Optical Network System, Control Device, Control Method, and Control Program

Abstract

This optical network system comprises: an optical relay device (20) forming an optical network; and a control device (10) that controls the optical relay device (20), wherein the control device (10) includes a management unit (11) that manages wavelength information of an optical signal transmitted and received by the optical relay device (20) on a path of an optical network and transmission line information of an optical transmission line connected to the optical relay device (20), and a compensation control unit (12) that determines a chromatic dispersion compensation amount to be compensated in the optical relay device (20), on the basis of the wavelength information and the transmission line information.

Description

Technical Field

[0001] The present invention relates to an optical network system, a control device, an optical relay device, a control method, and a non-transitory computer-readable medium.

Background Art

[0002] In recent years, the introduction of 5G wireless communication systems has been progressing. For the post-5G era, there is an increasing demand not only for wireless communication but also in the field of optical communication for higher speeds, further lower latency, and the ability to support a large number of simultaneous connections. Therefore, research is being conducted on the application of optical communication systems to various communication services and industrial uses.

[0003] For example, in backbone optical communication systems, by using a digital coherent method that combines an optical phase modulation method and polarization multiplexing separation technology, a large capacity exceeding 100 Gbps (Giga bit per second) has been achieved. Furthermore, research and development of a transmission method that improves frequency utilization efficiency and enables a large number of simultaneous connections by narrowing the signal band and performing wavelength division multiplexing (WDM) are also being carried out.

[0004] As related technologies, for example, Patent Documents 1 to 3 are known. Patent Document 1 discloses a wavelength converter that converts the wavelength of an optical signal using a coherent method at the receiving end and the transmitting end. Patent Document 2 discloses connecting an optical phase conjugate device that generates a phase conjugate signal by digital signal processing between a transmitting device and a receiving device. Patent Document 3 discloses connecting a dispersion compensation module that compensates for wavelength dispersion in an optical transmission path between a transmitting device and a receiving device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in related technologies such as Patent Documents 1 to 3, in an optical network system where the network path (route) switches according to the situation, changes in the characteristics of the optical transmission path accompanying the route switch are not considered, and the expected effect cannot be obtained, or there is a problem that the signal quality may deteriorate because the system cannot respond to the route switch.

[0007] In view of such problems, the present disclosure aims to provide an optical network system, a control device, an optical relay device, a control method, and a non-transitory computer-readable medium capable of suppressing deterioration of signal quality even in an optical network system where the network path switches appropriately.

Means for Solving the Problems

[0008] The optical network system according to the present disclosure includes an optical relay device that constitutes an optical network and a control device that controls the optical relay device. The control device includes a management unit that manages wavelength information of an optical signal transmitted and received by the optical relay device in a path of the optical network and transmission path information of an optical transmission path connected to the optical relay device, and a compensation control unit that determines a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information. The optical relay device includes an acquisition unit that acquires the determined wavelength dispersion compensation amount from the control device, and a wavelength dispersion compensation unit that performs wavelength dispersion compensation processing on an electrical signal based on a received optical signal based on the acquired wavelength dispersion compensation amount.

[0009] The control device according to the present disclosure includes a management unit that manages wavelength information of an optical signal transmitted and received by an optical relay device in a path of an optical network and transmission path information of an optical transmission path connected to the optical relay device, and a compensation control unit that determines a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information.

[0010] The optical relay device according to the present disclosure includes an acquisition unit that acquires a wavelength dispersion compensation amount from a control device, a coherent optical reception front-end unit that performs coherent detection of a received optical signal based on local light emission and outputs the coherently detected electrical signal, a wavelength dispersion compensation unit that performs wavelength dispersion compensation processing on the electrical signal by digital signal processing based on the acquired wavelength dispersion compensation amount, and a coherent optical transmission front-end unit that coherently modulates the electrical signal subjected to the wavelength dispersion compensation based on transmission light and transmits the coherently modulated optical signal.

[0011] The control method according to the present disclosure manages wavelength information of an optical signal transmitted and received by an optical relay device in a path of an optical network and transmission path information of an optical transmission path connected to the optical relay device, and determines a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information.

[0012] A non-transitory computer-readable medium storing a control program according to the present disclosure is a non-transitory computer-readable medium storing a control program for causing a computer to execute a process of managing wavelength information of an optical signal transmitted and received by an optical relay device in a path of an optical network and transmission path information of an optical transmission path connected to the optical relay device, and determining a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information.

Advantages of the Invention

[0013] According to the present disclosure, it is possible to provide an optical network system, a control device, an optical relay device, a control method, and a non-transitory computer-readable medium that can suppress deterioration of signal quality even in an optical network system in which a network path is appropriately switched.

Brief Description of the Drawings

[0014] [Figure 1] It is a block diagram showing a configuration example of an optical network system according to a basic example. [Diagram 2] It is a block diagram showing a configuration example of an optical relay device according to a basic example. [Diagram 3] It is a block diagram showing the configuration of an optical transceiver according to Study Example 1. [Figure 4] It is a diagram for explaining the problems of the optical transceiver according to Study Example 1. [Diagram 5] It is a diagram for explaining the problems of the optical transceiver according to Study Example 1. [Figure 6] It is a diagram for explaining the configuration and problems of the optical transceiver according to Study Example 2. [Figure 7] It is a block diagram showing the configuration of an optical transceiver according to Study Example 3. [Figure 8A] It is a diagram for explaining the problems of the optical transceiver according to Study Example 3. [Figure 8B] It is a diagram for explaining the problems of the optical transceiver according to Study Example 3. [Figure 9] It is a graph showing the wavelength dispersion characteristics of wavelength - wavelength dispersion. [Figure 10] It is a block diagram showing the schematic configuration of a control device according to an embodiment. [Figure 11] It is a block diagram showing the schematic configuration of an optical relay device according to an embodiment. [Figure 12] It is a block diagram showing the schematic configuration of an optical relay device according to an embodiment. [Figure 13] It is a block diagram showing a configuration example of an optical network system according to Embodiment 1. [Figure 14] It is a configuration showing configuration examples of each device in the optical network system according to Embodiment 1. [Figure 15] This is a configuration diagram showing an example of the configuration of the wavelength dispersion compensation unit according to Embodiment 1. [Figure 16] This is a configuration diagram showing an example of the configuration of the wavelength dispersion compensation unit according to Embodiment 1. [Figure 17] This is a flowchart showing an example of the operation of the optical network system according to Embodiment 1. [Figure 18A] This is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 1. [Figure 18B] This is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 1. [Figure 19A] This is a diagram showing another specific example of wavelength dispersion compensation by the control method according to Embodiment 1. [Figure 19B] This is a diagram showing another specific example of wavelength dispersion compensation by the control method according to Embodiment 1. [Figure 20A] This is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 2. [Figure 20B] This is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 2. [Figure 21A] This is a diagram showing another specific example of wavelength dispersion compensation by the control method according to Embodiment 2. [Figure 21B] This is a diagram showing another specific example of wavelength dispersion compensation by the control method according to Embodiment 2. [Figure 22] This is a configuration diagram showing an example of the configuration of the optical network system according to Embodiment 3. [Diagram 23] This is a flowchart showing an example of the operation of the optical network system according to Embodiment 3. [Figure 24A] This is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 3. [Figure 24B] This is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 3. [Diagram 25] This is a configuration diagram showing an example of the configuration of the optical network system according to Embodiment 4. [Figure 26]It is a flowchart showing an operation example of the optical network system according to Embodiment 4. [Figure 27A] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 4. [Figure 27B] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to Embodiment 4. [Figure 28A] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to other embodiments. [Figure 28B] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to other embodiments. [Figure 29A] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to other embodiments. [Figure 29B] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to other embodiments. [Figure 30A] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to other embodiments. [Figure 30B] It is a diagram showing a specific example of wavelength dispersion compensation by the control method according to other embodiments. [Diagram 31] It is a configuration diagram showing a configuration example of an optical relay device according to other embodiments. [Diagram 32] It is a configuration diagram showing a configuration example of an optical relay device according to other embodiments. [Diagram 33] It is a configuration diagram showing an overview of the hardware of a computer according to an embodiment.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments will be described with reference to the drawings. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations are omitted as necessary. Note that the arrows attached to the configuration diagrams (block diagrams) are for illustrative purposes and do not limit the type or direction of signals.

[0016] (Considerations Leading to the Embodiment) FIG. 1 shows the configuration of an optical network system according to a basic example that forms the basis of the present embodiment. The optical network system 1 according to the basic example is, for example, a backbone wavelength division multiplexing optical transmission system. It performs wavelength division multiplexing and conducts high-level modulation and digital coherent transmission using optical signals of each wavelength to achieve high-capacity communication exceeding 100 Gbps. By means of high-density wavelength division multiplexing, it is possible to improve the utilization efficiency of the optical frequency and to cope with mobile traffic and wavelength defragmentation. Also, due to wavelength division multiplexing, the transmission path (wavelength path) can be flexibly switched while the optical signal remains intact. Therefore, by switching the transmission path in case of a failure, the failure can be avoided and the infrastructure can be maintained. Furthermore, in the basic example, towards the post-5G era, the real-time performance is improved and the system can support ultra-low latency.

[0017] As shown in FIG. 1, the optical network system 1 according to the basic example includes a plurality of optical relay devices 2 (for example, 2-1 to 2-10) connected so as to be optically communicable via an optical transmission path (optical fiber transmission path) 3. The optical relay device 2 is a photonic node capable of relaying wavelength-division multiplexed optical signals, and is, for example, a ROADM (Reconfigurable Optical Add / Drop Multiplexer) device.

[0018] A wavelength path (simply also referred to as a path) is assigned to each optical relay device 2, and the traffic of a local network or another optical relay device 2 accommodated via the assigned wavelength path is transferred. For example, the optical relay device 2-1 accommodates the network of the data center 4, the optical relay device 2-2 accommodates the network of the data center 5, and transfers high-capacity traffic such as a video distribution service that distributes high-quality video (4K / 8K). When the optical relay device 2-1 and the optical relay device 2-2 transfer the traffic between the data center 4 and the data center 5 via the wavelength path P1, if a failure occurs in the wavelength path P1, the wavelength path P1 is switched to the wavelength path P2. Thereby, the transfer of the traffic between the data center 4 and the data center 5 can be maintained via a detour path including the optical relay device 2-3 and the optical relay device 2-4.

[0019] For example, the optical relay device 2-5 accommodates the IoT sensor network of the IT service provider 6, and the optical relay device 2-8 accommodates the mobile network of the event venue 7. The traffic of the mobile network is spot traffic due to moving users. When the optical relay device 2-5 and the optical relay device 2-8 transfer the traffic between the IT service provider 6 and the event venue 7 via the wavelength path P3 including the optical relay devices 2-6 and 2-7, when the user at the event venue 7 moves to the event venue 8, the wavelength path P3 is switched to the wavelength path P4. Thereby, the transfer of the traffic of the user who has moved to the event venue 8 can be maintained via the optical relay devices 2-6, 2-4, and 2-10.

[0020] Figure 2 shows a configuration example of the optical relay device 2 according to the basic example. The optical relay device 2 branches / inserts wavelength-division multiplexed signals and performs coherent demodulation and modulation on the signals of each wavelength to be branched / inserted. As shown in Figure 2, the optical relay device 2 includes an optical switch unit 300 and a transceiver unit 310.

