Optical repeater, optical repeating method, and program

Abstract

To provide an optical repeater that suppresses the degradation of signal quality due to nonlinear distortion in optical transmission.SOLUTION: An optical repeater performs: chromatic dispersion compensation processing on an electrical signal based on a received optical signal, the processing being based on a carrier frequency and frequency band of the relevant channel among channels included in the optical signal; and phase conjugation processing on the electrical signal based on the received optical signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical repeater, an optical repeater method, and a program. [Background technology]

[0002] In recent years, the introduction of 5G wireless communication systems has been progressing, and in the post-5G era, there is a growing demand not only for wireless communication but also for optical communication fields for large-capacity communication, ultra-high speed, ultra-low latency, and multiple simultaneous connections. For this reason, research on optical communication systems is being conducted with the expectation that they will be used for a variety of communication services and industrial applications.

[0003] For example, in backbone optical communication systems, a digital coherent method that combines optical phase modulation and polarization multiplexing / demultiplexing technology has been used to achieve a capacity of over 100 Gbps (Giga bit per second). Furthermore, research and development is being conducted on a transmission method that improves frequency utilization efficiency and enables multiple simultaneous connections by narrowing the signal band and using wavelength division multiplexing (WDM). Research and development is also being conducted on distortion compensation technology that uses optical processing or digital signal processing to compensate for signal distortion that occurs during optical transmission, which hinders high-capacity communication due to high baud rates and high multi-level signal modulation in optical communication systems.

[0004] As a related technique, for example, Patent Document 1 is known. Patent Document 1 discloses connecting an optical phase conjugator that generates a phase conjugate signal by digital signal processing between a transmitting device and a receiving device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2012 / 0224855 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology related to the optical network system described above, there is a demand for suppressing degradation of signal quality due to nonlinear distortion in optical transmission.

[0007] An object of the present disclosure is to provide an optical network system, a control method, a control program, a control device, and an optical repeater that solve the above-mentioned problems. [Means for solving the problem]

[0008] The optical repeater according to the present disclosure comprises a wavelength dispersion compensation processing means for performing wavelength dispersion compensation processing on an electrical signal based on a received optical signal, based on the carrier frequency and frequency band of a corresponding channel among a plurality of channels contained in the optical signal, and a phase conjugation processing means for performing phase conjugation processing on the electrical signal based on the received optical signal.

[0009] The optical relay method disclosed herein performs wavelength dispersion compensation processing on an electrical signal based on a received optical signal, based on the carrier frequency and frequency band of a corresponding channel among multiple channels contained in the optical signal, and performs phase conjugation processing on the electrical signal based on the received optical signal.

[0010] The program of the present disclosure causes an optical repeater to function as a chromatic dispersion compensation processing means that performs chromatic dispersion compensation processing on an electrical signal based on a received optical signal, based on the carrier frequency and frequency band of a relevant channel among multiple channels contained in the optical signal, and a phase conjugation processing means that performs phase conjugation processing on an electrical signal based on the received optical signal. Effect of the Invention

[0011] According to the present disclosure, it is possible to suppress degradation of signal quality due to nonlinear distortion in optical transmission. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a configuration diagram showing a configuration example of an optical network system according to a basic example. [Diagram 2] FIG. 2 is a configuration diagram showing a configuration example of an optical repeater according to a basic example. [Diagram 3] 1 is a configuration diagram showing a configuration of an optical transceiver according to the present disclosure. [Figure 4A] 1 is a diagram for explaining a problem with an optical transceiver according to the present disclosure. [Figure 4B] 1 is a diagram for explaining a problem with an optical transceiver according to the present disclosure. [Diagram 5] 1 is a configuration diagram showing a schematic configuration of a control device according to the present disclosure. [Figure 6] 1 is a configuration diagram showing a schematic configuration of an optical repeater according to the present disclosure. [Figure 7] FIG. 1 is a configuration diagram illustrating an example of a configuration of an optical network system according to an embodiment of the present disclosure. [Figure 8] 1 illustrates an example configuration of each device in an optical network system according to an embodiment of the present disclosure. [Figure 9A] 1 is a conceptual diagram showing a specific example of carrier frequency control by a control method according to an embodiment of the present disclosure. [Figure 9B] 1 is a conceptual diagram showing a specific example of carrier frequency control by a control method according to an embodiment of the present disclosure. [Figure 9C] 1 is a conceptual diagram showing a specific example of carrier frequency control by a control method according to an embodiment of the present disclosure. [Figure 10] 1 illustrates an example configuration of each device in an optical network system according to an embodiment of the present disclosure. [Figure 11] 1 is a diagram illustrating a configuration example of a chromatic dispersion compensator according to an embodiment of the present disclosure. [Figure 12A] FIG. 2 is a conceptual diagram illustrating a specific example of chromatic dispersion compensation according to an embodiment of the present disclosure. [Figure 12B] FIG. 2 is a conceptual diagram illustrating a specific example of chromatic dispersion compensation according to an embodiment of the present disclosure. [Figure 13]1 is a flowchart illustrating an example of an operation of an optical network system according to an embodiment of the present disclosure. [Figure 14A] FIG. 13 is a diagram showing a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 14B] FIG. 13 is a diagram showing a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 14C] FIG. 1 is a diagram illustrating an overview of phase conjugation processing according to an embodiment of the present disclosure. [Figure 15] FIG. 13 is a diagram showing a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 16A] FIG. 13 is another diagram showing a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 16B] FIG. 13 is another diagram showing a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 17A] FIG. 13 is another diagram showing a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 17B] FIG. 13 is another diagram showing a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 18] FIG. 13 is a diagram illustrating another configuration of the control device according to the embodiment of the present disclosure. [Figure 19] FIG. 11 is a diagram showing a process flow by a control device of another configuration according to an embodiment of the present disclosure. [Figure 20] FIG. 13 is a diagram illustrating another configuration of the optical relay device according to the embodiment of the present disclosure. [Figure 21] FIG. 11 is a diagram showing a process flow by an optical repeater device having another configuration according to an embodiment of the present disclosure. [Figure 22] FIG. 13 is a diagram illustrating another configuration of the optical relay device according to the embodiment of the present disclosure. [Figure 23] FIG. 11 is a diagram showing a process flow by an optical repeater device having another configuration according to an embodiment of the present disclosure. [Figure 24] FIG. 1 is a configuration diagram showing an overview of the hardware of a computer according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the optical network system, control method, control program, control device, and optical repeater of the present disclosure will be described with reference to the drawings. In each drawing, the same elements are given the same reference numerals, and duplicated explanations will be omitted as necessary. Note that the arrows in the configuration diagrams (block diagrams) are examples for explanation, and do not limit the type or direction of signals.

[0014] (Considerations leading to the embodiment) 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 multiplexing optical transmission system, and the devices that constitute the system perform wavelength multiplexing of optical signals, and perform high-level modulation and digital coherent transmission with optical signals of each wavelength to perform large-capacity communication of over 100 Gbps. High-density wavelength multiplexing makes it possible to improve the frequency utilization efficiency of light, and can handle mobile traffic and wavelength defragmentation.

[0015] The optical network system 1 includes optical repeaters 2 (e.g., 2-1 to 2-10) that can flexibly switch transmission paths (wavelength paths or optical transmission paths) as optical signals in order to switch transmission paths when a failure occurs or to meet local traffic demands (e.g., traffic demands for communication from data centers 4 and 5, the network of an IT service provider 6, and the networks of event venues 7 and 8). The optical network system 1 includes optical repeaters 2 (e.g., 2-1 to 2-10) that can maintain communication by optical signals as an infrastructure. The optical repeaters 2 are photonic nodes that can relay wavelength-multiplexed optical signals, and are, for example, ROADM (Reconfigurable Optical Add / Drop Multiplexer) devices. A wavelength path (also simply referred to as a path) is assigned to each optical repeater 2, and the optical repeater 2 transfers traffic of the local network or other optical repeaters 2 that it accommodates to a destination network or other communication devices via an optical communication cable that transmits optical signals of the assigned wavelength path.

[0016] 2 shows a configuration example of an optical repeater 2 according to a basic example. The optical repeater 2 drops / adds an optical wavelength multiplexed signal, and coherently modulates / demodulates the signals of each wavelength that are dropped / added. As shown in FIG. 2, the optical repeater 2 includes an optical switch unit 300 and a transmitting / receiving unit 310.

[0017] The optical switch unit 300 transfers an optical signal of a predetermined wavelength path received from a previous-stage optical repeater 2 in the optical network system 1 to a subsequent-stage optical repeater 2, and also drops / adds the received optical signal for each wavelength. For example, the optical switch unit 300 includes a demultiplexer 301, a multiplexer 302, and a drop / add unit 303. The demultiplexer 301 separates an optical signal received from the optical transmission line 3 into optical signals of multiple wavelengths. The multiplexer 302 multiplexes optical signals of multiple wavelengths into one optical signal and transmits it to the optical transmission line 3. The drop / add unit 303 drops / adds the optical signal of each wavelength between the demultiplexer 301 and the multiplexer 302.

[0018] The transceiver unit (transponder) 310 receives optical signals of each wavelength branched from the add / drop unit 303 of the optical switch unit 300, and outputs the received data that has been coherently demodulated to a local device (network). The transceiver unit 310 also inputs transmission data from the local device, and transmits (inserts) the coherently modulated optical signals of each wavelength to the add / drop unit 303 of the optical switch unit 300. The transceiver unit 310 includes a plurality of optical transceivers 311 that transmit and receive optical signals of each wavelength. The optical transceivers 311 receive optical signals of a specified wavelength, and further transmit optical signals of a specified wavelength (same or different from the received wavelength) to a destination.

[0019] Here, we consider problems that arise when an optical transceiver is used as the optical transceiver 311. Fig. 3 shows an example of the configuration of an 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. The digital signal processing enables phase conjugation processing and chromatic dispersion compensation on a channel-by-channel basis.

[0020] The coherent reception front-end unit 210 coherently detects an optical signal received from the optical repeater 2 at the previous stage by using a local light (local oscillator 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 (coherently modulates) the signal processed by the digital signal processing unit 901 to a predetermined wavelength, and transmits the generated optical signal to the optical repeater 2 at the next stage. The digital signal processing unit 901 is a DSP (Digital Signal Processor), converts the signal coherently detected by the coherent reception front-end unit 210 to a digital signal, outputs the processed reception data, and also regenerates the input transmission data and outputs the signal converted for optical modulation to the coherent transmission front-end unit 220. In this disclosure, the digital signal processing unit 901 performs phase conjugation processing and chromatic dispersion compensation on a channel-by-channel basis.

[0021] 4A and 4B show the amount of chromatic dispersion when an optical repeater 90 including an optical transceiver 311 according to this disclosure is used. As shown in Fig. 4A, the optical repeater 90 is connected between a transmitting terminal device (transmitting end) 30 and a receiving terminal device (receiving end) 40 via optical transmission paths 3a and 3b. The optical transmission path 3a has a distance L1, and the optical transmission path 3b has a distance L2, and L1 and L2 may be the same length or different lengths. An optical signal with a wavelength λ1 is transmitted through the optical transmission path 3a, and an optical signal with a wavelength λ2 is transmitted through the optical transmission path 3b.

[0022] 4A, the side of the optical repeater 90 on the transmitting terminal device 30 side may be referred to as the front stage of the optical repeater 90 (the receiving side of the optical signal), and the side of the optical repeater 90 on the receiving terminal device 40 side may be referred to as the rear stage of the optical repeater 90 (the transmitting side of the optical signal). Also, the optical transmission path between the optical repeater 90 and the transmitting terminal device 30 may be referred to as the front stage (first portion) optical transmission path, and the optical transmission path between the optical repeater 90 and the receiving terminal device 40 may be referred to as the rear stage (second portion) optical transmission path.

