阅读说明：本技术 一种多粒度混合的光正交模分复用接入系统 (Multi-granularity mixed optical orthogonal mode division multiplexing access system ) 是由 刘博� 忻向军 任建新 毛雅亚 渠松松 王瑞春 沈磊 李良川 周锐 王光全 吴泳 于 2020-03-30 设计创作，主要内容包括：本发明提供了一种基于光正交模分复用,电码分复用正交频分复用的新型无源光网络接入系统,使不同的用户/服务可以同时占用相同的子载波,并且可以消除由于高代码相关性而导致的不同用户/服务之间的干扰,另外由于具有很高的码增益,可以抵抗功率分配器的损耗,从而支持更多的用户,并减轻不同用户之间的差拍噪声,同时采用多模光纤作为传输媒介,每种模式可以单独传输终端到用户的信号,并提出了光正交模分复用的方法,从而消除了模式与模式之间的串扰,大大提高了系统的信息传输质量。(The invention provides a novel passive optical network access system based on optical orthogonal mode division multiplexing and code division multiplexing orthogonal frequency division multiplexing, which enables different users/services to simultaneously occupy the same subcarrier, eliminates the interference between different users/services due to high code correlation, resists the loss of a power distributor due to high code gain, supports more users and lightens the beat noise between different users, simultaneously adopts multimode optical fiber as a transmission medium, can independently transmit signals from a terminal to the user in each mode, and provides an optical orthogonal mode division multiplexing method, thereby eliminating the crosstalk between the modes and greatly improving the information transmission quality of the system.)

1. A multi-granularity mixed optical orthogonal mode division multiplexing access system is characterized in that: comprises at least one terminal digital signal processing module for processing output of digital signal according to terminal input data,

the digital-to-analog conversion and modulation module is used for performing digital-to-analog conversion on the digital signal output by the terminal digital signal processing module and loading an analog signal onto a laser carrier;

the multiplexing and demultiplexing optical fiber transmission module is used for multiplexing the optical signal and then demultiplexing and transmitting the optical signal to the user side through the multimode optical fiber;

and the user side is used for receiving the optical signals transmitted by the multiplexing and demultiplexing optical fiber transmission module and demodulating the optical signals to extract the data signals.

2. The multi-granularity mixed optical orthogonal mode division multiplexing access system according to claim 1, characterized in that: and the terminal digital signal processing module is internally provided with chips with the same number as that of users.

3. The multi-granularity mixed optical orthogonal mode division multiplexing access system according to claim 1, characterized in that: the digital-to-analog conversion and modulation module comprises an arbitrary wave generator, and the arbitrary wave generator performs digital-to-analog conversion on the digital signal input by the terminal digital signal processing module and generates an optical signal by combining a laser, a spatial light modulator and a Mach-Zehnder modulator.

4. The multi-granularity mixed optical orthogonal mode division multiplexing access system according to claim 3, wherein: the multiplexing and demultiplexing optical fiber transmission module comprises a mode multiplexer, a multimode optical fiber and a mode demultiplexer, wherein the mode multiplexer couples the optical signal converted by the Mach-Zehnder modulator into the multimode optical fiber through an orthogonal mode, and the optical signal in the multimode optical fiber is demultiplexed and reduced by the mode demultiplexer to the user side.

5. The multi-granularity mixed optical orthogonal mode division multiplexing access system according to claim 4, wherein: the user side specifically includes that the optical signal demultiplexed and restored by the mode demultiplexer is transmitted to the spatial light modulator through an orthogonal mode, and then distributed to the user through the power distributor.

6. The multi-granularity mixed optical orthogonal mode division multiplexing access system according to claim 4, wherein: the multimode fiber is also provided with an erbium-doped fiber amplifier.

7. The system of claim 2, wherein: the chips are encoded using walsh codes.

Technical Field

The invention belongs to the technical field of communication, and particularly relates to a multi-granularity mixed optical orthogonal mode division multiplexing access system.

