Optical communication device, optical communication system, and transfer method

Abstract

The present invention provides an optical communication device provided with: a plurality of first distribution units that are connected to a plurality of optical transmission paths and that output an optical signal input from one of first devices to one of the optical transmission paths; a plurality of second distribution units that are connected to a plurality of optical transmission paths and that output an optical signal input from one of the optical transmission paths to one of second devices; and a multicast transfer unit that transfers, by multicast, an optical signal transmitted from the first device connected to one of the plurality of first distribution units to one of the plurality of second distribution units to which one or more of the second devices have been connected.　

Description

[Technical Field]

[0001] The present invention relates to an optical communication device, an optical communication system, and a transfer method. This application claims priority to PCT / JP2021 / 037734, filed in Japan on October 12, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] Conventionally, optical communication devices have been proposed that can relay optical signals according to their destinations while reducing delay (see, for example, Patent Document 1). Fig. 16 is a diagram showing an example of the configuration of an optical communication system 100 that includes a conventional optical communication device. The optical communication system 100 includes an optical SW 110 that configures the optical communication device, and a control unit 115. 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. 16 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. 16, 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. 16 , 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. 16, by arranging multiple optical SWs 110-1 to 110-P (P is an integer equal to or greater than 2) in parallel at one point, the maximum number of users that can transmit to each direction can be increased. Fig. 17 is a diagram for explaining a configuration in which multiple optical SWs 110 are arranged in parallel. The example shown in Fig. 17 shows a configuration in which 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 conceivable 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 need 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. This problem is not limited to optical communication systems equipped with optical SWs, but is a common issue when performing return communication in optical communication systems equipped with an optical distribution unit that has the function of distributing input optical signals to other devices.

[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 distribution units. [Means for solving the problem]

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

[0014] One aspect of the present invention is an optical communication system comprising a plurality of first distribution units connected to a plurality of optical transmission paths and outputting an optical signal input from any of the first devices to any of the optical transmission paths, a plurality of second distribution units connected to a plurality of optical transmission paths and outputting an optical signal input from any of the optical transmission paths to any of the second devices, and a multicast forwarding unit that multicasts an optical signal transmitted from the first device connected to any of the plurality of first distribution units to any of the plurality of second distribution units to which one or more of the second devices are connected.

[0015] One aspect of the present invention is a transfer method in which a plurality of first distribution units are connected to a plurality of optical transmission paths and output an optical signal input from any of the first devices to any of the optical transmission paths, and a plurality of second distribution units are connected to a plurality of optical transmission paths and output an optical signal input from any of the optical transmission paths to any of the second devices, and an optical signal transmitted from a first device connected to any of the plurality of first distribution units is transferred by multicast to any of the plurality of second distribution units to which one or more of the second devices are connected. [Effects of the Invention]

[0016] According to the present invention, when performing return communication in an optical communication system having multiple optical distribution units, 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 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. 10 is a configuration diagram of an optical communication system according to a fourth embodiment. [Figure 9] FIG. 10 is a sequence diagram illustrating a processing flow of an optical communication system according to a fourth embodiment. [Figure 10] FIG. 11 is a configuration diagram of an optical communication system according to a modified example of the fourth embodiment. [Figure 11] FIG. 10 is a configuration diagram of an optical communication system according to a fifth embodiment. [Figure 12] FIG. 13 is a block diagram showing a specific example of a functional configuration (part 1) of a multicast forwarding unit in a modified example of the fifth embodiment. [Figure 13] FIG. 13 is a block diagram showing a specific example of a functional configuration (part 2) of a multicast forwarding unit in a modified example of the fifth embodiment. [Figure 14] FIG. 13 is a block diagram showing a specific example of a functional configuration (part 3) of a multicast forwarding unit in a modified example of the fifth embodiment. [Figure 15] FIG. 10 is a configuration diagram of an optical communication system according to a sixth embodiment. [Figure 16] FIG. 1 is a diagram illustrating an example of the configuration of an optical communication system including a conventional optical communication device. [Figure 17] 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 the optical transmission path 18-1 and the subscriber device 16-1 is connected via the optical transmission path 18-2. The optical SW10 is one aspect of a first optical distribution unit.

[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 the optical transmission line 18-2, and a subscriber device 16-3 is connected to the optical SW11-P via the optical transmission line 18-3. The optical SW11 is one aspect of a second optical distribution unit.

[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. The optical SW control unit 122 is one aspect of an optical distribution control unit.

[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 141-x multiplexes the input optical signals and outputs the multiplexed optical signals. In this way, on average, approximately the same number of optical transmission lines are connected to each coupler 141. For example, if there are two couplers 141 (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 141.

[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] (Fourth embodiment) In the first to third embodiments described above, a configuration using optical SWs was described as an upstream optical distribution unit and a downstream optical distribution unit connected to a multicast forwarding unit. In the fourth embodiment, an upstream optical distribution unit and a downstream optical distribution unit that are different from those in the first to third embodiments will be described. In the fourth embodiment, the system configuration of the optical communication system 1 is the same as in the first embodiment, but the configuration of the optical distribution unit is different. Therefore, the differences from the first embodiment will be described below.

