Optical relay device, optical relay method, program

Abstract

The present invention performs frequency flipping processing for at least one optical signal channel in units of channel.

Description

Technical Field

[0001] The present invention relates to an optical relay device, an optical relay method, and a program.

Background Art

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

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

[0004] As related technologies, for example, Patent Documents 1 to 4 are known. Patent Document 1 discloses a wavelength converter that converts the wavelength of an optical signal by a receiving end and a transmitting end using a coherent method.

[0005] Patent Document 2 discloses generating a phase conjugate signal by digital signal processing or connecting an optical phase conjugate device that shifts the optical carrier frequency between a transmitting device and a receiving device.

[0006] Patent Document 3 discloses connecting a dispersion compensation module between a transmitting device and a receiving device to compensate for wavelength dispersion in the optical transmission path.

[0007] Patent Document 4 discloses that nodes in an optical network having multiple spans generate a phase-conjugate signal or an inverted optical spectrum of an optical signal in order to improve the transmission efficiency of optical signals (paragraph 0040, etc.). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 2017-511036 [Patent Document 2] U.S. Patent Application Publication No. 2012 / 0224855 [Patent Document 3] Japanese Patent Publication No. 2011-035735 [Patent Document 4] Japanese Patent Publication No. 2015-220756 [Overview of the project] [Problems that the invention aims to solve]

[0009] In the optical network system-related technologies described above, there is a need to suppress the degradation of signal quality due to nonlinear distortion in optical transmission.

[0010] The purpose of this disclosure is to provide an optical network system, control method, control program, control device, and optical relay device that solve the above-mentioned problems. [Means for solving the problem]

[0011] The optical relay device according to this disclosure comprises a digital signal processing means that performs frequency flip processing on a channel-by-channel basis for at least one channel of an optical signal.

[0012] The optical relay method according to the present disclosure performs frequency flip processing for each channel of at least one or more optical signals on a channel-by-channel basis.

[0013] The program according to the present disclosure causes a computer of an optical relay device to function as digital signal processing means for performing frequency flip processing for each channel of at least one or more optical signals on a channel-by-channel basis.

Effect of the Invention

[0014] According to the present disclosure, it is possible to suppress deterioration of signal quality due to non-linear distortion in optical transmission.

Brief Description of the Drawings

[0015] [Figure 1] It is a configuration diagram showing a configuration example of an optical network system according to a basic example. [Figure 2] It is a configuration diagram showing a configuration example of an optical relay device according to a basic example. [Figure 3] It is a configuration diagram showing a configuration of an optical transceiver according to this disclosure. [Figure 4A] It is a diagram for explaining problems of the optical transceiver according to this disclosure. [Figure 4B] It is a diagram for explaining problems of the optical transceiver according to this disclosure. [Figure 5] It is a configuration diagram showing a schematic configuration of a control device according to an embodiment. [Figure 6] It is a configuration diagram showing a schematic configuration of an optical relay device according to an embodiment. [Figure 7] It is a configuration diagram showing a configuration example of an optical network system according to Embodiment 1. [Figure 8] It is a configuration showing a configuration example of each device in the optical network system according to Embodiment 1. [Figure 9] It is a configuration diagram showing a configuration example of a wavelength dispersion compensation unit according to Embodiment 1. [Figure 10] It is a flowchart showing an operation example of the optical network system according to Embodiment 1. [Figure 11A]It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 1. [Figure 11B] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 1. [Figure 11C] It is a diagram showing an overview of the phase conjugation process according to Embodiment 1. [Figure 11D] It is a first diagram showing an overview of the frequency flip process according to Embodiment 1. [Figure 11E] It is a second diagram showing an overview of the frequency flip process according to Embodiment 1. [Figure 11F] It is a third diagram showing an overview of the frequency flip process according to Embodiment 1. [Figure 12] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 1. [Figure 13A] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 2. [Figure 13B] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 2. [Figure 14A] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 3. [Figure 14B] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 3. [Figure 15] It is a diagram showing the minimum configuration of the control device according to an embodiment of the present disclosure. [Figure 16] It is a diagram showing the processing flow by the control device with the minimum configuration according to an embodiment of the present disclosure. [Figure 17] It is a diagram showing the minimum configuration of the optical relay device according to an embodiment of the present disclosure. [Figure 18] It is a diagram showing the processing flow by the optical relay device with the minimum configuration according to an embodiment of the present disclosure. [Figure 19] It is a diagram showing another configuration of the optical relay device according to an embodiment of the present disclosure. [Figure 20] It is a diagram showing the processing flow by the optical relay device with another configuration according to an embodiment of the present disclosure. [Figure 21]This figure shows another configuration of an optical relay device according to one embodiment of the present disclosure. [Figure 22] This figure shows the processing flow by an optical relay device in another configuration of one embodiment of the present disclosure. [Figure 23] This is a configuration diagram showing an overview of the computer hardware of one embodiment of the present disclosure. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments of the optical network system, control method, control program, control device, and optical relay device of this disclosure will be described with reference to the drawings. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations are omitted where necessary. The arrows in the configuration diagrams (block diagrams) are illustrative for explanatory purposes only and do not limit the type or direction of the signals.

[0017] (Considerations leading to the embodiment) Figure 1 shows the configuration of an optical network system according to a basic example of this embodiment. The optical network system 1 according to the basic example is, for example, a backbone wavelength division multiplexing optical transmission system, in which the devices constituting the system perform wavelength division multiplexing of optical signals and perform high-level modulation and digital coherent transmission of optical signals of each wavelength to achieve high-capacity communication exceeding 100 Gbps. High-density wavelength division multiplexing makes it possible to improve the frequency utilization efficiency of optical signals and can handle mobile traffic and wavelength defragmentation.

[0018] The optical network system 1 is equipped with optical relay devices 2 (e.g., 2-1 to 2-10) that can flexibly switch transmission paths (wavelength paths and optical transmission paths) while maintaining the optical signal, in order to switch transmission paths in the event of a failure and to respond to local traffic demands (e.g., traffic demands from data centers 4 and 5, the networks of IT service providers 6, and the networks of event venues 7 and 8). The optical network system 1 can maintain communication using optical signals as infrastructure by being equipped with optical relay devices 2 (e.g., 2-1 to 2-10). The optical relay devices 2 are photonic nodes capable of relaying wavelength-multiplexed optical signals, and are, for example, ROADM (Reconfigurable Optical Add / Drop Multiplexer) devices. Each optical relay device 2 is assigned a wavelength path (also simply called a path), and it forwards traffic from the local network it houses and other optical relay devices 2 to the destination network or other communication devices via optical communication cables that carry the optical signals of the assigned wavelength path.

[0019] Figure 2 shows an example configuration of the optical repeater 2 according to a basic example. The optical repeater 2 branches / inserts optical wavelength multiplexed signals and coherently modulates / demodulates the signals of each wavelength to be branched / inserted. As shown in Figure 2, the optical repeater 2 includes an optical switch unit 300 and a transmitting / receiving unit 310.

[0020] The optical switch unit 300 transfers optical signals of a predetermined wavelength path received from the preceding optical relay device 2 in the optical network system 1 to the subsequent optical relay device 2, and also branches / inserts the received optical signals for each wavelength. For example, the optical switch unit 300 includes a demultiplexer 301, a multiplexer 302, and a branching / inserting unit 303. The demultiplexer 301 separates the optical signal received from the optical transmission path 3 into optical signals of multiple wavelengths. The multiplexer 302 combines the multiple wavelength optical signals into a single optical signal and transmits it to the optical transmission path 3. The branching / inserting unit 303 branches / inserts the optical signals of each wavelength between the demultiplexer 301 and the multiplexer 302.

[0021] The transponder 310 receives optical signals of each wavelength branched from the branch insertion section 303 of the optical switch section 300 and outputs them to a local device (network) that stores the coherently demodulated received data. The transponder 310 also receives transmission data from the local device and transmits (inserts) the coherently modulated optical signals of each wavelength to the branch insertion section 303 of the optical switch section 300. The transponder 310 is equipped with multiple optical transceivers 311 that transmit and receive optical signals of each wavelength. The optical transceivers 311 receive an optical signal of a predetermined wavelength and then transmit an optical signal of a predetermined wavelength (the same or different wavelength as the received wavelength) to the destination.

[0022] Here, we will consider the challenges that arise when using an optical transceiver 311. Figure 3 shows an example configuration of the optical transceiver according to this disclosure. As shown in Figure 3, the optical transceiver 314 according to this disclosure includes a coherent receiving front end 210, a coherent transmitting front end 220, an acquisition unit 910, and a digital signal processing unit 901. Digital signal processing enables channel-level phase conjugation and wavelength dispersion compensation.

[0023] The coherent receiving front-end unit 210 coherently detects the optical signal received from the preceding optical relay device 2 using local oscillator (LO) light of a predetermined wavelength and outputs the detected signal to the digital signal processing unit 901. The coherent transmitting 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 next optical relay device 2. The digital signal processing unit 901 is a DSP (Digital Signal Processor) that converts the signal coherently detected by the coherent receiving front-end unit 210 into a digital signal, outputs the signal-processed received data, and also reconstructs the input transmission data and outputs the signal converted for optical modulation to the coherent transmitting front-end unit 220. In this disclosure, the digital signal processing unit 901 performs channel-level phase conjugate processing and wavelength dispersion compensation.

[0024] Figures 4A and 4B show the chromatic dispersion when using an optical relay device 90 including an optical transceiver 314 according to this disclosure. As shown in Figure 4A, the optical relay device 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. Optical transmission path 3a has a distance L1, and optical transmission path 3b has a distance L2, and L1 and L2 may be the same length or different. An optical signal with wavelength λ1 is transmitted through optical transmission path 3a, and an optical signal with wavelength λ2 is transmitted through optical transmission path 3b.

[0025] In addition, in a configuration where the optical relay device 90 is connected to the path from the transmitting terminal device 30 to the receiving terminal device 40, as shown in Figure 4A, the part of the optical relay device 90 closer to the transmitting terminal device 30 may be referred to as the upstream stage (receiving side of the optical signal) of the optical relay device 90, and the part of the optical relay device 90 closer to the receiving terminal device 40 may be referred to as the downstream stage (transmitting side of the optical signal) of the optical relay device. Furthermore, the optical transmission path between the optical relay device 90 and the transmitting terminal device 30 may be referred to as the upstream (first part) optical transmission path, and the optical transmission path between the optical relay device 90 and the receiving terminal device 40 may be referred to as the downstream (second part) optical transmission path.

