Optical communication device, optical communication system, and transfer method

Abstract

This optical communication device comprises: a first optical switch that is connected to a plurality of optical transmission lines and that outputs an optical signal inputted from any one of the optical transmission lines, to another one of the optical transmission lines; a second optical switch that is connected to a plurality of optical transmission lines and that outputs an optical signal inputted from any one of the optical transmission lines, to another one of the optical transmission lines; and a multicast transfer unit for transferring, by multicast, the optical signal transmitted from a first device connected to the first optical switch, to at least one second device connected to the second optical switch.　

Description

[Technical Field]

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

[0002] Conventionally, optical communication devices capable of relaying optical signals according to their destinations while reducing delays have been proposed (see, for example, Patent Document 1). Fig. 8 is a diagram showing an example of the configuration of an optical communication system 100 including a conventional optical communication device. The optical communication system 100 includes an optical SW 110 and a control unit 115, which constitute the optical communication device. Subscriber devices 140-1 to 140-3 are connected to the optical SW 110.

[0003] The optical SW 110 is connected to a plurality of optical transmission lines, and outputs an optical signal input from one of the optical transmission lines to another optical transmission line. The optical SW 110 shown in Fig. 8 has first ports 111-1 to 111-6 and second ports 112-1 to 112-6. Each of the first ports 111 is connected to one of the subscriber devices 140-1 to 140-3 via one of the optical transmission lines 135-1 to 135-3. Each of the second ports 112 is connected to one of the optical transmission lines 136-1 to 136-4 and a return transmission line 137.

[0004] The return transmission line 137 is an optical transmission line for inputting an optical signal output from one port to another port. For example, in the example shown in Fig. 8, the return transmission line 137 is connected to the second port 112-4 and the second port 112-5. This allows, for example, an optical signal output from the second port 112-4 to be input to the second port 112-5.

[0005] The control unit 115 is connected to the second port 112-6 of the optical SW 110 via an optical transmission path 136-4. The control unit 115 includes a wavelength management control unit 120 and an optical SW control unit 130. The wavelength management control unit 120 assigns wavelengths to the optical subscriber devices 140. The optical SW control unit 130 switches the path of the optical SW 110. In the example shown in FIG. 8 , the optical SW control unit 130 switches the path of the optical SW 110 so that the first port 111-2 to which the optical subscriber device 140-1 is connected is connected to the second port 112-2, the first port 111-4 to which the optical subscriber device 140-2 is connected is connected to the second port 112-4, and the first port 111-5 to which the optical subscriber device 140-3 is connected is connected to the second port 112-5.

[0006] As a result, the optical signal transmitted from the subscriber device 140-1 is input to the first port 111-2 of the optical SW 110 via the optical transmission path 135-1 and is output from the second port 112-2 of the optical SW 110 to the optical transmission path 136-2. Furthermore, the optical signal transmitted from the subscriber device 140-2 is input to the first port 111-4 of the optical SW 110 via the optical transmission path 135-2 and is output from the second port 112-4 of the optical SW 110 to the return transmission path 137. The optical signal output to the return transmission path 137 is input to the second port 112-5 of the optical SW 110 and is output from the first port 111-5 of the optical SW 110 to the optical transmission path 135-3. The optical signal output to the optical transmission path 135-3 is transmitted to the subscriber device 140-3.

[0007] As described above, low-delay communication can be achieved by using the return transmission path 137 for a port (e.g., the second port 112) different from the port (e.g., the first port 111) to which the subscriber device 140 is connected. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2021 / 131202 Summary of the Invention [Problem to be solved by the invention]

[0009] In the optical communication system 100 shown in Fig. 8, by arranging multiple optical SWs 110-1 to 110-P (P is an integer of 2 or more) in parallel at one point, the maximum number of users that can transmit to each direction can be increased. Fig. 9 is a diagram for explaining a configuration in which multiple optical SWs 110 are arranged in parallel. In the example shown in Fig. 9, optical SWs 110-1 to 110-P are arranged in parallel, and a subscriber device 140 is connected to each optical SW 110.

[0010] In order to perform loopback communication between the optical subscriber device 140-1 connected to the optical SW 110-1 and the optical subscriber device 140-2 connected to the optical SW 110-2, it is necessary to connect the second port 112-1 of the optical SW 110-1 and the second port 112-1 of the optical SW 110-2 with a loopback transmission line 137. When there are P optical SWs 110 and one optical SW 110 accommodates n (n is an integer equal to or greater than 1) optical subscriber devices 140, in order for each optical SW 110 to connect with an arbitrary optical subscriber device 140 at an arbitrary timing, it is necessary to connect the loopback transmission lines 137 using n×(p−1) ports from one optical SW 110.

