Optical relay device, optical network system, optical relay method, and program

Abstract

To provide an optical relay device, an optical network system, an optical relay method, and a program which suppress deterioration of signal quality in optical transmission.SOLUTION: In the optical network system 1, each of the plurality of optical relay devices 2 monitors the rotation angle from the reference angle of the polarization indicated by each of the plurality of signal channels included in the optical signal, and adjusts the rotation angle from the reference angle of the polarization of each signal channel to a rotation angle at which the reception characteristic of each signal channel is improved, using a control value for controlling the rotation angle from the reference angle of the polarization of any one of the plurality of signal channels.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

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

[0004] A related technique is known, for example, in Patent Document 1. Paragraph 0045 and elsewhere in Patent Document 1 discloses a technique in which an optical transmission system includes an optical fiber transmission line, an optical repeater, a polarization tracking device, and an optical receiver, and includes a transmission line polarization detection device that detects the polarization of an optical signal or an amount dependent thereon, a polarization management device that observes polarization fluctuations in the optical signal input to the optical receiver from the amount detected by the transmission line polarization detection device and controls the output polarization of the polarization multiplexed transmitter so as to eliminate the polarization fluctuations, and a system management device that transmits the amount of polarization fluctuation detected by the transmission line polarization detection device to the polarization management device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-146795 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology related to the optical network system described above, it is required to suppress the degradation of signal quality in optical transmission.

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

[0008] An optical repeater according to one aspect of the present disclosure includes a monitor means for monitoring the rotation angle from a reference angle of polarization indicated by a plurality of signal channels included in an optical signal, and a calculation means for adjusting the rotation angle from a reference angle of polarization of each signal channel to a rotation angle that improves the reception characteristics of each signal channel using a control value that controls the rotation angle from a reference angle of polarization of any one of the plurality of signal channels.

[0009] An optical network system according to one aspect of the present disclosure comprises an optical repeater and a control device, wherein the optical repeater comprises a monitor means for monitoring the rotation angle from a reference angle of polarization indicated by a plurality of signal channels included in an optical signal, and a calculation means for adjusting the rotation angle from a reference angle of polarization of each signal channel to a rotation angle that improves the reception characteristics of each signal channel using a control value that controls the rotation angle from a reference angle of polarization of any of the plurality of signal channels, and the control device comprises a management means for calculating the control value based on the reception characteristics of the optical signal in a downstream device that receives the optical signal relayed by the optical repeater, and outputting the control value to the optical repeater.

[0010] An optical relay method according to one aspect of the present disclosure monitors the rotation angles of polarization from a reference angle indicated by multiple signal channels included in an optical signal, and adjusts the rotation angle of polarization from the reference angle of each signal channel from the multiple signal channels to a rotation angle that improves the reception characteristics of each signal channel using a control value that controls the rotation angle of polarization from the reference angle of any one of the multiple signal channels.

[0011] A program according to one aspect of the present disclosure causes a computer of an optical repeater device to function as a monitor means for monitoring the rotation angle from a reference angle of polarization indicated by a plurality of signal channels included in an optical signal, and a calculation means for adjusting the rotation angle from a reference angle of polarization of each signal channel to a rotation angle that improves the reception characteristics of each signal channel using a control value that controls the rotation angle from a reference angle of polarization of any of the plurality of signal channels. [Effects of the Invention]

[0012] According to the above aspect, it is possible to suppress deterioration of signal quality in optical transmission. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a configuration diagram showing an example of the configuration of an optical network system according to a basic example. [Figure 2] FIG. 1 is a configuration diagram showing an example of the configuration of an optical repeater according to a basic example. [Figure 3] 1 is a diagram illustrating a configuration of an optical transceiver according to the present disclosure. [Figure 4A] 1A and 1B are diagrams for explaining problems with the optical transceiver according to the present disclosure. [Figure 4B] 1A and 1B are diagrams for explaining problems with the optical transceiver according to the present disclosure. [Figure 5] 1 is a configuration diagram showing a schematic configuration of a control device according to the present disclosure. [Figure 6] 1 is a diagram illustrating a schematic configuration of an optical repeater according to the present disclosure. [Figure 7]1 is a configuration diagram illustrating a configuration example of an optical network system according to an embodiment of the present disclosure. [Figure 8] 1 is a configuration illustrating an example of the configuration of each device in an optical network system according to an embodiment of the present disclosure. [Figure 9A] FIG. 1 is a conceptual diagram illustrating a specific example of carrier frequency control using a control method according to an embodiment of the present disclosure. [Figure 9B] FIG. 1 is a conceptual diagram illustrating a specific example of carrier frequency control using a control method according to an embodiment of the present disclosure. [Figure 9C] FIG. 1 is a conceptual diagram illustrating a specific example of carrier frequency control using a control method according to an embodiment of the present disclosure. [Figure 10] 1 is a configuration illustrating an example of the configuration of each device in an optical network system according to an embodiment of the present disclosure. [Figure 11] FIG. 2 is a diagram illustrating a configuration example of a chromatic dispersion compensation unit according to an embodiment of the present disclosure. [Figure 12A] FIG. 1 is a conceptual diagram illustrating a specific example of chromatic dispersion compensation according to an embodiment of the present disclosure. [Figure 12B] FIG. 1 is a conceptual diagram illustrating a specific example of chromatic dispersion compensation according to an embodiment of the present disclosure. [Figure 13] 10 is a flowchart illustrating an example of operation of an optical network system according to an embodiment of the present disclosure. [Figure 14A] FIG. 10 is a diagram illustrating a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 14B] FIG. 10 is a diagram illustrating a specific example of chromatic dispersion compensation by a control method according to an embodiment of the present disclosure. [Figure 14C] FIG. 1 is a diagram illustrating an overview of phase conjugation processing according to an embodiment of the present disclosure. [Figure 15] 1 is a configuration illustrating an example of the configuration of each device in an optical network system according to an embodiment of the present disclosure. [Figure 16] FIG. 10 is a diagram illustrating another example configuration of each device in the optical network system according to an embodiment of the present disclosure. [Figure 17]10A and 10B are diagrams illustrating changes in reception characteristics according to the difference in the rotation angle of polarization of two signal channels included in an optical signal according to an embodiment of the present disclosure. [Figure 18] FIG. 10 is a diagram illustrating monitor characteristics of a polarization monitor according to an embodiment of the present disclosure. [Figure 19] FIG. 10 is a diagram illustrating an overview of a process for matching the rotation angles of each signal channel in a digital signal processing unit according to an embodiment of the present disclosure. [Figure 20] FIG. 10 is a functional block diagram of another example optical repeater according to an embodiment of the present disclosure. [Figure 21] FIG. 10 is a diagram illustrating a processing flow of an optical repeater according to another example embodiment of the present disclosure. [Figure 22] FIG. 1 is a configuration diagram illustrating an overview of the hardware of a computer according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the optical network system, control method, control program, control device, and optical repeater of the present disclosure will be described with reference to the drawings. In each drawing, the same elements are given the same reference numerals, and duplicated explanations will be omitted as necessary. Note that arrows in the configuration diagrams (block diagrams) are for illustrative purposes only and do not limit the type or direction of signals.

[0015] (Considerations leading to the embodiment) 1 shows the configuration of an optical network system according to a basic example that forms the basis of this embodiment. The optical network system 1 according to the basic example is, for example, a backbone wavelength multiplexing optical transmission system, in which devices that constitute the system perform wavelength multiplexing of optical signals and perform high-level modulation and digital coherent transmission of optical signals of each wavelength, thereby achieving high-capacity communications of over 100 Gbps. High-density wavelength multiplexing makes it possible to improve the efficiency of optical frequency utilization, and can accommodate mobile traffic and wavelength defragmentation.

[0016] The optical network system 1 includes optical repeaters 2 (e.g., 2-1 to 2-10) that can flexibly switch transmission paths (wavelength paths or optical transmission paths) of optical signals as they are to switch transmission paths in the event of a failure or to accommodate local traffic demands (e.g., communication traffic demands from data centers 4 and 5, the network of an IT service provider 6, and the networks of event venues 7 and 8). The optical network system 1 can maintain communications using optical signals as an infrastructure by including the optical repeaters 2 (e.g., 2-1 to 2-10). The optical repeaters 2 are photonic nodes that can relay wavelength-multiplexed optical signals, such as ROADM (Reconfigurable Optical Add / Drop Multiplexer) devices. A wavelength path (also simply referred to as a path) is assigned to each optical repeater 2, and the optical repeater 2 forwards traffic from its corresponding local network or other optical repeater 2 to a destination network or other communication device via an optical communication cable that transmits optical signals of the assigned wavelength path.

[0017] 2 shows an example of the configuration of an optical repeater 2 according to the basic example. The optical repeater 2 drops / adds an optical wavelength-multiplexed signal, and coherently modulates / demodulates the signals of each wavelength that are dropped / added. As shown in FIG. 2, the optical repeater 2 includes an optical switch unit 300 and a transmitter / receiver unit 310.

[0018] The optical switch unit 300 transfers optical signals of a predetermined wavelength path received from a previous-stage optical repeater 2 in the optical network system 1 to a subsequent-stage optical repeater 2, and also drops / adds the received optical signals for each wavelength. For example, the optical switch unit 300 includes a demultiplexer 301, a multiplexer 302, and an add / drop unit 303. The demultiplexer 301 separates optical signals received from the optical transmission line 3 into optical signals of multiple wavelengths. The multiplexer 302 multiplexes optical signals of multiple wavelengths into one optical signal and transmits it to the optical transmission line 3. The add / drop unit 303 drops / adds optical signals of each wavelength between the demultiplexer 301 and the multiplexer 302.

[0019] The transceiver unit (transponder) 310 receives optical signals of each wavelength branched from the add / drop unit 303 of the optical switch unit 300, and outputs the coherently demodulated received data to a local device (network). The transceiver unit 310 also inputs transmission data from the local device, and transmits (adds) coherently modulated optical signals of each wavelength to the add / drop unit 303 of the optical switch unit 300. The transceiver unit 310 includes a plurality of optical transceivers 311 that transmit and receive optical signals of each wavelength. The optical transceiver 311 receives an optical signal of a predetermined wavelength, and further transmits an optical signal of a predetermined wavelength (the same as or different from the received wavelength) to a destination.

[0020] Here, we will consider issues that arise when an optical transceiver is used as the optical transceiver 311. Fig. 3 shows an example configuration of an optical transceiver according to this disclosure. As shown in Fig. 3, the optical transceiver 311 according to this disclosure includes a coherent receiver front-end unit 210, a coherent transmitter front-end unit 220, an acquisition unit 910, and a digital signal processor 901. Digital signal processing enables phase conjugation processing and chromatic dispersion compensation on a channel-by-channel basis.

[0021] The coherent receiver front-end unit 210 coherently detects an optical signal received from the optical repeater 2 at the previous stage using local oscillator light (LO light) of a predetermined wavelength, and outputs the detected signal to the digital signal processing unit 901. The coherent transmitter front-end unit 220 optically modulates (coherently modulates) the signal processed by the digital signal processing unit 901 to a predetermined wavelength, and transmits the generated optical signal to the optical repeater 2 at the next stage. The digital signal processing unit 901 is a DSP (Digital Signal Processor), and converts the signal coherently detected by the coherent receiver front-end unit 210 into a digital signal, outputs signal-processed received data, and recovers input transmission data and outputs a signal converted for optical modulation to the coherent transmitter front-end unit 220. In this disclosure, the digital signal processing unit 901 performs phase conjugation processing and chromatic dispersion compensation on a channel-by-channel basis.

[0022] 4A and 4B show the amount of chromatic dispersion when an optical repeater 90 including an optical transceiver 311 according to this disclosure is used. As shown in FIG. 4A, the optical repeater 90 is connected between a transmitting terminal device (transmitting end) 30 and a receiving terminal device (receiving end) 40 via optical transmission lines 3a and 3b. The optical transmission line 3a has a distance L1, and the optical transmission line 3b has a distance L2, and L1 and L2 may be the same length or different lengths. An optical signal with a wavelength λ1 is transmitted through the optical transmission line 3a, and an optical signal with a wavelength λ2 is transmitted through the optical transmission line 3b.

[0023] 4A, the side of the optical repeater 90 on the transmitting terminal device 30 side may be referred to as the upstream side of the optical repeater 90 (the receiving side of the optical signal), and the side of the optical repeater 90 on the receiving terminal device 40 side may be referred to as the downstream side of the optical repeater 90 (the transmitting side of the optical signal). Also, the optical transmission path between the optical repeater 90 and the transmitting terminal device 30 may be referred to as the upstream side (first portion) optical transmission path, and the optical transmission path between the optical repeater 90 and the receiving terminal device 40 may be referred to as the downstream side (second portion) optical transmission path.

[0024] As shown in Figure 4B, the amount of chromatic dispersion increases in proportion to the distance of the optical transmission path. Therefore, if the optical repeater 90 relays an optical signal by simply amplifying the signal, the amount of chromatic dispersion will continue to increase with the distance from the transmitting terminal device 30 to the receiving terminal device 40. As a result, as the distance of the optical transmission path increases, the quality of the optical signal received at the receiving terminal device 40 will deteriorate 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 of a material changes in proportion to the optical signal intensity as the optical signal propagates through an optical fiber, causing a change in the phase of the light itself. Such nonlinear distortion is a factor that limits the ability to increase the baud rate and multi-value of optical signals, thereby increasing capacity and long-distance transmission.