[0021] The optical switch unit 300 transfers the optical signal of a predetermined wavelength path received from the optical relay device 2 in the previous stage in the optical network system 1 to the optical relay device 2 in the subsequent stage, and branches / inserts the received optical signal for each wavelength. For example, the optical switch unit 300 includes a demultiplexer 301, a multiplexer 302, and a branch / insertion unit 303. The demultiplexer 301 separates the optical signal received from the optical transmission line 3 into optical signals of a plurality of wavelengths. The multiplexer 302 multiplexes the optical signals of a plurality of wavelengths into one optical signal and transmits it to the optical transmission line 3. The branch / insertion unit 303 branches / inserts the optical signal of each wavelength between the demultiplexer 301 and the multiplexer 302.

[0022] The transceiver (transponder) 310 receives the optical signals of each wavelength branched from the branching / insertion unit 303 of the optical switch unit 300, and outputs the received data obtained by coherent demodulation to a local device (network) that stores the data. Also, the transceiver 310 inputs transmission data from the local device, and transmits (inserts) the optical signals of each wavelength obtained by coherent modulation to the branching / insertion unit 303 of the optical switch unit 300. The transceiver 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 or different from the received wavelength).

[0023] Here, when using the optical transceivers of Study Examples 1 to 3 as the optical transceiver 311, the problems that occur will be studied.

[0024] FIG. 3 shows a configuration example of the optical transceiver according to Study Example 1. As shown in FIG. 3, the optical transceiver 312 according to Study Example 1 includes a coherent reception front-end unit 210, a coherent transmission front-end unit 220, and a digital signal processing unit 900.

[0025] The coherent reception front-end unit 210 performs coherent detection on the optical signal received from the preceding optical relay device 2 by local light emission (local oscillator (LO) light) of a predetermined wavelength, and outputs the detected signal to the digital signal processing unit 900. The coherent transmission front-end unit 220 optically modulates (coherently modulates) the signal processed by the digital signal processing unit 900 to a predetermined wavelength, and transmits the generated optical signal to the next-stage optical relay device 2. The digital signal processing unit 900 is a DSP (Digital Signal Processor), which converts the signal coherently detected by the coherent reception front-end unit 210 into a digital signal, outputs the decoded received data, and also encodes the input transmission data and converts it into a signal for optical modulation, and outputs the signal to the coherent transmission front-end unit 220. In Study Example 1, the digital signal processing unit 900 performs decoding, error correction, etc. to reproduce the data.

[0026] When the optical relay device 2 using the optical transceiver 312 of Study Example 1 relays an optical signal, as shown in FIG. 4, consider the case where optical signals of the same wavelength collide. For example, when a wavelength path P5 is set between the optical relay device 2-2 and the optical relay device 2-5 and traffic is being transferred between the IT service provider 6 and the data center 5, and a wavelength path P6 is set between the optical relay device 2-2 and the optical relay device 2-8 and traffic is being transferred between the event venue 7 and the data center 5. At this time, when the wavelength slots of the wavelength path P5 and the wavelength path P6 are λa, in the optical relay device 2-7, the optical signal S1 of the wavelength path P5 and the optical signal S2 of the wavelength path P6 collide.

[0027] In this case, a method of avoiding the collision by switching the wavelength path P5 or the wavelength path P6 to another path can be considered, but the wavelength slot of the other path is not always available. Even if the path is switched, there is a risk that the latency will increase due to the detour path. In addition, in the optical switch of the optical relay device, a method of collectively converting a certain wavelength band including optical signals of a plurality of channels into another wavelength band as optical signals using a wavelength conversion device or the like by an optical element can be considered, but in this case, switching cannot be performed in units of signal channels.

[0028] Therefore, as shown in FIG. 5, a method of converting an optical signal into an empty wavelength slot in the optical relay device 2-7 where a collision occurs can be considered. For example, in the optical transceiver 312 of the optical relay device 2-7, the wavelength of the optical signal of the wavelength path P6 is converted from λ1 to λ2. As a result, in the path from the optical relay device 2-7 to the optical relay device 2-2, the wavelengths of the optical signal S1 of the wavelength path P5 and the optical signal S2 of the wavelength path P6 are different, so the collision can be avoided.

[0029] However, in the case of FIG. 5, when wavelength conversion and folding back are performed by the optical transceiver 312, there is a problem that the latency increases for regeneration relay. That is, in the digital signal processing unit 900 of the optical transceiver 312, complex digital signal processing and error correction processing are performed, so the latency is large. In addition, the circuit size for digital signal processing is large, and the power consumption is also large.

[0030] Therefore, Consideration Example 2 based on the disclosure of Patent Document 1 can be considered. In Consideration Example 2, in the optical transceiver, the optical signal is folded back without using the digital signal processing unit of the optical transceiver. FIG. 6 shows an example in which the optical transceiver 313 according to Consideration Example 2 is applied to the network of FIG. 5.

[0031] As shown in FIG. 6, in Consideration Example 2, in the optical transceiver 313, the analog signal output from the coherent reception front-end unit 210 is folded back and relayed to the coherent transmission front-end unit 220 without passing through digital signal processing. That is, in Consideration Example 2, wavelength conversion is performed by performing optical-electrical (analog)-optical conversion without passing through digital signal processing with a complex and large delay. Thereby, miniaturization and power saving can be achieved, and an increase in latency due to complex digital signal processing can be suppressed.

[0032] However, in Consideration Example 2, there is a problem that waveform distortion of the optical signal generated when passing through a plurality of optical relay devices (optical transceiver circuits) and optical fiber transmission lines is not considered, and the signal quality may deteriorate.

[0033] In contrast, Consideration Example 3 based on the disclosure of Patent Document 2 can be considered. In Consideration Example 3, in the optical transceiver, wavelength dispersion compensation is enabled by performing phase conjugation processing by digital processing. FIG. 7 shows a configuration example of the optical transceiver according to Consideration Example 3.

[0034] As shown in FIG. 7, the optical transceiver 314 according to Consideration Example 3 includes a coherent reception front-end unit 210, a coherent transmission front-end unit 220, and a digital signal processing unit 901.

[0035] In Consideration Example 3, different from Consideration Example 1, in the digital signal processing unit 901, data regeneration such as error correction is not performed, and only phase conjugation processing for the digital signal is performed. Thereby, while suppressing an increase in latency due to complex error correction processing and the like, deterioration of signal quality due to wavelength dispersion and the like can be suppressed.

[0036] Figures 8A and 8B show the amount of wavelength dispersion when using the optical relay device 90 including the optical transceiver 314 according to Study Example 3. As shown in FIG. 8A, an optical relay device 90 is connected between the transmitting end station device (transmitting end) 30 and the receiving end station device (receiving end) 40 via optical transmission lines 3a and 3b. In Study Example 3, as a premise, the optical transmission line 3a and the optical transmission line 3b are of the same distance. An optical signal with a wavelength of λ1 is transmitted through the optical transmission line 3a, and an optical signal with a wavelength of λ1' close to the wavelength λ1 is transmitted through the optical transmission line 3b.

[0037] Note that in the configuration where the optical relay device is connected to the path from the transmitting end station device to the receiving end station device as shown in FIG. 8A, the side of the transmitting end station device with respect to the optical relay device is sometimes referred to as the front side (the receiving side of the optical signal) of the optical relay device, and the side of the receiving end station device with respect to the optical relay device is sometimes referred to as the rear side (the transmitting side of the optical signal) of the optical relay device. Also, the optical transmission line between the optical relay device and the transmitting end station device is sometimes referred to as the first half (the first part) of the optical transmission line, and the optical transmission line between the optical relay device and the receiving end station device is sometimes referred to as the second half (the second part) of the optical transmission line.

[0038] As shown in FIG. 8B, the amount of wavelength dispersion increases in proportion to the distance of the optical transmission line. For this reason, when the optical relay device relays the optical signal only by simple signal amplification, the amount of wavelength dispersion continues to increase according to the distance from the transmitting end station device 30 to the receiving end station device 40. Then, as the distance of the optical transmission line becomes longer, the quality of the optical signal received by the receiving end station device 40 deteriorates significantly.

[0039] In Study Example 3, the optical relay device 90 is arranged at the central point of the total transmission distance to perform optical phase conjugation. By performing phase conjugation processing on the optical signal in the optical relay device 90, the wavelength dispersion (N1) accumulated in the first half of the optical transmission line 3a of the path is inverted to the negative-side wavelength dispersion (N1) with the same dispersion amount. As a result, the influence of the waveform distortion received in the second half of the optical transmission line 3b of the path is offset because it receives the opposite influence to the influence of the waveform distortion received in the first half of the optical transmission line 3a, and the amount of wavelength dispersion becomes zero at the receiving end station device 40. Therefore, the influences of wavelength dispersion and SPM (Self Phase Modulation ) non-linearity can be mitigated.

[0040] Also, as a third study example, based on the disclosure of Patent Document 2, a method of converting the wavelength frequency to suppress the non-linear influence in the optical relay device can also be considered. That is, when relaying a plurality of wavelengths by a plurality of transceivers in the optical relay device, for a plurality of signal channels with continuous carrier frequencies, the carrier frequencies are mapped in reverse order, and wavelength conversion is performed, so that XPM (Cross Phase Modulation ) non-linear influence reduction techniques and the like are also disclosed.

[0041] However, as a result of studying the third study example, the inventor found the following problems. That is, in the third study example, Point-to-Point WDM transmission is assumed. In order to obtain the above effects, it is a prerequisite that the distances of the first half and the second half of the optical transmission path are about the same, and wavelength conversion is performed at adjacent carrier frequencies (wavelengths).

[0042] However, in the case of a system that avoids wavelength collisions including path switching in the optical network shown in FIG. 1 and the like, the distances of the optical transmission paths before and after the optical relay device in the transmission path are not necessarily about the same. There may be a case where the distances between the first half and the second half of the optical transmission path are greatly asymmetric. For this reason, the cancellation effect of waveform distortion due to wavelength dispersion and fiber non-linearity generated in the optical transmission paths before and after the optical relay device may not be sufficiently obtained.

[0043] FIG. 9 shows the wavelength dispersion characteristics of wavelength-wavelength dispersion. As shown in FIG. 9, the wavelength dispersion characteristics change depending on the wavelength (frequency). The greater the wavelength interval between two optical signals, the more different the wavelength dispersion characteristics of the two optical signals. For example, for wavelength collision avoidance in an optical network, it is assumed that wavelength conversion is performed between the C band (1528 to 1565 nm) and the L band (1570 to 1605 nm). In particular, with the increase in capacity, mutual wavelength conversion between the C band / L band is required, and in the future, conversion to another wavelength band may also be possible. Then, when performing wavelength conversion in an optical relay device, since the carrier frequency before conversion and the carrier frequency after conversion are widely separated, the wavelength dispersion characteristics also change significantly. Therefore, even if the distances of the optical transmission paths before and after the relay device are about the same, the influence of wavelength dispersion can change greatly, and a sufficient waveform distortion mitigation effect cannot be expected.

[0044] Therefore, in Study Example 3, simply relaying by simple optical phase conjugation cannot sufficiently suppress and mitigate the influence of waveform distortion occurring in the optical transmission path. For this reason, in the embodiment, even when the optical transmission paths before and after the optical relay device are asymmetric or when performing mutual wavelength conversion between the C band / L band, it is possible to mitigate the influence of wavelength dispersion and fiber nonlinearity in the optical transmission path.

[0045] (Outline of the Embodiment) FIG. 10 shows the schematic configuration of the control device according to the embodiment, and FIGS. 11 and 12 show the schematic configuration of the optical relay device according to the embodiment. The optical relay device 20 according to the embodiment constitutes an optical network, and the control device 10 according to the embodiment controls the optical relay device 20 in the optical network. The control device 10 and the optical relay device 20 constitute an optical network system.

