereof. If implemented in software, the functions, engines, blocks of the block diagrams and/or flowchart illustrations may be implemented by computer program instructions or software code, which may be stored or transmitted on a computer-readable medium, or loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the computer program instructions or software code which execute on the computer or other programmable data processing apparatus create means for implementing the functions described herein.

Embodiments of computer readable media include, but are not limited to, both computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. As used herein, a "computer storage medium" can be any physical medium that can be accessed by a computer or a processor. Furthermore, the terms "memory" and "computer storage medium" include any type of data storage device, such as, but not limited to, a hard disk drive, a flash memory drive or other flash memory device (e.g., a storage key, memory stick, key drive), a CD-ROM or other optical storage, a DVD, a magnetic disk storage or other magnetic storage device, a memory chip, Random Access Memory (RAM), Read Only Memory (ROM), electrically erasable programmable read-only memory (EEPROM), a smart card, or any other suitable medium that can be used to carry or store program code in the form of instructions or data structures readable by a computer processor, or a combination thereof. In addition, various forms of computer readable media may transmit or carry instructions to a computer, including a router, gateway, server, or other transmitting device, wired (coaxial, fiber optic, twisted pair, DSL cable), or wireless (infrared, radio, cellular, microwave). The instructions may include code from any computer programming language, including but not limited to assembly, C, C + +, Python, Visual Basic, SQL, PHP, and JAVA.

Unless specifically stated otherwise, it is appreciated that throughout the following description, discussions utilizing terms such as processing, computing, calculating, determining, or the like, refer to the action and processes of a computer or computing system, or similar electronic computing device, that manipulate or transform data represented as physical, such as electronic, quantities within the computing system's registers and memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices.

The terms "comprises," "comprising," "includes," "including," "has," "having," and any variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Moreover, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

In the following description and claims, the terms "coupled" and "connected," along with their derivatives, may be used indifferently to indicate that two or more elements are in direct physical or electrical contact with each other, or that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other.

In the following description, the terms "source," "light source," "transmitter," "optical transmitter," "transmitter side," and "transmit side" may be used indifferently to refer to any device or apparatus that may be implemented in hardware, or as a combination of hardware and software, either incorporated or not in an optical transceiver, configured to transmit optical signals carrying data in an optical network (e.g., an optical distribution network).

For the purposes of this disclosure, an "optical network" should be understood to refer to a network (including the use of optical fibers) to which devices (also referred to herein as "nodes") may be coupled so that optical data communications may be made between the devices. Any number of nodes, devices, apparatuses, links, interconnections, etc. may be used in an optical network in accordance with the present disclosure.

A computing device (e.g., a receiver, a transmitter (e.g., an optical/electrical composite device including a laser source device), or a transceiver) of an optical network can transmit and/or receive signals, such as via one or more optical fibers, and/or can process and/or store data.

It should be understood that embodiments of the present disclosure may be used in a variety of applications, particularly but not limited to optical distribution networks.

Fig. 1a schematically shows an exemplary point-to-point topology typically used for conventional optical access.

Fig. 1a shows a network (1) in which two optical network nodes (2,3) are connected to each other for data communication by two optical fibers (4a, 4 b).

Point-to-point topology uses one wavelength (λ) on the fiber in one direction of the communication link₁) Optical communication is performed while using the same wavelength (lambda) on the other fiber for the other direction₁). In other words, the same wavelength is used for transmitting optical signals on two different optical fibers (4a, 4b) dedicated to data transmission in one direction and in the opposite direction, respectively. Throughout this disclosure, the opposite direction from the perspective of the network node, one direction corresponding to the network node transmitting data, and the opposite direction corresponding to the network node receiving data will be referred to indiscriminately as "upstream" and "downstream", "uplink", and "downlink". The data transmitted through one of the optical fibres (4a, 4b) typically undergoes an attenuation of about 0.5dB/km, depending on the type of optical fibre used (in optical fibre networks the attenuation is typically about 0.15dB/km at operating wavelengths around 1550nm and about 0.55dB/km at operating wavelengths around 1300 nm). For example, assuming a fiber length of about 40km, the attenuation from the data source (2,3) to the well (3,2) is about 4.5 dB. Based on NRZ modulation, this point-to-point topology can provide line rates up to 25Gbps in the C-band at a wavelength of about 1550 nm.

Fig. 1b schematically shows an exemplary PON topology that would typically also be used for conventional optical access.

Fig. 1b shows a network (10) in which a central node (11) is connected to a plurality of network nodes (13a … 13n) through power splitter nodes (12), each pair of two nodes using two wavelengths (λ @)₁And λ₂) (one wavelength per communication direction) are connected by a single optical fiber.

Fig. 2 illustrates an exemplary bi-directional topology in which multiple downstream/upstream channel pairs are conveyed over a single fiber.

In contrast to the point-to-point topology shown in fig. 1a, where the uplink channel is transmitted through a first optical fiber and the downlink channel is transmitted through a second optical channel, the uplink channel and the downlink channel use the same wavelength, and the bidirectional topology uses frequency multiplexing to transmit the uplink channel and the downlink channel on the same optical fiber: the uplink channel and the downlink channel use adjacent frequency resources, i.e., adjacent wavelengths. The frequency reuse may be used to convey multiple pairs of uplink and downlink channels, where each pair may correspond to one user.

Indeed, in order to optimize the resource consumption in point-to-point topology optical networks, whether using a single fiber or two fibers (one fiber in each direction), it is beneficial to multiplex as many users as possible on the same fiber resource. In particular, in optical access networks, resource utilization efficiency is a key requirement to address as many users as possible with limited resources. When only one fiber is used, different users can be multiplexed by using a different pair of wavelengths for each user (one wavelength for the downstream channel and one wavelength for the upstream channel).

Another requirement, particularly for optical access networks, is the use of components that are simple enough in design and manufacture to limit their cost and meet strict cost constraints. Existing components (such as transceivers) are often reusable for this problem. These transceivers were developed for CWDM or DWDM technology, where each subscriber is assigned a pair of adjacent wavelengths with a filter width suitable for demultiplexing by the subscriber, so that discrimination between subscribers can be performed at a low cost transceiver component using optical band pass filters.

For example, fig. 2 shows four pairs of upstream and downstream channels. The pairs are frequency multiplexed using Wavelength Division Multiplexing (WDM) such that the respective center wavelengths of adjacent pairs of upstream channels are separated by approximately 100 GHz. For each pair, the center wavelength used by the upstream channel of the pair is less than 50GHz from the center wavelength used by the downstream channel of the pair. This corresponds to a channel spacing value specified for DWDM (dense wavelength division multiplexing) systems, which allows more information to be transmitted simultaneously than CWDM (coarse wavelength division multiplexing) systems and is typically used for optical data communication in core network subsystems of wireless cellular network systems, such as 3GPP networks (e.g. GSM, UMTS, HSPA, LTE-a, etc.).

Fig. 2 also shows that the same filtering template (e.g., in a splitter (diplexer device), possibly based on filtering techniques), that can be adapted for each pair of upstream and downstream wavelengths, can be used to distinguish optical signals associated with users from each other. Using adjacent wavelengths adapted to the same filter template for each user advantageously allows the use of filter-based user multiplexing/demultiplexing components, where the same optical filter is used to process both the upstream and downstream channels associated with the user. In a BiDi transceiver, this filtering operation may be performed by a splitter (duplexer) adapted to isolate one direction from the other. The use of such splitter components in BiDi transceivers may present various technical problems: first, the isolation achieved by the separator is never perfect, and the lower the cost of the separator assembly, the poorer the isolation effect. In addition, the wavelength position may vary in a common system, which results in the wavelength no longer being centered in the filter.

However, the use of the same filter to process the upstream and downstream channels associated with each user in an optical distribution network also imposes the use of adjacent wavelengths for the upstream and downstream channels of each user, which creates several challenges, mainly due to the lack of isolation within the filtering template between the wavelengths of the upstream and downstream channels.

Technical problems encountered when considering bi-directional optical transceivers using adjacent wavelength optical transmission technology with line rates around 10Gbps include problems related to upstream and downstream filtering.

Filtering at line rates of 10Gbps may be based on components such as circulators and thin film filters. Due to imperfect filtering, the isolation between the two propagation beams (uplink and downlink channels) of each channel pair is also imperfect, i.e. the part of the transmitted signal (downlink channel) is mixed with the received signal (uplink channel). This results in a superposition of the transmitted signal on the intended received signal at the receiver, which introduces external light injection and introduces perturbations in the gain characteristics (time and frequency domain) of the transmitter stage.

Furthermore, both ends of the point-to-point link may not be perfectly tuned, especially if there are cost reduction requirements for the BiDi transceiver, which are addressed by reducing the performance of the tuning system and/or reducing the performance of the splitter/duplexer.

The technical problem to be solved also includes the problems related to the following phenomena of spreading the signal spectrum, which makes the filtering even more critical: the modulation used to transmit the data may spread the optical signal in the frequency domain as the bit rate increases while maintaining the same modulation format. In addition, propagating scattering along the transmission link (including the optical fiber) also spreads the optical signal in the frequency domain. In addition, diffusion and back reflection in the propagation can introduce additional signal interference.

The BiDi systems that have been demonstrated to date typically operate at 10 Gbps. However, some operators represent a need for bi-directional systems capable of providing transmission at line rates in excess of 10Gbps, for example at 25Gbps or even 50 Gbps. This is the case, for example, of the eCPRI specification published in 8 months in 2017, which describes a scenario of interest to the operator, where a transmission of 50Gbps is being considered. Thus, there is a need for a bidirectional DWDM transceiver that operates at rates in excess of 10 Gbps.

In addition to the above challenges associated with line rates of about 10Gbps, several additional problems/challenges must be addressed for rates in excess of 10 Gbps:

first, the costs associated with the components used in the filtering components should preferably be controlled, thereby creating significant cost constraints. Preferably, the cost of upstream and downstream isolation achievable with the BiDi technology operating at 10Gbps should be kept low. Maintaining the same filtering components or cost equivalents as those used for rates up to 10Gbps may provide a solution to this constraint.

For example, as described above, a transceiver device designed for DWDM technology used in a core network of a cellular network operating at about 10Gbps line rate and employing NRZ modulation should ideally be reused in an optical access network environment such as an ODN network to avoid the costs associated with designing and manufacturing or procurement of devices with better filtering performance.

Other challenges are related to the available options to increase line rates above 10 Gbps:

first, an increase in line rate using the same modulation format will result in an increase (substantially linear) in the associated baseband spectral range. In this regard, it is noteworthy that 10Gbps transmission rates using NRZ modulation already require 20GHz bandwidth.