[0026] As shown in Figure 4B, chromatic dispersion increases in proportion to the distance of the optical transmission path. Therefore, if an optical relay device relays an optical signal by simply amplifying the signal, the chromatic dispersion continues to increase with distance from the transmitting terminal device 30 to the receiving terminal device 40. Consequently, 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, nonlinear distortion also significantly deteriorates the quality of the optical signal. Nonlinear distortion is a phenomenon in which the refractive index in the material changes in proportion to the optical signal intensity as the optical signal propagates through the optical fiber, causing a change in the phase of the light itself. Such nonlinear distortion is a factor that limits the ability to increase the capacity and long-distance transmission of optical signals through high baud rates and high multi-level systems.

[0027] In the above-described example, phase conjugation and wavelength dispersion compensation are performed in the optical relay device 90 connected to the path from the transmitting terminal device 30 to the receiving terminal device 40. In the above-described example, by performing phase conjugation and wavelength dispersion compensation in the optical relay device 90, the nonlinear distortion generated in the preceding transmission path and the nonlinear distortion generated in the subsequent transmission path in the phase-conjugated light transmitted from the optical relay device 90 cancel each other out, thereby mitigating the effect of nonlinear distortion at the receiving terminal device 40, which is the receiving end.

[0028] In the example disclosed above, the effects of intra-channel nonlinear distortion in single-channel transmission in an optical transmission path are mitigated.

[0029] In addition to the examples of disclosure described above, it is desirable to ensure that sufficient mitigation of nonlinear distortion can be obtained when there are multiple optical channels in the optical transmission signal transmitted through the optical fiber. This disclosure makes it possible to reduce inter-channel nonlinear effects during multi-channel transmission in optical relay devices in a multi-optical transmission network. Furthermore, this disclosure also makes it possible to reduce intra-channel nonlinear distortion by performing optimal wavelength dispersion compensation and phase conjugation in optical relay devices in a multi-optical transmission network.

[0030] This embodiment outlines the following. In addition to a relay configuration using optical phase conjugation and wavelength dispersion compensation for intra-channel nonlinear reduction, the inter-channel nonlinear reduction configuration shown in this disclosure is also presented. As a compensation method for intra-channel nonlinear distortion, compensation may be performed by digital backpropagation in the digital signal processing unit at the optical transmitting or receiving end. Furthermore, although the effect will be smaller, it is also possible to omit intra-channel nonlinear distortion compensation processing and use only a configuration for reducing inter-channel nonlinear distortion.

[0031] (Summary of the embodiment) Figure 5 shows the schematic configuration of the control device according to this embodiment. Figure 6 shows the schematic configuration of the optical relay device according to this embodiment. The control device 10 and the optical relay device 20 constitute an optical network system. The optical relay device 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 relay device 20, which is a component of the optical network system.

[0032] As shown in Figure 5, the control device 10 comprises a management unit 11, a phase conjugate control unit 12, a wavelength dispersion compensation control unit 13, and a frequency flip control unit 14. The management unit 11 manages the wavelength information of the optical signals transmitted and received by the optical relay device 20 in the optical network path and the transmission path information of the optical transmission path connected to the optical relay device 20. The phase conjugate control unit 12 determines the phase conjugate processing in the optical relay device 20 based on the wavelength information and transmission path information managed by the management unit 11. The wavelength dispersion compensation control unit 13 determines the amount of wavelength dispersion compensation to be compensated in the optical relay device 20 based on the wavelength information and transmission path information managed by the management unit 11. The frequency flip control unit 14 instructs that frequency flip processing be performed on a channel-by-channel basis for at least one or more channels of optical signals.

[0033] As shown in Figure 6, the optical relay device 20 includes a coherent receiving front end unit 21, a phase conjugate unit 22, a wavelength dispersion compensation unit 23, a coherent transmitting front end unit 24, a phase conjugate acquisition unit 25, a wavelength dispersion compensation acquisition unit 26, a frequency flip instruction acquisition unit 27, and a frequency flip processing unit 28. Although not shown in Figure 6, it transmits and receives signals from multiple optical channels and processes the signals from each channel with phase conjugate, wavelength dispersion compensation, and frequency flip.

[0034] 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 wavelength dispersion compensation acquisition unit 26 acquires the wavelength dispersion compensation amount determined by the wavelength dispersion compensation control unit 13 from the control device 10. The frequency flip instruction acquisition unit 27 acquires channel information for the frequency flip processing. The coherent receiving front end unit 21 coherently detects the received optical signal based on local emission and outputs the coherently detected electrical signal. The phase conjugate unit 22 performs phase conjugate processing on the electrical signal output from the coherent receiving front end unit 21 by digital signal processing based on the phase conjugate processing setting acquired by the phase conjugate acquisition unit 25. The wavelength dispersion compensation unit 23 performs wavelength dispersion compensation processing on the electrical signal output from the phase conjugate unit 22 by digital signal processing based on the wavelength dispersion compensation amount acquired by the wavelength dispersion compensation acquisition unit 26. The frequency flip processing unit 28 uses the electrical signal output from the wavelength dispersion compensation unit 23 to perform channel-level frequency flip processing on at least one optical signal based on the frequency flip processing information acquired from the frequency flip instruction acquisition unit 27. Frequency flip processing is a process that inverts the frequency components of the optical signal for each frequency based on a reference frequency set at the center of the frequency band of the channel. The coherent transmission front-end unit 24 coherently modulates the electrical signal that has undergone phase conjugation processing by the phase conjugation unit 22 and the electrical signal that has undergone wavelength dispersion compensation processing by the wavelength dispersion compensation unit 22 based on the transmitted light, and transmits the coherently modulated optical signal.

[0035] In this embodiment, the control device 10 determines the phase conjugation processing and wavelength dispersion compensation amount in the optical repeater 20 based on the wavelength information of the optical signals transmitted and received by the optical repeater 20 in the path and the transmission path information of the optical transmission path connected to the optical repeater 20. The control device 10 performs wavelength dispersion compensation of the determined phase conjugation processing and wavelength dispersion compensation amount in the optical repeater 20 in order to reduce intrachannel nonlinear distortion. The control device 10 also performs channel-level frequency flip processing to suppress nonlinear effects between channels.

[0036] By performing phase conjugation of the optical signal in the optical relay device 20, the distortion of the optical signal in the optical transmission path preceding the optical relay device 20 can be reversed. As the signal propagates through the optical transmission path following the optical relay device 20, the distortion is reversed and canceled out at the receiving end. In the embodiment shown below, the optical relay device 20 can perform chromatic dispersion compensation with appropriate phase conjugation and chromatic dispersion compensation amounts. Therefore, by using this for phase conjugation and chromatic dispersion compensation in each optical relay device 20 in a multi-span optical network, it is possible to maximize the cancellation effect of nonlinear distortion due to multi-span optical transmission, and effectively suppress the degradation of signal quality due to intra-channel nonlinear distortion at the receiving end of the optical network. In addition, since the optical relay device 20 performs channel-level frequency flip processing, nonlinear effects between channels can be suppressed.

[0037] (Embodiment 1) Next, Embodiment 1 will be described with reference to the drawings. Figure 7 shows an example of the configuration of an optical network system according to this embodiment. As shown in Figure 7, the optical network system 50 according to this embodiment includes a control device 100, a plurality of optical relay devices 200, a transmitting terminal device 30, and a receiving terminal device 40.

[0038] Multiple optical repeaters 200, transmitting terminal station 30, and receiving terminal station 40 are connected via an optical transmission path 3 to enable optical communication. Multiple optical repeaters 200, transmitting terminal station 30, and receiving terminal station 40 are connected to the control device 100 to enable communication of control signals. Multiple optical repeaters 200, transmitting terminal station 30, and receiving terminal station 40 are connected to the control device 100 via an optical transmission path 3, or they may be connected to the control device 100 to enable communication by any other transmission path, including wired or wireless.

[0039] Multiple optical relay devices 200, a transmitting terminal device 30, and a receiving terminal device 40 constitute an optical transmission device (optical node) that performs optical communication via an optical transmission path 3. The transmitting terminal device 30 and the receiving terminal device 40 constitute the transmitting and receiving ends of a path formed by the connection of multiple optical transmission paths 3. The transmitting terminal device 30 transmits a multi-channel optical signal, wavelength-multiplexed by the wavelength 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 a multi-channel optical signal, wavelength-multiplexed by the wavelength of the path set by the control device 100, from the transmitting terminal device 30 via the optical transmission path 3.

[0040] The multiple optical relay devices 200 are relay devices capable of relaying wavelength-multiplexed multi-channel optical signals, similar to the basic example. The multiple optical relay devices 200 constitute an optical network 51 that performs WDM communication. It can also be said that the multiple optical relay devices 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, similar to Figure 1. The optical network 51 may be a mesh network, a ring network, a point-to-point network, or a network with other topologies. Furthermore, the multiple optical relay devices 200, in response to control from the control device 100, constitute a path from the transmitting terminal device 30 to the receiving terminal device 40 and transmit optical signals (data) at wavelengths set along the path.

[0041] The control device 100 manages and controls the optical network 51, which includes multiple optical relay devices 200. For example, the control device 100 is a Network Management System (NMS) that manages the network.

[0042] The control device 100 manages and controls the paths formed by the optical relay devices 200 in the optical network 51. The control device 100 manages the path and wavelength of the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the path, wavelength, etc. for the transmitting terminal device 30, the receiving terminal device 40, and the optical relay devices 200 along the path.

[0043] Figure 8 shows an example of the configuration of each device in the optical network system according to this embodiment. As shown in Figure 8, the control device 100 includes a network management unit 110, a network control unit 120, a wavelength dispersion compensation amount calculation unit 130, a phase conjugate determination unit 140, and a frequency flip instruction unit 150.

[0044] The network management unit 110 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 composed of a database that stores information necessary for network management. Network configuration information includes the connection relationships of the optical relay devices 200, transmitting terminal devices 30, and receiving terminal devices 40 that constitute the network, and transmission path information of the optical transmission paths 3 that connect each device. Transmission path information includes the distance L (transmission path length) of the optical transmission path and may also include the structure and type of optical fiber, transmission characteristics, etc. Path configuration information includes information on each device that constitutes the path, the wavelengths that each device can use on the path route, and the status of wavelength usage, etc. This information may be set in advance in the database, or it may be set using information collected from each device, or it may be updated by the network control unit 120, etc.

