阅读说明：本技术 光学转发器及其控制方法 (Optical transponder and control method thereof ) 是由 中田树宏 于 2020-02-26 设计创作，主要内容包括：[问题]降低光学转发器的电力消耗。[解决方案]该光学转发器具有：客户端接口,其发送和接收客户端信号；线路接口,具有进行用于使用数字相干系统传输客户端信号的信号处理的信号处理电路以及在客户端信号和光学信号之间进行转换的光学收发器；以及控制单元,用于根据客户端信号的带宽控制信号处理电路的操作。([ problem ] to reduce power consumption of an optical repeater. [ solution ] this optical transponder has: a client interface that transmits and receives client signals; a line interface having a signal processing circuit that performs signal processing for transmitting a client signal using a digital coherent system and an optical transceiver that converts between the client signal and an optical signal; and a control unit for controlling the operation of the signal processing circuit according to the bandwidth of the client signal.)

1. An optical transponder, comprising:

a client interface that sends and receives client signals;

a line interface, the line interface comprising: signal processing means for performing signal processing for transmitting the client signal by a digital coherent scheme; and an optical transceiver that performs conversion between the client signal and an optical signal; and

control means for controlling the activation of the signal processing means in dependence on the bandwidth of the client signal.

2. The optical repeater according to claim 1,

each of the plurality of line interfaces includes the signal processing device, and

the control means calculates the number of active line interfaces according to the bandwidth of the client signal, and activates or deactivates each of the signal processing means of the plurality of line interfaces according to the number of active line interfaces.

3. The optical repeater according to claim 2, wherein the control means activates or deactivates each of the signal processing means of the plurality of line interfaces according to a bandwidth of the line interface.

4. The optical repeater according to any one of claims 1 to 3,

the control means generates information on an active state and an inactive state of each of the signal processing means of the line interface, and information indicating activation and deactivation of the signal processing means included in the opposite station, and

the line interface transmits the generated information to the opposite station.

5. The optical repeater according to any one of claims 1 to 4,

the line interface includes:

optical transmission means for modulating an optical carrier in accordance with the client signal input to the optical repeater, generating the modulated optical carrier, and outputting the modulated optical carrier from the optical repeater; and

an optical receiving device for demodulating an optical signal input to the optical repeater and outputting the demodulated client signal from the optical repeater, and

each of the optical transmission device and the optical reception device includes the signal processing device.

6. The optical repeater according to any one of claims 1 to 5,

the line interface further includes a dummy pattern generation unit that generates a dummy pattern,

when the signal processing device is inactive, the optical transceiver outputs an optical signal modulated with the pseudo mode, and

the optical signal modulated with the dummy pattern includes an optical profile similar to an optical signal modulated with the client signal input to the optical transponder.

7. The optical repeater according to any one of claims 1 to 6, further comprising a switch connected between the client interface and the line interface, wherein,

the switch, in response to an instruction from the control device, connects between the client interface and a plurality of the line interfaces to be activated, according to a bandwidth of the client signal input to the optical repeater.

8. The optical repeater according to claim 7,

the control device generates connection settings for the switch between the client signals and the line interface, and

the line interface sends the generated connection settings.

9. The optical repeater according to claim 7 or 8,

the connection between the client interface and the line interface at the switch is set by a port-based Virtual Local Area Network (VLAN).

10. An end station device comprising an optical repeater according to any one of claims 1 to 9, and

multiplexing/demultiplexing means for wavelength division multiplexing optical signals output by the optical repeater and outputting the wavelength division multiplexed optical signals to a transmission line, and separating wavelength division multiplexed optical signals input from the transmission line and outputting the separated wavelength division multiplexed optical signals to the optical repeater.

11. An optical transmission system comprising the terminal station device according to claim 10 and the transmission line, wherein,

two or more of the terminal station devices are communicably connected to each other via the transmission line.

12. A method of controlling an optical repeater, comprising:

sending and receiving, by a client interface, a client signal;

performing, by a signal processing apparatus included in the line interface, signal processing for transmitting the client signal by a digital coherent scheme;

converting, by an optical transceiver included in the line interface, between the client signal and an optical signal; and

controlling, by a control device, activation of the signal processing device in accordance with a bandwidth of the client signal.

13. The control method of the optical repeater according to claim 12, further comprising:

calculating, by the control means, a number of the plurality of active line interfaces according to a bandwidth of the client signal, and activating or deactivating each of the signal processing means of the plurality of line interfaces according to the number of the plurality of active line interfaces.

14. The method of controlling an optical repeater according to claim 13, further comprising:

activating or deactivating, by the control means, each of the signal processing means of a plurality of the line interfaces in accordance with the bandwidth of the line interface.

15. The control method of the optical repeater according to any one of claims 12 to 14, further comprising:

generating, by the control means, information on an active state and an inactive state of each of the signal processing means of the line interface, and information indicating activation and deactivation of the signal processing means included in the opposite station; and

transmitting, by the line interface, the generated information to the opposite station.

16. The control method of the optical repeater according to any one of claims 12 to 15, further comprising:

modulating, by optical transmission means including the signal processing means, an optical carrier in accordance with the client signal input to the optical repeater, generating the modulated optical carrier, and outputting the modulated optical carrier from the optical repeater; and

demodulating, by an optical receiving apparatus including the signal processing apparatus, an optical signal input to the optical repeater, and outputting the demodulated client signal from the optical repeater.

17. The control method of the optical repeater according to any one of claims 12 to 16, further comprising:

outputting, by the optical transceiver, an optical signal modulated with a dummy pattern when the signal processing device is inactive, wherein,

the optical signal modulated with the dummy pattern includes an optical profile similar to an optical signal modulated with the client signal input to the optical transponder.

18. The control method of the optical repeater according to any one of claims 12 to 17, further comprising:

by a switch connected between the client interface and the line interface,

in response to an instruction from the control means, a connection is made between the client interface and a plurality of the line interfaces to be activated in accordance with a bandwidth of the client signal input to the optical repeater.

19. The method of controlling an optical repeater according to claim 18, further comprising:

generating, by the control device, connection settings for the switch between the client signal and the line interface; and

sending, by the line interface, the generated connection setting.

20. The control method of the optical repeater according to claim 18 or 19, further comprising:

setting up, by a port-based Virtual Local Area Network (VLAN), a connection between the client interface and the line interface at the switch.

21. A method of controlling an optical repeater, comprising:

performing, by a signal processing apparatus, signal processing for transmitting and receiving a client signal by a digital coherent scheme;

performing a conversion between the client signal and an optical signal; and

controlling the activation of the signal processing means in dependence on the bandwidth of the client signal.

Technical Field

The present invention relates to an optical repeater and a control method thereof, and more particularly, to an optical repeater used in an optical communication system to which a digital coherent scheme is applied and a control method thereof.

Background

Recent submarine cable systems achieve large capacity and high-speed transmission by using optical repeaters (hereinafter, simply referred to as "repeaters") adopting a digital coherent scheme. In the digital coherent scheme, large capacity transmission is achieved by digital signal processing of the signal to be transmitted and further modulating the frequency, phase and amplitude of the optical carrier. Meanwhile, a repeater used in the digital coherent scheme performs high-speed signal processing using a Digital Signal Processor (DSP) and its peripheral circuits, thereby consuming large electric power. The increase in power consumption of the repeater not only increases environmental load but also becomes a factor of a large-scale heat dissipation structure and noise due to the cooling fan. Therefore, the increase in power consumption due to the DSP becomes an obstacle to high functionality and high integration of the optical transmission device equipped with the repeater.

In connection with the present invention, patent document 1 describes an optical transmission system in which WDM repeaters are controlled according to the number of L2 link aggregations in one client device.