[0046] As shown in FIG. 10, the control device 10 includes a management unit 11 and a compensation control unit 12. The management unit 11 manages the wavelength information of the optical signals transmitted and received by the optical relay device 20 in the path of the optical network and the transmission path information of the optical transmission path connected to the optical relay device 20. The compensation control unit 12 determines the wavelength dispersion compensation amount to be compensated in the optical relay device 20 based on the wavelength information and the transmission path information managed by the management unit 11.

[0047] As shown in Fig. 11, the optical relay device 20 includes a coherent reception front-end unit 21, a chromatic dispersion compensation unit 22, a coherent transmission front-end unit 23, and an acquisition unit 24. Also, as shown in Fig. 12, the optical relay device 20 may include a chromatic dispersion compensation unit 22 and an acquisition unit 24.

[0048] The acquisition unit 24 acquires the chromatic dispersion compensation amount determined by the compensation control unit 12 from the control device 10. The coherent reception front-end unit 21 performs coherent detection on the received optical signal based on local light emission, and outputs the electrically detected signal after coherent detection. The chromatic dispersion compensation unit 22 performs chromatic dispersion compensation processing on the electrical signal output from the coherent reception front-end unit 21 by digital signal processing based on the chromatic dispersion compensation amount acquired by the acquisition unit 24. The coherent transmission front-end unit 23 coherently modulates the electrical signal subjected to chromatic dispersion compensation processing by the chromatic dispersion compensation unit 22 based on transmission light, and transmits the coherently modulated optical signal.

[0049] In this way, in the embodiment, in the control device, based on the wavelength information of the optical signal transmitted and received by the optical relay device in the path and the transmission line information of the optical transmission line connected to the optical relay device, the chromatic dispersion compensation amount in the optical relay device is determined, and in the optical relay device, chromatic dispersion compensation is performed with the determined compensation amount. Thereby, in the optical relay device, chromatic dispersion compensation can be performed with an appropriate compensation amount, so that deterioration of signal quality can be effectively suppressed.

[0050] (Embodiment 1) Next, Embodiment 1 will be described with reference to the drawings.

[0051] Fig. 13 shows a configuration example of the optical network system according to the present embodiment. As shown in Fig. 13, the optical network system 50 according to the present embodiment includes a control device 100, a plurality of optical relay devices 200, a transmitting end station device 30, and a receiving end station device 40.

[0052] Between the plurality of optical relay devices 200, the transmitting end station device 30, and the receiving end station device 40, they are optically communicably connected via the optical transmission line 3. Between the plurality of optical relay devices 200, the transmitting end station device 30, the receiving end station device 40, and the control device 100, they are communicably connected for control signals. Between the plurality of optical relay devices 200, the transmitting end station device 30, the receiving end station device 40, and the control device 100, they may be connected via the optical transmission line 3, or may be communicably connected by any other transmission path including wired or wireless.

[0053] The plurality of optical relay devices 200, the transmitting end station device 30, and the receiving end station device 40 are optical transmission devices (optical nodes) that perform optical communication via the optical transmission line 3. The transmitting end station device 30 and the receiving end station device 40 constitute the transmitting end and the receiving end in the path. The transmitting end station device 30 transmits an optical signal wavelength-division multiplexed by the wavelength of the path set by the control device 100 to the receiving end station device 40 via the optical transmission line 3. The receiving end station device 40 receives an optical signal wavelength-division multiplexed by the wavelength of the path set by the control device 100 from the transmitting end station device 30 via the optical transmission line 3.

[0054] The plurality of optical relay devices 200 are relay devices capable of relaying wavelength-division multiplexed optical signals, similar to the basic example. The plurality of optical relay devices 200 constitute an optical network 51 that performs WDM communication. It can also be said that the plurality of optical relay devices 200, together with the transmitting end station device 30 and the receiving end station device 40, constitute the optical network 51. The optical network 51 is a wavelength-division 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. Also, the plurality of optical relay devices 200 configure a path from the transmitting end station device 30 to the receiving end station device 40 in response to control from the control device 100, and transmit an optical signal (data) according to the wavelength set on the path of the path.

[0055] The control device 100 manages and controls an optical network 51 including a plurality of optical relay devices 200. For example, the control device 100 is an NMS (Network Management System) that manages the network.

[0056] The control device 100 manages and controls the paths formed by the optical relay devices 200 in the optical network 51. The control device 100 manages the path and wavelength from the transmitting terminal device 30 to the receiving terminal device 40, and sets the path, wavelength, etc. for the transmitting terminal device 30, the receiving terminal device 40, and the optical relay devices 200 on the path.

[0057] FIG. 14 shows a configuration example of each device in the optical network system according to the present embodiment. As shown in FIG. 14, the control device 100 includes a network management unit 110, a network control unit 120, and a parameter calculation unit 130.

[0058] The network management unit 110 manages information necessary for network management such as network configuration information and path configuration information in the optical network 51. For example, the network management unit 110 may be configured by a database that stores information necessary for network management. The network configuration information includes the connection relationships of the optical relay devices 200, the transmitting terminal device 30, and the receiving terminal device 40 that constitute the network, and the transmission path information of the optical transmission paths 3 that connect between the devices. The transmission path information includes the distance (line length) of the optical transmission path, and may include the structure and type of the optical fiber, transmission characteristics, etc. The path configuration information includes information on each device that constitutes the path, the wavelengths available for each device on the path, and the usage status of the wavelengths. These pieces of information may be set in the database in advance, may be set based on information collected from each device, and may be further updated by the network control unit 120 or the like.

[0059] The network control unit 120 controls the paths in the optical network 51, the optical relay devices 200 constituting the paths, the transmitting end station device 30, and the receiving end station device 40. The network control unit 120 refers to network configuration information, path configuration information, etc. in the network management unit 110, determines the path and wavelength of the path from the transmitting end station device 30 to the receiving end station device 40, and sets the determined path and wavelength in the transmitting end station device 30, the receiving end station device 40, and the optical relay devices 200 on the path of the path. The wavelength of the path is determined for each optical transmission line in the path of the path. For example, when the path of a path overlaps with the path of another path, different wavelengths are selected from the available wavelengths in the optical transmission line of the overlapping section among the paths. Further, the network control unit 120 outputs information necessary for calculating the wavelength dispersion compensation amount in the optical relay device 200 constituting the path to the parameter calculation unit 130. For example, the network control unit 120 outputs the received wavelength information (wavelength information of the received optical signal), transmitted wavelength information (wavelength information of the transmitted optical signal), and transmission line information of the front and rear optical transmission lines of the optical relay device 200.

[0060] The parameter calculation unit 130 calculates parameters for controlling the optical relay device 200 constituting the path. In this example, the parameter calculation unit 130 calculates the wavelength dispersion compensation amount for the optical relay device 200 to perform wavelength dispersion compensation. The parameter calculation unit 130 is a compensation control unit that determines and controls the wavelength dispersion compensation amount of the optical relay device 200. The parameter calculation unit 130 determines the optimal wavelength dispersion compensation amount for the optical relay device 200 based on the received wavelength information, transmitted wavelength information, and front and rear transmission line information of the optical relay device 200 obtained from the network control unit 120. The parameter calculation unit 130 notifies the corresponding optical relay device 200 of the received wavelength information, transmitted wavelength information, and optimal wavelength dispersion compensation amount of the optical relay device 200.

[0061] Also, as shown in FIG. 14, the optical relay device 200 according to the present embodiment includes an optical transceiver 201 and a node control unit 202. Although not shown in FIG. 14, similar to the basic example of FIG. 2, the optical relay device 200 includes an optical switch unit 300 and a transceiver unit 310, and the transceiver unit 310 includes a plurality of optical transceivers 201. That is, the node control unit 202 can control the optical switch unit 300 and the transceiver unit 310 (a plurality of optical transceivers 201).

[0062] The optical transceiver 201 includes a coherent reception front-end unit 210, a coherent transmission front-end unit 220, a digital signal processing unit 230, a reception light source 240, a transmission light source 250, an ADC 260, and a DAC 270.

[0063] The reception light source 240 generates local light emission r1 with a wavelength (frequency) set by the node control unit 202 and outputs the generated local light emission r1 to the coherent reception front-end unit 210. The transmission light source 250 generates transmission light r2 with a wavelength (frequency) set by the node control unit 202 and outputs the generated transmission light r2 to the coherent transmission front-end unit 220.

[0064] The frequency (wavelength) of the local light emission r1 is the frequency (carrier frequency) of the input optical signal SO1 to be received, and the frequency of the transmission light r2 is the frequency of the output optical signal SO2 to be transmitted. For example, although the local light emission r1 and the transmission light r2 have different frequencies, they may also have the same frequency. By changing the frequencies of the local light emission r1 and the transmission light r2, the wavelength of the optical signal to be relayed can be switched. Thereby, the input optical signal SO1 can be converted into an output optical signal SO2 with a different wavelength.

[0065] The coherent reception front - end unit 210 and the coherent transmission front - end unit 220 have the same configuration as that in FIG. 3. The coherent reception front - end unit 210 is an optical / electrical conversion unit that converts an optical signal into an electrical signal and is a coherent detection unit that performs coherent detection. The coherent reception front - end unit 210 performs coherent detection on the input input optical signal SO1 (received optical signal) based on the local oscillation light r1 and outputs the generated analog signal SA1 (first analog electrical signal).

[0066] ADC( Analog / Digital Converter) 260 performs AD conversion on the analog signal SA1 generated by the coherent reception front - end unit 210 and outputs the converted digital signal SD1 (first digital electrical signal).

[0067] DAC(Digital / Analog Converter) 270 performs DA conversion on the digital signal SD2 (second digital electrical signal) signal - processed by the digital signal processing unit 230 and outputs the converted analog signal SA2 (second analog electrical signal).

[0068] The coherent transmission front - end unit 220 is an electrical / optical conversion unit that converts an electrical signal into an optical signal and is a coherent modulation unit that performs coherent modulation. The coherent transmission front - end unit 220 performs coherent modulation on the analog signal SA2 DA - converted by the DAC270 based on the transmission light r2 and outputs the generated output optical signal SO2 (transmission optical signal).

[0069] For example, the input optical signal SO1 and the output optical signal SO2 are phase - modulated and polarization - multiplexed optical signals. The analog signals SA1 and SA2, and the digital signals SD1 and SD2 are 4 - lane (4ch) signals including the I X signal of the I - component (in - phase component) of the X - polarization, the Q X signal of the Q - component (quadrature component) of the X - polarization, the I Y signal of the I - component of the Y - polarization, and the Q Y signal of the Q - component of the Y - polarization.

[0070] The digital signal processing unit 230 performs digital signal processing on the digital signal SD1 converted by the ADC 260 and outputs the digital signal SD2 after digital signal processing. The digital signal processing unit 230 is a digital circuit that performs predetermined digital signal processing for compensating signal quality. The digital signal processing unit 230 processes the I X signal, Q X signal, I Y signal, Q Y signal, all or part (X polarization or Y polarization) of each of them, and performs digital signal processing.

[0071] The digital signal processing unit 230 does not perform processing with a large delay such as error correction (data reproduction), but only performs specific signal compensation processing. Thereby, while suppressing signal delay, the necessary signal quality can be compensated. In the present embodiment, the digital signal processing unit 230 includes a chromatic dispersion compensation unit 231 that performs chromatic dispersion processing.

