Optical communication device, optical communication method, and optical communication system

Abstract

Provided are an optical communication device, an optical communication method and an optical communication system wherein improved transmission characteristics can be achieved. This optical communication device (NE) comprises: a monitor unit (MN) that is connected to an optical communication network (100) having multiple optical communication devices (NE) connected via transport paths used for transporting WDM signal light in which multiple optical signals have been wavelength-division-multiplexed and that monitors the received waveform (30) of an optical signal when the optical signal received from another optical communication device (NE) is converted to a digital signal; and a center-wavelength control unit (CW) that feedback-controls, on the basis of the monitored received waveform (30), the center wavelength (23) in the transmitted waveform (20) of the optical signal transmitted by the other optical communication device (NE).

Description

[Technical field]

[0001] The present invention relates to an optical communication device, an optical communication method, and an optical communication system. [Background technology]

[0002] Patent Document 1 describes an optical transmission system in which a transponder unit on the receiving side measures the BER (Bit Error Rate) of a received signal and feeds it back to the transmitting side.

[0003] Patent Document 2 describes a transmission device that calculates an index value for narrowing of an optical signal by calculating an error in sampling timing when a clock signal is extracted from an optical signal.

[0004] Patent Document 3 describes a transmission device that monitors the phase shift of an optical signal and prevents a wavelength adjacent to the outer edge of a transmission band from approaching the outer edge. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-213062 A [Patent Document 2] JP 2019-054404 A [Patent Document 3] JP 2016-131273 A Summary of the Invention [Problem to be solved by the invention]

[0006] There is a problem that the narrowing of wavelength bands used in WDM systems to increase the efficiency of channel accommodation and the deterioration of passband characteristics due to the miniaturization of wavelength selective switches (WSS) have resulted in the narrowing of wavelength bands and the deterioration of transmission characteristics.

[0007] In view of the above-mentioned problems, an object of the present disclosure is to provide an optical communication device, an optical communication method, and an optical communication system that can improve transmission characteristics. [Means for solving the problem]

[0008] An optical communication device according to one embodiment is connected to an optical communication network having a plurality of optical communication devices connected by a transmission line that transmits WDM signal light in which a plurality of optical signals are wavelength division multiplexed, and includes a monitor unit that monitors a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal, and a central wavelength control unit that feedback controls a central wavelength in a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored received waveform.

[0009] An optical communication method according to one embodiment includes, in an optical communication device connected to an optical communication network having a plurality of optical communication devices connected by a transmission line transmitting WDM signal light in which a plurality of optical signals are wavelength division multiplexed, a step of monitoring a received waveform of an optical signal when converting the optical signal received from another optical communication device into a digital signal, and a step of feedback controlling a center wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored received waveform.

[0010] An optical communication system according to one embodiment comprises an optical communication network having a plurality of optical communication devices connected by a transmission line that transmits WDM signal light in which a plurality of optical signals are wavelength division multiplexed, and each of the optical communication devices has a monitor unit that monitors a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal, and a central wavelength control unit that feedback controls a central wavelength in a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored received waveform.

[0011] An optical communication system according to one embodiment comprises an optical communication network having a plurality of optical communication devices connected by a transmission path that transmits WDM signal light in which a plurality of optical signals are wavelength division multiplexed, and a network management device that manages the optical communication network, wherein the network management device has a monitor unit that monitors a received waveform of the optical signal when a second optical communication device receives the optical signal transmitted by a first optical communication device and converts the optical signal into a digital signal, and a central wavelength control unit that feedback controls a central wavelength in a transmission waveform of the optical signal transmitted by the first optical communication device based on the monitored received waveform. Effect of the Invention

[0012] According to one embodiment, an optical communication device, an optical communication method, and an optical communication system capable of improving transmission characteristics are provided. [Brief description of the drawings]