[0082] 8 is a configuration diagram of an optical communication system 1 in the fourth embodiment. The optical communication system 1 in the fourth embodiment includes P optical distribution units 30-1 to 30-P, P optical distribution units 40-1 to 40-P, a control unit 12 (not shown), and a multicast forwarding unit 14. In the following explanation, it is assumed that the optical distribution units 30-1 to 30-P are used for transmitting optical signals in the upstream direction, and the optical distribution units 40-1 to 40-P are used for transmitting optical signals in the downstream direction.

[0083] The light distribution units 30-1 to 30-P have the same configuration. The light distribution units 40-1 to 40-P have the same configuration. In the following description, when the light distribution units 30-1 to 30-P do not need to be distinguished, they will simply be referred to as the light distribution unit 30, and when the light distribution units 40-1 to 40-P do not need to be distinguished, they will simply be referred to as the light distribution unit 40. The light distribution units 30, 40, control unit 12, and multicast forwarding unit 14 are functional units that constitute one optical communication device. The light distribution units 30 and 40 are multicast switches (MCS).

[0084] The optical distribution unit 30 includes a plurality of 1×M optical switches 31 and a plurality of signal multiplexing units 32. The number of 1×M optical switches 31 and the number of signal multiplexing units 32 may be the same or different. The optical distribution unit 30 is one aspect of a first optical distribution unit. Each 1×M optical switch 31 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. Each 1×M optical switch 31 has one first port and M second ports (M is an integer equal to or greater than 2). The one first port of each 1×M optical switch 31 is connected to an edge node 15 or a subscriber device 16 via an optical transmission path.

[0085] One second port out of the M second ports that each 1×M optical switch 31 has is connected to the multicast forwarding unit 14 via an optical transmission path. The remaining second ports (for example, (M−1) second ports) of the M second ports that each 1×M optical switch 31 has are connected to different signal multiplexing units 32 via optical transmission paths. Note that some of the remaining second ports out of the M second ports that each 1×M optical switch 31 has may not be connected to the signal multiplexing unit 32.

[0086] The signal multiplexing unit 32 is either an optical coupler, a wavelength selective switch, or an AWG. The signal multiplexing unit 32 multiplexes the optical signals output from each 1×M optical switch 31, and outputs the multiplexed signals to another device via an optical transmission line.

[0087] The optical distribution unit 40 includes a plurality of signal separation units 41 and a plurality of 1×M optical switches 42. The number of signal separation units 41 and the number of 1×M optical switches 42 may be the same or different. The optical distribution unit 40 is one aspect of a second optical distribution unit. The signal separation unit 41 is either an optical coupler, a wavelength selective switch, or an AWG. The signal separation unit 41 receives an optical signal transmitted from another device connected via an optical transmission line. The signal separation unit 41 branches or demultiplexes the input optical signal and outputs it to each 1×M optical switch 42. For example, if the optical distribution unit 40 is an optical coupler, the optical coupler branches the input optical signal and outputs it to each connected 1×M optical switch 42. For example, if the optical distribution unit 40 is a wavelength selective switch or an AWG, the wavelength selective switch or AWG demultiplexes the input optical signal and outputs it to the 1×M optical switch 42 connected to the port of the corresponding wavelength.

[0088] Each 1×M optical switch 42 is connected to multiple optical transmission lines and outputs an optical signal input from one of the optical transmission lines to another optical transmission line. Each 1×M optical switch 42 has one first port and M second ports. The one first port of each 1×M optical switch 42 is connected to a subscriber device 16 via an optical transmission line.

[0089] One second port out of the M second ports that each 1×M optical switch 42 has is connected to the multicast forwarding unit 14 via an optical transmission path. The remaining second ports (for example, (M−1) second ports) of the M second ports that each 1×M optical switch 42 has are connected to different signal demultiplexers 41 via optical transmission paths. Note that some of the remaining second ports out of the M second ports that each 1×M optical switch 42 has may not be connected to the signal demultiplexer 41.

[0090] An amplifier may be installed to compensate for signal loss. The amplifier may be installed in any or all of the following locations: on the optical transmission line connected to the first port of each of the 1×M optical switches 31 and 42; on the optical transmission line between each of the 1×M optical switches 31 and each of the signal multiplexing units 32; on the optical transmission line between each of the signal demultiplexing units 41 and each of the 1×M optical switches 42; on the optical transmission line on the output side of each of the signal multiplexing units 32 (the side opposite to the side connected to the 1×M optical switch 31); and on the optical transmission line on the input side of each of the signal demultiplexing units 41 (the side opposite to the side connected to the 1×M optical switch 42).

[0091] The multicast forwarding unit 14 receives as input the optical signal output from the 1×M optical switch 31 and forwards the input optical signal by multicast to at least the 1×M optical switch 42 to which the destination subscriber device 16 is connected. One optical transmission path is connected from one 1×M optical switch 31 to the multicast forwarding unit 14. Therefore, if one optical distribution unit 30 is equipped with n 1×M optical switches 31, n optical transmission paths are connected from one optical distribution unit 30 to the multicast forwarding unit 14, and since there are P optical distribution units 30, nP upstream optical transmission paths are connected to the multicast forwarding unit 14. Furthermore, if one optical distribution unit 40 is equipped with n 1×M optical switches 42, n optical transmission paths are connected from one optical distribution unit 40 to the multicast forwarding unit 14, and since there are P optical distribution units 40, nP downstream optical transmission paths are connected to the multicast forwarding unit 14.