Further, for transmission rates exceeding 10Gbps, it may be considered to use modulation more efficient than NRZ spectrum. For example, M-PAM modulation may be considered, the bandwidth of which is about half of the NRZ bandwidth for the same bit rate. However, each time M is doubled, the sensitivity may change by about 4dB compared to NRZ at the same bit rate (e.g., a 4dB sensitivity difference between NRZ and 4 PAM).

Regardless of the modulation scheme (NRZ or M-PAM), maintaining the filtering scheme as it is, the filtering performance of the uplink and downlink must be significantly improved, which is very expensive. When NRZ is used, the top of the filter must be enlarged while maintaining the effective band in the spectrum, i.e. the slope must also be increased. When 4PAM is used, the isolation must be increased, which also means a higher slope. In fact, 4PAM modulation can be used to achieve higher bit rates, to the extent that noise levels can be reduced, given its substantially constant spectral support in the frequency domain. This noise reduction is actually achieved by higher slope filters that are able to filter out noise lying on the frequency axis of the channel path.

Furthermore, the inventors of the present disclosure have devised that the transmitting side of the optical transceiver may suffer from frequency detuning damage occurring at the transmitting side of the light source when switching from a non-transmitting state to data transmission. This frequency detuning impairment may occur for any light source operating in burst mode for data transmission.

In fact, low cost lasers may have a sensitive side mode power contribution, as shown in fig. 2b, since the laser side modes may introduce crosstalk, but may also include frequency detuning impairments (hereinafter may be referred to as "frequency chirp"), typically with an amplitude of about 20GHz when operating in burst mode, as shown in fig. 2 c. Addressing such frequency chirps is critical to reducing power consumption, e.g., for packet transmission. Furthermore, accounting for frequency chirp allows the laser source to be turned off more frequently, helping to reduce the amount of aggregate power sent within the fiber, thereby reducing potential nonlinear propagation impairments.

Turning on the light source in a time interval of a few nanoseconds results in a frequency drift in detuned form which decreases after the initial peak within a few hundred microseconds, and turning on the light source in a time interval of a few hundred nanoseconds also results in a frequency drift in detuned form which also decreases after the initial peak within a few hundred microseconds, and turning on the light source in a time interval of a few microseconds also results in a frequency drift in detuned form which also decreases after the initial peak within a few hundred microseconds, as shown in fig. 2 c. Thus, fig. 2c shows that turning on the light source in a time interval of less than a few microseconds produces frequency detuning damage in the form of a peak detuning portion followed by a decay portion until the frequency detuning becomes negligible. The more significant the frequency detuning peak, the more severe the detuning is caused, because the light source is turned on fast. Therefore, for optical sources that perform data transmission at higher transmission rates (10Gbps and higher), for example using NRZ modulation, such frequency detuning can become an important issue. For bi-directional DWDM transceivers operating at higher transmission rates, this problem may become more severe because the multi-user time division multiplexing operation causes all users to stop transmitting, except for the users performing data transmission on a given time slot. Furthermore, certain modulations with larger spectral bandwidths, such as NRZ and RZ modulations, may even further exacerbate the problem as compared to other modulations (e.g., M-PAM modulations), as they may experience leakage in the frequency domain between user channels.

Fig. 3 shows an example of a BiDi transceiver device (50) receiving an optical signal S sent over an optical fiber (51), which optical fiber (51) is connected to an interface of a device, e.g. a coupler device (52). The coupler device (52) may be a WDM coupler, i.e. a coupler capable of combining and splitting data transmitted over the optical fiber (51) based on optical wavelengths for upstream and downstream.

The apparatus (50) comprises an optical transmitter (53) configured to transmit a signal T over an optical fibre (51) based on transmit data (Tx data) to be transmitted to one or more remote nodes. The transmission data is processed by an optical transmitter (53) to generate an optical signal T, which is supplied to an optical fiber (51) through a duplexer (54) and a coupler (52).

The apparatus (50) further comprises: an optical receiver (55) (e.g., an optical-receiver) including, for example, a photodiode, a transimpedance amplifier assembly, an analog circuit, and an analog-to-digital converter; and a digital processor configured to receive optical signals transmitted from one or more remote nodes over optical fibers (51) and received through a coupler (52) and a diplexer (54). The received optical signal is processed by an optical receiver (55) to generate reception data (Rx data).

The signal S transmitted from a remote source may be represented in the following phase-amplitude complex representation:wherein i represents a complex number whose square is equal to-1, ω_sRepresents the pulsation of the signal S, t represents time, anRepresenting the amplitude of the signal.

The signal T transmitted by the device (50) can likewise be represented by the following phase-amplitude complex representation:wherein i represents a complex number whose square is equal to-1, ω_tRepresents the pulsation of the signal T, T represents time, anRepresenting the amplitude of the signal.

An optical receiver (55) of the device (50) may receive a first received signal S corresponding to a signal S transmitted from a remote source_rAnd a second received signal t_b(also referred to as interference signal hereinafter) whose at least one component corresponds to a set of counter-propagations of the signal T transmitted by the device (50) itself. These counter-propagating are caused byDefects in the optical fiber (51) of the device (50) transmitting the signal and reflections in each connector, coupling or more generally in each optical device (52), except the optical fiber (51), the signal T transmitted by the device (50) encounters this counter-propagation on its signal path.

These back propagation prevent distinguishing between transmitted and received signals at the transceiver, especially when such transceivers are connected to several kilometers of optical fiber. As described above, an optical signal transmitted over a 40km length of optical fiber may experience an attenuation of about 0.15dB/km, i.e., 6dB for a 40km length of optical fiber. The signal attenuation also comes from the connector, possibly from any other component in the signal path, such as a power splitter component, in which case such losses are referred to as "insertion losses", and thus the attenuation experienced by the signal received at the receiver may be up to 18 dB. On the transmitter side, the signal power of the transmitted signal will be much higher (e.g. 15dB, 18dB or possibly 20dB) than the power of the received signal. Although the back reflections may also be strongly attenuated by the diplexer (about 20dB or 30dB), at least those reflected signal powers in the reflections that are generated by optical devices located near the transmitter transmitting the signal, such as coupler (52) in the case of transceiver (50) shown in fig. 3 close to transmitter (53), may have amplitudes close to about the amplitude of the signal received at the transmitter introducing significant interference to signal S. This creates significant interference to the received signal which degrades the performance of the transceiver as expressed in terms of bit error rate and may even be difficult to distinguish the received signal from the components of the transmitted signal generated by its back reflection.

First received signal s_rMay be represented as a signal received at a receiver (55) from a signal S transmitted over a propagation channel comprising a propagation in an optical fiber (51) connected to the device (50), which channel may be referred to hereinafter as a "forward channel".

Second received signal t_bCan be represented as a signal received at a receiver (55) as a result of a counter-propagation of a signal T transmitted by the device (50), which signal T can be represented by a counter-propagating channel, the signal T being represented by a signalThe channel may be referred to hereinafter indiscriminately as a "back channel" or "back propagation channel". In other words, the interference component (of the interfering signal) generated by the back propagation of the signal T transmitted by the transceiver (50) over a transmission link comprising an optical fiber (51) connected to the transceiver (50) can be expressed as the complex transfer function H of the signal T and the signal T representing the back channel_cpIs performed.

Assume a complex impulse response function H for the forward channel_p＝αe^iθThe frequency domain representation of the first received signal may be expressed as follows:

assuming a complex impulse response function for the reverse channelThe frequency domain representation of the second received signal may be represented as follows:

in the example shown in fig. 3, S corresponds to a signal transmitted by a source on the optical fiber (51) remote from the transceiver (50), and T corresponds to a signal transmitted on the optical fiber (51) by the transmitter (53) of the transceiver (50). H_pAnd H_cpRespectively, the propagation and counter-propagation channels associated with S and T.

Signal componentAndcan be viewed as the amplitude attenuation component, θ andmay be considered phase shift components, some or all of which are to be estimated in accordance with embodiments of the present disclosureAnd (6) counting and compensating. Although this is not represented in equations 1 and 2, one of ordinary skill in the art will appreciate that the signal componentAndare time-varying components (since they typically vary with a time constant of the order of magnitude of the symbol duration). Also, α and a are time-varying components (since they typically vary with a time constant of the order of magnitude of the duration of the channel).

More specifically, in equation 1, the term θ + ω_rt corresponds to the optical carrier. In an embodiment, ω_rMay represent a value corresponding to about 10¹⁴Wavelength of frequency in Hz.

In one or more embodiments, the interference to be handled includes interference with two carrier frequencies ω_rAnd ω_tAnd the variance between them, equations 1 and 2 are a convenient way to identify and estimate such variance, as shown in equation 4 below, from which it is derived.

Time varying componentAndand the time constant of the time variation of alpha and a can be considered to be significantly smaller than the time constant associated with the optical carrier and thus smaller than the time constant associated with the optical carrier consisting of two carrier frequencies omega_rAnd ω_tThe variation between them differs the time constant of the generated interference. Thus, in some embodiments, the time-varying component is in view of their time constant, as compared to the interference generated by the varying difference between the two carriersAndand alphaAnd the temporal variation of a can be neglected.

A receiver (55), e.g. a photodiode receiver, of the transceiver (50) receives the superimposed first reception signal s_rAnd a second received signal t_b. In embodiments where the receiver (55) is a photodiode receiver, the current i output from the photodiode may be estimated to be proportional to the received light intensity and may be expressed as follows:

where M is a known parameter related to the device used. Equation 3 can also be expressed as:

wherein z is^*Andrespectively, for specifying the complex conjugate of the complex number z.

Combining equations 1, 2, and 4 yields equation 5 below:

in the case of the measured current i, M is a known parameter related to the device used,is a known component (and possibly a phase component) of the transmitted signal) And alpha and a are determined by the propagation channel and the counter-propagation channel, respectively. As described above, by ω_rAnd ω_tThe interference generated by the difference in variation between appears explicitly in equation 4. Equation 4 also shows that this variation can be obtained by filteringEstimation of the quantization difference. In fact, even ifAndalso time-varying components, whose time constant varies significantly less than ω_rAnd ω_tAnd ω_rAnd ω_tThe difference between them.

In the case of the equation 5, the,corresponding to the signal to be estimated and in general possibly also to theta. In some embodiments, it may be assumed that the θ parameter does not carry any information to be determined at the receiver side (e.g., in the case where the transmit side does not encode any information in the phase of the transmitted signal). It may then be considered in some embodiments to beIs the only unknown signal that the receiver side may need to retrieve.

