Optical network system, control method, and program

Abstract

To provide an optical network system that suppresses degradation of signal quality caused by nonlinear distortion in optical transmission.SOLUTION: A transmitting device of an optical network system includes a first nonlinear distortion compensator. A receiving device of the optical network system includes a second nonlinear distortion compensator. An optical repeater of the optical network system includes a third nonlinear distortion compensator. A control device controls the transmitting device, the receiving device, and the optical repeater.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to an optical network system, a control method, and a program.

Background Art

[0002] In recent years, the introduction of 5G wireless communication systems has been progressing. For the post-5G era, there is an increasing demand not only for wireless communication but also for optical communication in terms of large-capacity communication, ultra-high speed, ultra-low latency, and multiple simultaneous connections. Therefore, regarding optical communication systems, research is being carried out with the expectation of utilization in various communication services and industrial applications.

[0003] For example, in backbone optical communication systems, by using a digital coherent method that combines an optical phase modulation method and polarization multiplexing separation technology, a large capacity exceeding 100 Gbps (Giga bit per second) has been achieved. Furthermore, research and development of a transmission method that improves frequency utilization efficiency and enables multiple simultaneous connections by narrowing the signal band and performing wavelength division multiplexing (WDM) are also being conducted. In addition, research and development on distortion compensation technology that compensates for signal distortion generated during optical transmission, which hinders large-capacity communication due to high baud rate and high multi-level signal modulation in optical communication systems, are also being carried out by optical processing or digital signal processing.

[0004] As a related technology, for example, Patent Document 1 is known. Patent Document 1 discloses connecting an optical phase conjugate device that generates a phase conjugate signal by digital signal processing between a transmission device and a reception device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the technologies related to optical network systems as described above, it is required to suppress the deterioration of signal quality due to non - linear distortion in optical transmission.

[0007] An object of the present disclosure is to provide an optical network system, a control method, and a program for solving the above - described problems.

Means for Solving the Problems

[0008] An optical network system according to an aspect of the present disclosure includes a transmission device including a first non - linear distortion compensation unit, a reception device including a second non - linear distortion compensation unit, one or more optical relay devices having a third non - linear distortion compensation unit, an optical transmission path connecting the transmission device, the optical relay device, and the reception device, and a control device for controlling the transmission device, the reception device, and the optical relay device.

[0009] An information processing method according to an aspect of the present disclosure is such that a control device of an optical network system including a transmission device including a first non - linear distortion compensation unit, a reception device including a second non - linear distortion compensation unit, one or more optical relay devices having a third non - linear distortion compensation unit, an optical transmission path connecting the transmission device, the optical relay device, and the reception device, and a control device for controlling the transmission device, the reception device, and the optical relay device determines a distortion compensation section of the optical relay device, notifies at least one of the transmission device or the reception device of non - linear distortion compensation information to be used for non - linear distortion compensation in a transmission path outside the distortion compensation section of the optical relay device, at least one of the transmission device or the reception device generates and transmits a signal obtained by performing non - linear distortion compensation based on the non - linear distortion compensation information, and the optical relay device performs non - linear distortion compensation based on the non - linear distortion compensation information.

[0010] A program according to an aspect of the present disclosure includes a transmission device having a first non-linear distortion compensation unit, a reception device having a second non-linear distortion compensation unit, one or more optical relay devices having a third non-linear distortion compensation unit, an optical transmission path connecting the transmission device, the optical relay device, and the reception device, and a control device that controls the transmission device, the reception device, and the optical relay device. The control device of the optical network system determines a distortion compensation section of the optical relay device and executes a process of notifying at least one of the transmission device or the reception device of non-linear distortion compensation information used for non-linear distortion compensation in a transmission path outside the distortion compensation section of the optical relay device.

Effect of the Invention

[0011] According to the present disclosure, it is possible to suppress deterioration of signal quality due to non-linear distortion in optical transmission.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the optical network system, control method, control program, control device, and optical relay device of this disclosure will be described with reference to the drawings. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations are omitted as necessary. Note that the arrows in the configuration diagram (block diagram) are for illustrative purposes only and do not limit the type or direction of signals.

[0014] (Considerations Leading to the Embodiment) FIG. 1 shows the configuration of an optical network system according to a basic example that is the basis of this embodiment. The optical network system 1 according to the basic example is, for example, a backbone wavelength division multiplexing optical transmission system. The devices constituting the system perform wavelength division multiplexing of optical signals and perform high-order modulation and digital coherent transmission with optical signals of each wavelength to perform large-capacity communication exceeding 100 Gbps. By means of high-density wavelength division multiplexing, it is possible to improve the frequency utilization efficiency of light and cope with mobile traffic and wavelength defragmentation.

[0015] The optical network system 1 includes an optical relay device 200 (for example, 2-1 to 2-10) that can flexibly switch the transmission path (wavelength path or optical transmission path) while maintaining the optical signal in order to cope with switching of the transmission path in case of a failure and local traffic demands (for example, traffic demands from the networks of data centers 4 and 5, the network of IT service provider 6, and the networks of event venues 7 and 8). By including the optical relay device 200 (for example, 2-1 to 2-10), the optical network system 1 can maintain communication using optical signals as infrastructure.

[0016] The optical relay device 200 is a photonic node capable of relaying wavelength-division multiplexed optical signals, and is, for example, a ROADM (Reconfigurable Optical Add / Drop Multiplexer) device. Each optical relay device 200 is assigned a wavelength path (simply referred to as a path), and transfers the traffic of a local network or another optical relay device 200 accommodated via an optical communication cable that passes the optical signal of the assigned wavelength path to a destination network or another communication device.

[0017] FIG. 2 shows a configuration example of the optical relay device 200 according to the basic example. The optical relay device 200 branches / inserts an optical wavelength-division multiplexed signal and coherently demodulates / modulates the signals of each wavelength to be branched / inserted. As shown in FIG. 2, the optical relay device 200 includes an optical switch unit 300 and a transceiver unit 310.

[0018] The optical switch unit 300 transfers the optical signal of a predetermined wavelength path received from the preceding optical relay device 200 in the optical network system 1 to the succeeding optical relay device 200, and branches / inserts the received optical signal for each wavelength. For example, the optical switch unit 300 includes a demultiplexer 301, a multiplexer 302, and a branch / insertion unit 303. The demultiplexer 301 separates the optical signal received from the optical transmission line 3 into optical signals of a plurality of wavelengths. The multiplexer 302 multiplexes the optical signals of a plurality of wavelengths into one optical signal and transmits it to the optical transmission line 3. The branch / insertion unit 303 branches / inserts the optical signal of each wavelength between the demultiplexer 301 and the multiplexer 302.

[0019] The transceiver unit (transponder) 310 receives the optical signal of each wavelength branched from the branch / insertion unit 303 of the optical switch unit 300, and outputs the received data that has been coherently demodulated to a local device (network) that accommodates it. Further, the transceiver unit 310 inputs transmission data from the local device, and transmits (inserts) the optical signal of each wavelength that has been coherently modulated to the branch / insertion unit 303 of the optical switch unit 300. The transceiver unit 310 includes a plurality of optical transceivers 311 that transmit and receive the optical signal of each wavelength. The optical transceiver 311 receives the optical signal of a predetermined wavelength and further transmits the optical signal of a predetermined wavelength (the same as or different from the received wavelength) to a transmission destination.

[0020] Here, when using an optical transceiver as the optical transceiver 311, the problems that occur will be examined. FIG. 3 shows a configuration example of the optical transceiver according to this disclosure. As shown in FIG. 3, the optical transceiver 311 according to this disclosure includes a coherent reception front-end unit 210, a coherent transmission front-end unit 220, an acquisition unit 910, and a digital signal processing unit 901. In digital signal processing, phase conjugation processing on a channel-by-channel basis, chromatic dispersion compensation, and phase rotation processing are possible.

[0021] The coherent reception front-end unit 210 performs coherent detection on the optical signal received from the previous optical relay device 200 using local oscillation light (Local oscillator (LO) light) of a predetermined wavelength, and outputs the detected signal to the digital signal processing unit 901. The coherent transmission front-end unit 220 optically modulates (coherent modulation) the signal processed by the digital signal processing unit 901 to a predetermined wavelength, and transmits the generated optical signal to the next-stage optical relay device 200. The digital signal processing unit 901 is a DSP (Digital Signal Processor). It converts the signal coherently detected by the coherent reception front-end unit 210 into a digital signal, outputs the signal-processed received data, regenerates the input transmission data, and outputs the signal converted for optical modulation to the coherent transmission front-end unit 220. In this disclosure, in the digital signal processing unit 901, phase conjugation processing on a channel-by-channel basis, chromatic dispersion compensation, and phase rotation processing are performed.

[0022] Figures 4A and 4B show the amount of chromatic dispersion when using the optical relay device 200 including the optical transceiver 311 according to this disclosure. As shown in FIG. 4A, an optical relay device 200 is connected between a transmitting terminal device (transmitting end) 30 and a receiving terminal device (receiving end) 40 via optical transmission lines 3a and 3b. The optical transmission line 3a has a distance L1, and the optical transmission line 3b has a distance L2. L1 and L2 may be the same length or different lengths. An optical signal with a wavelength λ1 is transmitted through the optical transmission line 3a, and an optical signal with a wavelength λ2 is transmitted through the optical transmission line 3b. The optical transmission lines 3a and 3b illustrated in FIG. 4A are each composed of one transmission line section, but may be composed of multiple transmission line sections with signal amplification. Note that one transmission line section refers to the section of the transmission line between two network devices that are communicatively connected adjacent to each other, such as an optical relay device or an optical signal amplifier connected in a communication network.

[0023] In addition, in the configuration where the optical relay device 200 is connected to the path from the transmitting terminal device 30 to the receiving terminal device 40 as shown in FIG. 4A, the side of the transmitting terminal device 30 closer to the optical relay device 200 is referred to as the front stage (optical signal receiving side) of the optical relay device 200, and the side of the receiving terminal device 40 closer to the optical relay device 200 is referred to as the rear stage (optical signal transmitting side) of the optical relay device. Also, the optical transmission line between the optical relay device 200 and the transmitting terminal device 30 may be referred to as the front-stage (first part) optical transmission line, and the optical transmission line between the optical relay device 200 and the receiving terminal device 40 may be referred to as the rear-stage (second part) optical transmission line.

[0024] As shown in FIG. 4B, the amount of wavelength dispersion increases in proportion to the distance of the optical transmission line. For this reason, when the optical relay device 200 relays an optical signal only by simple signal amplification, the amount of wavelength dispersion continues to increase according to the distance from the transmitting end station device 30 to the receiving end station device 40. Then, as the distance of the optical transmission line becomes longer, the quality of the optical signal received by the receiving end station device 40 deteriorates significantly. In addition to wavelength dispersion, the quality of the optical signal also deteriorates significantly due to nonlinear distortion. Nonlinear distortion is a phenomenon in which the refractive index in a substance changes in proportion to the optical signal intensity and the phase of the light itself changes when an optical signal propagates through an optical fiber. Such nonlinear distortion has become a factor limiting high-capacity and long-distance transmission due to high bit rates and high multi-valuedness of optical signals.

[0025] In the example of the above disclosure, in the optical relay device 200 connected to the path from the transmitting end station device 30 to the receiving end station device 40, when the optical relay device 200 receives an optical signal composed of one or more optical channels, phase conjugation processing and equivalent digital signal processing for wavelength dispersion compensation are performed for each received channel. In the example of the above disclosure, in the optical relay device 200, by performing phase conjugation processing and wavelength dispersion compensation, the nonlinear distortion generated in the previous transmission line and the nonlinear distortion generated in the subsequent transmission line in the phase-conjugated light transmitted from the optical relay device 200 cancel each other out, and the influence of the nonlinear distortion on the receiving end station device 40, which is the receiving end, can be mitigated.

[0026] In the example of the above disclosure, when the optical relay device 200 is located between the transmitting end station device 30 and the receiving end station device 40, that is, when the distance L1 of the optical transmission path 3a between the transmitting end station device 30 (transmitting device) and the optical relay device 200 is equal to the distance L2 of the optical transmission path 3b between the optical relay device 200 and the receiving end station device 40 (receiving device), the non-linear distortion range by the relay device extends over the entire transmission path, and the non-linear distortion can be most alleviated. Since the position of the optical relay device 200 in the actual optical network system 1 is arbitrarily arranged, it is desirable to be able to sufficiently obtain the non-linear distortion compensation effect even when the optical relay device 200 is not located between the transmitting end station device 30 and the receiving end station device 40. In the present disclosure, by using the optical relay device 200, the transmitting end station device 30 including the non-linear compensation unit 34, the receiving end station device 40 including the non-linear compensation unit 44, and the control device 10 including the management unit that controls the non-linear compensations 34 and 44, it is possible to alleviate the non-linear distortion of the signal in the transmission path even when the optical relay device 200 is not located between the transmitting end station device 30 and the receiving end station device 40.

[0027] The outline of this embodiment is shown. An optical network system 1 is shown, which includes a transmitting end station device 30 including a non-linear compensation unit 34, one or more optical relay devices 200 having a non-linear compensation unit, a receiving end station device 40 including a non-linear compensation unit 44, an optical transmission path connecting them, and a control device 10 including a management unit that controls the non-linear compensations 34 and 44. Note that processing units similar to the non-linear compensation units 34 and 44 may be provided in the transmitting device and the receiving device that constitute the optical network system and are located sandwiching the optical relay device 200. The transmitting device and the receiving device may be the optical signal amplifiers 50 provided in the transmission path. In the embodiment of the present disclosure, an optical relay device having a non-linear distortion compensation unit that performs phase conjugation and wavelength dispersion compensation processing is shown. That is, the non-linear distortion compensation processing in the optical relay device 200 of the present disclosure is to perform phase conjugation processing and wavelength dispersion compensation processing. Similarly, non-linear distortion compensation processing can be performed with an optical relay device configuration that performs phase rotation processing.