[0013] [Figure 1] 1 is a configuration diagram illustrating an optical communication system according to an embodiment. [Diagram 2] 1 is a block diagram illustrating an optical communication device according to an embodiment. [Diagram 3] 4 is a diagram illustrating an example of a received waveform of an optical signal received by a receiving-side optical communication device according to the embodiment, in which the horizontal axis indicates frequency and the vertical axis indicates optical intensity. [Figure 4] 4A and 4B are diagrams illustrating examples of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by a transmitting optical communication device according to an embodiment; [Diagram 5] FIG. 1 is a flow chart illustrating an optical communication method according to an embodiment. [Figure 6] FIG. 11 is a configuration diagram illustrating another optical communication system according to an embodiment. [Figure 7] FIG. 11 is a block diagram illustrating a network management device in another optical communication system according to an embodiment. [Figure 8] 1 is a block diagram illustrating a configuration of an optical communication device according to a first embodiment. [Figure 9]FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by a transmitting optical communication device according to the first embodiment, showing the transmission waveform before adjustment by a central wavelength control section. [Figure 10] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by the optical communication device on the transmitting side according to the first embodiment, showing the transmission waveform being adjusted by the central wavelength control section. [Figure 11] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by the transmitting optical communication device according to the first embodiment, and shows the transmission waveform after adjustment by the central wavelength control section. [Figure 12] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by a transmitting optical communication device according to the first embodiment, showing the transmission waveform before adjustment by a central wavelength control section. [Figure 13] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by the optical communication device on the transmitting side according to the first embodiment, showing the transmission waveform being adjusted by the central wavelength control section. [Figure 14] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by the transmitting optical communication device according to the first embodiment, and shows the transmission waveform after adjustment by the central wavelength control section. [Figure 15] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by a transmitting optical communication device according to the first embodiment, showing the transmission waveform before adjustment by a central wavelength control section. [Figure 16] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by the optical communication device on the transmitting side according to the first embodiment, showing the transmission waveform being adjusted by the central wavelength control section. [Figure 17] FIG. 2 is a diagram illustrating an example of a transmission waveform and a narrowed bandwidth of an optical signal transmitted by the transmitting optical communication device according to the first embodiment, and shows the transmission waveform after adjustment by the central wavelength control section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, in each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0015] (Overview of the embodiment) Prior to describing the embodiments of the present disclosure, an overview of the embodiments of the present disclosure will be described. First, an optical communication system will be described. Then, an optical communication device will be described, and an optical communication method will be described. Also, another optical communication system and a network management device will be described.

[0016] [Optical communication system] An optical communication system according to an embodiment will be described. FIG. 1 is a configuration diagram illustrating an optical communication system according to an embodiment. As shown in FIG. 1, the optical communication system 1 includes an optical communication network 100. The optical communication network 100 has a plurality of optical communication devices NE1 and NE2. In the figure, two optical communication devices NE1 and NE2 are shown, but the number of the optical communication devices NE1 and NE2 is not limited. Each of the optical communication devices NE1 and NE2 is connected to the optical communication network via a transmission line. Thus, the optical communication network 100 is configured by connecting a plurality of optical communication devices NE1 and NE2 with a transmission line. Each of the optical communication devices NE may be connected in a point-to-point manner, a ring manner, or a mesh manner. The optical communication devices NE1 and NE2 are collectively referred to as the optical communication devices NE.

[0017] The transmission path transmits WDM signal light, which is a combination of multiple optical signals that have been wavelength division multiplexed. The WDM signal light is transmitted from an optical communication device NE1 on the transmitting side to an optical communication device NE2 on the receiving side. When the WDM signal light is transmitted from the optical communication device NE2 to the optical communication device NE1, the optical communication device NE2 is the transmitting side and the optical communication device NE1 is the receiving side.

[0018] The optical communication equipment NE is a node of the optical communication network 100. The optical communication equipment NE may be connected to a transmitter and a receiver (not shown) via a communication line. The optical communication equipment NE may function as a multiplexer, a relay device, and a demultiplexer under the control of ROADM (Reconfigurable Optical Add and Drop MultiPlexing). The optical communication network 100 transmits optical signals by wavelength division multiplexing (WDM).

[0019] The optical communication device NE2 on the receiving side receives the WDM signal light transmitted by the optical communication device NE1 on the transmitting side. The optical communication device NE2 branches a predetermined optical signal from the received WDM signal light. The optical communication device NE2 on the receiving side also converts the branched optical signal into a digital signal. For example, each optical communication device NE has a digital signal processing unit DSP. The digital signal processing unit DSP arranged in the optical communication device NE2 on the receiving side converts the received optical signal into a digital signal.

[0020] [Optical communication device] Next, an optical communication device will be described. Fig. 2 is a block diagram illustrating an optical communication device NE according to an embodiment. As shown in Fig. 2, the optical communication device NE has a digital signal processing unit DSP, a monitor unit MN, and a central wavelength control unit CW. The digital signal processing unit DSP, the monitor unit MN, and the central wavelength control unit CW have functions as a digital signal processing means, a monitor means, and a central wavelength control means, respectively.

[0021] The digital signal processing unit DSP converts the received optical signal into a digital signal. The monitor unit MN monitors the received waveform of the optical signal when converting the optical signal received from another optical communication device NE into a digital signal. The central wavelength control unit CW feedback controls the central wavelength of the transmission waveform of the optical signal transmitted by the other optical communication device NE based on the monitored received waveform.

[0022] FIG. 3 is a diagram illustrating an example of a received waveform of an optical signal received by a receiving-side optical communication device NE2 according to an embodiment, where the horizontal axis indicates frequency and the vertical axis indicates optical intensity. As shown in FIG. 3, when an optical signal received by the receiving-side optical communication device NE2 is converted into a digital signal in a digital signal processing unit DSP, the analog received waveform is monitored by a monitor unit MN. The horizontal axis may indicate the wavelength of the optical signal. Thus, the monitor unit MN monitors the received waveform, which indicates the relationship of optical intensity to wavelength or frequency in the optical signal. The monitor unit MN may monitor the center wavelength or center frequency of the received waveform. Alternatively, the monitor unit MN may monitor the shape including the bandwidth of the received waveform.