[0023] As shown in FIG. 4B, the amount of chromatic dispersion increases in proportion to the distance of the optical transmission path. For this reason, if the optical repeater 90 relays an optical signal by simply amplifying the signal, the amount of chromatic dispersion continues to increase according to the distance from the transmitting terminal device 30 to the receiving terminal device 40. Then, as the distance of the optical transmission path increases, the quality of the optical signal received at the receiving terminal device 40 deteriorates significantly. In addition to chromatic 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 material changes in proportion to the optical signal strength when an optical signal propagates through an optical fiber, causing a change in the phase of the light itself. Such nonlinear distortion is a factor that limits the increase in capacity and long-distance transmission due to the increase in the baud rate and multi-value of optical signals.

[0024] In the example disclosed above, when the optical repeater 90 connected to the path from the transmitting terminal device 30 to the receiving terminal device 40 receives an optical signal consisting of one or more optical channels, the optical repeater 90 performs digital signal processing equivalent to phase conjugation and chromatic dispersion compensation for each received channel. In the example disclosed above, by performing phase conjugation and chromatic dispersion compensation in the optical repeater 90, the nonlinear distortion occurring in the upstream transmission path and the nonlinear distortion occurring in the downstream transmission path in the phase conjugate light transmitted from the optical repeater 90 are offset, and the influence of the nonlinear distortion in the receiving terminal device 40, which is the receiving end, can be mitigated.

[0025] In the above disclosed example, the effect of intra-channel nonlinear distortion in an optical transmission line is compensated for. The intra-channel nonlinear distortion refers to nonlinear distortion occurring in a single channel during single-channel transmission in the optical transmission line.

[0026] In addition to the examples disclosed above, it is desirable to obtain a sufficient compensation effect for inter-channel nonlinear distortion when there are multiple optical channels of an optical transmission signal transmitted through an optical fiber. In the present disclosure, it is possible to compensate for the nonlinear effect between channels during multi-channel transmission in an optical repeater in a multiple optical transmission network. Note that nonlinear distortion includes intra-channel nonlinear distortion and inter-channel nonlinear distortion. Intra-channel nonlinear distortion refers to nonlinear distortion occurring in a channel due to the optical signal of that channel. On the other hand, inter-channel nonlinear distortion refers to nonlinear distortion occurring in a channel due to the optical signal of a channel other than the channel in question when multiple optical channels are transmitted through an optical transmission path.

[0027] The outline of this embodiment is shown. When an optical repeater receives an optical signal consisting of multiple channels, the repeater configuration is shown, which performs optical phase conjugation to compensate for inter-channel nonlinear distortion in addition to intra-channel nonlinear distortion, and optimal chromatic dispersion compensation according to the channel frequency band and carrier frequency replacement. In addition, although the effect of compensating for intra-channel nonlinear distortion and inter-channel nonlinear distortion is small, optimal chromatic dispersion compensation according to the channel band and carrier frequency replacement may be either one of them.

[0028] (Outline of the embodiment) Fig. 5 shows a schematic configuration of a control device according to this embodiment. Fig. 6 shows a schematic configuration of an optical repeater according to this embodiment. The control device 10 and the optical repeater 20 constitute an optical network system. The optical repeater 20 according to this embodiment constitutes a part of the optical network system, and the control device 10 according to this embodiment controls the optical repeater 20 which is another component of the optical network system.

[0029] As shown in FIG. 5, the control device 10 includes a management unit 11, a phase conjugate control unit 12, a chromatic dispersion compensation control unit 13, and a carrier frequency control unit 14. The management unit 11 manages transmission line information of an optical transmission line connected to an optical repeater 20 in a path of an optical network. The phase conjugate control unit 12 determines a phase conjugate process in the optical repeater 20 based on the transmission line information managed by the management unit 11 and the wavelength information managed by the carrier frequency control unit 14. The chromatic dispersion compensation control unit 13 determines the amount of chromatic dispersion compensation to be compensated in the optical repeater 20 based on the transmission line information managed by the management unit 11 and the carrier frequency managed by the carrier frequency control unit. The carrier frequency control unit 14 specifies the order of magnitude of frequency values ​​in the frequency domain of each channel of an optical signal consisting of multiple channels received by the optical repeater 20, and controls the carrier frequency of the transmission signal of each channel so that the order of magnitude of frequency values ​​in the frequency domain of each channel is interchanged in the transmission signal.

[0030] As shown in Fig. 6, the optical repeater 20 includes a coherent receiving front-end unit 21, a phase conjugation unit 22, a chromatic dispersion compensation unit 23, a coherent transmitting front-end unit 24, a phase conjugation acquisition unit 25, a chromatic dispersion compensation acquisition unit 26, and a carrier frequency acquisition unit 27. Although not shown in Fig. 6, the optical repeater transmits and receives multiple optical channels, and performs phase conjugation, chromatic dispersion compensation, and carrier frequency setting for the signals of each channel.

[0031] The phase conjugate acquisition unit 25 acquires the phase conjugate processing determined by the phase conjugate control unit 12 from the control device 10. The chromatic dispersion compensation acquisition unit 26 acquires the amount of chromatic dispersion compensation determined by the chromatic dispersion compensation control unit 13 from the control device 10. The carrier frequency acquisition unit 27 acquires information on the reception carrier frequency and the transmission carrier frequency of each channel determined by the carrier frequency control unit 14. The coherent reception front end unit 21 coherently detects the received optical signal based on the local light of the reception carrier frequency acquired from the carrier frequency acquisition unit 27, and outputs the coherently detected electrical signal. The phase conjugate unit 22 performs phase conjugation processing by digital signal processing on the electrical signal output from the coherent reception front end unit 21 based on the phase conjugate processing setting acquired by the phase conjugate acquisition unit 25. The chromatic dispersion compensation unit 23 performs chromatic dispersion compensation processing by digital signal processing on the electrical signal output from the phase conjugate unit 22 based on the amount of chromatic dispersion compensation acquired by the chromatic dispersion compensation acquisition unit 26. The coherent transmission front-end unit 24 coherently modulates the electrical signal that has been phase conjugated by the phase conjugation unit 22 and the electrical signal that has been chromatic dispersion compensated by the chromatic dispersion compensation unit 23, based on the local light of the transmission carrier frequency acquired from the carrier frequency acquisition unit 27, and transmits the coherently modulated optical signal.

[0032] As described above, in the embodiment, the control device 10 determines the phase conjugation process and the amount of chromatic dispersion compensation in the optical repeater 20 based on the wavelength information and signal band information of the optical signal transmitted and received by the optical repeater 20 in the path, and the transmission line information of the optical transmission line connected to the optical repeater 20. The control device 10 performs the determined phase conjugation process and chromatic dispersion compensation amount in the optical repeater 20 to compensate for nonlinear distortion. The control device 10 also specifies the order of magnitude of frequency values ​​in the frequency domain of each channel of the optical signal consisting of multiple channels received by the optical repeater 20, and controls the carrier frequency so that the order of magnitude of frequency values ​​in the frequency domain of each channel in the transmission signal is interchanged, thereby compensating for the nonlinear effect between channels.

[0033] By performing phase conjugation of the optical signal in the optical repeater 20, the distortion of the optical signal can be reversed in the optical transmission path in front of the optical repeater 20. By propagating the signal in the optical transmission path in the rear of the optical repeater 20, the distortion is reversed and offset at the receiving end. According to the embodiment described below, the optical repeater 20 can perform chromatic dispersion compensation with an appropriate phase conjugation and chromatic dispersion compensation amount, so that it is possible to maximize the offset effect of nonlinear distortion due to multi-span optical transmission by using phase conjugation and chromatic dispersion compensation in each optical repeater 20 in a multi-span optical network, and it is possible to effectively suppress the deterioration of signal quality due to nonlinear distortion at the receiving end of the optical network. In addition, the optical repeater 20 can suppress the nonlinear effect between channels by selecting the optimal chromatic dispersion compensation according to the carrier frequency and signal band, and the carrier frequency so as to switch the order of the frequency values ​​in the frequency domain of each channel in the multi-channel optical signal.

[0034] (Embodiment 1) Next, a first embodiment will be described with reference to the drawings. Fig. 7 shows a configuration example of an optical network system according to an embodiment of the present disclosure. As shown in Fig. 7, an optical network system 50 according to an embodiment of the present disclosure includes a control device 100, a plurality of optical repeaters 200, a transmitting terminal device 30, and a receiving terminal device 40.

[0035] The optical repeater devices 200, the transmitting terminal device 30, and the receiving terminal device 40 are connected to each other via an optical transmission path 3 so that they can communicate with each other optically. The optical repeater devices 200, the transmitting terminal device 30, and the receiving terminal device 40 are connected to the control device 100 so that they can communicate control signals. The optical repeater devices 200, the transmitting terminal device 30, and the receiving terminal device 40 may be connected to the control device 100 via the optical transmission path 3, or may be connected to each other via any other transmission path including wired or wireless so that they can communicate with each other.

[0036] The multiple optical repeaters 200, the transmitting terminal device 30, and the receiving terminal device 40 are optical transmission devices (optical nodes) that perform optical communication via the optical transmission path 3. The transmitting terminal device 30 constitutes the transmitting end of a path formed by connecting multiple optical transmission paths 3. The receiving terminal device 40 constitutes the receiving end of a path formed by connecting multiple optical transmission paths 3. The transmitting terminal device 30 transmits multi-channel optical signals wavelength-multiplexed using the wavelengths of the path set by the control device 100 to the receiving terminal device 40 via the optical transmission path 3. The receiving terminal device 40 receives multi-channel optical signals wavelength-multiplexed using the wavelengths of the path set by the control device 100 from the transmitting terminal device 30 via the optical transmission path 3.

[0037] The optical repeaters 200 are repeaters capable of repeating wavelength-multiplexed multi-channel optical signals, as in the basic example. The optical repeaters 200 constitute an optical network 51 for performing WDM communication. It can be said that the optical repeaters 200, together with the transmitting terminal device 30 and the receiving terminal device 40, constitute the optical network 51. The optical network 51 is a wavelength-multiplexed optical network, as in FIG. 1. 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. In addition, the optical repeaters 200 form a path from the transmitting terminal device 30 to the receiving terminal device 40 under the control of the control device 100, and transmit optical signals (data) at wavelengths set on the path route.

[0038] The control device 100 manages and controls an optical network 51 including a plurality of optical repeater devices 200. For example, the control device 100 is an NMS (Network Management System) that manages the network.

[0039] The control device 100 manages and controls paths formed by optical repeater devices 200 in the optical network 51. The control device 100 manages the route and wavelength of the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the route and wavelength of the path for the transmitting terminal device 30, the receiving terminal device 40, and the optical repeater devices 200 on the path.

[0040] 8 shows an example of the configuration of each device in an optical network system according to an embodiment of the present disclosure. As shown in FIG. 8, the control device 100 includes a network management unit 110, a network control unit 120, a chromatic dispersion compensation amount calculation unit 130, a phase conjugation determination unit 140, and a carrier frequency control unit 150.

[0041] 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 and path configuration information 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 relationship of the optical repeater 200, the transmitting terminal device 30, and the receiving terminal device 40 that constitute the network, and transmission line information of the optical transmission line 3 that connects each device. The transmission line information includes the distance L (transmission line length) of the optical transmission line, and may also include the structure, type, and transmission characteristics of the optical fiber. The path configuration information includes information of each device that constitutes the path, the wavelengths that each device can use on the path, and the usage status of the wavelengths. These pieces of information may be set in advance in the database, or may be set based on information collected from each device, and may further be updated by the network control unit 120 or the like.

[0042] The network control unit 120 corresponds to the management unit 11 shown in FIG. 5 and controls the paths in the optical network 51 and the optical repeater 200, the transmitting terminal device 30, and the receiving terminal device 40 that constitute the paths. The network control unit 120 refers to the network configuration information and the path configuration information in the network management unit 110, determines the route of the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the determined route in the transmitting terminal device 30, the receiving terminal device 40, and the optical repeater 200 on the path route. The network control unit 120 also outputs information required for calculating the amount of chromatic dispersion compensation in the optical repeater 200 that constitutes the path to the chromatic dispersion compensation amount calculation unit 130. For example, the network control unit 120 outputs transmission path information of the optical transmission paths before and after. The network control unit 120 also outputs phase conjugation determination information in the optical repeater 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 repeaters in the optical network 51.