[0025] In the example disclosed above, when the optical repeater 90 connected to the path from the transmitting terminal device 30 to the receiving terminal device 40 receives an optical signal consisting of one or more optical channels, the optical repeater 90 performs digital signal processing equivalent to phase conjugation and chromatic dispersion compensation on each received channel. In the example disclosed above, by performing phase conjugation and chromatic dispersion compensation in the optical repeater 90, the nonlinear distortion occurring in the upstream transmission path and the nonlinear distortion occurring in the downstream transmission path in the phase conjugate light transmitted from the optical repeater 90 cancel each other out, thereby mitigating the effects of nonlinear distortion in the receiving terminal device 40, which is the receiving end.

[0026] In the above disclosed example, the effect of intra-channel nonlinear distortion in an optical transmission line is compensated for. Intra-channel nonlinear distortion refers to nonlinear distortion occurring in a single channel during single-channel transmission in the optical transmission line.

[0027] In addition to the examples disclosed above, it is desirable to obtain a sufficient inter-channel nonlinear distortion compensation effect when there are multiple optical channels in an optical transmission signal transmitted through an optical fiber. This disclosure makes it possible to compensate for inter-channel nonlinear effects during multi-channel transmission in an optical repeater in a multiple optical transmission network. Note that nonlinear distortion includes intra-channel nonlinear distortion and inter-channel nonlinear distortion. Intra-channel nonlinear distortion refers to nonlinear distortion occurring in a channel due to the optical signal of that channel. On the other hand, inter-channel nonlinear distortion refers to nonlinear distortion occurring in a channel due to the optical signal of a channel other than the channel in question when multiple optical channels are transmitted through an optical transmission path.

[0028] This embodiment is outlined below. When an optical repeater receives an optical signal consisting of multiple channels, it performs optical phase conjugation to compensate for inter-channel nonlinear distortion in addition to intra-channel nonlinear distortion, and optimal chromatic dispersion compensation and carrier frequency interchange according to the channel frequency band. Furthermore, although the effect of compensating for intra-channel nonlinear distortion and inter-channel nonlinear distortion is reduced, either optimal chromatic dispersion compensation or carrier frequency interchange according to the channel band may be used.

[0029] (Outline of the embodiment) Fig. 5 shows a schematic configuration of a control device according to this embodiment. Fig. 6 shows a schematic configuration of an optical repeater according to this embodiment. The control device 10 and the optical repeater 20 constitute an optical network system. The optical repeater 20 according to this embodiment constitutes a part of the optical network system, and the control device 10 according to this embodiment controls the optical repeater 20, which is another component of the optical network system.

[0030] As shown in FIG. 5, the control device 10 includes a management unit 11, a phase conjugate control unit 12, a chromatic dispersion compensation control unit 13, and a carrier frequency control unit 14. The management unit 11 manages transmission line information of an optical transmission line connected to an optical repeater 20 in a path of an optical network. The phase conjugate control unit 12 determines the phase conjugation processing in the optical repeater 20 based on the transmission line information managed by the management unit 11 and wavelength information managed by the carrier frequency control unit 14. The chromatic dispersion compensation control unit 13 determines the amount of chromatic dispersion compensation to be performed in the optical repeater 20 based on the transmission line information managed by the management unit 11 and the carrier frequency managed by the carrier frequency control unit. The carrier frequency control unit 14 identifies the order of magnitude of frequency values ​​in the frequency domain of each channel of an optical signal consisting of multiple channels received by the optical repeater 20, and controls the carrier frequency of the transmission signal of each channel so that the order of magnitude of frequency values ​​in the frequency domain of each channel in the transmission signal is reversed.

[0031] As shown in Fig. 6, the optical repeater 20 includes a coherent receiving front-end unit 21, a phase conjugation unit 22, a chromatic dispersion compensation unit 23, a coherent transmitting front-end unit 24, a phase conjugation acquisition unit 25, a chromatic dispersion compensation acquisition unit 26, and a carrier frequency acquisition unit 27. Although not shown in Fig. 6, the optical repeater transmits and receives multiple optical channels, and performs phase conjugation, chromatic dispersion compensation, and carrier frequency setting for the signal of each channel.

[0032] The phase conjugate acquisition unit 25 acquires the phase conjugate processing determined by the phase conjugate control unit 12 from the control device 10. The chromatic dispersion compensation acquisition unit 26 acquires the amount of chromatic dispersion compensation determined by the chromatic dispersion compensation control unit 13 from the control device 10. The carrier frequency acquisition unit 27 acquires information on the reception carrier frequency and transmission carrier frequency of each channel determined by the carrier frequency control unit 14. The coherent receiver front-end unit 21 coherently detects the received optical signal based on the local oscillation light of the reception carrier frequency acquired from the carrier frequency acquisition unit 27, and outputs the coherently detected electrical signal. The phase conjugate unit 22 performs phase conjugation processing by digital signal processing on the electrical signal output from the coherent receiver front-end unit 21 based on the phase conjugate processing setting acquired by the phase conjugate acquisition unit 25. The chromatic dispersion compensation unit 23 performs chromatic dispersion compensation processing by digital signal processing on the electrical signal output from the phase conjugate unit 22 based on the amount of chromatic dispersion compensation acquired by the chromatic dispersion compensation acquisition unit 26. The coherent transmission front-end unit 24 coherently modulates the electrical signal that has been subjected to phase conjugation processing by the phase conjugation unit 22 and the electrical signal that has been subjected to chromatic dispersion compensation processing by the chromatic dispersion compensation unit 23 based on the local light of the transmission carrier frequency acquired from the carrier frequency acquisition unit 27, and transmits the coherently modulated optical signal.

[0033] As described above, in the embodiment, the control device 10 determines the phase conjugation processing and the amount of chromatic dispersion compensation in the optical repeater 20 based on wavelength information and signal bandwidth information of the optical signals transmitted and received by the optical repeater 20 in the path, and transmission line information of the optical transmission line connected to the optical repeater 20. The control device 10 performs the determined phase conjugation processing and chromatic dispersion compensation amount in the optical repeater 20 to compensate for nonlinear distortion. The control device 10 also specifies the order of magnitude of frequency values ​​in the frequency domain of each channel of the optical signal consisting of multiple channels received by the optical repeater 20, and controls the carrier frequency so that the order of magnitude of frequency values ​​in the frequency domain of each channel in the transmission signal is reversed, thereby compensating for the nonlinear effect between channels.

[0034] By performing phase conjugation of the optical signal in the optical repeater 20, the distortion of the optical signal can be reversed in the optical transmission path upstream of the optical repeater 20. As the signal propagates through the optical transmission path downstream of the optical repeater 20, the distortion is reversed and canceled out at the receiving end. According to the embodiment described below, the optical repeater 20 can perform chromatic dispersion compensation using an appropriate phase conjugation and chromatic dispersion compensation amount. Therefore, by using phase conjugation and chromatic dispersion compensation in each optical repeater 20 in a multi-span optical network, it is possible to maximize the cancellation effect of nonlinear distortion caused by multi-span optical transmission, and effectively suppress degradation of signal quality due to nonlinear distortion at the receiving end of the optical network. Furthermore, by selecting the optimal chromatic dispersion compensation in the optical repeater 20 according to the carrier frequency and signal bandwidth, and by selecting a carrier frequency that reverses the order of frequency values ​​in the frequency domain of each channel in a multi-channel optical signal, nonlinear effects between channels can also be suppressed.

[0035] (Embodiment 1) Next, a first embodiment will be described with reference to the drawings. Fig. 7 shows a configuration example of an optical network system according to an embodiment of the present disclosure. As shown in Fig. 7, an optical network system 50 according to an embodiment of the present disclosure includes a control device 100, a plurality of optical repeaters 200, a transmitting terminal device 30, and a receiving terminal device 40.

[0036] The plurality of optical repeaters 200, the transmitting terminal device 30, and the receiving terminal device 40 are connected to each other via an optical transmission path 3 so that they can communicate with each other optically. The plurality of optical repeaters 200, the transmitting terminal device 30, and the receiving terminal device 40 are connected to the control device 100 so that they can communicate with each other control signals. The plurality of optical repeaters 200, the transmitting terminal device 30, and the receiving terminal device 40 may be connected to the control device 100 via the optical transmission path 3, or may be connected to each other via any other transmission path including wired or wireless so that they can communicate with each other.

[0037] The multiple optical repeaters 200, the transmitting terminal device 30, and the receiving terminal device 40 are optical transmission devices (optical nodes) that perform optical communication via an optical transmission path 3. The transmitting terminal device 30 constitutes the transmitting end of a path formed by connecting multiple optical transmission paths 3. The receiving terminal device 40 constitutes the receiving end of a path formed by connecting multiple optical transmission paths 3. The transmitting terminal device 30 transmits multi-channel optical signals wavelength-multiplexed using the wavelengths of the path set by the control device 100 to the receiving terminal device 40 via the optical transmission path 3. The receiving terminal device 40 receives multi-channel optical signals wavelength-multiplexed using the wavelengths of the path set by the control device 100 from the transmitting terminal device 30 via the optical transmission path 3.

[0038] Similar to the basic example, the multiple optical repeaters 200 are repeaters capable of repeating wavelength-multiplexed multi-channel optical signals. The multiple optical repeaters 200 constitute an optical network 51 for performing WDM communication. It can also be said that the multiple optical repeaters 200, together with the transmitting terminal device 30 and the receiving terminal device 40, constitute the optical network 51. The optical network 51 is a wavelength-multiplexed optical network, similar to FIG. 1. The optical network 51 may be a mesh-shaped network, a ring-shaped network, a point-to-point network, or a network of other topologies. Furthermore, the multiple optical repeaters 200 form a path from the transmitting terminal device 30 to the receiving terminal device 40 under the control of the control device 100, and transmit optical signals (data) at wavelengths set on the path route.

[0039] The control device 100 manages and controls an optical network 51 including a plurality of optical repeater devices 200. For example, the control device 100 is an NMS (Network Management System) that manages the network.

[0040] The control device 100 manages and controls paths formed by optical repeater devices 200 in the optical network 51. The control device 100 manages the route and wavelength of the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the route and wavelength of the path for the transmitting terminal device 30, the receiving terminal device 40, and the optical repeater devices 200 on the path.

[0041] 8 shows an example of the configuration of each device in an optical network system according to an embodiment of the present disclosure. As shown in Fig. 8, the control device 100 includes a network management unit 110, a network control unit 120, a chromatic dispersion compensation amount calculation unit 130, a phase conjugation determination unit 140, and a carrier frequency control unit 150.

[0042] The network management unit 110 corresponds to the management unit 11 shown in FIG. 5 and manages information necessary for network management, such as network configuration information and path configuration information in the optical network 51. For example, the network management unit 110 may be configured as a database that stores information necessary for network management. The network configuration information includes the connection relationships of the optical repeater devices 200, the transmitting terminal device 30, and the receiving terminal device 40 that constitute the network, as well as transmission path information of the optical transmission path 3 that connects each device. The transmission path information includes the distance L (transmission path length) of the optical transmission path, and may also include the structure, type, and transmission characteristics of the optical fiber. The path configuration information includes information about each device that constitutes the path, the wavelengths that each device can use on the path, and the wavelength usage status. This information may be set in advance in a database, or may be set based on information collected from each device, and may also be updated by the network control unit 120, etc.

[0043] The network control unit 120 corresponds to the management unit 11 shown in FIG. 5 and controls paths in the optical network 51 and the optical repeater devices 200, transmitting terminal devices 30, and receiving terminal devices 40 that constitute the paths. The network control unit 120 references network configuration information, path configuration information, etc. in the network management unit 110, determines the route of the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the determined route in the transmitting terminal device 30, the receiving terminal device 40, and the optical repeater devices 200 on the path route. The network control unit 120 also outputs information required for calculating the amount of chromatic dispersion compensation in the optical repeater devices 200 that constitute the path to the chromatic dispersion compensation amount calculation unit 130. For example, the network control unit 120 outputs transmission path information of the optical transmission paths before and after. The network control unit 120 also outputs phase conjugation determination information in the optical repeater devices 200 that constitute the path to the phase conjugation determination unit 140. For example, the network control unit 120 outputs the number of paths and the number of optical repeaters in the optical network 51.

[0044] The chromatic dispersion compensation amount calculation unit 130 corresponds to the chromatic dispersion compensation control unit 13 shown in FIG. 5 and calculates the amount of chromatic dispersion compensation required for the optical repeater 200 constituting the path to perform chromatic dispersion compensation. The chromatic dispersion compensation amount calculation unit 130 is a compensation control unit that determines and controls the amount of chromatic dispersion compensation for the optical repeater 200. The chromatic dispersion compensation amount calculation unit 130 determines the optimal amount of chromatic dispersion compensation for the optical repeater 200 based on the receiving wavelength information, signal band, transmitting wavelength information, and transmission path information before and after the optical repeater, of the optical repeater 200, which are obtained from the network control unit 120 and the carrier frequency control unit 150. The chromatic dispersion compensation amount calculation unit 130 notifies the corresponding optical repeater 200 of the receiving wavelength information, transmitting wavelength information, and optimal amount of chromatic dispersion compensation for the optical repeater 200.

[0045] 5, and controls the phase conjugation process of the optical repeater 200 that constitutes the path. The phase conjugation process determining unit 140 determines the optimal phase conjugation process for the optical repeater 200 based on the number of paths and the number of optical repeaters in the optical network 51 obtained from the network control unit 120. The phase conjugation process determining unit 140 notifies the optical repeater 200 of the phase conjugation process information.