[0092] When multicast communication spanning the optical distribution unit 30 is performed, the optical SW control unit 122 switches the path between the ports of the 1×M optical switch 31 so that the output destination of the optical signal from the 1×M optical switch 31 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 1×M optical switch 42. With this configuration, return communication between any 1×M optical switches is realized while limiting the number of wiring required for return at each 1×M optical switch to nP.

[0093] The configuration of the multicast forwarding unit 14 may be any of the configurations shown in the first to third embodiments. That is, the configuration of the multicast forwarding unit 14 may be any of the configurations shown in Fig. 2, and Figs. 4 to 7.

[0094] In the fourth embodiment, the optical SW control unit 122 switches the connection between ports of the 1×M optical switch 31 and the connection between ports of the 1×M optical switch 42. Specifically, in the fourth embodiment, the optical SW control unit 122 switches the connection between ports for each 1×M optical switch 31 included in each light distribution unit 30, and switches the connection between ports for each 1×M optical switch 42 included in each light distribution unit 40.

[0095] For example, the optical SW control unit 122 switches the connection between ports so as to connect the first port of the 1×M optical switch 31, to which the edge node 15 or the subscriber device 16 is connected, with the second port, to which the multicast forwarding unit 14 is connected. The 1×M optical switch 31 outputs the optical signal transmitted from the edge node 15 or the subscriber device 16 connected to the first port, from the second port, to which the multicast forwarding unit 14 is connected. As a result, the optical signal input to the first port of the 1×M optical switch 31 is directly input to the multicast forwarding unit 14.

[0096] Similarly, the optical SW control unit 122 switches the connection between the ports so that the first port of the 1×M optical switch 42 to which the desired subscriber device 16 is connected is connected to the second port to which the multicast forwarding unit 14 is connected. The optical signal forwarded from the multicast forwarding unit 14 is input to the second port of the 1×M optical switch 42. The 1×M optical switch 42 receives the optical signal forwarded from the multicast forwarding unit 14 connected to the second port, and outputs the input optical signal from the first port. As a result, the optical signal output from the multicast forwarding unit 14 is forwarded to the desired subscriber device 16.

[0097] 9 is a sequence diagram for explaining the processing flow of the optical communication system 1 in the fourth embodiment. FIG. 9 illustrates a case where an optical signal transmitted from the subscriber device 16-1 connected to the optical distribution unit 30-1 is multicast to the subscriber device 16-2 connected to the optical distribution unit 40-1 and the subscriber device 16-3 connected to the optical distribution unit 40-P. Here, it is assumed that a wavelength λ1 is assigned to the subscriber devices 16-1, 16-2, and 16-3. Note that the optical distribution unit 40-P and the subscriber device 16-3 are not shown in FIG. 9. Furthermore, the configuration of the multicast forwarding unit 14 will be explained using the configuration shown in FIG. 2 as an example.

[0098] The forwarding wavelength control unit 144 of the multicast forwarding unit 14 sets the wavelength tunable filters 145-1 to 145-nP to transmit an optical signal of wavelength λ1 (step S201). The subscriber device 16-1 transmits an optical signal of wavelength λ1 (step S202). The optical signal of wavelength λ1 transmitted from the subscriber device 16-1 is input to one 1×M optical switch 31 provided in the optical distribution unit 30-1 via an optical transmission path.

[0099] The 1×M optical switch 31 is controlled by the optical SW control unit 122 so that a path between the first port of the 1×M optical switch 31 to which subscriber device 16-1 is connected and the second port of the 1×M optical switch 31 to which the multicast forwarding unit 14 is connected is connected. As a result, the optical signal of wavelength λ1 input to the first port of the 1×M optical switch 31 is output from the second port to which the multicast forwarding unit 14 is connected. The optical signal output from the 1×M optical switch 31 is input to the multicast forwarding unit 14 (step S203).

[0100] The optical signal with wavelength λ1 output from the 1×M optical switch 31 is input to the coupler 141 included in the multicast forwarding unit 14 (step S204). The coupler 141 multiplexes the input optical signals and outputs the multiplexed signal (step S205). The optical signal output from the coupler 141 is amplified by the amplifier 142 (step S206). The optical signal amplified by the amplifier 142 is input to the coupler 143.

[0101] The coupler 143 branches the input optical signal to each connected optical transmission path (step S207). The optical signals branched to each optical transmission path are input to the tunable wavelength filters 145-1 to 145-nP. Here, since the wavelength λ1 is set as the set wavelength, optical signals of wavelength λ1 are output from the tunable wavelength filters 145-1 to 145-nP. The optical signals of wavelength λ1 output from the tunable wavelength filters 145-1 to 145-nP are input via the optical transmission paths to second ports of the plurality of 1×M optical switches 42 included in the optical distribution unit 40-1 and second ports of the plurality of 1×M optical switches 42 included in the optical distribution unit 40-P.

[0102] Of the multiple 1×M optical switches 42 included in the optical distribution unit 40-1, the optical SW control unit 122 controls so that a path between the first port of the 1×M optical switch 42 to which the subscriber device 16-2 is connected and the second port of the 1×M optical switch 42 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 1×M optical switch 42 is output from the first port to the subscriber device 16-2 via the optical transmission line (step S209). The subscriber device 16-2 receives the optical signal of wavelength λ1 output from the 1×M optical switch 42 (step S210).