[ list of references ]

[ patent document ]

[ patent document 1] Japanese unexamined patent application publication No.2010-283571

Disclosure of Invention

[ problem ] to

The transmission capacity (e.g., the number of multiplexed wavelengths) of a submarine cable system is designed according to the peak time bandwidth of the signal to be transmitted (client signal). However, the bandwidth required by the system varies depending on the increase or decrease in communication demand, and it is not always necessary to use all wavelengths that can be multiplexed for transmission. Further, in a general submarine cable system, it is impossible to determine whether a client signal is included in a received optical signal until an electrical signal is reproduced from the received optical signal. Therefore, even for signals that are not required in nature, it is necessary to perform digital signal processing on client signals by using a DSP in the repeater. Therefore, even when the client signal has a small data amount (bandwidth), it is difficult to reduce power consumption of the repeater.

(objects of the invention)

The object of the invention is to reduce the power consumption of a repeater.

[ problem solution ]

The optical repeater according to the present invention includes: a client interface that transmits and receives client signals; a line interface including a signal processing device for performing signal processing for transmitting a client signal by a digital coherent scheme and an optical transceiver for performing conversion between the client signal and an optical signal; and control means for controlling the activation of the signal processing means in dependence on the bandwidth of the client signal.

The control method of the optical repeater according to the present invention includes: performing, by a signal processing apparatus, signal processing for transmitting and receiving a client signal by a digital coherent scheme; performing a conversion between the client signal and the optical signal; and controlling the activation of the signal processing means in dependence of the bandwidth of the client signal.

[ advantageous effects of the invention ]

The repeater according to the present invention enables power consumption to be reduced according to the bandwidth of the client signal.

Drawings

Fig. 1 is a block diagram illustrating a configuration example of a submarine cable system 1000 according to a first exemplary embodiment.

Fig. 2 is a block diagram illustrating a configuration example of the repeater 10 according to the first exemplary embodiment.

Fig. 3 is a block diagram illustrating a configuration example of the repeater 11 according to the second exemplary embodiment.

Fig. 4 is a block diagram illustrating a configuration example of the line interface 201 according to the second exemplary embodiment.

Fig. 5 is a diagram illustrating an example of information indicating an activation request for a line interface of an opposite station.

Fig. 6 is a diagram illustrating an example of information indicating an active state of a line interface.

Fig. 7 is a flowchart illustrating an example of an operation procedure of the control unit 300.

Fig. 8 is a diagram illustrating an example of a change in the number of line interfaces to be in an active state.

Fig. 9 is a diagram illustrating an example of a spectrum of an optical signal transmitted by the terminal station 1001.

Fig. 10 is a block diagram illustrating a configuration example of a submarine cable system 2000 according to the third exemplary embodiment.

Fig. 11 is a block diagram illustrating a configuration example of the repeater 12 according to the fourth exemplary embodiment.

Fig. 12 is a diagram illustrating a selection example of the line interface.

Fig. 13 is a diagram illustrating an example of wavelength arrangement when line interfaces having different transmission schemes coexist.

Detailed Description

(first exemplary embodiment)

Fig. 1 is a block diagram illustrating a configuration example of a submarine cable system 1000 according to a first exemplary embodiment. The terminal stations 1001 and 1002 are optical transmission equipment disposed on land, and are opposed to and communicatively connected to each other by the submarine cable 40. The submarine cable 40 is an optical transmission line including an optical repeater. The undersea optical fiber cable 40 may also include undersea optical branching and coupling equipment and the like used in general undersea optical fiber cable systems. Note that in each drawing, arrows assigned to signals are illustrative, and do not limit the direction of signals.

Each of the terminal stations 1001 and 1002 includes a repeater (transponder)10, a multiplexing/demultiplexing unit 20, and a pseudo light source 50. The same specification of the repeater 10 and the multiplexing/demultiplexing unit 20 can be commonly used in the terminal stations 1001 and 1002. The terminal station 1001 will be described below, but the terminal station 1002 also includes similar functions.

The repeater 10 is connected to a plurality of client devices 30 located outside the terminal stations 1001 and 1002, and transmits and receives client signals to and from the client devices 30. The client device 30 is, for example, a communication device connected to a network of users of the submarine cable system 1000. A client device 30 may be connected to the repeater 10 via a plurality of transmission lines. The repeater 10 generates a plurality of optical signals modulated by a digital coherent scheme from a client signal received from the client device 30 and outputs the plurality of optical signals to the multiplexing/demultiplexing unit 20. The plurality of optical signals output by the transponder 10 have mutually different wavelengths. Further, the repeater 10 of the terminal station 1001 demodulates the client signal by detecting the optical signal received from the multiplexing/demultiplexing unit 20 and transmitted by the terminal station 1002 via a digital coherent scheme. The client signals demodulated in the terminal station 1001 are client signals output from a plurality of client devices 30 connected to the terminal station 1002. The repeater 10 of the terminal station 1001 outputs the demodulated client signal to the client device 30 connected to the terminal station 1001.

The multiplexing/demultiplexing unit 20 of the terminal station 1001 receives the optical signal generated by the repeater 10 from a port different for each wavelength, and generates a Wavelength Division Multiplexed (WDM) signal by wavelength division multiplexing the optical signal. The generated WDM signal is transmitted to the terminal station 1002 via the submarine cable 40. Further, the multiplexing/demultiplexing unit 20 of the end station 1001 separates the WDM signal received for each wavelength from the end station 1002 through the submarine cable 40 and outputs the separated optical signals from different ports to different ports of the repeater 10. The multiplexing/demultiplexing unit 20 may be implemented by using, for example, a dielectric multilayer film filter or an Arrayed Waveguide Grating (AWG).

The pseudo light source 50 outputs light for compensating for the wavelength dependence of the transmission characteristic of the undersea optical cable 40. For example, when the undersea optical fiber cable 40 includes an optical amplifier, the wavelength dependence of the gain of the optical amplifier is reduced by outputting dummy light via the dummy light source 50, and thus the spectrum of the WDM signal can be flatter. The wavelength of the dummy light is set so as not to overlap the wavelength of the optical carrier transmitted by the transponder 10. When such compensation of wavelength dependence is not required, the pseudo light source 50 may not be used.

Fig. 2 is a block diagram illustrating a configuration example of the repeater 10 included in the end stations 1001 and 1002. The repeater 10 includes a client interface 100, a line interface 200, and a control unit 300. Note that as shown in fig. 1, the client interface 100 may be connected with a plurality of client devices 30. Further, the line interface 200 may transmit and receive a plurality of optical signals to and from the multiplexing/demultiplexing unit 20.

The client interface 100 transmits client signals to the client device 30 and receives client signals from the client device 30. The client interface 100 receives the packet signal from the client device 30 and outputs the packet signal to the line interface 200. Further, the client interface 100 outputs a client signal to be transmitted to the client device 30, which is included in an optical signal input from the line interface 200 and transmitted by an opposite terminal station (hereinafter referred to as "opposite station"). The packet signal is a signal including packet data used in, for example, ethernet (registered trademark) or a Local Area Network (LAN).

The line interface 200 includes an optical transceiver 210 and a signal processing unit 220. The line interface 200 performs conversion between an optical signal and a packet signal input and output from the client interface 100. The optical transceiver 210 is an optical transmitter/receiver and coherently modulates the client signal processed by the signal processing unit 220 and coherently detects an optical signal received from the opposite station. The signal processing unit 220 includes a DSP221 and performs digital signal processing for transmitting and receiving a client signal through a digital coherent scheme.

The optical transceiver 210 performs coherent detection on an optical signal input from the multiplexing/demultiplexing unit 20 and received from the opposite station. The signal processing unit 220 demodulates the client signal by performing signal processing by a digital coherent scheme such as dispersion compensation on the detected signal, and outputs the client signal to the client interface 100.

Further, the signal processing unit 220 performs signal processing such as overhead processing on the client signal input from the client interface 100 before coherent modulation. The optical transceiver 210 converts the client signal processed by the signal processing unit 220 into an optical signal by performing coherent modulation, and outputs the optical signal to the multiplexing/demultiplexing unit 20.