[0072] The chromatic dispersion compensation unit 231 compensates for the chromatic dispersion generated in the optical signal in the optical transmission path according to the control (setting) from the node control unit 202. The chromatic dispersion compensation unit 231 compensates for the set chromatic dispersion compensation amount by performing digital signal processing on the input digital signal SD1.

[0073] Chromatic dispersion compensation by digital signal processing can be realized by convolution processing of the impulse response of the inverse transfer function of the optical transmission path and the received signal. Therefore, for example, the chromatic dispersion compensation unit 231 may be configured by a transversal filter (FIR filter). Since the characteristics of the optical transmission path can be modeled by an FIR filter, chromatic dispersion can be compensated by an FIR filter with its inverse characteristics.

[0074] FIG. 15 is a configuration example when the wavelength dispersion compensation unit 231 is configured by a FIR filter (digital filter). In the example of FIG. 15, the wavelength dispersion compensation unit 231 includes a plurality of delay elements 401, a plurality of multipliers 402, and an adder 403. The plurality of delay elements 401 are connected in series and sequentially delay the input signal (digital signal) in units of one sample cycle. The filter coefficient is multiplied by each delayed signal by the multiplier 402, the multiplied signals are added together by the adder 403, and the addition result is output. When using a FIR filter, the wavelength dispersion compensation amount can be adjusted by changing the filter coefficient and the number of taps.

[0075] The FIR filter performs time domain equalization (TDE: Time Domain Equalizing) that equalizes the received signal in the time delay domain, whereas the same characteristics may be realized by frequency domain equalization (FDE: Frequency Domain Equalization) that equalizes in the frequency domain. By configuring the wavelength dispersion compensation unit by FDE, the circuit scale can be reduced compared to the FIR filter.

[0076] FIG. 16 is a configuration example when the wavelength dispersion compensation unit 231 is configured by FDE processing. The wavelength dispersion compensation unit 231 in FIG. 16 is a configuration example of overlap FDE, and includes an overlap addition unit 411, a fast Fourier transform unit 412, an inverse transfer function multiplication unit 413, an inverse fast Fourier transform unit 414, and an overlap removal unit 415.

[0077] The overlap addition section 411 overlaps a part of the preceding and succeeding signals with the input signal (digital signal), and then the fast Fourier transform section 412 converts the overlapped signal into a signal in the frequency domain by fast Fourier transform (FFT: Fast Fourier Transform). After the inverse transfer function multiplication section 413 multiplies the signal in the frequency domain by the inverse transfer function of the transmission line for equalization, the inverse fast Fourier transform section 414 converts it into a signal in the time domain by inverse fast Fourier transform (IFFT: Inverse Fast Fourier Transform). The overlap removal section 415 removes the overlap part from the signal restored in the time domain and outputs it. When using FDE, the wavelength dispersion compensation amount can be adjusted by changing the inverse transfer function. Note that the overlap addition section 411 and the overlap removal section 415 may be omitted.

[0078] The node control section 202 receives control information from the control device 100 and controls each part of the optical relay device 200 based on the received control information. The node control section 202 is an acquisition section that acquires received wavelength information, transmission wavelength information, and an optimal wavelength dispersion compensation amount from the parameter calculation section 130. The node control section 202 sets the frequency (wavelength) of the local light emission r1 for the received light source 240 based on the acquired received wavelength information, and sets the frequency of the transmission light r2 for the transmission light source 250 based on the acquired transmission wavelength information. The node control section 202 sets the wavelength dispersion compensation amount for the wavelength dispersion compensation section 231 based on the acquired optimal wavelength dispersion compensation amount.

[0079] FIG. 17 shows an operation example of the optical network system according to the present embodiment. As shown in FIG. 17, first, the control device 100 determines the wavelengths to be used by the optical relay device 200 (S101). The network control unit 120 determines the path of the path in the optical network 51, identifies the optical transmission paths and the optical relay devices 200 on the path of the path, and determines the wavelengths of the identified optical transmission paths, thereby determining the wavelengths before and after (before and after conversion) in each optical relay device 200, that is, the wavelengths of the optical signals transmitted and received by the optical relay device 200. The network control unit 120 outputs the received wavelength information and the transmitted wavelength information of the optical relay device 200 according to the determined wavelengths, and outputs the transmission path information (distance) of the optical transmission paths before and after the optical relay device 200. When a plurality of optical relay devices 200 are included in the path, the following processing is performed for each optical relay device.

[0080] Next, the control device 100 calculates the wavelength dispersion characteristics in the optical transmission paths before and after the optical relay device 200 (S102). The parameter calculation unit 130 calculates the wavelength dispersion characteristics in the optical transmission paths before and after the optical relay device 200 based on the received wavelength information and the transmitted wavelength information acquired from the network control unit 120. The parameter calculation unit 130 determines the wavelength dispersion characteristics of the optical transmission path on the front side of the optical relay device 200 based on the wavelength of the received wavelength information, and determines the wavelength dispersion characteristics of the optical transmission path on the rear side of the optical relay device 200 based on the wavelength of the transmitted wavelength information. When the transmission information includes the structure and type of the optical fiber and the transmission characteristics, the wavelength dispersion characteristics may be determined based on these information.

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

[0082] Next, the control device 100 determines the optimal wavelength dispersion compensation amount in the optical relay device 200 (S103). The parameter calculation unit 130 determines the optimal wavelength dispersion compensation amount in the optical relay device 200 based on the wavelength dispersion characteristics of the optical transmission paths before and after the optical relay device 200 and the transmission path information (distance) of the optical transmission paths before and after. The parameter calculation unit 130 obtains the wavelength dispersion amount accumulated in the front-side (reception side) optical transmission path, obtains the wavelength dispersion amount accumulated in the rear-side (transmission side) optical transmission path, and determines the optimal wavelength dispersion amount based on the front-side wavelength dispersion amount and the rear-side wavelength dispersion amount. In particular, the optimal wavelength dispersion amount is determined based on the wavelength dispersion amount accumulated between the transmission terminal device 30 and the optical relay device 200 and the wavelength dispersion amount accumulated between the optical relay device and the reception terminal device. For example, the parameter calculation unit 130 obtains the wavelength dispersion amount accumulated in the front-side optical transmission path based on the wavelength dispersion characteristics and the transmission path information (distance) of the front-side optical transmission path of the optical relay device 200, and obtains the wavelength dispersion amount accumulated in the rear-side optical transmission path based on the wavelength dispersion characteristics and the transmission path information (distance) of the rear-side optical transmission path of the optical relay device 200. In this example, the wavelength dispersion compensation amount is determined based on the wavelength dispersion characteristics and the transmission path information. However, since the wavelength dispersion characteristics correspond to the wavelength information, the wavelength dispersion compensation amount may be determined based on the wavelength information and the transmission path information. That is, the wavelength dispersion compensation amounts in a plurality of optical relay devices constituting the path may be determined based on the wavelength information and the transmission path information in the path.

[0083] Next, the control device 100 notifies the optical relay device 200 of the wavelength information of the determined wavelength and the optimal wavelength dispersion compensation amount (S104). The parameter calculation unit 130 notifies the optical relay device 200 of the reception wavelength information and the transmission wavelength information determined in S101 and the optimal wavelength dispersion compensation amount determined in S103.

[0084] Next, the optical relay device 200 sets the wavelength of the wavelength information notified from the control device 100 and the optimal wavelength dispersion compensation amount (S105). 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, and sets the acquired optimal wavelength dispersion compensation amount to the wavelength dispersion compensation unit 231.

[0085] Next, the optical relay device 200 performs wavelength conversion and chromatic dispersion compensation (S106). The received light source 240 generates local light emission r1 of a set wavelength (frequency), and the transmission light source 250 generates transmission light r2 of a set wavelength, so that wavelength conversion is performed in the optical transceiver 201. Also, the chromatic dispersion compensation unit 231 performs chromatic dispersion compensation processing based on a set compensation amount by digital signal processing.

[0086] FIGS. 18A and 18B show specific examples of chromatic dispersion compensation by the control method in the present embodiment. In the present embodiment, the compensation amount for canceling chromatic dispersion at the receiving end is set as the optimal chromatic dispersion compensation amount in the optical relay device. That is, the optimal chromatic dispersion compensation amount in this example is the compensation amount based on the chromatic dispersion amount at the receiving end, and is the compensation amount obtained on the condition that the chromatic dispersion amount at the receiving end is smaller than a predetermined value.

[0087] As shown in FIG. 18A, in this example, one optical relay device 200 is arranged on the path between the transmitting end station device 30 and the receiving end station device. The transmitting end station device 30 and the optical relay device 200 are connected via an optical transmission line 3a (first optical transmission line), and the optical relay device 200 and the receiving end station device 40 are connected via an optical transmission line 3b (second optical transmission line). For example, the distance L1 of the optical transmission line 3a and the distance L2 of the optical transmission line 3b are different, and the distance L2 of the optical transmission line 3b is longer than the distance L1 of the optical transmission line 3a, but they may be the same distance. An optical signal with a wavelength λ1 in the C band is transmitted on the optical transmission line 3a, and an optical signal with a wavelength λ2 in the C band is transmitted on the optical transmission line 3b. That is, the optical relay device 200 converts the received optical signal with a wavelength λ1 into an optical signal with a wavelength λ2 and transmits the converted optical signal with a wavelength λ2.

[0088] As shown in Fig. 18B, in the first half of the optical transmission path 3a, since the wavelength of the optical signal is λ1, the control device 100 determines the slope DS1 (for example, 20 ps / nm / km) of the wavelength dispersion amount in the optical transmission path 3a according to the wavelength λ1 (C band). Using the slope DS1 of the wavelength dispersion amount and the distance L1 of the optical transmission path 3a, the control device 100 makes the wavelength dispersion at the time of transmission in the transmitting terminal device 30 zero, and obtains the wavelength dispersion amount M1 (= DS1 × L1) accumulated in the optical transmission path 3a from the transmitting terminal device 30 to the optical relay device 200.

[0089] Also, in the second half of the optical transmission path 3b, since the wavelength of the optical signal is λ2, the control device 100 determines the slope DS1 of the wavelength dispersion amount in the optical transmission path 3b according to the wavelength λ2 (C band). In this example, since the wavelengths λ1 and λ2 are wavelengths in the same C band, the slope of the wavelength dispersion amount in the optical transmission path 3a and the slope of the wavelength dispersion amount in the optical transmission path 3b are approximately equal. Using the slope DS1 of the wavelength dispersion amount and the distance L2 of the optical transmission path 3b, the control device 100 obtains the wavelength dispersion amount M2 (= DS1 × L2) accumulated in the optical transmission path 3b from the optical relay device 200 to the receiving terminal device 40 on the condition that the wavelength dispersion at the time of reception in the receiving terminal device 40 becomes zero. Note that it may be on the condition that the wavelength dispersion is within a predetermined range in the receiving terminal device 40. The control device 100 sets the total value of the obtained wavelength dispersion amounts M1 and M2 as the optimum wavelength dispersion compensation amount M0 (= M1 + M2) in the optical relay device 200.

[0090] Figs. 19A and 19B show other specific examples of wavelength dispersion compensation by the control method in the present embodiment. As shown in Fig. 19A, the configuration of each device and the optical transmission path is the same as that in Fig. 18A. In this example, an optical signal with a wavelength λ1 in the C band is transmitted in the optical transmission path 3a, and an optical signal with a wavelength λ3 in the L band is transmitted in the optical transmission path 3b.

[0091] As shown in Fig. 19B, the wavelength dispersion amount in the first half of the optical transmission path 3a is the same as that in Fig. 18B. Based on the slope DS1 of the wavelength dispersion amount corresponding to the wavelength λ1 and the distance L1 of the optical transmission path 3a, the control device 100 obtains the wavelength dispersion amount M1 (= DS1 × L1) accumulated in the optical transmission path 3a.