[0028] (Outline of the embodiment) FIG. 5 shows the schematic configuration of the control device according to the present embodiment. FIG. 6 shows the schematic configuration of the transmission end station device according to the present embodiment. FIG. 7 shows the schematic configuration of the reception end station device according to the present embodiment. FIG. 8 is a conceptual diagram showing a specific example of the non-linear compensation unit according to the present embodiment. FIG. 9 shows the schematic configuration of the optical relay device according to the present embodiment.

[0029] The control device 10, the optical transmitter 30, the optical relay device 200, and the optical receiver 40 constitute the optical network system 1. The transmission end station device 30 according to the present embodiment constitutes a part of the optical network system 1, the optical relay device 200 according to the present embodiment constitutes a part of the optical network system 1, the reception end station device 40 according to the present embodiment constitutes a part of the optical network system 1, and the control device 10 according to the present embodiment controls the transmission end station device 30, the optical relay device 200, and the reception end station device 40, which are other components in the optical network system 1.

[0030] As shown in FIG. 5, the control device 10 includes a management unit 11, a phase conjugation control unit 12, a chromatic dispersion compensation control unit 13, a distortion compensation section determination unit 14, and a distortion compensation control unit 15. The management unit 11 manages the transmission line information of the optical transmission line connected to one or more optical relay devices 200 in the path of the optical network, and the carrier frequency (wavelength) of each channel of the optical signal composed of one or more signal channels received by the optical relay device 200. The phase conjugation control unit 12 determines the phase conjugation process in the optical relay device 200 based on the transmission line information and the carrier frequency information managed by the management unit 11. The chromatic dispersion compensation control unit 13 determines the chromatic dispersion compensation amount to be compensated in the optical relay device 200 based on the transmission line information and the carrier frequency managed by the management unit 11. The distortion compensation section determination unit 14 determines the distortion compensation section, which is the transmission line for which the optical relay device in the transmission line of the optical network system 1 performs non-linear distortion compensation. The distortion compensation control unit 15 controls the non-linear distortion compensation processes of the transmission end station device 30 and the reception end station device 40 based on the information on the distortion compensation section determined by the distortion compensation section determination unit 14. Note that the non-linear distortion compensation or the non-linear distortion compensation process may be simply described as the distortion compensation process or the compensation process.

[0031] As shown in Fig. 6, the transmitting end station device 30 (transmitting device) includes a data generation unit 31, a linear compensation unit 32, a non-linear compensation acquisition unit 33, a non-linear compensation unit 34, and a coherent transmission front-end unit 35. The non-linear compensation acquisition unit 33 acquires non-linear distortion compensation information determined by the distortion compensation control unit 15 from the control device 10 and used by the transmitting device. The non-linear compensation unit 34 performs non-linear distortion compensation processing based on the non-linear distortion compensation information acquired from the non-linear compensation acquisition unit 33. Although not shown in Fig. 6, the transmitting end station device 30 generates and multiplexes optical signals of a plurality of optical channels and transmits them as transmission signals to the transmission line.

[0032] As shown in Fig. 7, the receiving end station device 40 (receiving device) includes a data restoration unit 41, a linear compensation unit 42, a non-linear compensation acquisition unit 43, a non-linear compensation unit 44, and a coherent reception front-end unit 45. The non-linear compensation acquisition unit 43 acquires non-linear distortion compensation information determined by the distortion compensation control unit 15 from the control device 10 and used by the transmitting device. The non-linear compensation unit 44 performs non-linear distortion compensation processing based on the non-linear distortion compensation information acquired from the non-linear compensation acquisition unit 43. Although not shown in Fig. 7, the receiving end station device 40 receives and demultiplexes optical signals of a plurality of optical channels and performs signal processing on the optical signals of each channel.

[0033] As an example of non-linear distortion compensation processing, there is the digital back-propagation method (DBP). In the digital back-propagation method, non-linear waveform distortion in an optical fiber communication path is simulated by digital signal processing, and non-linear distortion compensation is realized by applying the reverse action of non-linear waveform distortion to transmission or reception data.

[0034] As shown in Fig. 8, the non-linear compensation unit 34 included in the transmitting end station device 30 and the non-linear compensation unit 44 included in the receiving end station device 40 include a chromatic dispersion compensation unit 501 and a phase rotation compensation unit 502. In the digital backpropagation method, a chromatic dispersion compensation unit 501 (corresponding to the chromatic dispersion compensation unit 231 in Fig. 13) composed of a fast Fourier transform (FFT), frequency response multiplication based on the chromatic dispersion compensation amount compensated by the step, and an inverse fast Fourier transform (IFFT), and a phase rotation compensation 502 that performs phase rotation of the symbol based on non-linear distortion compensation information composed of inter-symbol information (number of taps and inter-symbol weight coefficients) between the symbol and the symbols before and after the symbol and a fixed coefficient (non-linear coefficient) in the time domain. One step consists of K (K is an integer of 1 or more) consecutive steps. The non-linear distortion compensation information may be determined for each step. The chromatic dispersion compensation unit 501 and the phase rotation compensation unit 502 perform non-linear distortion compensation on the signal based on the information acquired from the non-linear compensation acquisition unit 33 or 43. The non-linear distortion compensation information described above in the description of Fig. 6 includes, for example, the number of steps used in the non-linear distortion compensation process composed of the non-linear compensation units 34 and 44 shown in Fig. 8, the chromatic dispersion amount in the chromatic dispersion compensation unit 501 in each step, the number of taps and inter-symbol weight coefficients related to the phase rotation compensation unit 502, and non-linear parameters.

[0035] As shown in Fig. 9, the optical relay device 200 includes a coherent reception front-end unit 21, a phase conjugation unit 22, a chromatic dispersion compensation unit 23, a coherent transmission front-end unit 24, a phase conjugation acquisition unit 25, and a chromatic dispersion compensation acquisition unit 26. Although not shown in Fig. 9, it transmits and receives a plurality of optical channels and performs phase conjugation and chromatic dispersion compensation on the signals of each channel.

[0036] Returning to the description of FIG. 5, the phase conjugate acquisition unit 25 acquires the phase conjugate processing information determined by the phase conjugate control unit 12 of the control device 10. The wavelength dispersion compensation acquisition unit 26 acquires the wavelength dispersion compensation amount determined by the wavelength dispersion compensation control unit 13 of the control device 10. The coherent reception front-end unit 21 performs coherent detection on the received optical signal based on the local light emission of the received carrier frequency acquired from the management unit 11, and outputs the electrically-signal obtained by the coherent detection. The phase conjugate unit 22 performs phase conjugate processing on the electrical signal output from the coherent reception front-end unit 21 by digital signal processing based on the phase conjugate processing setting acquired by the phase conjugate acquisition unit 25. The wavelength dispersion compensation unit 23 performs wavelength dispersion compensation processing on the electrical signal output from the phase conjugate unit 22 by digital signal processing based on the wavelength dispersion compensation amount acquired by the wavelength dispersion compensation acquisition unit 26. The coherent transmission front-end unit 24 performs coherent modulation on the electrical signal subjected to phase conjugate processing by the phase conjugate unit 22 and the electrical signal subjected to wavelength dispersion compensation processing by the wavelength dispersion compensation unit 23 based on the local light emission of the transmission carrier frequency acquired from the management unit 11, and transmits the coherently-modulated optical signal.

[0037] By performing phase conjugation of the optical signal in the optical relay device 200, it is possible to invert the distortion of the optical signal in the optical transmission path in the front stage of the optical relay device 200. As the signal propagates through the optical transmission path in the rear stage of the optical relay device 200, the distortion is reproduced in reverse, and the distortion is canceled on the receiving end (such as the receiving end station device 40) side. According to the embodiments shown below, in the optical relay device 200, wavelength dispersion compensation can be performed with appropriate phase conjugation and wavelength dispersion compensation amount. Therefore, in a multi-transmission path section optical network, it is possible to maximize the cancellation effect of non-linear distortion by multi-span optical transmission by using phase conjugation and wavelength dispersion compensation in each optical relay device 200, and effectively suppress the degradation of signal quality due to non-linear distortion at the receiving end of the optical network.

[0038] In the non - linear distortion compensation using phase conjugation and wavelength dispersion compensation with distortion cancellation by the optical relay device 200, if the optical relay device 200 is not located at the center of the transmission line between the transmitting end - station device 30 and the receiving end - station device 40, there exists a section that the optical relay device 200 cannot compensate. Therefore, the control unit 10 determines a distortion compensation section, which is the transmission line for which the optical relay device 200 performs non - linear distortion compensation. For other transmission lines (outside the distortion compensation section) that are not the transmission lines for which the optical relay device 200 performs non - linear distortion compensation (sections that the optical relay device 200 cannot compensate), the transmitting end - station device 30 or the receiving end - station device 40 performs non - linear distortion compensation based on the non - linear distortion compensation information used by the transmitting end - station device 30 and the receiving end - station device 40 determined by the control unit 10. Thereby, regardless of the position of the optical relay device 200 on the transmission line between the transmitting end - station device 30 and the receiving end - station device 40, it becomes possible to effectively reduce non - linear distortion.

[0039] As described above, in the present embodiment, the control device 10 determines the wavelength information of the optical signal transmitted and received by the optical relay device 200, the signal band information, and the transmission line information of the optical transmission line connected to the optical relay device 200 in the transmission line between the transmitting end - station device 30 and the receiving end - station device 40, and determines the phase conjugation process and the wavelength dispersion compensation amount in the optical relay device 200. The control device 10 performs wavelength dispersion compensation of the determined phase conjugation process and wavelength dispersion compensation amount for non - linear distortion compensation in the optical relay device 200. The control device 10 determines the distortion compensation section of the optical relay device based on the transmission line information of the optical transmission line connected to the optical relay device 200 and the position information of the optical relay device. The control device 10 determines the non - linear distortion compensation information used by the transmitting end - station device 30 and the receiving end - station device 40 for non - linear distortion compensation processing based on the distortion compensation section of the optical relay device 200. The control device 10 notifies the transmitting end - station device 30 or the receiving end - station device 40 of the non - linear distortion compensation information used by the transmitting end - station device 30 and the receiving end - station device 40. The control device 10 performs non - linear distortion compensation in at least one of the transmitting end - station device 30 or the receiving end - station device 40 based on the non - linear distortion compensation information notified from the control device 10. As described above, the non - linear distortion compensation performed by the optical relay device 200 includes a phase conjugation process and a wavelength dispersion compensation process. Also, the non - linear distortion compensation performed by the transmitting end - station device 30 or the receiving end - station device 40 includes signal processing by the digital back - propagation method.

[0040] (Embodiment 1) Next, Embodiment 1 will be described with reference to the drawings. FIG. 10 shows a configuration example of an optical network system 1 according to an embodiment of the present disclosure. As shown in FIG. 10, an optical network system 1 according to an embodiment of the present disclosure includes a control device 100, an optical relay device 200, a transmitting end station device 30, and a receiving end station device 40. Although FIG. 10 shows a case where there is one optical relay device 200 in Embodiment 1, the same applies when a plurality of optical relay devices 200 exist between the transmitting end station device 30 and the receiving end station device 40 of the optical network system 1.

[0041] The optical relay device 200, the transmitting end station device 30, and the receiving end station device 40 are connected so as to be able to perform optical communication via an optical transmission line 3. The optical relay device 200, the transmitting end station device 30, and the receiving end station device 40 are communicably connected to the control device 100 by a control signal. The optical relay device 200, the transmitting end station device 30, and the receiving end station device 40 may be connected to the control device 100 via the optical transmission line 3, or may be communicably connected by any other transmission line including wired and wireless.

[0042] The optical relay device 200, the transmitting end station device 30, and the receiving end station device 40 are optical transmission devices (optical nodes) that perform optical communication via the optical transmission line 3. The transmitting end station device 30 constitutes a transmitting end in a path configured by connecting a plurality of optical transmission lines 3. The receiving end station device 40 constitutes a receiving end in a path configured by connecting a plurality of optical transmission lines 3. The transmitting end station device 30 transmits, in the same manner as in the basic example, a multi-channel optical signal wavelength-division multiplexed by the wavelength of the path set by the control device 100 to the receiving end station device 40 via the optical transmission line 3. The receiving end station device 40 receives, in the same manner as in the basic example, a multi-channel optical signal wavelength-division multiplexed by the wavelength of the path set by the control device 100 from the transmitting end station device 30 via the optical transmission line 3.

[0043] The optical relay device 200 is a relay device capable of relaying wavelength-division multiplexed multi-channel optical signals, similar to the basic example. The optical relay device 200 constitutes an optical network 51 that performs WDM communication. It can also be said that the optical relay device 200, together with the transmitting terminal device 30 and the receiving terminal device 40, constitutes the optical network 51. Similar to FIG. 1, the optical network 51 is a wavelength-division multiplexed optical network. The optical network 51 may be a mesh-shaped network, a ring-shaped network, a Point-to-Point network, or a network of other topologies. Also, the optical relay device 200 configures a path from the transmitting terminal device 30 to the receiving terminal device 40 in response to control from the control device 100, and transmits an optical signal (data) according to the wavelength set on the path of the path.

[0044] The control device 100 manages and controls the optical network 51 including the optical relay device 200. For example, the control device 100 is an NMS (Network Management System) that manages the network.

[0045] The control device 100 manages and controls the path configured by the optical relay device 200 in the optical network 51. The control device 100 manages the path and wavelength of the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the path, wavelength, etc. for the transmitting terminal device 30, the receiving terminal device 40, and the optical relay device 200 on the path.

[0046] FIG. 11 shows a configuration example of the control device 100 in an optical network system according to an embodiment of the present disclosure. As shown in FIG. 11, the control device 100 includes a network management unit 110, a network control unit 120, a wavelength dispersion compensation amount calculation unit 130, a phase conjugation determination unit 140, a distortion compensation section determination unit 150, and a distortion compensation control unit 160.

[0047] The network management unit 110 corresponds to the management unit 11 shown in FIG. 5, and manages information necessary for network management, such as network configuration information, path configuration information, and location information of the optical relay device 200 in the optical network 51. For example, the network management unit 110 may be configured by a database that stores information necessary for network management. The network configuration information includes the connection relationships of the optical relay devices 200, the transmission end station devices 30, and the reception end station devices 40 that constitute the network, and the transmission path information of the optical transmission paths 3 that connect between the devices. The transmission path information includes the distance L (transmission path length) of the optical transmission path and the carrier frequency of each channel of the optical signal composed of a plurality of channels in the path, and may include the structure, type, transmission characteristics, etc. of the optical fiber. The path configuration information includes information on each device that constitutes the path, the wavelengths available for each device on the path, and the usage status of the wavelengths. These pieces of information may be set in the database in advance, may be set based on information collected from each device, and may further be updated by the network control unit 120 or the like.