[0011] Within the optical SW 110, n lines are required to communicate with any subscriber device 140, so a total of np ports are required for connections between SWs and within the SW. While it is possible to reduce the number of return transmission lines 137 and physically change the wiring each time a connection request is received, this is undesirable because it increases on-site operation. Therefore, there is a demand for technology that eliminates the need for physical wiring and enables each subscriber device to connect to any subscriber device at any time using fewer return transmission lines than before.

[0012] In view of the above circumstances, the present invention aims to provide a technology that enables each subscriber device to connect to any other subscriber device at any timing using a smaller number of return transmission paths than conventional methods when performing return communication in an optical communication system equipped with multiple optical switches. [Means for solving the problem]

[0013] One aspect of the present invention is an optical communication device comprising: a first optical switch connected to a plurality of optical transmission paths and outputting an optical signal input from any of the optical transmission paths to another optical transmission path; a second optical switch connected to a plurality of optical transmission paths and outputting an optical signal input from any of the optical transmission paths to another optical transmission path; and a multicast forwarding unit that forwards an optical signal transmitted from a first device connected to the first optical switch to one or more second devices connected to the second optical switch by multicast.

[0014] One aspect of the present invention is an optical communication system comprising: a first optical switch connected to a plurality of optical transmission paths and outputting an optical signal input from any of the optical transmission paths to another optical transmission path; a second optical switch connected to a plurality of optical transmission paths and outputting an optical signal input from any of the optical transmission paths to another optical transmission path; and a multicast forwarding unit that forwards an optical signal transmitted from a first device connected to the first optical switch to one or more second devices connected to the second optical switch by multicast.

[0015] One aspect of the present invention is a transfer method in which a first optical switch is connected to multiple optical transmission paths and outputs an optical signal input from any of the optical transmission paths to another optical transmission path, a second optical switch is connected to multiple optical transmission paths and outputs an optical signal input from any of the optical transmission paths to another optical transmission path, and an optical signal transmitted from a first device connected to the first optical switch is multicast to one or more second devices connected to the second optical switch. [Effects of the Invention]

[0016] According to the present invention, when loopback communication is performed in an optical communication system equipped with multiple optical switches, it becomes possible for each subscriber device to connect to any other subscriber device at any timing using a smaller number of loopback transmission paths than in the past. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a configuration diagram of an optical communication system according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing a specific example of the functional configuration of a multicast forwarding unit in the first embodiment. [Figure 3] FIG. 3 is a sequence diagram illustrating a processing flow of the optical communication system according to the first embodiment. [Figure 4] FIG. 10 is a block diagram showing a specific example of a functional configuration (part 1) of a multicast forwarding unit in the second embodiment. [Figure 5] FIG. 10 is a block diagram showing a specific example of a functional configuration (part 2) of a multicast forwarding unit in the second embodiment. [Figure 6] FIG. 13 is a block diagram showing a specific example of a functional configuration (part 1) of a multicast forwarding unit in the third embodiment. [Figure 7] FIG. 13 is a block diagram showing a specific example of a functional configuration (part 2) of a multicast forwarding unit in the third embodiment. [Figure 8] FIG. 1 is a diagram illustrating an example of the configuration of an optical communication system including a conventional optical communication device. [Figure 9] FIG. 10 is a diagram for explaining a configuration in which a plurality of optical switches are arranged in parallel. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a configuration diagram of an optical communication system 1 in a first embodiment. The optical communication system 1 includes P optical SWs 10-1 to 10-P (P is an integer equal to or greater than 2), P optical SWs 11-1 to 11-P, a control unit 12, and a multicast forwarding unit 14. In the following description, it is assumed that the optical SWs 10-1 to 10-P are used to transmit optical signals in the upstream direction, and the optical SWs 11-1 to 11-P are used to transmit optical signals in the downstream direction. In the following description, when the optical SWs 10-1 to 10-P are not distinguished, they are simply referred to as optical SW10, and when the optical SWs 11-1 to 11-P are not distinguished, they are simply referred to as optical SW11. The optical SWs 10, 11, control unit 12, and multicast forwarding unit 14 are functional units that constitute one optical communication device.

[0019] The optical SW10 is connected to a plurality of optical transmission paths and outputs an optical signal input from one of the optical transmission paths to another optical transmission path. The optical transmission path is, for example, an optical fiber. The optical SW10 has a plurality of first ports (e.g., n first ports) and a plurality of second ports (e.g., n or more second ports). Each first port of the optical SW10 is connected to an edge node 15 or a subscriber device 16 via a transmission path 18. FIG. 1 shows an example in which the edge node 15 is connected to the optical SW10-1 via an optical transmission path 18-1 and the subscriber device 16-1 is connected via an optical transmission path 18-2. The optical SW10 is one aspect of a first optical switch.