[0023] FIG. 4 is a diagram illustrating the transmission waveform and narrowed bandwidth of an optical signal transmitted by the optical communication device NE1 on the transmitting side according to the embodiment. As shown in FIG. 4, the optical signal transmitted from the optical communication device NE1 on the transmitting side has a transmission waveform 20. Here, the high wavelength side or high frequency side is defined as the +X-axis direction. The end portion on the -X-axis side of the transmission waveform 20 is called an end portion 21, and the end portion on the +X-axis side of the transmission waveform 20 is called an end portion 22. The central wavelength of the transmission waveform 20 is called a central wavelength 23. In addition, when the X-axis indicates the frequency, the central wavelength 23 may be replaced with the central frequency. Similarly, the central wavelength may be replaced with the central frequency below. The transmission waveform 20 has a bandwidth 25.

[0024] An optical signal transmitted from the optical communication device NE1 on the transmitting side is added to a WDM signal light and transmitted through the optical communication network 100. Then, in the optical communication device NE2, the optical signal is narrowed by a filter of a wavelength selective switch that selects an optical signal to be added to the WDM signal light or an optical signal to be dropped from the WDM signal light. The end on the -X-axis direction of the band 40 narrowed by the filter is called an end 41, and the end on the +X-axis direction is called an end 42. The bandwidth is called a bandwidth 45.

[0025] The monitor unit MN of the optical communication device NE2 monitors the bandwidth 45 narrowed by the filters of the wavelength selective switches in the multiple optical communication devices NE. As a result, the monitor unit MN monitors the optical signal in the narrowed bandwidth 45 as a received waveform 30. The central wavelength control unit CW feedback-controls the central wavelength 23 in the transmission waveform 20 of the optical signal transmitted by the other optical communication device NE1 based on the monitored received waveform 30.

[0026] For example, feedback control is performed to move the central wavelength 23 of the transmission waveform 20 of the optical signal transmitted by the optical communication device NE1 in the +X-axis direction based on the central wavelength of the received waveform 30 shown in Fig. 4. For example, the central wavelength control unit CW controls the central wavelength 23 of the transmission waveform 20 by controlling the tunable laser of the optical communication device NE1. In this way, the monitor unit MN monitors the position of the filter end 41 where the transmission waveform 20 is cut off.

[0027] Moreover, the central wavelength control unit CW further moves the central wavelength 23 of the transmission waveform 20 toward the +X-axis direction. As a result, the monitor unit MN monitors the position of the end 42 of the filter where the transmission waveform 20 has been cut off. In this way, the monitor unit MN can obtain the shape of the filter from the positions of the end 41 and end 42 of the filter, and align the central wavelength 23 of the transmission waveform 20 with the center of the narrowed bandwidth 45. The central wavelength control CW may feedback-control the central wavelength 23 of the transmission waveform 20 based on the shape of the reception waveform 30 including its bandwidth.

[0028] [Optical communication method] Next, an optical communication method will be described. Fig. 5 is a flow chart illustrating an optical communication method according to an embodiment. As shown in step S11 of Fig. 5, a received waveform 30 is monitored. Specifically, the monitor unit MN of the optical communication device NE2 monitors the received waveform 30 of the optical signal when converting an optical signal received from another optical communication device NE1 into a digital signal.

[0029] Next, as shown in step S12, the central wavelength 23 in the transmission waveform 20 is feedback-controlled based on the received waveform 30. Specifically, the central wavelength control unit CW of the optical communication device NE2 feedback-controls the central wavelength 23 in the transmission waveform 20 of the optical signal transmitted by the other optical communication device NE1 based on the monitored received waveform 30.

[0030] According to this embodiment, the central wavelength control unit CW feedback-controls the central wavelength 23 of the transmission waveform 20 based on the received waveform 30 monitored by the monitor unit MN. Therefore, each optical signal in the WDM signal light has an appropriate central wavelength, and the transmission characteristics can be improved.

[0031] [Another optical communication system] Next, another optical communication system will be described. Fig. 6 is a configuration diagram illustrating another optical communication system according to an embodiment. As shown in Fig. 6, an optical communication system 1a may include a network management device NMS and an optical communication network 100. In the figure, four optical communication devices NE1 to NE4 are shown. Each optical communication device NE is connected to the network management device NMS by a communication line such as a LAN.

[0032] [Network management device] Fig. 7 is a block diagram illustrating a network management device NMS in another optical communication system according to an embodiment. As shown in Fig. 7, the network management device NMS includes a monitor unit 11 and a central wavelength control unit 12. The monitor unit 11 and the central wavelength control unit 12 function as a monitor means and a central wavelength control means. In the case of the optical communication system 1a, each optical communication device NE may or may not include a monitor unit MN and a central wavelength control unit CW.