The control unit 300 controls each part of the repeater 10. The control unit 300 controls the activation of the signal processing unit 220 according to the bandwidth of the client signal transmitted and received by the client interface 100. For example, the control unit 300 individually activates or deactivates the DSP221 included in each of the plurality of signal processing units 220 according to the bandwidth of the client signal. The signal processing unit 220, in which the DSP221 is active, performs digital signal processing on the transmitted and received client signals. The signal processing unit 220 in which the DSP221 is inactive is deactivated and does not perform processing of the client signal.

For example, when the bandwidth required for transmitting the client signal is reduced due to a reduction in the amount of data of the client signal transmitted and received by the repeater 10, the control unit 300 suppresses activation of the DSP221 included in the repeater 10. When the repeater 10 includes a plurality of DSPs 221, the control unit 300 reduces the number of active DSPs 221 in response to a reduction in the client signal bandwidth and deactivates the DSPs 221 that do not require processing.

The repeater 10 including such a configuration can reduce power consumption of the repeater 10 and the terminal stations 1001 and 1002. The reason is that the control unit 300 controls the activation of the DSP221 according to the bandwidth of the client signal.

(second example embodiment)

Fig. 3 is a block diagram illustrating a configuration example of the repeater 11 according to the second exemplary embodiment of the present invention. The repeater 11 includes a switch 400 in addition to the repeater 10 described in the first exemplary embodiment. Further, the repeater 11 may be used in place of the repeater 10 in the terminal stations 1001 and 1002. The repeater 11 includes ten client interfaces 101 to 110, eight line interfaces 201 to 208, a control unit 300, and a switch 400. The client interfaces 101 to 110 in fig. 3 are equivalent to the client interface 100 in fig. 2. The line interfaces 201 to 208 in fig. 3 are equivalent to the line interface 200 in fig. 2.

Each of the client interfaces 101 to 110 transmits and receives a client signal to and from the client device 30 external to the repeater 11. The client interfaces 101 to 110 receive client signals to be transmitted to the opposite station from the client devices 30 connected thereto, and output the client signals to the switch 400. Further, the client interfaces 101 to 110 output the client signals output by the switch 400 to the client device 30. The client signals output by switch 400 to client interfaces 101 to 110 are client signals demodulated by line interfaces 201 to 208 from optical signals received from opposite stations. One client device 30 may interface with multiple clients.

Similar to the line interface 200 in fig. 2, all of the line interfaces 201 to 208 include an optical transceiver 210 and a signal processing unit 220. The line interfaces 201 to 208 perform digital signal processing on the client signal input from the switch 400, convert the processed signal into an optical signal, and output the optical signal to the multiplexing/demultiplexing unit 20. The client signal input from the switch 400 to the line interfaces 201 to 208 is a client signal transmitted to the opposite station. Further, the line interfaces 201 to 208 perform coherent detection on the optical signals separated from the WDM signal by the multiplexing/demultiplexing unit 20, generate client signals by further performing digital signal processing on the optical signals, and output the client signals to the switch 400. The client signals output by the line interfaces 201 to 208 to the switch 400 are client signals output by the switch 400 to the line interfaces 201 to 208 in the opposite station.

The wavelengths of the optical signals transmitted and received by the line interfaces 201 to 208 and the wavelengths of the optical signals input and output through each port of the multiplexing/demultiplexing unit 20 are set so that the opposite line interfaces having the same reference numeral are connected to each other. In other words, when the optical signals transmitted by the line interfaces 201 to 208 of the terminal station 1001 have wavelengths λ 1 to λ 8, the multiplexing/demultiplexing unit 20 of the terminal station 1001 outputs WDM signals that combine the optical signals having wavelengths λ 1 to λ 8 to the submarine cable 40. The multiplexing/demultiplexing unit 20 of the terminal station 1002 separates the WDM signal into optical signals having wavelengths λ 1 to λ 8, and outputs the optical signals to the line interfaces 201 to 208 of the terminal station 1002. As a result, for example, the line interface 201 of the terminal station 1002 receives the optical signal of the wavelength λ 1 transmitted by the line interface 201 of the terminal station 1001.

Switch 400 is a packet switch having multiple ports on both the client interface side and the line interface side. The switch 400 is connected between the client interfaces 101 to 110 and the line interfaces 201 to 208 connected to the ports of each side according to the instruction of the control unit 300. The switch 400 is connected between the client interfaces 101 to 110 and one or more of the line interfaces 201 to 208 in which the DSP221 is active, depending on the total bandwidth of the client signals and the bandwidth of each of the line interfaces 201 to 208.

The switch 400 according to the present exemplary embodiment is arranged inside the repeater 11. When the switch 400 is arranged inside the repeater 11, it becomes easy to design in such a manner that the speed of each port of the switch 400 is uniform between the client interfaces 101 to 110 and the line interfaces 201 to 208. As a result, efficient and detailed bandwidth control of the repeater 11 becomes possible. On the other hand, when the switch 400 is arranged as a single device outside the repeater 11, the necessity arises to connect between the switch 400 and the repeater 11 through a common physical interface. In this case, since the physical interface between the switch 400 and the repeater 11 has limited options for specifications including speed, it becomes difficult to flexibly distribute the client signals to the line interfaces 201 to 208 according to the bandwidth.

Upon an instruction from the control unit 300, each of the line interfaces 201 to 208 is set to an active state or an inactive state. The line interface in which the DSP221 is active is in an active state, and the signal processing unit 220 performs digital signal processing for transmitting and receiving a client signal. The line interface in which the DSP221 is inactive. In this case, the signal processing unit 220 does not perform digital signal processing on the client signal. Therefore, the power consumption of the line interface can be reduced by deactivating the DSP 221. Note that even in the inactive state, the line interfaces 201 to 208 can operate circuits that do not use the DSP 221. As described below, when the DSP221 is deactivated, the dummy pattern generation unit 251 included in the signal processing unit 220 generates a dummy pattern and outputs it to the optical transceiver 210. The line interface in the inactive state then generates an optical signal modulated with the dummy pattern.

The control unit 300 controls a connection between the client interface side port and the line interface side port of the switch 400 and activation of the DSP221 included in the line interface 200 according to the bandwidth of the client signal. The control unit 300 acquires the bandwidth (traffic volume) of the client signal received from the client interfaces 101 to 110 connected to the repeater 11. The control unit 300 has a function of communicating with the line interfaces 201 to 208, and can set the line interfaces 201 to 208 independently into an active state or into an inactive state.

Fig. 4 is a block diagram illustrating a configuration example of the line interface 201 according to the second exemplary embodiment. Hereinafter, the configuration and function of the line interface 201 will be described. The line interfaces 202 to 208 have a configuration and function similar to those of the line interface 201. The line interface 201 includes a line control unit 231, a transmission signal processing unit 232, a modulator 233, a light source 234, a polarization synthesizer 235, and an optical Amplifier (AMP) 236. Further, the line interface 201 includes an optical amplifier 237, a polarization splitter 238, a 90-degree mixer 239, a light source 240, and a received signal processing unit 241.

The DSP221 is included in the signal processing unit 220 similarly to fig. 1, but is not shown in fig. 4. One DSP221 can realize the functions of the transmission signal processing unit 232 and the reception signal processing unit 241 of the line interface 201.

The transmission signal processing unit 232 and the reception signal processing unit 241 are one example of a configuration that realizes the function of the signal processing unit 220 in fig. 2. Further, the modulator 233, the optical source 234, the polarization combiner 235, the optical amplifiers 236 and 237, the polarization separator 238, the 90-degree mixer 239, and the optical source 240 are one example of a configuration that realizes the function of the optical transceiver 210 in fig. 2.

The line control unit 231 communicates with the control unit 300 of the repeater 11 shown in fig. 3, and controls activation and deactivation of the DSP221 according to an instruction from the control unit 300. The functions of the control unit 300 and the functions of the line control unit 231 may be integrated into one control unit. The line control unit 231 notifies the "line activation request information" and the "line activity state information" of the line interfaces 201 to 208 notified from the control unit 300 to the transmission signal processing unit 232. Further, the line control unit 231 reads "line activation request information" and "line activity state information" transmitted by the opposite station from the received signal processing unit 241, and notifies it to the control unit 300. The "line activation request information" and the "line activity state information" will be described later.