[0046] The carrier frequency control unit 150 corresponds to the carrier frequency control unit 14 shown in Fig. 5 and determines the carrier frequency of each channel of the optical signal in the path from the transmitting terminal device 30 to the receiving terminal device 40, and sets the determined carrier frequency in the transmitting terminal device 30, the receiving terminal device 40, and the optical repeater devices 200 on the path route. The carrier frequency of the light in the path is determined for each optical transmission line on the path route. In addition, the carrier frequency control unit 150 outputs information required for calculating the amount of chromatic dispersion compensation in the optical repeater devices 200 that make up the path to the chromatic dispersion compensation amount calculation unit 130. For example, the carrier frequency control unit 150 outputs reception wavelength information (wavelength information of the received optical signal) and transmission wavelength information (wavelength information of the transmitted optical signal) of the optical repeater device 200.

[0047] Assume that the optical repeater 200 receives an optical signal consisting of multiple channels. The carrier frequency selector 150 determines the order of the frequency values ​​of the multiple channels arranged in order based on the frequency band among the multiple channels with different frequency bands of the optical signal received by the corresponding optical repeater 200, and determines the carrier frequency of each channel in the transmission signal based on the carrier frequency and signal band of each channel of the received signal so that the order is reversed in the transmission signal. The carrier frequency selector 150 notifies the corresponding optical repeater 200 of the determined carrier frequencies of each channel of the received signal and the transmission signal.

[0048] 9A is a first diagram showing an overview of carrier frequency settings for channel shuffling instructed by the carrier frequency selector 150. Assume that the optical repeater 200 receives signals in the frequency bands of a first channel (1ch), a second channel (2ch), and a third channel (3ch). The carrier frequencies of each channel are f1, f2, and f3, respectively, and the signal bands of each channel are Δf1, Δf2, and Δf3, respectively. The carrier frequency controller 150 sets the carrier frequency of each channel so that the output signal received by the optical repeater 200 has a reverse order of frequency values ​​in the frequency domain of each channel. If the signal band widths of each channel are all the same, the order of frequency values ​​of each channel is reversed by setting the carrier frequency of 1ch to f3, the carrier frequency of 2ch to f2, and the carrier frequency of 3ch to f1.

[0049] FIG. 9B is a second diagram illustrating an outline of carrier frequency setting for channel shuffling instructed by the carrier frequency selector 150. Assume that the optical repeater 200 receives signals in the frequency bands of the first channel 1ch, the second channel 2ch, and the third channel 3ch. The carrier frequencies of each channel are f1, f2, and f3, respectively, and the signal bands are Δf1, Δf2, and Δf3, respectively. Assume that the widths of the signal bands indicated by Δf1, Δf2, and Δf3 are not equivalent. The carrier frequency control unit 150 sets the carrier frequency of each channel so that the output signal received by the optical repeater 200 has a reversed order of frequency values ​​in the frequency domain of each channel. The carrier frequencies of the channels 1ch, 2ch, and 3ch of the output signal from the optical repeater 200 are set to f3′ (=f2+(f2-f1)), f2, and f1′ (=f2-(f3-f2)), thereby reversing the order of frequency values ​​of each channel. The optical repeater 200 outputs optical signals by setting the signal bandwidth width of each channel to be the same when receiving and transmitting the optical repeater 200. In other words, the signal bandwidths of channels 1ch, 2ch, and 3ch when transmitting from the optical repeater 200 are Δf1, Δf2, and Δf3, respectively, which are the same as the signal bandwidths when receiving.

[0050] FIG. 9C is a third diagram illustrating an outline of carrier frequency settings for channel shuffling instructed by the carrier frequency selector 150. Assume that the optical repeater 200 receives signals in the frequency bands of the first channel (ch1), the second channel (ch2), and the third channel (ch3). The carrier frequencies of these channels are f1, f2, and f3, respectively, and the signal bands are Δf1, Δf2, and Δf3, respectively. The carrier frequency controller 150 sets the carrier frequency of each channel so that the order of the frequency values ​​in the frequency domain of each channel received by the optical repeater 200 is reversed and a uniform frequency offset Δf is applied to each channel in the output signal. By setting the carrier frequencies of channels 1, 2, and 3 of the output signal from the optical repeater 200 to f3+Δf, f2+Δf, and f1+Δf, the order of the frequency values ​​of each channel is reversed and an optical signal with a uniform frequency offset is transmitted. This allows a transmission signal having a different band from the band of the optical signal received by the optical repeater 200 to be transmitted to the path, making it possible to apply the present invention to a wavelength conversion repeater system in which the optical repeater converts the wavelengths of the received signal and the transmitted signal.

[0051] In the optical network 51, a multi-channel optical signal is relayed by a plurality of optical repeaters 200 via an optical transmission line 3. When a plurality of optical repeaters 200 in the optical network 51 change the channel order for a given channel of the optical signal, they notify the receiving terminal device 40 of the carrier frequency at the receiving end of that channel.

[0052] 8, an optical repeater 200 according to an embodiment of the present disclosure includes an optical transceiver 201 and a node control unit 202. Although not shown in FIG. 8, in order to transmit and receive multiple optical channels, the optical repeater 200 includes an optical switch unit 300 and a transceiver unit 310, and the transceiver unit 310 includes multiple optical transceivers 201, similar to the basic example in FIG. 2. That is, the node control unit 202 can control the optical switch unit 300 and the transceiver unit 310 (multiple optical transceivers 201 (corresponding to the optical transceiver 311 in FIG. 3)).

[0053] The optical transceiver 201 includes a coherent receiving front-end unit 210, a coherent transmitting front-end unit 220, a digital signal processing unit 230, a receiving light source 240, a transmitting light source 250, an ADC 260, and a DAC 270. The number of digital signal processing units 230 may correspond to the number of channels included in the optical signal.

[0054] The receiving light source 240 generates local light r1 of a wavelength (frequency) set by the node control unit 202 and outputs the generated local light r1 to the coherent receiving front end unit 210. The transmitting light source 250 generates transmission light r2 of a wavelength (frequency) set by the node control unit 202 and outputs the generated transmission light r2 to the coherent transmitting front end unit 220.

[0055] The frequency (wavelength) of the local light r1 is the frequency (carrier frequency) of the received input optical signal SO1, and the frequency of the transmitted light r2 is the frequency of the transmitted output optical signal SO2. The carrier frequencies of the local light r1 and r2 are determined based on carrier frequency information acquired by the node control unit 202 from the carrier frequency control unit 150.

[0056] The coherent receiver front-end unit 210 and the coherent transmitter front-end unit 220 have the same configuration as in Fig. 3. The coherent receiver front-end unit 210 is an optical / electrical converter that converts an optical signal into an electrical signal, and is a coherent detector that performs coherent detection. The coherent receiver front-end unit 210 coherently detects the input optical signal SO1 (received optical signal) based on the local oscillator light r1, and outputs the generated analog signal SA1 (first analog electrical signal).

[0057] The ADC (Analog / Digital Converter) 260 performs AD 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).

[0058] The DAC (Digital / Analog Converter) 270 performs digital to analog conversion on the digital signal SD2 (second digital electrical signal) that has been signal processed by the digital signal processing unit 230, and outputs the converted analog signal SA2 (second analog electrical signal).

[0059] The coherent transmission front-end unit 220 is an electrical / optical converter that converts an electrical signal into an optical signal, and a coherent modulator that performs coherent modulation. The coherent transmission front-end unit 220 coherently modulates the analog signal SA2 that has been D / A converted by the DAC 270 based on the transmitted light r2, and outputs the generated output optical signal SO2 (transmitted optical signal).

[0060] For example, input optical signal SO1 and output optical signal SO2 are phase-modulated and polarization-multiplexed optical signals. Analog signals SA1 and SA2 and digital signals SD1 and SD2 are four-lane (4-channel) signals including an IX signal of the I component (in-phase component) of the X polarization, a QX signal of the Q component (quadrature component) of the X polarization, an IY signal of the I component of the Y polarization, and a QY signal of the Q component of the Y polarization.

[0061] The digital signal processing unit 230 performs digital signal processing on the digital signal SD1 converted by the ADC 260 and outputs the processed digital signal SD2. 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 of the IX signal, QX signal, IY signal, and QY signal (X polarization or Y polarization) of the four lanes.

[0062] The digital signal processing unit 230 performs only specific signal processing, without performing processing that involves a large delay, such as code error correction (data recovery). This makes it possible to compensate for the required signal quality while suppressing signal delay. In this embodiment, the digital signal processing unit 230 includes a chromatic dispersion compensation unit 231 (corresponding to the chromatic dispersion compensation unit 23 in FIG. 6) that performs chromatic dispersion processing, and a phase conjugation processing unit 232 (corresponding to the phase conjugation unit 22 in FIG. 6) that performs phase conjugation processing.

[0063] Chromatic dispersion compensation using digital signal processing can be achieved by convolution processing of the impulse response of the inverse transfer function of the optical transmission line and the received signal. For this reason, for example, the chromatic dispersion compensator 231 may be configured using a transversal filter (FIR filter). Since the characteristics of the optical transmission line can be modeled using an FIR filter, chromatic dispersion can be compensated for using an FIR filter with the inverse characteristics. While an FIR filter performs time domain equalization (TDE) that equalizes the received signal in the time delay domain, the same characteristics can also be achieved using frequency domain equalization (FDE) that equalizes the signal in the frequency domain. Configuring the chromatic dispersion compensator using FDE allows for a smaller circuit scale than using an FIR filter.

[0064] In addition to compensating for transmission path wavelength dispersion, the wavelength dispersion compensator 231 may also compensate for bandwidth degradation due to characteristic degradation and characteristic variations of analog electrical circuits in each of the four lanes of the IX signal, QX signal, IY signal, and QY signal, amplitude variations among the four lanes, skew and crosstalk among the four lanes, etc.

[0065] 10 shows another example of the configuration of each device in an optical network system according to an embodiment of the present disclosure. As shown in FIG. 10, a delay adjustment unit 233 of a digital signal processing unit 230 of an optical repeater 200 may provide a delay to correct variations in optical path length within the optical repeater when transmitting and receiving multiple optical signals, and timing deviations that occur in the ADC, DCA, and digital signal processing.

[0066] Fig. 11 shows an example of the configuration of the chromatic dispersion compensator 231 when configured using FDE processing. The chromatic dispersion compensator 231 in Fig. 11 is an example of the configuration of overlap FDE, and includes an overlap adding unit 411, a fast Fourier transform unit 412, a frequency response multiplying unit 413, an inverse fast Fourier transform unit 414, and an overlap removing unit 415.

[0067] The node control unit 202 sets the amount of chromatic dispersion compensation notified by the control device 100 in the chromatic dispersion compensation unit 231 in the digital signal processing unit 230. When the chromatic dispersion compensation unit 231 is configured with an FDE as shown in Fig. 9, the node control unit 202 sets the coefficient of the frequency response multiplication unit 413 in Fig. 9 in accordance with the amount of chromatic dispersion compensation notified by the control device 100 and the carrier frequency and signal band of each channel.

[0068] The overlap adding unit 411 overlaps a portion of the preceding and following signals with respect to the input signal (digital signal). After that, the fast Fourier transform unit 412 converts the overlapped signal into a frequency domain signal by fast Fourier transform (FFT).

[0069] The frequency response multiplier 413 equalizes the amount of chromatic dispersion compensation notified from the control device 100 by multiplying it by the frequency response of chromatic dispersion in the transmission line according to the carrier frequency and signal band of each channel.

[0070] FIG. 12A is a first diagram illustrating an overview of determining the frequency response coefficient of the transmission line chromatic dispersion used in the frequency response multiplier 413, which performs equalization according to the notified chromatic dispersion compensation amount and the carrier frequency and signal bandwidth of each channel. Assume that the optical repeater 200 receives optical signals of a first channel (1ch), a second channel (2ch), and a third channel (3ch). The carrier frequencies of each channel are f1, f2, and f3, and their respective frequency bands are Δf1, Δf2, and Δf3. The curve L at the bottom of FIG. 12A indicates the phase of the chromatic dispersion frequency response. The frequency response multiplier 413 multiplies the signal input from the fast Fourier transform unit 412 by the frequency response coefficient, which is converted from a phase component to a complex component. Note that the complex coefficient used for the frequency application coefficient can be obtained by calculating exp(iθ) from the phase component θ shown by the curve L at the bottom of FIG. 12A. Assume that the digital signal processor 230 first performs phase conjugation processing, followed by chromatic dispersion compensation processing. The frequency response multiplication unit 413 for each channel of the optical repeater 200 multiplies the signal of each channel input from the fast Fourier transform unit 412 by the wavelength dispersion frequency response of each frequency band of the corresponding channel, based on frequency inversion by phase conjugation and the wavelength dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal.

[0071] More specifically, the frequency response multiplication unit 413 identifies a coefficient in the Δf3 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 1, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 1 by this coefficient. Also, the frequency response multiplication unit 413 identifies a coefficient in the Δf2 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 2, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 2 by this coefficient. Also, the frequency response multiplication unit 413 identifies a coefficient in the Δf1 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 3, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 3 by this coefficient. This allows for frequency component inversion due to phase conjugation processing.

[0072] FIG. 12B is a second diagram illustrating an overview of determining the frequency response coefficient of the transmission line chromatic dispersion used by the frequency response multiplier 413, which performs equalization according to the notified chromatic dispersion compensation amount and the carrier frequency and signal bandwidth of each channel. Assume that the optical repeater 200 receives optical signals of a first channel (1ch), a second channel (2ch), and a third channel (3ch). The carrier frequencies of each channel are f1, f2, and f3, and their respective frequency bands are Δf1, Δf2, and Δf3. The curve L at the bottom of FIG. 12B indicates the phase of the chromatic dispersion frequency response. The frequency response multiplier 413 multiplies the signal input from the fast Fourier transform unit 412 by the frequency response coefficient, which is converted from a phase component to a complex component. Assume that the digital signal processor 230 first performs chromatic dispersion compensation processing, and then performs phase conjugation processing.