[0103] Of the multiple 1×M optical switches 42 included in the optical distribution unit 40-P, the optical SW control unit 122 controls so that a path between the first port of the 1×M optical switch 42 to which the subscriber device 16-3 is connected and the second port of the 1×M optical switch 42 to which the multicast forwarding unit 14 is connected is connected. As a result, an optical signal of wavelength λ1 input to the second port of the 1×M optical switch 42 is output from the first port to the subscriber device 16-3 via the optical transmission line. The subscriber device 16-3 receives the optical signal of wavelength λ1 output from the 1×M optical switch 42.

[0104] According to the optical communication system 1 of the fourth embodiment configured as described above, even in a configuration in which a multicast switch is used instead of an optical SW as an optical distribution unit, it is possible to reduce the number of wirings required for return in each of the optical distribution units 30 and 40. Therefore, it becomes possible to connect each subscriber device to any other subscriber device at any timing using a smaller number of return transmission paths than conventionally.

[0105] (Modification 1 of the fourth embodiment) The light distribution unit 30 and the light distribution unit 40 may have the configuration shown in Fig. 10. Fig. 10 is a configuration diagram of an optical communication system 1 in a modified example of the fourth embodiment. The system configuration of the optical communication system 1 in the modified example of the fourth embodiment is the same as that of the fourth embodiment. In Fig. 10, what differs from Fig. 8 is the connection between the light distribution unit 30 and the multicast forwarding unit 14, and the connection between the light distribution unit 40 and the multicast forwarding unit 14.

[0106] In the configuration shown in FIG. 8 , one of the second ports of each 1×M optical switch 31 is connected to the multicast forwarding unit 14, and one of the second ports of each 1×M optical switch 42 is connected to the multicast forwarding unit 14. In contrast, in the configuration shown in FIG. 10 , one of the multiple signal multiplexing units 32 is connected to the multicast forwarding unit 14, and one of the multiple signal demultiplexing units 41 is connected to the multicast forwarding unit 14. With this configuration, it is sufficient to connect one optical distribution unit 30, 40 to the multicast forwarding unit 14 via one optical transmission line. Therefore, it is not necessary to connect one optical distribution unit 30, 40 to the multicast forwarding unit 14 via optical transmission lines equal to the number of 1×M optical switches 31, as in the fourth embodiment. This eliminates the need for optical transmission lines connected to the multicast forwarding unit 14.

[0107] 10 , when multicast communication spanning the optical distribution units 30 is performed, the optical SW control unit 122 switches the paths between the ports of each 1×M optical switch 31 so that the optical signals input to each 1×M optical switch 31 are input to the multicast forwarding unit 14. Specifically, the optical SW control unit 122 switches the paths between the ports of the 1×M optical switch 31 so that the second port of the 1×M optical switch 31 connected to the signal multiplexing unit 32 connected to the multicast forwarding unit 14 is connected to the first port of the 1×M optical switch 31. The 1×M optical switch 31 outputs the optical signal transmitted from the edge node 15 or the subscriber device 16 connected to the first port from the second port connected to the signal multiplexing unit 32 connected to the multicast forwarding unit 14. The signal multiplexing unit 32 multiplexes the optical signals output from each 1×M optical switch 31 and outputs the multiplexed signals to the multicast forwarding unit 14. As a result, the optical signal input to the first port of the 1×M optical switch 31 is input to the multicast forwarding unit 14 via the signal multiplexing unit 32 .

[0108] Similarly, the optical SW control unit 122 switches the path between the ports of the 1×M optical switch 42 so as to connect the second port of the 1×M optical switch 42 connected to the signal separation unit 41 connected to the multicast forwarding unit 14 with the first port of the 1×M optical switch 42. The signal separation unit 41 branches or demultiplexes the optical signal forwarded from the multicast forwarding unit 14 and outputs it to each 1×M optical switch 42. The 1×M optical switch 42 receives the optical signal output from the signal separation unit 41 connected to its second port and outputs the input optical signal from its first port. As a result, the optical signal multicast from the multicast forwarding unit 14 is input to the second port of the 1×M optical switch 42 via the signal separation unit 41. The optical signal input to the second port of the 1×M optical switch 42 is output from the first port and input to the desired subscriber device 16.

[0109] (Modification 2 of the fourth embodiment) In the above embodiment, a configuration has been shown in which the optical distribution unit 30, the optical distribution unit 40, and the multicast forwarding unit 14 are provided in one optical communication device. However, any one of the optical distribution unit 30, the optical distribution unit 40, and the multicast forwarding unit 14 may be implemented in another device. The same applies when the multicast forwarding unit 14 is the multicast forwarding unit 14a or 14b.

[0110] (Fifth embodiment) In the fifth embodiment, an upstream light distribution unit and a downstream light distribution unit that are different from the first to fourth embodiments will be described. In the fifth embodiment, the system configuration of the optical communication system 1 is the same as in the first embodiment, but the configuration of the light distribution unit is different. Therefore, the differences from the first embodiment will be described below.

[0111] 11 is a configuration diagram of an optical communication system 1 according to the fifth embodiment. The optical communication system 1 according to the fifth embodiment includes P optical distribution units 30a-1 to 30a-P, P optical distribution units 40a-1 to 40a-P, a control unit 12 (not shown), and a multicast forwarding unit 14. In the following description, it is assumed that the optical distribution units 30a-1 to 30a-P are used for transmitting optical signals in the upstream direction, and the optical distribution units 40a-1 to 40a-P are used for transmitting optical signals in the downstream direction.