[0045] The network control unit 120 controls the paths in the optical network 51 and the optical relay devices 200, transmitting terminal device 30, and receiving terminal device 40 that constitute the paths. The network control unit 120 refers to network configuration information and path configuration information in the network management unit 110 to determine the path and wavelength from the transmitting terminal device 30 to the receiving terminal device 40, and sets the determined path and wavelength to the transmitting terminal device 30, the receiving terminal device 40, and the optical relay devices 200 along the path. The wavelength of light in a path is determined for each optical transmission path along the path. For example, if the path of one path overlaps with the path of another path, different wavelengths are selected from the available wavelengths in the optical transmission path of the overlapping section. The network control unit 120 also outputs information necessary for calculating the wavelength dispersion compensation amount in the optical relay devices 200 that constitute the path to the wavelength dispersion compensation amount calculation unit 130. For example, the network control unit 120 outputs the received wavelength information (wavelength information of the received optical signal), the transmitted wavelength information (wavelength information of the transmitted optical signal), and the transmission path information of the preceding and succeeding optical transmission paths of the optical relay device 200. The network control unit 120 also outputs the phase conjugate determination information of the optical relay device 200 that constitutes the path to the phase conjugate determination unit 140. For example, the network control unit 120 outputs the number of paths and the number of optical relay devices in the optical network 51.

[0046] The wavelength dispersion compensation amount calculation unit 130 calculates the wavelength dispersion compensation amount for the optical repeater devices 200 that constitute the path to perform wavelength dispersion compensation. The wavelength dispersion compensation amount calculation unit 130 is a compensation control unit that determines and controls the wavelength dispersion compensation amount of the optical repeater devices 200. Based on the received wavelength information, transmitted wavelength information, and transmission path information before and after the optical repeater devices of the optical repeater devices 200 obtained from the network control unit 120, the wavelength dispersion compensation amount calculation unit 130 determines the optimal wavelength dispersion compensation amount for the optical repeater devices 200. The wavelength dispersion compensation amount calculation unit 130 notifies the corresponding optical repeater devices 200 of the received wavelength information, transmitted wavelength information, and the optimal wavelength dispersion compensation amount.

[0047] The phase conjugation determination unit 140 controls the phase conjugation processing of the optical relay devices 200 that constitute the path. Based on the number of paths and the number of optical relay devices in the optical network 51 obtained from the network control unit 120, the phase conjugation determination unit 140 determines the optimal phase conjugation processing for the optical relay devices 200. The phase conjugation determination unit 140 notifies the optical relay devices 200 of the phase conjugation processing information.

[0048] The frequency flip instruction unit 150 instructs the frequency of the channel to be subjected to frequency flip processing. The frequency flip instruction unit 150 instructs that frequency flip processing be performed on a channel-by-channel basis for at least one channel. The frequency flip instruction unit 150 may also instruct that frequency flip processing be performed on a channel-by-channel basis for all channels of the optical signal. The frequency flip instruction unit 150 may sequentially identify channels to be processed and channels not to be processed from among a plurality of channels with different frequency bands that are arranged sequentially based on the frequency band, and instruct that frequency flip processing be performed on the channels to be processed.

[0049] In the optical network 51, multi-channel optical signals are relayed via the optical transmission path 3 by multiple optical relay devices 200. When multiple optical relay devices 200 in the optical network 51 perform frequency flip processing on a given channel of an optical signal, the control device 100 counts the number of frequency flips for that channel and notifies the receiving end optical device 40. Based on the notified number of frequency flips for that channel, the signal processing unit for that channel in the receiving end optical device decides whether to perform frequency flip processing and performs signal processing on the received signal.

[0050] Furthermore, as shown in Figure 8, the optical relay device 200 according to this embodiment includes an optical transceiver 201 and a node control unit 202. Although not shown in Figure 8, in order to transmit and receive multiple optical channels, the optical relay device 200 includes an optical switch unit 300 and a transmitting / receiving unit 310, similar to the basic example in Figure 2, and the transmitting / receiving unit 310 includes multiple optical transceivers 201. In other words, the node control unit 202 can control the optical switch unit 300 and the transmitting / receiving unit 310 (multiple optical transceivers 201).

[0051] The optical transceiver 201 includes a coherent receiving front end 210, a coherent transmitting front end 220, a digital signal processing unit 230, a receiving light source 240, a transmitting light source 250, an ADC 260, and a DAC 270.

[0052] The receiving light source 240 generates local light emission r1 at a wavelength (frequency) set by the node control unit 202 and outputs the generated local light emission r1 to the coherent receiving front end unit 210. The transmitting light source 250 generates transmitting light r2 at a wavelength (frequency) set by the node control unit 202 and outputs the generated transmitting light r2 to the coherent transmitting front end unit 220.

[0053] The frequency (wavelength) of the station light emission 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. For example, the station light emission r1 and the transmitted light r2 may have different frequencies or the same frequency. By changing the frequencies of the station light emission r1 and the transmitted light r2, the wavelength of the relayed optical signal can be switched. This allows the input optical signal SO1 to be converted into an output optical signal SO2 with a different wavelength.

[0054] The coherent receiving front end 210 and the coherent transmitting front end 220 have the same configuration as in Figure 3. The coherent receiving front end 210 is an optical / electrical conversion unit that converts optical signals into electrical signals and is a coherent detection unit that performs coherent detection. The coherent receiving front end 210 coherently detects the input optical signal SO1 (received optical signal) based on the local light emission r1 and outputs the generated analog signal SA1 (first analog electrical signal).

[0055] The ADC (Analog / Digital Converter) 260 performs A / D conversion on the analog signal SA1 generated by the coherent receiving front-end unit 210 and outputs the converted digital signal SD1 (first digital electrical signal).

[0056] The DAC (Digital / Analog Converter) 270 performs a digital-to-analog conversion on the digital signal SD2 (second digital electrical signal) processed by the digital signal processing unit 230, and outputs the converted analog signal SA2 (second analog electrical signal).

[0057] The coherent transmission front-end unit 220 is an electro-optical conversion unit that converts electrical signals into optical signals, and is a coherent modulation unit that performs coherent modulation. The coherent transmission front-end unit 220 coherently modulates the analog signal SA2 converted by the DAC270 based on the transmitted optical r2, and outputs the generated output optical signal SO2 (transmitted optical signal).

[0058] For example, the input optical signal SO1 and the output optical signal SO2 are phase-modulated and polarization-multiplexed optical signals. The analog signals SA1 and SA2, and the digital signals SD1 and SD2 are 4-lane (4ch) signals including the IX signal, which is the I component (in-phase component) of the X polarization; the QX signal, which is the Q component (orthogonal component) of the X polarization; the IY signal, which is the I component of the Y polarization; and the QY signal, which is the Q component of the Y polarization.

[0059] The digital signal processing unit 230 performs digital signal processing on the digital signal SD1 converted by the ADC260 and outputs the digital signal SD2 after digital signal processing. The digital signal processing unit 230 is a digital circuit that performs predetermined digital signal processing to compensate for signal quality. The digital signal processing unit 230 performs digital signal processing on all or part (X-polarization or Y-polarization) of each of the four lanes of the IX signal, QX signal, IY signal, and QY signal.

[0060] The digital signal processing unit 230 performs only specific signal processing, without performing processes that involve large delays, such as code error correction (data reconstruction). This allows for the compensation of necessary signal quality while suppressing signal delay. In this embodiment, the digital signal processing unit 230 includes a wavelength dispersion compensation unit 231 that performs wavelength dispersion processing, a phase conjugation processing unit 232 that performs phase conjugation processing, and a frequency flip processing unit 233 that performs frequency flip processing.

[0061] Wavelength dispersion compensation using digital signal processing can be achieved by convolution of the impulse response of the inverse transfer function of the optical transmission path with the received signal. For this reason, the wavelength dispersion compensation section 231 may be configured using a transversal filter (FIR filter). Since the characteristics of the optical transmission path can be modeled with an FIR filter, wavelength dispersion can be compensated using an FIR filter with inverse characteristics. While an FIR filter performs time-domain equalization (TDE) with respect to the received signal in the time-delay domain, the same characteristics may be achieved by frequency-domain equalization (FDE). By configuring the wavelength dispersion compensation section using FDE, the circuit size can be reduced compared to using an FIR filter.

[0062] Figure 9 shows an example configuration when the wavelength dispersion compensation unit 231 is configured by FDE processing. The wavelength dispersion compensation unit 231 in Figure 9 is an example configuration of overlap FDE and includes an overlap addition unit 411, a fast Fourier transform unit 412, an inverse transfer function multiplication unit 413, an inverse fast Fourier transform unit 414, and an overlap removal unit 415.

[0063] The node control unit 202 sets the wavelength dispersion compensation amount notified by the control device 100 to the wavelength dispersion compensation unit 231 in the digital signal processing unit 230. If the wavelength dispersion compensation unit 231 is configured as an FDE as shown in Figure 9, the node control unit 202 sets the transfer function coefficients of the inverse transfer function multiplication unit 413 in Figure 9 according to the wavelength dispersion compensation amount notified by the control device 100.

[0064] The overlap addition unit 411 overlaps a portion of the preceding and succeeding signals with the input signal (digital signal). Then, the fast Fourier transform unit 412 converts the overlapped signal into a frequency domain signal using a fast Fourier transform (FFT). The inverse transfer function multiplication unit 413 equalizes the frequency domain signal by multiplying it by the inverse transfer function of the transmission line. Then, the inverse fast Fourier transform unit 414 converts it into a time domain signal using an inverse fast Fourier transform (IFFT). The overlap removal unit 415 removes the overlap portion from the time domain signal and outputs it. When using FDE, the amount of wavelength 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.

[0065] Frequency flip processing in digital signal processing inverts the frequency response components of an input signal. The input signal is converted into a frequency domain signal using FFT. The frequency components are inverted with respect to the center frequency of the channel. Then, it is converted into a time domain signal using IFFT. Frequency flip processing may be performed in conjunction with chromatic dispersion compensation in the same FDE processing unit, or it may be performed in an FDE processing unit independent of chromatic dispersion compensation.

[0066] Phase conjugation processing using digital signal processing determines the complex conjugate of the input digital signal. That is, as shown in equation (1) below, the sign of the imaginary component Q in the Ix, Qx, Iy, and Qy signals is reversed.

[0067]

number

[0068] The node control unit 202 receives control information from the control device 100 and controls each part of the optical relay device 200 based on the received control information. The node control unit 202 is an acquisition unit that acquires received wavelength information and transmitted wavelength information from the network control unit 120, the optimal wavelength dispersion compensation amount from the wavelength dispersion compensation amount calculation unit 130, phase conjugate processing information from the phase conjugate determination unit 140, and channel information for frequency flipping from the frequency flip instruction unit 150. Based on the acquired received wavelength information, the node control unit 202 sets the frequency (wavelength) of the local emission r1 for the receiving light source 240 and sets the frequency of the transmitted light r2 for the transmitting light source 250 based on the acquired transmitted wavelength information. Based on the control information including an instruction to perform phase conjugate processing acquired from the control device 100, the node control unit 202 sets the phase conjugate processing calculation for the phase conjugate processing unit 232. Based on the acquired optimal wavelength dispersion compensation amount, the node control unit 202 sets the wavelength dispersion compensation amount for the wavelength dispersion compensation unit 231. The node control unit 202 sets the channel information acquired from the control device 100 into the frequency flip processing unit 233.