Under this assumption, equation 5 above can be considered as a · x²A quadratic equation of the type + b · x + c ═ 0, where x is an unknown variable, with the following parameters:

a＝1，

and isIs an unknown variable.

The discriminant Δ b of the quadratic equation²4ac can be considered a positive number or zero, since i corresponds to the sum of all contributions, and thereforeIt follows that equation 5 always has at least one real solution, which can beExpressed by equation 6:

wherein the content of the first and second substances,

equation 6 can be rewritten as equations 6' and 6 "as follows:

in some embodiments, the isolation may be considered small enough such that a may also be considered small enough to account forTaylor expansion of (a):

this results inThe following were used:

equation 7 can also be rewritten as equation 7':

in view ofIs a signal, toOnly the positive solution may be retained, which results in:

equation 8 can also be rewritten as equation 8':

wherein

Signals transmitted by remote sourcesCan be approximated as follows:

where a and a are parameters representing the amplitude attenuation introduced by propagation on the reverse channel and the forward channel, respectively, where θ andthe phase shifts introduced by the forward and reverse channels, respectively. In practice, the filter used to filter the interference may be chosen such thatThus item

As described above, in some embodiments, these parameters may be considered to be independent of time to the first order. Instead, their frequency dependence can be taken into account.

Equation 9 shows that the interference component introduced by a transceiver transmitting signal T over a transmission link comprising an optical fiber receiving signal S can be determined by characterizing the back channel, which represents the combination of contributing signals resulting from the respective back propagation of the transmitted signal T along its transmission path.

In one or more embodiments, the reverse channel may be characterized by determining an estimate of the attenuation coefficient, a, corresponding to the reverse channel. Then, in an embodiment, the signalMay involve the determination of an estimate of the attenuation coefficient alpha corresponding to the forward channel. Depending on the implementation of the receiver of the transceiver, the estimates of α and a may be obtained simultaneously or sequentially.

That is, an estimate of the attenuation coefficient α corresponding to the forward channel may already be available in some embodiments, e.g., from measurements performed at system deployment or during system configuration. In other embodiments, the estimate of the attenuation factor α may also be determined using the transmission of a known signal from a remote source while all other transmitters of the network (including the transmitter of the transceiver of interest) are muted, as will be described in more detail below.

In one or more embodiments, the reverse channel may also be determined by determining phase shift coefficients corresponding to the forward channel and the reverse channelIs characterized by the estimate of (c). As described above, with respect to the α and a components, θ andis a time-varying component having a time constant in the order of the time constant of the channel, i.e. the time constant is significantly smaller than ω_rAnd ω_tTime constant of, and ω_rAnd ω_tIn betweenAnd (4) poor.

That is, according to an embodiment, the determination of the interference component corresponding to the back propagation of the optical signal T transmitted by the transceiver may comprise a coefficient corresponding to the back channelDetermination of an estimate of, an estimate of an attenuation coefficient alpha corresponding to the forward channel, and/or phase shift coefficients corresponding to the forward channel and the reverse channelIs determined. In some embodiments, the determination of the attenuation coefficient α may be performed using standard estimation and equalization techniques applied to the desired signal S, assuming no interference.

Fig. 4a shows an exemplary embodiment of the proposed method for transmitting signals at a light source of an optical distribution network according to the present disclosure.

The proposed method may be implemented in any light source configured for transmitting data through an optical network. For example, in one or more embodiments, the proposed method may be implemented at the transmit side of a transceiver, such as the optical transmitter (53) of the transceiver shown in fig. 3.

In one or more embodiments, a light source implementing the proposed method may be configured for obtaining (80) characteristics of frequency detuning impairments of the light source occurring when switching from non-transmission to data transmission. For example, the light source may be configured such that a frequency chirp knowledge acquisition process may be performed to adjust data transmission at the light source based on the acquired frequency chirp knowledge. The transmission of data (81) at the light source may then be based on the characteristics of the frequency detuning impairments.

In one or more embodiments, the light source may be configured to determine a characteristic of the frequency chirp. In general, frequency chirp knowledge acquisition may be performed using a filter having a triangular shape in the frequency domain in combination with a photodiode configured to detect a signal. The filter may be configured to track amplitude variations over time to gain knowledge of the frequency chirp, for example with a filter configured with a center frequency corresponding to the frequency of interest and a slope for tracking signal attenuation (the dynamics of the frequency variation may then be derived from the dynamics of the amplitude variation). Depending on the implementation, the filter-photodiode set configured for frequency chirp knowledge acquisition may be included in the light source, or in any other node in the network.

In other embodiments, the acquisition of the characteristics of the frequency detuning corresponding to the frequency chirp may be performed using heterodyne interference techniques, such as those described herein with respect to frequency detuning knowledge acquisition. Such techniques may use multiple laser sources, one of which is the laser source of interest whose frequency chirp knowledge is to be acquired.

As shown in fig. 2d and discussed above with respect to fig. 2b and 2c, when operating data transmission in burst mode, the frequency chirp impairment experienced by the optical source typically comprises two consecutive portions: the initial part (called "non-adiabatic effect") is in a very short time frame (in the time interval from time 0 to a few nanoseconds (narampu)), followed by the second part (called "adiabatic evolution") which scales in more than a few hundred microseconds (ARampUp). The duration of the frequency detuning impairment comprises a first (narampu) duration and a second (ARampUp) duration that are consecutive.

In one or more embodiments, the light source may be configured to obtain data relating to a duration of the frequency-detuned damage as part of obtaining characteristics of the frequency-detuned damage.

In some implementations, the light source can be configured to determine data related to a duration of frequency detuning damage.

According to an embodiment, the determination of data relating to the duration of frequency detuning damage may be performed in a dynamic manner, e.g. dynamically adjusted as the data transmission rate of the light source operation changes.

According to an embodiment, the data relating to the duration of the frequency-detuned impairment may relate to an estimate of a partial duration of the frequency-detuned impairment or to an estimate of a total duration of the frequency-detuned impairment.

In some embodiments, the data relating to the duration of a portion of the frequency-detuned damage may represent an estimate of the duration of the above-described initial portion of the frequency-detuned damage (non-adiabatic effect). For example, obtaining characteristics of frequency detuning impairments of a light source that occur when switching from non-transmission to data transmission may include obtaining an estimate of a duration naramtap of the light source in some embodiments.

In some embodiments, the data relating to the duration of the part of the frequency-detuned damage may represent an estimate of the duration of the above-mentioned initial part of the frequency-detuned damage (non-adiabatic effect) and an estimate of the duration of the above-mentioned second part of the frequency-detuned damage (adiabatic evolution), such that an estimate of the total duration of the frequency-detuned damage may be obtained. For example, obtaining a characteristic of frequency detuning impairment of a light source that occurs when switching from non-transmission to data transmission may in some embodiments include obtaining an estimate of duration narampupp for the light source, obtaining an estimate of duration arampupp for the light source, based on which an estimate of total duration of frequency detuning impairment (narampupp + arampupp) may be obtained.

In other embodiments, an estimate of the total duration of frequency detuning damage may be determined directly.

The first embodiment: using ramp-up periods

Referring now to fig. 2e, in one or more embodiments, transmitting data based on characteristics of frequency detuned impairments may include transmitting data with a time shift based on a duration of frequency detuned impairments. The use of such a time shift advantageously allows avoiding the strongest effects of frequency detuning impairments. In some implementations, the light source may be configured to transmit the virtual signal during the time shift period. That is, the dummy signal may be transmitted during the time shift duration before the start of transmitting data. Alternatively, one may choose to send data during a time shift period for which the occurrence of frequency chirp impairments is considered acceptable.

In some embodiments, a framing may be defined that sets a period for ramping before any type of signaling or data is transmitted, and a light source implementing the proposed method may be configured to defer any transmission of signaling or data until after a predefined ramping period. The sending of the signal (ramp-up signal) may be turned on (e.g., for sending a dummy signal as described above) so that frequency detuning impairments may occur, and the light source may be configured to wait until the end of a ramp-up period, the ramp-up period beginning with turning on the sending of the ramp-up signal before sending data to be sent, and frequency chirp impairments considered undesirable thereto.

In some embodiments, the time shift (for transmitting data) may be based on a combination (e.g., sum) of the first duration (corresponding to an estimate of the duration of the non-adiabatic effect) and a portion of the second duration (corresponding to an estimate of the duration of the adiabatic evolution) where the frequency detuning is above a predetermined threshold (the Dth threshold on fig. 2 e). The threshold (Dth) may be considered to correspond to a duration in adiabatic evolution at the end of which the frequency detuning is substantially stable (no longer significantly changing) (ARampUp' as shown in figure 2 e).

As shown in fig. 2e, during the duration ArampUp _ J, n corresponding to adiabatic evolution at the light source J, the frequency detuning decreases to reach the Dth threshold (duration ArampUp'). The time shift may be configured with a duration corresponding to the sum of an estimate of the narampu duration (first duration) and an estimate of the ARampUp' duration (part of the second duration). After a time-shifted period (narampp + arampp' in the example shown in fig. 2e), the light source may send data during the duration Trans J, n, since the frequency chirp impairments may be considered no longer significant or undesirable.

Data transmission may stop at tltt (time of last transmission time), and the dashed curve shows the evolution of the resonance condition in the laser cavity after stopping transmission at the light source, translating into frequency. When a resume is sent, for example using the dummy signal discussed above, another non-adiabatic effect occurs at a higher value (Δ D) than the previous one, starting at the time corresponding to the activation of the light source. The second adiabatic effect generates a frequency detuned peak that is not as high as the previous peak, followed by a new adiabatic evolution (ARampUp _ J, n +1) during which the frequency chirp reaches the Dth threshold faster than before. The second adiabatic effect occurs at a value closer to the progressive value (Δ D) of the chirp associated with the steady state than the previous one, starting at a time corresponding to the activation of the light source. The next data transmission (Trans _ J, n +1) can then be performed earlier than the previous one (Trans _ J, n), as shown in FIG. 2 e.

In some embodiments, the Dth threshold may be a parameter for configuring the light sources for a duration of time shift that may be dynamically changed.

In some embodiments, to account for the different effects of memory effects in non-adiabatic cycling from one data transmission to the next, the time shift may also be determined based on an estimate of the duration between the end of the last data transmission and the next activation of the light source.