[0020] Of the multiple second ports of the optical SW 10, n second ports are connected to the multicast forwarding unit 14 via n optical transmission paths. The remaining second ports of the multiple second ports of the optical SW 10 may be connected to other devices via optical transmission paths. In the following explanation, for simplicity, it is assumed that the number of first ports and second ports of the optical SW 10 is n.

[0021] The optical SW11 is connected to a plurality of optical transmission lines and outputs an optical signal input from one of the optical transmission lines to another optical transmission line. The optical SW11 has a plurality of first ports (e.g., n first ports) and a plurality of second ports (e.g., n or more second ports). Each first port of the optical SW11 is connected to a subscriber device 16 via a transmission line 18. FIG. 1 shows an example in which a subscriber device 16-2 is connected to the optical SW11-1 via an optical transmission line 18-2, and a subscriber device 16-3 is connected to the optical SW11-P via an optical transmission line 18-3. The optical SW11 is one aspect of a second optical switch.

[0022] Of the multiple second ports of the optical SW11, n second ports are connected to the multicast forwarding unit 14 via n optical transmission paths. The remaining second ports of the multiple second ports of the optical SW11 may be connected to other devices via optical transmission paths. In the following explanation, for simplicity, it is assumed that the number of first ports and second ports of the optical SW11 is n.

[0023] The edge node 15 distributes a signal containing predetermined information to the subscriber device 16. The signal distributed by the edge node 15 is content such as video. The edge node is one aspect of the first device.

[0024] The subscriber device 16 is connected to the optical SW 10 or 11 via an optical access network such as a PON (Passive Optical Network). The subscriber device 16 includes an optical transceiver. The optical transceiver is an example of an optical transmitter and an optical receiver in the subscriber device 16. The optical transceiver is a wavelength-tunable optical transmitter / receiver. In this case, the subscriber device 16 can communicate at any wavelength. The optical transceiver may be an optical transceiver with an AMCC (Auxiliary Management and Control Channel) function. In this case, the wavelength used by the subscriber device 16 is controlled via a control signal superimposed by the AMCC. The subscriber device 16 is one aspect of the first device and the second device.

[0025] The control unit 12 is connected to the second ports of the optical SWs 10 and 11 via optical transmission paths. The control unit 12 includes a wavelength management control unit 121 and an optical SW control unit 122. The wavelength management control unit 121 assigns wavelengths to the edge node 15 and each subscriber device 16. When the wavelength management control unit 121 assigns wavelengths to the edge node 15 and each subscriber device 16, the optical SW control unit 122 switches the paths between the ports of the optical SW 10 or 11 so that the edge node 15 and the subscriber device 16 are connected to the wavelength management control unit 121.

[0026] The optical SW control unit 122 switches the connection between ports of the optical SW 10 and the connection between ports of the optical SW 11. For example, the optical SW control unit 122 switches the connection between ports of the optical SW 10 and the optical SW 11 so that the edge node 15 or the subscriber device 16 can communicate with a desired subscriber device 16.

[0027] The control unit 12 stores a management table. The management table includes information for identifying the edge node 15 or the subscriber device 16, information on the wavelengths assigned to the edge node 15 and each subscriber device 16, and information on the optical SW 10 or 11 to which the edge node 15 or the subscriber device 16 is connected (for example, information on the port to which the edge node 15 or the subscriber device 16 is connected). The control unit 12 is composed of one or more processors.

[0028] The multicast forwarding unit 14 receives as input the optical signal output from the optical SW 10, and forwards the input optical signal by multicast to at least the optical SW 11 connected to the destination subscriber device 16. Since n optical transmission paths are connected from one optical SW 10 to the multicast forwarding unit 14, nP upstream optical transmission paths are connected to the multicast forwarding unit 14. Furthermore, since n optical transmission paths are connected from one optical SW 11 to the multicast forwarding unit 14, nP downstream optical transmission paths are connected to the multicast forwarding unit 14.

[0029] When multicast communication spanning optical SW10 is performed, the optical SW control unit 122 switches the path between ports of the optical SW10 so that the output destination of the optical signal from the optical SW10 is connected to the multicast forwarding unit 14. The multicast forwarding unit 14 controls so that the input optical signal is output to the desired optical SW 11. This configuration realizes return communication between any optical SWs while limiting the number of wirings required for return in each optical SW to n. Note that although the present invention will be described using multicast communication as an example, it is also applicable to simple return communication. For example, it is also applicable to a case where an optical signal transmitted from a subscriber device 16-1 connected to the optical SW10 is forwarded to a subscriber device 16 connected to the optical SW11.

[0030] When the multicast forwarding unit 14 is implemented in a single device, a WSS (Wavelength Selective Switch) with nP x nP ports is used. However, when nP is large, it is difficult to implement a WSS with nP x nP ports, and this leads to an increase in cost. For this reason, the following explanation also covers the case where the multicast forwarding unit 14 is configured with multiple devices.