[0043] The chromatic dispersion compensation amount calculation unit 130 corresponds to the chromatic dispersion compensation control unit 13 shown in FIG. 5, and calculates the amount of chromatic dispersion compensation for the optical repeater 200 constituting the path to perform chromatic dispersion compensation. The chromatic dispersion compensation amount calculation unit 130 is a compensation control unit that determines and controls the amount of chromatic dispersion compensation of the optical repeater 200. The chromatic dispersion compensation amount calculation unit 130 determines the optimal amount of chromatic dispersion compensation for the optical repeater 200 based on the reception wavelength information, signal band, transmission wavelength information, and transmission line information before and after the optical repeater, of the optical repeater 200 obtained from the network control unit 120 and the carrier frequency control unit 150. The chromatic dispersion compensation amount calculation unit 130 notifies the corresponding optical repeater 200 of the reception wavelength information, transmission wavelength information, and optimal amount of chromatic dispersion compensation of the optical repeater 200.

[0044] 5, and controls the phase conjugation process of the optical repeater 200 that constitutes the path. The phase conjugation determination unit 140 determines the optimal phase conjugation process for the optical repeater 200 based on the number of paths and the number of optical repeaters in the optical network 51 obtained from the network control unit 120. The phase conjugation determination unit 140 notifies the optical repeater 200 of the phase conjugation process information.

[0045] The carrier frequency control unit 150 corresponds to the carrier frequency control unit 14 shown in Fig. 5, and 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 repeater device 200 on the path route. The carrier frequency of the light in the path is determined for each optical transmission line in the path route. In addition, the carrier frequency control unit 150 outputs information required for calculating the amount of chromatic dispersion compensation in the optical repeater device 200 constituting the path to the chromatic dispersion compensation amount calculation unit 130. For example, the carrier frequency control unit 150 outputs the receiving wavelength information (wavelength information of the received optical signal) and the transmitting wavelength information (wavelength information of the transmitted optical signal) of the optical repeater device 200.

[0046] Assume that the optical repeater 200 receives an optical signal consisting of multiple channels. The carrier frequency selector 150 identifies the order of magnitude of the frequency values ​​of the multiple channels arranged in order based on the frequency band among the multiple channels with different frequency bands of the optical signal received by the corresponding optical repeater 200, and determines the carrier frequency of each channel in the transmission signal based on the carrier frequency and signal band of each channel of the received signal so that the order is reversed in the transmission signal. The carrier frequency selector 150 notifies the corresponding optical repeater 200 of the determined carrier frequency of each channel of the received signal and the transmission signal of the optical repeater 200.

[0047] FIG. 9A is a first diagram showing an outline of carrier frequency setting for channel switching instructed by the carrier frequency selection unit 150. Assume that the optical repeater 200 receives signals in the frequency bands of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The carrier frequencies of the channels are f1, f2, and f3, respectively, and the signal bands of the channels are Δf1, Δf2, and Δf3, respectively. The carrier frequency control unit 150 sets the carrier frequency of each channel so that the output signal received by the optical repeater 200 has a reverse order of frequency values ​​in the frequency domain of each channel. When the widths of the signal bands of the channels are all equal, the order of frequency values ​​of each channel is reversed by setting the carrier frequency of 1ch to f3, the carrier frequency of 2ch to f2, and the carrier frequency of 3ch to f1.

[0048] FIG. 9B is a second diagram showing an outline of carrier frequency setting for channel switching instructed by the carrier frequency selection unit 150. Assume that the optical repeater 200 receives signals in the frequency bands of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The carrier frequencies of the channels are f1, f2, and f3, respectively, and the signal bands are Δf1, Δf2, and Δf3, respectively. Assume that the widths of the signal bands indicated by Δf1, Δf2, and Δf3 are not equivalent. The carrier frequency control unit 150 sets the carrier frequency of each channel so that the output signal received by the optical repeater 200 has a reverse order of frequency values ​​in the frequency domain of each channel. The carrier frequencies of the channels 1ch, 2ch, and 3ch of the output signal of the optical repeater 200 are set to f3' (=f2+(f2-f1)), f2, and f1' (=f2-(f3-f2)), thereby reversing the order of frequency values ​​of each channel. The optical repeater 200 outputs optical signals by setting the signal bandwidth width of each channel to be the same during reception and transmission of the optical repeater 200. In other words, the signal bandwidths of channels 1ch, 2ch, and 3ch during transmission by the optical repeater 200 are Δf1, Δf2, and Δf3, respectively, which are the same as the signal bandwidths during reception.

[0049] FIG. 9C is a third diagram showing an outline of carrier frequency setting for channel switching instructed by the carrier frequency selection unit 150. Assume that the optical repeater 200 receives signals in the frequency bands of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The carrier frequencies of the channels are f1, f2, and f3, respectively, and the signal bands are Δf1, Δf2, and Δf3, respectively. The carrier frequency control unit 150 sets the carrier frequency of each channel so that the order of the frequency values ​​in the frequency domain of each channel received by the optical repeater 200 is reversed, and a frequency offset Δf is uniformly applied to each channel to produce an output signal. By setting the carrier frequencies of the channels 1ch, 2ch, and 3ch of the output signal of the optical repeater 200 to f3+Δf, f2+Δf, and f1+Δf, the order of the frequency values ​​of each channel is reversed, and an optical signal with a uniform frequency offset is transmitted. This allows a transmission signal having a band different from the band of the optical signal received by the optical repeater 200 to be transmitted to the path. This makes it possible to apply the present invention to a wavelength conversion repeater system in which the optical repeater converts the wavelengths of the received and transmitted signals.

[0050] In the optical network 51, a multi-channel optical signal is relayed by a plurality of optical repeaters 200 via an optical transmission line 3. When a plurality of optical repeaters 200 in the optical network 51 change the channel order for a given channel of the optical signal, the receiving terminal device 40 is notified of the carrier frequency at the receiving end of the given channel.

[0051] 8, an optical repeater 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. 8, in order to transmit and receive multiple optical channels, the optical repeater 200 includes an optical switch unit 300 and a transceiver unit 310, and the transceiver unit 310 includes multiple optical transceivers 201, similar to the basic example of FIG. 2. That is, the node control unit 202 can control the optical switch unit 300 and the transceiver unit 310 (multiple optical transceivers 201 (corresponding to the optical transceiver 311 of FIG. 3)).

[0052] The optical transceiver 201 includes a coherent receiving front-end unit 210 , a coherent transmitting front-end unit 220 , a digital signal processing unit 230 , a receiving light source 240 , a transmitting light source 250 , an ADC 260 , and a DAC 270 .

[0053] The receiving light source 240 generates local light r1 of a wavelength (frequency) set by the node control unit 202, and outputs the generated local light r1 to the coherent receiving front-end unit 210. The transmitting light source 250 generates transmission light r2 of a wavelength (frequency) set by the node control unit 202, and outputs the generated transmission light r2 to the coherent transmitting front-end unit 220.

[0054] The frequency (wavelength) of the local light r1 is the frequency (carrier frequency) of the received input optical signal SO1, and the frequency of the transmitted light r2 is the frequency of the transmitted output optical signal SO2. The carrier frequencies of the local light r1 and r2 are determined based on carrier frequency information acquired by the node control unit 202 from the carrier frequency control unit 150.

[0055] The coherent receiver front-end unit 210 and the coherent transmitter front-end unit 220 have the same configuration as in Fig. 3. The coherent receiver front-end unit 210 is an optical / electrical converter that converts an optical signal into an electrical signal, and is a coherent detector that performs coherent detection. The coherent receiver front-end unit 210 coherently detects the input optical signal SO1 (received optical signal) based on the local light r1, and outputs the generated analog signal SA1 (first analog electrical signal).

[0056] An 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 (first digital electrical signal).

[0057] A DAC (Digital / Analog Converter) 270 performs digital to analog conversion on the digital signal SD2 (second digital electric signal) that has been signal-processed by the digital signal processor 230, and outputs the converted analog signal SA2 (second analog electric signal).

[0058] The coherent transmission front-end unit 220 is an electrical / optical conversion unit that converts an electrical signal into an optical signal, and a coherent modulation unit that performs coherent modulation. The coherent transmission front-end unit 220 coherently modulates the analog signal SA2 that has been DA converted by the DAC 270 based on the transmission light r2, and outputs the generated output optical signal SO2 (transmission optical signal).

[0059] 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 an IX signal of an I component (in-phase component) of an X polarization, a QX signal of a Q component (orthogonal component) of an X polarization, an IY signal of an I component of a Y polarization, and a QY signal of a Q component of a Y polarization.

[0060] The digital signal processor 230 performs digital signal processing on the digital signal SD1 converted by the ADC 260, and outputs a digital signal SD2 after the digital signal processing. The digital signal processor 230 is a digital circuit that performs predetermined digital signal processing for compensating for signal quality. The digital signal processor 230 performs digital signal processing on all or part of the IX signal, QX signal, IY signal, and QY signal (X polarization or Y polarization) of the four lanes.

[0061] The digital signal processing unit 230 performs only specific signal processing, without performing processing involving a large delay such as code error correction (data recovery). This makes it possible to compensate for the required signal quality while suppressing signal delay. In this embodiment, the digital signal processing unit 230 includes a wavelength dispersion compensation unit 231 (corresponding to the wavelength dispersion compensation unit 23 in FIG. 6) that performs wavelength dispersion processing, and a phase conjugation processing unit 232 (corresponding to the phase conjugation unit 22 in FIG. 6) that performs phase conjugation processing.

[0062] The chromatic 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. For this reason, for example, the chromatic 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, the chromatic dispersion can be compensated by an FIR filter with the inverse characteristics. While an FIR filter performs time domain equalization (TDE) that equalizes the received signal in the time delay domain, the same characteristics may be realized by frequency domain equalization (FDE) that equalizes in the frequency domain. By configuring the chromatic dispersion compensation unit by FDE, the circuit scale can be reduced compared to an FIR filter.

[0063] In addition to compensating for transmission path wavelength dispersion, the chromatic dispersion compensating unit 231 may also compensate for bandwidth degradation due to characteristic degradation and characteristic variations of analog electrical circuits in each of the four lanes of the IX signal, QX signal, IY signal, and QY signal, amplitude variations of the four lanes, skew and crosstalk of the four lanes, etc.

[0064] Fig. 10 shows another example of the configuration of each device in the optical network system according to an embodiment of the present disclosure. As shown in Fig. 10, the delay adjustment unit 233 of the digital signal processing unit 230 of the optical repeater 200 may provide a delay to correct the variation in the optical path length inside the optical repeater when transmitting and receiving multiple optical signals and the timing deviation generated by the ADC, DCA, and digital signal processing.

[0065] Fig. 11 shows an example of the configuration of the chromatic dispersion compensator 231 configured by FDE processing. The chromatic dispersion compensator 231 in Fig. 11 is an example of the configuration of overlap FDE, and includes an overlap adding unit 411, a fast Fourier transform unit 412, a frequency response multiplying unit 413, an inverse fast Fourier transform unit 414, and an overlap removing unit 415.

[0066] The node control unit 202 sets the amount of chromatic dispersion compensation notified by the control device 100 in the chromatic dispersion compensation unit 231 in the digital signal processing unit 230. When the chromatic dispersion compensation unit 231 is configured with an FDE as shown in Fig. 9, the node control unit 202 sets the coefficient of the frequency response multiplication unit 413 in Fig. 9 in accordance with the amount of chromatic dispersion compensation notified by the control device 100 and the carrier frequency and signal band of each channel.

[0067] The overlap adding unit 411 overlaps a part of the preceding and following signals with respect to the input signal (digital signal). After that, the fast Fourier transform unit 412 transforms the overlapped signal into a frequency domain signal by fast Fourier transform (FFT).

[0068] The frequency response multiplier 413 performs equalization by multiplying the amount of chromatic dispersion compensation notified from the control device 100 by the frequency response of chromatic dispersion in the transmission line according to the carrier frequency and signal band of each channel.