In such embodiments, the time shift may be shortened based on the estimated duration between the end of the last data transmission (initiated in a system without any memory effect of the previous activation (or with less memory effect)) and the next activation of the light source, as compared to a combination of narampu and ARampUp ' durations (the ARampUp ' is determined based on the Dth threshold) (e.g., the sum of narampu + ARampUp '). For example, in some embodiments, the duration of the ARampUp' used in the time shift may be shortened by an amount of time corresponding to the difference Δ ARampUp between the beginning of the adiabatic period and the duration from one data transmission (initiated in a system without any previously activated memory effects (or with less memory effects)) to the next data transmission reaching the detuning threshold Dth, since the amount of detuning maximum deviation will be reduced from one transmission initiated in a system without any previously activated memory effects (or with little memory effects) to the next (Δ D as shown in fig. 2 e).

This reduction in time shift can advantageously be used to account for previously activated memory effects that produce a difference in duration from the beginning of the adiabatic period to the detuning threshold Dth. Since such memory effects from one transmission to the next may have different effects (e.g., due to different durations of data transmissions), the time shift may shorten the amount of time that changes.

In some embodiments, the amount of time that the time shift is reduced can be calculated using the detuning value at ARampUp _ J, n given by a look-up table that gives the adiabatic detuning as a function of time, and the value of T-tltt given by another look-up table that gives the relaxed detuning as a function of time.

Second embodiment: estimation and compensation of detuning

In one or more embodiments, a light source implementing the proposed method may be configured to estimate frequency detuning impairment and to adjust its data transmission by compensating for the estimated frequency detuning impairment.

Such an implementation may be considered as an alternative to, or in combination with, using time shifting to defer data transmission as described above. They provide the advantage that time shifts can be avoided where the time period is considered too long, especially in view of the transmission rate at which data is to be transmitted. In practice, this may be a problem for critical delay (<100 μ s) applications, since the hundreds of microseconds reserved for the ramp-up period may generate a large overhead (100 μ s at 25Gbps means 2.5Mb of data transmission is lost), and may also cause delays. Thus, in some embodiments, the introduction of a ramp-up period in the framing of the light source may be avoided by estimating and compensating for the detuning introduced by the light source.

In some implementations, obtaining the characteristic of the frequency detuning impairment may include obtaining an estimate of the frequency detuning impairment, and the sending of the data may include processing the optical signal carrying the data to compensate for the frequency detuning impairment based on the estimate of the frequency detuning.

In some implementations, the frequency chirp damage may be estimated at the time of manufacture of the light source, and the light source may be configured with data representing the estimated frequency chirp damage to account for the characteristics of the obtained frequency detuned damage by compensating for the damage.

In some embodiments, frequency chirp damage may be estimated at the time of setup of the light source, and the light source may be configured at the time of setup with data representing the estimated frequency chirp damage to account for characteristics of the obtained frequency detuned damage by compensating for the damage.

In some implementations, the frequency chirp impairment may be regular for the light source, and the light source may be configured with updated data representing the estimated frequency chirp impairment to account for the characteristics of the obtained frequency detuned impairment by compensating for the impairment. Periodically determining an estimate of frequency chirp impairment provides the following advantages: frequency chirp damage that evolves over time can be more accurately estimated by periodic updates, for example as the light source ages.

The third embodiment: combination of the first embodiment and the second embodiment

In one or more embodiments, a combination of reserved ramp-up periods and estimating and compensating for frequency detuning impairments may be used, for example, by using a ramp-up period corresponding to the above-described initial portion of frequency detuning impairments (non-adiabatic effects) during which the detuning is more severe than during subsequent periods (adiabatic evolution), and then mitigating the detuning based on an estimation of such detuning as described above with respect to the second embodiment.

For example, in some embodiments, transmitting data based on characteristics of frequency detuning impairments may include: transmitting data with a time shift, wherein the time shift is based on a first duration of the frequency detuning impairment, obtaining characteristics of the frequency detuning impairment may comprise: obtaining an estimate of frequency detuning impairment during a second duration of frequency detuning impairment, and transmitting the data may further comprise: the data-bearing optical signal is processed to compensate for the frequency detuning impairment based on an estimate of the frequency detuning impairment.

Fig. 4b illustrates an exemplary embodiment of a method for receiving signals at an optical transceiver of an ODN network that may be used in addition to the proposed method on the transmit side of the optical transceiver in accordance with the present disclosure.

A receive side of a transceiver (e.g., an optical receiver (55) of the transceiver (50) shown in fig. 3) receives (60) a received optical (RxO) signal corresponding to a first transmitted optical signal (TxO) carrying data transmitted by an optical source (e.g., a laser source) over a first transmission link including an optical fiber.

As mentioned above, the received RxO signal includes an interfering signal, which itself is composed of one or more interfering components, one of which is introduced by the transmission performed by the transmitting side of the transceiver (e.g., the optical transmitter (53) of the transceiver (50) shown in fig. 3).

Then, an estimate of an interference component of an interference signal in the received optical signal, the interference signal being introduced by a transmission side of the optical transceiver (53) transmitting a second TxO signal on a second transmission link comprising an optical fiber, is determined (61).

The proposed scheme for receiving optical signals therefore takes into account the interference in the optical signals received at the receiving side of the transceiver, introduced by the optical signal transmission performed at the transceiver itself.

In one or more embodiments, determining the interference component may include characterizing a combination of contributing signals introduced from respective back-propagation of the transmitted second TxO signal.

Based on the determined interference component, the received RxO signal is processed (62) to obtain (63) an estimate of the first TxO signal, and such estimate is removed from the received RxO signal. Further details regarding this process in one or more embodiments are provided below.

Fig. 5 shows an optical distribution network 70 comprising a plurality of interconnected nodes, the optical distribution network comprising a transceiver device 71, one or more optical receiver devices 72a-72d, one or more optical transceiver devices 73a-73d, and an operations and management node 74 according to one or more embodiments of the present disclosure.

The operations and management node 74 is interconnected with the transceiver 71, the transceivers 73a-73d and the receivers 72a-72d through the ODN 70 so that it can exchange messages with the transceiver 71, the transceivers 73a-73d and the receivers 72a-72 d.

The transceiver 71 of interest is connected to the ODN 70 by a single optical fiber 71' over which it transmits and receives wavelength division multiplexed optical signals, for example according to the multiplexing scheme shown in fig. 2.

One of ordinary skill in the relevant art will appreciate that the network 70 shown in fig. 5 is merely an example illustrating an ODN in which embodiments of the present disclosure may be implemented. In particular, any suitable network topology or architecture (e.g., a tree topology or a mesh topology) may be used for network 70, with the architecture shown in fig. 5 being given by way of example only. Furthermore, any suitable architecture may be used for each of the network nodes 71, 72a-72d, 73a-73d and 74. For example, each of the receiver devices 72a-72d may be a stand-alone device or may be integrated within an optical transceiver.

An exemplary operational procedure for reverse channel acquisition applied to the network shown in fig. 5 is described as follows.

Depending on the implementation, the following operational procedures, or variations thereof, may be performed at the time the network 70 is established, during network updates, which may be performed on a preferably long-term, possibly periodic basis, and/or based on external requests (external requests being requests received from an operation and maintenance center of the network 70).

In one or more embodiments, the proposed procedure may use Optical Time Domain Reflectometry (OTDR) by sending OTDR signals in the network to carry measurements of parameters of interest.

In one or more embodiments, the operational procedure may be performed after a period of inactivity in the network, which may be selected to be no less than a predetermined period of time (T;)_otdrRefresh). According to an embodiment, the predefined period may be set to resolve a particular context. For example, in some embodiments, in the case of an operator-controlled network, the predefined period may correspond to a maintenance operation on the network, and may vary, for example, between hours to months. In some embodiments, the operational procedure may also be scheduled to account for the effects of aging of system components, in which case the predefined period may be set to several months. In some embodiments, the network node includes a component that is sensitive to temperature (e.g., includes a temperature change, such as a temperature change between daytime temperature and nighttime temperature, or a temperature change between sunlit and non-sunlit temperatures), and the network node includes a component that is sensitive to temperature (e.g., includes a temperature change between daytime temperature and nighttime temperature, or a temperature change between sunlit and non-sunlit temperature)The defined period may be set to about several milliseconds. In some embodiments, the predefined period may be set to a combination of some or all of the predefined periods of the particular environments described above.

For example, in a use case where one of the endpoints of the bidirectional point-to-point optical link is located at the top of the antenna mast, a temperature change (e.g., a temperature change between day and night or a temperature change during the time the cloud passes the endpoint) may affect the operation of the laser chip assembly of the BiDi transceiver such that the predefined period of time may be set to about 10 milliseconds.

In some implementations, the period of inactivity may be determined based on an estimate of a derivative of the temperature change over the period of time. In some embodiments, the predefined period of time may also be updated (including dynamically updated) to adapt the operation of the BiDi transceiver to changing conditions. For example, where the temperature around the BiDi transceiver varies over time, the predefined period may be updated from a few milliseconds to a longer duration (e.g., 1 hour). In some implementations, the predefined period of time can be dynamically adjusted, for example, based on a derivative of the temperature change around the BiDi transceiver.

Assuming that the execution of the program has been triggered, the management node (74) sends a pair to each transmitter (transceiver 73a-73d) of the network (70) from a predefined time t_mStart and last for a duration of time T_mOf OTDR silence. The relevant parameters may be transmitted to the destination node as the payload of the request message or may be pre-configured at the sender. According to an embodiment, a protocol such as the Optical Network Unit (ONU) management protocol OMCI (for ONU management and control interface) (specified by ITU-T as ITU-T g.988 recommendation) or the physical layer operation and maintenance (PLOAM) protocol (specified by ITU as GPON specification) may be used for the messaging described in the present disclosure. In some embodiments, a particular layer 2 channel (such as an ethernet channel) may also be used for messaging described in this disclosure.

In one or more embodiments, the management node (74) determines whether acknowledgement responses to the request have been received from all receivers of the network. A positive acknowledgement response by the receiver may typically carry an indication that it has been connectedThe requested information is received and may be serviced by the receiver. For example, a positive acknowledgement response may confirm that OTDR muting may be performed using relevant parameters, including a requested start time (tm) and a requested duration (T)_m). Depending on the implementation, the confirmation response may be explicit or implicit.