[0092] Further, in the latter half optical transmission path 3b, since the wavelength of the optical signal is λ3, the control device 100 determines the slope DS2 (e.g., 25 ps / nm / km) of the wavelength dispersion amount in the optical transmission path 3b according to the wavelength λ3 (L band). In this example, since the wavelength λ1 is a wavelength in the C band and the wavelength λ3 is a wavelength in the L band, the slope of the wavelength dispersion amount in the optical transmission path 3b is larger than the slope of the wavelength dispersion amount in the optical transmission path 3a. The control device 100 uses the slope DS2 of the wavelength dispersion amount and the distance L2 of the optical transmission path 3b to obtain the wavelength dispersion amount M3 (=DS2×L2) accumulated in the optical transmission path 3b from the optical relay device 200 to the receiving end station device 40 on the condition that the wavelength dispersion at the time of reception in the receiving end station device 40 becomes zero. The control device 100 sets the total value of the obtained wavelength dispersion amounts M1 and M3 as the optimum wavelength dispersion compensation amount M0 (=M1 + M3) in the optical relay device 200.

[0093] As described above, in the present embodiment, in an optical relay device that performs wavelength conversion in channel units, an analog signal output from an optical reception front end is converted into a digital signal by an ADC, and after digital signal processing, it is converted back into an analog signal by a DAC and relayed back to the optical transmission front end. At this time, in the digital signal processing unit, wavelength dispersion distortion generated in the optical fiber transmission path is compensated according to the line length of the network path (transmission line).

[0094] Specifically, in the control device, an optimum compensation amount is obtained so that the wavelength dispersion is minimized at the receiving end, and wavelength dispersion compensation is performed in the optical relay device with the obtained optimum compensation amount. Thereby, the distortion of the optical signal due to wavelength dispersion can be minimized at the receiving end. Also, since the wavelength dispersion distortion is canceled at the receiving end, power reduction of the wavelength dispersion compensation circuit becomes possible. Furthermore, by setting an optimum compensation amount according to the wavelength, wavelength dispersion can be appropriately compensated even when performing mutual wavelength conversion between the C band and the L band.

[0095] (Embodiment 2) Next, Embodiment 2 will be described with reference to the drawings. In this embodiment, the configuration and basic operation of the optical network system are the same as those in Embodiment 1.

[0096] Figures 20A and 20B show specific examples of wavelength dispersion compensation by the control method in the present embodiment. In the present embodiment, the optimal wavelength dispersion compensation amount in the optical relay device is mainly focused on suppressing non-linear distortion (SPM) throughout the transmission line. As the wavelength dispersion amount increases, the ratio of the peak value to the average power of the signal waveform (PAPR: Peak-to-Average Power Ratio) increases, and the influence of the non-linear effect becomes greater. Therefore, it is possible to suppress the non-linear effect by setting the wavelength dispersion compensation amount so that the transmission section where the peak value of the signal amplitude becomes large is minimized. For example, by performing wavelength dispersion compensation with a compensation amount that makes the wavelength dispersion zero at the center of the latter half of the transmission line, the influence of the non-linear effect can be suppressed to a smaller extent compared to Embodiment 1 shown in FIGS. 18A and 18B. That is, the optimal wavelength dispersion compensation amount in this example is a compensation amount based on the wavelength dispersion amount in a predetermined range including the center in the optical transmission line from the optical relay device to the receiving end station device, and is a compensation amount obtained on the condition that the wavelength dispersion amount in a predetermined range including the center in the optical transmission line is smaller than a predetermined value. Note that the predetermined range, which is a condition for obtaining the optimal wavelength dispersion compensation amount, is not limited to the range including the center of the optical transmission line. For example, the range on the first half side of the optical transmission line may be set as the predetermined range, or the range on the latter half side of the optical transmission line may be set as the predetermined range. That is, a compensation amount that can suppress the wavelength dispersion amount in a predetermined range determined in advance of the optical transmission line to be smaller than a predetermined value may be used as the optimal wavelength dispersion compensation amount. In other words, the optimal wavelength dispersion compensation amount is a compensation amount based on the absolute value of the wavelength dispersion amount from the optical relay device to the receiving end station device, and is a compensation amount obtained on the condition that the absolute value of the wavelength dispersion amount at each point from the optical relay device to the receiving end station device is smaller than a predetermined value.

[0097] As shown in Fig. 20A, the configuration of each device, optical transmission line, and wavelength is the same as that in Fig. 18A. As shown in Fig. 20B, the amount of wavelength dispersion in the first half of the optical transmission line 3a is the same as that in Fig. 18B. The control device 100 obtains the amount of wavelength dispersion M1 (= DS1 × L1) accumulated in the optical transmission line 3a based on the slope DS1 of the amount of wavelength dispersion corresponding to the wavelength λ1 and the distance L1 of the optical transmission line 3a.

[0098] Also, in the second half of the optical transmission line 3b, since the wavelength of the optical signal is λ2, the control device 100 determines the slope DS1 of the amount of wavelength dispersion in the optical transmission line 3b according to the wavelength λ2 (C band). The control device 100 uses the slope DS1 of the amount of wavelength dispersion and the distance L2 of the optical transmission line 3b, and on the condition that the wavelength dispersion at half the distance L2 / 2 of the optical transmission line 3b becomes zero, obtains the amount of wavelength dispersion M4 (= DS1 × L2 / 2) accumulated from the optical relay device 200 to the center of the optical transmission line 3b. Note that it may be on the condition that the wavelength dispersion is within a predetermined range near the center of the second half of the optical transmission line 3b, or on the condition that the absolute value of the wavelength dispersion at each point in the entire second half of the optical transmission line 3b is within a predetermined range. The control device 100 sets the total value of the obtained amounts of wavelength dispersion M1 and M4 as the optimal wavelength dispersion compensation amount M0 (= M1 + M4) in the optical relay device 200.

[0099] Figs. 21A and 21B show another specific example of wavelength dispersion compensation by the control method in the present embodiment. As shown in Fig. 21A, the configuration of each device, optical transmission line, and wavelength is the same as that in Fig. 19A. As shown in Fig. 21B, the amount of wavelength dispersion in the first half of the optical transmission line 3a is the same as that in Fig. 19B. The control device 100 obtains the amount of wavelength dispersion M1 (= DS1 × L1) accumulated in the optical transmission line 3a based on the slope DS1 of the amount of wavelength dispersion corresponding to the wavelength λ1 and the distance L1 of the optical transmission line 3a.

[0100] In the latter half of the optical transmission path 3b, since the wavelength of the optical signal is λ3, the control device 100 determines the slope DS2 of the wavelength dispersion amount in the optical transmission path 3b according to the wavelength λ3 (L band). Using the slope DS2 of the wavelength dispersion amount and the distance L2 of the optical transmission path 3b, the control device 100 obtains the wavelength dispersion amount M5 (= DS2 × L2 / 2) accumulated from the optical relay device 200 to the center of the optical transmission path 3b on the condition that the wavelength dispersion at half the distance L2 / 2 of the optical transmission path 3b is zero. The control device 100 sets the total value of the obtained wavelength dispersion amounts M1 and M5 as the optimal wavelength dispersion compensation amount M0 (= M1 + M5) in the optical relay device 200.

[0101] As described above, in the present embodiment, in the optical network system of Embodiment 1, the compensation amount for suppressing the non-linearity most in the entire transmission path is used as the optimal wavelength dispersion compensation amount to compensate for the wavelength dispersion. Specifically, in the control device, an optimal compensation amount is obtained such that the absolute value of the wavelength dispersion amount becomes small in the latter half of the transmission path. For example, the wavelength dispersion amount becomes zero at the center of the latter half of the transmission path, and wavelength dispersion compensation is performed by the optical relay device with the obtained optimal compensation amount. As a result, even if wavelength dispersion distortion remains at the receiving end, it is possible to minimize the non-linear distortion that is difficult to compensate by signal processing when viewed from the entire transmission path. Therefore, the signal quality can be maximized.

[0102] (Embodiment 3) Next, Embodiment 3 will be described with reference to the drawings.

[0103] FIG. 22 shows a configuration example of each device in the optical network system according to the present embodiment. As shown in FIG. 22, the configuration of the control device 100 according to the present embodiment is the same as that of Embodiments 1 and 2.

[0104] The optical relay device 200 according to the present embodiment includes a phase conjugate unit 232 in addition to the wavelength dispersion compensation unit 231 in the digital signal processing unit 230 of the optical transceiver 201. Other configurations of the optical relay device 200 are the same as those of Embodiments 1 and 2.

[0105] The phase conjugation unit 232 performs phase conjugation processing on the input digital signal SD1. Similar to Consideration Example 3, the phase conjugation unit 232 performs phase conjugation processing to generate a signal with a wavelength dispersion whose sign is inverted from the wavelength dispersion accumulated in the first half of the optical transmission line. That is, a signal equivalent to that obtained by performing wavelength dispersion compensation twice that of the wavelength dispersion accumulated in the first half of the optical transmission line is generated. The wavelength dispersion compensation unit 231 further performs wavelength dispersion processing on the signal phase-conjugated by the phase conjugation unit 232.

[0106] Specifically, the phase conjugation unit 232 obtains the complex conjugate of the input digital signal SD1. That is, as in the following formula (1), for the I X signal, Q X signal, I Y signal, Q Y signal, the sign of Qch is inverted. Ich and Qch may be swapped.

Equation

[0107] FIG. 23 shows an operation example of the optical network system according to the present embodiment. As shown in FIG. 23, first, similar to Embodiments 1 and 2, the control device 100 determines the wavelengths used in the optical relay device 200 (S201), and calculates the wavelength dispersion characteristics in the optical transmission lines before and after the optical relay device 200 (S202).

[0108] Next, the control device 100 determines the additional wavelength dispersion compensation amount (additional wavelength dispersion compensation amount) in the optical relay device 200 (S203). The additional wavelength dispersion compensation amount is the compensation amount to be further compensated by the wavelength dispersion processing of the wavelength dispersion compensation unit 231 in addition to the wavelength dispersion compensation by the phase conjugation processing of the phase conjugation unit 232 in the optical relay device 200. That is, in the present embodiment, the additional wavelength dispersion compensation amount is determined based on the wavelength dispersion compensation amount by the phase conjugation processing.

[0109] That is, similar to Embodiments 1 and 2, the parameter calculation unit 130 determines the optimal wavelength dispersion compensation amount in the optical relay device 200 based on the wavelength dispersion characteristics of the optical transmission paths before and after the optical relay device 200 and the transmission path information (distance) of the optical transmission paths before and after. Further, the parameter calculation unit 130 subtracts the wavelength dispersion compensation amount (phase conjugate compensation amount) compensated by phase conjugation in the optical relay device 200 from the obtained optimal wavelength dispersion compensation amount to determine the wavelength dispersion compensation amount of the additional part in the optical relay device 200. The phase conjugate compensation amount is twice the amount of wavelength dispersion accumulated in the front-side (reception side) optical transmission path. That is, based on the amount of wavelength dispersion accumulated in the front-side optical transmission path, the wavelength dispersion compensation amount by the phase conjugate process is obtained.

[0110] Next, the control device 100 notifies the optical relay device 200 of the wavelength information of the determined wavelength and the additional wavelength dispersion compensation amount (S204). The parameter calculation unit 130 notifies the optical relay device 200 of the received wavelength information, the transmitted wavelength information, and the additional wavelength dispersion compensation amount.