[0112] The light distribution units 30a-1 to 30a-P have the same configuration. The light distribution units 40a-1 to 40a-P have the same configuration. In the following description, when there is no need to distinguish between the light distribution units 30a-1 to 30a-P, they will simply be referred to as light distribution unit 30a, and when there is no need to distinguish between the light distribution units 40a-1 to 40a-P, they will simply be referred to as light distribution unit 40a. The light distribution units 30a, 40a, control unit 12, and multicast forwarding unit 14 are functional units that make up a single optical communication device.

[0113] The optical distribution unit 30a is configured to include one or more N×M wavelength selective switches 33. The optical distribution unit 30a is one aspect of a first optical distribution unit. The N×M wavelength selective switch 33 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 N×M wavelength selective switch 33 has N (N is an integer equal to or greater than 1) first ports and M second ports. The N first ports of the N×M wavelength selective switch 33 are connected to the edge node 15 or the subscriber device 16 via the optical transmission paths. The N×M wavelength selective switch 33 is a WSS.

[0114] One second port out of the M second ports of the N×M wavelength selective switch 33 is connected to the multicast forwarding unit 14 via an optical transmission path. The remaining second ports (for example, (M−1) second ports) of the M second ports of the N×M wavelength selective switch 33 are each connected to another device via an optical transmission path.

[0115] The optical distribution unit 40a includes one or more N×M wavelength selective switches 43. The optical distribution unit 40a is one aspect of a second optical distribution unit. The N×M wavelength selective switch 43 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 N×M wavelength selective switch 43 has N first ports and M second ports. The N first ports of the N×M wavelength selective switch 43 are connected to the subscriber device 16 via the optical transmission paths.

[0116] One second port of the M second ports of the N×M wavelength selective switch 43 is connected to the multicast forwarding unit 14 via an optical transmission path. The remaining second ports of the M second ports of the N×M wavelength selective switch 43 (for example, (M−1) second ports) are each connected to another device via an optical transmission path. The N×M wavelength selective switch 43 is a WSS.

[0117] To compensate for signal loss, an amplifier may be installed on either or all of the optical transmission lines connected to the first ports of the N×M wavelength selective switches 33 and 43 or the optical transmission lines connected to the second ports of the N×M wavelength selective switches 33 and 43.

[0118] The multicast forwarding unit 14 receives as input the optical signals output from each N×M wavelength selective switch 33, and forwards the input optical signals by multicast to at least each N×M wavelength selective switch 43 to which the destination subscriber device 16 is connected. One optical transmission path is connected from one N×M wavelength selective switch 33 to the multicast forwarding unit 14. Therefore, one optical transmission path is connected from one optical distribution unit 30a to the multicast forwarding unit 14, and since there are P optical distribution units 30a, P upstream optical transmission paths are connected to the multicast forwarding unit 14. Furthermore, one optical transmission path is connected from one optical distribution unit 40a to the multicast forwarding unit 14, and since there are P optical distribution units 40a, P downstream optical transmission paths are connected to the multicast forwarding unit 14.

[0119] When multicast communication spanning the optical distribution unit 30a is performed, the optical SW control unit 122 switches the paths between the ports of each N×M wavelength selective switch 33 so that the output destination of the optical signal from each N×M wavelength selective switch 33 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 N×M wavelength selective switch 43. With this configuration, return communication between any N×M wavelength selective switches is realized while limiting the number of wirings required for return at each N×M wavelength selective switch to P.

[0120] The configuration of the multicast forwarding unit 14 may be any of the configurations shown in the first to third embodiments. That is, the configuration of the multicast forwarding unit 14 may be any of the configurations shown in Fig. 2, and Figs. 4 to 7.

[0121] In the fifth embodiment, the optical SW control unit 122 switches the connection between ports of the N×M wavelength selective switches 33 and the connection between ports of the N×M wavelength selective switches 43. Specifically, in the fourth embodiment, the optical SW control unit 122 switches the connection between ports for each N×M wavelength selective switch 33 included in each light distribution unit 30a, and the connection between ports for each N×M wavelength selective switch 43 included in each light distribution unit 40a.

[0122] For example, the optical SW control unit 122 switches the connection between ports so as to connect a first port of the N×M wavelength selective switch 33 to which the edge node 15 or subscriber device 16 to which data is to be transmitted is connected, with a second port to which the multicast forwarding unit 14 is connected. The N×M wavelength selective switch 33 outputs an optical signal transmitted from the edge node 15 or subscriber device 16 connected to the first port from the second port to which the multicast forwarding unit 14 is connected. As a result, the optical signal input to the first port of the N×M wavelength selective switch 33 is directly input to the multicast forwarding unit 14.

[0123] Similarly, the connection between ports is switched so that the first port of the N×M wavelength selective switch 43, to which the destination subscriber device 16 is connected, is connected to the second port to which the multicast forwarding unit 14 is connected. The optical signal forwarded from the multicast forwarding unit 14 is input to the second port of the N×M wavelength selective switch 43. The N×M wavelength selective switch 43 outputs the optical signal forwarded from the multicast forwarding unit 14 and input to the second port from the first port to which the destination subscriber device 16 is connected. In this way, the optical signal output from the multicast forwarding unit 14 is forwarded to the desired subscriber device 16.