[0033] The monitor unit 11 monitors the received waveform 30 of the optical signal received by each optical communication device NE. For example, the optical communication device NE2 receives an optical signal transmitted by the optical communication device NE1. The monitor unit 11 monitors the received waveform 30 of the optical signal received by the optical communication device NE2 when the optical communication device NE2 converts the optical signal into a digital signal. The monitor unit 11 may monitor a bandwidth 45 narrowed by a filter that selects the wavelength of the optical signal in a plurality of optical communication devices NE. The monitor unit 11 may monitor the received waveform 30 indicating the relationship of optical intensity to wavelength or frequency in the optical signal. The central wavelength control unit 12 feedback controls the central wavelength 23 of the transmitted waveform 20 of the optical signal transmitted by the optical communication device NE1 based on the monitored received waveform 30.

[0034] In another optical communication system 1a, the optical communication method shown in FIG. 5 may be performed using a network management device NMS. For example, the steps in FIG. S11 2, the monitor unit 11 of the network management device NMS may monitor a reception waveform 30 of the received optical signal when the optical communication device NE2 converts the received optical signal into a digital signal.

[0035] Next, step S12 As shown in FIG. 1, the central wavelength control unit 12 of the network management device NMS may feedback-control the central wavelength 23 of the transmission waveform 20 of the optical signal to be transmitted in the optical communication device NE1 that transmitted the optical signal, based on the monitored reception waveform 30 in the optical communication device NE2.

[0036] According to another optical communication system, a central wavelength control unit 12 feedback controls a central wavelength 23 in a transmission waveform 20 based on a received waveform 30 monitored by a monitor unit 11. Therefore, each optical signal in the WDM signal light has an appropriate central wavelength, and the transmission characteristics can be improved.

[0037] (Embodiment 1) Next, a detailed description will be given of the optical communication system according to the embodiment 1. First, a configuration of the optical communication device NE will be described. Then, an optical communication method will be described.

[0038] [Configuration of optical communication device] Fig. 8 is a block diagram illustrating a configuration of an optical communication device NE according to embodiment 1. As shown in Fig. 8, the optical communication device NE has a wavelength cross-connect function unit 110, a wavelength cross-connect function unit 120, a wavelength multiplexing / demultiplexing function unit 130, a transponder function unit 140, and an NE control unit 150 in addition to a digital signal processing unit DSP, a monitor unit MN, and a central wavelength control unit CW.

[0039] The wavelength cross-connect function unit 110 and the wavelength cross-connect function unit 120 function as wavelength cross-connect means. The wavelength multiplexing / demultiplexing function unit 130 and the transponder function unit 140 function as wavelength multiplexing / demultiplexing means and transponder means. The NE control unit 150 functions as control means for the optical communication equipment NE.

[0040] An amplifier may be connected to the wavelength cross connect functional unit 110 and the wavelength cross connect functional unit 120. A transmitter and a receiver may be connected to the wavelength multiplexing / demultiplexing functional unit 130 via the transponder functional unit 140. A multiplexing device may be configured by the wavelength cross connect functional unit 120 and the wavelength multiplexing / demultiplexing functional unit 130. A demultiplexing device may be configured by the wavelength cross connect functional unit 110 and the wavelength multiplexing / demultiplexing functional unit 130. A relay device may be configured by the wavelength cross connect functional unit 110 and the wavelength cross connect functional unit 120. Note that the relay device may not have the wavelength cross connect functional unit 110 and the wavelength cross connect functional unit 120 and may be configured by an amplifier.

[0041] The wavelength cross-connect function unit 110 wavelength-separates a predetermined optical signal from the received WDM signal light. Specifically, the wavelength cross-connect function unit 110 selects a wavelength band into which an optical signal is to be branched and switches the selected wavelength band. The wavelength cross-connect function unit 110 includes a WSS control unit 111 and a wavelength selective switch 112. The WSS control unit 111 functions as a control means for controlling the operation of the wavelength selective switch 112. The wavelength selective switch 112 functions as a switch means for selecting a predetermined wavelength.

[0042] The wavelength cross-connect functional unit 120 wavelength-multiplexes a predetermined optical signal into a WDM signal light. Specifically, the wavelength cross-connect functional unit 120 selects a wavelength band into which an optical signal is added and switches the selected wavelength band. The wavelength cross-connect functional unit 120 includes a WSS control unit 121 and a wavelength selective switch 122. The WSS control unit 121 functions as a control means for controlling the operation of the wavelength selective switch 122. The wavelength selective switch 122 functions as a switch means for selecting a predetermined wavelength.

[0043] The wavelength multiplexing / demultiplexing functional unit 130 and the transponder functional unit 140 transmit the optical signal separated from the wavelength cross-connect functional unit 110 to the receiver. Specifically, the wavelength multiplexing / demultiplexing functional unit 130 and the transponder functional unit 140 receive the optical signal to be dropped from the wavelength band. In addition, the wavelength multiplexing / demultiplexing functional unit 130 and the transponder functional unit 140 multiplex the optical signal transmitted from the transmitter and transmit the multiplexed signal to the wavelength cross-connect functional unit 120. Specifically, the wavelength multiplexing / demultiplexing functional unit 130 and the transponder functional unit 140 transmit the optical signal to be added to the wavelength band.