[0069] Figure 10 shows an example of operation of the optical network system according to this embodiment. As shown in Figure 10, first, the network management unit 110 of the control device 100 determines the wavelength to be used by the optical relay device 200 (S101). The network control unit 120 of the control device 100 determines the path of the optical network 51 and identifies the optical transmission path and optical relay device 200 along the path. By determining the wavelength of each identified optical transmission path, the network control unit 120 determines the wavelengths of the preceding and succeeding stages (before and after conversion) in each optical relay device 200, that is, the wavelength of the optical signal transmitted and received by the optical relay device 200. The network control unit 120 outputs the received wavelength information and transmitted wavelength information of the optical relay device 200 to the wavelength dispersion compensation amount calculation unit 130, the phase conjugate determination unit 140, and the frequency flip instruction unit 150 based on the determined wavelength, and also outputs the transmission path information (distance) of the optical transmission paths before and after the optical relay device 200 to the wavelength dispersion compensation amount calculation unit 130 and the phase conjugate determination unit 140. If the path includes multiple optical relay devices 200, the following processing is performed for each optical relay device.

[0070] Next, the control device 100 and the chromatic dispersion compensation calculation unit 130 of the optical repeater 200 calculate the chromatic dispersion characteristics of the preceding and succeeding optical transmission paths (S102). The chromatic dispersion compensation calculation unit 130 calculates the chromatic dispersion characteristics of the preceding and succeeding optical transmission paths of the optical repeater 200 based on the received wavelength information and transmitted wavelength information obtained from the network control unit 120 and the transmission path information (distance) of the preceding and succeeding optical transmission paths of the optical repeater 200. If 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.

[0071] For example, the chromatic dispersion characteristic is the slope of the chromatic dispersion amount accumulated with respect to the distance of the optical transmission path (the chromatic dispersion characteristic depending on the distance). Since this slope of the chromatic dispersion amount changes with wavelength, a table relating wavelength (or wavelength band) to the slope of the chromatic dispersion amount may be stored in advance. The chromatic dispersion compensation amount calculation unit 130 may refer to this table and determine the chromatic dispersion characteristic corresponding to the wavelength.

[0072] Next, the chromatic dispersion compensation amount calculation unit 130 of the control device 100 determines the optimal chromatic dispersion compensation amount for the optical repeater 200 (S103). The chromatic dispersion compensation amount calculation unit 130 determines the optimal chromatic dispersion compensation amount for the optical repeater 200 based on the chromatic dispersion characteristics of the preceding and succeeding optical transmission paths of the optical repeater 200 and the transmission path information of the preceding and succeeding optical transmission paths. The chromatic dispersion compensation amount calculation unit 130 determines the amount of chromatic dispersion accumulated in the preceding (receiving) optical transmission path and the amount of chromatic dispersion accumulated in the succeeding (transmitting) optical transmission path, and determines the optimal chromatic dispersion amount based on the chromatic dispersion amount of the preceding and succeeding stages. 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 preceding optical transmission path based on the chromatic dispersion characteristics and transmission path information (distance) of the preceding optical transmission path of the optical relay device 200, and determines the amount of chromatic dispersion accumulated in the subsequent optical transmission path based on the chromatic dispersion characteristics and transmission path information of the subsequent optical transmission path of the optical relay device 200. 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 path information, but since the chromatic dispersion characteristics correspond to wavelength information, the amount of chromatic dispersion compensation may also be determined based on the wavelength information and transmission path information. That is, the chromatic dispersion compensation amount calculation unit 130 may determine the amount of chromatic dispersion compensation in multiple optical relay devices 200 constituting the path based on the wavelength information and transmission path information in the path.

[0073] Next, the phase conjugation determination unit 140 of the control device 100 determines the optimal phase conjugation processing in the optical repeater 200 (S104). The phase conjugation determination unit 140 determines the optimal phase conjugation 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 50 and the number of optical repeaters 200. Next, the control device 100 determines the frequency of the channel to which the frequency flip processing will be performed (step S105).

[0074] Next, the control device 100 notifies the optical relay device 200 of the received wavelength information and transmitted wavelength information determined in S101, the optimal phase conjugate processing information determined in S104, the optimal wavelength dispersion compensation amount determined in S103, and the frequency information of the channel to be subjected to frequency flip processing determined in step S105 (S106).

[0075] Next, the node control unit 202 of the optical relay device 200 sets the wavelength of the wavelength information notified from the control device 100, the phase conjugate processing information, the optimal wavelength dispersion compensation amount, and the frequency information of the channel to be processed for frequency flip processing (S107). The node control unit 202 sets the wavelength of the acquired received wavelength information to the receiving light source 240, the wavelength of the acquired transmitted wavelength information to the transmitting light source 250, the acquired phase conjugate processing information to the phase conjugate processing unit 232, the acquired optimal wavelength dispersion compensation amount to the wavelength dispersion compensation unit 231, and the acquired frequency of the channel to be processed for flip processing to the frequency flip processing unit 233 of the corresponding channel.

[0076] Next, the optical repeater 200 performs wavelength conversion, phase conjugation, wavelength dispersion compensation, and frequency flip processing (S108). The receiving light source 240 generates local light emission r1 of a set wavelength (frequency), and the transmitting light source 250 generates transmitted light r2 of a set wavelength, thereby performing wavelength conversion in the optical transceiver 201. The phase conjugation processing unit 232 performs phase conjugation processing by phase conjugation, and the wavelength dispersion compensation unit 231 performs wavelength dispersion compensation processing on the signal after phase conjugation processing based on a set compensation amount by digital signal processing. The frequency flip processing unit 233 performs frequency flip processing to invert the frequency components of the optical signal for each frequency based on a reference frequency set in the center of the indicated frequency band.

[0077] Figures 11A and 11B show specific examples of phase conjugation processing and wavelength dispersion compensation processing according to the control method of this embodiment. In this embodiment, the optical repeater 200 performs phase conjugation processing on the nonlinear distortion accumulated in the preceding optical transmission path in the optical signal received by the optical repeater 200. This makes it possible to cancel out the nonlinear distortion in the transmission of the optical signal transmitted from the optical repeater 200 in the subsequent optical transmission path at the receiving end. To obtain this effect, the optical repeater 200 in this embodiment determines an optimal wavelength dispersion compensation amount that maximizes the nonlinear distortion cancellation effect. In this example, the optimal wavelength dispersion compensation amount is a compensation amount calculated for the optical repeater 200 based on the wavelength dispersion amounts in the preceding and subsequent transmission paths.

[0078] As shown in Figure 11A, in this example, one optical repeater 200 is placed on 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 path 3a (first optical transmission path), and the optical repeater 200 and the receiving terminal device 40 are connected via an optical transmission path 3b (second optical transmission path). For example, the distance L1 of optical transmission path 3a and the distance L2 of optical transmission path 3b are different, with the distance L2 of optical transmission path 3b being longer than the distance L1 of optical transmission path 3a, but they may also be the same distance. An optical signal with wavelength λ1 is transmitted through optical transmission path 3a, and an optical signal with wavelength λ2 is transmitted through optical transmission path 3b. For example, wavelengths λ1 and λ2 may both be in the C-band wavelength range, or they may be different, such as a C-band wavelength range and an L-band wavelength range, or they may both be in the L-band wavelength range. The optical relay device 200 converts the received optical signal of wavelength λ1 into an optical signal of wavelength λ2, and transmits the converted optical signal of wavelength λ2.

[0079] As shown in Figure 11B, in the preceding optical transmission path 3a, the wavelength of the optical signal is λ1, so the wavelength dispersion compensation calculation unit 130 of the control device 100 determines the slope DS1 of the wavelength dispersion in the optical transmission path 3a according to the wavelength λ1. The slope DS1 of the wavelength dispersion in the optical transmission path 3a may be read from a storage means such as a database. The wavelength dispersion compensation calculation unit 130 of the control device 100 uses the slope DS1 of the wavelength dispersion and the effective nonlinear distance Leff1 in the optical transmission path 3a to determine the accumulated wavelength dispersion M1 (=DS1×Leff1) at the effective nonlinear distance Leff1 in the preceding optical transmission path 3a. The nonlinear effect is an effect that depends on the optical signal intensity, and the optical intensity in the transmission path 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 of high optical intensity. The effective nonlinear distance Leff is defined as the distance at which the nonlinear effect is considered, and Leff is given by the following equation (2) using the length L and the propagation loss constant α in the optical fiber.

[0080]

number

[0081] Furthermore, in the subsequent optical transmission path 3b, since the wavelength of the optical signal is λ2, the wavelength dispersion compensation calculation unit 130 of the control device 100 determines the slope DS2 of the wavelength dispersion in the optical transmission path 3b according to the wavelength λ2. The slope DS2 of the wavelength dispersion in the optical transmission path 3b may be read from a storage means such as a database. The wavelength dispersion compensation calculation unit 130 of the control device 100 calculates the cumulative wavelength dispersion M2 at the effective nonlinear distance Leff2 in the subsequent optical transmission path 3b as M2 = -M1, on the condition that it has a different sign from the cumulative wavelength dispersion M1 at the effective nonlinear distance Leff1 in the preceding optical transmission path 3a. Then the wavelength dispersion compensation calculation unit 130 finds the cumulative wavelength dispersion M3 in the transmission signal of the optical relay device. M3 can be calculated as M3 = M2 + DS2 × Leff2 = DS1 × Leff1 + DS2 × Leff2.

[0082] The wavelength dispersion compensation amount calculation unit 130 of the control device 100 then calculates the cumulative wavelength dispersion compensation amount M5 for the optical relay device 200 to compensate for wavelength dispersion using phase conjugation, using the formula M5 = M4 × 2.