[0069] FIG. 12A is a first diagram showing an overview of determining the frequency response coefficient of the transmission line chromatic dispersion used in the frequency response multiplication unit 413, which is equalized according to the notified chromatic dispersion compensation amount and the carrier frequency and signal band of each channel. Assume that the optical repeater 200 receives optical signals of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The carrier frequencies of each channel are f1, f2, and f3, and the respective frequency bands are Δf1, Δf2, and Δf3. The curve L at the bottom of FIG. 12A indicates the phase of the chromatic dispersion frequency response. The frequency response multiplication unit 413 multiplies the signal input from the fast Fourier transform unit 412 by the frequency response coefficient converted from the phase component to a complex component. Note that a complex coefficient to be used for the frequency application coefficient can be obtained by calculating exp(iθ) from the phase component θ as shown by the curve L at the bottom of FIG. 12A. Assume that the digital signal processing unit 230 first performs phase conjugation processing and then performs chromatic dispersion compensation processing. The frequency response multiplication unit 413 for each channel of the optical repeater 200 multiplies the signal of each channel input from the fast Fourier transform unit 412 by the wavelength dispersion frequency response of each frequency band of the corresponding channel, based on frequency inversion by phase conjugation and the wavelength dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal.

[0070] More specifically, the frequency response multiplication unit 413 specifies a coefficient in the Δf3 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 1ch, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 1ch by the coefficient. The frequency response multiplication unit 413 also specifies a coefficient in the Δf2 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 2ch, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 2ch by the coefficient. The frequency response multiplication unit 413 also specifies a coefficient in the Δf1 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 3ch, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 3ch by the coefficient. This allows for frequency component inversion due to phase conjugation processing.

[0071] FIG. 12B is a second diagram showing an overview of determining the frequency response coefficient of the transmission line chromatic dispersion used in the frequency response multiplication unit 413, which performs equalization according to the notified chromatic dispersion compensation amount and the carrier frequency and signal band of each channel. Assume that the optical repeater 200 receives optical signals of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The carrier frequencies of each channel are f1, f2, and f3, and the frequency bands are Δf1, Δf2, and Δf3. The curve L at the bottom of FIG. 12B indicates the phase of the chromatic dispersion frequency response, and the frequency response multiplication unit 413 multiplies the signal input from the fast Fourier transform unit 412 by the frequency response coefficient converted from the phase component to the complex component. Assume that the digital signal processing unit 230 first performs chromatic dispersion compensation processing, and then performs phase conjugation processing.

[0072] The frequency response multiplication unit 413 of each channel of the optical repeater 200 multiplies the signal of each channel input from the fast Fourier transform unit 412 by the chromatic dispersion frequency response of each frequency band of the corresponding channel based on the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal. More specifically, the frequency response multiplication unit 413 specifies a coefficient in the Δf1 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation to channel 1ch, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 1ch by the coefficient. Also, the frequency response multiplication unit 413 specifies a coefficient in the Δf2 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation to channel 2ch, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 2ch by the coefficient. In addition, the frequency response multiplication unit 413 identifies a coefficient in the Δf3 region from the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 3ch, and multiplies the coefficient by the signal input from the fast Fourier transform unit 412 corresponding to channel 3ch.

[0073] As a result, when the optical repeater 200 receives a multi-channel signal, it is possible to compensate for the difference in group delay characteristics between channels, and to compensate for nonlinear distortion between channels due to phase conjugation.

[0074] Thereafter, the inverse fast Fourier transform unit 414 converts the signal into a time domain signal by an inverse fast Fourier transform (IFFT). The overlap removal unit 415 removes the overlap portion from the signal restored in the time domain and outputs the signal. When FDE is used, the amount of chromatic dispersion compensation 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.

[0075] Phase conjugation by digital signal processing finds the complex conjugate of the input digital signal. That is, the sign of the imaginary component Q in the Ix signal, Qx signal, Iy signal, and Qy signal is inverted as shown in the following equation (1).

[0076]

number

[0077] The node control unit 202 receives control information from the control device 100 and controls each unit of the optical repeater 200 based on the received control information. The node control unit 202 is an acquisition unit that acquires an optimal chromatic dispersion compensation amount according to the frequency band of each channel from the chromatic dispersion compensation amount calculation unit 130, phase conjugation processing information from the phase conjugation determination unit 140, and reception wavelength information and transmission wavelength information from the carrier frequency control unit 150. The node control unit 202 sets the frequency (wavelength) of the local light r1 for the reception light source 240 based on the acquired reception 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 calculation for the phase conjugation processing unit 232 based on the control information including an instruction to perform phase conjugation processing acquired from the control device 100. The node control unit 202 sets the chromatic dispersion compensation amount for the chromatic dispersion compensation unit 231 based on the acquired optimal chromatic dispersion compensation amount.

[0078] 13 shows an example of the operation of the optical network system according to an embodiment of the present disclosure. As shown in FIG. 13, first, the network management unit 110 of the control device 100 determines the transmission line information of the optical transmission lines before and after the optical repeater 200. The carrier frequency control unit 150 determines the wavelength to be used by the optical repeater 200 (S101). The network control unit 120 of the control device 100 determines the route of the path in the optical network 51, and identifies the optical transmission lines and the optical repeater 200 on the path route. The carrier frequency control unit 150 determines the wavelength of each identified optical transmission line, thereby determining the wavelengths of the front and rear stages (before and after conversion) of each optical repeater 200, i.e., the wavelengths of the optical signals transmitted and received by the optical repeater 200. The network control unit 120 and the carrier frequency control unit 150 output the receiving wavelength information and the transmitting wavelength information of the optical repeater 200 to the chromatic dispersion compensation amount calculation unit 130, the phase conjugate determination unit 140, and the carrier frequency control unit 150 according to the determined wavelength, and also output the transmission line information (distance) of the optical transmission lines before and after the optical repeater 200 to the chromatic dispersion compensation amount calculation unit 130 and the phase conjugate determination unit 140. When a path includes multiple optical repeaters 200, the following process is performed for each optical repeater.

[0079] Next, the chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the chromatic dispersion characteristics in the upstream and downstream optical transmission paths (S102). The chromatic dispersion compensation amount calculation unit 130 calculates the chromatic dispersion characteristics in the upstream and downstream optical transmission paths of the optical repeater 200 based on the reception wavelength information and transmission wavelength information acquired from the network control unit 120 and the carrier frequency control unit 150 and the transmission path information (distance) of the upstream and downstream optical transmission paths of the optical repeater 200. Note that when the transmission information includes the structure, type, and transmission characteristics of the optical fiber, the chromatic dispersion characteristics may be determined based on this information.

[0080] For example, the chromatic dispersion characteristic is the slope of the amount of chromatic dispersion accumulated with respect to the distance of the optical transmission path (the chromatic dispersion characteristic according to the distance). Since the slope of this chromatic dispersion amount varies depending on the wavelength, a table that associates the wavelength (or wavelength band) with the slope of the amount of chromatic dispersion may be stored in advance. The chromatic dispersion compensation amount calculation unit 130 may refer to this table to determine the chromatic dispersion characteristic corresponding to the wavelength.

[0081] Next, the chromatic dispersion compensation amount calculation unit 130 of the control device 100 determines the optimal chromatic dispersion compensation amount in the optical repeater 200 (S103). The chromatic dispersion compensation amount calculation unit 130 determines the optimal chromatic dispersion compensation amount in the optical repeater 200 based on the chromatic dispersion characteristics of the optical transmission lines in the front and rear stages of the optical repeater 200 and the transmission line information of the optical transmission lines in the front and rear stages. The chromatic dispersion compensation amount calculation unit 130 obtains the amount of chromatic dispersion accumulated in the optical transmission line in the front stage (receiving side), obtains the amount of chromatic dispersion accumulated in the optical transmission line in the rear stage (transmitting side), and determines the optimal chromatic dispersion amount based on the chromatic dispersion amount in the front stage and the chromatic dispersion amount in the rear stage. In particular, the chromatic dispersion compensation amount calculation unit 130 determines the optimal chromatic dispersion amount based on the amount of chromatic dispersion accumulated between the transmitting terminal device 30 and the optical repeater 200 and the amount of chromatic dispersion accumulated between the optical repeater 200 and the receiving terminal device 40. For example, the chromatic dispersion compensation amount calculation unit 130 determines the amount of chromatic dispersion accumulated in the optical transmission line at the upstream stage based on the chromatic dispersion characteristics and transmission line information (distance) of the optical transmission line at the upstream stage of the optical repeater 200, and determines the amount of chromatic dispersion accumulated in the optical transmission line at the downstream stage based on the chromatic dispersion characteristics and transmission line information of the optical transmission line at the downstream stage of the optical repeater 200. Note that in this example, the chromatic dispersion compensation amount calculation unit 130 determines the amount of chromatic dispersion compensation based on the chromatic dispersion characteristics and transmission line information, but since the chromatic dispersion characteristics correspond to the wavelength information, the chromatic dispersion compensation amount may be determined based on the wavelength information and the transmission line information. That is, the chromatic dispersion compensation amount calculation unit 130 may determine the amount of chromatic dispersion compensation in the multiple optical repeaters 200 constituting the path based on the wavelength information and transmission line information in the path.

[0082] Next, the phase conjugate determination unit 140 of the control device 100 determines the optimal phase conjugate processing in the optical repeater 200 (S104). The phase conjugate determination unit 140 determines the optimal phase conjugate processing in the optical repeater 200 based on the number of optical paths between the transmitting terminal device 30 and the receiving terminal device 40 in the optical network 51 and the number of optical repeaters 200.

[0083] Next, the control device 100 notifies the optical repeater 200 of the route information, receiving wavelength information, and transmitting wavelength information determined in S101, the optimal phase conjugate processing information determined in S104, and the optimal amount of chromatic dispersion compensation determined in S103 (S105).

[0084] Next, the node control unit 202 of the optical repeater 200 sets the wavelength of the wavelength information notified from the control device 100, the phase conjugate processing information, and the optimal amount of chromatic dispersion compensation (S106). The node control unit 202 sets the wavelength of the acquired reception wavelength information to the reception light source 240, sets the wavelength of the acquired transmission wavelength information to the transmission light source 250, sets the acquired phase conjugate processing information to the phase conjugate processing unit 232, and sets the acquired optimal amount of chromatic dispersion compensation to the chromatic dispersion compensation unit 231.

[0085] Next, the optical repeater 200 executes wavelength conversion, phase conjugation, and chromatic dispersion compensation (S107). The receiving light source 240 generates local light r1 of a set wavelength (frequency), and the transmitting light source 250 generates transmitting light r2 of a set wavelength, thereby performing wavelength conversion in the optical transceiver 201. The phase conjugation processor 232 performs phase conjugation by phase conjugation, and the chromatic dispersion compensation unit 231 performs chromatic dispersion compensation by digital signal processing on the signal after the phase conjugation based on the set compensation amount.

[0086] 14A and 14B show specific examples of phase conjugation and chromatic dispersion compensation by the control method according to an embodiment of the present disclosure. In this embodiment, the optical repeater 200 performs phase conjugation on the nonlinear distortion accumulated in the upstream optical transmission path in the optical signal received by the optical repeater 200. This makes it possible to cancel nonlinear distortion in the downstream optical transmission path of the optical signal transmitted from the optical repeater 200 at the receiving end. In order to obtain such an effect, the optical repeater 200 in this embodiment determines an optimal amount of chromatic dispersion compensation that maximizes the nonlinear distortion cancellation effect. The optimal amount of chromatic dispersion compensation in this example is a compensation amount calculated based on the amount of chromatic dispersion in the upstream transmission path and the downstream transmission path for the optical repeater 200. Also, in this example, the digital signal processor 230 of the optical repeater 200 determines an optimal amount of chromatic dispersion compensation when performing chromatic dispersion compensation after phase conjugation. When the digital signal processor 230 performs phase conjugation after chromatic dispersion compensation, an optimal amount of chromatic dispersion compensation may be determined based on the amount of chromatic dispersion in the upstream and downstream transmission paths. In this example, the digital signal processor 230 first performs phase conjugation and then performs chromatic dispersion compensation.