In one or more embodiments, a respective request start time parameter (tmi) value may be determined for each transceiver other than the transceiver of interest based on the request start time (tm) of the transceiver of interest, such that the transceiver of interest does not receive any signal other than an OTDR signal on its receiver side until time tm. For example, the tmi parameter for transceiver i (but not the transceiver of interest) may be determined based on the respective distance between transceiver i and the transceiver of interest. For example, the OTDR procedure may be configured such that each transceiver i except the transceiver of interest stops transmitting at tmi tm-Li/n/c, where Li denotes the distance between the transceiver of interest and transceiver i (except the transceiver of interest), n is the optical index of the optical link between the transceiver of interest and transceiver i, and c is the speed of light in vacuum. In some embodiments, OTDR management may be based on the tm parameter and the respective distances Li between the transceiver of interest and the transceivers i (other than the transceiver of interest), determined, for example, using: tni-tm-Li/nxc determines tmi parameters and transfers the determined tmi parameters to transceiver i for use in the OTDR procedure described herein.

In one or more embodiments, a respective requested duration parameter (Tmi) value may be determined for each transceiver other than the transceiver of interest based on a requested duration (Tm) of the transceiver of interest, such that the transceiver of interest does not receive any signal other than OTDR signals at the receiver side during the duration Tm. For example, the Tmi parameter for transceiver i (other than the transceiver of interest) may be determined based on the respective distance between transceiver i and the transceiver of interest, or, according to an embodiment, based on the start time Tmi parameter determined for transceiver i. In some embodiments, OTDR management may determine a Tmi parameter based on the Tm parameter and transmit the determined Tmi parameter to transceiver i for use in the OTDR procedure described herein.

The receiver's negative acknowledgement response may typically carry information indicating that the request has been received, but cannot be served by the receiver. A negative acknowledgement response may also be considered received in the event that no acknowledgement response (whether positive or negative) is received from the receiver after a predetermined period from the start of the transmission of the request.

In one or more embodiments, in the event that the management node determines that one or more negative acknowledgement responses have been received, a new request for OTDR muting may be sent to each of the receivers (72a, 72b, 72c, 72d) of the network (70) with the same parameters or different parameters. For example, a new start time Tm 'and/or a new duration Tm' may be suggested to the receiver of the network.

In one or more embodiments, the duration T of the OTDR silence request_mMay be based on a frame period T_otdrAnd the length of the OTDR pattern signal at a given wavelength (point). The frame period may be determined to be T, for example_otdr＝L_maxN × c, wherein L_maxIs the maximum length of the optical link (typically an optical fibre) connected to the transceiver (71) under test, n is the optical index of the optical link, c is the speed of light in vacuum, and therefore the duration T_mCan be determined as

T_m＝L_maxDuration of/nxc + OTDR mode

Wherein the duration of the OTDR mode is the duration of the OTDR mode. In other embodiments, the frame period may be determined as T_otdr＝k×L_maxN x c, wherein L_maxIs the maximum length of the optical link connected to the transceiver (71) under test, n is the optical index of the optical link, c is the speed of light in vacuum, k is a guard period parameter (k ≧ 1) such that the duration T is_mCan be determined as

T_m＝k×L_maxThe duration of the/nxc + OTDR mode,

wherein the duration of the OTDR mode is the duration of the OTDR modeAnd (7) continuing for a while. In other words, nxc is the speed of light in the optical link. T is_mMay preferably be selected to be greater than or equal to T_otdrSo that it can be within a sufficient amount of time (i.e., at least equal to T)_otdrDuring the time frame) the reverse channel is probed.

The transmitter of the transceiver (71) then transmits, starting from time tm, an OTDR mode signal, i.e. an optical signal carrying a known mode (OTDR mode), at a wavelength point that may correspond to any operation envisioned for the transceiver (71). For example, in case the transceiver (71) is used according to the multiplexing scheme shown in fig. 2, the transceiver (71) will repeat the transmission of the OTDR mode signal for each of the four transmission operating wavelengths shown in fig. 2. The above-described initial phase for obtaining transmission silence at all transmitters of the network may be repeated for transmission at each of these operating wavelengths.

In some embodiments, the initial phase described above may be performed at system setup, so that all operating wavelengths to be tested for channel estimation may be tested at once during system setup. Although the preliminary phase performed at setup may take a long time to complete, it has the advantage that once the system is running, a complete scan of the operating wavelength can be made without using any system resources.

In other embodiments, the preliminary phase described above may be performed during system operation. For example, the system may be configured to automatically learn as wavelengths are used. The system performs such tests each time a wavelength is to be used at which a preliminary stage test is not performed, and stores the results in memory so that the test need not be performed again. Although this strategy of performing the preliminary phase uses system resources once the system is running (during system operation), it advantageously avoids the lengthy preliminary phase at system setup, thus simplifying the preliminary phase. This strategy also takes advantage of the fact that the likelihood of using all system resources during the first phase of system operation is quite low in practice.

Depending on the implementation, the selected wavelength point may be any parameter that is explicitly or implicitly related to a given operating wavelength. For example, for a laser light source, it may be the temperature value of the source chip.

In one or more embodiments, the OTDR pattern may comprise a "1", followed by consecutive zeros, thus corresponding to Dirac (Dirac) pulses, to measure the impulse response of the reverse channel.

In one or more embodiments, the OTDR pattern may be a pattern consisting of pilots generated in an analog or digital manner.

The receiver of the transceiver (71) of interest obtains T in memory_odtrA received signal over the time frame, the received signal corresponding to a counter-propagation of the transmitted OTDR mode signal. In embodiments where the transmitted OTDR pattern corresponds to an impulse, the received signal acquired at the receiver of the transceiver (71) corresponds to the impulse response of the reverse channel. In some embodiments, the OTDR pattern may correspond to a plurality of frequency peaks, which may cover a spectrum corresponding to the spectrum of a signal transmitted by a remote source to the transceiver of interest, in order to obtain a transfer function at the receiver of the transceiver of interest, based on which the impulse response of the reverse channel may be determined. For example, in some embodiments, the transfer function (and thus the impulse response implicitly) may be retrieved by performing a Fast Fourier Transform (FFT) on OTDRFFTWindow/Ts samples, where Ts is the sample duration and otdrfwindow is the FFT window width (each parameter is predetermined or dynamically determined, depending on the embodiment), in order to obtain an estimate of the amplitude and phase response of the reverse channel.

In some embodiments, the transmitted OTDR pattern may comprise a sequence of 0 bits and 1 bits, which are selected to have certain arithmetic characteristics, so that synchronization may be achieved using the transmitted OTDR pattern. The impulse response of the channel may then be obtained from the received signal using an inverse convolution with the known transmitted OTDR pattern. The binary sequence is also advantageous in that it avoids the risk of noise when sending a single bit and is easier to synchronize than sending on a single bit basis.

In one or more embodiments, the above-described signal acquisition may be repeated and then averaged to achieve a predetermined signal-to-noise (S/N) ratio for signal acquisition. In some embodiments, a significant interference may be deemed not to be present if a predetermined S/N ratio is not reached after a predetermined number of averaged consecutive signal acquisitions.

The signal acquisition described above may result in a large number of bits being stored in memory. Depending on the implementation, these bits may be stored in a local memory of the transceiver and processed at the transceiver or sent to a remote processing node for further processing, as described below with reference to fig. 9. For example, for a given acquisition time frame T_odtrAnd given symbol duration T_sFetching in memoryAnd (4) sampling. Assuming that number of bits per symbol is given, BitsPerSymbol, storesThe required storage space may be up to 20 Mbits: in fact, for a 40km long fiber, T_odtrMay be chosen to be equal to 400 mus, the acquisition rate may be equal to 10Gbps, and for 4Mbits at 25GHz rate, 10Mbits should be stored for further processing, if oversampled with an oversampling factor equal to 2, they become 20 Mbits.

To avoid memory overflow at the transceiver, in some embodiments, the transceiver may comprise an OTDR management module configured to perform thresholding of the length of the acquired sequence by retaining only the start time of a valid sequence (significant sequence) and the bits of such a valid sequence. In some embodiments, when it is determined that the sequence includes more than a predetermined threshold Th_OTDRCan be determined to be valid for a predetermined number of consecutive samples. Accordingly, a threshold analysis may be performed based on the acquired data to determine that inclusion is above Th_OTDRA sequence of consecutive samples of the threshold. In some embodiments, there are no valid values for the data sequence (i.e., no values above Th_OTDRSamples of the threshold) may be lost as part of the threshold analysisAnd abandon to save storage space.

The OTDR data resulting from the OTDR processing may then be sent from the transceiver (71) to the management node (74). In one or more embodiments, upon completion of data acquisition and processing (possibly including thresholding analysis), the transceiver (71) may send an OTDR information message (e.g., using OMCI, PLOAM, or ethernet protocol) including wavelength points for OTDR transmission, along with the acquired data, at the transmitter side of the transceiver (71) and at the receiver side of the transceiver (71) to the management node (74). Where thresholding analysis is performed, the acquired data sent to the management node (74) may include the sequence resulting from the thresholding analysis, as well as the start time of such sequence.

The OTDR information received at the management node (74) may be stored in one or more look-up tables, referred to herein as back channel (BCh) tables, in which wavelength points on the transmitter side of the transceiver (71) and the receiver side of the transceiver (71) may be stored in association with corresponding acquisition data, possibly in the form of corresponding samples of a start time and an acquisition sequence corresponding to the wavelength points.

Fig. 6 illustrates the reverse channel knowledge process described above in one or more embodiments.

Fig. 6 shows a transceiver of interest (100), an operation and management node (101) and one or more transceivers (102) that may transmit data to the transceiver of interest (100) according to an embodiment of the present disclosure. The operations and management node (101), the transceiver of interest (100) and the one or more transceivers (102) are communicatively coupled, for example, by an optical distribution network such as that shown in fig. 5.

The transceiver (100) may include a transmitter (110), a receiver (111), and a wavelength splitter (112), which may be substantially similar to that shown in fig. 3 in some embodiments.

The transceiver (100) may be configured with a wavelength control engine (100a), a framing engine (100b), and an acquisition and thresholding engine (100 c). The wavelength control engine (100a) may be configured to operate at the transmitter (110) and the wavelength splitter (112). The framing engine (100b) may be configured to control and manage time parameters for transmitting and/or receiving data, and in some embodiments may be implemented as a state machine that organizes a temporal distribution of state changes to configure a temporal sequence of transmitted and/or received data. The acquisition and thresholding engine (100c) may be configured to operate at the receiver (111), i.e. to operate on data and/or signals received by the receiver (111).

The acquisition and thresholding engine (100c) may be configured to perform data acquisition operations on the acquired data and thresholding analysis, as described above with respect to the proposed back channel knowledge acquisition process.