[0044] The NE control unit 150 controls the operations of the wavelength cross-connect function unit 110 , the wavelength cross-connect function unit 120 , the wavelength multiplexing / demultiplexing function unit 130 and the transponder function unit 140 .

[0045] [Optical communication method] Next, an optical communication method will be described as an operation of the optical communication device NE. The optical communication method will be described in three cases: when the bandwidth 25 of the transmission waveform 20 is larger than the narrowed bandwidth 45 (bandwidth of the transmission waveform>narrowed bandwidth), when the bandwidth 25 of the transmission waveform 20 is smaller than the narrowed bandwidth 45 (bandwidth of the transmission waveform<narrowed bandwidth), and when the bandwidth 25 of the transmission waveform 20 is overwhelmingly smaller than the narrowed bandwidth 45 (bandwidth of the transmission waveform<<narrowed bandwidth).

[0046] [Transmitted waveform bandwidth>narrowed bandwidth] Figures 9 to 11 are diagrams illustrating the transmission waveform 20 and narrowed bandwidth 45 of an optical signal transmitted by the transmitting optical communication device NE in embodiment 1, where Figure 9 shows the transmission waveform 20 before adjustment by the central wavelength control unit CW, Figure 10 shows the transmission waveform 20 during adjustment by the central wavelength control unit CW, and Figure 11 shows the transmission waveform 20 after adjustment by the central wavelength control unit CW.

[0047] As shown in Figure 9, the bandwidth 25 of the transmission waveform 20 is larger than the narrowed bandwidth 45. Ends 21 and 22 of the transmission waveform 20 are located outside the range of the narrowed bandwidth 45. Therefore, the monitor unit MN monitors the reception waveform 30 across the narrowed bandwidth 45. The monitor unit MN can also monitor the positions of ends 41 and 42 of the bandwidth 45 narrowed by the filter. This allows the monitor unit MN to monitor the center position of the bandwidth 45.

[0048] 10, the central wavelength control unit CW feedback-controls the transmission waveform 20 based on the received waveform 30. For example, the central wavelength control unit CW dynamically controls the transmission waveform 20 to move the transmission waveform 20 in the +X-axis direction. As a result, the end 21 of the transmission waveform 20 moves within the narrowed bandwidth 45. This allows the monitor unit MN to monitor the end 21 of the transmission waveform 20.

[0049] Moreover, the central wavelength control unit CW dynamically controls the transmission waveform 20 to move the transmission waveform 20 in the -X-axis direction. Then, the end 22 of the transmission waveform 20 moves into the range of the narrowed bandwidth 45. This allows the monitor unit MN to monitor the end 22 of the transmission waveform 20. Therefore, it is possible to monitor the end 21 and the end 22 of the transmission waveform 20. This allows the monitor unit MN to monitor the bandwidth 25 of the transmission waveform 20 and the central wavelength 23. Therefore, as shown in FIG. 11, the central wavelength control unit CW can place the central wavelength 23 of the transmission waveform 20 at the center of the narrowed bandwidth 45.

[0050] [Bandwidth of transmitted waveform < narrowed bandwidth] 12 to 14 are diagrams illustrating the transmission waveform 20 and narrowed bandwidth 45 of an optical signal transmitted by the transmitting optical communication device NE in embodiment 1, where FIG. 12 shows the transmission waveform 20 before adjustment by the central wavelength control unit CW, FIG. 13 shows the transmission waveform 20 during adjustment by the central wavelength control unit CW, and FIG. 14 shows the transmission waveform 20 after adjustment by the central wavelength control unit CW.

[0051] As shown in FIG. 12, the bandwidth 25 of the transmission waveform 20 is smaller than the narrowed bandwidth 45. The end 21 of the transmission waveform 20 is located outside the range of the narrowed bandwidth 45. On the other hand, the end 22 of the transmission waveform 20 is located within the range of the narrowed bandwidth 45. Therefore, the monitor unit MN can monitor the end 22 of the transmission waveform 20. In addition, the monitor unit MN monitors the reception waveform 30 on the -X-axis direction side of the narrowed bandwidth 45. Therefore, the monitor unit MN can monitor the position of the end 41 of the bandwidth 45 narrowed by the filter.

[0052] As shown in FIG. 13, the central wavelength control unit CW feedback-controls the transmission waveform 20 based on the reception waveform 30. For example, the central wavelength control unit CW dynamically controls the transmission waveform 20 to move the transmission waveform 20 to the +X-axis direction. Then, the end 21 of the transmission waveform 20 moves to within the range of the narrowed bandwidth 45. Therefore, the monitor unit MN can monitor the end 21 of the transmission waveform 20. As a result, the monitor unit MN can monitor the bandwidth 25 of the transmission waveform 20 and the central wavelength 23 of the transmission waveform 20. In addition, the monitor unit MN monitors the reception waveform 30 on the +X-axis direction side of the narrowed bandwidth 45. Therefore, the monitor unit MN can monitor the position of the end 42 of the bandwidth 45 narrowed by the filter. As a result, the monitor unit MN can monitor the center position of the bandwidth 45.