[0087] As shown in FIG. 14A, in this example, one optical repeater 200 is arranged on the route of the path between the transmitting terminal device 30 and the receiving terminal device 40. The transmitting terminal device 30 and the optical repeater 200 are connected via an optical transmission line 3a (first optical transmission line), and the optical repeater 200 and the receiving terminal device 40 are connected via an optical transmission line 3b (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 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. For example, the wavelengths λ1 and λ2 may both be in the C-band wavelength band, or may be different, such as the C-band wavelength band and the L-band wavelength band, or may both be in the L-band wavelength band. The optical repeater 200 converts a received optical signal having a wavelength of λ1 into an optical signal having a wavelength of λ2, and transmits the converted optical signal having the wavelength of λ2.

[0088] As shown in FIG. 14B, in the optical transmission line 3a at the front stage, the wavelength of the optical signal is λ1, so the chromatic dispersion compensation amount calculation unit 130 of the control device 100 determines the gradient DS1 of the chromatic dispersion amount in the optical transmission line 3a according to the wavelength λ1. The gradient DS1 of the chromatic dispersion amount in the optical transmission line 3a may be read from a storage means such as a database. The chromatic dispersion compensation amount calculation unit 130 of the control device 100 uses the gradient DS1 of the chromatic dispersion amount and the effective nonlinear distance Leff1 in the optical transmission line 3a to determine the accumulated chromatic dispersion amount M1 (=DS1×Leff1) at the effective nonlinear distance Leff1 in the optical transmission line 3a at the front stage. The nonlinear effect is an effect that depends on the optical signal intensity, and the optical intensity in the transmission line decreases according to an exponential function characterized by the propagation loss constant, so it is sufficient to consider the nonlinear effect only in the region where the optical intensity is large. The effective nonlinear distance Leff is defined as the distance in which the nonlinear effect is considered, and Leff is given by the following formula (2) using the length L and the propagation loss constant α in the optical fiber.

[0089]

number

[0090] In addition, in the latter optical transmission line 3b, the wavelength of the optical signal is λ2, so the chromatic dispersion compensation amount calculation unit 130 of the control device 100 determines the slope DS2 of the chromatic dispersion amount in the optical transmission line 3b according to the wavelength λ2. The slope DS2 of the chromatic dispersion amount in the optical transmission line 3b may be read from a storage means such as a database. The chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the accumulated chromatic dispersion amount M2 in the effective nonlinear distance Leff2 in the latter optical transmission line 3b as M2=-M1 under the condition that the accumulated chromatic dispersion amount M2 has a different sign from the accumulated chromatic dispersion amount M1 in the effective nonlinear distance Leff1 in the former optical transmission line 3a. Then, the chromatic dispersion compensation amount calculation unit 130 calculates the accumulated chromatic dispersion amount M3 in the transmission signal of the optical repeater. M3 can be calculated by M3=M2+DS2×Leff2=DS1×Leff1+DS2×Leff2.

[0091] The chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the cumulative chromatic dispersion compensation amount M5 for the optical repeater 200 to compensate for chromatic dispersion using phase conjugation by using M5=M4×2.

[0092] The chromatic dispersion compensation amount calculation unit 130 of the control device 100 obtains the difference M6 between the accumulated chromatic dispersion amount M3 and the accumulated chromatic dispersion compensation amount M5, and transmits the difference M6 to the optical repeater 200 as an optimal chromatic dispersion compensation amount. The control device 100 also transmits control information including an instruction to perform phase conjugation to the optical repeater 200. As a result, the node control unit 202 of the optical repeater 200 instructs the phase conjugation processing unit 232 to perform phase conjugation calculation based on the control information including an instruction to perform the acquired phase conjugation, as described with reference to Figs. 9 and 11. The phase conjugation processing unit 232 performs phase conjugation calculation. The node control unit 202 of the optical repeater 200 also sets the chromatic dispersion compensation amount M6 notified from the control device 100 to the chromatic dispersion compensation unit 231 in the digital signal processing unit 230, as described with reference to Fig. 9. That is, when the chromatic dispersion compensator 231 is configured with the FDE as shown in Fig. 9, the node controller 202 sets the transfer function coefficient of the inverse transfer function multiplier 413 in Fig. 9 according to the chromatic dispersion compensation amount M6 notified from the control device 100. As a result, the optical repeater 200 calculates the accumulated chromatic dispersion M3 (M3 = M4 - M5 - M6) after calculating the accumulated chromatic dispersion compensation amount M5 using the phase conjugation processing of the phase conjugator 232 and performing chromatic dispersion compensation using the chromatic dispersion compensation amount M6 of the chromatic dispersion compensator 231 for the downstream optical transmission line 3b, and outputs an optical signal with the accumulated chromatic dispersion M3 (Fig. 14B). As a result, the nonlinear effect in the receiving terminal device 40 is suppressed.

[0093] The optical repeater 200 can calculate the accumulated chromatic dispersion amount M3 by M3=M2+DS2×Leff2=DS1×Leff1+DS2×Leff2 without performing phase conjugation. Therefore, the chromatic dispersion compensation unit 231 of the optical repeater 200 may calculate the accumulated chromatic dispersion amount M3 and output an optical signal with the accumulated chromatic dispersion M3 without performing phase conjugation (FIG. 14B). In the explanation of FIGS. 12A and 12B, for convenience of explanation, it is explained that an optical signal with a wavelength λ1 is transmitted in the optical transmission line 3a and an optical signal with a wavelength λ2 is transmitted in the optical transmission line 3b, but a multi-channel optical signal with a plurality of wavelengths λ (frequency bands) may be transmitted in the optical transmission line 3a and a multi-channel optical signal with a plurality of wavelengths λ (frequency bands) may be transmitted in the optical transmission line 3b.

[0094] FIG. 14C is a diagram showing an outline of the phase conjugate processing. As shown in FIG. 14C, in a certain span in the optical network 51 (between the transmitting terminal device 30 and the network device such as the optical repeater device 200 in FIG. 14C), nonlinear distortion of the transmission signal occurs as signal degradation due to nonlinear effects (1111 in FIG. 14C). The optical repeater device 200 performs phase conjugation processing (inversion of the optical signal) (1112 in FIG. 14C). This provides an offsetting effect of nonlinear distortion using phase conjugation in the span following the optical repeater device 200 (between the optical repeater device 200 and the receiving terminal device 40), and can reduce signal degradation (nonlinear distortion) in the receiving terminal device 40 (1113 in FIG. 14C). In addition, when the optical repeater device 200 receives a multi-channel signal, it performs wavelength dispersion compensation optimal to the signal band of each channel, thereby enhancing the offsetting effect of nonlinear distortion in the receiving terminal device 40.

[0095] The processing in the control device 100 described above is one aspect of processing for determining the amount of chromatic dispersion compensation to be performed in the optical repeater 200 based on wavelength information of optical signals transmitted and received by the optical repeater 200 constituting the optical network in the path of the optical network and transmission line information of the optical transmission line connected to the optical repeater 200, and for determining the phase conjugation processing in the optical repeater 200 based on the wavelength information and the transmission line information.

[0096] In addition, a portion of the processing in the control device 100 is one form of processing to send an instruction to the optical repeater 200 to perform phase conjugation processing to calculate the complex conjugate of the optical signal received by the optical repeater 200 based on the accumulated chromatic dispersion amount M4 of the optical signal.

[0097] In addition, a portion of the processing in the control device 100 is one aspect of processing to calculate a first accumulated chromatic dispersion amount M1 in a first effective nonlinear distance (Leff1) based on a transmitting network device in a first optical transmission path (previous path) between the optical repeater 200 and a transmitting network device that transmits an optical signal received by the optical repeater 200, among the optical transmission paths connected to the optical repeater 200.

[0098] In addition, a part of the processing in the control device 100 is one aspect of processing to calculate a second accumulated chromatic dispersion amount (M2) of the optical signal in a second effective nonlinear distance (Leff2) based on the optical signal in a second optical transmission path (back-stage path) between the optical repeater 200 and a network device on the receiving side of the optical signal transmitted by the optical repeater 200, among the optical transmission paths connected to the optical repeater 200, and which has the opposite sign (multiplied by minus 1) to the first accumulated chromatic dispersion amount.

[0099] Further, a part of the processing in the control device 100 is one aspect of processing for calculating a chromatic dispersion compensation amount (M6) indicating the difference between the chromatic dispersion amount (M3) at the time of transmission in the optical repeater 200 of the optical signal when the accumulated chromatic dispersion amount of the optical signal becomes the second accumulated chromatic dispersion amount (M2) at the second effective nonlinear distance (Leff2) based on a statistical value (DS2) of the transition of the accumulated chromatic dispersion amount of the optical signal according to the distance in the second optical transmission path, and the chromatic dispersion amount (M5) which is the result of the complex conjugation.

[0100] The above-mentioned processing of the optical repeater 200 is one aspect of processing in which chromatic dispersion compensation processing is performed on an electrical signal based on a received optical signal based on the chromatic dispersion compensation amount (M6), and phase conjugation processing is performed on an electrical signal based on a received optical signal based on phase conjugation processing information acquired from the control device 100.

[0101] In addition, a part of the processing in the optical repeater 200 described above is one aspect of processing for performing phase conjugate processing based on the amount of accumulated chromatic dispersion of an optical signal received by the optical repeater and an instruction to perform phase conjugate processing for calculating the complex conjugate of the optical signal.

[0102] Furthermore, a part of the processing in the optical repeater 200 described above is one aspect of processing for determining the amount of chromatic dispersion (M3) of an optical signal to be transmitted to a receiving network device based on the amount of chromatic dispersion (M5) resulting from the complex conjugation after phase conjugation processing and the amount of chromatic dispersion compensation (M6) acquired from the control device 100.

[0103] Fig. 15 shows another example of the amount of chromatic dispersion compensation by the control method according to an embodiment of the present disclosure. Unlike Fig. 14B, in this example, as shown in Fig. 15, the transmitting terminal device 30 transmits an optical signal having an accumulated chromatic dispersion amount M10 to the optical transmission line 3a. Note that when the transmitting terminal device 30 is an optical repeater device 200 in the optical network 51, dispersion such as the accumulated chromatic dispersion amount M10 may occur in the optical signal transmitted by the transmitting terminal device 30.

[0104] 15, in the optical transmission line 3a upstream of the optical repeater 200, the wavelength of the optical signal is λ1, so the control device 100 determines the gradient DS1 of the amount of chromatic dispersion in the optical transmission line 3a according to the wavelength λ1. The control device 100 uses the effective nonlinear distance Leff1 to obtain the amount of accumulated chromatic dispersion M11 (=DS1×Leff1+M10) in the effective nonlinear distance Leff1 in the optical transmission line 3a upstream.

[0105] In the latter optical transmission line 3b, the wavelength of the optical signal is λ2, so the control device 100 determines the slope DS2 of the chromatic dispersion amount in the optical transmission line 3b according to the wavelength λ2. The control device 100 obtains the accumulated chromatic dispersion amount M13 (=DS1×Leff1+DS2×Leff2+M10) in the transmission signal of the optical repeater under the condition that the accumulated chromatic dispersion amount M12 in the effective nonlinear distance Leff2 in the latter optical transmission line 3b has a sign opposite to that of the accumulated chromatic dispersion amount M11 in the effective nonlinear distance Leff1 in the former optical transmission line 3a. The control device 100 obtains the phase conjugate compensation amount M15 (=M14×2) compensated by the phase conjugation in the optical repeater 200.

[0106] The control device 100 obtains a difference M16 between M13 and M15, and sets M6 as an optimal amount of chromatic dispersion compensation in the optical repeater 200. The control device 100 sets the optical repeater 200 to perform phase conjugation processing.

[0107] As described above, in this embodiment, in the optical repeater 200 that performs wavelength conversion on a channel-by-channel basis, the analog signal output from the coherent receiving front-end unit 210 is converted to a digital signal by the ADC, and after digital signal processing, is converted back to an analog signal by the DAC, and is then folded back and relayed to the coherent transmitting front-end unit 220. At this time, the digital signal processing unit 230 performs phase conjugation processing. At this time, the digital signal processing unit 230 compensates for chromatic dispersion distortion occurring in the optical fiber transmission line based on the transmission line length of the network path (transmission line) and the signal band and carrier frequency of the signal channel. Also, the coherent transmitting front-end unit 220 sets each carrier frequency so that the order of each channel is interchanged in the frequency domain.