The transmission signal processing unit 232 receives a client signal from the client device 30 via the switch 400. The transmission signal processing unit 232 performs Forward Error Correction (FEC) encoding and digital signal processing on the received client signal by using the DSP221 before outputting the client signal to the modulator 233. The DSP221 can perform polarization phase separation for polarization division multiplexing and pre-emphasis processing for compensating distortion of the optical transmission line 40. The line interface 201 set to the active state activates the DSP221 and performs digital signal processing on the client signal. The line interface 201 set to the inactive state deactivates the DSP221 and transitions to a low power consumption state.

The transmission signal processing unit 232 includes a pseudo pattern generating unit 251 and a header (header) processing unit 252. The dummy pattern generation unit 251 is a circuit independent from the DSP221, and may be arranged outside the transmission signal processing unit 232. Even when the DSP221 is inactive, the generation unit 251 can generate the pseudo mode without using the DSP 221. When the DSP221 is deactivated, the signal processing unit 220 outputs the dummy pattern generated by the dummy pattern generation unit 251 to the optical modulator 233. The pseudo pattern is, for example, random data having a similar speed as the client signal. The optical transceiver 210 of the line interface in the inactive state modulates the optical carrier by using the dummy pattern. In other words, the line interface 201 outputs the optical signal from the optical transceiver 210 to the multiplexing/demultiplexing unit 20 regardless of whether it is in an active state or an inactive state. When the DSP221 is activated, the signal processing unit 220 stops the pseudo pattern generating unit 251, and outputs the client signal processed by the DSP221 to the modulator 233.

The header processing unit 252 stores "line activation request information" and "line activity state information" of the repeater 11 in the free area of FEC _ OH added to the client signal to be transmitted, and notifies the repeater of the opposite station. FEC _ OH is an abbreviation of forward error correction overhead. The function of the header processing unit 252 is implemented by the DSP 221.

As a coherent optical transmission scheme, a Quadrature Phase Shift Keying (QPSK) scheme is known. In the QPSK scheme, 2 optical carriers that are 90 ° out of phase with different pieces of data modulation are multiplexed. Further, when a polarization division multiplexing scheme in which two QPSK optical signals having polarization planes perpendicular to each other are multiplexed and transmitted is used in combination, four pieces of data can be modulated and transmitted at the same time. Since the configuration of an optical transceiver in the polarization division multiplexing QPSK scheme is well known, hereinafter, the well-known configuration of an optical transmission/reception function included in the line interface 201 will be simply described. Further, the line interfaces 202 to 208 also transmit and receive optical signals similarly to the line interface 201.

The optical transceiver 210 in fig. 4 illustrates a configuration example when the modulation/demodulation scheme is a polarization division multiplexing QPSK scheme. However, the modulation/demodulation scheme of the optical transceiver 210 is not limited to the polarization division multiplexing QPSK scheme. The transmission signal processing unit 232 performs digital signal processing on the client signal input from the switch 400, and divides the client signal into four signals by serial-parallel conversion. The modulator 233 includes four Mach-Zehnder optical modulators. The modulator 233 modulates the optical carrier output from the optical source 234 by using the four signals output from the transmission signal processing unit 232, and outputs the optical carrier to the polarization combiner 235. The optical source 234 is an optical source that generates an optical carrier. The wavelength of the light source 234 is different for each of the line interfaces 201 to 208.

The four optical signals output from the modulator 233 generate two sets of QPSK signals having polarized waves perpendicular to each other. The polarization combiner 235 polarization-division-multiplexes (polarization-combines) the two sets of QPSK signals and outputs the polarization-division-multiplexed QPSK signal to the optical amplifier 236. The optical amplifier 236 is a booster amplifier that amplifies an optical signal to be transmitted. The optical signal amplified by the optical amplifier 236 is output to the multiplexing/demultiplexing unit 20.

The multiplexing/demultiplexing unit 20 generates a WDM signal by combining polarization division multiplexing QPSK signals output from the line interfaces 201 to 208 and transmits the WDM signal to an opposite station. Further, the multiplexing/demultiplexing unit 20 receives the WDM signal obtained by wavelength-division multiplexing the polarization-division multiplexing QPSK signal from the opposite station, and outputs the polarization-division multiplexing QPSK signal separated for each wavelength to the line interface 201 at 208. The following description also uses the line interface 201 as an example.

The line interface 201 receives the polarization division multiplexing QPSK signal from the multiplexing/demultiplexing unit 20, and amplifies the polarization division multiplexing QPSK signal by using the optical amplifier 237. The optical amplifier 237 is a preamplifier that amplifies a received optical signal. The optical signal amplified by the optical amplifier 237 is split into two QPSK signals by the polarization splitter 238. The polarization-separated QPSK signals are input to two 90-degree mixers 239. The 90-degree mixer 239 generates four reception signals from the beat signal between the QPSK signal and the local light, and outputs the four reception signals to the reception signal processing unit 241. The light source 240 is a source of local light for coherent detection of the QPSK signal.

The received signal processing unit 241 performs digital signal processing on the four received signals output from the 90-degree mixer 239, and demodulates one client signal. When the line interface 201 is set to the active state after an instruction from the line control unit 231, the received signal processing unit 241 performs digital signal processing included in the receiver of the coherent scheme by using the DSP 221. For example, the received signal processing unit 241 compensates for wavelength dispersion, polarization dispersion, and the like generated during transmission, and performs error correction based on FEC. When the line interface 201 is set to the inactive state, the DSP221 of the line interface 201 is deactivated upon an instruction of the line control unit 231. In this case, since the function using the received signal processing unit 241 of the DSP221 stops operating, the line interface 201 does not demodulate the client signal, and shifts to a low power consumption state.

The received signal processing unit 241 includes a header processing unit 261. The header processing unit 261 terminates FEC overhead (FEC _ OH) of the received signal, and extracts an activation request ("line activation request information") for a line interface of the transmission-destination end station and activity state information ("line activity state information") of the opposite station transmitted by the opposite station. The received signal processing unit 241 notifies the extracted information to the line control unit 231. The function of the header processing unit 261 is implemented by the DSP 221.

Fig. 5 is a diagram illustrating an example of information indicating an activation request for a line interface of an opposite station ("line activation request information"). In fig. 5, line (1) represents a first line interface 201 of the opposite station. For example, the "line (1) activation request" transmitted by the terminal station 1001 includes a request for setting the first line interface 201 (line (1)) included in the repeater of the terminal station 1002 as the opposite station to the active state or the inactive state. Further, the "line (1) activation request" received by the terminal station 1001 includes a request from the terminal station 1002 for setting (activating) the first line interface 201 (line (1)) included in the repeater of the terminal station 1001 in an active state or an inactive state.

The header processing unit 252 of the transmission signal processing unit 232 of at least one of the line interfaces 201 to 208 included in the terminal station 1001 stores "line activation request information" in an unused area of FEC _ OH, and transmits a plurality of pieces of "line activation request information" to the opposite station (terminal station 1002). The terminal station 1001 generates "line activation request information" so that the same line interfaces (for example, 201 to 204) as those (201 to 204) of the terminal station 1001 set to the activated state are also set to the active state in the terminal station 1002. In this case, "line (1) activation request" to "line (4) activation request" includes a request for setting the line interfaces 201 to 204 to the activated state. In this way, the line interfaces 201 to 208 of the terminal station 1001 and the line interfaces 201 to 208 of the terminal station 1002 can be operated in the same active state.

Further, the control unit 300 may allow the "line activity request information" to include settings for a connection between the client interface side port and the line interface side port of the switch 400 (hereinafter, referred to as "port settings"). When the port setting is used by the opposite station, the same port setting can be used between the opposite end stations. As described above, the line interfaces 201 to 208 of the terminal station 1001 are opposed to the line interfaces 201 to 208 of the terminal station 1002, respectively. Therefore, when the port setting of the switch 400 is shared between the terminal station 1001 and the terminal station 1002, each of the client interfaces 101 to 110 of the terminal station 1001 can be connected with the client interface assigned with the same reference numeral in the terminal station 1002. However, the above-described procedure of port setting is an example and is not mandatory. In order to transmit the client signals, the client interfaces 101 to 110 of the terminal station 1001 must be connected with the client interfaces 101 to 110 of the terminal station 1002 according to the specifications of the submarine cable system 1000. For example, based on specifications, the client interface 101 of the terminal station 1001 may connect with the client interface 110 of the terminal station 1002. In this case, the port setting of the switch 400 differs between the end station 1001 and the end station 1002.