The transceiver (100) may further comprise: a clock engine (100d) configured to time manage operations (including data processing operations) performed at the transceiver (100); and an OTDR management engine (100e) configured to control reverse channel knowledge acquisition operations at the transmitter (110) and receiver (111) of the transceiver (100).

Each of the other transceivers (102) may include: a framing engine (102 b); a clock engine (102d) configured to time manage operations (including data processing operations) performed at the transceiver (102); and an OTDR management engine (102e) configured to control reverse channel knowledge acquisition operations at the transceiver (102).

As shown in fig. 6, starting from a predefined time Tm and having a duration Tm (as indicated by the OTDR _ Message (Tm, Tm) Message of fig. 6), the management node (101) may be configured to send a request for an OTDR procedure to the transceiver (100) of interest. In response, starting from time Tm and lasting Tm, the management node (101) may receive an acknowledgement Message (as indicated by the OTDR _ Message _ Ack (Tm, Tm) Message of fig. 6) from the interested transceiver (100), acknowledging that the OTDR procedure may be performed.

The management node (101) may be further configured to send a request for OTDR silence to each (102) of the one or more transceivers (i), starting at the determined time Tmi and lasting for the determined duration Tmi (as shown in the Slient _ Message (Tmi, Tmi) Message of fig. 6). In response, the management node (101) may receive, starting from time Tm and for a duration Tm from each of the one or more transceivers (102), a respective acknowledgement Message (as shown in the exemplary silence _ Message _ Ack (Tmi, Tmi) Message of fig. 6), acknowledging that the OTDR procedure may be performed in the network at the transceiver of interest.

In some cases, the OTDR procedure may time out if a positive acknowledgement of OTDR silence with a given start and duration parameter cannot be obtained from all receivers to which a request for OTDR silence has been sent.

An OTDR management engine (100e) of the transceiver may be configured to then control the transmission of OTDR patterns by the transmitter (110) during periods of OTDR silence.

The transceiver's OTDR management engine (100e) may also be configured to control the acquisition and thresholding engine (100c) to perform data processing including data acquisition and to threshold the acquired data according to an embodiment.

In some embodiments, the data processing for reverse channel knowledge acquisition performed on data received at the receiver (111) of the transceiver (100) results in the generation of one or more look-up tables (LUTs) or Bch look-up tables, referred to herein as reverse channel look-up tables, which may be stored in the memory of the management node (101), further sending the data acquisition results and possible thresholding process results to the management node (101) (illustrated by the OTDR _ Information _ Message of fig. 6). In an exemplary OTDR Information Message, the start time sequence parameter may indicate the time at which OTDR signals are to be transmitted, the sequence parameter may indicate the OTDR sequence or signals to be used, and the wavelength point parameter may provide wavelength-related Information for use by the transmitter of the transceiver of interest during the OTDR procedure.

As described above, the interference component included in the interference signal present in the optical signal received by the receiver of the optical transceiver may be regarded as a change in time of the difference between the two frequencies, which may be expressed as Δ ω ═ ω in the above equation 9_s-ω_tA variant of (1).

In one or more embodiments, the estimate of the interference component may be determined by a detuning measurement procedure in order to determine an estimate of the position of the wavelength of the two interfering signals (the first transmitted optical signal transmitted by the remote source and the second transmitted optical signal transmitted by the transceiver) relative to each other. Once the respective positions of the wavelengths of the two interfering signals are determined, the interference components due to variations in the distance between these respective positions can be determined and corrected.

An exemplary operational procedure for acquisition by predicting chirp impairment for application to the network shown in fig. 6 is also provided as follows:

the management node (101) may set a framing sequence for transmission between the transceiver (i) (102) and the transceiver (j) (100) of interest during the period tramp _ i and determine a time instant t _ start for the start of synchronization of the chirp acquisition process.

The transceiver (j) may be configured to keep the transmitted signal silent during t _ start and t _ start + tramp _ i when performing the chirp acquisition procedure.

The transmitter side of the transceiver (i) may be configured to transmit a continuous wave at a given wavelength point starting at time t _ start when a chirp acquisition procedure is performed.

The receiver side of transceiver (j) may be configured to use a detuning measurement procedure to obtain characteristics of chirp impairment detuning within a period corresponding to an estimate of the duration of the chirp when performing the chirp acquisition procedure (as described above-e.g. NARampUp + aramppp), e.g. using a filter with a triangular shape or as described in connection with fig. 7, possibly with a suitable number of samples corresponding to the estimated duration of the chirp.

The results of the detuning acquisition method are stored together with Tx _ i wavelength point, WS wavelength point and Rxs _ j wavelength point, which respectively correspond to information about the wavelength used at the transmitter of the transceiver of interest (Tx _ i), information about the wavelength used at the wavelength separator of the transceiver of interest (WS _ i) and information about the wavelength used at the transmitters of other transceivers (j) in the network that can transmit data to the transceiver of interest (Rxs _ j).

The above operations may be repeated to partially or fully cover the expected range of wavelength points over which the nodes of the system may operate, the delay between two successive transmissions of transceiver (j).

In some embodiments, the detuning measurement processes and methods described herein for performing compensation (particularly with respect to the embodiments shown in fig. 7 and 8) may be used in transceivers of interest to estimate and compensate for frequency detuning impairments, including chirp detuning impairments generated by the transmit side of the transceiver.

In some embodiments, the detuning measurement process may also be performed on an optical distribution network (e.g., the network shown in fig. 5) that includes the BiDi transceiver.

The detuning measurement procedure is advantageously used in optical networks, in particular in networks where the network operator wants to relax constraints on the tuning system (e.g. relaxing constraints related to component tolerances, or increasing update periods to reduce signalling overhead), or in case a Directly Modulated Laser (DML) source is used.

The detuning measurement process may typically be performed periodically in order to estimate the detuning or to predict the detuning.

In some embodiments, the knowledge of instantaneous global detuning may be obtained based on self-heterodyne techniques. However, unless a proprietary system and process is established, a known determination of detuning based on measuring the signal level at the output of the heterodyne mixing and low-pass filters within the detuning range to be estimated cannot be used, since the presence of other filtering elements may be unknown or time-varying may alter the detuning measurement.

In accordance with the present disclosure, a direct measure of the beat introduced by the detuning to retrieve the value of the detuned cosine function is preferred because the system can sample the signal essentially as fast as the bandwidth of interest (e.g., about tens of giga-samples per second (GSps) samples_t) The function performs a cross-correlation or obtains a detuned cosine function using a Fast Fourier Transform (FFT) and a search of an existing peak over a set of FFT coefficients over a predetermined number (FmDetufting/Ts) of samplesNumerical values.

In one or more embodiments, the detuning measurement procedure proposed according to the present disclosure may use one or more of the following parameters:

for the wavelength point parameters, Tx wavelength point, WS wavelength point and Rxs wavelength point parameters may be defined, which correspond to information related to the wavelength used at the transmitter of the transceiver of interest, information related to the wavelength used at the wavelength splitter of the transceiver of interest, and information related to the wavelength used at the transmitters of other transceivers in the network that may transmit data to the transceiver of interest, respectively.

Transmitter-side and receiver-side guard time parameters (Tx _ ramp _ GT and Rxs _ ramp _ GT) may also be defined to account for the ramping up of the laser of the transmitter of the transceivers of the network (especially in the case of recent on/off).

A transmitter-side detuning frame (frxsmdeturning) having a length of TFRxsmDetuning bits may be defined with a predetermined pattern (smdeturning pattern) with respect to transmitters of transceivers (other than the transceiver of interest) in a network that may transmit data to the transceiver of interest.

A transceiver transmitter side frame (ftxm failure) of length (ttxm failure bits) may also be defined with respect to the transmitter of the transceiver of interest.

Transceiver receiver side frames (frxm decision) of the same length (ttxm decision bits) may also be defined with respect to the receiver of the transceiver of interest.

According to the proposed detuning measurement method, and referring back to fig. 5, a message is sent (e.g. by a management node (74)) to each transceiver of the network that can send data to the transceiver of interest, requesting a smdutting mode that starts at a time corresponding to the reception instant at which the predefined time tm can be added, and continues for tfrxsmdetuing. According to embodiments, the predefined time (tm) information may be included in the message, included in the signaling channel, or implicitly defined using default values.

A transceiver transmitter side frame (ftxmdeturning) may start at time tm + RTT/2, where RTT corresponds to an estimated round trip time for a transmitted message, which lasts frxmdeturning.

The transceiver receive side frame (FRxmDetufing) activation may begin at time tm + RTT/2, which lasts for TTxmDetufing.

The signal received at the transceiver (71) may then be acquired during FRxmDetuning.

In addition to signal acquisition at the transceiver (71), the acquired signals may be provided to a signal processing unit for filter analysis. Depending on the embodiment, the signal processing unit may be implemented at the transceiver or in a remote processing node, as described below with reference to fig. 9.

As described above, the filter analysis will provide a differential phase shift (dps (in equation 9)) Including the phase itself and its origin modulo 2 pi within the time symbol). This estimate may be stored in memory with the set of wavelength points and the differential phase shift reference dpsr. In fact, based on the knowledge of the wavelength point at the transmitter of the transceiver, the wavelength point at the receiver of the transceiver can be obtained without any explicit messages from the receiver or other transceivers of the network. In a reverse channel (BCh) look-up table, the wavelength point state of the receiver of the transceiver can be obtained using interpolation of previous measurements. As discussed below, then tt may also be expected for a period before the next detuning measurement.

In one or more embodiments, the detuning measurement process may be periodically triggered using a detuning measurement period, which may be predetermined or dynamically updated according to the latest state of the transceiver, the dynamics of the detuning, and/or by expectation.

In embodiments where the detuning measurement period is dynamically updated according to the dynamics of the detuning, the detuning measurement process may start, for example, with a fine time granularity measurement period to obtain, define a tuning fractional Threshold by linear or non-linear interpolation of previous measurements to set the following period. In other words, the detuning measurement process may be configured such that if the measured detuning shows little or no change over time, it may be estimated based on an interpolation of previous measurements rather than the actual updated measurements.

In embodiments where the detuning measurement period is dynamically updated by anticipation, a set of varying periods may also be defined, for example where one of the transceivers of the network that may transmit data to the transceiver of interest or the transmitter of the transceiver of interest has previously been turned off.

In some embodiments, the Round Trip Time (RTT) of a sent message may be measured by known ranging procedures.

Fig. 7 illustrates the detuning measurement process described above in one or more embodiments.