[0073] The frequency response multiplication unit 413 for each channel of the optical repeater 200 multiplies the signal for each channel input from the fast Fourier transform unit 412 by the chromatic dispersion frequency response for each frequency band of the corresponding channel, based on the chromatic dispersion frequency response for the entire band (Δf1+Δf2+Δf3) of the received signal. More specifically, the frequency response multiplication unit 413 identifies a coefficient in the Δf1 region of the chromatic dispersion frequency response for the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 1, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 1 by that coefficient. The frequency response multiplication unit 413 also identifies a coefficient in the Δf2 region of the chromatic dispersion frequency response for the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 2, and multiplies the signal input from the fast Fourier transform unit 412 corresponding to channel 2 by that coefficient. Furthermore, the frequency response multiplication unit 413 identifies a coefficient in the Δf3 region of the chromatic dispersion frequency response of the entire band (Δf1+Δf2+Δf3) of the received signal as a frequency application coefficient for performing chromatic dispersion compensation for channel 3ch, and multiplies the coefficient by the signal input from the fast Fourier transform unit 412 corresponding to channel 3ch.

[0074] This makes it possible to compensate for differences in group delay characteristics between channels when the optical repeater 200 receives multi-channel signals, and to compensate for nonlinear distortion between channels due to phase conjugation.

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

[0076] Phase conjugation processing using digital signal processing finds the complex conjugate of the input digital signal, that is, inverts the sign of the imaginary component Q in the Ix signal, Qx signal, Iy signal, and Qy signal, as shown in the following equation (1).

[0077]

number

[0078] The node control unit 202 receives control information from the control device 100 and controls each unit of the optical repeater 200 based on the received control information. The node control unit 202 is an acquisition unit that acquires the optimal chromatic dispersion compensation amount corresponding to the frequency band of each channel from the chromatic dispersion compensation amount calculation unit 130, phase conjugation processing information from the phase conjugation determination unit 140, and reception wavelength information and transmission wavelength information from the carrier frequency control unit 150. The node control unit 202 sets the frequency (wavelength) of the local light r1 for the reception light source 240 based on the acquired reception wavelength information, and sets the frequency of the transmission light r2 for the transmission light source 250 based on the acquired transmission wavelength information. The node control unit 202 sets the phase conjugation processing calculation for the phase conjugation processing unit 232 based on control information including an instruction to perform phase conjugation processing acquired from the control device 100. The node control unit 202 sets the chromatic dispersion compensation amount for the chromatic dispersion compensator 231 based on the acquired optimal chromatic dispersion compensation amount.

[0079] 13 shows an example of operation of an optical network system according to an embodiment of the present disclosure. As shown in FIG. 13, first, the network management unit 110 of the control device 100 determines transmission line information for the optical transmission lines before and after the optical repeater 200. The carrier frequency control unit 150 determines the wavelength to be used by the optical repeater 200 (S101). The network control unit 120 of the control device 100 determines the route of the path in the optical network 51 and identifies the optical transmission lines and the optical repeaters 200 on the path route. By determining the wavelength of each identified optical transmission line, the carrier frequency control unit 150 determines the wavelengths of the upstream and downstream stages (before and after conversion) of each optical repeater 200, i.e., the wavelengths of the optical signals transmitted and received by the optical repeater 200. The network control unit 120 and the carrier frequency control unit 150 output the reception wavelength information and transmission wavelength information of the optical repeater 200 to the chromatic dispersion compensation amount calculation unit 130, the phase conjugate determination unit 140, and the carrier frequency control unit 150 according to the determined wavelength, and also output the transmission path information (distance) of the optical transmission paths before and after the optical repeater 200 to the chromatic dispersion compensation amount calculation unit 130 and the phase conjugate determination unit 140. When a path includes multiple optical repeaters 200, the following process is performed for each optical repeater.

[0080] Next, the chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the chromatic dispersion characteristics in the upstream and downstream optical transmission paths (S102). The chromatic dispersion compensation amount calculation unit 130 calculates the chromatic dispersion characteristics in the upstream and downstream optical transmission paths of the optical repeater 200 based on the reception wavelength information and transmission wavelength information acquired from the network control unit 120 and the carrier frequency control unit 150 and the transmission path information (distance) of the upstream and downstream optical transmission paths of the optical repeater 200. Note that 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.

[0081] For example, the chromatic dispersion characteristic is the slope of the amount of chromatic dispersion accumulated with respect to the distance of the optical transmission path (distance-dependent chromatic dispersion characteristic). Since the slope of this chromatic dispersion amount varies depending on the wavelength, a table that associates the wavelength (or wavelength band) with the slope of the amount of chromatic dispersion may be stored in advance. The chromatic dispersion compensation amount calculation unit 130 may refer to this table to determine the chromatic dispersion characteristic corresponding to the wavelength.

[0082] Next, the chromatic dispersion compensation amount calculation unit 130 of the control device 100 determines an optimal chromatic dispersion compensation amount for the optical repeater 200 (S103). The chromatic dispersion compensation amount calculation unit 130 determines an optimal chromatic dispersion compensation amount for the optical repeater 200 based on the chromatic dispersion characteristics of the optical transmission paths upstream and downstream of the optical repeater 200 and transmission path information for the optical transmission paths upstream and downstream. The chromatic dispersion compensation amount calculation unit 130 calculates the amount of chromatic dispersion accumulated in the optical transmission path of the upstream stage (receiving side), calculates the amount of chromatic dispersion accumulated in the optical transmission path of the downstream stage (transmitting side), and determines an optimal chromatic dispersion amount based on the chromatic dispersion amounts of the upstream stage and the downstream stage. In particular, the chromatic dispersion compensation amount calculation unit 130 determines the optimal chromatic dispersion amount based on the amount of chromatic dispersion accumulated between the transmitting terminal device 30 and the optical repeater 200 and the amount of chromatic dispersion accumulated between the optical repeater 200 and the receiving terminal device 40. For example, the chromatic dispersion compensation amount calculation unit 130 determines the amount of chromatic dispersion accumulated in the optical transmission line upstream of the optical repeater 200 based on the chromatic dispersion characteristics and transmission line information (distance) of the optical transmission line upstream of the optical repeater 200, and determines the amount of chromatic dispersion accumulated in the optical transmission line downstream of the optical repeater 200 based on the chromatic dispersion characteristics and transmission line information of the optical transmission line downstream of the optical repeater 200. Note that in this example, the chromatic dispersion compensation amount calculation unit 130 determines the amount of chromatic dispersion compensation based on the chromatic dispersion characteristics and transmission line information, but since the chromatic dispersion characteristics correspond to the wavelength information, the chromatic dispersion compensation amount may also be determined based on the wavelength information and transmission line information. In other words, the chromatic dispersion compensation amount calculation unit 130 may determine the amount of chromatic dispersion compensation for multiple optical repeaters 200 constituting a path based on the wavelength information and transmission line information of the path.

[0083] Next, the phase conjugate determination unit 140 of the control device 100 determines the optimum phase conjugate processing in the optical repeater 200 (S104). The phase conjugate determination unit 140 determines the optimum phase conjugate processing in the optical repeater 200 based on the number of optical paths and the number of optical repeaters 200 between the transmitting terminal device 30 and the receiving terminal device 40 in the optical network 51.

[0084] Next, the control device 100 notifies the optical repeater 200 of the path information, receiving wavelength information, and transmitting wavelength information determined in S101, the optimal phase conjugate processing information determined in S104, and the optimal amount of chromatic dispersion compensation determined in S103 (S105).

[0085] Next, the node control unit 202 of the optical repeater 200 sets the wavelength of the wavelength information notified from the control device 100, the phase conjugate processing information, and the optimum amount of chromatic dispersion compensation (S106). The node control unit 202 sets the wavelength of the acquired reception wavelength information to the reception light source 240, sets the wavelength of the acquired transmission wavelength information to the transmission light source 250, sets the acquired phase conjugate processing information to the phase conjugate processing unit 232, and sets the acquired optimum amount of chromatic dispersion compensation to the chromatic dispersion compensation unit 231.

[0086] Next, the optical repeater 200 performs wavelength conversion, phase conjugation, and chromatic dispersion compensation (S107). The receiving light source 240 generates local light r1 of a set wavelength (frequency), and the transmitting light source 250 generates transmitting light r2 of a set wavelength, thereby performing wavelength conversion in the optical transceiver 201. Furthermore, the phase conjugation processing unit 232 performs phase conjugation processing by phase conjugation, and the chromatic dispersion compensation unit 231 performs chromatic dispersion compensation processing on the signal after phase conjugation processing based on a set compensation amount by digital signal processing.

[0087] 14A and 14B show specific examples of phase conjugation and chromatic dispersion compensation performed by a control method according to an embodiment of the present disclosure. In this embodiment, the optical repeater 200 performs phase conjugation to remove nonlinear distortion accumulated in a previous optical transmission path in an optical signal received by the optical repeater 200. This allows nonlinear distortion in the optical signal transmitted from the optical repeater 200 during transmission in a subsequent optical transmission path to be canceled at the receiving end. To achieve this effect, the optical repeater 200 in this embodiment determines an optimal amount of chromatic dispersion compensation that maximizes the nonlinear distortion cancellation effect. In this example, the optimal amount of chromatic dispersion compensation is calculated based on the amounts of chromatic dispersion in the previous and subsequent transmission paths for the optical repeater 200. In addition, in this example, the digital signal processing unit 230 of the optical repeater 200 determines an optimal amount of chromatic dispersion compensation when performing chromatic dispersion compensation after the phase conjugation. When the digital signal processor 230 performs phase conjugation processing after chromatic dispersion compensation processing, the optimum amount of chromatic dispersion compensation may be determined based on the amount of chromatic dispersion in the upstream and downstream transmission paths. In this example, the digital signal processor 230 first performs phase conjugation processing, and then performs chromatic dispersion compensation processing.

[0088] As shown in FIG. 14A, in this example, one optical repeater 200 is disposed 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 line 3a (first optical transmission line), and the optical repeater 200 and the receiving terminal device 40 are connected via an optical transmission line 3b (second optical transmission line). For example, the distance L1 of the optical transmission line 3a and the distance L2 of the optical transmission line 3b are different, and the distance L2 of the optical transmission line 3b is longer than the distance L1 of the optical transmission line 3a, but they may also be the same distance. An optical signal with a wavelength λ1 is transmitted through the optical transmission line 3a, and an optical signal with a wavelength λ2 is transmitted through the optical transmission line 3b. For example, the wavelengths λ1 and λ2 may both be in the C-band wavelength band, or may be different, such as the C-band wavelength band and the L-band wavelength band, or may both be in the L-band wavelength band. The optical repeater 200 converts the received optical signal of wavelength λ1 into an optical signal of wavelength λ2, and transmits the converted optical signal of wavelength λ2.

[0089] As shown in FIG. 14B, in the upstream optical transmission line 3a, the wavelength of the optical signal is λ1, so the chromatic dispersion compensation amount calculation unit 130 of the control device 100 determines the slope DS1 of the chromatic dispersion amount in the optical transmission line 3a according to the wavelength λ1. The slope DS1 of the chromatic dispersion amount in the optical transmission line 3a may be read from a storage means such as a database. The chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the accumulated chromatic dispersion amount M1 (=DS1 × Leff1) at the effective nonlinear distance Leff1 in the upstream optical transmission line 3a using the slope DS1 of the chromatic dispersion amount and the effective nonlinear distance Leff1 in the optical transmission line 3a. The nonlinear effect is an effect that depends on the optical signal intensity, and the optical intensity in the transmission line decreases according to an exponential function characterized by the propagation loss constant. Therefore, it is sufficient to consider the nonlinear effect only in the region where the optical intensity is high. The effective nonlinear distance Leff is defined as the distance in 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.

[0090]

number

[0091] Furthermore, since the wavelength of the optical signal in the downstream optical transmission line 3b is λ2, the chromatic dispersion compensation amount calculation unit 130 of the control device 100 determines the slope DS2 of the chromatic dispersion amount in the optical transmission line 3b in accordance with the wavelength λ2. The slope DS2 of the chromatic dispersion amount in the optical transmission line 3b may be read from a storage means such as a database. The chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the accumulated chromatic dispersion amount M2 at the effective nonlinear distance Leff2 in the downstream optical transmission line 3b as M2 = -M1, under the condition that the accumulated chromatic dispersion amount M2 has the opposite sign to the accumulated chromatic dispersion amount M1 at the effective nonlinear distance Leff1 in the upstream optical transmission line 3a. The chromatic dispersion compensation amount calculation unit 130 then determines the accumulated chromatic dispersion amount M3 in the transmission signal of the optical repeater. M3 can be calculated as M3 = M2 + DS2 × Leff2 = DS1 × Leff1 + DS2 × Leff2.

[0092] The chromatic dispersion compensation amount calculation unit 130 of the control device 100 then calculates the cumulative chromatic dispersion compensation amount M5 for the optical repeater 200 to compensate for chromatic dispersion using phase conjugation, using M5=M4×2.