[0124] According to the optical communication system 1 of the fifth embodiment configured as described above, even in a configuration in which the N×M wavelength selective switches 33, 43 are used as the optical distribution units instead of the optical SW, the number of wirings required for return in each of the optical distribution units 30 a, 40 a can be reduced. Therefore, it becomes possible to connect each subscriber device to any subscriber device at any timing using a smaller number of return transmission lines than conventionally.

[0125] (Modification 1 of the fifth embodiment) As shown in the fifth embodiment, when the light distribution unit 30a is configured with an N×M wavelength selective switch 33 and the light distribution unit 40a is configured with an N×M wavelength selective switch 43, the multicast forwarding unit 14 may have the configuration shown in any of Figures 12 to 14. The configuration of the multicast forwarding unit 14 shown in Figures 12 to 14 is configured with components that are not wavelength-dependent for the ports.

[0126] When the optical distribution unit 30a is configured with an N×M wavelength selective switch 33, a plurality of optical signals can be multiplexed in the optical distribution unit 30a and then input to the multicast forwarding unit 14. Therefore, it is sufficient that each N×M wavelength selective switch 33 is connected to the multicast forwarding unit 14 by one optical transmission line, and when there are P N×M wavelength selective switches 33, P optical transmission lines are connected to the multicast forwarding unit 14.

[0127] 12 is a block diagram showing a specific example of a functional configuration (part 1) of the multicast forwarding unit 14c in a modified example of the fifth embodiment. The multicast forwarding unit 14c includes a coupler 141, an amplifier 142, and a coupler 143. The coupler 141 is connected to P optical transmission paths connected to each optical distribution unit 30a, and receives an optical signal transmitted through any of the P optical transmission paths. The coupler 141 multiplexes the input optical signals and outputs the multiplexed signals. The number of ports required for the coupler 141 is P.

[0128] The amplifier 142 amplifies the optical signal output from the coupler 141 .

[0129] The coupler 143 branches and outputs the optical signal amplified by the amplifier 142. The number of ports required for the coupler 143 is P. The optical signals branched and output by the coupler 143 are input to the N×M wavelength selective switches 43 of each optical distribution unit 40a via P optical transmission paths. Even if the optical signal input from the multicast forwarding unit 14 to each N×M wavelength selective switch 43 is a wavelength multiplexed signal, it can be separated by each N×M wavelength selective switch 43.

[0130] With this configuration, even if the multicast forwarding unit 14 is not provided with a component having wavelength selectivity such as a WSS or AWG, multicast communication between any users is possible.

[0131] 13 is a block diagram showing a specific example of a functional configuration (part 2) of the multicast forwarding unit 14c in a modification of the fifth embodiment. The multicast forwarding unit 14c includes a plurality of couplers 141-1 to 141-X, an amplifier 142, a plurality of couplers 143-1 to 143-X, a plurality of upper-level 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.

[0132] In the example shown in FIG. 13, 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.

[0133] The coupler 141-x is connected to P / X different optical transmission paths out of the P optical transmission paths connected to each optical distribution unit 30a, and receives as input an optical signal transmitted through any of the P / X optical transmission paths. The coupler 141-x multiplexes the input optical signals and outputs the multiplexed optical signals. In this way, on average, approximately the same number of optical transmission paths are connected to each coupler 141. For example, if there are two couplers 141 (X=2) and four optical distribution units 30a (P=4), two different optical transmission paths are connected to each coupler 141.

[0134] The amplifier 147-x amplifies the optical signal output from the coupler 141-x. The upstream coupler 146-1 multiplexes and outputs the optical signals amplified by the amplifiers 147. The upstream coupler 146-2 branches the optical signal output from the upstream coupler 146-1 and amplified by the amplifier 142.

[0135] The amplifier 148-x amplifies the optical signal output from the upstream coupler 146-2. The coupler 143-x branches and outputs the optical signal amplified by the amplifier 148-x. The number of ports required for the coupler 143-x is P / X. The optical signals branched and output by the coupler 143-x are input to the N×M wavelength selective switches 43 of each optical distribution unit 40a via P / X optical transmission paths. Even if the optical signals input from the multicast forwarding unit 14 to each N×M wavelength selective switch 43 are wavelength multiplexed signals, they can be separated by each N×M wavelength selective switch 43.

[0136] With this configuration, even if the multicast forwarding unit 14 is not provided with a component having wavelength selectivity such as a WSS or AWG, multicast communication between any users is possible.

[0137] 14 is a block diagram showing a specific example of a functional configuration (part 3) of the multicast forwarding unit 14c in a modification of the fifth embodiment. The multicast forwarding unit 14c 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 plurality of upper level couplers 146-1-1 to 146-1-X, a plurality of upper level 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.

[0138] In the example shown in FIG. 14, 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.

[0139] The coupler 141-x is connected to different P / X optical transmission lines among the P optical transmission lines connected to each optical distribution unit 30a, and receives an optical signal transmitted through any of the P / X optical transmission lines as input. The coupler 141-x multiplexes the input optical signals and outputs the multiplexed signal.

[0140] The amplifier 147-x amplifies the optical signal output from the coupler 141-x. The upstream coupler 146-1-x branches and outputs the optical signal amplified by the amplifier 147-x. 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.