Fig. 7 shows a transceiver (100) of interest, an operation and management node (101) and one or more transceivers (102) that can transmit data to the transceiver (100) of interest, according to an embodiment of the disclosure. Such as communicatively coupled via an optical distribution network, such as the optical distribution network shown in fig. 5.

As described with reference to fig. 6, transceiver (100) may include a transmitter (110), a receiver (111), and a wavelength splitter (112), which may be substantially similar to that shown in fig. 3 in some embodiments.

The transceiver (100) may be configured with a wavelength control engine (100a), a framing engine (100b), and an acquisition and filtering engine (100 g). The wavelength control engine (100a) may be configured to operate at the transmitter (110) and the wavelength splitter (112). The framing engine (100b) may be configured to control and manage time parameters for transmission and/or reception of data, and in some embodiments may be implemented as a state machine that organizes a temporal distribution of state changes in order to configure a temporal sequence of transmitting and/or receiving data. The acquisition and filtering engine (100g) may be configured to operate at the receiver (111), i.e. to operate on data and/or signals received by the receiver (111). In some embodiments, the time parameters may be shared and managed over the network through a ranging procedure or a dedicated synchronization protocol.

The acquisition and filtering engine (100g) may be configured to perform data acquisition operations and filter analysis of the acquired data, as described above with respect to the proposed detuning measurement procedure.

The transceiver (100) may further comprise: a clock engine (100d) configured to time manage operations (including data processing operations) performed at the transceiver (100); and a detuning management engine (100f) configured to control a detuning measurement operation at the transceiver (100) of interest.

Each of the other transceivers (102) may include: a framing engine (102 b); a clock engine (102d) configured to time manage operations (including data processing operations) performed at the transceiver (102); and a detuning management engine (102f) configured to control a detuning measurement operation at the transceiver (102).

As shown in fig. 7, the management node (101) may be configured to send a detuning measurement request to the transceiver of interest (100) starting from a predefined time tm and lasting for a time window of duration tfrxmdutuing, as shown by the mdeturning _ Message (tm, tfrxmdeturning) Message of fig. 7. In response, the management node (101) may receive an acknowledgement Message (shown as an mdeturning _ Message _ Ack Message in fig. 7) from the transceiver (100) of interest, acknowledging that the detuning measurement may be performed using the parameters requested by the management node (101).

The management node (101) may also be configured to send a request for detuning measurements to each of the one or more transceivers (102) starting at time tm and lasting for a time window of duration tfrxmdutuing, as shown in the mdeturning _ Message (tm, tfrxmdeturning) Message of fig. 7. In response, the management node (101) may receive an acknowledgement Message (as shown in the mdeturning _ Message _ Ack Message of fig. 7) from each of the one or more transceivers (102), acknowledging that the detuning measurement may be made with the parameters requested by the management node (101).

The detuning management engine (100f) of the transceiver may be configured to then control the detuning measurements to an extent performed at the transmitter (110) and receiver (111) of the transceiver (100).

In particular, the detuning management engine (100f) of the transceiver may be configured to control the acquisition and filtering engine (100g) to perform data processing including data acquisition and filter analysis of the acquired data, as described above with respect to the proposed detuning measurement procedure.

In some embodiments, data processing for detuning measurements performed on data received at the receiver (111) of the transceiver (100) may result in the generation of one or more look-up tables (LUTs) or mdetuting look-up tables, referred to herein as detuning look-up tables, which may be stored in a memory of the management node (101), further sending data acquisition and filtering results to the management node (101) (illustrated by DDTS _ Information _ Message (w, dps, wavetength points) of fig. 7). In the exemplary DDTS _ Information _ Message (w, dps, wavelength points) detune differential phase shift (DDTS) Message of FIG. 7, the w parameter may represent the measured detuning (expressed as ω in equation 9)_s-ω_t) The parameter dps may represent the corresponding differential phase shift (expressed as equation 9)) The parameter wavelength point may provide information about the wavelength used by the transmitter of the transceiver of interest (wptx), the transmitters of other transceivers of the network (wprx) and/or the wavelength separator during the detuning measurement.

In the following, the proposed method of using the above described detuning and filtering procedure to perform compensation of impairments caused by transmission at the transmitting side of the optical transceiver is described.

The proposed method advantageously makes use of the following points:

at a given sampling time of the transceiver, the field on the photodiode is a combination of the field from the transmitter of the network, rather than the transceiver of interest, and a delayed version of the signal from the transmitter of the transceiver of interest (which may be characterized as being derived from the back channel).

Since detuning can vary in a sensitive manner within a few microseconds, and RTT is on the order of hundreds of microseconds, the continuous contribution to the signal received at the receiver resulting from the back channel may have varying wavelengths, thus covering multiple wavelength points. Therefore, it may be advantageous to reconstruct a series of wavelength points over time. In some embodiments, a vector of wavelength points at the transmitter is included in the BCh lookup table for this purpose.

Furthermore, the coefficients a and α may also depend on the wavelength point. In some embodiments, the wavelength point of Rxs at the sampling instant is estimated to retrieve the signal according to equation 9 above.

In one or more embodiments, the impairment caused by the above-described interference component can be compensated in the received light signal estimation process.

In some embodiments, the compensation process may include the multiplication of the phase term with the transformed transmitted signal transmitted by the transceiver, for example, to compensate for the distortion introduced by the wavelength splitter used by the transceiver of interest on the signal transmitted by the transmitter of the transceiver of interest, which distortion may affect the signal received by the receiver of the transceiver of interest, which may be corrected for by use in the proposed compensation scheme.

In other embodiments, for example, where the wavelength separator used in the transceiver of interest does not introduce a phase change to the signal received by the receiver of the transceiver of interest (or introduces such a phase change at an insignificant level, e.g., it is still below a predefined threshold), the proposed compensation scheme may be configured to ignore the distortion introduced by the wavelength separator. For example, the signal transmitted by the transceiver may not be multiplied by the phase term in order to not compensate for the phase distortion introduced by the wavelength separator that is considered insignificant. This may be advantageously used in cases where the filter of the wavelength separator has been designed not to introduce any significant phase distortion.

In some embodiments, the compensation scheme may be configured to correct for interference introduced by the wavelength separator based on a value of a wavelength point of a transmitter of the transceiver of interest relative to a value of a center frequency of a filter used to separate wavelengths in the wavelength separator. Since the interference generated by the wavelength separator may depend on the wavelength point used by the transmitter, the compensation scheme may be configured to compensate for such interference only for wavelength points for which the interference is considered and insignificant (e.g. exceeding a predefined threshold).

Thus, according to embodiments, the proposed compensation scheme advantageously allows to compensate only amplitude distortions from the back reflections, or to compensate amplitude distortions from the back reflections and phase distortions from the back reflections, or to dynamically configure the compensation (amplitude only, or phase and amplitude) depending on the wavelength used by the transmitter of the transceiver.

In some embodiments, for example using the above-described generation of the BCh look-up table, the coefficients for the compensation scheme may be selected in the back channel (BCh) look-up table in dependence on the wavelength point used by the transmitter of the transceiver of interest (wptx), used by transmitters of other transceivers (wprx) of the network and/or used by the wavelength separator during the detuning measurement. The transformed (i.e., compensated) signal may be the product of coefficients describing the reverse channel and a window that is slid by 1 at each clock instant and contains the transmit symbols transmitted by the transmitter of the transceiver.

Fig. 8 illustrates a method for performing compensation as set forth in one or more embodiments.

Fig. 8 shows a number of input vectors used in the proposed process, and they may have been generated according to the reverse channel acquisition process or detuning measurement process described herein (as the case may be).

Such input vectors may be stored in memory in the form of look-up tables as described above, and may be combined to generate output vectors according to the processes set forth in one or more embodiments.

The left hand side of fig. 8 shows a vector with time values (hereinafter referred to as "time vector") from which a first time value t-Bch _ sized is derived_TxCrossing to the last time value t + Proc _ sizeT_Tx-1, wherein T_TxIs a temporal sampling step size, Bch _ size corresponds to the temporal depth of the acquired reverse channel, and Proc _ size is a process size parameter. Thus, the size of the time vector is T_Tx(Proc _ size + Bch _ size). The time vector can be divided intoA set of values and a second set of values, the first set of values corresponding to the past and including a representation from t-Bch _ sizeT_TxHaving a time step T to the current time T_TxTime series of values (T, T-T)_Tx，...，t-k.T_Tx,., and t-Bch-sizeT_Tx) The second set of values corresponds to the future and includes the representation from T + T_TxTo t + Proc _ sizeT_Tx-1 have the same time sample step T_TxTime series of values of (a). I.e. the step size T of time samples from one to the next_TxMay be represented as t-k.T_Tx}_{k＝0，...，Bch_size}And the same time sample step T from one interval to the next_TxMay be represented as t + l.T_Tx}_{l＝1，...，Proc_size}. The exemplary temporal vector shown in fig. 8 thus spans the past with a depth equal to the Bch _ size and the future with a depth equal to the Proc _ size. In the embodiment shown in fig. 8, future time values are used which allow prediction of what will be sent in the future.

According to an embodiment, the processing may be performed on the acquired data corresponding to a time window spanning only past values having a first predetermined depth, or the acquired data corresponding to a time window spanning future values and past values having a second predetermined depth.

The next vector (immediately to the right in fig. 9) holds the values corresponding to the bit or binary symbol sequence transmitted by the transceiver at the time corresponding to the value of the time vector adjacent to the value corresponding to the transmitted bit (hereinafter referred to as "transmitted signal vector"), and at the current time t, the bit value is transmittedAt time T-T_TxSending bit values…, at time t-k.T_TxSending bit values…, and at time t-BCH _ size.T_TxSending bit valuesThe value of the transmitted signal vector corresponding to the future time value represents bits expected to be transmitted in the future. For example, the transmitter of the transceiver may be about to be at time T + T_TxTransmitted bits or symbolsStored in memory. In some embodiments, this advantageously allows for the processing of expected bits or symbols as long as such bits or symbols are stored in memory for future transmission, rather than waiting for the bits or symbols to actually be transmitted to at least participate in the respective processing set forth in this disclosure.

The next vector (immediately to the right of the transmitted signal vector in fig. 9) holds the value corresponding to the wavelength point at the transmitter of the transceiver at the time corresponding to the value of the time vector adjacent to the value corresponding to the transmitted bit (hereinafter referred to as "transmitted wavelength vector"): at t, the bit valueIs transmitted using the wavelength wptx (T), at time T-T_nValue of bitUsing a wavelength wptx (T-T)_Tx) Is sent, …, at time t-k.T_TxValue of bitUsing a wavelength wptx (t-k.T)_Tx) Is sent, …, at time t-BCH _ size.T_TxValue of bitUsing a wavelength wptx (t-BCH)_size.T_Tx) Is transmitted. Therefore, the transmission wavelength vector is a vector of values representing wavelengths at different time values, the length of which corresponds to the channel depth of the reverse channel Bch _ size.