Fig. 6 is a diagram illustrating an example of information indicating an activity state of a line interface ("line activity state information"). The "line active state information" includes information indicating whether each of the line interfaces 201 to 208 is in an active state (active) or an inactive state (inactive). For example, "line (1) active state" in fig. 6 is information on the active state of the line interface 201 of the terminal station that transmits the information. The "line (1) activation state" transmitted by the terminal station 1001 to the terminal station 1002 indicates the state of the line interface 201 of the terminal station 1001.

The terminal station 1001 stores the line activity state information together with the line activation request information in the unused area of FEC _ OH by using the header processing unit 252 of the transmission signal processing unit 232, and transmits these pieces of information to the opposite station (terminal station 1002). Similarly, the terminal station 1002 also stores line activation request information and line activity state information in an unused area of FEC _ OH, and transmits these pieces of information to the terminal station 1001. The terminal station 1001 can know the activity state of the line interface of the terminal station 1002 from the "line activity state information" received from the terminal station 1002. The terminal station 1001 can know whether or not the line interface requested in the terminal station 1002 is in an active state by comparing the "line activation request information" that has been transmitted to the terminal station 1002 with the "line active state information" received from the terminal station 1002. When the line interface requested in the terminal station 1002 is not in an active state, the terminal station 1001 may again transmit "line activation request information" to the terminal station 1002. Alternatively, the terminal station 1001 may determine that the line interface of the terminal station 1002 requesting activation has failed, possibly in exchange for a line interface activation.

(a) Setting an active state of a line interface

A procedure for setting the active state of the line interfaces 201 to 208 will be described. As shown in fig. 1, the terminal station 1001 and the terminal station 1002 are connected to each other via a submarine cable 40 so that client signals are transmitted bi-directionally between the client devices 30. The terminal station 1001 and the terminal station 1002 have the same configuration, and the terminal station 1002 also operates similarly to the terminal station 1001.

(a1) The control unit 300 of the terminal station 1001 acquires the bandwidth (traffic) of the client signal input from the client interfaces 101 to 110 to the switch 400 from the switch 400 for each of the client interfaces 101 to 110. Then, the control unit 300 calculates the total bandwidth of the client signal used in the communication between the terminal station 1001 and the client device 30.

(a2) The control unit 300 of the terminal station 1001 calculates the number of line interfaces necessary for transmitting the client signal to the terminal station 1002 based on the bandwidths that the line interfaces 201 to 208 can handle. The bandwidth allocated to each client signal of the line interfaces 201 to 208 is set not to exceed the bandwidth that can be processed by each of the line interfaces 201 to 208. Then, the control unit 300 instructs the line control unit 231 to set the calculated line interface number among the line interfaces 201 to 208 to the active state. Setting the active state or inactive state of the line interfaces 201 to 208 is performed by the line control unit 231 activating or deactivating the DSP221 in each of the line interfaces 201 to 208.

(a3) The control unit 300 of the terminal station 1001 instructs the switch 400 to allocate the client signals input to the switch 400 from the client interfaces 101 to 110 to the line interfaces set to the active state.

(a4) At least one of the line interfaces 201 to 208 of the terminal station 1001 stores the "line activation request" shown in fig. 5 and the "line active state" shown in fig. 6 in the unused area of the FEC _ OH of the transmission signal by using the header processing unit 252. The transmission signal is a client signal that is signal-processed by the transmission signal processing unit 232, and is to be transmitted to the terminal station 1002. A signal in which pieces of information are stored is modulated by the optical transceiver 210 and transmitted to the terminal station 1002.

(a5) At least one of the line interfaces 201 to 208 of the opposite station (terminal station 1002) reads the "line activation request" and the "line active state" stored in FEC _ OH in the terminal station 1001. The line control unit 231 of the terminal station 1002 notifies the control unit 300 of the terminal station 1002 of the pieces of information read.

(a6) The control unit 300 of the terminal station 1002 sets the line interfaces 201 to 208 in an active state or an inactive state in response to a request of "line activation request" transmitted by the terminal station 1001. Then, the control unit 300 distributes and outputs the client signal from the terminal station 1001 demodulated by the line interface set to the active state to the client interfaces 101 to 110 of the terminal station 1002 by using the switch 400. For example, the control unit 300 of the terminal station 1002 activates a line interface specified by a "line activation request" notified from the terminal station 1001 in the terminal station 1002.

Further, the control unit 300 may set the connections between the client interfaces 101 to 110 and the line interfaces 201 to 208 in the switch 400 by applying a port-based Virtual Local Area Network (VLAN). The control unit 300 on the side of transmitting the client signal may transmit "line activity request information" including the port setting of the switch 400 to the opposite station, and the opposite station may set the port VLAN of the switch 400 of the opposite station based on the port setting. Thereby, the same client interface (e.g., client interface 101) is interconnected between the opposite end stations.

Note that, in order to transmit and receive "line activation request information" and "line active state information" to and from the terminal station 1001 and the terminal station 1002, it is preferable that at least one pair of opposing line interfaces be set to an active state at the start of system operation.

Next, details of the operation of each part of the repeater 11 are described by using the terminal station 1001 as an example.

(b) Operation of the control unit 300

The operation of the control unit 300 will be described with reference to the flowchart in fig. 7.

(b1) The control unit 300 of the terminal station 1001 acquires information on the traffic amount of the client signals (packet signals) input from the client interfaces 101 to 110 from the switch 400. Then, the control unit 300 calculates the total bandwidth of the packets input from all the client interfaces 101 to 110 (step S01 in fig. 7).

(b2) The control unit 300 calculates the number of line interfaces to be activated according to the calculated total bandwidth (step S02), and selects a line interface to be activated from among the line interfaces 201 to 208 (step S03). Then, the control unit 300 sets the active state of the line interfaces 201 to 208 by notifying the line control unit 231 of each line interface of the selected line interface. Further, the control unit 300 generates "line activation request information" in fig. 5 based on the selection result of the line interface to be activated, and notifies each line control unit 231 (step S04). Further, the control unit 300 instructs the switch 400 to distribute the client signal based on the active states of the line interfaces 201 to 208 (step S05).

(b3) The control unit 300 acquires the processing state of the received signal processing unit 241 from each line control section 231 of the line interfaces 201 to 208 (step S06). When the DSP221 is in an inactive state or the received signals are not synchronized, the received signal processing unit 241 is determined to be in an inactive state (inactive). When the DSP221 of the line interface is active and the client signal is normally demodulated, the received signal processing unit 241 is determined to be in an active state (active) (step S07). The control unit 300 generates line activity state information of the line interfaces 201 to 208 shown in fig. 6 according to the determination result thereof, and notifies the line control unit 231 (step S08).

(b4) The control unit 300 acquires the "line activation request information" for the repeater of the terminal station 1001 notified from the terminal station 1002 from the line control unit 231 (step S09). For the line interface of the terminal station 1001 set in the inactive state, it is checked whether a request for setting in the active state is received from the terminal station 1002 (step S10). When the activation is requested (step S10: YES), the control unit 300 of the terminal station 1001 cancels the inactive state of the requested line interface and sets the line interface to the active state (step S11). Further, with respect to the line interface determined to be in the inactive state in step S07, it is checked whether a request for setting to the inactive state is issued from the terminal station 1002 (step S12). When a request for setting to the inactive state is issued, the line interface is set to the inactive state (step S13). Here, when a deactivation request for the purpose of the line interface being in an active state for transmitting the client signal is notified from the opposite station, the line interface remains in the active state to continue transmitting the client signal.