[0048] The network control unit 120 corresponds to the management unit 11 shown in FIG. 5 and controls the paths in the optical network 51, the optical relay devices 200, the transmitting terminal device 30, and the receiving terminal device 40 that constitute the paths. The network control unit 120 refers to network configuration information, path configuration information, etc. in the network management unit 110, determines the path of the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the determined path in the transmitting terminal device 30, the receiving terminal device 40, and the optical relay device 200 on the path of the path. Further, the network control unit 120 determines the carrier frequency of each channel of the optical signal in the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the determined carrier frequency in the transmitting terminal device 30, the receiving terminal device 40, and the optical relay device 200 on the path of the path. The carrier frequency of the light in the path is determined for each optical transmission path in the path of the path. In addition, the network control unit 120 outputs information necessary for calculating the wavelength dispersion compensation amount in the optical relay device 200 that constitutes the path to the wavelength dispersion compensation amount calculation unit 130. For example, the network control unit 120 outputs the transmission path information of the front and rear optical transmission paths. Further, the network control unit 120 outputs the phase conjugation determination information in the optical relay device 200 that constitutes the path to the phase conjugation determination unit 140. For example, the network control unit 120 outputs the number of paths and the number of optical relay devices in the optical network 51.

[0049] The phase conjugation determination unit 140 corresponds to the phase conjugation control unit 12 shown in FIG. 5 and controls the phase conjugation process of the optical relay device 200 that constitutes the path. The phase conjugation determination unit 140 determines the optimal phase conjugation process for the optical relay device 200 based on the number of paths and the number of optical relay devices in the optical network 51, the position information of the optical relay device 200, etc. obtained from the network control unit 120. The phase conjugation determination unit 140 notifies the optical relay device 200 of the phase conjugation process information.

[0050] The wavelength dispersion compensation amount calculation unit 130 corresponds to the wavelength dispersion compensation control unit 13 shown in FIG. 5, and calculates the wavelength dispersion compensation amount for the optical relay device 200 constituting the path to perform wavelength dispersion compensation. The wavelength dispersion compensation amount calculation unit 130 is a compensation control unit that determines and controls the wavelength dispersion compensation amount of the optical relay device 200. The wavelength dispersion compensation amount calculation unit 130 determines the optimum wavelength dispersion compensation amount for the optical relay device 200 based on the received wavelength information, signal band, transmission wavelength information of the optical relay device 200 obtained from the network control unit 120, and the transmission path information before and after the optical relay device. The wavelength dispersion compensation amount calculation unit 130 notifies the corresponding optical relay device 200 of the received wavelength information, transmission wavelength information, and the optimum wavelength dispersion compensation amount of the optical relay device 200.

[0051] The distortion compensation section determination unit 150 corresponds to the distortion compensation section determination unit 14 shown in FIG. 5, and determines a non-linear distortion compensation section (distortion compensation section), which is the transmission path for performing non-linear distortion compensation implemented by the optical relay device 200 in the optical network 51.

[0052] FIG. 12A is a first diagram showing the concept of a distortion compensation section determination method determined by the distortion compensation section determination unit 150. Assume an optical network 51 composed of a transmission optical path connecting a transmitting end station device 30 and a receiving end station device 40, which consists of six transmission path sections (3A, 3B, 3C, 3D, 3E, 3F), five optical signal amplifiers 50 that respectively compensate for the transmission loss of one transmission path section, one optical relay device 200, the transmitting end station device 30, and the receiving end station device 40. As shown in FIG. 12A, the transmission paths in the optical network 51 are connected in the order of 3A, 3B, 3C, 3D, 3E, 3F. It is assumed that the lengths of each transmission path are approximately the same. Also, the optical relay device 200 is located in the second half from the center in the entire transmission path connecting the transmitting end station device 30 and the receiving end station device 40. For example, assume that the optical relay device 200 is located between the transmission paths 3D and 3E as shown in FIG. 12A. At this time, the optical relay device 200 performs non-linear distortion compensation so that no distortion occurs in the signal received by the receiving end station device 40, considering the non-linear distortion generated in the transmission path sections 3A, 3B, 3C, 3D and the non-linear distortion generated in the subsequent transmission paths 3E, 3F. However, although the details will be described later, the optical relay device 200 can perform non-linear distortion compensation so that no distortion occurs in the signal received by the receiving end station device 40 when it is located approximately in the center between the preceding transmission path and the subsequent transmission path. Therefore, among the transmission paths 3A, 3B, 3C, 3D, 3E, 3F, the transmission path sections 3C, 3D in the preceding stage and the transmission path sections 3E, 3F in the subsequent stage centered on the position of the optical relay device 200 are determined as the distortion compensation sections. That is, in this way, the distortion compensation section determination unit 150 determines the distortion compensation section of the optical relay device 200 as 3C to 3F, with the number of transmission path sections that cancel non-linear distortion in the first and second halves of the optical relay device 200 by phase conjugation being four transmission path sections. In this case, the distortion compensation section determination unit 150 determines that the sections of the transmission paths 3A and 3B that are not determined as the distortion compensation section of the optical relay device 200 are the distortion compensation sections of the transmitting end station device 30 close to those transmission paths.

[0053] FIG. 12B is a second diagram showing the concept of the distortion compensation section determination method determined by the distortion compensation section determination unit 150. Assume an optical network 51 composed of a transmission path connecting the transmitting end station device 30 and the receiving end station device 40, which consists of 6 transmission path sections (3A, 3B, 3C, 3D, 3E, 3F), five optical signal amplifiers 50 that compensate for the transmission loss of each transmission path section, one optical relay device 200, the transmitting end station device 30, and the receiving end station device 40. Also, as shown in FIG. 12B, the transmission paths in the optical network 51 are connected in the order of 3A, 3B, 3C, 3D, 3E, 3F. It is assumed that the lengths of each transmission path are approximately the same. Further, the optical relay device 200 is located in the first half from the center in the entire transmission path connecting the transmitting end station device 30 and the receiving end station device 40. For example, assume that the optical relay device 200 is located between the transmission paths 3B and 3C as shown in FIG. 12B. At this time, the optical relay device 200 performs non-linear distortion compensation so that no distortion occurs in the signal received by the receiving end station device 40 in consideration of the non-linear distortion generated in the transmission path sections 3A and 3B and the non-linear distortion generated in the subsequent transmission path sections 3C, 3D, 3E, and 3F. However, although the details will be described later, the optical relay device 200 can perform non-linear distortion compensation so that no distortion occurs in the signal received by the receiving end station device 40 when it is located approximately in the center of the previous transmission path and the subsequent transmission path. Therefore, among the transmission paths 3A, 3B, 3C, 3D, 3E, and 3F, the previous transmission path sections 3A and 3B and the subsequent transmission path sections 3C and 3D centered on the position of the optical relay device 200 are determined as the distortion compensation sections. That is, in this way, the distortion compensation section determination unit 150 determines the distortion compensation section of the optical relay device 200 as 3A to 3D with the number of transmission path sections in which the non-linear distortion cancels out in the first half and the second half of the optical relay device 200 by phase conjugation being 4 transmission path sections. In this case, the distortion compensation section determination unit 150 determines the sections of the transmission paths 3E and 3F that were not determined as the distortion compensation section of the optical relay device 200 as the distortion compensation section of the receiving end station device 40 close to those transmission paths.

[0054] The distortion compensation control unit 160 corresponds to the distortion compensation control unit 15 shown in FIG. 5, and controls the distortion compensation process of the transmitting end station device 30 or the receiving end station device 40 based on the information on the distortion compensation section of the optical relay device determined by the distortion compensation section determination unit 150.

[0055] In the case of the example of FIG. 12A, since the section outside the distortion compensation section of the optical relay device 200 exists in the first half of the entire transmission path, the non-linear distortion compensation information in the distortion compensation section of the transmission device is notified to the transmitting end station device 30 as the section (distortion compensation section of the transmitting end station device 30) in which the transmitting end station device 30 compensates for the transmission paths 3A and 3B, and the non-linear distortion compensation unit 34 is controlled.

[0056] In the case of the example of FIG. 12B, since the section outside the distortion compensation section of the optical relay device 200 exists in the second half of the entire transmission path, the non-linear distortion compensation information in the distortion compensation section of the receiving end station device 40 is notified to the receiving end station device 40 as the section (distortion compensation section of the receiving end station device 40) in which the receiving end station device 40 compensates for the transmission paths 3E and 3F, and the non-linear distortion compensation unit 44 is controlled.

[0057] In this way, by switching the non-linear compensation of the transmitting end station device 30 and the receiving end station device 40 according to the positional relationship of the distortion compensation section of the optical relay device 200, effective non-linear compensation becomes possible. Since the distortion compensation by the optical relay device 200 cannot completely compensate for the non-linear distortion generated in the transmission path, some non-linear distortion remains. For the signal with the remaining non-linear distortion, the effect of non-linear distortion compensation by the digital signals of the transmitting end station device 30 and the receiving end station device 40 is not sufficient. By switching the non-linear compensation of the transmitting end station device 30 and the receiving end station device 40 according to the positional relationship of the distortion compensation section of the optical relay device 200 as shown in the present embodiment, the non-linear distortion compensation of the transmitting end station device 30 and the receiving end station device 40 can be executed for a signal without residual non-linear distortion of phase conjugation, and the effect of non-linear distortion compensation can be fully exerted. As a result, it is possible to sufficiently maintain the effect of non-linear distortion compensation regardless of the position of the relay device.

[0058] FIG. 13 shows a configuration example of the optical relay device 200 in the optical network system according to an embodiment of the present disclosure. As shown in FIG. 13, an optical relay device 200 according to an embodiment of the present disclosure includes an optical transceiver 201 and a node control unit 202. Although not shown in FIG. 13, in order to perform transmission and reception of a plurality of optical channels, similar to the basic example of FIG. 2, the optical relay device 200 includes an optical switch unit 300 and a transmission / reception unit 310, and the transmission / reception unit 310 includes a plurality of optical transceivers 201. That is, the node control unit 202 controls the optical switch unit 300 and the transmission / reception unit 310 (a plurality of optical transceivers 201 (corresponding to the optical transceiver 311 in FIG. 3)).

[0059] The optical transceiver 201 includes a coherent reception front-end unit 210, a coherent transmission front-end unit 220, a digital signal processing unit 230, a reception light source 240, a transmission light source 250, an ADC 260, and a DAC 270.

[0060] The reception light source 240 generates local light emission r1 having a wavelength (frequency) set from the node control unit 202, and outputs the generated local light emission r1 to the coherent reception front-end unit 210. The transmission light source 250 generates transmission light r2 having a wavelength (frequency) set from the node control unit 202, and outputs the generated transmission light r2 to the coherent transmission front-end unit 220.

[0061] The frequency (wavelength) of the local light emission r1 is the frequency (carrier frequency) of the input optical signal SO1 to be received, and the frequency of the transmission light r2 is the frequency of the output optical signal SO2 to be transmitted. The carrier frequencies of the local light emission r1 and the transmission light r2 are determined based on the carrier frequency information acquired by the node control unit 202 from the network management unit 110.

[0062] The coherent reception front-end unit 210 and the coherent transmission front-end unit 220 have the same configuration as that in FIG. 3. The coherent reception front-end unit 210 is an optical / electrical conversion unit that converts an optical signal into an electrical signal, and is a coherent detection unit that performs coherent detection. The coherent reception front-end unit 210 performs coherent detection on the input input optical signal SO1 (received optical signal) based on the local light emission r1, and outputs the generated analog signal SA1 (first analog electrical signal).

[0063] The ADC (Analog / Digital Converter) 260 performs AD conversion on the analog signal SA1 generated by the coherent reception front-end unit 210 and outputs the converted digital signal SD1 (the first digital electrical signal).

[0064] The DAC (Digital / Analog Converter) 270 performs DA conversion on the digital signal SD2 (the second digital electrical signal) signal-processed by the digital signal processing unit 230 and outputs the converted analog signal SA2 (the second analog electrical signal).

[0065] The coherent transmission front-end unit 220 is an electro-optical conversion unit that converts an electrical signal into an optical signal and is a coherent modulation unit that performs coherent modulation. The coherent transmission front-end unit 220 performs coherent modulation on the analog signal SA2 DA-converted by the DAC 270 based on the transmission light r2 and outputs the generated output optical signal SO2 (transmission optical signal).

[0066] For example, the input optical signal SO1 and the output optical signal SO2 are phase-modulated and polarization-multiplexed optical signals. The analog signals SA1 and SA2 and the digital signals SD1 and SD2 are 4-lane (4ch) signals including the IX signal of the I component (in-phase component) of the X polarization, the QX signal of the Q component (orthogonal component) of the X polarization, the IY signal of the I component of the Y polarization, and the QY signal of the Q component of the Y polarization.

[0067] The digital signal processing unit 230 performs digital signal processing on the digital signal SD1 converted by the ADC 260 and outputs the digital signal SD2 after digital signal processing. The digital signal processing unit 230 is a digital circuit that performs predetermined digital signal processing for compensating signal quality. The digital signal processing unit 230 performs digital signal processing on all or part (X polarization or Y polarization) of the 4-lane IX signal, QX signal, IY signal, and QY signal.

[0068] The digital signal processing unit 230 performs only specific signal processing without performing processing involving large delays such as error correction (data reproduction). As a result, it is possible to compensate for the necessary signal quality while suppressing signal delay. In the present embodiment, the digital signal processing unit 230 includes a dispersion compensation unit 231 (corresponding to the dispersion compensation unit 23 in FIG. 6) that performs dispersion processing, and a phase conjugation processing unit 232 (corresponding to the phase conjugation unit 22 in FIG. 6) that performs phase conjugation processing.