[0093] The chromatic dispersion compensation amount calculation unit 130 of the control device 100 calculates the difference M6 between the accumulated chromatic dispersion amount M3 and the accumulated chromatic dispersion compensation amount M5, and transmits the difference M6 to the optical repeater 200 as an optimal chromatic dispersion compensation amount. The control device 100 also transmits control information including an instruction to perform phase conjugation to the optical repeater 200. As a result, the node control unit 202 of the optical repeater 200 instructs the phase conjugation processing unit 232 to perform phase conjugation calculation based on the control information including the instruction to perform the acquired phase conjugation, as described with reference to FIGS. 9 and 11. The phase conjugation processing unit 232 performs phase conjugation calculation. The node control unit 202 of the optical repeater 200 also sets the chromatic dispersion compensation amount M6 notified from the control device 100 in the chromatic dispersion compensation unit 231 of the digital signal processing unit 230, as described with reference to FIG. 9. 9, the node control unit 202 sets the transfer function coefficient of the inverse transfer function multiplier 413 in FIG. 11 in accordance with the chromatic dispersion compensation amount M6 notified from the control device 100. As a result, the optical repeater 200 calculates the accumulated chromatic dispersion M3 (M3=M4-M5-M6) for the downstream optical transmission line 3b after calculating the accumulated chromatic dispersion compensation amount M5 using the phase conjugation processing of the phase conjugation processing unit 232 and performing chromatic dispersion compensation using the chromatic dispersion compensation amount M6 of the chromatic dispersion compensator 231, and outputs an optical signal with this accumulated chromatic dispersion M3 (FIG. 14B). As a result, the nonlinear effect in the receiving terminal device 40 is suppressed.

[0094] The optical repeater 200 can calculate the accumulated chromatic dispersion M3 by the following equation without performing phase conjugation: M3 = M2 + DS2 × Leff2 = DS1 × Leff1 + DS2 × Leff2. Therefore, the chromatic dispersion compensator 231 of the optical repeater 200 may calculate the accumulated chromatic dispersion M3 and output an optical signal having the accumulated chromatic dispersion M3 without performing phase conjugation (FIG. 14B). In the explanations of FIGS. 12A and 12B, for convenience of explanation, an optical signal having a wavelength λ1 is transmitted through the optical transmission line 3a, and an optical signal having a wavelength λ2 is transmitted through the optical transmission line 3b. However, a multi-channel optical signal having multiple wavelengths λ (frequency bands) may be transmitted through the optical transmission line 3a, and a multi-channel optical signal having multiple wavelengths λ (frequency bands) may also be transmitted through the optical transmission line 3b.

[0095] FIG. 14C is a diagram showing an outline of the phase conjugate processing. As shown in FIG. 14C, in a certain span in the optical network 51 (between the transmitting terminal device 30 and a network device such as the optical repeater device 200 in FIG. 14C), nonlinear distortion of the transmitted signal occurs as signal degradation due to nonlinear effects (1111 in FIG. 14C). The optical repeater device 200 performs phase conjugation (inversion of the optical signal) (1112 in FIG. 14C). This provides an offsetting effect of nonlinear distortion using phase conjugation in the span subsequent to the optical repeater device 200 (between the optical repeater device 200 and the receiving terminal device 40), thereby reducing signal degradation (nonlinear distortion) in the receiving terminal device 40 (1113 in FIG. 14C). In addition, when the optical repeater device 200 receives a multi-channel signal, optimal chromatic dispersion compensation is performed for the signal bandwidth of each channel, thereby enhancing the offsetting effect of nonlinear distortion in the receiving terminal device 40.

[0096] The processing in the control device 100 described above is one aspect of processing in which the amount of chromatic dispersion compensation to be performed in the optical repeater 200 is determined based on wavelength information of optical signals transmitted and received by the optical repeater 200 constituting the optical network in the path of the optical network and transmission line information of the optical transmission line connected to the optical repeater 200, and the phase conjugation processing in the optical repeater 200 is determined based on the wavelength information and the transmission line information.

[0097] In addition, a part of the processing in the control device 100 is one form of processing to send to the optical repeater 200 an instruction to perform phase conjugate processing to calculate the complex conjugate of the optical signal based on the accumulated chromatic dispersion amount M4 of the optical signal received by the optical repeater 200.

[0098] In addition, a part of the processing in the control device 100 is one form of processing to calculate a first accumulated chromatic dispersion amount M1 in a first effective nonlinear distance (Leff1) based on a transmitting-side network device in a first optical transmission path (previous path) between the optical repeater 200 and a transmitting-side network device that transmits an optical signal received by the optical repeater 200, among the optical transmission paths connected to the optical repeater 200.

[0099] Furthermore, a part of the processing in the control device 100 is one aspect of processing to calculate a second accumulated chromatic dispersion amount (M2) of the optical signal in a second effective nonlinear distance (Leff2) based on the optical repeater device itself in a second optical transmission path (later path) between the optical repeater device 200 and a network device on the receiving side of the optical signal transmitted by the optical repeater device 200, among the optical transmission paths connected to the optical repeater device 200, and which has the opposite sign to the first accumulated chromatic dispersion amount (multiplied by minus 1).

[0100] Furthermore, a part of the processing in the control device 100 is one aspect of processing to calculate a chromatic dispersion compensation amount (M6) indicating the difference between the chromatic dispersion amount (M3) of the optical signal at the time of transmission in the optical repeater 200 when the accumulated chromatic dispersion amount of the optical signal becomes the second accumulated chromatic dispersion amount (M2) at the second effective nonlinear distance (Leff2) based on a statistical value (DS2) of the transition of the accumulated chromatic dispersion amount of the optical signal according to the distance in the second optical transmission path, and the chromatic dispersion amount (M5) which is the result of complex conjugation.

[0101] The processing of the optical repeater 200 described above is one aspect of processing in which chromatic dispersion compensation processing is performed on an electrical signal based on a received optical signal based on the chromatic dispersion compensation amount (M6), and phase conjugation processing is performed on an electrical signal based on a received optical signal based on phase conjugation processing information acquired from the control device 100.

[0102] Furthermore, some of the processing in the optical repeater 200 described above is one aspect of processing for performing phase conjugate processing based on the amount of accumulated chromatic dispersion of the optical signal received by the optical repeater 200 itself and an instruction to perform phase conjugate processing for calculating the complex conjugate of the optical signal.

[0103] Furthermore, a part of the processing in the optical repeater 200 described above is one aspect of processing to determine the chromatic dispersion amount (M3) of the optical signal to be transmitted to the receiving network device based on the chromatic dispersion amount (M5) that is the result of the complex conjugation after the phase conjugation processing and the chromatic dispersion compensation amount (M6) acquired from the control device 100.

[0104] Here, the digital signal processing of the optical repeater 200 described above allows for phase conjugation and chromatic dispersion compensation on a channel-by-channel basis when receiving an optical signal consisting of one or more optical channels. However, if the polarization rotation angle of the light is not uniform on a channel-by-channel basis, the optical reception characteristics of other optical repeaters 200 and receiving terminal devices 40 on the receiving side at the downstream stage may deteriorate. The reception characteristics are expressed by a Q-factor (Quality Factor). The Q-factor can be measured on the receiving side using known techniques.

[0105] FIG. 15 is a diagram illustrating another example configuration of each device in the optical network system according to an embodiment of the present disclosure. The digital signal processing unit 230 of the optical repeater 200 may further include the functions of a polarization monitor unit 234 and a polarization rotation calculation unit 235 as shown in FIG. 15 in addition to the chromatic dispersion compensator 230 and the phase conjugate processor 232. Note that the digital signal processing unit 230 may also include the function of a delay adjuster 233 as shown in FIG. 10. Note that the digital signal processing unit 230 of the optical repeater 200 may at least perform the functions of the polarization monitor unit 234 and the polarization rotation calculation unit 235. Note that in the present disclosure, the optical repeater 200 includes digital signal processing units 230 in numbers corresponding to the number of channels included in the optical signal, and each digital signal processing unit 230 performs signal processing for the corresponding channel. The optical repeater 200 further includes a polarization management unit 236.

[0106] The optical repeater 200 is communicatively connected to a pre-stage device 31, a post-stage device 41, and the control device 100. The pre-stage device 31 may be another optical repeater 200 or a transmitting terminal device 30 located in a stage preceding the optical repeater 200 in the optical network. The post-stage device 41 may be another optical repeater 200 or a receiving terminal device 40 located in a stage following the optical repeater 200 in the optical network.

[0107] The digital signal processing unit 230 of the optical repeater 200 may use the functions of the polarization monitor 234 and the polarization rotation calculation unit 235 to perform processing to mitigate deterioration of the optical reception characteristics in other optical repeaters 200 and the receiving terminal device 40 on the receiving side at the downstream stage, even when there is a mismatch in the polarization rotation angle of the light on a channel-by-channel basis. This processing will be explained below. Note that mismatch in the polarization rotation degree between channels may occur when an optical signal consisting of one or more optical channels is separated into each channel, or may occur because the optical characteristics of the conductor parts of each optical channel after separation differ between the channels.

[0108] FIG. 16 is a diagram showing changes in the reception characteristics of one signal channel depending on the difference in polarization rotation angle that occurs in repeater device 200 for two signal channels included in an optical signal. As shown in FIG. 16, as an example, when a difference occurs in the polarization rotation angle of two signal channels included in an optical signal, the Q factor of each channel increases or decreases. For example, in FIG. 16, when the difference in the polarization rotation angle of the two signal channels is 0, π, or 2π, the Q factor of each channel is high. On the other hand, in FIG. 16, when the difference in the polarization rotation angle of the two signal channels is 1 / 2π or 3 / 2π, the Q factor of each channel is relatively low. When the difference in the polarization rotation angle of the two signal channels is 1 / 2π or 3 / 2π, the two signal channels are orthogonal to each other. In the nonlinear distortion compensation by phase conjugation of the optical repeater 200 as in the disclosed examples of the optical repeater 200 described above, it is possible to expect a compensation effect for the polarization interaction component in the inter-channel nonlinear distortion, but if orthogonal polarization rotation occurs between two signal channels in the optical repeater 200, the compensation effect for the polarization interaction component in the inter-channel nonlinear distortion is reduced, and therefore the Q value decreases when a deviation of 1 / 2π or 3 / 2π occurs in the polarization rotation angles of the two signal channels as shown in Fig. 16. Note that the change in the Q value based on the difference (deviation) in the polarization rotation angles of the two signal channels is not limited to the mode shown in Fig. 16.

[0109] Here, the polarization monitor 234 monitors the rotation angles from a reference angle of the polarization indicated by the multiple signal channels included in the optical signal. The polarization rotation calculation unit 235 adjusts the rotation angle of the polarization of each signal channel from the reference angle to a rotation angle that improves the reception characteristics of each signal channel, using a control value that controls the rotation angle of the polarization of any one of the multiple signal channels from the reference angle. The polarization management unit 234 controls the polarization monitor unit 234 and the polarization rotation calculation unit 235 of each digital signal processing unit 230 .

[0110] FIG. 17 is a diagram showing the monitor characteristics of the polarization monitor unit. As shown in Fig. 17, the polarization monitor unit 234 detects the rotation angle of one signal channel, which is responsible for processing, from a reference angle of polarization of the multiple signal channels included in the optical signal. At this time, as shown in Fig. 17, the polarization monitor unit 234 outputs a detected rotation angle (Estimated degrees) whose value differs depending on the rotation angle (Actual degrees) from the reference angle of the actual polarization. Specifically, when the actual rotation angle of the polarization from the reference angle is 0°, 15°, or 30°, the detected rotation angle can be output as 0°, 15°, or 30°, respectively. However, when the actual rotation angle of the polarization from the reference angle is 45°, 60°, 75°, or 90°, the detected rotation angle can be output as -45°, -30°, -15°, or 0°, respectively. Although not shown in FIG. 17 , the polarization monitor unit 234 is capable of outputting the detected rotation angle φ as the same value as the actual rotation angle (Actual deg) of the polarization from the reference angle when the actual rotation angle (Actual deg) of the polarization from the reference angle is 0°≦Actual deg<45°. Thus, the polarization monitor unit 234 has the characteristic of outputting the same value as the detected rotation angle when the actual rotation angle of the polarization from the reference angle is within the range of 0°≦Actual deg<45°, and outputting a value obtained by subtracting 90° from that value as the detected rotation angle when the actual rotation angle of the polarization from the reference angle is 45°≦Actual deg<90°. In other words, the output value (detected rotation angle φ) of the polarization monitor unit 234 takes a value in the range of −45°≦detected rotation angle φ<+45°. Furthermore, a similar output mode of the polarization monitor unit 234 is repeated every time the rotation angle (Actual deg) of the actual polarization from the reference angle increases by π / 2. Note that this characteristic is an example of polarization monitoring using an adaptive equalization algorithm that uses an FIR filter with a 2x2 butterfly structure for a QPSK signal, and is a characteristic of a known polarization monitor function. The monitoring characteristic of the polarization rotation angle of the polarization monitor unit 234 is not limited to that shown in Fig. 17, but similarly has a characteristic in which the output monitor value is limited to a range of 90°. Note that the polarization monitor unit 234 may also be able to directly detect the rotation angle of the actual polarization reference angle and output it as the detected rotation angle.