[0031] FIG. 2 is a block diagram showing a specific example of the functional configuration of the multicast forwarding unit 14 in the first embodiment. The multicast forwarding unit 14 includes a coupler 141, an amplifier 142, a coupler 143, a forwarding wavelength control unit 144, and a plurality of wavelength-tunable filters 145-1 to 145-nP. The coupler 141 is connected to n optical transmission lines (a total of nP optical transmission lines) connected to the second ports of the optical SW10, and receives as input an optical signal transmitted through any of the nP optical transmission lines. The coupler 141 multiplexes and outputs the input optical signals. The number of ports required for the coupler 141 is n×P. The coupler 141 is one aspect of the first demultiplexing unit.

[0032] The amplifier 142 amplifies the optical signal output from the coupler 141 .

[0033] The coupler 143 branches and outputs the optical signal amplified by the amplifier 142. The number of ports required for the coupler 143 is n×P. The coupler 143 is one aspect of the second demultiplexing unit.

[0034] The forwarding wavelength control unit 144 sets wavelengths to be transmitted through the tunable filters 145-1 to 145-nP in accordance with instructions from the control unit 12. Specifically, when the control unit 12 instructs the forwarding wavelength control unit 144 on wavelengths to be transmitted during multicast communication, the forwarding wavelength control unit 144 sets the specified wavelengths to the tunable filters 145-1 to 145-nP. This allows the tunable filters 145-1 to 145-nP to transmit optical signals of the set wavelengths. The forwarding wavelength control unit 144 may be implemented in the control unit 12.

[0035] The wavelength-tunable filters 145-1 to 145-nP are provided on nP optical transmission paths connecting the coupler 143 and the second ports of the optical SW11, and transmit optical signals of wavelengths set by the transfer wavelength control unit 144 (hereinafter referred to as "set wavelengths").

[0036] Fig. 3 is a sequence diagram for explaining the processing flow of the optical communication system 1 in the first embodiment. Fig. 3 explains a case where an optical signal transmitted from the subscriber device 16-1 connected to the optical SW10-1 shown in Fig. 1 is multicast to the subscriber device 16-2 connected to the optical SW11-1 and the subscriber device 16-3 connected to the optical SW11-P. Here, it is assumed that the wavelength λ1 is assigned to the subscriber devices 16-1, 16-2, and 16-3. Note that the optical SW11-P and the subscriber device 16-3 are not shown in Fig. 3.

[0037] The forwarding wavelength control unit 144 sets the wavelength tunable filters 145-1 to 145-nP to transmit an optical signal of wavelength λ1 (step S101). The subscriber device 16-1 transmits an optical signal of wavelength λ1 (step S102). The optical signal of wavelength λ1 transmitted from the subscriber device 16-1 is input to the first port of the optical SW10-1 via the optical transmission line 18-2.

[0038] The optical SW10-1 is controlled by the optical SW control unit 122 so as to connect the route between the first port of the optical SW10-1 to which the subscriber device 16-1 is connected and the second port of the optical SW10-1 to which the multicast forwarding unit 14 is connected. As a result, the optical signal of wavelength λ1 input to the first port of the optical SW10-1 is output from the second port to the multicast forwarding unit 14 (step S103).

[0039] The optical signal with wavelength λ1 output from optical SW10-1 is input to coupler 141 (step S104). Coupler 141 multiplexes the input optical signals and outputs the multiplexed signal (step S105). The optical signal output from coupler 141 is amplified by amplifier 142 (step S106). The optical signal amplified by amplifier 142 is input to coupler 143.

[0040] The coupler 143 branches the input optical signal to each connected optical transmission path (step S107). The optical signals branched to each optical transmission path are input to the wavelength-tunable filters 145-1 to 145-nP. Here, since the wavelength λ1 is set as the set wavelength, the optical signals with wavelength λ1 are output from the wavelength-tunable filters 145-1 to 145-nP. The optical signals with wavelength λ1 output from the wavelength-tunable filters 145-1 to 145-nP are input to the second ports of the optical SW11-1 and 11-P via the optical transmission paths.

[0041] The optical SW11-1 is controlled by the optical SW control unit 122 so that the path between the first port of the optical SW11-1 to which the subscriber device 16-2 is connected and the second port of the optical SW11-1 to which the multicast forwarding unit 14 is connected is connected. As a result, the optical signal of wavelength λ1 input to the second port of the optical SW11-1 is output from the first port to the subscriber device 16-2 via the optical transmission line 18-3 (step S109). The subscriber device 16-2 receives the optical signal of wavelength λ1 output from the optical SW11-1 (step S110).