[0069] Wavelength dispersion compensation by digital signal processing can be realized by convolution processing of the impulse response of the inverse transfer function of the optical transmission line and the received signal. Therefore, for example, the dispersion compensation unit 231 may be configured by a transversal filter (FIR filter). Since the characteristics of the optical transmission line can be modeled by an FIR filter, wavelength dispersion can be compensated by an FIR filter with inverse characteristics. The FIR filter performs time domain equalization (TDE: Time Domain Equalizing) that equalizes the received signal in the time delay domain, whereas the same characteristics may be realized by frequency domain equalization (FDE: Frequency Domain Equalization) that equalizes in the frequency domain. By configuring the dispersion compensation unit by FDE, the circuit scale can be reduced compared to an FIR filter.

[0070] In addition to compensating for transmission line wavelength dispersion, the dispersion compensation unit 231 may also compensate for bandwidth degradation due to characteristic degradation and characteristic variations of the analog electrical circuit in each of the four lanes of the IX signal, QX signal, IY signal, and QY signal, amplitude variations in the four lanes, skew and crosstalk in the four lanes, and the like.

[0071] FIG. 14 is a configuration example when the dispersion compensation unit 231 is configured by FDE processing. The dispersion compensation unit 231 in FIG. 14 is a configuration example of overlap FDE, and includes an overlap addition unit 411, a fast Fourier transform unit 412, a frequency response multiplication unit 413, an inverse fast Fourier transform unit 414, and an overlap removal unit 415.

[0072] The node control unit 202 sets the wavelength dispersion compensation amount notified from the control device 100 in the wavelength dispersion compensation unit 231 in the digital signal processing unit 230. When the wavelength dispersion compensation unit 231 is configured by an FDE as shown in FIG. 14, the node control unit 202 sets the coefficient of the frequency response multiplication unit 413 in FIG. 9 according to the wavelength dispersion compensation amount notified from the control device 100, the carrier frequency of each channel, and the signal band.

[0073] The overlap addition unit 411 overlaps a part of the preceding and succeeding signals with respect to the input signal (digital signal). Thereafter, the fast Fourier transform unit 412 converts the overlapped signal into a signal in the frequency domain by fast Fourier transform (FFT).

[0074] The frequency response multiplication unit 413 multiplies and equalizes the frequency response of the wavelength dispersion of the transmission line according to the wavelength dispersion compensation amount notified from the control device 100, the carrier frequency of each channel, and the signal band.

[0075] Thereafter, the inverse fast Fourier transform unit 414 converts the signal into a signal in the time domain by inverse fast Fourier transform (IFFT). The overlap removal unit 415 removes the overlap part from the signal restored in the time domain and outputs it. When using FDE, the wavelength dispersion compensation amount can be adjusted by changing the inverse transfer function. Note that the overlap addition unit 411 and the overlap removal unit 415 may be omitted.

[0076] The phase conjugation process by digital signal processing obtains the complex conjugate of the input digital signal. That is, as shown in the following formula (1), the sign of the imaginary component Q in the Ix signal, Qx signal, Iy signal, and Qy signal is inverted.

[0077]

Equation

[0078] The node control unit 202 receives control information from the control device 100, and controls each part of the optical relay device 200 based on the received control information. The node control unit 202 is an acquisition unit that acquires the optimal wavelength dispersion compensation amount corresponding to the frequency band of each channel from the wavelength dispersion compensation amount calculation unit 130, the phase conjugation processing information from the phase conjugation determination unit 140, the received wavelength information, and the transmission wavelength information from the network management unit 110. The node control unit 202 sets the frequency (wavelength) of the local light emission r1 for the received light source 240 based on the acquired received wavelength information, and sets the frequency of the transmission light r2 for the transmission light source 250 based on the acquired transmission wavelength information. The node control unit 202 sets a phase conjugation processing operation for the phase conjugation processing unit 232 based on the control information including an instruction to perform the phase conjugation processing acquired from the control device 100. The node control unit 202 sets the wavelength dispersion compensation amount for the wavelength dispersion compensation unit 231 based on the acquired optimal wavelength dispersion compensation amount.

[0079] FIG. 15 shows a configuration example of the transmitting end station device 30 in the optical network system 51 according to an embodiment of the present disclosure. Although not shown in FIG. 15, in order to transmit a plurality of optical channels, the transmitting end station device 30 includes a multiplexer 302 as shown in FIG. 2. The transmitting end station device 30 also includes a plurality of optical transmitters 311 for transmitting optical signals of each wavelength.

[0080] As shown in FIG. 15, the transmitting end station device 30 according to an embodiment of the present disclosure includes a transmission node control unit 3001, a data generation unit 3100, a linear compensation unit 3200, a non-linear compensation unit 3400, a DAC 3700, a coherent transmission front-end unit 3500, and a transmission light source 3600.

[0081] The transmission node control unit 3001 acquires the wavelength of the transmission signal and the non-linear distortion compensation information from the control device 100. The transmission light source 3600 generates local light emission r3 with the wavelength (frequency) set by the transmission node control unit 3001, and outputs the generated local light emission r3 to the coherent transmission front-end unit 3500. The frequency of the transmission light r3 is the frequency of the output optical signal SO3 to be transmitted.

[0082] As digital signal processing, the data generation unit 3100 generates a transmission signal by performing error coding and bit symbol mapping. The linear compensation unit 3200 performs pulse shaping, chromatic dispersion pre - equalization, front - end characteristic pre - equalization, etc. The non - linear compensation unit 3400 performs non - linear compensation such as the digital backpropagation method shown in FIG. 9.

[0083] The DAC 3700 performs DA conversion on the digital signal SD3 signal - processed by the non - linear compensation 3400 and outputs the converted analog signal SA3. The digital signal processing generates SD3 to be output to the DAC 3700.

[0084] The coherent transmission front - end unit 3500 is an electro - optical conversion unit that converts an electrical signal into an optical signal and is a coherent modulation unit that performs coherent modulation. The coherent transmission front - end unit 3500 coherently modulates the analog signal SA3 DA - converted by the DAC 3700 based on the transmission optical signal r3 and outputs the generated output optical signal SO3 (transmission optical signal).

[0085] FIG. 16 shows a configuration example of the receiving end - station device 40 in the optical network system 51 according to an embodiment of the present disclosure. Although not shown in FIG. 16, in order to receive a plurality of optical channels, the receiving end - station device 40 includes a demultiplexer 301 as shown in FIG. 2. The receiving end - station device 40 includes a plurality of optical receivers 311 for receiving optical signals of each wavelength.

[0086] As shown in FIG. 16, the receiving end - station device 40 according to an embodiment of the present disclosure includes a receiving node control unit 4001, a data restoration unit 4100, a linear compensation unit 4200, a non - linear compensation unit 4400, an ADC 4700, a coherent reception front - end unit 4500, and a reception light source 4600.

[0087] The receiving node control unit 4001 acquires the wavelength of the received signal and the non - linear distortion compensation information from the control device 100. The transmission light source 3600 generates the local light emission r3 of the wavelength (frequency) set by the transmission node control unit 3001, and outputs the generated local light emission r3 to the coherent transmission front - end unit 3500.

[0088] The coherent reception front - end unit 4500 is an optical / electrical conversion unit that converts an optical signal into an electrical signal and is a coherent detection unit that performs coherent detection. The coherent reception front - end unit 4500 performs coherent detection on the input optical signal SO4 (received optical signal) based on the local light emission r4, and outputs the generated analog signal SA4.

[0089] The ADC 4700 performs AD conversion on the analog signal SA4 generated by the coherent reception front - end unit 4500, and outputs the converted digital signal SD4.

[0090] Regarding SD3, as digital signal processing, in the linear compensation unit 4200, pulse shaping, wavelength dispersion compensation, front - end characteristic pre - equalization, etc. are performed, and in the non - linear compensation unit 4400, non - linear compensation is performed by the digital backpropagation method as shown in FIG. 9. In the data restoration unit 4100, polarization separation, frequency offset compensation, phase regeneration, error correction processing, etc. are performed to restore the data.

[0091] FIG. 17 shows an operation example of an optical network system according to an embodiment of the present disclosure. As shown in FIG. 17, first, the network management unit 110 of the control device 100 determines the position of the optical relay device 200, the transmission line information of the optical transmission lines before and after the optical relay device 200, and the wavelength used by the optical relay device 200 (S101). The network control unit 120 of the control device 100 determines the path of the path in the optical network 51, and specifies the positions of the optical transmission lines and the optical relay device 200 on the path of the path. The network control unit 120 outputs the received wavelength information and the transmitted wavelength information of the optical relay device 200 to the wavelength dispersion compensation amount calculation unit 130 and the phase conjugation determination unit 140 according to the determined wavelength. Further, the network control unit 120 outputs the transmission line information (distance) of the optical transmission lines before and after the optical relay device 200 to the wavelength dispersion compensation amount calculation unit 130 and the phase conjugation determination unit 140. When a plurality of optical relay devices 200 are included in the path constituting the optical network 51, the following processing is performed for each optical relay device 200. The network control unit 120 outputs the received wavelength information of the determined receiving end station device 40 to the receiving end station device 40.

[0092] Next, the wavelength dispersion compensation amount calculation unit 130 of the control device 100 calculates the wavelength dispersion characteristics in the optical transmission paths before and after the optical relay device 200, and determines the phase conjugation and the wavelength dispersion compensation amount (S102). Specific examples of the method for determining the phase conjugation and the wavelength dispersion compensation amount will be described later. Based on the received wavelength information, the transmitted wavelength information, and the transmission path information (distance) of the optical transmission paths before and after the optical relay device 200 acquired from the network control unit 120, the wavelength dispersion compensation amount calculation unit 130 calculates the wavelength dispersion characteristics in the optical transmission paths before and after the optical relay device 200. When the transmission information includes the structure, type, and transmission characteristics of the optical fiber, the wavelength dispersion characteristics may be determined based on this information. For example, the wavelength dispersion characteristics are the slope of the wavelength dispersion amount accumulated with respect to the distance of the optical transmission path (the wavelength dispersion amount according to the distance (FIG. 4)). Since this slope of the wavelength dispersion amount varies depending on the wavelength, a table associating the wavelength (or wavelength band) with the slope of the wavelength dispersion amount may be stored in advance. The wavelength dispersion compensation amount calculation unit 130 may refer to this table and determine the wavelength dispersion characteristics corresponding to the wavelength. That is, the wavelength dispersion characteristics are values determined according to the structure, type, transmission characteristics of the optical fiber constituting the optical network 51, and the frequency of the light used for communication. The wavelength dispersion characteristics may be calculated by inputting values determined according to the structure, type, transmission characteristics of the optical fiber constituting the optical network, and the frequency of the light used for communication into a predetermined calculation formula.

[0093] The wavelength dispersion compensation amount calculation unit 130 determines the optimal wavelength dispersion compensation amount in the optical relay device 200 based on the wavelength dispersion characteristics of the optical transmission paths in the front stage and the rear stage of the optical relay device 200 and the transmission path information of the optical transmission paths in the front stage and the rear stage. The wavelength dispersion compensation amount calculation unit 130 obtains the amount of wavelength dispersion accumulated in the optical transmission path in the front stage (reception side), obtains the amount of wavelength dispersion accumulated in the optical transmission path in the rear stage (transmission side), and determines the optimal wavelength dispersion amount based on the wavelength dispersion amount in the front stage and the wavelength dispersion amount in the rear stage. In particular, the wavelength dispersion compensation amount calculation unit 130 determines the optimal wavelength dispersion amount based on the amount of wavelength dispersion accumulated between the transmission end station device 30 and the optical relay device 200 and the amount of wavelength dispersion accumulated between the optical relay device 200 and the reception end station device 40. For example, the wavelength dispersion compensation amount calculation unit 130 obtains the amount of wavelength dispersion accumulated in the optical transmission path in the front stage based on the wavelength dispersion characteristics and the transmission path information (distance) of the optical transmission path in the front stage of the optical relay device 200, and obtains the amount of wavelength dispersion accumulated in the optical transmission path in the rear stage based on the wavelength dispersion characteristics and the transmission path information of the optical transmission path in the rear stage of the optical relay device 200. In this example, the wavelength dispersion compensation amount calculation unit 130 determines the wavelength dispersion compensation amount based on the wavelength dispersion characteristics and the transmission path information. However, since the wavelength dispersion characteristics correspond to the wavelength information, the wavelength dispersion compensation amount may be determined based on the wavelength information and the transmission path information. That is, the wavelength dispersion compensation amount calculation unit 130 may determine the wavelength dispersion compensation amounts in the plurality of optical relay devices 200 constituting the path based on the wavelength information and the transmission path information in the path. The phase conjugation determination unit 140 determines the optimal phase conjugation process in the optical relay device 200 of the optical network 51.

[0094] Next, the control device 100 notifies the optical relay device 200 of the path information, the received wavelength information, the transmitted wavelength information determined in S101, the optimal phase conjugation process information determined in S102, and the optimal wavelength dispersion compensation amount (S103).

[0095] Next, based on the information notified in S103, the optical relay device 200 executes signal transmission and reception, phase conjugation processing, and chromatic dispersion compensation (S104). The node control unit 202 of the optical relay device 200 sets the wavelength of the wavelength information notified from the control device 100, the phase conjugation processing information, and the optimal chromatic dispersion compensation amount. The node control unit 202 sets the wavelength of the acquired received wavelength information to the received light source 240, and sets the wavelength of the acquired transmission wavelength information to the transmission light source 250. Further, the node control unit 202 sets the acquired phase conjugation processing information to the phase conjugation processing unit 232, and sets the acquired optimal chromatic dispersion compensation amount to the chromatic dispersion compensation unit 231. The received light source 240 generates local light emission r1 of the set wavelength (frequency), and the transmission light source 250 generates transmission light r2 of the set wavelength, thereby performing wavelength conversion in the optical transceiver 201. Also, the phase conjugation processing unit 232 performs phase conjugation processing by phase conjugation, and the chromatic dispersion compensation unit 231 performs chromatic dispersion compensation processing on the signal after the phase conjugation processing based on the set compensation amount by digital signal processing.