Background

Orthogonal frequency division multiplexing passive optical networks are considered as an effective solution for future broadband access networks due to their high spectral efficiency, high dispersion tolerance and flexibility in provisioning of multiple services and dynamic bandwidth allocation. In recent years, much research and development has been focused on orthogonal frequency division multiplexing passive optical networks, such as hybrid wavelength division multiplexing-orthogonal frequency division multiplexing passive optical networks and hybrid time division multiplexing-orthogonal frequency division multiplexing passive optical networks. However, wdm-OFDM passive optical network systems require a large number of high-speed OFDM transceivers and arrayed waveguide gratings to allocate broadband among the optical network units, which not only increases system cost and complexity, but also lacks flexibility to dynamically allocate resources among multiple networks according to the needs among different services and users. The tdm-ofdm passive optical network system supports dynamic allocation of bandwidth between different services and users, but improvements are still needed, such as interference between different users caused by downlink transmission and insecurity of the physical layer. The cdma technology has many attractive functions such as high power budget, a secure physical layer, low interference between different users and low beat noise between different channels.

System capacity has been increased by using two polarization modes in a single mode fiber to carry the signal. However, multiple modes in the same core, which may be transmission channels of a pair, may be referred to as mode multiplexing. At present, developed countries such as the united states and japan have conducted a great deal of research and have rapidly developed for ultra-high capacity transmission of novel optical fibers such as few-mode optical fibers. Therefore, multi-core optical fiber based on mode multiplexing technology is becoming a trend of optical fiber communication development. The mode multiplexing technology is a novel optical communication technology based on an optical fiber waveguide transmission mode, adopts a higher-order mode as a carrier in addition to a basic transmission mode, performs mode division multiplexing, and realizes higher capacity and higher transmission rate. In a mode multiplexing transmission system, because a multimode fiber (generally, the number of transmission modes is 2-10) has a larger mode field area, the influence of intermodal dispersion, intermodal coupling and nonlinear damage in mode transmission is slightly smaller than that of the traditional multimode fiber, and therefore the mode multiplexing transmission system has great research value.

However, since the multimode optical fiber inevitably has defects of refractive index distribution caused by materials, processes and the like in the manufacturing process, and is influenced by microbending, optical fiber span mismatch and the like caused by external force in the laying engineering, mutual coupling crosstalk occurs in the originally orthogonal transmission mode in transmission, and the coupling is random, which causes the ambiguity of mode signals at the receiving end, and the transmission performance is limited.

Disclosure of Invention

Technical problem to be solved

The present invention is directed to a multi-granularity hybrid optical orthogonal mode division multiplexing access system, so as to solve the practical problems mentioned in the background art.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme: a mixed multi-granularity optical orthogonal-mode-division multiplexing access system comprises at least one terminal digital signal processing module for processing and outputting digital signals according to terminal input data,

the digital-to-analog conversion and modulation module is used for performing digital-to-analog conversion on the digital signal output by the terminal digital signal processing module and loading an analog signal onto a laser carrier;

the multiplexing and demultiplexing optical fiber transmission module is used for multiplexing the optical signal and then demultiplexing and transmitting the optical signal to the user side through the multimode optical fiber;

and the user side is used for receiving the optical signals transmitted by the multiplexing and demultiplexing optical fiber transmission module and demodulating the optical signals to extract the data signals.

Further, the terminal digital signal processing module is provided with chips with the same number as the users.

Further, the digital-to-analog conversion and modulation module comprises an arbitrary wave generator, and the arbitrary wave generator performs digital-to-analog conversion on the digital signal input by the terminal digital signal processing module and generates an optical signal by combining the laser, the spatial light modulator and the mach-zehnder modulator.

Further, the multiplexing and demultiplexing optical fiber transmission module includes a mode multiplexer, a multimode optical fiber and a mode demultiplexer, the mode multiplexer couples the optical signal converted by the mach-zehnder modulator into the multimode optical fiber through an orthogonal mode, and the optical signal in the multimode optical fiber is demultiplexed and reduced by the mode demultiplexer to the user side.