When the active state of the line interface is changed in step S11 or S13, the control unit 300 connects the line interfaces 201 to 208 with the client interfaces 101 to 110 based on the latest active state. Note that, when the received "line activation request information" includes information on the port setting of the switch 400, the control unit 300 may set the connection between the ports of the switch 400 based on the information. When the switch 400 cannot be operated with the received settings, an alarm indicating the effect may be returned to the opposite station. The control unit 300 repeats the above-described process.

(c) Operation of the exchanger 400

(c1) The switch 400 of the terminal station 1001 connects between the client interfaces 101 to 110 and the line interfaces according to the instruction of the control unit 300, so that the client signal received from each of the client interfaces 101 to 110 is dispersed to the line interface in the active state. Switch 400 may distribute client signals of one client device to a plurality of line interfaces. A line interface processes client signals received from a plurality of client interfaces within a processable bandwidth. Further, the switch 400 distributes and outputs the client signals received from the line interfaces 201 to 208 to the client interfaces 101 to 110. The switch 400 can distribute the received client signal to the any one of the client interfaces 101 to 110 by using a port-based VLAN, and the client device 30 at its destination is connected to the any one of the client interfaces 101 to 110.

(c2) The switch 400 monitors the bandwidth (traffic) of the client signal input from each of the client interfaces 101 to 110. Upon request from the control unit 300, the switch 400 notifies the control unit 300 of the traffic of each of the client interfaces 101 to 110.

(d) Operation of line control unit 231

(d1) Upon an instruction from the control unit 300, the line control unit 231 of the terminal station 1001 sets an active state and an inactive state for the line interfaces 201 to 208 of the terminal station 1001.

(d2) The line control unit 231 of the terminal station 1001 acquires the "line activation request information" and the "line activity state information" generated by the control unit 300 of the terminal station 1001 from the control unit 300, and notifies the transmission signal processing unit 232.

(d3) The "line activation request information" and the "line active state information" generated by the terminal station 1002 are stored in an unused area of the FEC _ OH of the optical signal, and are notified to the terminal station 1001. After the instruction 300 from the control unit, the line control unit 231 of the terminal station 1001 acquires the "line activation request information" and the "line activity state information" notified from the terminal station 1002 from the received signal processing unit 241, and notifies the control unit 300.

(e. operation of the transmission signal processing unit 232)

(e1) When the line interface receives an instruction to set to the active state from the line control unit 231, the transmission signal processing unit 232 returns the DSP221 from the inactive state. Then, the output of the transmission signal processing unit 232 is changed from the dummy mode to the output of the DSP221 (i.e., the client signal-processed by the DSP 221). In contrast, when the line interface receives an instruction to set the inactive state, the transmission signal processing unit 232 makes the DSP221 transition to the inactive state, and switches the output of the transmission signal processing unit 232 to the dummy mode generated by the dummy mode generation unit 251.

(e2) The transmission signal processing unit 232 of the terminal station 1001 stores "line activation request information" and "line activity state information" of the terminal station 1001 notified from the line control unit 231 in the unused area of FEC _ OH. For example, the header processing unit 252 stores "line activation request information" and "line activity state information" in an unused area of FEC _ OH of the signal-processed client signal. The stored pieces of information are transmitted to the terminal station 1002.

(f. operation of the received signal processing unit 241)

(f1) When the line interface receives an instruction to set to the active state from the line control unit 231, the received signal processing unit 241 returns the DSP221 from the inactive state, and restarts the process of outputting the client signal to the switch 400. When the line interface receives an instruction to set to the inactive state, the received signal processing unit 241 transitions the DSP221 to the inactive state and stops the processing of the received signal processing unit 241.

(f2) Upon an instruction from the line control unit 231, the received signal processing unit 241 notifies the line control unit 231 of "line activation request information" and "line activity state information" extracted from the unused area of FEC _ OH of the received signal and notified from the opposite station.

Fig. 8 illustrates an example of a change in the number of line interfaces in an active state when the total bandwidth of client signals received by the client interfaces 101 to 110 included in the terminal station 1001 from the client device 30 changes over time. The vertical axis of fig. 8 indicates the total bandwidth of the client signal, and the horizontal axis indicates time. The right side a to D of fig. 8 indicates an upper limit of the total bandwidth of the client signals that the line interfaces 201 to 208 can process according to the number of line interfaces in the active state. A indicates the upper bandwidth limit when only one line interface is active. Similarly, B, C, D indicates the upper bandwidth limit when 2, 3, and 4 line interfaces are active, respectively. The vertical axis indicates the relative relationship of the bandwidths and does not indicate the absolute values of the bandwidths. Further, in fig. 8, it is assumed that the line interfaces 201 to 208 have the same performance and can each handle the same bandwidth.

In fig. 8, the number of line interfaces to be in an active state is indicated next to "the number of line interfaces to be activated". The number indicates the number of line interfaces activated according to a change in the total bandwidth of the client signal received by the terminal station 1001 from the client device 30. For example, when the bandwidth of the client signal is equal to or less than a, at least one line interface needs to be set to an active state. Further, when the bandwidth of the client signal is greater than B but not greater than C, at least three line interfaces need to be set to the active state.

In fig. 8, there is no hysteresis in bandwidth at the threshold for switching the number of line interfaces to be set to the active state. However, to reduce the frequency of increasing and decreasing the number of active line interfaces, hysteresis may be given as follows.

(1) When the total unused bandwidth of the bandwidths that can be processed by the line interface in the active state is less than 20% of the bandwidth of one line interface, one line interface to be set in the active state is added.

(2) One line interface in the active state is subtracted when the total unused bandwidth of the bandwidth that can be handled by the line interface in the active state exceeds 150% of the bandwidth of one line interface.

Fig. 9 is a diagram showing an example of a spectrum of an optical signal transmitted by the terminal station 1001. In the figure, the horizontal axis represents wavelength and the vertical axis represents intensity of an optical signal. Fig. 9 (a) is an example of a spectrum of a WDM signal transmitted from the end station 1001 to the end station 1002 when the line interfaces 201 to 208 (lines (1) to (8) in fig. 9) are in an active state. Optical signals output from the lines (1) to (4) (line interfaces 201 to 204) are arranged on the long wavelength side, and optical signals output from the lines (5) to (8) (line interfaces 205 to 208) are arranged on the short wavelength side. Further, the dummy light is transmitted in a wavelength band between these optical signals. The dummy light is light generated by the dummy light source 50 shown in fig. 1 and is used to compensate for the gain tilt of the optical amplifier.

Fig. 9 (B) is an example of a spectrum of an optical signal transmitted from the terminal station 1001 to the terminal station 1002 when the lines (1) to (4) are active and the lines (5) to (8) are inactive. The optical signal on the long wavelength side is an optical signal output from the lines (1) to (4), and transmits a client signal. On the other hand, the optical signal on the short wavelength side is an optical signal modulated by the dummy signal generated by the dummy pattern generation unit 251 in the lines (5) to (8) of the terminal station 1001. In this way, even if some of the line interfaces 201 to 208 are inactive, the terminal station 1001 transmits an optical signal modulated with a dummy signal. Therefore, in (B) in fig. 9, the wavelength characteristic of the optical amplifier is not changed as compared with (a) in fig. 9. Therefore, when the bandwidth of the client signal is small, some line interfaces are deactivated and power consumption of the terminal stations 1001 and 1002 is reduced, while it is possible to prevent a change in the spectral profile of the optical signal being transmitted. As a result, a variation in the transmission quality of the optical signal associated with a variation in the bandwidth of the client signal can be prevented.

Fig. 9 (C) is an example of the spectrum of the WDM signal when the inactive line interface (lines (5) to (8)) does not output an optical signal. The optical repeaters in the undersea cable 40 operate so as to maintain the total power of the optical signals being transmitted. Therefore, in (C) of fig. 9, a change in the gain tilt of the transmission line may cause a change in the transmission quality of the WDM signal, particularly in long-distance transmission using an optical repeater.