[0042] The optical SW11-P is controlled by the optical SW control unit 122 so that the path between the first port of the optical SW11-P, to which the subscriber device 16-3 is connected, and the second port of the optical SW11-P, to which the multicast forwarding unit 14 is connected, is connected. As a result, the optical signal of wavelength λ1 input to the second port of the optical SW11-P is output from the first port to the subscriber device 16-3 via the optical transmission line 18-4. The subscriber device 16-3 receives the optical signal of wavelength λ1 output from the optical SW11-P.

[0043] According to the optical communication system 1 configured as above, when multicast communication is performed in the optical communication system 1 including the multiple optical SWs 10 and 11, the number of wirings required for return at each optical SW can be reduced to n. Therefore, it becomes possible for each subscriber device to connect to any other subscriber device at any timing using a smaller number of return transmission paths than conventionally.

[0044] (Modification of the first embodiment) The coupler 141 may be replaced with a WSS or a circular AWG (Arrayed Waveguide Gratings). When configured in this manner, the WSS is connected to n optical transmission lines (a total of nP optical transmission lines) connected to the second port of each optical SW10, and outputs an optical signal of a set wavelength from among the optical signals transmitted via a certain optical transmission line. The WSS is a wavelength-selective optical switch. The number of ports required for the WSS is n×P.

[0045] The AWG is connected to n optical transmission lines (a total of nP optical transmission lines) connected to the second ports of each optical SW 10, and inputs the optical signals output from each optical SW 10 through a path corresponding to the wavelength. The AWG outputs the input optical signals to the amplifier 142. The number of ports required for the AWG is n×P.

[0046] (Second embodiment) In the second embodiment, the system configuration of the optical communication system 1 is the same as in the first embodiment, but differs only in the configuration of the multicast forwarding unit 14. Therefore, the differences from the first embodiment will be described below.

[0047] FIG. 4 is a block diagram showing a specific example of the functional configuration (part 1) of the multicast forwarding unit 14a in the second embodiment. The multicast forwarding unit 14a includes a plurality of couplers 141-1 to 141-X (X is an integer equal to or greater than 2), an amplifier 142, a plurality of couplers 143-1 to 143-X, a forwarding wavelength control unit 144a, a plurality of wavelength-tunable filters 145-1-1 to 145-1-nP / X, 145-X-1 to 145-X-nP / X, a plurality of upper couplers 146-1 to 146-2, a plurality of amplifiers 147-1 to 147-X, and a plurality of amplifiers 148-1 to 148-X.

[0048] In the example shown in FIG. 4, coupler 141-x (1≦x≦X) is connected to upstream coupler 146-1 via amplifier 147-x, coupler 143-x is connected to upstream coupler 146-2 via amplifier 148-x, and upstream couplers 146-1 and 146-2 are connected via amplifier 142.

[0049] The coupler 141-x is connected to nP / X different optical transmission lines out of the n optical transmission lines (nP optical transmission lines in total) connected to the second port of each optical SW10, and receives an optical signal transmitted through any of the nP / X optical transmission lines as input. The coupler 145-x multiplexes the input optical signals and outputs the multiplexed optical signals. In this way, approximately the same number of optical transmission lines are connected to each coupler 145 on average. For example, if there are two couplers 145 (X=2), three optical SW10 (P=3), and the number of optical transmission lines connected to the second port of each optical SW10 is two (n=2), three different optical transmission lines are connected to each coupler 145.

[0050] The amplifier 147-x amplifies the optical signal output from the coupler 141-x.

[0051] The upstream coupler 146-1 multiplexes the optical signals amplified by the amplifiers 147 and outputs the multiplexed signals.

[0052] The upstream coupler 146-2 branches the optical signal output from the upstream coupler 146-1 and amplified by the amplifier 142.

[0053] The amplifier 148-x amplifies the optical signal output from the upstream coupler 146-2.

[0054] The coupler 143-x branches and outputs the optical signal amplified by the amplifier 148-x.

[0055] The wavelength tunable filters 145-1-1 to 145-1-nP / X are provided on nP / X optical transmission lines connecting the coupler 143-1 and the second ports of the optical SW11, and transmit optical signals of set wavelengths.

[0056] The wavelength tunable filters 145-X-1 to 145-X-nP / X are provided on nP / X optical transmission lines connecting the coupler 143-X and the second ports of the optical SW11, and transmit optical signals of set wavelengths.

[0057] The transfer wavelength control unit 144a sets wavelengths to be transmitted by the wavelength tunable filters 145-1-1 to 145-1-nP / X and 145-X-1 to 145-X-nP / X in accordance with instructions from the control unit 12. The transfer wavelength control unit 144a may be implemented in the control unit 12.