[0096] Next, the distortion compensation section determination unit 150 of the control device 100 determines a distortion compensation section that is a transmission path for which the optical relay device 200 performs non-linear distortion compensation (S105). The distortion compensation section determination unit 150 determines a distortion compensation section that is a transmission path for which the optical relay device 200 performs non-linear distortion compensation based on the transmission path information determined by the network management unit 110, the path of the path, the position information of the optical relay device 200, and the information on the phase conjugation and chromatic dispersion compensation amount determined in S102. For example, the distortion compensation section determination unit 150 determines the distortion compensation section of the optical relay device 200 as described with reference to FIGS. 12A and 12B.

[0097] Next, the distortion compensation control unit 160 of the control device 100 determines non-linear distortion compensation information regarding distortion compensation at the transmitting end office device 30. Or the distortion compensation control unit 160 of the control device 100 determines non-linear distortion compensation information regarding distortion compensation at the receiving end office device 40. Specifically, when the distortion compensation section, which is the transmission path for which the optical relay device 200 performs non-linear distortion compensation determined in step S105, exists in the second half with respect to the central position of the distance from the transmitting end office device 30 to the receiving end office device 40 of the optical network 51, the distortion compensation control unit 160 determines the non-linear distortion compensation information used by the transmitting end office device 30 in the distortion compensation process on the assumption that the transmission path outside the distortion compensation section is distorted and compensated at the transmitting end office device 30 (S106A). Also, when the distortion compensation section, which is the transmission path for which the optical relay device 200 performs non-linear distortion compensation determined in step S105, exists in the first half with respect to the central position of the distance from the transmitting end office device 30 to the receiving end office device 40 of the optical network 51, the distortion compensation control unit 160 determines the non-linear distortion compensation information used by the receiving end office device 40 in the distortion compensation process on the assumption that the transmission path outside the distortion compensation section is compensated at the receiving end office device 40 (S106B).

[0098] In the determination of the above-mentioned distortion compensation section, the distortion compensation section determination unit 150 may acquire the transmission path information determined by the network management unit 110, the path of the path, and the position information of the optical relay device 200, and compare the number of transmission paths between the transmission end station device 30 and the optical relay device 200. Then, when the number of transmission paths between the optical relay device 200 and the transmission end station device 30 matches the number of transmission paths between the optical relay device 200 and the reception end station device 40, the optical relay device 200 may determine that all the transmission paths from the transmission end station device 30 to the reception end station device 40 are the distortion compensation section. Further, when the number of transmission paths between the optical relay device 200 and the transmission end station device 30 does not match the number of transmission paths between the optical relay device 200 and the reception end station device 40, the distortion compensation section determination unit 150 may identify the smaller number of the number of transmission paths reaching the transmission end station device 30 and the reception end station device 40 with the optical relay device 200 as the center at the front stage and the rear stage of the optical relay device 200. For example, as shown in FIG. 12A, the distortion compensation section determination unit 150 compares the number of transmission paths "4" reaching the transmission end station device 30 and the number of transmission paths "2" reaching the reception end station device 40 with the optical relay device 200 as the center, and identifies each transmission path of the smaller number "2" at the front stage and the rear stage of the optical relay device 200 (transmission paths 3C, 3D, 3E, 3F). Then, the distortion compensation section determination unit 150 determines that each transmission path (transmission paths 3C, 3D, 3E, 3F) at the front stage and the rear stage of the identified optical relay device 200 is the distortion compensation section of the optical relay device 200. For the transmission paths 3A and 3B that are not identified, the distortion compensation section determination unit 150 determines that they are the distortion compensation sections of the transmission end station device 30 close to those transmission paths.

[0099] The distortion compensation control unit 160 may determine the non-linear distortion compensation information based on the transmission path information such as the wavelength dispersion characteristic, the non-linear characteristic, and the signal propagation loss characteristic managed by the network management unit 110. When the transmission end station device 30 or the reception end station device 40 performs the distortion compensation process using the digital backpropagation method, for example, parameters related to the number of steps or the phase rotation may be determined as the non-linear distortion compensation information.

[0100] Next, the transmitting end station device 30 notifies the receiving end station device 40 of the non - linear distortion compensation information determined in S106A (S107A). Alternatively, the receiving end station device 40 notifies the transmitting end station device 30 of the non - linear distortion compensation information determined in S106B (S107B).

[0101] Next, either the transmitting end station device 30 or the receiving end station device 40 performs non - linear distortion compensation. Specifically, when the compensation section where the optical relay device 200 determined in S105 performs non - linear distortion compensation is in the second half relative to the central position of the distance from the transmitting end station device 30 to the receiving end station device 40 in the optical network 51, the transmission node control unit 3001 of the transmitting end station device 30 sets the non - linear distortion compensation information of the transmitting end station device 30 in the non - linear compensation unit 3400. The non - linear compensation unit 3400 of the transmitting end station device 30 performs non - linear distortion compensation based on the set non - linear distortion compensation information (S108A). When the compensation section where the optical relay device 200 determined in S105 performs non - linear distortion compensation is in the first half relative to the central position of the distance from the transmitting end station device 30 to the receiving end station device 40 in the optical network 51, the receiving node control unit 4001 of the receiving end station device 40 sets the non - linear distortion compensation information of the receiving end station device 40 in the non - linear compensation unit 4400. The non - linear compensation unit 4400 of the receiving end station device 40 performs non - linear distortion compensation based on the set non - linear distortion compensation information (S108B).

[0102] FIG. 18A and FIG. 18B show specific examples of phase - conjugate processing and wavelength - dispersion compensation processing in an optical relay device according to the control method of an embodiment of the present disclosure. In this specific example, the effect of non - linear distortion compensation by phase - conjugate and wavelength - dispersion compensation performed by the optical relay device 200 for the compensation section which is the transmission path for which the distortion compensation section determination unit 150 of the control device 100 determines that the optical relay device 200 performs non - linear distortion compensation can be maximized.

[0103] Here, as an example, a case is shown where a distortion compensation section, which is a transmission path for which the optical relay device 200 performs non-linear distortion compensation, consists of a total of two transmission path sections, namely, a first half indicating a transmission path section from the transmitting terminal device 30 to the optical relay device 200 and a second half indicating a transmission path section from the optical relay device 200 to the receiving terminal device 40. However, when N is an integer of 2 or more, and the distortion compensation section, which is a transmission path for which the optical relay device 200 performs non-linear distortion compensation, consists of a total of 2N transmission path sections, namely, a first half indicating N transmission path sections from the transmitting terminal device 30 to the optical relay device 200 and a second half indicating N transmission path sections from the optical relay device 200 to the receiving terminal device 40, the situation is the same. Also, here, as an example, the endpoints of the distortion compensation section are the transmitting terminal device 30 and the receiving terminal device 40, but the endpoints may be considered as amplification devices in the transmission path.

[0104] In the present embodiment, the optical relay device 200 performs phase conjugation processing on the non-linear distortion accumulated in the previous optical transmission path in the optical signal received by the optical relay device 200. As a result, the non-linear distortion in the transmission in the subsequent optical transmission path of the optical signal transmitted from the optical relay device 200 can be canceled out by the receiving terminal device 40. In order to obtain such an effect, the optical relay device 200 in the present embodiment determines an optimal wavelength dispersion compensation amount such that the non-linear distortion cancellation effect is maximized. The optimal wavelength dispersion compensation amount in this example is the compensation amount calculated based on the wavelength dispersion amounts in the previous transmission path section and the subsequent transmission path section with respect to the optical relay device 200. Also, in this example, the digital signal processing unit 230 of the optical relay device 200 determines the optimal wavelength dispersion compensation amount when performing wavelength dispersion compensation processing after phase conjugation processing. Similarly, when the digital signal processing unit 230 performs phase conjugation processing after wavelength dispersion compensation processing, the optimal wavelength dispersion compensation amount may be determined based on the wavelength dispersion amounts in the previous and subsequent transmission paths. Also, in this example, it is assumed that the digital signal processing unit 230 first performs phase conjugation processing and then performs wavelength dispersion compensation processing.

[0105] As shown in Fig. 18A, in this example, one optical relay device 200 is arranged on the path between the transmitting end station device 30 and the receiving end station device 40. The transmitting end station device 30 and the optical relay device 200 are connected via an optical transmission line 3a (the first optical transmission line), and the optical relay device 200 and the receiving end station device 40 are connected via an optical transmission line 3b (the second optical transmission line). For example, the distance L1 of the optical transmission line 3a and the distance L2 of the optical transmission line 3b are different, and the distance L2 of the optical transmission line 3b is longer than the distance L1 of the optical transmission line 3a, but they may be the same distance. An optical signal with a wavelength of λ1 is transmitted on the optical transmission line 3a, and an optical signal with a wavelength of λ2 is transmitted on the optical transmission line 3b. For example, both the wavelength λ1 and the wavelength λ2 may be in the C-band wavelength band, or they may be different, such as the C-band wavelength band and the L-band wavelength band respectively, or both may be in the L-band wavelength band. The optical relay device 200 converts the received optical signal with a wavelength of λ1 into an optical signal with a wavelength of λ2 and transmits the converted optical signal with a wavelength of λ2.

[0106] As shown in Fig. 18B, in the previous-stage optical transmission line 3a, since the wavelength of the optical signal is λ1, the wavelength dispersion amount gradient DS1 in the optical transmission line 3a is determined by the wavelength dispersion compensation amount calculation unit 130 of the control device 100 according to the wavelength λ1. The wavelength dispersion amount gradient DS1 in the optical transmission line 3a may be read from storage means such as a database. The wavelength dispersion compensation amount calculation unit 130 of the control device 100 uses the wavelength dispersion amount gradient DS1 and the effective nonlinear distance Leff1 in the optical transmission line 3a to obtain the accumulated wavelength dispersion amount M1 (= DS1 × Leff1) at the effective nonlinear distance Leff1 in the previous-stage optical transmission line 3a. The nonlinear effect is an effect that depends on the optical signal intensity. Since the optical intensity in the transmission line decreases according to an exponential function characterized by the propagation loss constant, it is sufficient to consider only the nonlinear effect in the region where the optical intensity is large. The effective nonlinear distance Leff is defined as the distance for considering the nonlinear effect, and Leff is given by the following formula (2) using the length L and the propagation loss constant α in the optical fiber.

[0107]

Equation

[0108] In the subsequent optical transmission path 3b, since the wavelength of the optical signal is λ2, the wavelength dispersion amount gradient DS2 in the optical transmission path 3b is determined by the wavelength dispersion compensation amount calculation unit 130 of the control device 100 according to the wavelength λ2. The wavelength dispersion amount gradient DS2 in the optical transmission path 3b may be read from storage means such as a database. The wavelength dispersion compensation amount calculation unit 130 of the control device 100 calculates M2 = -M1 on the condition that the accumulated wavelength dispersion amount M2 at the effective nonlinear distance Leff2 in the subsequent optical transmission path 3b has a sign opposite to that of the accumulated wavelength dispersion amount M1 at the effective nonlinear distance Leff1 in the previous optical transmission path 3a. Then, the wavelength dispersion compensation amount calculation unit 130 obtains the accumulated wavelength dispersion amount M3 in the transmission signal of the optical relay device. M3 can be calculated by M3 = M2 + DS2 × Leff2 = DS1 × Leff1 + DS2 × Leff2.

[0109] Then, the wavelength dispersion compensation amount calculation unit 130 of the control device 100 obtains the accumulated wavelength dispersion compensation amount M5 for the optical relay device 200 to compensate for wavelength dispersion using phase conjugation by M5 = M4 × 2.

[0110] The wavelength dispersion compensation amount calculation unit 130 of the control device 100 obtains the difference M6 between the accumulated wavelength dispersion amount M3 and the cumulative wavelength dispersion compensation amount M5, and transmits the difference M6 as the optimal wavelength dispersion compensation amount to the optical relay device 200. Further, the control device 100 transmits control information including an instruction to perform phase conjugation processing to the optical relay device 200. Thereby, as described with reference to FIG. 13, the node control unit 202 of the optical relay device 200 instructs the phase conjugation processing unit 232 to perform a phase conjugation processing operation based on the acquired control information including the instruction to perform the phase conjugation processing. The phase conjugation processing unit 232 performs a phase conjugation processing operation. Also, as described with reference to FIG. 13, the node control unit 202 of the optical relay device 200 sets the wavelength dispersion compensation amount M6 notified from the control device 100 in the wavelength dispersion compensation unit 231 in the digital signal processing unit 230. That is, when the wavelength dispersion compensation unit 231 is configured by an FDE as shown in FIG. 13, the node control unit 202 sets the multiplication coefficient of the frequency response multiplication unit 413 in FIG. 14 according to the wavelength dispersion compensation amount M6 notified from the control device 100. Thereby, the optical relay device 200 calculates the cumulative wavelength dispersion compensation amount M5 using the phase conjugation processing of the phase conjugation processing unit 232 for the subsequent optical transmission path 3b, and after performing wavelength dispersion compensation using the wavelength dispersion compensation amount M6 of the wavelength dispersion compensation unit 231, the cumulative wavelength dispersion M3 (M3 = M4 - M5 - M6) is calculated, and an optical signal having the cumulative wavelength dispersion M3 is output (FIG. 14B). Thereby, the non-linear effect in the receiving terminal device 40 is suppressed.

[0111] Note that even if the optical relay device 200 does not perform phase conjugation, the accumulated wavelength dispersion amount M3 can be calculated by M3 = M2 + DS2 × Leff2 = DS1 × Leff1 + DS2 × Leff2. Therefore, the wavelength dispersion compensation unit 231 of the optical relay device 200 may calculate the accumulated wavelength dispersion amount M3 and output an optical signal having the cumulative wavelength dispersion M3 without performing phase conjugation (FIG. 14B).

[0112] In the description of FIGS. 12A and 12B, for the sake of convenience of explanation, it is described that an optical signal with wavelength λ1 is transmitted through the optical transmission path 3a and an optical signal with wavelength λ2 is transmitted through the optical transmission path 3b. However, multiple channels of optical signals with multiple wavelengths λ (frequency bands) may be transmitted through the optical transmission path 3a, and multiple channels of optical signals with multiple wavelengths λ (frequency bands) may also be transmitted through the optical transmission path 3b.