According to the present exemplary embodiment, the optical carrier modulated with the dummy pattern maintains the profile (profile) of the optical signal similarly to the transmission of the client signal. For example, the dummy signal is set so that the modulated optical signal has the same optical output and the same transmission speed as when the client signal is transmitted. Patent document 1 describes that a monitoring signal or monitoring light is transmitted to a transmission line in an interface from which an L1 link is deleted. However, since the monitor signal in patent document 1 is a low-speed signal and the monitor light is a continuous light, the profile of the optical signal before the link deletion cannot be maintained. Therefore, the configuration in PTL1 may deteriorate the transmission quality of the WDM signal associated with link drop.

In this way, the repeater 11 can prevent the influence on the optical signal transmission quality due to the increase and decrease in the client signal bandwidth while reducing the power consumption of the line interfaces 201 to 208. An optical signal modulated with the dummy signal is output from the inactive line interface and the profile of the optical signal is maintained.

Further, when any one of the line interfaces 201 to 208 fails, the repeater 11 may deactivate the failed line interface and may activate another inactive line interface. Thereby, a redundant configuration of line interfaces can be achieved, improving the reliability of the submarine cable system 1000.

(third exemplary embodiment)

Fig. 10 is a block diagram illustrating a configuration example of a submarine cable system 2000 according to a third exemplary embodiment of the present invention. In the submarine optical cable system 2000, two optical transmission lines 41 and 42 exist between the opposite end stations 2001 and 2002, and four line interfaces are connected opposite to each of the optical transmission lines 41 and 42, respectively. The optical transmission lines 41 and 42 include repeaters. The multiplexing/demultiplexing unit 21 multiplexes/demultiplexes the optical signals transmitted and received by the line interfaces 201 to 204, and the multiplexing/demultiplexing unit 22 multiplexes/demultiplexes the optical signals transmitted and received by the line interfaces 205 to 208.

The terminal stations 2001 and 2002 according to the present embodiment have line interfaces assigned to a plurality of paths, so that when one path fails, it is possible to continue transmitting a client signal by using a line interface connected to another path. For example, when the optical transmission line 41 fails, the control unit 300 of the terminal station 2001 changes the active states of the line interfaces 205 to 208 so that the bandwidths capable of further transmitting the client signals transmitted by the line interfaces 201 to 204 are ensured. Then, the control unit 300 changes the setting of the switch 400 and sets the line interfaces 201 to 204 to the inactive state.

The submarine optical cable system 2000 distributes the optical signals transmitted and received by the line interfaces 201 to 208 to the optical transmission line 41 and the optical transmission line 42. As a result, even in the case where one optical transmission line cannot communicate, the transmission of the client signal can be continued by increasing the number of active line interfaces connected to the other optical transmission line.

(fourth embodiment)

Fig. 11 is a block diagram illustrating a configuration example of the repeater 12 according to the fourth exemplary embodiment of the present invention. According to the present exemplary embodiment, specific bandwidths are set for the client interfaces 101 to 110 and the line interfaces 201 to 208. Hereinafter, a setting example of activation and deactivation of the line interfaces 201 to 208 in the repeater 12 will be described. A repeater 12 having the same configuration is provided in the opposite end stations 1001 and 1002 in place of the repeater 10 shown in fig. 1.

In fig. 11, the client interfaces 101 to 110 are 100 gigabit ethernet (GbE) interfaces each having a data transmission capacity of 100 gigabits per second (Gb/s). Line interfaces 201 and 202 each have 50Gb/s data transmission capability modulated by Binary Phase Shift Keying (BPSK). Both line interfaces 203 and 204 have a data transmission capacity of 100Gb/s by QPSK modulation. Line interfaces 205 and 206 each have a 150Gb/s data transmission capability over 8 quadrature amplitude modulation (8 QAM). Both line interfaces 207 and 208 have a data transmission capacity of 200Gb/s with 16QAM modulation. The polarization division multiplexing scheme can be used in combination in any modulation scheme.

Similar to the earlier described repeater 11, the repeater 12 comprises a switch 400 arranged between the client interfaces 101 to 110 and the line interfaces 201 to 208.

The control unit 300 selects the line interface to be set to the active state so that the total bandwidth that the line interface can handle is equal to or greater than the total bandwidth of the client signal. Further, by selecting the line interfaces such that the number of line interfaces to be set in the active state is minimized, the power consumption of all the line interfaces can be further reduced.

Fig. 12 is a diagram illustrating a selection example of a line interface to be activated in the repeater 12 in fig. 11. The curve represents the time variation of the total bandwidth of the client signal. The horizontal axis indicates time and bandwidth that can be handled by the line interface that is active at the time. The vertical axis indicates the total bandwidth of the client signal. The circle marks indicate the line interfaces 201 to 208 (lines (1) to (8)) that are set to the active state at that time.

The control unit 300 of the terminal station 1001 selects a line interface to be activated from among the line interfaces 201 to 208 based on the total bandwidth of the client signals acquired from the client interfaces 101 to 110. Then, the control unit 300 activates the selected line interface, and notifies the opposite station (terminal station 1002) of "line activation request information" based on the selection result. As a result, the line interface of the repeater 12 is also active in the end station 1002, and the configuration and bandwidth of the end station 1002 are similar to those in the end station 1001.

In fig. 12, first, the total bandwidth of the client signal exceeds 50G (50Gb/s), and therefore, the control unit 300 activates the line interface 205 (line (5)) having a bandwidth of 150G. Thereafter, as the total bandwidth of the client signal increases, the control unit 300 switches the line interface to be activated to the line (7) (total bandwidth 200Gb/s), to the line (1) + the line (7) (total bandwidth 250Gb/s), and to the line (3) + the line (7) (total bandwidth 300 Gb/s). Further, when the total bandwidth of the client signal exceeds 350G, the client interface can guarantee a bandwidth of 500Gb/s by activating the line (3), the line (7), and the line (8). By ensuring a capacity greater than the total bandwidth of the client signal via the client interface, it is possible to prevent the client interface bandwidth from being immediately strained when the total bandwidth of the client signal sharply increases.

In this way, by selecting the line interface to be set in the active state according to the total bandwidth of the client signal, the number of line interfaces to be activated can be reduced even when the bandwidth of the client signal increases. As a result, the power consumption of the repeater 12 can be reduced.

(fifth exemplary embodiment)

When different types of line interfaces are provided in the repeater 12 as in the fourth exemplary embodiment, the modulation scheme of the optical transceiver, the form of FEC, and the size of FEC _ OH may be changed for each line interface. In this way, the WDM signal can be transmitted by a more preferable scheme according to the total bandwidth and transmission quality of the client signal.

For example, for an optical signal in a wavelength band having good transmission characteristics, the wavelength interval of the WDM signal becomes narrow, the size of the FEC _ OH is reduced, and the data speed is set high. In this way, broadband client signals can be transmitted.

For optical signals in a waveband with poor transmission characteristics, the wavelength interval of WDM signals is widened, the interference between optical carriers is reduced, the FEC _ OH size is increased, and the data rate is set low, so that the fault tolerance is improved. In this way, the transmission quality of the client signal can be ensured.

Fig. 13 is a diagram illustrating one example of wavelength arrangement when line interfaces having different transmission schemes coexist. Fig. 13 illustrates a case where the transmission characteristic of the optical signal on the short wavelength side is relatively poor and the transmission characteristic of the optical signal on the long wavelength side is relatively good. And the line interface with the bandwidth of 50Gb/s transmits the client signals through BPSK modulation. The line interface with the bandwidth of 100Gb/s transmits the client signals through QPSK modulation. Similarly, a line interface with a 150Gb/s bandwidth and a line interface with a 200Gb/s bandwidth transmit client signals by 8QAM modulation and 16QAM modulation, respectively. The wavelength interval of each optical signal generated by the line interface with the bandwidth of 50G and the line interface with the bandwidth of 100G is wider than that of each optical signal generated by the line interface with the bandwidth of 150G and the line interface with the bandwidth of 200G. In this way, both high transmission quality and broadband transmission can be achieved by selecting a more suitable transmission scheme for each line interface.