[0108] Specifically, the control device 100 calculates an optimal chromatic dispersion compensation amount in the frequency band of each channel to be compensated by the optical repeater so that the accumulated chromatic dispersion amount in the effective nonlinear distance in the transmission path at the front stage and the accumulated chromatic dispersion amount in the effective nonlinear distance in the transmission path at the rear stage have opposite signs, and the optical repeater 200 performs phase conjugation and chromatic dispersion compensation based on the calculated optimal chromatic dispersion compensation amount, the signal band of the signal channel, and the carrier frequency. This allows the nonlinear distortion accumulated in the front optical transmission path at the receiving end of the optical repeater 200 to be offset by the optical transmission at the rear optical transmission, maximizing the effect of suppressing nonlinear distortion in the receiving terminal device 40. Furthermore, even if the transmission signal by the transmitting terminal device 30 contains an unnecessary amount of dispersion as shown in FIG. 12, the optical repeater 200 can set an appropriate chromatic dispersion amount and compensate for the nonlinear distortion. Furthermore, by setting the carrier frequency so that the order of each channel is interchanged in the frequency domain in the coherent transmission front end unit 220, the inter-channel nonlinear distortion can be reduced.

[0109] (Embodiment 2) Next, a second embodiment will be described with reference to the drawings. In this embodiment, the configuration and basic operation of the optical network system are similar to those of the first embodiment. Fig. 16A and Fig. 16B show a specific example of the amount of chromatic dispersion compensation by the control method in one embodiment of the present disclosure. In this embodiment, the number of spans in the optical network is an odd number equal to or greater than 3, and in particular, an example in which the number of spans is 3 will be described.

[0110] As shown in FIG. 16A, an optical repeater 200a (first optical repeater) and an optical repeater 200b (second optical repeater) are arranged on the route of the path between the transmitting terminal device 30 and the receiving terminal device 40. The transmitting terminal device 30 and the optical repeater 200a are connected via an optical transmission line 3a (first optical transmission line), the optical repeater 200a and the optical repeater 200b are connected via an optical transmission line 3b (second optical transmission line), and the optical repeater 200b and the receiving terminal device 40 are connected via an optical transmission line 3c (third optical transmission line). For example, the distance L1 of the optical transmission line 3a, the distance L2 of the optical transmission line 3b, and the distance L3 of the optical transmission line 3c may be different or the same. An optical signal with a wavelength λ1 is transmitted through the optical transmission line 3a, an optical signal with a wavelength λ2 is transmitted through the optical transmission line 3b, and an optical signal with a wavelength λ3 is transmitted through the optical transmission line 3c. Multi-channel optical signals of multiple wavelengths λ (frequency bands) may be transmitted through optical transmission path 3a, multi-channel optical signals of multiple wavelengths λ (frequency bands) may be transmitted through optical transmission path 3b, and channel optical signals of multiple wavelengths λ (frequency bands) may be transmitted through optical transmission path 3c.

[0111] In the case where the total number of spans is an odd number of three or more, such as three or more in embodiment 2, the control of the control device 100 using the method of embodiment 1 is applied to combinations of two spans, such as optical transmission line 3a and optical transmission line 3b, and for one of the remaining optical transmission lines 3, such as optical transmission line 3c, the control device 100 sets, in the last optical repeater 200 (optical repeater 200b in this embodiment) constituting the optical network 51, an optimal dispersion compensation amount that can suppress nonlinear distortion when optically transmitting one span in that optical transmission line 3 (optical transmission line 3c in this embodiment).

[0112] 16B, the optical repeater 200a performs phase conjugation and calculates the amount of chromatic dispersion compensation M26 to which the first embodiment is applied, based on the control by the control device 100. The amount of chromatic dispersion M26 after compensation in the optical repeater 200a is determined by the same method as in the first embodiment. The control device 100 sets the amount of dispersion compensation M26 to which the first embodiment is applied in the optical repeater 200a to the optical repeater 200a. The control device 100 also sets the optical repeater 200a to perform phase conjugation.

[0113] Further, under the control of the control device 100, the optical repeater 200b compensates for an optimal amount of chromatic dispersion compensation that minimizes the nonlinear effect in one span of optical transmission in the optical transmission line 3c. The control device 100 determines the slope DS3 of the chromatic dispersion amount in the optical transmission line 3c according to the wavelength λ3. The control device 100 calculates the chromatic dispersion M28 (=DS3×L3′) of the transmission signal of the optical repeater 200b under the condition that the accumulated chromatic dispersion of the transmission signal in the optical transmission line 3c becomes zero in the effective nonlinear distance L3′. The control device 100 calculates the accumulated chromatic dispersion amount M27 accumulated in the optical transmission line 3b.

[0114] The control device 100 sets the amount of chromatic dispersion to be compensated for by the optical repeater 200b as M27+M28 from the calculated chromatic dispersion amounts M27 and M28 in the optical repeater 200b. Also, the control device 100 sets the optical repeater 200b so as not to perform phase conjugation processing.

[0115] When the total number of spans is an odd number N equal to or greater than 5, similar to the case where the total number of spans is 3 as shown in the second embodiment, the control device 100 identifies a combination consisting of one optical repeater and two optical transmission lines that allows the first embodiment to be implemented. The control device 100 sets phase conjugation and optimal chromatic dispersion compensation according to the first embodiment for each identified combination of optical repeaters. For one remaining optical transmission line out of the N spans, the control device 100 sets the optimal amount of chromatic dispersion compensation in the optical repeater that minimizes nonlinear distortion in transmission of one span.

[0116] In each optical repeater 200, a frequency flip process may be performed on a specified channel as in the other embodiments described above.

[0117] As described above, in this embodiment, nonlinear distortion at the receiving end is suppressed in the case of multiple spans, particularly an odd number of spans. Specifically, combinations consisting of one optical repeater and two optical transmission lines are set so that the first embodiment can be implemented, and phase conjugation and chromatic dispersion compensation according to the first embodiment are set for the optical repeater in each combination. For the remaining optical transmission lines, the optimal amount of chromatic dispersion compensation shown in the second embodiment is set so that nonlinear distortion in one span is minimized. Therefore, in an optical network consisting of an odd number of multiple transmission lines, the offset effect of nonlinear distortion during optical transmission using chromatic dispersion compensation can be maximized, and signal quality at the receiving end can be improved.

[0118] (Embodiment 3) Next, a third embodiment will be described with reference to the drawings. In this embodiment, the configuration and basic operation of the optical network system are the same as those in the first embodiment. Fig. 17A and Fig. 17B show a specific example of the amount of chromatic dispersion compensation by the control method in an embodiment of the present disclosure. In this embodiment, the number of spans in the optical network is an even number equal to or greater than four, and an example in which the number of spans is four will be described.

[0119] As shown in FIG. 17A, an optical repeater 200a (first optical repeater), an optical repeater 200b (second optical repeater), and an optical repeater 200c are arranged on the route of the path between the transmitting terminal device 30 and the receiving terminal device 40. The transmitting terminal device 30 and the optical repeater 200a are connected via an optical transmission line 3a (first optical transmission line), the optical repeater 200a and the optical repeater 200b are connected via an optical transmission line 3b (second optical transmission line), the optical repeater 200b and the optical repeater 200c are connected via an optical transmission line 3c (third optical transmission line), and the optical repeater 200c and the receiving terminal device 40 are connected via an optical transmission line 3d (fourth optical transmission line). For example, the distance L1 of the optical transmission line 3a, the distance L2 of the optical transmission line 3b, the distance L3 of the optical transmission line 3c, and the distance L4 of the optical transmission line 3d may be different or the same. The optical transmission line 3a transmits an optical signal of wavelength λ1, the optical transmission line 3b transmits an optical signal of wavelength λ2, the optical transmission line 3c transmits an optical signal of wavelength λ3, and the optical transmission line 3d transmits an optical signal of wavelength λ4. Of these optical wavelengths λ1 to λ4, two or more of the wavelengths λ may be the same or different. The optical transmission line 3a may transmit multi-channel optical signals of multiple wavelengths λ (frequency bands), the optical transmission line 3b may also transmit multi-channel optical signals of multiple wavelengths λ (frequency bands), the optical transmission line 3c may also transmit optical signals of channels of multiple wavelengths λ (frequency bands), and the optical transmission line 3d may also transmit optical signals of channels of multiple wavelengths λ (frequency bands).

[0120] As shown in FIG. 17B, in the case where the total number of spans in embodiment 3 is 4, for example, the control of the control device 100 according to embodiment 1 is applied to two spans, optical transmission lines 3a and 3b, and the control of the control device 100 according to embodiment 1 is also applied to two spans, optical transmission lines 3c and 3d.

[0121] The control device 100 sets, in the optical repeater 200a, the amount of dispersion compensation to which the control of the control device 100 according to the embodiment 1 has been applied and information for performing phase conjugation processing. That is, the control device 100 sets, in the optical repeater 200a, the optimal amount of chromatic dispersion compensation M36 obtained by applying the control of the control device 100 according to the embodiment 1 to the optical repeater 200a. The control device 100 also sets, in the optical repeater 200a, the optical repeater 200a to perform phase conjugation processing in the same manner as in the embodiment 1.

[0122] The control device 100 also sets, in the optical repeater 200c, the amount of dispersion compensation to which the control of the control device 100 according to the embodiment 1 has been applied and information for performing phase conjugation processing. That is, the control device 100 sets, in the optical repeater 200c, the optimal amount of chromatic dispersion compensation M44 found by applying the control of the control device 100 according to the embodiment 1 to the optical repeater 200c. The control device 100 also sets, in the optical repeater 200c, the optical repeater 200c to perform phase conjugation processing in the same manner as in the embodiment 1.

[0123] The control device 100 determines the gradient DS2 of the chromatic dispersion amount in the optical transmission line 3b in accordance with the wavelength λ2. The control device 100 obtains the accumulated chromatic dispersion amount M37 (=DS2×L2+M33) accumulated in the optical transmission line 3b.

[0124] The control device 100 sets the amount of chromatic dispersion to be compensated for in the optical repeater 200b as M37-M38 from the calculated chromatic dispersion amount M37 and the amount of dispersion M38 smaller than M37 possessed by the transmission signal in the optical transmission line 3c in the optical repeater 200b. The control device 100 also sets the optical repeater 200b so as not to perform phase conjugation processing.

[0125] When the total number of spans is an even number equal to or greater than six, the control device 100 sets a combination of one optical repeater and two optical transmission lines that allows the implementation of the first embodiment, as in the case of the total number of spans being four as shown in the third embodiment. The control device 100 sets the phase conjugation and optimal chromatic dispersion compensation according to the first embodiment for each combination of optical repeaters.

[0126] In each optical repeater 200, a frequency flip process may be performed on a specified channel as in the other embodiments described above.

[0127] As described above, in this embodiment, nonlinear distortion at the receiving end in the case of multiple spans, particularly an even number of spans, is compensated for. Specifically, a combination of one optical repeater and two optical transmission lines is set so that the first embodiment can be implemented, and phase conjugation and chromatic dispersion compensation according to the first embodiment are set for the optical repeater in each combination. Therefore, in an optical network consisting of an even number of transmission lines, the offset effect of nonlinear distortion during optical transmission using chromatic dispersion compensation can be maximized, and the signal quality at the receiving end can be improved.

[0128] FIG. 18 is a diagram showing another configuration of the control device. FIG. 19 is a diagram showing a process flow by a control device having another configuration. The control device 100 includes at least a chromatic dispersion compensation control unit 151 , a phase conjugate processing control unit 152 , and a carrier frequency control unit 153 .

[0129] The carrier frequency control means 153 determines the carrier frequency for transmission and reception of each channel so that the order of magnitude of the frequency values ​​of each channel of the multi-channel signal received by the optical repeater 200 is reversed (step S161). The chromatic dispersion compensation control means 151 determines the amount of chromatic dispersion compensation to be performed in the optical repeater 200 based on wavelength information of the optical signal transmitted and received by the optical repeater 200 constituting the optical network in the path of the optical network and transmission line information of the optical transmission line connected to the optical repeater 200 (step S162). The phase conjugate processing control means 152 determines the phase conjugate processing in the optical repeater 200 based on the wavelength information and the transmission line information (step S163).