[0058] According to the optical communication system 1 of the second embodiment configured as described above, X couplers 141 and couplers 143 are arranged in parallel, and an upper coupler 146 is arranged above each of the parallel-arranged couplers 141 and couplers 143. With this configuration, it is possible to reduce the number of ports required per coupler compared to the first embodiment.

[0059] (Modification of the second embodiment) The multicast forwarding unit 14a may have the configuration shown in Fig. 5. Fig. 5 is a block diagram showing a specific example of a functional configuration (part 2) of the multicast forwarding unit 14a in the second embodiment. The multicast forwarding unit 14a includes a plurality of couplers 141-1 to 141-X, an amplifier 142, a plurality of upper couplers 146-1 to 146-2, a plurality of amplifiers 147-1 to 147-X, a plurality of amplifiers 148-1 to 148-P, and a plurality of WSSs 149-1 to 149-P.

[0060] In the example shown in FIG. 5, couplers 141-1 to 141-X are connected to upstream coupler 146-1 via amplifiers 147-1 to 147-X, respectively, WSSs 149-1 to 149-P are connected to upstream coupler 146-2 via amplifiers 148-1 to 148-P, respectively, and upstream couplers 146-1 and 146-2 are connected via amplifier 142.

[0061] 5 differs from the configuration shown in Fig. 4 in that the control target of the transfer wavelength control unit 144a is the WSS 149, and in that a plurality of WSSs 149-1 to 144-P are newly provided instead of the plurality of couplers 143-1 to 143-X. The coupler 141, amplifier 142, amplifier 147, upper coupler 146, and amplifier 148 perform the same processes as the functional units with the same names shown in Fig. 4, and therefore their explanations will be omitted.

[0062] The transfer wavelength control unit 144a sets the wavelength to be output by the WSS 149 in accordance with instructions from the control unit 12. Specifically, when the control unit 12 instructs the transfer wavelength control unit 144a on the wavelength to be transferred during multicast communication, the transfer wavelength control unit 144a sets the specified wavelength to the WSS 149. This allows the WSS 149 to output an optical signal with the set wavelength.

[0063] The WSS 149-p (1≦p≦P) is connected to n different optical transmission lines among the n optical transmission lines (a total of nP optical transmission lines) connected to the second port of each optical SW11, and outputs the optical signal amplified by the amplifier 148-p to the optical transmission line that serves as the output path of the set wavelength. The WSS 149-p is one aspect of the second demultiplexing unit. The configuration shown in Figure 5 makes it possible to omit the wavelength tunable filter. However, WSS 149-p can only output any wavelength from one port. Therefore, it is necessary to prevent one WSS 149-p from connecting to multiple optical SW11s. When multicasting within one optical SW11, it is necessary to receive the wavelength to be multicast and then branch it within that optical SW11.

[0064] (Third embodiment) In the third embodiment, the system configuration of the optical communication system 1 is the same as in the first embodiment, but differs only in the configuration of the multicast forwarding unit 14. Therefore, the differences from the first embodiment will be described below.

[0065] FIG. 6 is a block diagram showing a specific example of a functional configuration (part 1) of the multicast forwarding unit 14b in the third embodiment. The multicast forwarding unit 14b includes a plurality of couplers 141-1 to 141-X, a plurality of amplifiers 142-1-1 to 142-XX, a plurality of couplers 143-1 to 143-X, a forwarding wavelength control unit 144b, a plurality of wavelength-tunable filters 145-1-1 to 145-1-nP / X, 145-X-1 to 145-X-nP / X, a plurality of upper couplers 146-1-1 to 146-1-X, a plurality of upper couplers 146-2-1 to 146-2-X, a plurality of amplifiers 147-1 to 147-X, and a plurality of amplifiers 148-1 to 148-X.

[0066] In the example shown in FIG. 6, coupler 141-x is connected to upstream coupler 146-1-x via amplifier 147-x, coupler 143-x is connected to upstream coupler 146-2-x via amplifier 148-x, and upstream couplers 146-1 and 146-2 are connected via amplifier 142.

[0067] The coupler 141-x is connected to different nP / X optical transmission lines among the n optical transmission lines (a total of nP optical transmission lines) connected to the second port of each optical SW10, and receives an optical signal transmitted through any of the nP / X optical transmission lines as input. The coupler 141-x multiplexes the input optical signals and outputs the combined signal.

[0068] The amplifier 147-x amplifies the optical signal output from the coupler 141-x.

[0069] The upstream coupler 146-1-x branches and outputs the optical signal amplified by the amplifier 147-x.

[0070] The upstream coupler 146-2-x multiplexes the optical signals output from the upstream couplers 146-1 and amplified by the amplifiers 142 connected thereto.

[0071] The amplifier 148-x amplifies the optical signal output from the upstream coupler 146-2-x.