[0113] FIG. 18C is a diagram showing an outline of phase conjugation processing. As shown in FIG. 18C, in a certain transmission path section in the optical network 51 (between network devices such as the transmitting end station device 30 and the optical relay device 200 in FIG. 18C), non-linear distortion of the transmitted signal occurs as signal degradation due to non-linear effects (1111 in FIG. 18C). The optical relay device 200 performs phase conjugation processing (inversion of the optical signal) (1112 in FIG. 18C). As a result, in the transmission path section after the optical relay device 200 (between the optical relay device 200 and the receiving end station device 40), the cancellation effect of non-linear distortion using phase conjugation is exerted, and signal degradation (non-linear distortion) at the receiving end station device 40 can be reduced (1113 in FIG. 18C). In addition to this, when the optical relay device 200 receives a multi-channel signal, by performing wavelength dispersion compensation optimal for the signal band of each channel, the cancellation effect of non-linear distortion at the receiving end station device 40 can be increased.

[0114] The processing in the above-described control device 100 is an aspect of a process of determining the amount of wavelength dispersion compensation to be compensated in the optical relay device 200 based on the wavelength information of the optical signals transmitted and received by the optical relay device 200 constituting the optical network and the transmission path information of the optical transmission path connected to the optical relay device 200 in the path of the optical network, and determining the phase conjugation processing in the optical relay device 200 based on the wavelength information and the transmission path information.

[0115] Also, a part of the processing in the control device 100 is an aspect of a process of transmitting an instruction to the optical relay device 200 to perform phase conjugation processing for calculating the complex conjugate of the optical signal based on the accumulated wavelength dispersion amount M4 of the optical signal received by the optical relay device 200.

[0116] Also, a part of the processing in the control device 100 is an aspect of a process for calculating a first accumulated wavelength dispersion amount M1 at a first effective nonlinear distance (Leff1) with respect to a transmission-side network device in a first optical transmission path (front-stage path) between the transmission-side network device of the optical transmission path to which the optical relay device 200 is connected and which transmits the optical signal received by the optical relay device 200.

[0117] Also, a part of the processing in the control device 100 is an aspect of a process for calculating a second accumulated wavelength dispersion amount M2, which is a second accumulated wavelength dispersion amount at a second effective nonlinear distance (Leff2) with respect to the own device of the optical signal in a second optical transmission path (rear-stage path) between the reception-side network device of the optical signal transmitted by the optical relay device 200 and which has a sign opposite to that of the first accumulated wavelength dispersion amount (multiplied by -1).

[0118] Also, a part of the processing in the control device 100 is an aspect of a process for calculating a wavelength dispersion compensation amount M6, which indicates the difference between the wavelength dispersion amount M3 at the time of transmission in the optical relay device 200 of the optical signal when the accumulated wavelength dispersion amount of the optical signal becomes the second accumulated wavelength dispersion amount M2 at the second effective nonlinear distance (Leff2) based on the statistical value (DS2) of the transition of the accumulated wavelength dispersion amount of the optical signal according to the distance in the second optical transmission path and the wavelength dispersion amount M5, which is the result of complex conjugation.

[0119] The processing of the above-described optical relay device 200 is an aspect of a process for performing wavelength dispersion compensation processing on an electrical signal based on the received optical signal based on the wavelength dispersion compensation amount M6 and performing phase conjugation processing on the electrical signal based on the received optical signal based on the phase conjugation processing information acquired from the control device 100.

[0120] Also, a part of the processing in the above-described optical relay device 200 is an aspect of a process for performing the phase conjugation processing based on the accumulated wavelength dispersion amount of the optical signal received by the own device and an instruction to perform the phase conjugation processing for calculating the complex conjugate of the optical signal.

[0121] In addition, some of the processes in the above-described optical relay device 200 are an aspect of a process of determining the wavelength dispersion amount (M3) of an optical signal to be transmitted to a receiving-side network device based on the wavelength dispersion amount (M5), which is the result of complex conjugation, after performing phase conjugation processing, and the wavelength dispersion compensation amount (M6) acquired from the control device 100.

[0122] FIG. 19 shows another example of the wavelength dispersion compensation amount by the control method in an embodiment of the present disclosure. Different from FIG. 18B, in this example, as shown in FIG. 19, the transmitting end-office device 30 transmits an optical signal with an accumulated wavelength dispersion amount M10 to the optical transmission line 3a. When considering the transmitting end-office device 30 as an optical relay device 200, a signal amplifier, etc. in the optical network 51, there may be a case where dispersion such as the accumulated wavelength dispersion amount M10 occurs in the optical signal transmitted by the transmitting end-office device 30.

[0123] As shown in FIG. 19, in the optical transmission line 3a in front of the optical relay device 200, since the wavelength of the optical signal is λ1, the control device 100 determines the slope DS1 of the wavelength dispersion amount in the optical transmission line 3a according to the wavelength λ1. The control device 100 obtains the accumulated wavelength dispersion amount M11 (= DS1 × Leff1 + M10) at the effective nonlinear distance Leff1 in the optical transmission line 3a in front using the effective nonlinear distance Leff1.

[0124] In addition, in the optical transmission line 3b in the rear stage, since the wavelength of the optical signal is λ2, the control device 100 determines the slope DS2 of the wavelength dispersion amount in the optical transmission line 3b according to the wavelength λ2. The control device 100 obtains the accumulated wavelength dispersion amount M13 (= DS1 × Leff1 + DS2 × Leff2 + M10) in the transmission signal of the optical relay device on the condition that the accumulated wavelength dispersion amount M12 at the effective nonlinear distance Leff2 in the optical transmission line 3b in the rear stage has a different sign from the accumulated wavelength dispersion amount M11 at the effective nonlinear distance Leff1 in the optical transmission line 3a in the front stage. The control device 100 obtains the phase conjugate compensation amount M15 (= M14 × 2) compensated by phase conjugation in the optical relay device 200.

[0125] The control device 100 calculates the difference M16 between M13 and M15, and sets M6 as the optimal wavelength dispersion compensation amount in the optical relay device 200. The control device 100 sets the optical relay device 200 to perform phase conjugation processing.

[0126] As described above, in this embodiment, in the optical relay device 200 that performs wavelength conversion for each channel, the analog signal output from the coherent reception front-end unit 210 is converted into a digital signal by an ADC, and after digital signal processing, it is converted back into an analog signal by a DAC and relayed back to the coherent transmission front-end unit 220. At this time, the digital signal processing unit 230 performs phase conjugation processing. Also at this time, in the digital signal processing unit 230, wavelength dispersion distortion generated in the optical fiber transmission line is compensated based on the transmission line length of the network path (transmission line), the signal band and carrier frequency of the signal channel. Further, in the coherent transmission front-end unit 220, each carrier frequency is set so that the order of each channel is swapped in the frequency domain.

[0127] Specifically, in the control device 100, the optimal wavelength dispersion compensation amount in the frequency band of each channel to be compensated by the optical relay device is obtained so that the accumulated wavelength dispersion amount at the effective non-linear distance in the previous transmission line and the accumulated wavelength amount at the effective non-linear distance in the subsequent transmission line have opposite signs. The optical relay device 200 performs phase conjugation and wavelength dispersion compensation based on the obtained optimal wavelength dispersion compensation amount, the signal band of the signal channel, and the carrier frequency. As a result, the non-linear distortion accumulated in the previous optical transmission line at the receiving end of the optical relay device 200 can be offset by the optical transmission in the subsequent optical transmission, and the effect of suppressing the non-linear distortion in the receiving end station device 40 can be maximized. Further, even when the transmission signal from the transmitting end station device 30 contains an extra dispersion amount as shown in FIG. 12, an appropriate wavelength dispersion amount can be set by the optical relay device 200 to compensate for the non-linear distortion. Furthermore, by setting the carrier frequency so that the order of each channel is swapped in the frequency domain in the coherent transmission front-end unit 220, inter-channel non-linear distortion can be reduced.

[0128] (Embodiment 2) Next, Embodiment 2 will be described with reference to the drawings. In this embodiment, the configuration and basic operations of the optical network system are the same as those in Embodiment 1. FIGS. 20A and 20B show the concept of the control method for the distortion compensation process of the transmitting and receiving terminal device 30 controlled by the distortion compensation control unit 160 of the control device 100 based on the information on the distortion compensation section of the optical relay device 200 determined by the distortion compensation section determination unit 150 of the control device 100. In this embodiment, an example in which both the transmitting and receiving terminal device 30 and the receiving terminal device 40 perform non-linear distortion compensation will be described.

[0129] FIG. 20A is a first diagram showing the concept of the control method for the distortion compensation process of the transmitting and receiving terminal device 30 controlled by the distortion compensation control unit 160 of the control device 100. Assume an optical network 51 composed of an optical transmission line consisting of six transmission line sections (3A, 3B, 3C, 3D, 3E, 3F), five optical signal amplifiers 50 for compensating the transmission loss for one transmission line section, and one optical relay device 200, a transmitting terminal device 30, and a receiving terminal device 40 each. Also, the optical relay device 200 is located in the second half from the center between the transmitting terminal device 30 and the receiving terminal device 40.

[0130] For example, assume that as shown in FIG. 20A, the optical relay device 200 is located between the transmission lines 3D and 3E. As described with reference to FIG. 12A of Embodiment 1, the distortion compensation section determination section 150 of the control device 100 determines the distortion compensation section of the optical relay device 200 to be 3C to 3F. The distortion compensation control section 160 of the control device 100 takes into account the noise derived from the front end in the transmitting end station device 30, the noise derived from the front end in the receiving end station device 40, and the noise added by signal amplification or the like in the transmission lines 3A to 3F, and determines the distortion compensation section L1A of the transmitting end station device 30 and the distortion compensation section L1B of the receiving end station device 40 outside the distortion compensation section of the optical relay device 200 (transmission lines 3A and 3B) so that the effect of the non-linear distortion compensation performed by the transmitting and receiving end station devices 30 and the receiving end station device 40 is maximized. Specifically, the distortion compensation control section 160 of the control device 100 stores in advance a data table associating the magnitude of the noise (such as SNR) and the information on the optimal distortion compensation section compensated by the transmitting end station device 30 and the receiving end station device 40 (transmitting and receiving device) when there is noise derived from the transmission line and the noise derived from the transmitting and receiving front ends obtained by simulation or transmission evaluation, and may determine the distortion compensation sections L1A and L2B according to the data table.

[0131] The noise from the front end in the transmitting station device 30 and the noise from the front end in the receiving station device 40 may be evaluated individually in advance using a signal analyzer or the like provided in the transmitting station device 30, or may be estimated by an equalization algorithm (equalization processing using signal optimization in digital signal processing). The noise from the front end refers to non-linearity of the driver amplifier, bias deviation of the modulator, IQ distortion such as skew between lanes, and bandwidth narrowing in DAC, ADC, etc. The noise added by signal amplification or the like in the transmission lines 3A to 3F may be estimated by evaluating the noise intensity at the receiving station device 40, or may be estimated using an approximate mathematical model assuming the noise as white Gaussian noise. The distortion compensation control unit 160 of the control device 100 notifies the transmitting station device 30 of the non-linear distortion compensation information in the distortion compensation section of L1A, and notifies the receiving station device 40 of the non-linear distortion compensation information in the distortion compensation section of L1B. Based on the notified non-linear distortion compensation information, the transmitting station device 30 and the receiving station device 40 perform distortion compensation processing respectively.

[0132] FIG. 20B is a second diagram showing the concept of the control method of the distortion compensation processing of the transmitting and receiving station device 30 controlled by the distortion compensation control unit 160 of the control device 100. Assume an optical network 51 composed of an optical transmission path consisting of six transmission path sections (3A, 3B, 3C, 3D, 3E, 3F), five optical signal amplifiers 50 for compensating the transmission loss for one transmission path section, one optical relay device 200 each, a transmitting station device 30, and a receiving station device 40. Also, the optical relay device 200 is located entirely in the middle of the distance between the transmitting station device 30 and the receiving station device 40.

[0133] For example, assume that as shown in FIG. 20B, the optical relay device 200 is located between transmission lines 3B and 3C. As shown in Embodiment 1, the distortion compensation section determination unit 150 of the control device 100 determines the distortion compensation section of the optical relay device 200 as 3A to 3D. The distortion compensation control unit 160 of the control device 100 takes into account the noise derived from the front end in the transmitting terminal device 30, the noise derived from the front end in the receiving terminal device 40, and the noise added by signal amplification or the like in the transmission lines 3A to 3F, and determines the distortion compensation section L2A of the transmitting terminal device 30 and the distortion compensation section L2B of the receiving terminal device 40 outside the distortion compensation section of the optical relay device 200 (transmission lines 3E and 3F) so that the effect of the non-linear distortion compensation performed by the transmitting terminal device 30 and the receiving terminal device 40 is maximized. The distortion compensation control unit 160 of the control device 100 notifies the transmitting terminal device 30 of the non-linear distortion compensation information in the distortion compensation section L2A and notifies the receiving terminal device 40 of the non-linear distortion compensation information in the distortion compensation section L2B. Based on the notified non-linear distortion compensation information, the transmitting terminal device 30 and the receiving terminal device 40 perform distortion compensation processing respectively.

[0134] Thereby, by performing transmission and reception distortion compensation control in consideration of the cumulative noise along the signal propagation in the optical network 51, it becomes possible to maximize the effect of non-linear distortion compensation outside the distortion compensation section of the optical relay device 200. Further, by dividing the non-linear distortion compensation section between the transmitting terminal device 30 and the receiving terminal device 40, it becomes possible to reduce the circuit scale related to the non-linear distortion compensation of each of the transmitting terminal device 30 and the receiving terminal device 40.