[0130] FIG. 20 is a diagram showing another configuration of the optical repeater. FIG. 21 is a diagram showing a process flow in an optical repeater having another configuration. The optical repeater 200 includes at least a chromatic dispersion compensation unit 171 , a phase conjugate processing unit 172 and a carrier frequency setting unit 173 . The phase conjugate processing means 172 performs phase conjugate processing on an electrical signal based on a received optical signal, based on the acquired phase conjugate processing information (step S181). The chromatic dispersion compensation means 171 performs chromatic dispersion compensation processing on the electrical signal based on the received optical signal, based on the amount of chromatic dispersion compensation (step S182). The carrier frequency setting means 173 sets the carrier frequency for transmission of each channel based on the acquired carrier frequency (step S183). In other embodiments, the optical repeater 200 may perform part or all of the processing of the control device 100 .

[0131] FIG. 22 is a diagram showing another configuration of the optical repeater. FIG. 23 is a diagram showing a process flow in an optical repeater device having another configuration. In another embodiment, the optical repeater 200 may further include a chromatic dispersion compensation control means 191, a phase conjugate processing control means 192, and a carrier frequency control means 193, in addition to the configuration of the chromatic dispersion compensation means 171 and the phase conjugate processing means 172, as shown in FIG. 22. The carrier frequency control means 193 determines the carrier frequency at the time of transmission of each channel so that the order of the magnitude of the frequency values ​​of each channel of the multi-channel signal received by the optical repeater 200 is reversed (step S2001). The chromatic dispersion compensation control means 191 determines the amount of chromatic dispersion compensation to be performed in the optical repeater 200 based on wavelength information of the optical signal transmitted and received by the own device (optical repeater 200) constituting the optical network in the path of the optical network and transmission line information of the optical transmission line connected to the optical repeater 200 (step S2002). The phase conjugate processing control means 192 determines the phase conjugate processing in the optical repeater 200 based on the wavelength information and the transmission line information (step S2003). In this case, the chromatic dispersion compensation control means 191, the phase conjugate processing control means 192, and the carrier frequency control means 193 may perform the same processing as that of the above-mentioned control device 100. Furthermore, when the optical repeater 200 performs the processing of the chromatic dispersion compensation control means 191, the phase conjugate processing control means 192, and the carrier frequency control means 193, the optical repeater 200 may obtain, from the control device 100, information necessary for the processing, similar to that of the above-mentioned control device 100.

[0132] In another embodiment, the optical repeater 200 may include at least one of a chromatic dispersion compensation control means 191, a phase conjugate processing control means 192 and a carrier frequency control means 193 in addition to the configuration of the chromatic dispersion compensation means 171, the phase conjugate processing control means 172 and the carrier frequency setting means 173, and the remaining means may be provided in the control device 100.

[0133] The control device, optical repeater device, transmitting terminal device, and receiving terminal device in the above-mentioned embodiments are configured by hardware or software, or both, and may be configured by one piece of hardware or software, or may be configured by multiple pieces of hardware or software. Each device (control device, etc.) and each function (processing) 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. 23. For example, a program for performing the method (control method, etc.) in the embodiment may be stored in the memory 62, and each function may be realized by executing the program stored in the memory 62 by the processor 61.

[0134] These programs include instructions (or software codes) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray® disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may be transmitted on a transitory computer-readable medium or a communication medium. By way of example and not limitation, a transitory computer-readable medium or a communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0135] The control device 100, the optical repeater device 200, the transmitting terminal device 30, and the receiving terminal device 40 of this disclosure have been described above, but this disclosure is not limited to the above-mentioned embodiments. Various modifications 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. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0136] Note that some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.

[0137] (Appendix 1) An optical repeater that constitutes an optical network, and a control device that controls the optical repeater, The control device includes: a management unit for managing wavelength information of optical signals transmitted and received by the optical repeater in a path of the optical network and transmission line information of an optical transmission line connected to the optical repeater; a chromatic dispersion compensation control means for determining an amount of chromatic dispersion compensation to be performed in the optical repeater based on the wavelength information and the transmission line information; a phase conjugate processing control means for determining a phase conjugate processing in the optical repeater based on the wavelength information and the transmission line information; Equipped with The optical repeater device includes: a chromatic dispersion compensation amount acquisition unit that acquires the determined chromatic dispersion compensation amount from the control device; a phase conjugate processing acquisition means for acquiring the determined phase conjugate processing information from the control device; a phase conjugate processing means for performing a phase conjugate process on an electrical signal based on a received optical signal, based on the acquired phase conjugate processing information; a chromatic dispersion compensation unit that performs chromatic dispersion compensation processing on an electrical signal based on a received optical signal based on the acquired chromatic dispersion compensation amount; An optical network system comprising:

[0138] (Appendix 2) the chromatic dispersion compensation control means calculates an amount of accumulated chromatic dispersion in an effective nonlinear distance in the optical transmission path on the receiving side of the optical repeater and an amount of accumulated chromatic dispersion in an effective nonlinear distance in the optical transmission path on the transmitting side of the optical repeater based on the wavelength information and the transmission path information on the receiving side of the optical repeater and the wavelength information and the transmission path information on the transmitting side of the optical repeater; 2. The optical network system of claim 1.

[0139] (Appendix 3) the chromatic dispersion compensation control means determines the amount of chromatic dispersion compensation based on the amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission path on a receiving side of the optical repeater, the amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission path on a transmitting side of the optical repeater, and the amount of chromatic dispersion compensation by phase conjugation processing in the optical repeater. 3. The optical network system of claim 2.

[0140] (Appendix 4) the chromatic dispersion compensation control means determines the amount of chromatic dispersion compensation based on an accumulated chromatic dispersion amount included in a transmission signal before optical transmission in an optical transmission path on a receiving side of the optical repeater, the accumulated chromatic dispersion amount in an effective nonlinear distance in the optical transmission path on the receiving side of the optical repeater, the accumulated chromatic dispersion amount in an effective nonlinear distance in the optical transmission path on the transmitting side of the optical repeater, and the chromatic dispersion compensation amount by phase conjugation processing in the optical repeater. 4. An optical network system according to any one of claims 1 to 3.

[0141] (Appendix 5) The amount of chromatic dispersion compensation is a compensation amount obtained under the condition that the amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission line on a receiving side of the optical repeater and the amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission line on a transmitting side of the optical repeater have opposite signs. 5. An optical network system according to any one of claims 1 to 4.

[0142] (Appendix 6) In an optical network in which three or more odd number of paths are connected via the optical repeater, the chromatic dispersion compensation control means and the phase conjugation control means determine the amount of chromatic dispersion compensation and the phase conjugation process in a target optical repeater based on the wavelength information and the transmission line information in paths before and after a target optical repeater other than the optical repeater connected to the last path among the plurality of paths. 2. The optical network system of claim 1.

[0143] (Appendix 7) The wavelength dispersion compensation control means and the phase conjugate processing control means obtain, in the optical repeater, a combination of two paths, one in the front stage and one in the rear stage, and one optical repeater that repeats the path, and determine an optical repeater other than the optical repeater connected to the one remaining path as the target optical repeater. 7. An optical network system according to any one of claims 1 to 6.

[0144] (Appendix 8) the phase conjugate processing control means determines the phase conjugate processing to be performed by the optical repeater in the combination; 8. The optical network system of claim 7.

[0145] (Appendix 9) the chromatic dispersion compensation control means determines an amount of chromatic dispersion compensation in the optical repeater of the combination based on the wavelength information and the transmission line information in the two optical transmission lines of the combination; 9. The optical network system according to claim 7 or 8.

[0146] (Appendix 10) the chromatic dispersion compensation control means determines an amount of chromatic dispersion compensation in the optical repeater of the one remaining path based on the wavelength information and the transmission line information in the optical transmission line of the one remaining path; 8. The optical network system of claim 7.

[0147] (Appendix 11) the amount of chromatic dispersion compensation is a compensation amount obtained under the condition that the amount of accumulated chromatic dispersion in the effective nonlinear distance in the optical transmission line of the remaining one path becomes zero; 11. The optical network system according to claim 7.

[0148] (Appendix 12) In an optical network in which an even number of paths, equal to or greater than four, are connected via the optical repeater, the chromatic dispersion compensation control means and the phase conjugation control means determine the amount of chromatic dispersion compensation and the phase conjugation process in the optical repeater based on the wavelength information and the transmission line information in paths before and after each of the optical repeaters in the plurality of paths. 12. An optical network system according to any one of claims 7 to 11.

[0149] (Appendix 13) The chromatic dispersion compensation control means and the phase conjugate processing control means determine a combination of two optical transmission lines and one optical repeater in the optical repeater. 13. An optical network system according to any one of claims 1 to 12.

[0150] (Appendix 14) the phase conjugate processing control means determines the phase conjugate processing to be performed by the optical repeater in the combination; 14. The optical network system according to claim 7.

[0151] (Appendix 15) the chromatic dispersion compensation control means determines an amount of chromatic dispersion compensation in the optical repeater of the combination based on the wavelength information and the transmission line information in the two optical transmission lines of the combination; 15. The optical network system according to any one of claims 7 to 14.

[0152] (Appendix 16) Manage wavelength information of optical signals transmitted and received by an optical repeater in a path of an optical network, transmission path information of an optical transmission path connected to the optical repeater, and the number of paths of the optical network; determining an amount of chromatic dispersion compensation and a phase conjugation process to be performed in the optical repeater based on the wavelength information, the transmission line information, and the number of paths in the optical network; Control methods.

[0153] (Appendix 17) determining the amount of chromatic dispersion compensation and the phase conjugation process based on an amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission path on a receiving side of each optical repeater in a path of the optical network and an amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission path on a transmitting side of the optical repeater; 17. The control method according to claim 16.

[0154] (Appendix 18) Manage wavelength information of optical signals transmitted and received by an optical repeater in a path of an optical network, transmission path information of an optical transmission path connected to the optical repeater, and the number of paths of the optical network; determining an amount of chromatic dispersion compensation and a phase conjugation process to be performed in the optical repeater based on the wavelength information, the transmission line information, and the number of paths in the optical network; A control program that causes a computer to execute processing.

[0155] (Appendix 19) determining the amount of chromatic dispersion compensation and the phase conjugation process based on an amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission path on a receiving side of each optical repeater in a path of the optical network and an amount of accumulated chromatic dispersion in an effective nonlinear distance in an optical transmission path on a transmitting side of the optical repeater; 19. The program according to claim 18.

[0156] (Appendix 20) a chromatic dispersion compensation control means for determining an amount of chromatic dispersion compensation to be performed in the optical repeater based on wavelength information of an optical signal transmitted and received by the optical repeater constituting the optical network and transmission line information of an optical transmission line connected to the optical repeater; a phase conjugate processing control means for determining a phase conjugate processing in the optical repeater based on the wavelength information and the transmission line information; A control device comprising:

[0157] (Appendix 21) The phase conjugate processing control means transmits to the optical repeater an instruction to perform a phase conjugate processing for calculating a complex conjugate of the optical signal. 21. The control device according to claim 20.

[0158] (Appendix 22) The chromatic dispersion compensation control means calculating a first accumulated chromatic dispersion amount in a first effective nonlinear distance based on the transmitting network device in a first optical transmission path between the optical repeater and a transmitting network device that transmits an optical signal received by the optical repeater, among optical transmission paths connected to the optical repeater; Calculate a second accumulated chromatic dispersion amount in a second effective nonlinear distance of the optical signal in a second optical transmission line between the optical repeater and a network device on a receiving side of the optical signal transmitted by the optical repeater, the second accumulated chromatic dispersion amount being opposite in sign to the first accumulated chromatic dispersion amount, based on the optical signal in the second optical transmission line between the optical repeater and a network device on a receiving side of the optical signal transmitted by the optical repeater; The chromatic dispersion compensation amount is calculated based on a statistical value of a transition of an accumulated chromatic dispersion amount of the optical signal according to a distance in the second optical transmission path, the chromatic dispersion compensation amount indicating a difference between an amount of chromatic dispersion of the optical signal during transmission in the optical repeater when the accumulated chromatic dispersion amount of the optical signal becomes the second accumulated chromatic dispersion amount in the second effective nonlinear distance, and an amount of chromatic dispersion that is a result of the complex conjugation. 22. The control device according to claim 21.