[0053] In this manner, the central wavelength control portion CW can place the central wavelength 23 of the transmit waveform 20 at the center of the narrowed bandwidth 45, as shown in FIG.

[0054] [Transmitted waveform bandwidth << Narrowed bandwidth] 15 to 17 are diagrams illustrating the transmission waveform 20 and narrowed bandwidth 45 of an optical signal transmitted by the transmitting optical communication device NE in embodiment 1, where FIG. 15 shows the transmission waveform 20 before adjustment by the central wavelength control unit CW, FIG. 16 shows the transmission waveform 20 during adjustment by the central wavelength control unit CW, and FIG. 17 shows the transmission waveform 20 after adjustment by the central wavelength control unit CW.

[0055] 15, the bandwidth 25 of the transmission waveform 20 is overwhelmingly smaller than the narrowed bandwidth 45. The ends 21 and 22 of the transmission waveform 20 are located within the range of the narrowed bandwidth 45. Therefore, the monitor unit MN can monitor the ends 21 and 22 of the transmission waveform 20. This allows the monitor unit MN to monitor the bandwidth 25 of the transmission waveform 20 and the center wavelength 23 of the transmission waveform 20. The monitor unit MN can also monitor the reception waveform 30.

[0056] 16, the central wavelength control unit CW feedback-controls the transmission waveform 20 based on the reception waveform 30. For example, the central wavelength control unit CW dynamically controls the transmission waveform 20 to move the transmission waveform 20 toward the -X-axis direction from the end 41. As a result, the transmission waveform 20 moves outside the range of the narrowed bandwidth 45. Therefore, the monitor unit MN can monitor the position of the end 41 of the bandwidth 45 narrowed by the filter.

[0057] Furthermore, the central wavelength control unit CW dynamically controls the transmission waveform 20 to move the transmission waveform 20 toward the +X-axis direction from the end 42. As a result, the transmission waveform 20 moves outside the range of the narrowed bandwidth 45. Thus, the monitor unit MN can monitor the position of the end 42 of the bandwidth 45 narrowed by the filter. This allows the monitor unit MN to monitor the center position of the bandwidth 45.

[0058] In this manner, the central wavelength control portion CW can place the central wavelength 23 of the transmit waveform 20 at the center of the narrowed bandwidth 45, as shown in FIG.

[0059] For example, the monitor unit MN may monitor the received waveform of the main optical signal transmitted and received during operation of the optical communication network 100, or may monitor the received waveform of the training optical signal transmitted and received during adjustment of the optical communication network 100.

[0060] The main optical signal may use a transmission waveform 20 such that the bandwidth 25 of the transmission waveform 20 is greater than the narrowed bandwidth 45. On the other hand, the training optical signal may use a transmission waveform 20 such that the bandwidth 25 of the transmission waveform 20 is less than the narrowed bandwidth 45, and the bandwidth 25 of the transmission waveform 20 is less than the narrowed bandwidth 45. By making the bandwidth 25 of the training optical signal smaller than the narrowed bandwidth 45, the influence between adjacent optical signals can be reduced. In addition, the wavelength width for which the central wavelength control section CW dynamically controls the transmission waveform 20 can be small, so that the ends 41 and 42 of the narrowed bandwidth 45 can be easily found. This makes the adjustment easier.

[0061] Also, the main optical signal may use a transmission waveform 20 such that the bandwidth 25 of the transmission waveform 20 is smaller than the narrowed bandwidth 45, and the bandwidth 25 of the transmission waveform 20 is smaller than the narrowed bandwidth 45. This can increase the transmission capacity.

[0062] (Embodiment 2) Next, a description will be given of an optical communication system according to embodiment 2. In this embodiment, the received waveform 30 is monitored, and the adjustment timing for performing feedback control of the transmitted waveform 20 is changed.

[0063] For example, when a new optical communication equipment NE is connected to the optical communication network 100, the transmission waveform 20 may be adjusted. Specifically, when a new optical communication equipment NE is connected, a training optical signal may be transmitted and received. Then, the new optical communication equipment NE may be made to monitor the received waveform 30 and feedback-control the center wavelength 23 of the transmission waveform 20 on the transmitting side based on the received waveform 30. This makes it possible to improve the transmission characteristics of the newly set up optical communication equipment NE.

[0064] Also, for example, the transmission waveform 20 may be adjusted to correct changes over time in the optical communication network 100. Specifically, when the optical communication network 100 is inspected at predetermined intervals, a training optical signal may be transmitted and received. Then, each optical communication device NE may be caused to monitor the received waveform 30 and feedback control the central wavelength 23 of the transmission waveform 20 on the transmitting side. This makes it possible to reduce the influence of changes over time in the optical communication network 100.

[0065] Furthermore, in the optical communication network 100, for example, when changing a path from the optical communication device NE1 to the optical communication device NE2, the transmission waveform 20 may be adjusted. Specifically, when changing a path from the optical communication device NE1 to the optical communication device NE2, a training optical signal may be transmitted and received. Then, the optical communication device NE2 may be caused to monitor the received waveform 30 and feedback control the center wavelength 23 of the transmission waveform 20 on the transmitting side. This makes it possible to improve the transmission characteristics of the changed path.