[0083] The chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the difference M6 between the cumulative chromatic dispersion amount M3 and the cumulative chromatic dispersion compensation amount M5, and transmits the difference M6 as the optimal chromatic dispersion compensation amount to the optical relay device 200. The control device 100 also transmits control information to the optical relay device 200, including an instruction to perform phase conjugation processing. As a result, the node control unit 202 of the optical relay device 200 instructs the phase conjugation processing unit 232 to perform phase conjugation processing calculation based on the acquired control information including the instruction to perform phase conjugation processing, as explained with reference to Figures 9 and 10. The phase conjugation processing unit 232 performs phase conjugation processing calculation. The node control unit 202 of the optical relay device 200 also sets the chromatic dispersion compensation amount M6 notified by the control device 100 to the chromatic dispersion compensation unit 231 in the digital signal processing unit 230, as explained with reference to Figure 9. In other words, if the wavelength dispersion compensation unit 231 is configured as an FDE as shown in Figure 9, the node control unit 202 sets the transfer function coefficients of the inverse transfer function multiplication unit 413 in Figure 9 according to the wavelength dispersion compensation amount M6 notified by the control device 100. As a result, the optical relay device 200 calculates the cumulative wavelength dispersion M3 (M3 = M4 - M5 - M6) after calculating the cumulative wavelength dispersion compensation amount M5 using the phase conjugation processing of the phase conjugation processing unit 232 and performing wavelength dispersion compensation using the wavelength dispersion compensation amount M6 of the wavelength dispersion compensation unit 231 for the downstream optical transmission path 3b, and outputs an optical signal with this cumulative wavelength dispersion M3 (Figure 11B). This suppresses nonlinear effects in the receiving terminal device 40.

[0084] Furthermore, the optical relay device 200 can calculate the cumulative chromatic dispersion amount M3 without performing phase conjugation using the formula M3 = M2 + DS2 × Leff2 = DS1 × Leff1 + DS2 × Leff2. Therefore, the chromatic dispersion compensation unit 231 of the optical relay device 200 may calculate the cumulative chromatic dispersion amount M3 and output an optical signal that has the cumulative chromatic dispersion amount M3 without performing phase conjugation (Figure 11B). In the explanation of Figures 11A and 11B, for the sake of explanation, it is explained that an optical signal with wavelength λ1 is transmitted in the optical transmission path 3a and an optical signal with wavelength λ2 is transmitted in the optical transmission path 3b. However, a multi-channel optical signal with multiple wavelengths λ (frequency bands) may be transmitted in the optical transmission path 3a, and a multi-channel optical signal with multiple wavelengths λ (frequency bands) may also be transmitted in the optical transmission path 3b.

[0085] Figure 11C shows an overview of the phase conjugation process. As shown in Figure 11C, in a certain span of the optical network 51 (between the transmitting station terminal equipment 30 and network devices such as the optical repeater 200 in Figure 11C), nonlinear distortion of the transmitted signal occurs as signal degradation due to nonlinear effects (1111 in Figure 11C). Phase conjugation processing (inversion of the optical signal) is performed in the optical repeater 200. This allows for the cancellation of nonlinear distortion using phase conjugation in the span downstream of the optical repeater 200 (between the optical repeater 200 and the receiving station equipment 40), thereby reducing signal degradation (nonlinear distortion) in the receiving station equipment 40. In addition, by performing wavelength dispersion compensation, the cancellation effect of in-channel nonlinear distortion in the receiving station equipment 40 can be increased.

[0086] The processing in the control device 100 described above is one aspect of the process which determines the amount of wavelength dispersion compensation to be compensated in the optical relay device 200 based on the wavelength information of the optical signals transmitted and received by the optical relay device 200 that constitute the optical network in the optical network path and the transmission path information of the optical transmission path connected to the optical relay device 200, and determines the phase conjugate processing in the optical relay device 200 based on the wavelength information and the transmission path information.

[0087] Furthermore, one aspect of the processing in the control device 100 is the transmission of an instruction to the optical relay device 200 to perform phase conjugation processing to calculate the complex conjugate of the optical signal based on the cumulative wavelength dispersion amount M4 of the optical signal received by the optical relay device 200.

[0088] Furthermore, a part of the processing in the control device 100 is one aspect of the process of calculating a first cumulative wavelength dispersion amount M1 at a first effective nonlinear distance (Leff1) with respect to the transmitting network device in the first optical transmission path (previous path) between the optical relay device 200 and the transmitting network device that transmits the optical signal received by the optical relay device 200.

[0089] Furthermore, one aspect of the processing in the control device 100 is a process for calculating a second cumulative chromatic dispersion (M2) at a second effective nonlinear distance (Leff2) of the optical signal in the second optical transmission path (later path) between the optical relay device 200 and the receiving network device of the optical signal transmitted by the optical relay device 200, with respect to the device itself, and which is a second cumulative chromatic dispersion (M2) with the opposite sign (multiplied by minus 1) of the first cumulative chromatic dispersion.

[0090] Furthermore, one aspect of the processing in the control device 100 is a process that calculates a wavelength dispersion compensation amount (M6) which is the difference between the wavelength dispersion amount (M3) at the time of transmission of the optical signal in the optical relay device 200 when the cumulative wavelength dispersion amount of the optical signal becomes the second cumulative wavelength dispersion amount (M2) at the second effective nonlinear distance (Leff2), based on statistical values ​​(DS2) of the change in the cumulative wavelength dispersion amount of the optical signal according to the distance in the second optical transmission path, and the wavelength dispersion amount (M5) which is the result of complex conjugation.

[0091] The processing of the optical relay device 200 described above is one aspect of the process which involves performing wavelength dispersion compensation processing on an electrical signal based on a received optical signal based on a wavelength dispersion compensation amount (M6), and performing phase conjugation processing on an electrical signal based on a received optical signal based on phase conjugation processing information acquired from the control device 100.

[0092] Furthermore, some of the processing in the optical relay device 200 described above is one form of processing that performs phase conjugation processing based on the cumulative wavelength dispersion amount of the optical signal received by the device and an instruction to perform phase conjugation processing to calculate the complex conjugate of the optical signal.

[0093] Furthermore, some of the processing in the optical relay device 200 described above is one aspect of the process that, after performing phase conjugation, determines the chromatic dispersion amount (M3) of the optical signal to be transmitted to the receiving network device based on the chromatic dispersion amount (M5), which is the result of complex conjugation, and the chromatic dispersion compensation amount (M6) obtained from the control device 100.

[0094] Figure 11D is the first diagram illustrating the overview of the frequency flip process. The frequency flip processing unit 233 of the optical relay device 200 performs frequency flip processing on a channel-by-channel basis for each channel of the received multi-channel optical signal. Here, as shown in Figure 11D, the optical signal is assumed to have received signals in two frequency bands, channel 1 and channel 2. Channel 1 is assumed to contain signals of frequencies L11 to L1n on the lower frequency side, and signals of frequencies R11 to R1n on the higher frequency side, with the center frequency in between. Channel 2 is assumed to contain signals of frequencies L21 to L2n on the lower frequency side, with the center frequency in between, and signals of frequencies R21 to R2n on the higher frequency side.

[0095] Assume that the frequency flip processing unit 233 of the optical repeater 200 is instructed to perform frequency flip processing on channels 1 and 2. In this case, the optical repeater 200 performs frequency flip processing on channel 1, inverting the signal components of each frequency L11 to L1n on the low-frequency side and the signal components of each frequency R11 to R1n on the high-frequency side, with respect to the center frequency of channel 1. Similarly, the frequency flip processing unit 233 of the optical repeater 200 performs frequency flip processing on channel 2, inverting the signal components of each frequency L21 to L2n on the low-frequency side and the signal components of each frequency R21 to R2n on the high-frequency side, with respect to the center frequency of channel 2.

[0096] As a result, the optical repeater 200 outputs an optical signal that includes signal components R1n to R11 on the lower frequency side with respect to the center frequency of channel 1, and signal components L1n to L11 on the higher frequency side with respect to the center frequency of channel 1. The optical repeater 200 also outputs an optical signal that includes signal components R2n to R21 on the lower frequency side with respect to the center frequency of channel 2, and signal components L2n to L21 on the higher frequency side with respect to the center frequency of channel 2. The order of the frequency components in each region is reversed by frequency flipping.

[0097] The frequency flipping process described above reduces inter-channel correlation by moving the frequency domain R1 on the channel 2 side within the frequency band of channel 1 and the frequency domain L2 on the channel 1 side within the frequency band of channel 2 further apart, thereby reducing inter-channel nonlinear effects. With high baud rate signals, the transmission bandwidth widens, allowing the regions of R1 and L2 to be moved even further apart. This reduces inter-channel nonlinear effects caused by frequency flipping.

[0098] Here, the optical relay device 200 may perform frequency flip processing on a channel-by-channel basis for all channels of the received optical signal. Alternatively, the optical relay device 200 may receive multiple channels with different frequency bands, sequentially identify channels to be processed and channels not to be processed from among these multiple channels which are arranged sequentially based on their frequency bands, and perform frequency flip processing on the channels to be processed. The channels to be processed and channels not to be processed for frequency flip processing may be identified by the optical relay device 200 itself, or they may be identified based on instructions from the control device 100.

[0099] Figure 11E is a second diagram illustrating the overview of the frequency flip process. Assume that the optical repeater 200 has received optical signals in the frequency bands of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The frequency flip processing unit 233 of the optical repeater 200 determines, based on instructions from the control unit 100 or on its own decision, that it will perform frequency flip processing on the second channel 2ch, which is the second of the three channels. This causes the signal component in the frequency domain of the first channel 1ch on the second channel 2ch side to move away from the signal component in the frequency domain of the second channel 2ch on the first channel 1ch side, thereby reducing the nonlinear effect between the first channel 1ch and the second channel 2ch. Similarly, the signal component in the frequency domain of the second channel 2ch on the third channel 3ch side to move away from the signal component in the frequency domain of the third channel 3ch on the second channel 2ch side, thereby reducing the nonlinear effect between the second channel 2ch and the third channel 3ch.

[0100] Figure 11F is a third diagram illustrating the overview of the frequency flip process. Assume that the optical repeater 200 has received optical signals in the frequency bands of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The frequency flip processing unit 233 of the optical repeater 200 determines, based on instructions from the control unit 100 or based on its own decision, that it will perform frequency flip processing on all three channels. This makes it possible to similarly reduce the nonlinear effects between the first channel 1ch and the second channel 2ch, and between the second channel 2ch and the third channel 3ch.

[0101] Figure 12 shows another embodiment of the wavelength dispersion compensation amount by the control method in this embodiment. Unlike Figure 11B, in this example, as shown in Figure 12, the transmitting terminal device 30 transmits an optical signal with a cumulative wavelength dispersion amount M10 to the optical transmission path 3a. Note that if the transmitting terminal device 30 is an optical relay device 200 in the optical network 51, dispersion such as a cumulative wavelength dispersion amount M10 may occur in the optical signal transmitted by the transmitting terminal device 30.

[0102] As shown in Figure 12, in the optical transmission path 3a preceding the optical relay device 200, the wavelength of the optical signal is λ1. Therefore, the control device 100 determines the slope DS1 of the chromatic dispersion in the optical transmission path 3a according to the wavelength λ1. The control device 100 uses the effective nonlinear distance Leff1 to determine the accumulated chromatic dispersion M11 (=DS1 × Leff1 + M10) at the effective nonlinear distance Leff1 in the optical transmission path 3a preceding the device.