[0111] FIG. 18 is a diagram showing an outline of the process of matching the rotation angles of the signal channels in the digital signal processing unit. For example, suppose the optical signal includes three signal channels: a first signal channel (CH1), a second signal channel (CH2), and a third signal channel (CH3). In this case, the polarization rotation calculation unit 235 acquires a control value generated by the control device 100 based on the detected rotation angles of the first signal channel (CH1) and the second signal channel (CH2) that the polarization management unit 236 acquires from the polarization monitor unit 234 corresponding to the signal channels and transmits to the control device 100. This control value may be a signal channel identifier and a compensation rotation angle that are stored by the control device 100 when the control device 100 acquires the reception characteristics of the first signal channel (CH1) and the second signal channel (CH2) in the subsequent device 41 from the subsequent device 41 and that are used to obtain the best reception characteristic among the reception characteristics. The polarization rotation calculation unit 235 adjusts the rotation angle of the polarization of the first signal channel (CH1) and the second signal channel (CH2) from the reference angle using the signal channel identifier and compensation rotation angle indicated by the acquired control value (step 181). At this time, the polarization rotation calculation unit 235 adjusts one of the rotation angle of the polarization of the first signal channel (CH1) from the reference angle and the rotation angle of the polarization of the second signal channel (CH2) from the reference angle to the other, based on the control value, which is the rotation angle that provides good reception characteristics in the receiving device. Specifically, if the control value includes an identifier of the first signal channel (CH1), the polarization rotation calculation unit 235 adjusts the rotation angle of the polarization of the second signal channel (CH2) from the reference angle to the rotation angle of the polarization of the first signal channel (CH1). Alternatively, if the control value includes an identifier of the second signal channel (CH2), the polarization rotation calculation unit 235 adjusts the rotation angle of the polarization of the first signal channel (CH1) from the reference angle to the rotation angle of the polarization of the second signal channel (CH2) from the reference angle. For convenience, the rotation angle obtained after the rotation angles of the two signal channels have been matched will be referred to as a first combined rotation angle.

[0112] Furthermore, the polarization rotation calculation unit 235 acquires a control value generated by the control device 100 based on the detected rotation angle of the third signal channel (CH3) acquired by the polarization management unit 236 from the polarization monitor unit 234 corresponding to the signal channel and transmitted to the control device 100. This control value may be a result of the control device 100 acquiring from the subsequent device 41 the reception characteristics of the first signal channel (CH1), the second signal channel (CH2), and the third signal channel (CH3) in the subsequent device 41, and an identifier and a compensation rotation angle of the signal channel that has the best value among these reception characteristics stored by the control device 100. The polarization rotation calculation unit 235 uses the identifier and compensation rotation angle of the signal channel indicated by the acquired control value to match the first integrated rotation angle with the rotation angle from the reference angle of the polarization of the third signal channel (CH3) (step 182). At this time, the polarization rotation calculation unit 235 adjusts one of the first integrated rotation angle and the rotation angle from the reference angle of polarization of the third signal channel (CH3) to the other, based on the control value, among the rotation angle from the reference angle of polarization of the first signal channel (CH1), the rotation angle from the reference angle of polarization of the second signal channel (CH2), and the rotation angle from the reference angle of polarization of the third signal channel (CH3). This adjustment results in good reception characteristics in the subsequent device 41. Specifically, when the control value includes the identifier of the first signal channel (CH1) or the second signal channel (CH2), the polarization rotation calculation unit 235 adjusts the rotation angle from the reference angle of polarization of the third signal channel (CH3) to the first integrated rotation angle. Alternatively, if the control value includes an identifier of the third signal channel (CH3), the polarization rotation calculation unit 235 adjusts the rotation angle (first integrated rotation angle) of the polarization of the first signal channel (CH1) and the second signal channel (CH2) from the reference angle to the rotation angle of the polarization of the third signal channel (CH3) from the reference angle. The above processing allows the rotation angles of the polarization of the first signal channel (CH1), the second signal channel (CH2), and the third signal channel (CH3) from the reference angle to be adjusted. Note that even when the optical signal includes four or more signal channels, the polarization rotation calculation unit 235 similarly controls the rotation angles of the polarization of all signal channels from the reference angle to be the same, sequentially adjusting them to the rotation angle of the polarization with the best reception characteristics from the reference angle.

[0113] FIG. 19 is a diagram showing a processing flow of the optical network system. In the optical repeater 200, the polarization monitor 234 of each digital signal processor 230 responsible for processing each signal channel detects the rotation angle (detected rotation angle) of the polarization of the acquired signal channel from a reference angle. Each polarization monitor 234 outputs the detected rotation angle of the signal channel to be processed to the polarization management unit 236. The polarization management unit 236 outputs the detected rotation angle of each signal channel to the control device 100 (step S901).

[0114] Assume now that the optical signal includes three channels: a first signal channel (CH1), a second signal channel (CH2), and a third signal channel (CH3). In this case, the polarization management unit 236 calculates the detected rotation angle φ1 from the reference angle of the polarization of the first signal channel (CH1) using the polarization monitor unit 234.

[0115] Similarly, for the second signal channel (CH2) indicating the frequency band adjacent to the first signal channel (CH1), the polarization management unit 236 calculates the detected rotation angle φ2 from the reference angle of the polarization of the second signal channel (CH2).

[0116] The polarization management unit 236 calculates candidate compensation rotation angles Δ such that the difference between the actual rotation angle of the first signal channel (CH1) and the rotation angle of the second signal channel (CH2) is 0° or 180° (π), that is, candidate compensation rotation angles Δ1 and Δ2 such that the difference between the rotation angle of the first signal channel (CH1) and the rotation angle of the second signal channel (CH2) is 0° or 180° (π) so as to improve the reception characteristics as shown in FIG. 16.

[0117] Of the two compensation rotation angle candidates Δ1 and Δ2 calculated below, when one candidate is applied to the second signal channel (CH2) relative to the signal characteristics (reception characteristics) before compensation, the signal characteristics deteriorate, but when the other candidate, which is shifted 90° from that compensation rotation angle candidate, is applied to the second signal channel (CH2), the signal characteristics improve. The compensation rotation angle that improves the latter signal characteristics is the optimal compensation rotation angle. However, if the difference in the actual rotation angles of the first signal channel CH1 and the second signal channel CH2 is already 0° or 180° before compensation, when one of the two compensation rotation angle candidates Δ1 and Δ2 is applied to the second signal channel (CH2), the signal characteristics deteriorate, but when the other candidate is applied to the second signal channel (CH2), the signal characteristics remain unchanged from before compensation, and the latter is the optimal compensation rotation angle.

[0118] That is, the polarization management unit 236 calculates a candidate compensation rotation angle Δ that improves the reception characteristics in the subsequent device 41, based on the rotation angle from the reference angle of polarization of a first signal channel among the multiple signal channels and the rotation angle from the reference angle of polarization of a second signal channel among the multiple signal channels (step S902). In this process, it is sufficient to set the difference in polarization angle between the first signal channel (CH1) and the second signal channel (CH2) to 0° or 180° (π), so there is no need to estimate the actual angles of the first signal channel (CH1) and the second signal channel (CH2), and the optimal compensation angle can be estimated with fewer calculations.

[0119] Therefore, the polarization management unit 236 calculates the compensation rotation angle candidates Δ1 and Δ2 using the following equations. Δ1=φ1-φ2 Δ2=φ1-φ2+90°

[0120] Below, we will show an example where the actual rotation angle of the polarization of the first signal channel (CH1) with respect to the reference angle is 30°, and the actual rotation angle of the polarization of the second signal channel (CH2) with respect to the reference angle is 150°. In this case, from Figure 17, the monitored values ​​(detected rotation angles) are φ1 = 30° and φ2 = -30°, respectively. From the above calculation formula, the candidate compensation rotation angles Δ are Δ1 = 60° and Δ2 = φ1 - φ2 + 90° = 150°, respectively.

[0121] (Case 1) A compensation rotation angle Δ1 for the second signal channel (CH2) is calculated. That is, by changing the actual rotation angle of the second signal channel (CH2) from the reference angle of polarization by Δ1 (increasing Δ1), the difference in rotation angle of the first signal channel (CH1) and the second signal channel (CH2) from the reference angle of polarization becomes 180° (π), and the value of the reception characteristic (Q value) is improved in the subsequent device 41 as shown in FIG.

[0122] (Case 2) A compensation rotation angle Δ2 for the second signal channel (CH2) is calculated. That is, by changing the actual rotation angle of the second signal channel (CH2) from the reference angle of polarization by Δ2 (increasing Δ2), the difference in rotation angle from the reference angle of polarization of the first signal channel (CH1) and the second signal channel (CH2) becomes 270° (π3 / 2), and the value of the reception characteristic (Q value) in the subsequent device 41 deteriorates as shown in FIG. 16.

[0123] The optimum compensation rotation angle is determined by comparing the reception characteristic Q values ​​of Case 1 and Case 2. In this example, Δ1 of Case 1 is the optimum compensation rotation angle.

[0124] (Processing assuming case 1) Assuming the above-described case 1, the polarization management unit 236 outputs an execution request to the polarization rotation calculation unit 235, including the identifier of the first signal channel (CH1), the identifier of the second signal channel (CH2), the identifier of the second signal channel whose polarization is to be rotated, and the compensation rotation angle Δ1. Based on the identifier of the second signal channel (CH2) whose polarization is to be rotated, included in the execution request, the polarization rotation calculation unit 235 adds the compensation rotation angle Δ1 to the polarization rotation angle of the second signal channel (CH2). The polarization rotation calculation unit 235 outputs a measurement request for the reception characteristic value (Q factor) of the subsequent stage device 41 to the polarization management unit 236. The polarization management unit 236 outputs a measurement request for the reception characteristic value (Q factor) including the identifier of the first signal channel (CH1) and the identifier of the second signal channel (CH2) to the control device 100. The subsequent stage device 41 outputs the reception characteristics of each channel to the control device 100. Therefore, the network control unit 120 of the control device 100 receives the reception characteristics (Q values) of the first signal channel (CH1) and the second signal channel (CH2). The network control unit 120 of the control device 100 associates the first reception characteristics (Q values) of the first signal channel (CH1) and the second signal channel (CH2) with the case number of case 1 (a number indicating processing assuming case 1) and the compensation rotation angle +Δ1 in a situation where the compensation rotation angle Δ1 is added to the rotation angle of the polarization of the second signal channel (CH2), and temporarily stores them.

[0125] (Processing assuming case 2) Assuming the above-mentioned Case 2, the polarization management unit 236 outputs an execution request to the polarization rotation calculation unit 235, including the identifier of the first signal channel (CH1), the identifier of the second signal channel (CH2), the identifier of the second signal channel whose polarization is to be rotated, and the compensation rotation angle Δ2. The polarization rotation calculation unit 235 adds the compensation rotation angle Δ2 to the polarization rotation angle of the second signal channel (CH2) based on the identifier of the second signal channel (CH2) whose polarization is to be rotated, included in the execution request. The polarization rotation calculation unit 235 outputs a measurement request for the reception characteristic value (Q factor) of the subsequent stage device 41 to the polarization management unit 236. The polarization management unit 236 outputs a measurement request for the reception characteristic value (Q factor) including the identifier of the first signal channel (CH1) and the identifier of the second signal channel (CH2) to the control device 100. The subsequent stage device 41 outputs the reception characteristics of each channel to the control device 100. Therefore, the network control unit 120 of the control device 100 receives the reception characteristics (Q values) of the first signal channel (CH1) and the second signal channel (CH2). The network control unit 120 of the control device 100 associates and temporarily stores the third reception characteristics (Q values) of the first signal channel (CH1) and the second signal channel (CH2), the case number of case 2 (a number indicating processing assuming case 2), and the compensation rotation angle +Δ2 in a situation where the compensation rotation angle Δ2 is added to the rotation angle of the polarization of the second signal channel (CH2).

[0126] That is, in the processing assuming case 1 and the processing assuming case 2, the network control unit 120 of the control device 100 calculates candidates for control values ​​including a compensation rotation angle Δ indicating the rotation angle from the reference angle of the polarization of each signal channel when the difference in rotation angle improves the reception characteristics in the subsequent device 41 (step S903). For example, in the processing assuming case 1, the compensation rotation angle of the first signal channel is 0, and the compensation rotation angle of the second signal channel is +Δ1. In the processing assuming case 2, the compensation rotation angle of the first signal channel is 0, and the compensation rotation angle of the second signal channel is +Δ2.

[0127] The polarization management unit 236 detects the completion of transmission of the measurement request for all cases, Case 1 and Case 2, which are assumed cases for determining whether the reception characteristics will improve by changing the compensation rotation angle of the polarization of the second signal channel (CH2) without changing the polarization of the first signal channel (CH1). The polarization management unit 236 outputs the completion of transmission of the measurement request to the control device 100.

[0128] The network control unit 120 of the control device 100 identifies the case number with the highest Q value among the Q values ​​indicated by the stored first and second reception characteristics. That is, in this process, the network control unit 120 of the control device 100 identifies a control value including a compensation rotation angle Δ indicating the rotation angle of the polarization of the signal channel from the reference angle when the Q value indicated by the reception characteristics is the highest Q value (step S904).

[0129] The control device 100 transmits a control value including the identified case number and the compensation rotation angle for that case number to the optical repeater 200 (step S905). The polarization management unit 236 of the optical repeater 200 acquires the control value and outputs the control value to the polarization rotation calculation unit 235. The processing of this polarization management unit 236 is processing of acquiring from the control device 100 a control value including the rotation angle from the reference angle of the polarization of each signal channel calculated by the control device 100 based on the reception characteristics of each of the multiple signal channels received from the subsequent device 41, the rotation angle being the difference in the rotation angle that improves the reception characteristics in the subsequent device 41. The polarization rotation calculation unit 235 of the optical repeater 200 uses the case number and the compensation rotation angle for that case number to match the rotation angle from the reference angle of the polarization of the first signal channel (CH1) and the second signal channel (CH2) (step S906). For example, suppose the control value includes the case number of case 1 (a number indicating processing assuming case 1) and a compensation rotation angle Δ1. In this case, the polarization rotation calculation unit 235 adds the compensation rotation angle Δ1 to the rotation angle of the polarization of the second signal channel (CH2) to control and fix the difference between the rotation angle of the polarization of the first signal channel (CH1) from the reference angle and the rotation angle of the polarization of the second signal channel (CH2) from the reference angle to 0° or 180°. Note that a known technique may be used for the processing of adding a change in the compensation rotation angle to the rotation angle of the polarization.