In some embodiments, a wavelength value corresponding to the sub-sampled time value may be determined (e.g., wptx (T-dts) for time value T-dts, where dts < T_Tx). In fact, the detuning of interest does not change in a random manner from one time symbol to the next, but corresponds to a continuously changing physical value. Thus, interpolation may be performed based on derivatives (e.g., first or second derivatives), top enabling sub-time sample step resolution for the proposed process. This is particularly useful for predicting the bits/symbols to be transmitted, since the value of the wavelength point corresponding to the next symbol to be transmitted or to a number of symbols to be transmitted next can be estimated, so that the next symbol to be transmitted or a number of symbols to be transmitted next and the corresponding wavelength point can be stored in a memory and thus be known.

Then referring to the reverse channel complex impulse response functionAnd the frequency domain representation of the second received signal described above by equation 2, in some embodiments, the past time point ({ t-k.T)_Tx}_{k＝0，...，Bch_size}) The wavelength values of the transmit wavelength vector at (a) may also be used to determine a value representing the reverse channel, as described above. In some embodiments, the proposed processing may consider two parameters, a time parameter and a wavelength value, affecting the value of α, the time parameter corresponding to the time at which a bit or symbol generating the back reflection interference is transmitted, at which time such bit or symbol is transmitted at the wavelength value. Thus, in some embodiments, the proposed process may use an α value that depends on time and the wavelength value at that time:

one or more reverse channel look-up tables (LUTs), generated for example according to the proposed reverse channel knowledge acquisition process, may be used in some embodiments to obtain the vector shown in fig. 9, maintaining the alpha values as a function of time and wavelength at such time: { a (t-k.T)_Tx；wptx(t-k.T_Tx)}_{k＝0，...，Bch_size}。

For example,in some embodiments, the first LUT may be used for time t-k.T_TxRetrieves the value of alpha and a second LUT may be used at time t-k.T_TxWhere the wavelength point values wptx (t-k.T) are retrieved_Tx). This advantageously allows the following facts to be taken into account: for the transmitter by the transceiver at time t-k.T_TxThe back reflection of the transmitted signal reception will be utilized at time t-k.T_TxThe wavelength wptx corresponding to the wavelength of the transmitted signal is received.

Time values t-k.T respectively associated with time vectors_Tx}_{k＝-Proc_size，...，Bch_size}Corresponding detuning valueIt may also be determined, for example, using the proposed detuning measurement procedure. As mentioned above, the detuning measurement procedure may be performed regularly or only from time to reduce the calculations involved by the proposed compensation method. In particular, the above-described filtering process, which may be transmitted along each signal of the transmitter of the transceiver or perform an estimation of the detuning according to time intervals (i.e., the time-varying wavelength difference Φ (t)) in some embodiments, may be selected as a function of the time-constant driven wavelength change, as described above (e.g., with respect to temperature changes).

In some embodiments, an estimate of an interference component generated by a signal transmitted by a transmitter of a transceiver by back reflection of the transmitted signal on its signal path may be obtained by convolution of the transmitted signal and an estimated impulse response of the back channel, determined using the estimated parameters and the measured detuning. In some embodiments, the convolution operation may be expressed as an alpha value and a transmit signalThe product of the value and the tuning value at the time value t-k.T_Tx}_{k＝1，..，Bch_size}Sum of (c): at first order, the reverse channel interference component may be estimated as:

in some implementations, the convolution operation may involve components smaller than the Bch size, as it may be chosen to simplify the computation to ignore some components. For example, in the event that no back reflections are received that exceed a predetermined threshold (particularly if no back reflections are detected at the receiver), the corresponding terms of the convolution operation to be used may be ignored in some embodiments.

In the first order estimate of the reverse channel interference component, the term cos (t-k.T)_Tx) May be considered to be too computationally intensive such that the term cos (t-k.T)_Tx) In some embodiments it may be replaced by a predetermined value (e.g., equal to 1). In this case, as described above, only the amplitude distortion generated by the back reflection interference is compensated.

The wavelength point value a (wptx (t-k.T) of the signal transmitted by the transmitter of the transceiver of interest may then be based on_Tx)}_{k＝-Proc_size，...，Bch_size}(for a length of T_Tx(Proc _ size + Bch _ size) time windows are available) and based on respective detuning measures derived therefromObtaining a value of a wavelength point at a transmitter (Rxs) for a length T_Tx(Proc _ size + Bch _ size) (represented on FIG. 8 by vector (wpRxs (t + Proc _ size T)_Tx-1)；...；wpRxs(t+T_Tx)；wpRxs(t)；wpRxs(t-T_Tx)；...；wpRxs(t-k.T_Tx)；...；wpRxs(t-Bch_sizeT_Tx) Shown) transmits a source signal received at a transceiver of interest.

Then referring to the complex impulse response function H of the forward channel_p＝αe^iθAnd the frequency domain representation of the first received signal described above by equation 1, may be based on the values of the available wavelength points at the transmitter (Rxs) (transmitting the source signal received at the transceiver of interest) within the corresponding time values (represented by the vector (α (t + Proc _ sizer) in fig. 8_Tx-1)；...；α(t+T_Tx)；α(t)；α(t-T_Tx)；...；α(t-k.T_Tx)；...α(t-Bch_sizeT_Tx) Shown) to obtain a length T)_TxThe alpha value of the time window of (Proc _ size + Bch _ size).

In other embodiments, the value of α (for a length of T)_TxThe time values of the time window (Proc _ size + Bch _ size) of the wavelength point values at the transmitter (Rxs) (transmitting the source signal received at the transceiver of interest) may be ignored for the respective time values, in which case variations in the alpha values based on the wavelength of the transmitted source signal may not be considered.

In some embodiments, the determination of the vector of alpha values may include subtracting a reverse channel interference component from a signal received at a receiver of the transceiver. In an embodiment, the above estimate of the reverse channel interference component may be used to determine a vector of vectors of alpha values.

Fig. 9 illustrates an exemplary optical transceiver 80 configured to use damage mitigation features in accordance with embodiments of the present disclosure.

The transceiver 80 includes a control engine 81, an optical receiver 82, an optical transmitter 83, an optical interface 84, a memory 85, a data acquisition engine 86, a data processing engine 87, a data communication engine 88, and a clock engine (not shown).

In the architecture shown in fig. 9, the receiver 82, the transmitter 83, the optical interface 84, the memory 85, the data acquisition engine 86, the data processing engine 87, and the data communication interface 88 are all operatively coupled to one another by the control engine 81.

In one embodiment, the data acquisition engine 86 may be configured to perform various aspects of embodiments of the proposed method for receiving data, such as configuring parameters, acquiring data, and possibly performing thresholding analysis as described above with respect to the proposed back channel knowledge acquisition, and possibly filtering analysis as described above with respect to the processed detuning measurement process. Also, the data processing engine 87 is configured to perform various aspects of embodiments of the proposed method for receiving data, such as performing thresholding analysis as described above with respect to the proposed back channel knowledge acquisition, and performing filtering analysis as described above with respect to the proposed detuning measurement procedure.

In one embodiment, the data processing engine 87 may also be configured to perform impairment compensation procedures for the back channel interference compensation and/or frequency chirp detuning compensation procedures described above, e.g., based on the results of the proposed back channel knowledge acquisition and/or the detuning measurement procedures. In other embodiments, the impairment compensation process may be performed at least in part at a server node (such as the operations and management nodes shown in fig. 5, 6, and 7).

In one or more embodiments, the optical receiver 82 is configured to receive optical signals, and the optical transmitter 83 is configured to transmit optical signals. The interface 84 may be adapted to connect an optical fiber to the transceiver and may be optically coupled to the receiver 82 and the transmitter 83.

In some embodiments, the data communication engine 88 is configured to receive and/or transmit signaling messages, such as the silence request message and/or the tune-away measurement request message described above, from a network management node according to any suitable signaling protocol. Likewise, the data communication engine 88 is configured to send signaling messages (such as the silence request positive or negative acknowledgement messages, OTDR information messages, detune measurement request positive or negative acknowledgement messages, and detune measurement information messages described above) to the network management node according to any suitable signaling protocol. Data communication engine 88 may also be communicatively coupled to a network management node through one or more data communication networks.

Control engine 81 includes a processor, which may be any suitable microprocessor, microcontroller, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), digital signal processing chip and/or state machine, or combination thereof. The control engine 81 may also include or may be in communication with a computer storage medium, such as, but not limited to, a memory 85 capable of storing computer program instructions or software code that, when executed by a processor, cause the processor to perform the elements described herein. Furthermore, memory 85 may be any type of data storage computer storage medium capable of storing data acquired by receiver 82, such as during OTDR reverse channel knowledge acquisition or detuned measurement data acquisition.

It should be understood that the transceiver 80 shown and described with reference to fig. 9 is provided as an example only. Many other architectures, operating environments, and configurations are possible. Other embodiments of the transceiver may include a fewer or greater number of components and may incorporate some or all of the functionality described with respect to the transceiver components shown in fig. 9. Thus, while control engine 81, receiver 82, transmitter 83, optical interface 84, memory 85, data acquisition engine 86, data processing engine 87, and data communication engine 88 are shown as part of transceiver 80, there is no limitation on the location and control of components 81-88. In particular, in other embodiments, the components 81-88 may be part of different entities, devices, or systems.

Although the present invention has been described in connection with the preferred embodiments, those skilled in the art will readily appreciate that various changes and/or modifications may be made to the invention without departing from the spirit or scope of the invention as defined by the appended claims.

Although the present invention has been disclosed in the context of certain preferred embodiments, it should be understood that certain advantages, features and aspects of the systems, devices and methods may be realized in various other embodiments. Moreover, it is contemplated that the various aspects and features described herein may be practiced separately, combined together or substituted for one another, and that various combinations and subcombinations of the various features and aspects may be made and still fall within the scope of the invention. Further, the above-described systems and devices need not include all of the modules and functions described in the preferred embodiments.

The information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Depending on the implementation, certain acts, events or functions of any of the methods described herein can be performed in a different order, may be added, merged, or omitted altogether (e.g., not all described acts or events are necessary for the practice of the methods). Further, in some embodiments, acts or events may be performed concurrently rather than sequentially.