[0103] Furthermore, since the wavelength of the optical signal in the subsequent optical transmission path 3b is λ2, the control device 100 determines the slope DS2 of the chromatic dispersion in the optical transmission path 3b according to the wavelength λ2. The control device 100 calculates the cumulative chromatic dispersion M13 (=DS1×Leff1+DS2×Leff2+M10) in the transmitted signal of the optical relay device, provided that the cumulative chromatic dispersion M12 at the effective nonlinear distance Leff2 in the subsequent optical transmission path 3b has a different sign than the cumulative chromatic dispersion M11 at the effective nonlinear distance Leff1 in the preceding optical transmission path 3a. The control device 100 calculates the phase conjugate compensation amount M15 (=M14×2) which is compensated by phase conjugate in the optical relay device 200.

[0104] The control device 100 calculates the difference M16 between M13 and M15, and sets M6 as the optimal wavelength dispersion compensation amount to the optical relay device 200. The control device 100 also sets the optical relay device 200 to perform phase conjugation processing.

[0105] As described above, in this embodiment, in an optical relay device that performs wavelength conversion on a channel-by-channel basis, the analog signal output from the optical receiving front end is converted into a digital signal by an ADC, digital signal processing is performed, and then it is converted back into an analog signal by a DAC and relayed back to the optical transmitting front end. At this time, the digital signal processing unit performs phase conjugation processing, compensation for wavelength dispersion distortion occurring in the optical fiber transmission line according to the transmission line length of the network path (transmission line), and frequency flip processing on a channel-by-channel basis.

[0106] Specifically, the control device 100 determines the optimal wavelength dispersion compensation amount to be compensated by the optical repeater so that the cumulative wavelength dispersion amount at the effective nonlinear distance in the preceding transmission line and the cumulative wavelength amount at the effective nonlinear distance in the subsequent transmission line are of opposite signs. The optical repeater 200 then performs phase conjugation, frequency flip processing on a channel-by-channel basis, and wavelength dispersion compensation using the determined optimal wavelength dispersion compensation amount. This cancels out the nonlinear distortion accumulated in the preceding optical transmission line at the receiving end of the optical repeater through optical transmission in the subsequent optical transmission, maximizing the effect of suppressing nonlinear distortion at the receiving terminal station. Furthermore, even if the transmitted signal from the transmitting terminal station contains extra dispersion as shown in Figure 12, the optical repeater can set an appropriate wavelength dispersion amount to compensate for the nonlinear distortion. In addition, inter-channel nonlinear distortion can be reduced by frequency flip processing on a channel-by-channel basis.

[0107] (Embodiment 2) Next, Embodiment 2 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 in Embodiment 1. Figures 13A and 13B show specific examples of wavelength dispersion compensation amounts by the control method in this embodiment. In this embodiment, the case where the number of spans of the optical network is an odd number of 3 or more will be described, and in particular, an example where the number of spans is 3 will be described.

[0108] As shown in Figure 13A, optical repeaters 200a (first optical repeater) and 200b (second optical repeater) are arranged on the path between the transmitting terminal device 30 and the receiving terminal device 40. The transmitting terminal device 30 and optical repeater 200a are connected via optical transmission path 3a (first optical transmission path), optical repeater 200a and optical repeater 200b are connected via optical transmission path 3b (second optical transmission path), and optical repeater 200b and receiving terminal device 40 are connected via optical transmission path 3c (third optical transmission path). For example, the distances L1 of optical transmission path 3a, L2 of optical transmission path 3b, and L3 of optical transmission path 3c may be different or the same. An optical signal with wavelength λ1 is transmitted through optical transmission path 3a, an optical signal with wavelength λ2 is transmitted through optical transmission path 3b, and an optical signal with wavelength λ3 is transmitted through optical transmission path 3c. In optical transmission path 3a, multi-channel optical signals of multiple wavelengths λ (frequency bands) may be transmitted; in optical transmission path 3b, multi-channel optical signals of multiple wavelengths λ (frequency bands) may also be transmitted; and in optical transmission path 3c, optical signals of multiple wavelengths λ (frequency bands) may also be transmitted.

[0109] In the case of an odd number of total spans, such as 3 or more in Embodiment 2, the control of the control device 100 according to the method of Embodiment 1 is applied to combinations of two spans, such as optical transmission path 3a and optical transmission path 3b. For the remaining optical transmission path 3, such as optical transmission path 3c, the control device 100 sets an optimal dispersion compensation amount in the last optical relay device 200 (optical relay device 200b in this embodiment) that constitutes the optical network 51, so as to suppress nonlinear distortion when optical transmission is performed over one span in the optical transmission path 3 (optical transmission path 3c in this embodiment).

[0110] As shown in Figure 13B, the optical relay device 200a performs phase conjugation processing and calculates the wavelength dispersion compensation amount M26 based on the control of the control device 100, applying Embodiment 1. The compensated wavelength dispersion amount M26 in the optical relay device 200a is determined by the same method as in Embodiment 1. The control device 100 sets the dispersion compensation amount M26 applied to Embodiment 1 to the optical relay device 200a. The control device 100 also sets the optical relay device 200a to perform phase conjugation processing.

[0111] Furthermore, the optical repeater 200b compensates for the optimal chromatic dispersion compensation amount such that the nonlinear effect is minimized in one span of optical transmission in the optical transmission path 3c, based on the control of the control device 100. The control device 100 determines the slope DS3 of the chromatic dispersion amount in the optical transmission path 3c according to the wavelength λ3. The control device 100 determines the chromatic dispersion M28 (=DS3 × L3') of the transmitted signal of the optical repeater 200b, provided that the cumulative chromatic dispersion of the transmitted signal in the optical transmission path 3c is zero at the effective nonlinear distance L3'. The control device 100 determines the cumulative chromatic dispersion amount M27 accumulated in the optical transmission path 3b.

[0112] The control device 100 sets the optical repeater 200c to compensate for the wavelength dispersion amount M27 + M28, based on the calculated wavelength dispersion amounts M27 and M28, as M27 + M28. The control device 100 also sets the optical repeater 200c so that it does not perform phase conjugation processing.

[0113] If the total number of spans is an odd number N, which is 5 or more, the control device 100 identifies a combination consisting of one optical relay device and two optical transmission lines that can implement Embodiment 1, similar to the case of a total span of 3 shown in Embodiment 2. For each identified combination of optical relay devices, the control device 100 sets the phase conjugate and optimal wavelength dispersion compensation according to Embodiment 1. For the remaining optical transmission line among the N spans, the control device 100 sets the optimal wavelength dispersion compensation amount for the optical relay device that minimizes nonlinear distortion in the transmission of one span.

[0114] Each relay device 200 may perform frequency flip processing on a specified channel, as in the other embodiments described above.

[0115] As described above, this embodiment suppresses nonlinear distortion at the receiving end, especially in cases with an odd number of spans. Specifically, a combination consisting of one optical relay device and two optical transmission lines is set up so that Embodiment 1 can be implemented, and phase conjugation and chromatic dispersion compensation according to Embodiment 1 are set for the optical relay device in each combination. For the remaining optical transmission lines, the optimal chromatic dispersion compensation amount shown in Embodiment 2 is set so that the nonlinear distortion is minimized in one span. Therefore, in an optical network consisting of an odd number of transmission lines, the effect of canceling out nonlinear distortion during optical transmission using chromatic dispersion compensation can be maximized, and the signal quality at the receiving end can be improved.

[0116] (Embodiment 3) Next, Embodiment 3 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 in Embodiment 1. Figures 14A and 14B show specific examples of wavelength dispersion compensation amounts by the control method in this embodiment. In this embodiment, the case where the number of spans of the optical network is an even number of four or more, and an example with four spans will be described.

[0117] As shown in Figure 14A, optical repeaters 200a (first optical repeater), 200b (second optical repeater), and 200c are arranged along the path between the transmitting terminal device 30 and the receiving terminal device 40. The transmitting terminal device 30 and optical repeater 200a are connected via optical transmission path 3a (first optical transmission path), optical repeater 200a and optical repeater 200b are connected via optical transmission path 3b (second optical transmission path), optical repeater 200b and optical repeater 200c are connected via optical transmission path 3c (third optical transmission path), and optical repeater 200c and receiving terminal device 40 are connected via optical transmission path 3d (fourth optical transmission path). For example, the distances L1 of optical transmission path 3a, L2 of optical transmission path 3b, L3 of optical transmission path 3c, and L4 of optical transmission path 3d may be different or the same. In optical transmission path 3a, an optical signal with wavelength λ1 is transmitted; in optical transmission path 3b, an optical signal with wavelength λ2 is transmitted; in optical transmission path 3c, an optical signal with wavelength λ3 is transmitted; and in optical transmission path 3d, an optical signal with wavelength λ4 is transmitted. Two or more of these wavelengths λ1 to λ4 may be the same, or they may be different. In optical transmission path 3a, a multi-channel optical signal with multiple wavelengths λ (frequency bands) may be transmitted; in optical transmission path 3b, a multi-channel optical signal with multiple wavelengths λ (frequency bands) may be transmitted; in optical transmission path 3c, a channel optical signal with multiple wavelengths λ (frequency bands) may be transmitted; and in optical transmission path 3d, a channel optical signal with multiple wavelengths λ (frequency bands) may be transmitted.

[0118] As shown in Figure 14B, in the case of a total of 4 spans in Embodiment 3, for example, the control of the control device 100 according to Embodiment 1 is applied to two spans, optical transmission path 3a and optical transmission path 3b, and the control of the control device 100 according to Embodiment 1 is also applied to two spans, optical transmission path 3c and optical transmission path 3d.

[0119] The control device 100 sets information for the optical relay device 200a to perform dispersion compensation and phase conjugation processing, applying the control of the control device 100 according to Embodiment 1. In other words, the control device 100 sets the optical relay device 200a with the optimal wavelength dispersion compensation amount M36 obtained by applying the control of the control device 100 according to Embodiment 1. Furthermore, the control device 100 sets the optical relay device 200a to perform phase conjugation processing in the same manner as in Embodiment 1.

[0120] The control device 100 sets information for the optical relay device 200c to perform dispersion compensation and phase conjugation processing, applying the control of the control device 100 according to Embodiment 1 to the optical relay device 200c as well. In other words, the control device 100 sets the optical relay device 200c to the optimal wavelength dispersion compensation amount M44 obtained by applying the control of the control device 100 according to Embodiment 1 to the optical relay device 200c. Furthermore, the control device 100 sets the optical relay device 200c to perform phase conjugation processing in the same manner as in Embodiment 1.