[0111] Next, the optical relay device 200 sets the wavelength of the wavelength information notified from the control device 100 and the additional wavelength dispersion compensation amount (S205). The node control unit 202 sets the wavelength of the acquired received wavelength information to the reception light source 240, sets the wavelength of the acquired transmitted wavelength information to the transmission light source 250, and sets the acquired additional wavelength dispersion compensation amount to the wavelength dispersion compensation unit 231.

[0112] Next, the optical relay device 200 performs wavelength conversion, phase conjugation, and wavelength dispersion compensation (S206). Based on the wavelengths of the set reception light source 240 and the transmission light source 250, wavelength conversion is performed in the optical transceiver 201. Also, the phase conjugate unit 232 performs a phase conjugate process by phase conjugation, and the wavelength dispersion compensation unit 231 performs a wavelength dispersion compensation process on the signal after the phase conjugate process based on the set compensation amount.

[0113] Figures 24A and 24B show specific examples of wavelength dispersion compensation by the control method in this embodiment. In Figure 24A, the basic configuration of each device, the optical transmission line, and the wavelength is the same as in Figure 21A. In this example, this embodiment is applied to the configuration of Figure 21A of Embodiment 2. Note that this embodiment may also be applied to Embodiment 1.

[0114] As shown in Figure 24B, the control device 100, similar to Embodiment 2, obtains the optimal wavelength dispersion compensation amount M0 to be compensated by the optical relay device 200 from the wavelength dispersion amount M1 accumulated in the optical transmission line 3a and the wavelength dispersion amount M5 accumulated up to the center of the optical transmission line 3b. Further, the control device 100 obtains the phase conjugate compensation amount M7 (= M1 × 2) compensated by phase conjugation from the wavelength dispersion amount M1 accumulated in the optical transmission line 3a. The control device 100 sets, as the additional wavelength dispersion compensation amount M8 (= M0 - M7), the compensation amount obtained by subtracting the phase conjugate compensation amount M7 from the optimal wavelength dispersion compensation amount M0 in the optical relay device 200.

[0115] As described above, in this embodiment, in the digital signal processing unit of the optical relay device in Embodiments 1 and 2, wavelength dispersion compensation is performed by phase conjugation, and further, wavelength dispersion compensation is performed by an additional wavelength dispersion compensation unit. The control device obtains the additional wavelength dispersion compensation amount in consideration of the compensation amount by phase conjugation. As described above, since phase conjugation can be implemented by simple operations, the circuit scale can be reduced by combining an optical phase conjugate circuit and a wavelength dispersion compensation circuit.

[0116] (Embodiment 4) Next, Embodiment 4 will be described with reference to the drawings.

[0117] Figure 25 shows a configuration example of each device in the optical network system according to this embodiment. As shown in Figure 25, the configuration of the optical relay device 200 according to this embodiment is the same as in Embodiment 3. Note that an optical relay device similar to those in Embodiments 1 and 2 may also be used.

[0118] In this embodiment, the receiving end station device 40 is provided with a monitor unit 41. The monitor unit 41 monitors the signal quality of the optical signal received from the optical transmission line. The monitor unit 41 notifies the control device 100 of signal quality information indicating the monitored signal quality. For example, the signal quality to be monitored is BER (Bit Error Rate), Q value, EVM (Error Vector Magnitude), etc., and the signal quality information includes at least any one of these pieces of information.

[0119] The control device 100 according to this embodiment includes a parameter variable unit 140 instead of the parameter calculation unit 130. Other configurations in the control device 100 are the same as those in Embodiments 1 to 3. Note that the parameter calculation unit 130 may have the function of the parameter variable unit 140.

[0120] Similar to the parameter calculation unit 130 in Embodiments 1 to 3, the parameter variable unit 140 calculates the optimal wavelength dispersion compensation amount in the optical relay device 200 and the wavelength dispersion compensation amount of the additional unit, and further acquires signal quality information from the receiving end station device 40, and adjusts (varies) the calculated wavelength dispersion compensation amount based on the acquired signal quality information. It can also be said that the parameter variable unit 140 determines the wavelength dispersion compensation amount of the optical relay device 200 based on the signal quality information of the receiving end station device 40.

[0121] FIG. 26 shows an operation example of the optical network system according to this embodiment. As shown in FIG. 26, first, similar to Embodiment 3, the control device 100 (parameter variable unit 140) calculates the wavelength dispersion compensation amount, and the optical relay device 200 performs wavelength dispersion compensation with the calculated wavelength dispersion compensation amount (S201 to S206). In this example, similar to Embodiment 3, the additional wavelength dispersion compensation amount is obtained and compensated, but wavelength dispersion compensation may be performed with the optimal wavelength dispersion compensation amount as in Embodiments 1 and 2.

[0122] Next, the control device 100 acquires the signal quality information of the receiving end (S207). The monitor unit 41 of the receiving end station device 40 monitors, for example, periodically, the signal quality of the received optical signal, and notifies the control device 100 of the signal quality information indicating the monitored result. The network control unit 120 acquires the signal quality information notified from the monitor unit 41.

[0123] Next, the control device 100 adjusts the wavelength dispersion compensation amount set in the optical relay device 200 (S208). The parameter variable unit 140 adjusts the wavelength dispersion compensation amount that has already been notified and set to the optical relay device 200 based on the signal quality information acquired from the receiving end station device 40. After that, in S204 and later, the control device 100 notifies the optical relay device 200 of the adjusted wavelength dispersion compensation amount, and the optical relay device 200 performs wavelength dispersion compensation with the adjusted compensation amount. For example, the adjustment of the wavelength dispersion compensation amount is repeated until the signal quality at the receiving end station device 40 is within a predetermined range or until the signal quality becomes the best.

[0124] FIGS. 27A and 27B show specific examples of wavelength dispersion compensation by the control method in the present embodiment. In FIG. 27A, the basic configuration of each device, the optical transmission line, and the wavelength is the same as that in FIG. 24A. In this example, the present embodiment is applied to the configuration of FIG. 24A in Embodiment 3. Note that the present embodiment may also be applied to Embodiments 1 and 2.

[0125] As shown in FIG. 27B, the control device 100 obtains the additional wavelength dispersion compensation amount M8 from the optimal wavelength dispersion compensation amount M0 and sets it in the optical relay device 200 in the same manner as in Embodiment 3. The optical relay device 200 compensates the phase conjugate compensation amount M7 by the phase conjugate unit 232 and compensates the additional wavelength dispersion compensation amount M8 by the wavelength dispersion compensation unit 231.

[0126] The receiving end office device 40 receives the optical signal compensated by the optical relay device 200 and monitors the quality of the received optical signal. The control device 100 adaptively adjusts the wavelength dispersion compensation amount so that the signal quality is maximized based on the signal quality information indicating the signal quality monitored by the receiving end office device 40. That is, according to the signal quality of the receiving end office device 40, the set wavelength dispersion compensation amount (in this example, the additional wavelength dispersion compensation amount) is adjusted, and the adjusted wavelength dispersion compensation amount is reset to the optical relay device 200. Only the change amount of the wavelength dispersion compensation amount may be set to the optical relay device 200. For example, the wavelength dispersion compensation amount may be changed to the positive side or the negative side in a predetermined step, and the wavelength dispersion compensation amount at which the signal quality becomes the best may be obtained. Note that optimization is possible even during operation by slowly and slightly adjusting the wavelength dispersion compensation amount.

[0127] As described above, in the present embodiment, in the optical network systems of Embodiments 1 to 3, based on the signal quality of the optical signal at the receiving end, the wavelength dispersion compensation amount in the optical relay device is made variable and feedback control is performed. Thereby, the wavelength dispersion amount can be optimized so that the signal quality is maximized in the actual transmission line.

[0128] (Other Embodiments) An example in which the wavelength dispersion compensation control method described in Embodiments 1 to 4 is applied to a plurality of optical relay devices on the path will be described with reference to FIGS. 28A and 28B to FIGS. 30A and 30B.

[0129] In the example of FIGS. 28A and 28B, as shown in FIG. 28A, an optical relay device 200a (first optical relay device) and an optical relay device 200b (second optical relay device) are arranged on the path of the path between the transmitting end office device 30 and the receiving end office device 40. The between the transmitting end office device 30 and the optical relay device 200a is connected via an optical transmission line 3a (first optical transmission line), the between the optical relay device 200a and the optical relay device 200b is connected via an optical transmission line 3b (second optical transmission line), and the between the optical relay device 200b and the receiving end office device 40 is connected via an optical transmission line 3c (third optical transmission line). For example, the distance L1 of the optical transmission line 3a, the distance L2 of the optical transmission line 3b, and the distance L3 of the optical transmission line 3c are different from each other, but the same DistanceThey may be separated. In the optical transmission path 3a, an optical signal with a wavelength λ1 in the C band is transmitted. In the optical transmission path 3b, an optical signal with a wavelength λ2 in the C band is transmitted. In the optical transmission path 3c, an optical signal with a wavelength λ3 in the L band is transmitted.

[0130] The optical relay device 200a has only the phase conjugate part 232 in the digital signal processing part 230 among the configurations of the optical relay device shown in the third embodiment, and is, for example, an optical relay device similar to the third study example. The optical relay device 200b has the configuration of the optical relay device in the first and second embodiments, and has only the wavelength dispersion compensation part 231 in the digital signal processing part 230. Note that the optical relay device 200b may be used as the optical relay device in the third embodiment.

[0131] As shown in FIG. 28B, since the optical relay device 200a only performs wavelength compensation by phase conjugation, the amount of wavelength dispersion M11 accumulated in the optical transmission path 3a is determined by the slope DS1 of the wavelength dispersion amount corresponding to the wavelength λ1 (C band) and the distance L1 of the optical transmission path 3a, and the phase conjugate compensation amount in the optical relay device 200a is M10 (= M11 × 2). That is, the amount of wavelength dispersion after compensation in the optical relay device 200a is -M11. Note that it is not necessary to set the wavelength dispersion compensation amount for the optical relay device 200a.

[0132] Considering the amount of wavelength dispersion compensated in the optical relay device 200a, the wavelength dispersion compensation amount in the optical relay device 200b is determined. That is, in the optical relay device 200b, using the slope DS1 of the wavelength dispersion amount corresponding to the wavelength λ2 (C band) and the distance L2 of the optical transmission path 3b, the amount of wavelength dispersion accumulated in the optical transmission path 3b from the optical relay device 200a to the optical relay device 200b is obtained as the amount of wavelength dispersion -M11 after compensation in the optical relay device 200a. In this example, the amount of wavelength dispersion is canceled out to zero in the optical relay device 200b.

[0133] In the optical relay device 200b, the fact that the accumulated wavelength dispersion amount is zero means that when relaying is performed only by optical phase conjugation, there is substantially no strain relaxation effect on wavelength dispersion, and there is no waveform distortion relaxation effect in the optical transmission line 3c. Therefore, in this example, similar to the second embodiment, wavelength dispersion is compensated so that the wavelength dispersion amount becomes zero at the center of the optical transmission line 3c. That is, the control device 100 uses the slope DS2 of the wavelength dispersion amount corresponding to the wavelength λ3 (L band) and the distance L3 of the optical transmission line 3c, and on the condition that the wavelength dispersion at half the distance L3 / 2 of the optical transmission line 3c becomes zero, obtains the wavelength dispersion amount M12 (= DS2 × L3 / 2) accumulated from the optical relay device 200b to the center of the optical transmission line 3c. Since the wavelength dispersion amount in the optical relay device 200b is zero, the obtained wavelength dispersion amount M12 is set in the optical relay device 200b as the optimal wavelength dispersion compensation amount. Note that, similar to the first embodiment, the wavelength dispersion compensation amount may be obtained on the condition that the wavelength dispersion amount at the receiving end station device 40 becomes zero.