[0130] In the above-described processing, the polarization management unit 236 fixes the rotation angle of the polarization of the first signal channel (CH1) from the reference angle, and performs control to vary the rotation angle of the polarization of the second signal channel (CH2) from the reference angle by a compensation rotation angle. However, the polarization management unit 236 may fix the rotation angle of the polarization of the second signal channel (CH2) from the reference angle, and perform control to vary the rotation angle of the polarization of the first signal channel (CH1) from the reference angle by a compensation rotation angle, and may similarly instruct the control device 100 to measure the reception characteristics (Q value) for each similar case, and perform processing for the best case of those reception characteristics.

[0131] The polarization management unit 236 specifies the rotation angle of the polarization of the first signal channel (CH1) or the second signal channel (CH2) from the reference angle. This value is fixed by the process of matching the rotation angles of the polarization of the first signal channel (CH1) and the second signal channel (CH2) from the reference angle.

[0132] The polarization management unit 236 determines whether there are any unprocessed signal channels among the signal channels included in the optical signal (step S907). If there are any unprocessed signal channels among the signal channels included in the optical signal, the polarization management unit 236 repeats the above-described processing from step S901.

[0133] Assume now that the optical signal includes three channels: a first signal channel (CH1), a second signal channel (CH2), and a third signal channel (CH3). In this case, the polarization management unit 236 calculates the rotation angle φ1 of the polarization of the first signal channel (CH1) from the reference angle by using the polarization monitor unit 234.

[0134] Similarly, for the third signal channel (CH3) indicating the frequency band adjacent to the second signal channel (CH2), the polarization management unit 236 calculates a detected rotation angle φ3 from the reference angle of polarization of the third signal channel (CH3). Therefore, the polarization management unit 236 calculates candidate compensation rotation angles Δ (Δ3 and Δ4 below) such that the difference between the actual rotation angle of the first signal channel (CH1) and the rotation angle of the third signal channel (CH3) is 0° or 180° (π).

[0135] That is, based on the rotation angle from the reference angle of polarization of a first signal channel among the multiple signal channels and the rotation angle from the reference angle of polarization of a third signal channel among the multiple signal channels, the polarization management unit 236 calculates a candidate compensation rotation angle Δ that indicates the rotation angle from the reference angle of polarization of each signal channel when the difference in rotation angles improves the reception characteristics in the subsequent device 41.

[0136] Therefore, the polarization management unit 236 calculates the compensation rotation angle candidates Δ3 and Δ4 using the following equations. Δ3=φ1-φ3 Δ4=φ1-φ3+90°

[0137] (Case 3) A compensation rotation angle Δ3 is calculated for the third signal channel (CH3). That is, a change of Δ3 is added to the actual rotation angle of the polarization of the third signal channel (CH3) from the reference angle (an increase of Δ3).

[0138] (Case 4) A compensation rotation angle Δ4 is ​​calculated for the third signal channel (CH3), i.e., a change of Δ4 is ​​added to the actual rotation angle from the reference angle of the polarization of the third signal channel (CH3) (an increase of Δ4).

[0139] The network control unit 120 of the control device 100 compares the reception characteristic Q values ​​of Case 3 and Case 4 to determine the optimum compensation rotation angle in the same manner as in step S902 described above.

[0140] (Processing assuming case 3) Assuming the above-mentioned Case 3, the polarization management unit 236 outputs an execution request to the polarization rotation calculation unit 235, including the identifier of the first signal channel (CH1), the identifier of the third signal channel (CH3), the identifier of the third signal channel whose polarization is to be rotated, and the compensation rotation angle Δ3. The polarization rotation calculation unit 235 adds the compensation rotation angle Δ3 to the polarization rotation angle of the third signal channel (CH3) based on the identifier of the third signal channel (CH3) whose polarization is to be rotated, included in the execution request. The polarization rotation calculation unit 235 outputs a measurement request for the reception characteristic value (Q factor) of the subsequent stage device 41 to the polarization management unit 236. The polarization management unit 236 outputs a measurement request for the reception characteristic value (Q factor) including the identifier of the first signal channel (CH1) and the identifier of the third signal channel (CH3) to the control device 100. The subsequent stage device 41 outputs the reception characteristics of each channel to the control device 100. Therefore, the network control unit 120 of the control device 100 receives the reception characteristics (Q values) of the first signal channel (CH1) and the third signal channel (CH3). The network control unit 120 of the control device 100 associates the third reception characteristics (Q values) of the first signal channel (CH1) and the third signal channel (CH3) with the case number of Case 3 (a number indicating processing assuming Case 3) and the compensation rotation angle + Δ3 in a situation where the compensation rotation angle Δ3 is added to the rotation angle of the polarization of the third signal channel (CH3), and temporarily stores them.

[0141] (Processing assuming case 4) Assuming the above-mentioned Case 4, the polarization management unit 236 outputs an execution request to the polarization rotation calculation unit 235, including the identifier of the first signal channel (CH1), the identifier of the third signal channel (CH3), the identifier of the third signal channel whose polarization is to be rotated, and the compensation rotation angle Δ4. The polarization rotation calculation unit 235 adds the compensation rotation angle Δ4 to the polarization rotation angle of the third signal channel (CH3) based on the identifier of the third signal channel (CH3) whose polarization is to be rotated, included in the execution request. The polarization rotation calculation unit 235 outputs a measurement request for the reception characteristic value (Q factor) of the subsequent stage device 41 to the polarization management unit 236. The polarization management unit 236 outputs a measurement request for the reception characteristic value (Q factor) including the identifier of the first signal channel (CH1) and the identifier of the third signal channel (CH3) to the control device 100. The subsequent stage device 41 outputs the reception characteristics of each channel to the control device 100. Therefore, the network control unit 120 of the control device 100 receives the reception characteristics (Q values) of the first signal channel (CH1) and the third signal channel (CH3). The network control unit 120 of the control device 100 temporarily stores, in association with each other, the fourth reception characteristics (Q values) of the first signal channel (CH1) and the third signal channel (CH3), the case number of case 4 (a number indicating processing assuming case 4), and the compensation rotation angle + Δ4 in a situation where the compensation rotation angle Δ4 is ​​added to the rotation angle of the polarization of the third signal channel (CH3).

[0142] That is, in the processing assuming Case 3 and the processing assuming Case 4, the network control unit 120 of the control device 100 calculates candidates for the control value including the compensation rotation angle Δ indicating the rotation angle from the reference angle of the polarization of each signal channel when the difference in rotation angle improves the reception characteristics in the subsequent device 41 (step S903). For example, in the processing assuming Case 3, the compensation rotation angle of the first signal channel is 0, and the compensation rotation angle of the third signal channel is +Δ3. In the processing assuming Case 4, the compensation rotation angle of the first signal channel is 0, and the compensation rotation angle of the third signal channel is +Δ4.

[0143] The polarization management unit 236 detects the completion of transmission of the measurement request for all cases 3 and 4, which are assumed cases for determining whether the reception characteristics can be improved by changing the compensation rotation angle of the polarization of the third signal channel (CH3) without changing the polarization of the first signal channel (CH1) and the second signal channel (CH2). The polarization management unit 236 outputs the completion of transmission of the measurement request to the control device 100.

[0144] The network control unit 120 of the control device 100 identifies the case number with the highest Q value among the Q values ​​indicated by the stored third and fourth reception characteristics. That is, in this process, the network control unit 120 of the control device 100 identifies a control value including a compensation rotation angle Δ indicating the rotation angle of the polarization of the signal channel from the reference angle when the Q value indicated by the reception characteristics is the highest Q value (step S904).

[0145] The control device 100 transmits a control value including the identified case number and the compensation rotation angle for that case number to the optical repeater 200 (step S905). The polarization rotation calculation unit 235 of the optical repeater 200 uses the case number and the compensation rotation angle for that case number to match the rotation angles of the polarization of the first signal channel (CH1), the second signal channel (CH2), and the third signal channel (CH3) from the reference angle (step S906). Because the rotation angles of the polarization of the first signal channel (CH1) and the second signal channel (CH2) from the reference angle are already matched, the rotation angle of the polarization of the third signal channel (CH3) from the reference angle can be matched to these rotation angles. For example, suppose the control value includes the case number of case 3 (a number indicating processing assuming case 3) and the compensation rotation angle Δ3. In this case, the polarization rotation calculation unit 235 adds the compensation rotation angle Δ3 to the rotation angle of the polarization of the third signal channel (CH3) to control and fix the difference between the rotation angle of the polarization of the first signal channel (CH1) from the reference angle (or the rotation angle of the polarization of the second signal channel (CH2) from the reference angle) and the rotation angle of the polarization of the third signal channel (CH3) from the reference angle to 0° or 180°. A known technique may be used for the process of adding a change in the compensation rotation angle to the rotation angle of the polarization.

[0146] The polarization management unit 236 determines whether there are any unprocessed signal channels among the signal channels included in the optical signal (step S907). If there are no unprocessed signal channels among the signal channels included in the optical signal, the polarization management unit 236 ends the process.

[0147] In the above-described processing, the polarization management unit 236 fixes the rotation angle of the polarization of the first signal channel (CH1) from the reference angle, and performs control to vary the rotation angle of the polarization of the third signal channel (CH3) from the reference angle by a compensation rotation angle. However, the polarization management unit 236 may fix the rotation angle of the polarization of the third signal channel (CH3) from the reference angle, and perform control to vary the rotation angles of the polarization of the first signal channel (CH1) and the second signal channel (CH2) from the reference angles by a compensation rotation angle, and may instruct the control device 100 to measure the reception characteristics (Q value) for each similar case, and perform processing for the best case of those reception characteristics.

[0148] By the above processing, when the optical signal includes a first signal channel (CH1), a second signal channel (CH2), and a third signal channel (CH3), the difference in the rotation angle of the polarization of each signal channel from the reference angle becomes 0° or 180°, improving the reception characteristics in the subsequent device 41. When the optical signal includes four or more signal channels, the optical repeater device 200, subsequent device 41, and control device 100 work together to achieve the same effect by making the difference in the rotation angle of the polarization of each signal channel from the reference angle 0° or 180°.

[0149] The processing of the optical repeater device 200 described above is an example of processing in which, based on the rotation angle of the polarization of a first signal channel among the multiple signal channels from a reference angle and the rotation angle of the polarization of a second signal channel among the multiple signal channels from a reference angle, a control value including the rotation angle of each signal channel from a reference angle of polarization when the difference in rotation angle results in improved reception characteristics in the subsequent device 41 is obtained, and the rotation angle of the polarization of the first signal channel from a reference angle and the rotation angle of the polarization of the second signal channel from a reference angle are matched based on the rotation angles of each signal channel.

[0150] Furthermore, the processing of the optical repeater 200 described above is an example of a process of sequentially acquiring control values ​​for each change in the combination of a first signal channel selected from a plurality of signal channels and a second signal channel selected from a plurality of signal channels, and repeating the process of matching the rotation angle of one of the first signal channel or the second signal channel from a reference angle of polarization to the rotation angle of the other polarization from a reference angle based on each of the control values, thereby matching the rotation angles of all of the plurality of signal channels from a reference angle of polarization.

[0151] FIG. 20 is a functional block diagram of another example of an optical repeater. FIG. 21 is a diagram showing a processing flow of another example of an optical repeater. The optical repeater 200 may include a polarization monitor 234 (monitoring means) and a polarization rotation calculator 235 (calculating means). The polarization monitor 234 monitors the rotation angles from a reference angle of the polarization indicated by the multiple signal channels included in the optical signal (step S2001). The polarization rotation calculation unit 235 adjusts the rotation angle of each signal channel from the reference angle of polarization to a rotation angle that improves the reception characteristics of each signal channel using a control value that controls the rotation angle of the polarization of any one of the multiple signal channels from the reference angle (step S2002).

[0152] The control device, optical repeater, transmitting terminal device, and receiving terminal device in the above-described embodiments are configured by hardware or software, or both, and may be configured by one piece of hardware or software, or may be configured by multiple pieces of hardware or software. Each device (control device, etc.) and each function (processing) may be realized by a computer 60 having a processor 61 such as a CPU (Central Processing Unit) and a memory 62 serving as a storage device, as shown in Fig. 22. 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 having the processor 61 execute the program stored in the memory 62.

[0153] These programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray® disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0154] The control device 100, optical repeater device 200, transmitting terminal device 30, and receiving terminal device 40 of this disclosure have been described above, but this disclosure is not limited to the above-mentioned embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of this disclosure within the scope of this disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0155] Note that part or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.

[0156] (Appendix 1) a monitor means for monitoring a rotation angle of a polarization indicated by a plurality of signal channels included in the optical signal from a reference angle; a calculation means for adjusting a rotation angle of each signal channel from a reference angle of polarization to a rotation angle that improves reception characteristics of the signal channel by using a control value that controls a rotation angle of the polarization of any one of the plurality of signal channels from a reference angle of polarization; An optical repeater device comprising:

[0157] (Appendix 2) The calculation means acquires the control value including the rotation angle from the reference angle of polarization of each signal channel when the difference in rotation angle results in improved reception characteristics in a subsequent device, based on the rotation angle from the reference angle of polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of polarization of a second signal channel among the plurality of signal channels, and aligns the rotation angle from the reference angle of polarization of the first signal channel and the rotation angle from the reference angle of polarization of the second signal channel based on the rotation angles of each signal channel. 2. The optical repeater device of claim 1.

[0158] (Appendix 3) The calculation means sequentially acquires the control value when a combination of the first signal channel selected from the plurality of signal channels and the second signal channel selected from the plurality of signal channels is changed, and repeats a process of matching a rotation angle from a reference angle of polarization of one of the first signal channel or the second signal channel to a rotation angle from a reference angle of polarization of the other signal channel based on each of the control values, thereby matching the rotation angles from a reference angle of polarization of all of the plurality of signal channels. 3. The optical repeater device according to claim 2.