[0121] The control device 100 determines the slope DS2 of the chromatic dispersion in the optical transmission path 3b according to the wavelength λ2. The control device 100 calculates the cumulative chromatic dispersion M37 (=DS2 × L2 + M33) accumulated in the optical transmission path 3b.

[0122] The control device 100 sets the optical repeater 200b to compensate for the wavelength dispersion amount M37 - M38, which is calculated from the wavelength dispersion amount M37 and the dispersion amount M38 of the transmitted signal in the optical transmission path 3c that is smaller than M37. The control device 100 also sets the optical repeater 200b so that it does not perform phase conjugation processing.

[0123] If the total number of spans is an even number of six or more, the control device 100 sets a combination consisting of one optical relay device and two optical transmission lines, similar to the case of four total spans shown in Embodiment 3, so that Embodiment 1 can be implemented. The control device 100 sets the phase conjugate and optimal wavelength dispersion compensation according to Embodiment 1 for each combination of optical relay devices.

[0124] Each relay device 200 may perform frequency flip processing on a specified channel, as in the other embodiments described above.

[0125] As described above, this embodiment compensates for nonlinear distortion at the receiving end in the case of multiple spans, particularly in the case of an even number of spans. Specifically, a combination consisting of one optical relay device and two optical transmission lines is set up so that Embodiment 1 can be implemented, and phase conjugation and chromatic dispersion compensation according to Embodiment 1 are set for the optical relay device in each combination. Therefore, in an optical network consisting of an even number of transmission lines, the effect of canceling out nonlinear distortion during optical transmission using chromatic dispersion compensation can be maximized, and the signal quality at the receiving end can be improved.

[0126] Figure 15 shows the minimum configuration of the control device. Figure 16 shows the processing flow using a minimal control device configuration. The control device 100 includes at least a wavelength dispersion compensation control means 151 and a phase conjugate processing control means 152. The wavelength dispersion compensation control means 151 determines the amount of wavelength dispersion compensation to be compensated by the optical relay device 200 based on the wavelength information of the optical signals transmitted and received by the optical relay device 200 that constitute the optical network in the optical network path and the transmission path information of the optical transmission path connected to the optical relay device 200 (step S161). The phase conjugation processing control means 152 determines the phase conjugation processing in the optical relay device 200 based on the wavelength information and the transmission path information (step S162).

[0127] Figure 17 shows the minimum configuration of an optical relay device. Figure 18 shows the processing flow using a minimal optical relay device. The optical relay device 200 includes at least a wavelength dispersion compensation means 171 and a phase conjugate processing means 172. The phase-conjugate processing means 172 performs phase-conjugate processing on the electrical signal based on the received optical signal based on the acquired phase-conjugate processing information (step S181). The wavelength dispersion compensation means 171 performs wavelength dispersion compensation processing on the electrical signal based on the received optical signal based on the wavelength dispersion compensation amount (step S182).

[0128] In other embodiments, the optical relay device 200 may perform some or all of the processing of the control device 100.

[0129] Figure 19 shows another configuration of the optical relay device. Figure 20 shows the processing flow using an optical relay device with a different configuration. In other embodiments, the optical relay device 200 may further include, in addition to the chromatic dispersion compensation means 171 and the phase conjugate processing means 172, a chromatic dispersion compensation control means 191 and a phase conjugate processing control means 192, as shown in Figure 19. The wavelength dispersion compensation control means 191 determines the amount of wavelength dispersion compensation to be compensated by the optical repeater 200 based on the wavelength information of the optical signals transmitted and received by the device (optical repeater 200) that constitutes the optical network in the optical network path and the transmission path information of the optical transmission path connected to the optical repeater 200 (step S2001). The phase conjugation processing control means 192 determines the phase conjugation processing in the optical relay device 200 based on the wavelength information and the transmission path information (step S2002). In this case, the wavelength dispersion compensation control means 191 and the phase conjugate processing control means 192 may perform the same processing as the control device 100 described above. Furthermore, when the optical relay device 200 performs the processing of the wavelength dispersion compensation control means 191 and the phase conjugate processing control means 192, it may obtain the same information necessary for the processing as the control device 100 described above from the control device 100.

[0130] In other embodiments, the optical relay device 200 may, in addition to the chromatic dispersion compensation means 171 and the phase conjugate processing means 172, include at least one of the chromatic dispersion compensation control means 191 and the phase conjugate processing control means 192, with the remaining means provided in the control device 100.

[0131] Figure 21 shows another configuration of the optical relay device. Figure 22 shows the processing flow using an optical relay device with a different configuration. In other embodiments, the optical relay device 200 includes frequency flip processing means 280. The frequency flip processing means 280 performs frequency flip processing on a channel-by-channel basis for at least one or more channels of the optical signal (step S2201).

[0132] The control device, optical relay device, transmitting terminal device, and receiving terminal device in the above-described embodiment are composed of hardware, software, or both, and may consist of one piece of hardware or software, or 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 as a storage device, as shown in Figure 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 with the processor 61.

[0133] These programs, when loaded into a computer, include a set of instructions (or software code) for causing the computer to perform one or more of the functions described in the embodiments. The programs may be stored on non-temporary computer-readable media or tangible storage media. Examples, but not limited to, include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drives (SSDs), or other memory technologies, CD-ROMs, digital versatile discs (DVDs), Blu-ray® discs, or other optical disc storage, magnetic cassettes, magnetic tapes, magnetic disk storage, or other magnetic storage devices. The programs may be transmitted over temporary computer-readable media or communication media. Examples, but not limited to, include electrical, optical, acoustic, or other forms of propagating signals.

[0134] Furthermore, some or all of the above embodiments may also be described as follows, but are not limited to these.

[0135] (Note 1) The system comprises an optical relay device that constitutes an optical network, and a control device that controls the optical relay device. The control device is Management means for managing wavelength information of optical signals transmitted and received by the optical relay device in the optical network path and transmission path information of the optical transmission path connected to the optical relay device, A wavelength dispersion compensation control means for determining the amount of wavelength dispersion compensation to be compensated in the optical relay device based on the wavelength information and the transmission path information, A phase conjugation processing control means for determining phase conjugation processing in the optical relay device based on the wavelength information and the transmission path information, Equipped with, The optical relay device is, A means for acquiring the determined wavelength 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-conjugation processing means performs phase-conjugation processing on an electrical signal based on a received optical signal based on the acquired phase-conjugation processing information, A wavelength dispersion compensation means that performs wavelength dispersion compensation processing on an electrical signal based on a received optical signal based on the acquired wavelength dispersion compensation amount, An optical network system equipped with [the following features].

[0136] (Note 2) The wavelength dispersion compensation control means determines the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the receiving side of the optical relay device and the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the transmitting side of the optical relay device, based on the wavelength information and transmission path information on the receiving side of the optical relay device and the wavelength information and transmission path information on the transmitting side of the optical relay device. The optical network system described in Appendix 1.

[0137] (Note 3) The wavelength dispersion compensation control means determines the wavelength dispersion compensation amount based on the accumulated wavelength dispersion amount at the effective nonlinear distance in the optical transmission path on the receiving side of the optical relay device, the accumulated wavelength dispersion amount at the effective nonlinear distance in the optical transmission path on the transmitting side of the optical relay device, and the wavelength dispersion compensation amount by phase conjugation processing in the optical relay device. The optical network system described in Appendix 2.

[0138] (Note 4) The wavelength dispersion compensation control means determines the wavelength dispersion compensation amount based on the amount of accumulated wavelength dispersion included in the transmitted signal before optical transmission in the optical transmission path on the receiving side of the optical relay device, the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the receiving side of the optical relay device, the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the transmitting side of the optical relay device, and the wavelength dispersion compensation amount by phase conjugation processing in the optical relay device. An optical network system as described in any one of the appendices 1 through 3.

[0139] (Note 5) The aforementioned wavelength dispersion compensation amount is a compensation amount determined on the condition that the accumulated wavelength dispersion amount at the effective nonlinear distance in the optical transmission path on the receiving side of the optical relay device and the accumulated wavelength dispersion amount at the effective nonlinear distance in the optical transmission path on the transmitting side of the optical relay device have opposite signs. An optical network system as described in any one of the appendices 1 through 4.

[0140] (Note 6) In an optical network comprising three or more odd-numbered paths connected via optical relay devices, the wavelength dispersion compensation control means and the phase conjugation processing control means determine the wavelength dispersion compensation amount and phase conjugation processing in the target optical relay device based on the wavelength information and transmission path information in the paths before and after the target optical relay device, excluding the optical relay device connected to the last path among the plurality of paths. The optical network system according to claim 1.

[0141] (Note 7) The wavelength dispersion compensation control means and the phase conjugate processing control means determine, in the optical relay device, combinations of two paths, a preceding and succeeding stage, and one optical relay device that relays those paths, as a set, and the remaining one path, and determine that the optical relay device other than the one connected to the remaining one path is the target optical relay device. An optical network system as described in any one of the appendices 1 through 6.

[0142] (Note 8) The phase conjugate processing control means determines the phase conjugate processing for the optical relay device in the combination. The optical network system described in Appendix 7.

[0143] (Note 9) The wavelength dispersion compensation control means determines the amount of wavelength dispersion compensation in the optical relay device of the combination based on the wavelength information and transmission path information in the two optical transmission paths of the combination. An optical network system as described in either Appendix 7 or Appendix 8.

[0144] (Note 10) The wavelength dispersion compensation control means determines the amount of wavelength dispersion compensation in the optical relay device of the remaining one path based on the wavelength information and transmission path information in the optical transmission path of the remaining one path. The optical network system described in Appendix 7.

[0145] (Note 11) The aforementioned wavelength dispersion compensation amount is a compensation amount determined on the condition that the cumulative wavelength dispersion amount over the effective nonlinear distance in the optical transmission path of the remaining one path becomes zero. An optical network system as described in any one of the appendices 7 through 10.

[0146] (Note 12) In an optical network comprising four or more even-numbered paths connected via the optical relay device, the wavelength dispersion compensation control means and the phase conjugation processing control means determine the wavelength dispersion compensation amount and phase conjugation processing in the optical relay device based on the wavelength information and transmission path information in the paths before and after each of the optical relay devices in the plurality of paths. An optical network system as described in any one of the appendices 7 through 11.

[0147] (Note 13) The wavelength dispersion compensation control means and the phase conjugate processing control means determine a combination of two optical transmission paths and one optical relay device in the optical relay device. An optical network system as described in any one of the appendices 1 through 12.

[0148] (Note 14) The phase conjugate processing control means determines the phase conjugate processing for the optical relay device in the combination. An optical network system as described in any one of the appendices 7 through 13.