[0159] (Appendix 23) a chromatic dispersion compensation control means for determining an amount of chromatic dispersion compensation to be performed in the local device based on wavelength information of an optical signal transmitted and received by the local device constituting the optical network and transmission line information of an optical transmission line connected to the local device in a path of the optical network; a phase conjugate processing control means for determining a phase conjugate processing in the own device based on the wavelength information and the transmission line information; An optical repeater indicating the own device that is communicatively connected to a control device comprising: a phase conjugate processing means for performing a phase conjugate process on an electrical signal based on a received optical signal, based on phase conjugate processing information acquired from the control device; a chromatic dispersion compensation unit that performs chromatic dispersion compensation processing on an electrical signal based on a received optical signal based on the chromatic dispersion compensation amount; An optical repeater device comprising:

[0160] (Appendix 24) The phase conjugate processing means performs the phase conjugate processing based on an instruction to perform the phase conjugate processing for calculating the complex conjugate of the optical signal. 24. The optical repeater device according to claim 23.

[0161] (Appendix 25) calculating a first accumulated chromatic dispersion amount in a first effective nonlinear distance based on the transmitting network device in a first optical transmission path between the optical repeater and a transmitting network device that transmits an optical signal received by the optical repeater, among optical transmission paths connected to the optical repeater; Calculate a second accumulated chromatic dispersion amount in a second effective nonlinear distance of the optical signal in a second optical transmission line between the optical repeater and a network device on a receiving side of the optical signal transmitted by the optical repeater, the second accumulated chromatic dispersion amount being opposite in sign to the first accumulated chromatic dispersion amount, based on the optical signal in the second optical transmission line between the optical repeater and a network device on a receiving side of the optical signal transmitted by the optical repeater; a control unit for calculating the chromatic dispersion compensation amount, the chromatic dispersion compensation amount indicating a difference between the chromatic dispersion amount of the optical signal at the time of transmission in the optical repeater when the accumulated chromatic dispersion amount of the optical signal becomes the second accumulated chromatic dispersion amount at the second effective nonlinear distance based on a statistical value of a transition of the accumulated chromatic dispersion amount of the optical signal according to the distance in the second optical transmission path, and the chromatic dispersion amount which is a result of the complex conjugation; a chromatic dispersion compensation unit that determines an amount of chromatic dispersion of an optical signal to be transmitted to the receiving network device based on the amount of chromatic dispersion obtained from the control device and the amount of chromatic dispersion that is a result of the complex conjugation after the phase conjugation process is performed; 25. The optical repeater device according to claim 24, comprising:

[0162] (Appendix 26) digital signal processing means for performing frequency flip processing on at least one or more channels of an optical signal on a channel-by-channel basis; An optical repeater device comprising:

[0163] (Appendix 27) The digital signal processing means performs the frequency flip processing on all channels of the optical signal on a channel-by-channel basis. 27. The optical repeater device according to claim 26.

[0164] (Appendix 28) The digital signal processing means sequentially identifies a processing target and a non-processing target among the plurality of channels having different frequency bands, which are arranged in order based on the frequency band, and performs the frequency flip processing on the processing target channel. 28. The optical repeater device according to claim 26 or 27.

[0165] (Appendix 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 of the frequency band. 29. An optical repeater device according to any one of claims 26 to 28.

[0166] (Appendix 30) The digital signal processing means comprises: a phase conjugate processing means for performing a phase conjugate process on an electrical signal based on the received optical signal; a chromatic dispersion compensation unit that performs chromatic dispersion compensation processing on an electrical signal based on the received optical signal; A frequency flip processing means for performing the frequency flip processing; 30. The optical repeater device according to claim 26, further comprising:

[0167] (Appendix 31) The frequency flip processing means performs the phase conjugation processing and the chromatic dispersion compensation processing for all channels of the optical signal, and performs the frequency flip processing on at least one or more channels on a channel-by-channel basis. 31. The optical repeater device according to any one of claims 26 to 30.

[0168] (Appendix 32) a chromatic dispersion compensation processing unit that performs chromatic dispersion compensation processing on an electrical signal based on a received optical signal, based on a carrier frequency and a frequency band of a corresponding channel among a plurality of channels included in the optical signal; a phase conjugate processing means for performing a phase conjugate process on an electrical signal based on the received optical signal; An optical repeater device comprising:

[0169] (Appendix 33) The chromatic dispersion compensation processing means includes: performing chromatic dispersion compensation processing based on a frequency region of the relevant channel among the frequency bands of all the channels of the plurality of channels having different frequency bands; 33. The optical repeater device of claim 32.

[0170] (Appendix 34) The chromatic dispersion compensation processing means includes: Before or after the phase conjugation process, a chromatic dispersion compensation process is performed 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. 34. The optical repeater device according to claim 32 or 33.

[0171] (Appendix 35) a carrier frequency control means for performing carrier frequency control to change the frequencies of a plurality of channels included in the optical signal; 35. The optical repeater device according to claim 32, further comprising:

[0172] (Appendix 36) The carrier frequency control means identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, and determining carrier frequencies at the time of transmission of the plurality of channels such that the order of the channels is reversed; 36. The optical repeater device of claim 35.

[0173] (Appendix 37) The carrier frequency control means identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, determining carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels, and further providing a certain frequency offset to each of the channels; 37. The optical repeater device according to claim 35 or 36.

[0174] (Appendix 38) performing chromatic dispersion compensation processing on an electrical signal based on a received optical signal, based on a carrier frequency and a frequency band of a corresponding channel among a plurality of channels included in the optical signal; A phase conjugate process is performed on the electrical signal based on the received optical signal. Optical relay method.

[0175] (Appendix 39) Carrier frequency control is performed to change the frequencies of the multiple channels included in the optical signal. 39. The optical relay method according to claim 38.

[0176] (Appendix 40) performing the chromatic dispersion compensation process based on a frequency region of the relevant channel among the frequency bands of all the channels of the plurality of channels having different frequency bands; 39. An optical relay method according to claim 38 or 39.

[0177] (Appendix 41) Before or after the phase conjugation process, the chromatic dispersion compensation process is performed 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. 41. An optical relay method according to any one of claims 38 to 40.

[0178] (Appendix 42) identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, and determining carrier frequencies at the time of transmission of the plurality of channels such that the order of the channels is reversed; 42. An optical relay method according to any one of claims 38 to 41.

[0179] (Appendix 43) identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, determining carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels, and further providing a certain frequency offset to each of the channels; 43. An optical relay method according to any one of claims 38 to 42.

[0180] (Appendix 44) An optical repeater device, a chromatic dispersion compensation processing means for performing chromatic dispersion compensation processing on an electrical signal based on a received optical signal, based on a carrier frequency and a frequency band of a corresponding channel among a plurality of channels included in the optical signal; a phase conjugate processing means for performing a phase conjugate process on an electrical signal based on the received optical signal; A program to function as a

[0181] (Appendix 45) A carrier frequency control means for performing carrier frequency control for changing the frequencies of a plurality of channels included in the optical signal; 45. The program according to claim 44 for causing the device to function as a

[0182] (Appendix 46) The chromatic dispersion compensation processing means includes: performing chromatic dispersion compensation processing based on a frequency region of the relevant channel among the frequency bands of all the channels of the plurality of channels having different frequency bands; 46. ​​The program according to claim 44 or 45.

[0183] (Appendix 47) The chromatic dispersion compensation processing means includes: Before or after the phase conjugation process, a chromatic dispersion compensation process is performed 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. 47. A program according to any one of claims 44 to 46.

[0184] (Appendix 48) The carrier frequency control means identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, and determining carrier frequencies at the time of transmission of the plurality of channels such that the order of the channels is reversed; 46. ​​The program according to claim 45.

[0185] (Appendix 49) The carrier frequency control means identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, determining carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels, and further providing a certain frequency offset to each of the channels; 47. The program according to claim 45 or 48. [Explanation of symbols]

[0186] 1. Optical network system 2. Optical repeater 3. Optical transmission path 5. Data Center 6. IT service providers 7, 8: Event venue 10. Control device 11...Management Department 12 Phase conjugate control section 13 Wavelength dispersion compensation control section 14 Carrier frequency control section 20 Optical repeater 21 Coherent receiver front-end 22 Phase conjugation section 23...chromatic dispersion compensation section 24 Coherent transmission front-end 25 Phase conjugate acquisition section 26...Chromatic dispersion compensation acquisition section 27 Carrier frequency acquisition section 30. Transmitting end station device 40 Receiving terminal device 50 Optical Network System 51 Optical Network 60. Computer 61. Processor 62...Memory 90 Optical repeater 100... Control device 110 Network Management Department 120 Network control section 130...Chromatic dispersion compensation amount calculation section 140... Phase conjugate determination unit 150 Carrier frequency control section 200 Optical repeater 201 Optical transmitter / receiver 202 Node control unit 210 Coherent receiver front end 220 Coherent transmission front end 230 Digital signal processing unit 231...chromatic dispersion compensation section 232 Phase conjugate processing unit 240···Receiving light source 250···Transmitting light source 260··ADC 270···DAC 300 Optical switch section 301...Brancher 302...Multiplexer 303... Branch insertion part 310 Transmitter / receiver 311, 312, 313... Optical transceiver 401... Delay unit 402... Multiplier 403 Adder 411...Overlap addition part 412 Fast Fourier transform section 413 Frequency response multiplier 414...Inverse Fast Fourier Transform 415···Overlap removal section 910...Acquisition section 901···Digital signal processing unit

Claims

1. a chromatic dispersion compensation processing unit that performs chromatic dispersion compensation processing on an electrical signal based on a received optical signal, based on a carrier frequency and a frequency band of a corresponding channel among a plurality of channels included in the optical signal; a phase conjugate processing means for performing a phase conjugate process on an electrical signal based on the received optical signal; An optical repeater device comprising:

2. The chromatic dispersion compensation processing means includes: performing chromatic dispersion compensation processing based on a frequency region of the relevant channel among the frequency bands of all the channels of the plurality of channels having different frequency bands; 2. The optical repeater according to claim 1.

3. The chromatic dispersion compensation processing means includes: Before or after the phase conjugation process, a chromatic dispersion compensation process is performed 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.

3. The optical repeater according to claim 2.

4. a 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 repeater according to claim 3 .

5. The carrier frequency control means identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, and determining carrier frequencies at the time of transmission of the plurality of channels such that the order of the channels is reversed; 5. The optical repeater according to claim 4.

6. The carrier frequency control means identifying an order of the plurality of channels arranged in order based on the frequency band among the plurality of channels having different frequency bands, determining carrier frequencies at the time of transmission of the plurality of channels so as to reverse the order of the channels, and further providing a certain frequency offset to each of the channels; 6. The optical repeater according to claim 5.

7. performing chromatic dispersion compensation processing on an electrical signal based on a received optical signal, based on a carrier frequency and a frequency band of a corresponding channel among a plurality of channels included in the optical signal; A phase conjugate process is performed on the electrical signal based on the received optical signal. Optical relay method.

8. Carrier frequency control is performed to change the frequencies of the multiple channels included in the optical signal.

8. The optical relay method according to claim 7.

9. An optical repeater device, a chromatic dispersion compensation processing means for performing chromatic dispersion compensation processing on an electrical signal based on a received optical signal, based on a carrier frequency and a frequency band of a corresponding channel among a plurality of channels included in the optical signal; a phase conjugate processing means for performing a phase conjugate process on an electrical signal based on the received optical signal; A program to function as a

10. A carrier frequency control means for performing carrier frequency control for changing the frequencies of a plurality of channels included in the optical signal; The program according to claim 9, for causing the program to function as a

Images