[0141] The amplifier 148-x amplifies the optical signal output from the upstream coupler 146-2-x. The coupler 143-x branches and outputs the optical signal amplified by the amplifier 148-x. The number of ports required for the coupler 143-x is P / X. The optical signals branched and output by the coupler 143-x are input to the N×M wavelength selective switches 43 of each optical distribution unit 40a via P / X optical transmission paths. Even if the optical signals input from the multicast forwarding unit 14 to each N×M wavelength selective switch 43 are wavelength multiplexed signals, they can be separated by each N×M wavelength selective switch 43.

[0142] With this configuration, even if the multicast forwarding unit 14 is not provided with a component having wavelength selectivity such as a WSS or AWG, multicast communication between any users is possible.

[0143] (Modification 2 of the fifth embodiment) In the above embodiment, a configuration has been shown in which the optical distribution unit 30a, the optical distribution unit 40a, and the multicast forwarding unit 14 are provided in one optical communication device. However, any one of the optical distribution unit 30a, the optical distribution unit 40a, and the multicast forwarding unit 14 may be implemented in another device. The same applies when the multicast forwarding unit 14 is the multicast forwarding unit 14a or 14b.

[0144] (Sixth embodiment) In the sixth embodiment, an upstream light distribution unit and a downstream light distribution unit that are different from the first to fifth embodiments will be described. In the sixth embodiment, the system configuration of the optical communication system 1 is the same as in the first embodiment, but the configuration of the light distribution unit is different. Therefore, the differences from the first embodiment will be described below.

[0145] 15 is a configuration diagram of an optical communication system 1 in the sixth embodiment. The optical communication system 1 in the sixth embodiment includes P optical distribution units 30b-1 to 30b-P, P optical distribution units 40b-1 to 40b-P, a control unit 12 (not shown), and a multicast forwarding unit 14. In the following explanation, it is assumed that the optical distribution units 30b-1 to 30b-P are used for transmitting optical signals in the upstream direction, and the optical distribution units 40b-1 to 40b-P are used for transmitting optical signals in the downstream direction.

[0146] The light distribution units 30b-1 to 30b-P have the same configuration. The light distribution units 40b-1 to 40b-P have the same configuration. In the following description, when there is no need to distinguish between the light distribution units 30b-1 to 30b-P, they will simply be referred to as light distribution unit 30b, and when there is no need to distinguish between the light distribution units 40b-1 to 40b-P, they will simply be referred to as light distribution unit 40b. The light distribution units 30b, 40b, control unit 12, and multicast forwarding unit 14 are functional units that make up a single optical communication device.

[0147] The optical distribution unit 30b includes one or more 1×N wavelength selective switches 34 and one or more 1×M wavelength selective switches 35. The optical distribution unit 30b is one aspect of a first optical distribution unit. The 1×N wavelength selective switches 34 and the 1×M wavelength selective switches 35 are connected to multiple optical transmission paths and output an optical signal input from one of the optical transmission paths to another optical transmission path. The 1×N wavelength selective switch 34 has N first ports and one second port. The N first ports of the 1×N wavelength selective switch 34 are connected to the edge node 15 or the subscriber device 16 via the optical transmission paths. The one second port of the 1×N wavelength selective switch 34 is connected to the 1×M wavelength selective switch 35 via the optical transmission path. The 1×N wavelength selective switch 34 is a WSS.

[0148] The 1×M wavelength selective switch 35 has one first port and M second ports. The one first port of the 1×M wavelength selective switch 35 is connected to the 1×N wavelength selective switch 34 via an optical transmission path. One second port of the M second ports of the 1×M wavelength selective switch 35 is connected to the multicast forwarding unit 14 via an optical transmission path. The remaining second ports of the M second ports of the 1×M wavelength selective switch 35 (for example, (M−1) second ports) are each connected to other devices via optical transmission paths. The 1×M wavelength selective switch 35 is a WSS.

[0149] The optical distribution unit 40b is configured to include one or more 1×M wavelength selective switches 44 and one or more 1×N wavelength selective switches 45. The optical distribution unit 40b is one aspect of a second optical distribution unit. The 1×M wavelength selective switches 44 and the 1×N wavelength selective switches 45 are connected to multiple optical transmission paths and output an optical signal input from one of the optical transmission paths to another optical transmission path. The 1×M wavelength selective switch 44 has one first port and M second ports. The one first port of the 1×M wavelength selective switch 44 is connected to the 1×N wavelength selective switch 45 via an optical transmission path.

[0150] One of the M second ports of the 1×M wavelength selective switch 44 is connected to the multicast forwarding unit 14 via an optical transmission path. The remaining second ports of the M second ports of the 1×M wavelength selective switch 44 (for example, (M−1) second ports) are each connected to another device via an optical transmission path. The 1×M wavelength selective switch 44 is a WSS.

[0151] The 1×N wavelength selective switch 45 has N first ports and one second port. The N first ports of the 1×N wavelength selective switch 45 are connected to the subscriber device 16 via optical transmission lines. The one second port of the 1×N wavelength selective switch 45 is connected to the 1×M wavelength selective switch 44 via an optical transmission line. The 1×N wavelength selective switch 45 is a WSS.

[0152] Amplifiers may be installed to compensate for signal loss, and may be installed in any or all of the following locations: on the transmission line of the first port of each of the 1×N wavelength selective switches 34 and 45; on the transmission line between the 1×N wavelength selective switch 34 and the 1×M wavelength selective switch 35; on the transmission line between the 1×M wavelength selective switch 44 and the 1×N wavelength selective switch 45; and on the transmission line of the second port of each of the 1×M wavelength selective switches 35 and 44.