[0149] (Note 15) The wavelength dispersion compensation control means determines the amount of wavelength dispersion compensation in the optical relay device of the combination based on the wavelength information and transmission path information in the two optical transmission paths of the combination. An optical network system as described in any one of the appendices 7 through 14.

[0150] (Note 16) The optical network manages the wavelength information of optical signals transmitted and received by optical relay devices in the optical network path, the transmission path information of the optical transmission path connected to the optical relay device, and the number of paths in the optical network. Based on the wavelength information, the transmission path information, and the number of paths in the optical network, the optical relay device determines the amount of wavelength dispersion compensation to be compensated and the phase conjugate processing. Control method.

[0151] (Note 17) Based on the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the receiving side of each optical relay device in the optical network path, and the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the transmitting side of the optical relay device, the wavelength dispersion compensation amount and phase conjugation processing are determined. The control method described in Appendix 16.

[0152] (Note 18) The optical network manages the wavelength information of optical signals transmitted and received by optical relay devices in the optical network path, the transmission path information of the optical transmission path connected to the optical relay device, and the number of paths in the optical network. Based on the wavelength information, the transmission path information, and the number of paths in the optical network, the optical relay device determines the amount of wavelength dispersion compensation to be compensated and the phase conjugate processing. A control program that instructs a computer to perform a process.

[0153] (Note 19) Based on the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the receiving side of each optical relay device in the optical network path, and the amount of accumulated wavelength dispersion at the effective nonlinear distance in the optical transmission path on the transmitting side of the optical relay device, the wavelength dispersion compensation amount and phase conjugation processing are determined. The program described in Appendix 18.

[0154] (Note 20) A wavelength dispersion compensation control means that determines the amount of wavelength dispersion compensation to be compensated by the optical relay device based on the wavelength information of the optical signals transmitted and received by the optical relay device constituting the optical network and the transmission path information of the optical transmission path connected to the optical relay device in the path of the optical network, A phase conjugation processing control means for determining the phase conjugation processing in the optical relay device based on the wavelength information and the transmission path information, A control device equipped with the following features.

[0155] (Note 21) The phase conjugation processing control means transmits an instruction to the optical relay device to perform phase conjugation processing for calculating the complex conjugate of the optical signal. The control device described in Appendix 20.

[0156] (Note 22) The wavelength dispersion compensation control means is The first cumulative wavelength dispersion amount is calculated in the first effective nonlinear distance with respect to the transmitting network device in the first optical transmission path between the optical relay device and the transmitting network device that transmits the optical signal received by the optical relay device, among the optical transmission paths to which the optical relay device is connected. The optical relay device calculates a second cumulative chromatic dispersion amount in a second effective nonlinear distance of the optical signal with respect to the device itself in the second optical transmission path between the optical relay device and the receiving network device of the optical signal transmitted by the optical relay device, which is a second cumulative chromatic dispersion amount with a different sign from the first cumulative chromatic dispersion amount. The wavelength dispersion compensation amount is calculated based on statistical values ​​of the progression of the cumulative wavelength dispersion amount of the optical signal according to the distance in the second optical transmission path, where the cumulative wavelength dispersion amount of the optical signal at the second effective nonlinear distance becomes the second cumulative wavelength dispersion amount, and the wavelength dispersion amount which is the result of the complex conjugate. The control device described in Appendix 21.

[0157] (Note 23) A wavelength dispersion compensation control means that determines the amount of wavelength dispersion compensation to be compensated by the device in an optical network path based on the wavelength information of the optical signals transmitted and received by the device and the transmission path information of the optical transmission path connected to the device, A phase conjugation processing control means that determines the phase conjugation processing in the device based on the wavelength information and the transmission path information, An optical relay device that communicates with a control device equipped with the same device, A phase-conjugate processing means performs phase-conjugate processing on an electrical signal based on a received optical signal based on phase-conjugate processing information acquired from the control device, A wavelength dispersion compensation means that performs wavelength dispersion compensation processing on an electrical signal based on a received optical signal based on the wavelength dispersion compensation amount, An optical relay device equipped with the following features.

[0158] (Note 24) The phase conjugation processing means performs the phase conjugation processing based on an instruction to perform the phase conjugation processing for calculating the complex conjugate of the optical signal. The optical relay device described in Appendix 23.

[0159] (Note 25) The first cumulative wavelength dispersion amount is calculated in the first effective nonlinear distance with respect to the transmitting network device in the first optical transmission path between the optical relay device and the transmitting network device that transmits the optical signal received by the optical relay device, among the optical transmission paths to which the optical relay device is connected. The optical relay device calculates a second cumulative chromatic dispersion amount in a second effective nonlinear distance of the optical signal with respect to the device itself in the second optical transmission path between the optical relay device and the receiving network device of the optical signal transmitted by the optical relay device, which is a second cumulative chromatic dispersion amount with a different sign from the first cumulative chromatic dispersion amount. The control and communication connection are established to calculate the wavelength dispersion compensation amount, which is the difference between the wavelength dispersion amount at the time of transmission of the optical signal in the optical relay device and the wavelength dispersion amount resulting from the complex conjugate, based on statistical values ​​of the transition of the cumulative wavelength dispersion amount of the optical signal according to the distance in the second optical transmission path, when the cumulative wavelength dispersion amount of the optical signal at the second effective nonlinear distance becomes the second cumulative wavelength dispersion amount. A wavelength dispersion compensation means that, after performing the phase conjugation process, determines the wavelength dispersion amount of the optical signal to be transmitted to the receiving network device based on the wavelength dispersion amount which is the result of the complex conjugation and the wavelength dispersion compensation amount obtained from the control device, An optical relay device as described in Appendix 24, comprising:

[0160] (Note 26) Digital signal processing means that performs frequency flip processing on a channel-by-channel basis for at least one or more channels of optical signals, An optical relay device equipped with the following features.

[0161] (Note 27) The digital signal processing means performs the frequency flip processing on a channel-by-channel basis for all channels of the optical signal. The optical relay device described in Appendix 26.

[0162] (Note 28) The digital signal processing means sequentially identifies channels to be processed and channels not to be processed from among a plurality of channels with different frequency bands, arranged sequentially based on the frequency band, and performs the frequency flip process on the channels to be processed. The optical relay device described in Appendix 26 or Appendix 27.

[0163] (Note 29) The digital signal processing means performs the frequency flip process, which inverts the frequency components of the optical signal for each frequency based on a reference frequency set at the center of the frequency band. An optical relay device as described in any one of the appendices 26 to 28.

[0164] (Note 30) The aforementioned digital signal processing means is A phase-conjugation processing means that performs phase-conjugation processing on an electrical signal based on the received optical signal, A wavelength dispersion compensation means that performs wavelength dispersion compensation processing on an electrical signal based on the received optical signal, The frequency flip processing means that performs the frequency flip processing, An optical relay device as described in any one of the appendices 26 to 29, comprising the above.

[0165] (Note 31) The frequency flip processing means performs the phase conjugation process and the wavelength dispersion compensation process for all channels of the optical signal, and performs the frequency flip process on a channel-by-channel basis for at least one channel. An optical relay device as described in any one of the appendices 26 to 30. [Explanation of Symbols]

[0166] 1. Optical Network System 2. Optical relay device 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 unit 13. Wavelength dispersion compensation control unit 14. Frequency Flip Control Unit 20. Optical relay device 21. Coherent receiving front-end section 22. Phase-conjugate 23...chromatic dispersion compensation section 24. Coherent transmission front-end section 25. Phase conjugate acquisition section 26...Chromatic dispersion compensation acquisition section 27. Frequency flip instruction acquisition unit 28. Frequency flip processing unit 30. Transmitting terminal equipment 40. Receiving terminal equipment 50. Optical Network System 51. Optical Network 60... Computers 61 Processor 62...memory 90... Optical relay device 100... Control device 110...Network Management Department 120...Network Control Unit 130...Chromatic dispersion compensation amount calculation section 140...Phase Conjugate Determination Unit 150... Frequency flip indicator 200... Optical relay device 201... Optical transceiver 202...Node Control Unit 210... Coherent receiving front end 220... Coherent transmission front-end section 230...Digital signal processing unit 231...chromatic dispersion compensation section 232... Phase Conjugate Processing Unit 233...Frequency flip 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 section 310...Transmitter / Receiver Unit 311, 312, 313, 314... Optical transceivers 401... Delay device 402... Multiplier 403... Adder 411... Overlap addition 412...Fast Fourier Transform section 413...Inverse transfer function multiplication section 414...Inverse Fast Fourier Transform section 415... Overlap removal section 900... Digital signal processing unit 910...Acquisition part 901...Digital signal processing unit

Claims

1. Digital signal processing means that performs frequency flip processing on a channel-by-channel basis for at least one or more channels of an optical signal. An optical relay device comprising, The digital signal processing means sequentially identifies channels to be processed and channels not to be processed from among a plurality of channels with different frequency bands, arranged sequentially based on the frequency band, and performs the frequency flip process on the channels to be processed. Optical relay device.

2. The digital signal processing means performs the frequency flip processing on a channel-by-channel basis for all channels of the optical signal. The optical relay device according to claim 1.

3. The digital signal processing means performs the frequency flip process, which inverts the frequency components of the optical signal for each channel, based on a reference frequency set in the center of the frequency band. The optical relay device according to claim 1 or 2.

4. The aforementioned digital signal processing means is A phase-conjugation processing means that performs phase-conjugation processing on an electrical signal based on the received optical signal, A wavelength dispersion compensation means that performs wavelength dispersion compensation processing on an electrical signal based on the received optical signal, The frequency flip processing means that performs the frequency flip processing, The optical relay device according to claim 3, comprising:

5. The digital signal processing means performs the phase conjugation process and the wavelength dispersion compensation process for all channels of the optical signal, and performs the frequency flip process on a channel-by-channel basis for at least one channel. The optical relay device according to claim 4.

6. Digital signal processing means perform frequency flip processing on a channel-by-channel basis for at least one or more channels of optical signals. A method of optical relay, From among the multiple channels with different frequency bands, the channels to be processed and those not to be processed are sequentially identified from the multiple channels arranged sequentially based on the frequency band, and the frequency flip process is performed on the channels that are to be processed. Optical relay method.

7. The computer of the optical relay device, Digital signal processing means that performs frequency flip processing on a channel-by-channel basis for at least one channel of an optical signal, It is a program that makes it function as such. The digital signal processing means sequentially identifies channels to be processed and channels not to be processed from among a plurality of channels with different frequency bands, arranged sequentially based on the frequency band, and causes the channel to be processed to perform the frequency flip processing. program.

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