[0159] (Appendix 4) The calculation means acquires from the control device the control value, which includes a rotation angle from a reference angle of polarization of each signal channel calculated by the control device based on the reception characteristics of each of the plurality of signal channels received from the subsequent device, and which is a difference in rotation angle that improves the reception characteristics in the subsequent device. 4. The optical repeater device according to claim 3.

[0160] (Appendix 5) The calculation means acquires the control value such that the difference between the rotation angle from the reference angle of the polarization of each signal channel when the difference in rotation angle improves the reception characteristics in the subsequent stage device, and the rotation angle from the reference angle of the polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of the polarization of a second signal channel among the plurality of signal channels is 0 or π. 5. An optical repeater according to any one of claims 2 to 4.

[0161] (Appendix 6) An optical repeater and a control device are provided, The optical repeater device a monitor means for monitoring a rotation angle of a polarization indicated by a plurality of signal channels included in the optical signal from a reference angle; a calculation means for adjusting a rotation angle of each signal channel from a reference angle of polarization to a rotation angle that improves reception characteristics of the signal channel by using a control value that controls a rotation angle of the polarization of any one of the plurality of signal channels from a reference angle of polarization; Equipped with The control device a management unit that calculates the control value based on reception characteristics of the optical signal in a downstream device that receives the optical signal relayed by the optical relay device, and outputs the control value to the optical relay device; An optical network system comprising:

[0162] (Appendix 7) The calculation means acquires the control value including the rotation angle from the reference angle of polarization of each signal channel when the difference in rotation angle results in improved reception characteristics in a subsequent device, based on the rotation angle from the reference angle of polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of polarization of a second signal channel among the plurality of signal channels, and aligns the rotation angle from the reference angle of polarization of the first signal channel and the rotation angle from the reference angle of polarization of the second signal channel based on the rotation angles of each signal channel. 7. The optical network system of claim 6.

[0163] (Appendix 8) The calculation means sequentially acquires the control value when a combination of the first signal channel selected from the plurality of signal channels and the second signal channel selected from the plurality of signal channels is changed, and repeats a process of matching a rotation angle from a reference angle of polarization of one of the first signal channel or the second signal channel to a rotation angle from a reference angle of polarization of the other signal channel based on each of the control values, thereby matching the rotation angles from a reference angle of polarization of all of the plurality of signal channels. 8. The optical network system of claim 7.

[0164] (Appendix 9) The management means of the control device The control value includes a rotation angle from a reference angle of polarization of each signal channel calculated by the control device based on the reception characteristics of each of the plurality of signal channels received from the subsequent device, the rotation angle being a difference in rotation angle that improves the reception characteristics in the subsequent device. 9. An optical network system according to any one of claims 6 to 8.

[0165] (Appendix 10) The management means generates the control value such that the difference between the rotation angle from the reference angle of the polarization of each signal channel of the plurality of signal channels and the rotation angle from the reference angle of the polarization of a first signal channel of the plurality of signal channels is 0 or π when the difference in rotation angles improves the reception characteristics in the subsequent stage device. 10. An optical network system according to any one of claims 7 to 9.

[0166] (Appendix 11) monitoring rotation angles from a reference angle of polarization indicated by a plurality of signal channels included in the optical signal; Using a control value for controlling the rotation angle of the polarization of any one of the plurality of signal channels from a reference angle, the rotation angle of the polarization of each signal channel from a reference angle is adjusted to a rotation angle at which the reception characteristics of each signal channel are improved. Optical relay method.

[0167] (Appendix 12) Based on a rotation angle from a reference angle of polarization of a first signal channel among the plurality of signal channels and a rotation angle from a reference angle of polarization of a second signal channel among the plurality of signal channels, the control value including the rotation angle from a reference angle of polarization of each signal channel when the difference in rotation angle results in improved reception characteristics in a subsequent stage device is acquired, and the rotation angle from a reference angle of polarization of the first signal channel and the rotation angle from a reference angle of polarization of the second signal channel are matched based on the rotation angles of the respective signal channels. 12. The optical relay method according to claim 11.

[0168] (Appendix 13) The control value when the combination of the first signal channel selected from the plurality of signal channels and the second signal channel selected from the plurality of signal channels is changed is acquired sequentially each time the combination is changed, and a process of matching the rotation angle from a reference angle of polarization of one of the first signal channel or the second signal channel to the rotation angle from a reference angle of polarization of the other signal channel based on each of the control values ​​is repeated to match the rotation angles from a reference angle of polarization of all of the plurality of signal channels. 13. The optical relay method according to claim 12.

[0169] (Appendix 14) The control value includes a rotation angle from a reference angle of polarization of each signal channel calculated by the control device based on the reception characteristics of each of the plurality of signal channels received from the subsequent device, the rotation angle being a difference in rotation angle at which the reception characteristics are improved in the subsequent device. 14. The optical relay method according to claim 13.

[0170] (Appendix 15) The control value is obtained such that the difference between the rotation angle from the reference angle of the polarization of each signal channel when the difference in rotation angle improves the reception characteristics in the subsequent stage device, and the difference between the rotation angle from the reference angle of the polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of the polarization of a second signal channel among the plurality of signal channels is 0 or π. 15. An optical relay method according to any one of claims 12 to 14.

[0171] (Appendix 16) The computer of the optical repeater, a monitor means for monitoring a rotation angle of a polarization indicated by a plurality of signal channels included in the optical signal from a reference angle; a calculation means for adjusting the rotation angle of each signal channel from a reference angle of polarization to a rotation angle that improves the reception characteristics of the signal channel by using a control value that controls the rotation angle of the polarization of any one of the plurality of signal channels from a reference angle of polarization; A program that functions as a

[0172] (Appendix 17) The calculation means acquires the control value including the rotation angle from the reference angle of polarization of each signal channel when the difference in rotation angle results in improved reception characteristics in a subsequent device, based on the rotation angle from the reference angle of polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of polarization of a second signal channel among the plurality of signal channels, and aligns the rotation angle from the reference angle of polarization of the first signal channel and the rotation angle from the reference angle of polarization of the second signal channel based on the rotation angles of each signal channel. 16. The program described in Appendix 16.

[0173] (Appendix 18) The calculation means sequentially acquires the control value when a combination of the first signal channel selected from the plurality of signal channels and the second signal channel selected from the plurality of signal channels is changed, and repeats a process of matching a rotation angle from a reference angle of polarization of one of the first signal channel or the second signal channel to a rotation angle from a reference angle of polarization of the other signal channel based on each of the control values, thereby matching the rotation angles from a reference angle of polarization of all of the plurality of signal channels. 17. The program described in Appendix 17.

[0174] (Appendix 19) The calculation means acquires from the control device the control value, which includes a rotation angle from a reference angle of polarization of each signal channel calculated by the control device based on the reception characteristics of each of the plurality of signal channels received from the subsequent device, and which is a difference in rotation angle that improves the reception characteristics in the subsequent device. 18. The program described in Appendix 18.

[0175] (Appendix 20) The calculation means acquires the control value such that the difference between the rotation angle from the reference angle of the polarization of each signal channel when the difference in rotation angle improves the reception characteristics in the subsequent stage device, and the rotation angle from the reference angle of the polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of the polarization of a second signal channel among the plurality of signal channels is 0 or π. 19. A program according to any one of claims 17 to 19. [Explanation of symbols]

[0176] 1. Optical network system 2. Optical repeater 3. Optical transmission line 5. Data Center 6. IT service providers 7, 8...Event venue 10. Control device 11... Management Department 12 Phase conjugate control section 13 Wavelength dispersion compensation control section 14 Carrier frequency control section 20 Optical repeater 21 Coherent receiver front-end 22 Phase conjugate section 23...chromatic dispersion compensation section 24 Coherent transmit front-end 25 Phase conjugate acquisition section 26...Chromatic dispersion compensation acquisition section 27 Carrier frequency acquisition unit 30. Transmitting terminal equipment (pre-stage equipment) 31...Previous stage device 40 Receiving terminal equipment (pre-stage equipment) 41...Late stage device 50 Optical Network System 51 Optical Network 60. Computer 61 Processor 62...Memory 90 Optical repeater 100 Control device 110 Network Management Department 120 Network control unit (management means) 130...Chromatic dispersion compensation amount calculation section 140... Phase conjugate determination unit 150 Carrier frequency control section 200 Optical repeater 201 Optical transmitter / receiver 202 Node control unit 210 Coherent receiver front end 220 Coherent transmission front end 230 Digital signal processing unit 231...chromatic dispersion compensation section 232 Phase conjugate processing unit 233 Delay adjustment unit 234 Polarization monitor unit (monitoring means) 235... Polarization rotation calculation unit (calculation means) 236 Polarization control unit 240···Receiving light source 250···Transmitting light source 260 ADC 270...DAC 300 Optical switch unit 301...Brancher 302...Multiplexer 303 Branch insertion section 310 Transmitter / receiver 311, 312, 313... Optical transceiver 401...Delay 402···Multiplier 403 Adder 411....Overlap addition section 412 Fast Fourier Transform 413...Frequency response multiplier 414...Inverse Fast Fourier Transform 415...Overlap removal section 910...Acquisition section 901 Digital signal processing unit

Claims

1. a monitor means for monitoring a rotation angle of a polarization indicated by a plurality of signal channels included in the optical signal from a reference angle; a calculation means for adjusting a rotation angle of each signal channel from a reference angle of polarization to a rotation angle that improves reception characteristics of the signal channel by using a control value that controls a rotation angle of the polarization of any one of the plurality of signal channels from a reference angle of polarization; An optical repeater device comprising:

2. The calculation means acquires the control value including the rotation angle from the reference angle of polarization of each signal channel when the difference in rotation angle results in improved reception characteristics in a subsequent device, based on the rotation angle from the reference angle of polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of polarization of a second signal channel among the plurality of signal channels, and aligns the rotation angle from the reference angle of polarization of the first signal channel and the rotation angle from the reference angle of polarization of the second signal channel based on the rotation angles of each signal channel.

2. The optical repeater according to claim 1.

3. The calculation means sequentially acquires the control value when a combination of the first signal channel selected from the plurality of signal channels and the second signal channel selected from the plurality of signal channels is changed, and repeats a process of matching a rotation angle from a reference angle of polarization of one of the first signal channel or the second signal channel to a rotation angle from a reference angle of polarization of the other signal channel based on each of the control values, thereby matching the rotation angles from a reference angle of polarization of all of the plurality of signal channels.

3. The optical repeater according to claim 2.

4. The calculation means acquires from the control device the control value, which includes a rotation angle from a reference angle of polarization of each signal channel calculated by the control device based on the reception characteristics of each of the plurality of signal channels received from the subsequent device, and which is a difference in rotation angle that improves the reception characteristics in the subsequent device.

4. The optical repeater according to claim 3.

5. An optical repeater and a control device are provided, The optical repeater device a monitor means for monitoring a rotation angle of a polarization indicated by a plurality of signal channels included in the optical signal from a reference angle; a calculation means for adjusting a rotation angle of each signal channel from a reference angle of polarization to a rotation angle that improves reception characteristics of the signal channel by using a control value that controls a rotation angle of the polarization of any one of the plurality of signal channels from a reference angle of polarization; Equipped with The control device a management unit that calculates the control value based on reception characteristics of the optical signal in a downstream device that receives the optical signal relayed by the optical relay device, and outputs the control value to the optical relay device; An optical network system comprising:

6. The calculation means acquires the control value including the rotation angle from the reference angle of polarization of each signal channel when the difference in rotation angle results in improved reception characteristics in a subsequent device, based on the rotation angle from the reference angle of polarization of a first signal channel among the plurality of signal channels and the rotation angle from the reference angle of polarization of a second signal channel among the plurality of signal channels, and aligns the rotation angle from the reference angle of polarization of the first signal channel and the rotation angle from the reference angle of polarization of the second signal channel based on the rotation angles of each signal channel.

6. The optical network system according to claim 5.

7. The calculation means sequentially acquires the control value when a combination of the first signal channel selected from the plurality of signal channels and the second signal channel selected from the plurality of signal channels is changed, and repeats a process of matching a rotation angle from a reference angle of polarization of one of the first signal channel or the second signal channel to a rotation angle from a reference angle of polarization of the other signal channel based on each of the control values, thereby matching the rotation angles from a reference angle of polarization of all of the plurality of signal channels.

7. The optical network system according to claim 6.

8. The management means of the control device The control value includes a rotation angle from a reference angle of polarization of each signal channel calculated by the control device based on the reception characteristics of each of the plurality of signal channels received from the subsequent device, the rotation angle being a difference in rotation angle that improves the reception characteristics in the subsequent device.

8. The optical network system according to claim 5, wherein the optical network system comprises:

9. monitoring rotation angles from a reference angle of polarization indicated by a plurality of signal channels included in the optical signal; Using a control value for controlling the rotation angle of the polarization of any one of the plurality of signal channels from a reference angle, the rotation angle of the polarization of each signal channel from a reference angle is adjusted to a rotation angle at which the reception characteristics of each signal channel are improved. Optical relay method.

10. The computer of the optical repeater, a monitor means for monitoring a rotation angle of a polarization indicated by a plurality of signal channels included in the optical signal from a reference angle; a calculation means for adjusting the rotation angle of each signal channel from a reference angle of polarization to a rotation angle that improves the reception characteristics of the signal channel by using a control value that controls the rotation angle of the polarization of any one of the plurality of signal channels from a reference angle of polarization; A program that functions as a

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