[0134] In the examples of FIGS. 29A and 29B, as shown in FIG. 29A, optical relay devices 200c and 200d are arranged on the path of the pass between the transmitting end station device 30 and the receiving end station device 40. Similar to FIG. 28A, the distance L1 of the optical transmission line 3a between the transmitting end station device 30 and the optical relay device 200c, the distance L2 of the optical transmission line 3b between the optical relay device 200c and the optical relay device 200d, and the distance L3 of the optical transmission line 3c between the optical relay device 200d and the receiving end station device 40 are different from each other, but they Distance may be the same distance. An optical signal with a wavelength λ1 in the C band is transmitted on the optical transmission line 3a, an optical signal with a wavelength λ3 in the L band is transmitted on the optical transmission line 3b, and an optical signal with a wavelength λ4 in the L band is transmitted on the optical transmission line 3c. The optical relay devices 200c and 200d are optical relay devices in the third embodiment, and the digital signal processing unit 230 has a wavelength dispersion compensation unit 231 and a phase conjugation unit 232. Note that the optical relay devices 200c and 200d may be optical relay devices in the first and second embodiments.

[0135] As shown in Fig. 29B, in the setting of the optical relay device 200c, the control device 100 obtains the wavelength dispersion amount M21 accumulated in the optical transmission path 3a from the slope DS1 of the wavelength dispersion amount corresponding to the wavelength λ1 (C band) and the distance L1 of the optical transmission path 3a, and obtains the wavelength dispersion amount M22 accumulated up to the center of the optical transmission path 3b from the slope DS2 of the wavelength dispersion amount corresponding to the wavelength λ3 (L band) and half the distance L2 / 2 of the optical transmission path 3b, and obtains the optimum wavelength dispersion compensation amount M20 (=M21 + M22) to be compensated by the optical relay device 200c. The control device 100 sets the optical relay device 200c with the additional wavelength dispersion compensation amount M24 (=M20 - M23) in the optical relay device 200c from the optimum wavelength dispersion amount M20 and the phase conjugate compensation amount M23 (=M21×2) compensated by phase conjugation. In this example, since the phase conjugate compensation amount M23 is larger than the optimum wavelength dispersion compensation amount M20, the additional wavelength dispersion compensation amount M24 is compensation in the positive direction on the vertical axis (axis indicating the wavelength dispersion amount) of the graph in Fig. 29B. For example, when the wavelength dispersion compensation amount for compensating the accumulated wavelength dispersion amount M is M, the direction in which the compensation amount becomes smaller than M is the positive direction on the vertical axis of the graph, and the direction in which the compensation amount becomes larger than M is the negative direction on the vertical axis of the graph. Note that the wavelength dispersion compensation amount may be obtained on the condition that the wavelength dispersion amount in the optical relay device 200d becomes zero.

[0136] Also, in the setting of the optical relay device 200d, the control device 100 uses the slope DS2 of the wavelength dispersion amount corresponding to the wavelength λ3 (L band) and the distance L2 of the optical transmission path 3b to obtain the wavelength dispersion amount -M22 after compensation in the optical relay device 200c, and determines the wavelength dispersion amount M31 accumulated in the optical transmission path 3b from the optical relay device 200c to the optical relay device 200d. The control device 100 uses the slope DS2 of the wavelength dispersion amount corresponding to the wavelength λ4 (L band) and half of the distance L3 / 2 of the optical transmission path 3c to obtain the wavelength dispersion amount M32 accumulated up to the center of the optical transmission path 3c, and determines the optimum wavelength dispersion compensation amount M30 (=M31 + M32) to be compensated by the optical relay device 200d. The control device 100 sets the additional wavelength dispersion compensation amount M34 (=M30 - M33) in the optical relay device 200d from the optimum wavelength dispersion amount M30 and the phase conjugate compensation amount M33 (=M31×2) compensated by phase conjugation. Note that the wavelength dispersion compensation amount may be obtained on the condition that the wavelength dispersion amount in the receiving end station device 40 becomes zero.

[0137] As shown in FIGS. 30A and 30B, in the example of FIG. 30A, similar to FIG. 29A, the optical relay devices 200c and 200d are arranged on the path between the transmitting end station device 30 and the receiving end station device 40. An optical signal with a wavelength λ1 in the C band is transmitted through the optical transmission path 3a, an optical signal with a wavelength λ2 in the C band is transmitted through the optical transmission path 3b, and an optical signal with a wavelength λ3 in the L band is transmitted through the optical transmission path 3c.

[0138] As shown in FIG. 30B, in the setting of the optical relay device 200c, the control device 100 obtains the wavelength dispersion amount M41 accumulated in the optical transmission path 3a from the slope DS1 of the wavelength dispersion amount corresponding to the wavelength λ1 (C band) and the distance L1 of the optical transmission path 3a, and obtains the wavelength dispersion amount M42 accumulated up to the center of the optical transmission path 3b from the slope DS1 of the wavelength dispersion amount corresponding to the wavelength λ2 (C band) and half of the distance L2 / 2 of the optical transmission path 3b, and determines the optimum wavelength dispersion compensation amount M40 (=M41 + M42) to be compensated by the optical relay device 200c. The control device 100 sets the additional wavelength dispersion compensation amount M44 (=M40 - M43) in the optical relay device 200c from the optimum wavelength dispersion compensation amount M40 and the phase conjugate compensation amount M43 (=M41×2) compensated by phase conjugation.

[0139] Also, in the setting of the optical relay device 200d, the control device 100 uses the slope DS1 of the wavelength dispersion amount corresponding to the wavelength λ2 (C band) and the distance L2 of the optical transmission line 3b to obtain the wavelength dispersion amount -M42 after compensation in the optical relay device 200c, that is, the wavelength dispersion amount M51 accumulated in the optical transmission line 3b from the optical relay device 200c to the optical relay device 200d. The control device 100 uses the slope DS2 of the wavelength dispersion amount corresponding to the wavelength λ3 (L band) and half of the distance L3 / 2 of the optical transmission line 3c to obtain the wavelength dispersion amount M52 accumulated up to the center of the optical transmission line 3c, and obtains the optimum wavelength dispersion compensation amount M50 (=M51 + M52) to be compensated by the optical relay device 200d. The control device 100 sets the additional wavelength dispersion compensation amount M54 (=M50 - M53) in the optical relay device 200d from the optimum wavelength dispersion compensation amount M50 and the phase conjugate compensation amount M53 (=M51×2) compensated by phase conjugation.

[0140] Also, in the digital signal processing unit of the optical relay device shown in Embodiments 1 to 4, not limited to wavelength dispersion compensation, other signal quality compensation processes may be performed. For example, as shown in FIGS. 31 and 32, a band compensation process for compensating for signal band degradation, a frequency offset compensation process for compensating for the frequency deviation of a light source (local light emission), etc. may be performed.

[0141] In the example of FIG. 31, in addition to the wavelength dispersion compensation unit 231, the digital signal processing unit 230 of the optical relay device 200 includes a spectrum monitor 233 and a band compensation unit 234. The spectrum monitor 233 monitors the spectrum of the digital signal SD1 after wavelength dispersion compensation. The band compensation unit 234 performs band compensation on the digital signal SD1 after wavelength dispersion compensation by increasing the signal level of the deteriorated band according to the band deterioration of the monitored spectrum. The band compensation unit 234 may be constituted by a digital filter such as a FIR filter. Thereby, it is possible to restore the narrowed signal band, such as the band deterioration accompanying the passage of the optical relay device provided with the optical filter and the band deterioration caused by the optical transceiver analog front-end unit, and suppress the deterioration of the signal quality. Of course, the wavelength dispersion compensation by the wavelength dispersion compensation unit 231 and the band compensation by the band compensation unit 234 may be collectively compensated by a single FIR filter or a frequency domain equalization filter (FDE).

[0142] In the example of FIG. 32, in addition to the wavelength dispersion compensation unit 231, the digital signal processing unit 230 of the optical relay device 200 includes a spectrum monitor 233 and an offset compensation unit 235. The spectrum monitor 233 monitors the spectrum of the digital signal SD1 after wavelength dispersion compensation. The offset compensation unit 235 performs frequency offset compensation on the digital signal SD1 after wavelength dispersion compensation by shifting the frequency so as to return the frequency shift according to the frequency offset (wavelength shift) of the monitored spectrum. The offset compensation unit 235 may be constituted by a digital frequency shifter. Thereby, it is possible to compensate the frequency offset of the light source accumulated by multi-stage wavelength conversion inside the optical relay device, and suppress the signal quality deterioration caused by the frequency offset even in multi-stage relay.

[0143] Note that the present disclosure is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit thereof.

[0144] Each configuration in the above-described embodiments is constituted by hardware or software, or both, and may be constituted by one piece of hardware or software, or may be constituted by a plurality of pieces of hardware or software. Each device (such as a control device) and each function (processing) may be realized by a computer 60 having a processor 61 such as a CPU (Central Processing Unit) and a memory 62 which is a storage device, as shown in FIG. 33. For example, a program for performing the method (such as a control method) in the embodiment may be stored in the memory 62, and each function may be realized by the processor 61 executing the program stored in the memory 62.

[0145] These programs, when loaded into a computer, include a set of instructions (or software code) for causing the computer to perform one or more functions described in the embodiment. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, a computer-readable medium or a tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD), or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disc, or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may be transmitted on a transient computer-readable medium or a communication medium. By way of example and not limitation, a transient computer-readable medium or a communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0146] Although the present disclosure has been described with reference to the embodiments above, the present disclosure is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure.