[0072] The coupler 143-x branches and outputs the optical signal amplified by the amplifier 148-x.

[0073] The wavelength tunable filters 145-1-1 to 145-1-nP / X are provided on nP / X optical transmission lines connecting the coupler 143-1 and the second ports of the optical SW11, and transmit optical signals of set wavelengths.

[0074] The wavelength tunable filters 145-X-1 to 145-X-nP / X are provided on nP / X optical transmission lines connecting the coupler 143-X and the second ports of the optical SW11, and transmit optical signals of set wavelengths.

[0075] The transfer wavelength control unit 144b sets wavelengths to be transmitted by the wavelength tunable filters 145-1-1 to 145-1-nP / X and 145-X-1 to 145-X-nP / X in accordance with instructions from the control unit 12. The transfer wavelength control unit 144b may be implemented in the control unit 12.

[0076] According to the optical communication system 1 of the third embodiment configured as described above, in addition to the X couplers 141 and 143, X upper-level couplers 146-1 and 146-2 are also arranged in parallel. In the second embodiment, it was necessary to aggregate a maximum of nP wavelengths in the upper-level coupler 146. In contrast, in the third embodiment, the maximum number of wavelengths that can be accommodated by all couplers is nP / X, making it possible to reduce the number of wavelengths that must be accommodated by one coupler.

[0077] (Modification of the third embodiment) The multicast forwarding unit 14b may have the configuration shown in Fig. 7. Fig. 7 is a block diagram showing a specific example of a functional configuration (part 2) of the multicast forwarding unit 14b in the third embodiment. The multicast forwarding unit 14b includes a plurality of couplers 141-1 to 141-X, a plurality of amplifiers 142-1-1 to 142-XX, a forwarding wavelength control unit 144b, a plurality of upstream couplers 146-1-1 to 146-1-X, a plurality of upstream couplers 146-2-1 to 146-2-X, a plurality of amplifiers 147-1 to 147-X, a plurality of amplifiers 148-1 to 148-X, and a plurality of WSSs 149-1 to 149-X.

[0078] In the example shown in Fig. 7, coupler 141-x is connected to upstream coupler 146-1-x via amplifier 147-x, WSS 149-x is connected to upstream coupler 146-2-x via amplifier 148-x, and upstream coupler 146-1 and upstream coupler 146-2 are connected via amplifier 142. The configuration shown in Fig. 7 differs from the configuration shown in Fig. 6 in that the WSS 149 is controlled by the forwarding wavelength control unit 144b and in that multiple WSSs 149-1 to 149-X are newly provided instead of the multiple couplers 143-1 to 143-X. The coupler 141, amplifier 142, amplifier 147, upstream coupler 146, and amplifier 148 perform the same processes as the functional units with the same names shown in Fig. 6, and therefore their descriptions will be omitted.

[0079] WSS149-x is connected to n different optical transmission paths out of the n optical transmission paths (a total of nP optical transmission paths) connected to the second port of each optical SW11, and outputs the optical signal amplified by amplifier 148-x to the optical transmission path that serves as the output path for the set wavelength.

[0080] The transfer wavelength control unit 144b sets the wavelength to be output by the WSS 149 in accordance with an instruction from the control unit 12. Specifically, when the control unit 12 instructs the transfer wavelength control unit 144b on the wavelength to be transferred during multicast communication, the transfer wavelength control unit 144b sets the specified wavelength to the WSS 149. This allows the WSS 149 to output an optical signal with the set wavelength.

[0081] (Modifications common to the first to third embodiments) In each of the above embodiments, the optical SW is divided into the upstream and downstream directions, but the same optical SW may be used for both the upstream and downstream directions.

[0082] In each of the above embodiments, the optical SW 10, the optical SW 11, or the multicast forwarding units 14, 14a, and 14b are provided in one optical communication device. However, any of the optical SW 10, the optical SW 11, and the multicast forwarding units 14, 14a, and 14b may be implemented in another device.

[0083] Some of the functional units (e.g., the control unit 12, the multicast forwarding units 14, 14a, and 14b) of the optical communication device in the above-described embodiment may be realized by a computer. In this case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0084] Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or over communication lines like telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within the computer systems that serve as servers or clients. Furthermore, the programs may be programs that implement some of the aforementioned functions, or may be programs that can realize the aforementioned functions in combination with programs already stored in the computer system, or may be programs that are implemented using programmable logic devices such as FPGAs.