[0135] In the above-described process, the control device 100 may determine the distortion compensation section of the optical relay device 200 and notify at least one of the transmitting terminal device 30 (transmitting device) or the receiving terminal device 40 (receiving device) of the non-linear distortion compensation information used for non-linear distortion compensation in the transmission line outside the distortion compensation section of the optical relay device 200. Then, at least one of the transmitting terminal device 30 (transmitting device) or the receiving terminal device 40 (receiving device) may generate and transmit a signal that has been non-linearly distortion-compensated based on the non-linear distortion compensation information acquired from the control device 100, and the optical relay device 200 may perform non-linear distortion compensation based on the non-linear distortion compensation information. Non-linear distortion compensation may be performed by either the transmitting terminal device 30 (transmitting device) or the receiving terminal device 40 (receiving device) when the influence of noise generated at any location among the transmitting terminal device 30 (transmitting device), the receiving terminal device 40 (receiving device), and the transmission line is small. Conversely, when the influence of noise is large at any location among the transmitting terminal device 30 (transmitting device), the receiving terminal device 40 (receiving device), and the transmission line, non-linear distortion compensation is performed by both the transmitting terminal device 30 (transmitting device) and the receiving terminal device 40 (receiving device).

[0136] The control device 100, the optical relay device 200, the transmitting terminal device 30, and the receiving terminal device 40 in the above-described embodiment are configured by hardware or software, or both, and may be configured from one piece of hardware or software, or may be configured from a plurality of pieces of hardware or software. Each device (such as the control device) and each function (process) may be realized by a computer 60 having a processor 61 such as a CPU (Central Processing Unit) and a memory 62 which is a storage device, as shown in FIG. 21. For example, a program for performing the method (such as the control method) in the embodiment may be stored in the memory 62, and each function may be realized by the processor 61 executing the program stored in the memory 62.

[0137] These programs, when loaded into a computer, include a set of instructions (or software code) for causing the computer to perform one or more functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD), or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disc, or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may also be transmitted on a transient computer-readable medium or a communication medium. By way of example and not limitation, the transient computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0138] As described above, the control device 100, optical relay device 200, transmitting end station device 30, and receiving end station device 40 of this disclosure have been described. However, this disclosure is not limited to the above-described embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of this disclosure within the scope of this disclosure. And each embodiment can be combined with other embodiments as appropriate.

[0139] Note that some or all of the above embodiments may be described as follows in the appended claims, but are not limited thereto.

[0140] (Appended Claim 1) An optical relay device constituting an optical network and a control device for controlling the optical relay device, The control device is management means for managing wavelength information of an optical signal transmitted and received by the optical relay device in a path of the optical network and transmission path information of an optical transmission path connected to the optical relay device; Wavelength dispersion compensation control means for determining the amount of wavelength dispersion compensation to be compensated in the optical relay device based on the wavelength information and the transmission path information; Phase conjugate processing control means for determining phase conjugate processing in the optical relay device based on the wavelength information and the transmission path information; Comprising: The optical relay device: Wavelength dispersion compensation amount acquisition means for acquiring the determined amount of wavelength dispersion compensation from the control device; Phase conjugate processing acquisition means for acquiring the determined phase conjugate processing information from the control device; Phase conjugate processing means for performing phase conjugate processing on an electrical signal based on an optical signal to be received based on the acquired phase conjugate processing information; Wavelength dispersion compensation means for performing wavelength dispersion compensation processing on an electrical signal based on an optical signal to be received based on the acquired amount of wavelength dispersion compensation; An optical network system comprising:

[0141] (Appendix 2) The wavelength dispersion compensation control means calculates the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the receiving side of the optical relay device and the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the transmitting side of the optical relay device based on the wavelength information and the transmission path information on the receiving side of the optical relay device and the wavelength information and the transmission path information on the transmitting side of the optical relay device. The optical network system according to Appendix 1.

[0142] (Appendix 3) The wavelength dispersion compensation control means determines the amount of wavelength dispersion compensation based on the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the receiving side of the optical relay device, the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the transmitting side of the optical relay device, and the amount of wavelength dispersion compensation by phase conjugate processing in the optical relay device. The optical network system according to Appendix 2.

[0143] (Appendix 4) The wavelength dispersion compensation control means determines the wavelength dispersion compensation amount based on the accumulated wavelength dispersion amount included in the transmission signal before optical transmission in the optical transmission path on the receiving side of the optical relay device, the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the receiving side of the optical relay device, the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the transmitting side of the optical relay device, and the wavelength dispersion compensation amount by phase conjugation processing in the optical relay device. The optical network system according to any one of Appendices 1 to 3.

[0144] (Appendix 5) The wavelength dispersion compensation amount is a compensation amount obtained on the condition that the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the receiving side of the optical relay device and the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path on the transmitting side of the optical relay device have different signs. The optical network system according to any one of Appendices 1 to 4.

[0145] (Appendix 6) In an optical network configured by connecting three or more odd-numbered paths through the optical relay device, the wavelength dispersion compensation control means and the phase conjugation processing control means determine the wavelength dispersion compensation amount and the phase conjugation processing in the target optical relay device based on the wavelength information and the transmission path information in the paths before and after the target optical relay device other than the optical relay device connected to the last path among the plurality of paths. The optical network system according to claim 1.

[0146] (Appendix 7) The wavelength dispersion compensation control means and the phase conjugation processing control means obtain a combination of two paths, a front stage and a rear stage, and one optical relay device that relays the paths in the optical relay device as a set, and one remaining path, and determine the target optical relay device as other than the optical relay device connected to the remaining one path. The optical network system according to any one of Appendices 1 to 6.

[0147] (Appendix 8) The phase conjugate processing control means determines the phase conjugate processing for the optical relay device in the combination. The optical network system according to Supplementary Note 7.

[0148] (Supplementary Note 9) Based on the wavelength information and the transmission path information in the two optical transmission paths of the combination, the wavelength dispersion compensation amount in the optical relay device of the combination is determined by the wavelength dispersion compensation control means. The optical network system according to any one of Supplementary Note 7 or Supplementary Note 8.

[0149] (Supplementary Note 10) Based on the wavelength information and the transmission path information in the optical transmission path of the remaining one path, the wavelength dispersion compensation amount in the optical relay device of the remaining one path is determined by the wavelength dispersion compensation control means. The optical network system according to Supplementary Note 7.

[0150] (Supplementary Note 11) The wavelength dispersion compensation amount is a compensation amount obtained on the condition that the accumulated wavelength dispersion amount at the effective non-linear distance in the optical transmission path of the remaining one path becomes zero. The optical network system according to any one of Supplementary Notes 7 to 10.

[0151] (Supplementary Note 12) In an optical network configured by connecting four or more even-numbered paths through the optical relay device, the wavelength dispersion compensation control means and the phase conjugate processing control means are based on the wavelength information and the transmission path information in the paths before and after each of the optical relay devices in the plurality of paths, and determine the wavelength dispersion compensation amount and the phase conjugate processing in the optical relay device. The optical network system according to any one of Supplementary Notes 7 to 11.

[0152] (Supplementary Note 13) The wavelength dispersion compensation control means and the phase conjugate processing control means obtain a combination of two optical transmission paths and one optical relay device as a set in the optical relay device. The optical network system according to any one of Appendices 1 to 12.

[0153] (Appendix 14) The phase conjugate processing control means determines the phase conjugate processing for the optical relay device in the combination. The optical network system according to any one of Appendices 7 to 13.

[0154] (Appendix 15) The wavelength dispersion compensation control means determines the wavelength dispersion compensation amount in the optical relay device of the combination based on the wavelength information and the transmission path information in the two optical transmission paths of the combination. The optical network system according to any one of Appendices 7 to 14.

[0155] (Appendix 16) Manage the wavelength information of the optical signal transmitted and received by the optical relay device in the path of the optical network, the transmission path information of the optical transmission path connected to the optical relay device, and the number of paths of the optical network. Based on the wavelength information, the transmission path information, and the number of paths of the optical network, determine the wavelength dispersion compensation amount and the phase conjugate processing to be compensated in the optical relay device. Control method.

[0156] (Appendix 17) Based on the accumulated wavelength dispersion amount in the effective non-linear distance of the optical transmission path on the receiving side of each optical relay device in the path of the optical network and the accumulated wavelength dispersion amount in the effective non-linear distance of the optical transmission path on the transmitting side of the optical relay device, determine the wavelength dispersion compensation amount and the phase conjugate processing. The control method according to Appendix 16.

[0157] (Appendix 18) Manage the wavelength information of the optical signal transmitted and received by the optical relay device in the path of the optical network, the transmission path information of the optical transmission path connected to the optical relay device, and the number of paths of the optical network. Based on the wavelength information, the transmission path information, and the number of paths in the optical network, determine the wavelength dispersion compensation amount and the phase conjugation process to be compensated in the optical relay device. A control program for causing a computer to execute the process.

[0158] (Appendix 19) Based on the accumulated wavelength dispersion amount in the effective non-linear distance in the optical transmission path on the receiving side of each optical relay device in the path of the optical network and the accumulated wavelength dispersion amount in the effective non-linear distance in the optical transmission path on the transmitting side of the optical relay device, determine the wavelength dispersion compensation amount and the phase conjugation process. The program according to Appendix 18.

[0159] (Appendix 20) Wavelength dispersion compensation control means for determining the wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information of the optical signal transmitted and received by the optical relay device constituting the optical network in the path of the optical network and the transmission path information of the optical transmission path connected to the optical relay device, Phase conjugation process control means for determining the phase conjugation process in the optical relay device based on the wavelength information and the transmission path information, A control device comprising:

[0160] (Appendix 21) The phase conjugation process control means transmits an instruction to perform the phase conjugation process for calculating the complex conjugate of the optical signal to the optical relay device. The control device according to Appendix 20.

[0161] (Appendix 22) The wavelength dispersion compensation control means calculates the first accumulated wavelength dispersion amount in the first effective non-linear distance with respect to the first network device on the transmission side in the first optical transmission path between the optical relay device and the network device on the transmission side that transmits the optical signal received by the optical relay device among the optical transmission paths connected to the optical relay device, The second accumulated wavelength dispersion amount at the second effective nonlinear distance with respect to the own device of the optical signal in the second optical transmission path between the optical relay device and the network device on the reception side of the optical signal transmitted by the optical relay device among the optical transmission paths to which the optical relay device is connected, which is the second accumulated wavelength dispersion amount having a sign opposite to that of the first accumulated wavelength dispersion amount, is calculated. The wavelength dispersion compensation amount, which is the difference between the wavelength dispersion amount at the time of transmission of the optical signal in the optical relay device and the wavelength dispersion amount that is the result of complex conjugation, when the accumulated wavelength dispersion amount of the optical signal becomes the second accumulated wavelength dispersion amount at the second effective nonlinear distance based on the statistical value of the transition of the accumulated wavelength dispersion amount of the optical signal according to the distance in the second optical transmission path, is calculated. The control device according to Supplementary Note 21.

[0162] (Supplementary Note 23) Wavelength dispersion compensation control means for determining the wavelength dispersion compensation amount to be compensated in the own device based on the wavelength information of the optical signal transmitted and received by the own device constituting the optical network and the transmission path information of the optical transmission path connected to the own device in the path of the optical network, Phase conjugation processing control means for determining the phase conjugation processing in the own device based on the wavelength information and the transmission path information, An optical relay device that shows the own device that is communicatively connected to a control device including Phase conjugation processing means for performing phase conjugation processing on the electrical signal based on the received optical signal based on the phase conjugation processing information acquired from the control device, Wavelength dispersion compensation means for performing wavelength dispersion compensation processing on the electrical signal based on the received optical signal based on the wavelength dispersion compensation amount, An optical relay device including

[0163] (Supplementary Note 24) The phase conjugation processing means performs the phase conjugation processing based on an instruction to perform the phase conjugation processing for calculating the complex conjugation of the optical signal. The optical relay device according to Supplementary Note 23.

[0164] (Supplementary Note 25) Calculate the first accumulated wavelength dispersion amount at the first effective nonlinear distance based on the transmitting-side network device in the first optical transmission path between the transmitting-side network device with which the optical relay device communicates and the optical transmission path that the optical relay device receives among the optical transmission paths to which the optical relay device is connected. Calculate the second accumulated wavelength dispersion amount at the second effective nonlinear distance based on the self-device of the optical signal in the second optical transmission path between the receiving-side network device of the optical signal transmitted by the optical relay device and the optical transmission path that the optical relay device transmits among the optical transmission paths to which the optical relay device is connected, where the second accumulated wavelength dispersion amount has a sign opposite to that of the first accumulated wavelength dispersion amount. Control and communicate with the calculation of the wavelength dispersion compensation amount, which is the difference between the wavelength dispersion amount at the time of transmission of the optical signal in the optical relay device and the wavelength dispersion amount that is the result of complex conjugation when the accumulated wavelength dispersion amount of the optical signal becomes the second accumulated wavelength dispersion amount at the second effective nonlinear distance based on the statistical value of the transition of the accumulated wavelength dispersion amount of the optical signal according to the distance in the second optical transmission path. After performing the phase conjugation process, wavelength dispersion compensation means for determining the wavelength dispersion amount of the optical signal transmitted to the receiving-side network device based on the wavelength dispersion amount that is the result of complex conjugation and the wavelength dispersion compensation amount obtained from the control device. The optical relay device according to appended note 24, comprising the above.

[0165] (Appended note 26) Digital signal processing means for performing frequency flip processing on at least one or more channels of optical signals in channel units. An optical relay device comprising the above.

[0166] (Appended note 27) The digital signal processing means performs the frequency flip processing on all channels of the optical signal in channel units. The optical relay device according to appended note 26.

[0167] (Appended note 28) The digital signal processing means sequentially identifies channels to be processed and channels not to be processed among a plurality of channels having different frequency bands, based on the frequency bands, and performs the frequency flip process on the channels to be processed. The optical relay device according to appended note 26 or appended note 27.

[0168] (Appended note 29) The digital signal processing means performs the frequency flip process of inverting the frequency components of the optical signal for each frequency, based on a reference frequency set at the center in the frequency band. The optical relay device according to any one of appended notes 26 to 28.

[0169] (Appended note 30) The digital signal processing means phase conjugate processing means for performing phase conjugate processing on an electrical signal based on the received optical signal; chromatic dispersion compensation means for performing chromatic dispersion compensation processing on an electrical signal based on the received optical signal; frequency flip processing means for performing the frequency flip process; The optical relay device according to any one of appended notes 26 to 29, comprising

[0170] (Appended note 31) The frequency flip processing means performs the phase conjugate processing and the chromatic dispersion compensation processing on all channels of the optical signal, and performs the frequency flip process in units of channels on at least one or more channels. The optical relay device according to any one of appended notes 26 to 30.