[0066] The present invention has been described above with reference to the outline of the embodiment and the first and second embodiments, but the present invention is not limited to the outline of the embodiment and the first and second embodiments. Various modifications that can be understood by a person skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. For example, an embodiment that combines the configurations of the outline of the embodiment and the first and second embodiments is also included in the scope of the technical idea.

[0067] A part or all of the above-described embodiments can be described as, but is not limited to, the following supplementary notes.

[0068] (Appendix 1) In an optical communication device connected to an optical communication network having a plurality of optical communication devices connected by a transmission line for transmitting a WDM signal light in which a plurality of optical signals are wavelength division multiplexed, a step of monitoring a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal; feedback-controlling a center wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored reception waveform; An optical communication method comprising: (Appendix 2) In the monitoring step, In the plurality of optical communication devices, a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or a wavelength of the optical signal to be dropped from the WDM signal light is monitored. 2. The optical communication method according to claim 1. (Appendix 3) In the monitoring step, monitoring a bandwidth of the transmit waveform; 3. The optical communication method according to claim 1 or 2. (Appendix 4) In the monitoring step, monitoring a received waveform indicating a relationship between optical intensity and wavelength or frequency of the optical signal; 4. The optical communication method according to claim 1. (Appendix 5) In the monitoring step, monitoring the received waveform of a main optical signal transmitted and received during operation of the optical communication network, and the received waveform of a training optical signal transmitted and received during adjustment of the optical communication network; 5. The optical communication method according to claim 1. (Appendix 6) a bandwidth of the training optical signal is narrowed to be smaller than a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or a wavelength of the optical signal to be dropped from the WDM signal light; 6. The optical communication method according to claim 5. (Appendix 7) transmitting and receiving the training optical signal at least in any one of the following cases: when a new optical communication device is connected to the optical communication network; when the optical communication network is inspected at a predetermined interval; and when a route in the optical communication network is changed. 7. The optical communication method according to claim 5 or 6. (Appendix 8) an optical communication network having a plurality of optical communication devices connected by a transmission line for transmitting WDM signal light in which a plurality of optical signals are wavelength division multiplexed; The optical communication device includes: a monitor unit that monitors a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal; a central wavelength control unit that feedback-controls a central wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored reception waveform; having Optical communication system. (Appendix 9) the monitor unit monitors, in the plurality of optical communication devices, a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or a wavelength of the optical signal to be dropped from the WDM signal light. 9. The optical communication system of claim 8. (Appendix 10) The monitor unit monitors a bandwidth of the transmission waveform. 10. The optical communication system of claim 8 or 9. (Appendix 11) the monitor unit monitors a received waveform indicating a relationship of optical intensity with respect to a wavelength or a frequency of the optical signal; 11. The optical communication system according to any one of claims 8 to 10. (Appendix 12) the monitor unit monitors the received waveform of a main optical signal transmitted and received during operation of the optical communication network, and the received waveform of a training optical signal transmitted and received during adjustment of the optical communication network. 12. The optical communication system according to claim 8. (Appendix 13) a bandwidth of the training optical signal is narrowed to be smaller than a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or a wavelength of the optical signal to be dropped from the WDM signal light; 13. The optical communication system of claim 12. (Appendix 14) transmitting and receiving the training optical signal at least in any one of the following cases: when a new optical communication device is connected to the optical communication network; when the optical communication network is inspected at a predetermined interval; and when a route in the optical communication network is changed. 14. The optical communication system of claim 12 or 13. (Appendix 15) an optical communication network having a plurality of optical communication devices connected by a transmission line that transmits WDM signal light obtained by wavelength division multiplexing a plurality of optical signals; a network management device for managing the optical communication network; Equipped with The network management device a monitor unit that monitors a received waveform of the optical signal when a second optical communication device receives the optical signal transmitted by a first optical communication device and converts the optical signal into a digital signal; a central wavelength control unit that feedback-controls a central wavelength of a transmission waveform of the optical signal transmitted by the first optical communication device based on the monitored reception waveform; having Optical communication system. (Appendix 16) the monitor unit monitors, in the plurality of optical communication devices, a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or a wavelength of the optical signal to be dropped from the WDM signal light. 16. The optical communication system of claim 15. (Appendix 17) The monitor unit monitors a bandwidth of the transmission waveform. 17. The optical communication system of claim 15 or 16. (Appendix 18) the monitor unit monitors a received waveform indicating a relationship of optical intensity with respect to a wavelength or a frequency of the optical signal; 18. The optical communication system according to any one of claims 15 to 17. (Appendix 19) the monitor unit monitors the received waveform of a main optical signal transmitted and received during operation of the optical communication network, and the received waveform of a training optical signal transmitted and received during adjustment of the optical communication network. 19. The optical communication system according to any one of claims 15 to 18. (Appendix 20) a bandwidth of the training optical signal is narrowed to be smaller than a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or a wavelength of the optical signal to be dropped from the WDM signal light; 20. The optical communication system of claim 19. (Appendix 21) transmitting and receiving the training optical signal at least in any one of the following cases: when a new optical communication device is connected to the optical communication network; when the optical communication network is inspected at a predetermined interval; and when a route in the optical communication network is changed. 21. The optical communication system of claim 19 or 20.