[0085] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0086] The present invention can be applied to optical communication system technology that performs loopback communication via an optical SW. [Explanation of symbols]

[0087] 10-1 to 10-P, 11-1 to 11-P...optical switches, 12...control unit, 121...wavelength management control unit, 122...optical switch control unit, 14, 14a, 14b...multicast forwarding unit, 15...edge node, 16-1 to 16-3...subscriber device, 141, 141-1 to 141-X, 143, 143-1 to 143-X...coupler, 142, 142-1-1 to 142-XX, 147-1 to 147-X, 148-1 to 148-X, 148-1 to 148-P...amplifier, 144, 144a, 144b...transfer wavelength control unit, 145-1 to 145-nP...wavelength tunable filter, 146-1, 146-2, 146-1-1 to 146-1-X, 146-2-1 to 146-2-X... Upper coupler, 149-1 to 149-P, 149-1 to 149-X... WSS

Claims

1. a first optical switch connected to a plurality of optical transmission lines and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a second optical switch connected to a plurality of optical transmission lines and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a multicast forwarding unit that multicasts an optical signal transmitted from a first device connected to the first optical switch to one or more second devices connected to the second optical switch; Equipped with the multicast forwarding unit returns the optical signal forwarded from the first optical switch to one or more second devices connected to the second optical switch and forwards the optical signal by multicast; The multicast forwarding unit one or more first demultiplexing units that multiplex and output optical signals transmitted from first devices connected to the first optical switch; one or more second demultiplexing units that branch the optical signal output from the first demultiplexing unit or an optical signal based on the optical signal output from the first demultiplexing unit, and output the branched optical signal to an optical transmission line to which the second optical switch is connected; An optical communication device comprising:

2. The multicast forwarding unit a plurality of wavelength-tunable filters provided on the optical transmission lines connecting the one or more second demultiplexing units and the second optical switch, the wavelength-tunable filters transmitting optical signals of predetermined wavelengths; a transfer wavelength control unit that sets wavelengths to be transmitted by the plurality of wavelength tunable filters; Furthermore, the transfer wavelength control unit sets wavelengths used for communication between the first device and the second device in the plurality of wavelength tunable filters.

2. The optical communication device according to claim 1.

3. the one or more second demultiplexing units are wavelength selective optical switches, The multicast forwarding unit a transfer wavelength control unit that sets wavelengths to be output from the one or more second demultiplexing units; Furthermore, the transfer wavelength control unit sets wavelengths used for communication between the first device and the second device in the one or more second multiplexing / demultiplexing units.

2. The optical communication device according to claim 1.

4. the one or more first demultiplexing units are a plurality of first demultiplexing units, the one or more second demultiplexing units are a plurality of second demultiplexing units, one or more upper-level first demultiplexers that multiplex and output the plurality of optical signals output from the plurality of first demultiplexers; one or more upper-level second demultiplexers that split the optical signal output from the upper-level first demultiplexer and output the split optical signal to each of the plurality of second demultiplexers; Further provided with The optical communication device according to claim 1 .

5. the one or more first demultiplexing units are a plurality of first demultiplexing units, the one or more second demultiplexing units are a plurality of second demultiplexing units, a plurality of higher-order first demultiplexing units that branch and output the optical signals output from the plurality of first demultiplexing units; a plurality of upper second demultiplexing units that multiplex the optical signals output from the plurality of upper first demultiplexing units and output the multiplexed optical signals to the plurality of second demultiplexing units, respectively; Further provided with The optical communication device according to claim 1 .

6. a first optical switch connected to a plurality of optical transmission lines and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a second optical switch connected to a plurality of optical transmission lines and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a multicast forwarding unit that multicasts an optical signal transmitted from a first device connected to the first optical switch to one or more second devices connected to the second optical switch; Equipped with the multicast forwarding unit returns the optical signal forwarded from the first optical switch to one or more second devices connected to the second optical switch and forwards the optical signal by multicast; The multicast forwarding unit one or more first demultiplexing units that multiplex and output optical signals transmitted from first devices connected to the first optical switch; one or more second demultiplexing units that branch the optical signal output from the first demultiplexing unit or an optical signal based on the optical signal output from the first demultiplexing unit, and output the branched optical signal to an optical transmission line to which the second optical switch is connected; An optical communication system comprising:

7. a first optical switch connected to a plurality of optical transmission lines, and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a second optical switch connected to a plurality of optical transmission lines, and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a multicast forwarding unit that multicasts an optical signal transmitted from a first device connected to the first optical switch to one or more second devices connected to the second optical switch; the multicast forwarding unit returns the optical signal forwarded from the first optical switch to one or more second devices connected to the second optical switch and forwards it by multicast; one or more first demultiplexing units included in the multicast forwarding unit multiplex and output optical signals transmitted from first devices connected to the first optical switch; A transfer method in which one or more second multiplexing / demultiplexing units provided in the multicast transfer unit branch off the optical signal output from the first multiplexing / demultiplexing unit or an optical signal based on the optical signal output from the first multiplexing / demultiplexing unit, and output it to an optical transmission path to which the second optical switch is connected.

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