[0147] Some or all of the above embodiments may be described as follows in the appended claims, but are not limited thereto. (Appendix 1) An optical relay device constituting an optical network and a control device for controlling the optical relay device are provided. The control device management means for managing wavelength information of an optical signal transmitted and received by the optical relay device in a path of the optical network and transmission path information of an optical transmission path connected to the optical relay device; compensation control means for determining a wavelength dispersion compensation amount in the optical relay device based on the wavelength information and the transmission path information; and The optical relay device acquisition means for acquiring the determined wavelength dispersion compensation amount from the control device; wavelength dispersion compensation means for performing wavelength dispersion compensation processing on an electrical signal based on a received optical signal based on the acquired wavelength dispersion compensation amount An optical network system comprising. (Appendix 2) The compensation control means determines the wavelength dispersion compensation amount based on the wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device and the wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device. The optical network system according to Appendix 1. (Appendix 3) The compensation control means obtains the wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device based on the wavelength information and the transmission path information on the reception side of the optical relay device, and obtains the wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device based on the wavelength information and the transmission path information on the transmission side of the optical relay device. The optical network system according to Appendix 2. (Appendix 4) The compensation control means specifies the wavelength dispersion characteristics of the optical transmission path based on the wavelength information, and obtains the wavelength dispersion amount accumulated in the optical transmission path based on the wavelength dispersion characteristics and the distance included in the transmission path information. The optical network system according to Appendix 2 or 3. (Appendix 5) The compensation control means determines the wavelength dispersion compensation amount based on the amount of wavelength dispersion accumulated between the transmitting end station device and the optical relay device in the path. The optical network system according to any one of Appendices 2 to 4. (Appendix 6) The compensation control means determines the wavelength dispersion compensation amount based on the amount of wavelength dispersion accumulated between the optical relay device and the receiving end station device in the path. The optical network system according to any one of Appendices 2 to 5. (Appendix 7) The wavelength dispersion compensation amount is a compensation amount based on the amount of wavelength dispersion in the receiving end station device. The optical network system according to Appendix 6. (Appendix 8) The wavelength dispersion compensation amount is a compensation amount obtained on the condition that the amount of wavelength dispersion in the receiving end station device is smaller than a predetermined value. The optical network system according to Appendix 7. (Appendix 9) The wavelength dispersion compensation amount is a compensation amount based on the amount of wavelength dispersion within a predetermined range determined in advance in the optical transmission path from the optical relay device to the receiving end station device. The optical network system according to Appendix 6. (Appendix 10) The wavelength dispersion compensation amount is a compensation amount obtained on the condition that the amount of wavelength dispersion within the predetermined range is smaller than a predetermined value. The optical network system according to Appendix 9. (Appendix 11) The predetermined range is a range including the center of the optical transmission path. The optical network system according to Appendix 9 or 10. (Appendix 12) The wavelength dispersion compensation amount is a compensation amount based on the absolute value of the amount of wavelength dispersion at each point from the optical relay device to the receiving end station device. The optical network system according to Appendix 6. (Appendix 13) The wavelength dispersion compensation amount is a compensation amount obtained on the condition that the absolute value of the wavelength dispersion amount at each point from the optical relay device to the receiving end station device is smaller than a predetermined value. The optical network system according to Supplementary Note 12. (Supplementary Note 14) The compensation control means acquires signal quality information of an optical signal received at the receiving end station device, and determines the wavelength dispersion compensation amount based on the acquired signal quality information. The optical network system according to any one of Supplementary Notes 6 to 13. (Supplementary Note 15) The optical relay device further includes phase conjugation means for performing phase conjugation processing on an electrical signal based on the received optical signal. The compensation control means determines the wavelength dispersion compensation amount in the optical relay device based on the wavelength dispersion compensation amount by the phase conjugation processing. The optical network system according to any one of Supplementary Notes 1 to 14. (Supplementary Note 16) The compensation control means obtains the wavelength dispersion compensation amount by the phase conjugation processing based on the wavelength dispersion amount accumulated in the optical transmission path on the receiving side of the optical relay device. The optical network system according to Supplementary Note 15. (Supplementary Note 17) The compensation control means determines the wavelength dispersion compensation amounts in a plurality of the optical relay devices constituting the path based on the wavelength information and the transmission path information in the path. The optical network system according to any one of Supplementary Notes 1 to 16. (Supplementary Note 18) Management means for managing wavelength information of an optical signal transmitted and received by an optical relay device in a path of an optical network and transmission path information of an optical transmission path connected to the optical relay device; Compensation control means for determining a wavelength dispersion compensation amount in the optical relay device based on the wavelength information and the transmission path information; A control device comprising: (Supplementary Note 19) The compensation control means determines the wavelength dispersion compensation amount based on the amount of wavelength dispersion accumulated in the optical transmission line on the receiving side of the optical relay device and the amount of wavelength dispersion accumulated in the optical transmission line on the transmitting side of the optical relay device. The control device according to Supplementary Note 18. (Supplementary Note 20) An acquisition means for acquiring a wavelength dispersion compensation amount from the control device; Coherent optical reception front-end means for coherently detecting the received optical signal based on local light emission and outputting the coherently detected electrical signal; Wavelength dispersion compensation means for performing wavelength dispersion compensation processing on the electrical signal by digital signal processing based on the acquired wavelength dispersion compensation amount; Coherent optical transmission front-end means for coherently modulating the electrical signal subjected to the wavelength dispersion compensation processing based on the transmission light and transmitting the coherently modulated optical signal; An optical relay device comprising: (Supplementary Note 21) Further comprising phase conjugation means for performing phase conjugation processing on the electrical signal by digital signal processing; The optical relay device according to Supplementary Note 20. (Supplementary Note 22) Further comprising bandwidth compensation means for performing bandwidth compensation processing on the electrical signal by digital signal processing; The optical relay device according to Supplementary Note 20 or 21. (Supplementary Note 23) Further comprising offset compensation means for performing frequency offset compensation processing on the electrical signal by digital signal processing; The optical relay device according to any one of Supplementary Notes 20 to 22. (Supplementary Note 24) The acquisition means acquires received wavelength information which is the wavelength of the received optical signal and transmitted wavelength information which is the wavelength of the transmitted optical signal from the control device, sets the wavelength of the received wavelength information to the light source of the local light emission, and sets the wavelength of the transmitted wavelength information to the light source of the transmission light. The optical relay device according to any one of Supplementary Notes 20 to 23. (Supplementary Note 25) Manage the wavelength information of the optical signals transmitted and received by the optical relay device in the path of the optical network and the transmission path information of the optical transmission path connected to the optical relay device, Determine the amount of chromatic dispersion compensation in the optical relay device based on the wavelength information and the transmission path information, Control method. (Appendix 26) Determine the amount of chromatic dispersion compensation based on the amount of chromatic dispersion accumulated in the optical transmission path on the receiving side of the optical relay device and the amount of chromatic dispersion accumulated in the optical transmission path on the transmitting side of the optical relay device, The control method according to Appendix 25. (Appendix 27) Manage the wavelength information of the optical signals transmitted and received by the optical relay device in the path of the optical network and the transmission path information of the optical transmission path connected to the optical relay device, Determine the amount of chromatic dispersion compensation in the optical relay device based on the wavelength information and the transmission path information, A non-transitory computer-readable medium storing a control program for causing a computer to execute the process. (Appendix 28) Determine the amount of chromatic dispersion compensation based on the amount of chromatic dispersion accumulated in the optical transmission path on the receiving side of the optical relay device and the amount of chromatic dispersion accumulated in the optical transmission path on the transmitting side of the optical relay device, The non-transitory computer-readable medium according to Appendix 27.

Explanation of Signs

[0148] 1 Optical network system 2 Optical relay device 3 Optical transmission path 4, 5 Data center 6 IT service provider 7, 8 Event venue 10 Control device 11 Management department 12 Compensation control unit 20 Optical relay device 21 Coherent reception front-end unit 22 Chromatic dispersion compensation unit 23 Coherent transmission front-end unit 24 Acquisition Unit 30 Transmission End Office Device 40 Receiving End Office Device 41 Monitor Unit 50 Optical Network System 51 Optical Network 60 Computer 61 Processor 62 Memory 100 Control Device 110 Network Management Unit 120 Network Control Unit 130 Parameter Calculation Unit 140 Parameter Variable Unit 200 Optical Relay Device 201 Optical Transceiver 202 Node Control Unit 210 Coherent Receiver Front End Unit 220 Coherent Transmitter Front End Unit 230 Digital Signal Processing Unit 231 Chromatic Dispersion Compensation Unit 232 Phase Conjugation Unit 233 Spectrum Monitor 234 Bandwidth Compensation Unit 235 Offset Compensation Unit 240 Received Light Source 250 Transmitted Light Source 260 ADC 270 DAC 300 Optical Switch Unit 301 Demultiplexer 302 Multiplexer 303 Branch Insertion Unit 310 Transceiver Unit 311, 312, 313, 314 Optical Transceivers 401 Delay Unit 402 Multiplier 403 Adder 411 Overlap Add Unit 412 Fast Fourier Transform Unit 413 Inverse Transfer Function Multiplication Unit 414 Inverse Fast Fourier Transform Unit 415 Overlap Removal Unit

Claims

1. An optical relay device that constitutes an optical network, and a control device that controls the optical relay device, The control device is Management means for managing wavelength information of an optical signal transmitted and received by the optical relay device in a path of the optical network and transmission path information of an optical transmission path connected to the optical relay device; Compensation control means for determining a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information; Comprising The optical relay device is Acquisition means for acquiring the determined wavelength dispersion compensation amount from the control device; Wavelength dispersion compensation means for performing wavelength dispersion compensation processing on an electrical signal based on a received optical signal based on the acquired wavelength dispersion compensation amount Comprising The compensation control means obtains a wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device based on the wavelength information and the transmission path information on the reception side of the optical relay device, and based on the wavelength information and the transmission path information on the transmission side of the optical relay device, obtains a wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device, and determines the wavelength dispersion compensation amount based on the wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device and the wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device. Optical network system.

2. The compensation control means specifies the wavelength dispersion characteristics of the optical transmission path based on the wavelength information, and obtains the wavelength dispersion amount accumulated in the optical transmission path based on the wavelength dispersion characteristics and the distance included in the transmission path information. The optical network system according to claim 1.

3. The compensation control means determines the wavelength dispersion compensation amount based on the wavelength dispersion amount accumulated between the transmission terminal device in the path and the optical relay device. The optical network system according to claim 1 or 2.

4. The compensation control means determines the wavelength dispersion compensation amount based on the wavelength dispersion amount accumulated between the optical relay device and the reception terminal device in the path. The optical network system according to any one of claims 1 to 3.

5. The wavelength dispersion compensation amount is a compensation amount based on a wavelength dispersion amount within a predetermined range determined in advance in the optical transmission path from the optical relay device to the reception terminal device. The optical network system according to claim 4.

6. The wavelength dispersion compensation amount is a compensation amount based on the absolute value of the wavelength dispersion amount at each point from the optical relay device to the reception terminal device. The optical network system according to claim 4.

7. The optical relay device further includes phase conjugation means for performing phase conjugation processing on an electrical signal based on the received optical signal, The compensation control means determines the wavelength dispersion compensation amount in the optical relay device based on the wavelength dispersion compensation amount by the phase conjugation processing. The optical network system according to any one of claims 1 to 6.

8. Management means for managing wavelength information of an optical signal transmitted and received by an optical relay device in a path of an optical network and transmission path information of an optical transmission path connected to the optical relay device; Compensation control means for determining a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information; Comprising: The compensation control means obtains a wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device based on the wavelength information and the transmission path information on the reception side of the optical relay device, and based on the wavelength information and the transmission path information on the transmission side of the optical relay device, obtains a wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device, and determines the wavelength dispersion compensation amount based on the wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device and the wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device. Control device.

9. Manages wavelength information of an optical signal transmitted and received by an optical relay device in a path of an optical network and transmission path information of an optical transmission path connected to the optical relay device, Determines a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information, Based on the wavelength information and the transmission path information on the reception side of the optical relay device, obtains a wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device, and based on the wavelength information and the transmission path information on the transmission side of the optical relay device, obtains a wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device, and determines the wavelength dispersion compensation amount based on the wavelength dispersion amount accumulated in the optical transmission path on the reception side of the optical relay device and the wavelength dispersion amount accumulated in the optical transmission path on the transmission side of the optical relay device. Control method.

10. Manages wavelength information of an optical signal transmitted and received by an optical relay device in a path of an optical network and transmission path information of an optical transmission path connected to the optical relay device, Determines a wavelength dispersion compensation amount to be compensated in the optical relay device based on the wavelength information and the transmission path information, Based on the wavelength information and the transmission path information on the receiving side of the optical relay device, obtain the amount of wavelength dispersion accumulated in the optical transmission path on the receiving side of the optical relay device. Based on the wavelength information and the transmission path information on the transmitting side of the optical relay device, obtain the amount of wavelength dispersion accumulated in the optical transmission path on the transmitting side of the optical relay device. Determine the wavelength dispersion compensation amount based on the amount of wavelength dispersion accumulated in the optical transmission path on the receiving side of the optical relay device and the amount of wavelength dispersion accumulated in the optical transmission path on the transmitting side of the optical relay device. A control program for causing a computer to execute the processing.

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