Some or all of the functions described in each exemplary embodiment may be implemented by a program executed by a central processing unit or DSP221 included in the control unit 300 or the line control unit 231. The program is recorded on a fixed, non-transitory recording medium. As the recording medium, a semiconductor memory or a fixed disk device included in the transponder is used, but not limited thereto.

Furthermore, exemplary embodiments of the present invention may be described as, but not limited to, the following supplementary notes.

(supplementary notes 1)

An optical transponder, comprising:

a client interface that transmits and receives client signals;

a line interface, comprising: signal processing means for performing signal processing for transmitting a client signal by a digital coherent scheme; and an optical transceiver that performs conversion between the client signal and the optical signal; and

control means for controlling the activation of the signal processing means in dependence on the bandwidth of the client signal.

(supplementary notes 2)

The optical repeater according to supplementary note 1, wherein,

each of the plurality of line interfaces includes a signal processing device, and

the control device calculates the number of the plurality of active line interfaces according to the bandwidth of the client signal, and activates or deactivates each of the signal processing devices of the plurality of line interfaces according to the number of the plurality of active line interfaces.

(supplementary notes 3)

The optical repeater according to supplementary note 2, wherein the control means activates or deactivates each of the signal processing means of the plurality of line interfaces according to the bandwidth of the line interface.

(supplementary notes 4)

The optical repeater according to any one of supplementary notes 1 to 3, wherein,

the control means generates information on an active state and an inactive state of each of the signal processing means of the line interface, and information indicating activation and deactivation of the signal processing means included in the opposite station, and

the line interface transmits the generated information to the opposite station.

(supplementary notes 5)

The optical repeater according to any one of supplementary notes 1 to 4, wherein,

the line interface includes:

an optical transmission device for modulating an optical carrier in accordance with a client signal input to the optical repeater, generating a modulated optical carrier, and outputting the modulated optical carrier from the optical repeater; and

an optical receiving device for demodulating the optical signal input to the optical repeater and outputting the demodulated client signal from the optical repeater, and

each of the optical transmission device and the optical reception device includes a signal processing device.

(supplementary notes 6)

The optical repeater according to any one of supplementary notes 1 to 5, wherein,

the line interface further includes a dummy pattern generation unit that generates a dummy pattern,

when the signal processing means is inactive, the optical transceiver outputs an optical signal modulated with a pseudo pattern, and

the optical signal modulated with the dummy pattern includes an optical profile similar to the optical signal modulated with the client signal input to the optical transponder.

(supplementary notes 7)

The optical repeater according to any one of supplementary notes 1 to 6, further comprising a switch connected between the client interface and the line interface, wherein,

the switch connects between the client interface and the plurality of line interfaces to be activated according to the bandwidth of the client signal input to the optical repeater in response to an instruction of the control means.

(supplementary notes 8)

The optical repeater according to supplementary note 7, wherein,

the control device generates connection settings for the switch between the client signal and the line interface, and

the line interface sends the generated connection settings.

(supplementary notes 9)

The optical repeater according to supplementary note 7 or 8, wherein,

the connection between the client interface and the line interface at the switch is set by a port-based Virtual Local Area Network (VLAN).

(supplementary notes 10)

An end station device comprising the optical repeater according to any one of supplementary notes 1 to 9, and

multiplexing/demultiplexing means for wavelength-division multiplexing the optical signals output by the optical repeater and outputting the wavelength-division multiplexed optical signals to the transmission line, and separating the wavelength-division multiplexed optical signals input from the transmission line and outputting the separated wavelength-division multiplexed optical signals to the optical repeater.

(supplementary notes 11)

An optical transmission system comprising the terminal station device and the transmission line according to supplementary note 10, wherein,

two or more of the terminal station devices are communicably connected to each other via a transmission line.

(supplementary notes 12)

A method of controlling an optical repeater, comprising:

sending and receiving, by a client interface, a client signal;

performing, by a signal processing apparatus included in the line interface, signal processing for transmitting a client signal by a digital coherent scheme;

converting, by an optical transceiver included in the line interface, the client signal and the optical signal; and

the activation of the signal processing means is controlled by the control means in dependence of the bandwidth of the client signal.

(supplementary notes 13)

The method for controlling an optical repeater according to supplementary note 12, further comprising:

calculating, by the control means, a number of the plurality of active line interfaces according to a bandwidth of the client signal, and activating or deactivating each of the signal processing means of the plurality of line interfaces according to the number of the plurality of active line interfaces.

(supplementary notes 14)

The method of controlling an optical repeater according to supplementary note 13, further comprising:

each of the signal processing means of the plurality of line interfaces is activated or deactivated by the control means in dependence on the bandwidth of the line interface.

(supplementary notes 15)

The control method of an optical repeater according to any one of supplementary notes 12 to 14, further comprising:

generating, by the control means, information on an active state and an inactive state of each of the signal processing means of the line interface, and information indicating activation and deactivation of the signal processing means included in the opposite station; and

the generated information is transmitted to the opposite station by the line interface.

(supplementary notes 16)

The control method of an optical repeater according to any one of supplementary notes 12 to 15, further comprising:

modulating, by an optical transmission apparatus including a signal processing apparatus, an optical carrier in accordance with a client signal input to an optical repeater, generating a modulated optical carrier, and outputting the modulated optical carrier from the optical repeater; and

the optical signal input to the optical repeater is demodulated by an optical receiving apparatus including a signal processing apparatus, and the demodulated client signal is output from the optical repeater.

(supplementary notes 17)

The control method of an optical repeater according to any one of supplementary notes 12 to 16, further comprising:

outputting, by the optical transceiver, an optical signal modulated with a dummy pattern when the signal processing device is inactive, wherein,

the optical signal modulated with the dummy pattern includes an optical profile similar to the optical signal modulated with the client signal input to the optical transponder.

(supplementary notes 18)

The control method of an optical repeater according to any one of supplementary notes 12 to 17, further comprising:

by a switch connected between the client interface and the line interface,

in response to an instruction from the control device, connection is made between the client interface and the plurality of line interfaces to be activated in accordance with the bandwidth of the client signal input to the optical repeater.

(supplementary notes 19)

The method of controlling an optical repeater according to supplementary note 18, further comprising:

generating, by a control device, connection settings for an exchanger between a client signal and a line interface; and

the generated connection settings are sent by the line interface.

(supplementary notes 20)

The method of controlling an optical repeater according to supplementary note 18 or 19, further comprising,

the connection between the client interface and the line interface at the switch is set by a port-based Virtual Local Area Network (VLAN).

(supplementary notes 21)

A method of controlling an optical repeater, comprising:

performing, by a signal processing apparatus, signal processing for transmitting and receiving a client signal by a digital coherent scheme;

performing a conversion between the client signal and the optical signal; and

the activation of the signal processing means is controlled in dependence of the bandwidth of the client signal.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, the present invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. In each example embodiment, an example of applying the present invention to a submarine cable system has been described. However, the present invention can also be applied to terrestrial optical transmission systems.

Moreover, the configurations described in the example embodiments are not necessarily mutually exclusive. The functions and effects of the present invention can be achieved by combining the configurations of some or all of the above-described exemplary embodiments.

The present application is based on and claims priority from japanese patent application No. 2019-059075 filed on 26.3.2019, the disclosure of which is incorporated herein by reference in its entirety.

[ list of reference numerals ]

10 to 12 transponder

20 to 22 multiplexing/demultiplexing units

30 client device

40 submarine cable

41. 42 optical transmission line

50 pseudo light source

100 to 110 client interface

200 to 208 line interface

210 optical transceiver

220 signal processing unit

221 DSP

231 line control unit

232 transmit signal processing unit

233 optical modulator

234, 240 light source

235 polarization synthesizer

236, 237 optical amplifier

238 polarization separator

241 received signal processing unit

251 pseudo pattern generating unit

252 header processing unit

261 header processing unit

300 control unit

400 exchanger

1000, 2000 submarine cable system

1001. 1002 terminal station

2001. 2002 terminal station