[0171] (Appended note 32) chromatic dispersion compensation processing means for performing chromatic dispersion compensation processing on an electrical signal based on the received optical signal, based on the carrier frequency and the frequency band of the corresponding channel among a plurality of channels included in the optical signal; phase conjugate processing means for performing phase conjugate processing on an electrical signal based on the received optical signal; An optical relay device comprising

[0172] (Appendix 33) The wavelength dispersion compensation processing means performs wavelength dispersion compensation processing based on the frequency region of the corresponding channel among the frequency bands of all channels of the plurality of channels having different frequency bands. The optical relay device described in Appendix 32.

[0173] (Appendix 34) The wavelength dispersion compensation processing means performs wavelength dispersion compensation processing based on the frequency region of the corresponding channel among the frequency bands of all channels of the plurality of channels having different frequency bands, before or after the phase conjugation processing. The optical relay device described in Appendix 32 or Appendix 33.

[0174] (Appendix 35) Carrier frequency control means for performing carrier frequency control to change the frequencies of a plurality of channels included in the optical signal, The optical relay device according to any one of Appendices 32 to 34, comprising the above.

[0175] (Appendix 36) The carrier frequency control means identifies the order of a plurality of the channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, and determines the carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels. The optical relay device described in Appendix 35.

[0176] (Appendix 37) The carrier frequency control means identifies the order of a plurality of the channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, determines the carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels, and further gives a constant frequency offset to each of the channels. The optical relay device described in Appendix 35 or Appendix 36.

[0177] (Appendix 38) Perform dispersion compensation processing based on the carrier frequency and frequency band of the corresponding channel among the plurality of channels included in the optical signal on the electrical signal based on the received optical signal, Perform phase conjugation processing on the electrical signal based on the received optical signal Optical relay method.

[0178] (Appendix 39) Perform carrier frequency control to change the frequencies of the plurality of channels included in the optical signal The optical relay method according to Appendix 38.

[0179] (Appendix 40) Perform the dispersion compensation processing based on the frequency region of the corresponding channel among the frequency bands of all the channels of the plurality of channels having different frequency bands The optical relay method according to Appendix 38 or Appendix 39.

[0180] (Appendix 41) Before or after the phase conjugation processing, perform the dispersion compensation processing based on the frequency region of the corresponding channel among the frequency bands of all the channels of the plurality of channels having different frequency bands The optical relay method according to any one of Appendix 38 to Appendix 40.

[0181] (Appendix 42) Among the plurality of channels having different frequency bands, specify the order of the plurality of channels arranged in order based on the frequency band, and determine the carrier frequencies of the plurality of channels at the time of transmission so as to reverse the order of the channels The optical relay method according to any one of Appendix 38 to Appendix 41.

[0182] (Appendix 43) Among the plurality of channels with different frequency bands, identify the order of a plurality of the channels arranged in order based on the frequency band, determine the carrier frequencies at the time of transmitting the plurality of channels so as to reverse the order of the channels, and further give a constant frequency offset to each of the channels. The optical relay method according to any one of Appendices 38 to 42.

[0183] (Appendix 44) An optical relay device Wavelength dispersion compensation processing means for performing wavelength dispersion compensation processing based on the carrier frequency and frequency band of the corresponding channel among the plurality of channels included in the optical signal on the electrical signal based on the received optical signal. Phase conjugation processing means for performing phase conjugation processing on the electrical signal based on the received optical signal. A program for causing it to function as such.

[0184] (Appendix 45) Carrier frequency control means for performing carrier frequency control to change the frequencies of the plurality of channels included in the optical signal. The program according to Appendix 44 for causing it to function as such.

[0185] (Appendix 46) The wavelength dispersion compensation processing means Performs wavelength dispersion compensation processing based on the frequency region of the corresponding channel among the frequency bands of all channels of the plurality of channels with different frequency bands. The program according to Appendix 44 or Appendix 45.

[0186] (Appendix 47) The wavelength dispersion compensation processing means Before or after the phase conjugation processing, performs wavelength dispersion compensation processing based on the frequency region of the corresponding channel among the frequency bands of all channels of the plurality of channels with different frequency bands. The program according to any one of Appendices 44 to 46.

[0187] (Appendix 48) The carrier frequency control means identifies the order of a plurality of the channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, and determines the carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels. The program according to Supplementary Note 45.

[0188] (Supplementary Note 49) The carrier frequency control means identifies the order of a plurality of the channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, determines the carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels, and further gives a constant frequency offset to each of the channels. The program according to Supplementary Note 45 or Supplementary Note 48.

[0189] (Supplementary Note 50) A transmission device including a first non-linear distortion compensation unit, A reception device including a second non-linear distortion compensation unit, One or more optical relay devices having a third non-linear distortion compensation unit, An optical transmission path connecting the transmission device, the optical relay device, and the reception device, A control device for controlling the transmission device, the reception device, and the optical relay device, An optical network system including the above.

[0190] (Supplementary Note 51) The control device determines a distortion compensation section of the optical relay device in a transmission path in which the optical relay device performs non-linear distortion compensation. The optical network system according to Supplementary Note 50.

[0191] (Supplementary Note 52) The control device transmits non-linear distortion compensation information used for the non-linear distortion compensation to the transmission device or the reception device according to the position of the distortion compensation section of the optical relay device with respect to the optical transmission path. The optical network system described in Supplementary Note 51.

[0192] (Supplementary Note 53) The control device When the distortion compensation section of the optical relay device is located in the latter half of the transmission line, notifies the transmission device of non-linear distortion compensation information used for non-linear distortion compensation of the transmission line outside the distortion compensation section of the optical relay device. When the distortion compensation section of the optical relay device is located in the first half of the transmission line, notifies the receiving device of non-linear distortion compensation information used for non-linear distortion compensation in the transmission line outside the distortion compensation section of the optical relay device. The optical network system described in Supplementary Note 52.

[0193] (Supplementary Note 54) The control device Based on the signal noise derived from the transmission device, the signal noise derived from the receiving device, and the noise added in the transmission line, for the transmission line section outside the distortion compensation section of the optical relay device, determines the distortion compensation section for non-linear distortion compensation by the transmission device and the distortion compensation section for non-linear distortion compensation by the receiving device. The optical network system described in Supplementary Note 53.

[0194] (Supplementary Note 55) The control device Based on the distortion compensation section of the transmission device and the distortion compensation section of the receiving device, notifies the transmission device or the receiving device of non-linear distortion compensation information used for the non-linear distortion compensation process performed by the transmission device or the receiving device. The optical network system described in Supplementary Note 54.

[0195] (Supplementary Note 56) A transmission device having a first non-linear distortion compensation section, A receiving device having a second non-linear distortion compensation section, One or more optical relay devices having a third non-linear distortion compensation section, An optical transmission line connecting the transmission device, the optical relay device, and the receiving device, A control device that controls the transmission device, the receiving device, and the optical relay device A control device of an optical network system including the optical relay device determines a distortion compensation section of the optical relay device, and notifies at least one of the transmission device or the reception device of non-linear distortion compensation information used for non-linear distortion compensation in a transmission path outside the distortion compensation section of the optical relay device. At least one of the transmission device or the reception device generates and transmits a signal obtained by performing non-linear distortion compensation based on the non-linear distortion compensation information. The optical relay device performs non-linear distortion compensation based on the non-linear distortion compensation information. Control method.

[0196] (Appendix 57) A transmission device including a first non-linear distortion compensation section, A reception device including a second non-linear distortion compensation section, One or more optical relay devices having a third non-linear distortion compensation section, An optical transmission path connecting the transmission device, the optical relay device, and the reception device, A control device for controlling the transmission device, the reception device, and the optical relay device, A program for a control device of an optical network system including the above, the control device determines a distortion compensation section of the optical relay device, and executes a process of notifying at least one of the transmission device or the reception device of non-linear distortion compensation information used for non-linear distortion compensation in a transmission path outside the distortion compensation section of the optical relay device.

Explanation of Signs

[0197] 1 ··· Optical network system 200 ··· Optical relay device 3 ··· Optical transmission path 5 ··· Data center 6 ··· IT service provider 7, 8 ··· Event venue 10 ··· Control device 11 ··· Management section 12 ··· Phase conjugate control section 13 ··· Wavelength dispersion compensation control section 14 ··· Distortion compensation section determination section 15 ··· Distortion compensation control section 20... Optical Relay Device 21... Coherent Reception Front-End Unit 22... Phase Conjugation Unit 23... Chromatic Dispersion Compensation Unit 24... Coherent Transmission Front-End Unit 25... Phase Conjugation Acquisition Unit 26... Chromatic Dispersion Compensation Acquisition Unit 30... Transmitting End Office Device 31... Data Generation Unit 32... Linear Compensation Unit 33... Nonlinear Compensation Acquisition Unit 34... Nonlinear Compensation Unit 35... Coherent Transmission Front-End 40... Receiving End Office Device 41... Data Restoration Unit 42... Linear Compensation Unit 43... Nonlinear Compensation Acquisition Unit 44... Nonlinear Compensation Unit 45... Coherent Reception Front-End 50... Optical Network System 51... Optical Network 60... Computer 61... Processor 62... Memory 100... Control Device 110... Network Management Unit 120... Network Control Unit 130... Chromatic Dispersion Compensation Amount Calculation Unit 140... Phase Conjugation Determination Unit 150... Distortion Compensation Interval Judgment Unit 160... Distortion Compensation Control Unit 201... Optical Transceiver 202... Node Control Unit 210... Coherent Reception Front-End Unit 220... Coherent Transmission Front-End Unit 230... Digital Signal Processing Unit 231... Chromatic Dispersion Compensation Unit 232... Phase Conjugation Processing Unit 240 ··· Receiving light source 250 ··· Transmitting light source 260 ··· ADC 270 ··· DAC 300 ··· Optical switch section 301 ··· Demultiplexer 302 ··· Multiplexer 303 ··· Branch insertion section 310 ··· Transceiver section 311, 312, 313 ··· Optical transceivers 500 ··· Nonlinear compensation section 501 ··· Chromatic dispersion compensation section 502 ··· Phase rotation compensation section 411 ··· Overlap addition section 412 ··· Fast Fourier transform section 413 ··· Frequency response multiplication section 414 ··· Inverse fast Fourier transform section 415 ··· Overlap removal section 910 ··· Acquisition section 901 ··· Digital signal processing section 3001 ··· Transmitting node control section 3100 ··· Data generation section 3200 ··· Linear compensation section 3400 ··· Nonlinear compensation section 3500 ··· Coherent transmission front end 3600 ··· Transmitting light source 3700 ··· DAC 3001 ··· Receiving node control section 3100 ··· Data restoration section 3200 ··· Linear compensation section 3400 ··· Nonlinear compensation section 3500 ··· Coherent reception front end 3600 ··· Transmitting light source 3700 ··· ADC

Claims

1. A transmitting device including a first non-linear distortion compensation unit, a receiving device including a second non-linear distortion compensation unit, one or more optical relay devices having a third non-linear distortion compensation unit, an optical transmission line connecting the transmitting device, the optical relay device, and the receiving device, and a control device for controlling the transmitting device, the receiving device, and the optical relay device. An optical network system comprising the above components.

2. The control device determines a distortion compensation section of the optical relay device in a transmission line where the optical relay device performs non-linear distortion compensation. The optical network system according to Claim 1.

3. The control device transmits non-linear distortion compensation information used for the non-linear distortion compensation to the transmitting device or the receiving device according to the position of the distortion compensation section of the optical relay device with respect to the optical transmission line. The optical network system according to Claim 2.

4. The control device notifies the transmitting device of non-linear distortion compensation information used for non-linear distortion compensation of a transmission line outside the distortion compensation section of the optical relay device when the distortion compensation section of the optical relay device is located in the latter half of the transmission line. When the distortion compensation section of the optical relay device is located in the first half of the transmission line, the control device notifies the receiving device of non-linear distortion compensation information used for non-linear distortion compensation of a transmission line outside the distortion compensation section of the optical relay device. The optical network system according to Claim 3.

5. The control device determines, based on signal noise derived from the transmitting device, signal noise derived from the receiving device, and noise added in the transmission line, a distortion compensation section in which the transmitting device performs non-linear distortion compensation and a distortion compensation section in which the receiving device performs non-linear distortion compensation for a transmission line section outside the distortion compensation section of the optical relay device. The optical network system according to Claim 4.

6. The control device notifies the transmitting device or the receiving device of non-linear distortion compensation information used for non-linear distortion compensation processing performed by the transmitting device or the receiving device based on the distortion compensation section of the transmitting device and the distortion compensation section of the receiving device. The optical network system according to Claim 5.

7. A transmitting device including a first non-linear distortion compensation unit, a receiving device including a second non-linear distortion compensation unit, one or more optical relay devices having a third non-linear distortion compensation unit, an optical transmission line connecting the transmitting device, the optical relay device, and the receiving device, and a control device for controlling the transmitting device, the receiving device, and the optical relay device. A control device of an optical network system including the same determines a distortion compensation section of the optical relay device, and notifies at least one of the transmission device and the reception device of non-linear distortion compensation information used for non-linear distortion compensation in a transmission line outside the distortion compensation section of the optical relay device. At least one of the transmission device and the reception device generates and transmits a signal obtained by performing non-linear distortion compensation based on the non-linear distortion compensation information. The optical relay device performs non-linear distortion compensation based on the non-linear distortion compensation information. Control method.

8. A transmission device including a first non-linear distortion compensation section, A reception device including a second non-linear distortion compensation section, One or more optical relay devices each having a third non-linear distortion compensation section, An optical transmission line connecting the transmission device, the optical relay device, and the reception device, A control device that controls the transmission device, the reception device, and the optical relay device, A program for causing a control device of an optical network system including the same to execute a process of determining a distortion compensation section of the optical relay device and notifying at least one of the transmission device and the reception device of non-linear distortion compensation information used for non-linear distortion compensation in a transmission line outside the distortion compensation section of the optical relay device.

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