[0069] This application claims priority based on Japanese Patent Application No. 2021-050738, filed on March 24, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0070] 1, 1a Optical communication system 11 Monitor section 12 Central wavelength control section 20 Transmission Waveform 21, 22 End 23 Center wavelength 25 Bandwidth 30 Received Waveform 40 Narrowed Bandwidth 41 End 42 End 45 Bandwidth 100 Optical Communication Network CW central wavelength control section DSP Digital Signal Processing Unit MN Monitor Unit NE, NE1, NE2, NE3, NE4 Optical communication equipment NMS Network Management Device

Claims

1. a monitor means for connecting to an optical communication network having a plurality of optical communication devices connected by a transmission line for transmitting a WDM signal light obtained by wavelength division multiplexing a plurality of optical signals, and for monitoring a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal; a central wavelength control means for feedback-controlling a central wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored reception waveform; Equipped with said monitoring means monitors the bandwidth of said transmission waveform; Optical communication equipment.

2. the monitor means monitors, in the plurality of optical communication devices, a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or the optical signal to be dropped from the WDM signal light; 2. The optical communication device according to claim 1.

3. the monitoring means monitors a received waveform indicating a relationship between a wavelength or a frequency and an optical intensity of the optical signal; 2. The optical communication device according to claim 1.

4. the monitor means monitors the received waveform of a main optical signal transmitted and received during operation of the optical communication network, and the received waveform of a training optical signal transmitted and received during adjustment of the optical communication network.

2. The optical communication device according to claim 1.

5. a monitor means for connecting to an optical communication network having a plurality of optical communication devices connected by a transmission line for transmitting a WDM signal light obtained by wavelength division multiplexing a plurality of optical signals, and for monitoring a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal; a central wavelength control means for feedback-controlling a central wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored reception waveform; Equipped with The monitor means monitors the received waveform of a main optical signal transmitted and received during operation of the optical communication network, and the received waveform of a training optical signal transmitted and received during adjustment of the optical communication network, a bandwidth of the training optical signal is narrowed to be smaller than a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or the optical signal to be dropped from the WDM signal light; Optical communication equipment.

6. transmitting and receiving the training optical signal at least in any one of the following cases: when a new optical communication device is connected to the optical communication network; when the optical communication network is inspected at a predetermined interval; and when a route in the optical communication network is changed.

6. An optical communication device according to claim 4 or 5.

7. In an optical communication device connected to an optical communication network having a plurality of optical communication devices connected by a transmission line for transmitting a WDM signal light in which a plurality of optical signals are wavelength division multiplexed, a step of monitoring a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal; feedback-controlling a center wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored reception waveform; Equipped with In the monitoring step, monitoring a bandwidth of the transmit waveform; Optical communication method.

8. In an optical communication device connected to an optical communication network having a plurality of optical communication devices connected by a transmission line for transmitting a WDM signal light in which a plurality of optical signals are wavelength division multiplexed, a step of monitoring a received waveform of the optical signal when converting the optical signal received from another optical communication device into a digital signal; feedback-controlling a center wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored reception waveform; Equipped with In the monitoring step, monitoring the received waveform of a main optical signal transmitted and received during operation of the optical communication network, and the received waveform of a training optical signal transmitted and received during adjustment of the optical communication network; a bandwidth of the training optical signal is narrowed to be smaller than a bandwidth narrowed by a filter that selects a wavelength of the optical signal to be added to the WDM signal light or the optical signal to be dropped from the WDM signal light; Optical communication method.

9. an optical communication network including a plurality of optical communication devices connected by a transmission line for transmitting WDM signal light in which a plurality of optical signals are wavelength division multiplexed; The optical communication device includes: a monitor means for monitoring a received waveform of the optical signal when the optical signal received from another optical communication device is converted into a digital signal; a central wavelength control means for feedback-controlling a central wavelength of a transmission waveform of the optical signal transmitted by the other optical communication device based on the monitored reception waveform; having said monitoring means monitors the bandwidth of said transmission waveform; Optical communication system.

10. an optical communication network having a plurality of optical communication devices connected by a transmission line for transmitting WDM signal light in which a plurality of optical signals are wavelength division multiplexed; a network management device for managing the optical communication network; Equipped with The network management device a monitor means for monitoring a received waveform of the optical signal when a second optical communication device receives the optical signal transmitted by a first optical communication device and converts the optical signal into a digital signal; a central wavelength control means for feedback-controlling a central wavelength of a transmission waveform of the optical signal transmitted by the first optical communication device based on the monitored reception waveform; having said monitoring means monitors the bandwidth of said transmission waveform; Optical communication system.

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