Further, the user side specifically includes that the optical signal demultiplexed and restored by the mode demultiplexer is transmitted to the spatial light modulator through the orthogonal mode, and then distributed to the user through the power distributor.

Furthermore, an erbium-doped fiber amplifier is also arranged on the multimode fiber.

Further, the chips are encoded with walsh codes.

(III) advantageous effects

The invention dynamically allocates the flexibility of resources among a plurality of networks according to the requirements of different services and users, carries out mode division multiplexing, realizes the novel optical communication technology with higher capacity and higher transmission rate, adopts the orthogonal mode division multiplexing method to carry out multiplexing and demultiplexing at two ends of a multimode optical fiber, and the modes are orthogonal with each other, thereby avoiding the coupling crosstalk among the modes in the transmission process, greatly improving the transmission capacity of the system and avoiding the fuzzy problem of signals at a receiving end.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic structural view of example 1 of the present invention;

FIG. 2 is a schematic diagram illustrating the generation of orthogonal modes according to the present invention;

fig. 3 is a flow chart of the ue downlink propagation according to the present invention;

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1 and 3, a 3-mode fiber communication system is taken as an embodiment 1 of the present invention, after a terminal is first constellation-mapped, different chips are allocated according to different demands of users, a downlink channel is spread with chips and then allocated to given subcarriers to generate an OFDM frame, which is implemented by inverse fast fourier transform, wherein each chip is encoded with a walsh code defined by a hadamard matrix with the order of 2L, and thus the spreading matrix is a hadamard matrix

Let u [ k ] and v [ k ] be QAM data symbols, where k represents the kth symbol. After power adaptation, the coded signal is mapped into OFDM subcarriers by inverse fourier transform, and the kth OFDM symbol can be written as

Where m is the mth user, f_iThe method comprises the steps of representing the ith subcarrier of an OFDM signal, representing the number of the subcarriers of the OFDM, generating an ECDM-OFDM signal, uploading the ECDM-OFDM signal to an arbitrary waveform generator for digital/analog conversion, then loading the converted ECDM-OFDM signal to a Mach-Zehnder modulator for conversion into an optical signal, similarly, generating optical signals in other two modes by the method, modulating the three modes by a spatial light modulator, multiplexing the three modes, then transmitting the optical signals to a user terminal by a few-mode optical fiber, amplifying the optical signals by an EDFA (for compensating attenuation in the signal transmission process), and finally demultiplexing and reducing the optical signals into three modes before multiplexing. At a user end, the orthogonal mode 1, the orthogonal mode 2 and the orthogonal mode 3 are respectively modulated into a low-order mode through the spatial light modulator, and optical signals of the three modes are respectively distributed to the user through the power divider. The optical signal carrying information is converted into analog electric signal by a photoelectric detector, converted into digital electric signal by analog/digital, divided into two paths of signals after I-Q modulation, and then extracted from the subcarrier by fast Fourier transform and related to a special code chip. Due to the orthogonal nature of the walsh codes, correct data can be extracted from the downstream signal and interference of two ONUs can be eliminated. And finally, the binary bit stream is restored through constellation demapping.

In order to further explain the principle of the orthogonal mode in the embodiment, please refer to fig. 2, the field intensity of the coupled light spots of the three orthogonal modes is observed and observed through the CCD, the field intensity of the coupled light spots is distributed in a ring shape, compared with the traditional few-mode multiplexing, no interference exists between each mode and each mode, the method of orthogonal mode division multiplexing is adopted, light of the three orthogonal modes is respectively generated by a spatial light modulator at the multiplexing end and is coupled into a multimode optical fiber after multiplexing, the coupled light spots are in a ring shape, thus, no crosstalk exists between the modes, and the light of the three orthogonal modes at the demultiplexing end is demodulated back to the fundamental mode light after passing through the spatial light modulator.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.