[0153] The multicast forwarding unit 14 receives as input the optical signals output from each 1×M wavelength selective switch 35, and forwards the input optical signals by multicast to at least each 1×M wavelength selective switch 44 to which the destination subscriber device 16 is connected. One optical transmission path is connected from one 1×M wavelength selective switch 35 to the multicast forwarding unit 14. Therefore, one optical transmission path is connected from one optical distribution unit 30b to the multicast forwarding unit 14, and since there are P optical distribution units 30b, P upstream optical transmission paths are connected to the multicast forwarding unit 14. Furthermore, one optical transmission path is connected from one optical distribution unit 40b to the multicast forwarding unit 14, and since there are P optical distribution units 40b, P downstream optical transmission paths are connected to the multicast forwarding unit 14.

[0154] When multicast communication spanning the optical distribution units 30b is performed, the optical SW control unit 122 switches the paths between the ports of the 1×N wavelength selective switch 34 and the 1×M wavelength selective switch 35 provided in the optical distribution unit 30b so that the output destination of the optical signal from the optical distribution unit 30b 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 distribution unit 40b. With this configuration, return communication between any optical distribution units is realized while limiting the number of wirings required for return at each optical distribution unit 40b to P.

[0155] The configuration of the multicast forwarding unit 14 may be any of the configurations shown in the first to third embodiments. That is, the configuration of the multicast forwarding unit 14 may be any of the configurations shown in Fig. 2, and Figs. 4 to 7.

[0156] In the sixth embodiment, the optical SW control unit 122 switches the connection between ports of the 1×N wavelength selective switches 34 and 45 and the connection between ports of the 1×M wavelength selective switches 35 and 44. Specifically, in the sixth embodiment, the optical SW control unit 122 switches the connection between ports for each of the 1×N wavelength selective switches 34 and 35 included in each light distribution unit 30b, and the connection between ports for each of the 1×M wavelength selective switches 44 and 45 included in each light distribution unit 40b.

[0157] For example, the optical SW control unit 122 switches the connections between the ports of the 1×N wavelength selective switch 34 and the 1×M wavelength selective switch 35 so as to connect the first port of the 1×N wavelength selective switch 34, to which the edge node 15 or subscriber device 16 to be transmitted is connected, to the second port, and connect the first port of the 1×M wavelength selective switch 35 to the second port to which the multicast forwarding unit 14 is connected. The 1×N wavelength selective switch 34 outputs the optical signal transmitted from the edge node 15 or subscriber device 16 connected to the first port from the second port. The optical signal output from the 1×N wavelength selective switch 34 is input to the first port of the 1×M wavelength selective switch 35. The 1×M wavelength selective switch 35 outputs the optical signal input to the first port from the second port connected to the multicast forwarding unit 14. As a result, the optical signal input to the optical distribution unit 30b is forwarded to the multicast forwarding unit 14.

[0158] Furthermore, the optical SW control unit 122 switches the connection between the ports of the 1×M wavelength selective switch 44 and the 1×N wavelength selective switch 45 so as to connect the first port of the 1×M wavelength selective switch 44 to the second port of the 1×M wavelength selective switch 44 to which the multicast forwarding unit 14 is connected, and to connect the second port of the 1×N wavelength selective switch 45 to the first port to which the destination subscriber device 16 is connected. The optical signal forwarded from the multicast forwarding unit 14 is input to the second port of the 1×M wavelength selective switch 44. The 1×M wavelength selective switch 44 outputs the optical signal forwarded from the multicast forwarding unit 14 and input to the second port from its first port. The optical signal output from the 1×M wavelength selective switch 44 is input to the second port of the 1×N wavelength selective switch 45. The 1×N wavelength selective switch 45 outputs the optical signal input to the second port from the first port to which the destination subscriber device 16 is connected. As a result, the optical signal output from the multicast forwarding unit 14 is forwarded to the destination subscriber device 16 .

[0159] According to the optical communication system 1 of the sixth embodiment configured as described above, even in a configuration in which a 1×N wavelength selective switch and a 1×M wavelength selective switch are combined as an optical distribution unit instead of an optical SW, the number of wirings required for return in each optical distribution unit 30 b, 40 b can be reduced. Therefore, it becomes possible to connect each subscriber device to any subscriber device at any timing using a smaller number of return transmission lines than conventionally.

[0160] (Modification 1 of the sixth embodiment) As shown in the sixth embodiment, when the optical distribution unit 30b is composed of a 1×N wavelength selective switch 34 and a 1×M wavelength selective switch 35, and the optical distribution unit 40b is composed of a 1×M wavelength selective switch 44 and a 1×N wavelength selective switch 45, the multicast forwarding unit 14 may have the configuration shown in any of Figures 12 to 14.

[0161] (Modification 2 of the sixth embodiment) Either or both of the 1×N wavelength selective switches 34 and 45 and the 1×M wavelength selective switches 35 and 44 may be couplers.

[0162] (Modification 3 of the sixth embodiment) In the above embodiment, a configuration has been shown in which the optical distribution unit 30b, the optical distribution unit 40b, and the multicast forwarding unit 14 are provided in one optical communication device. Any of the optical distribution unit 30b, the optical distribution unit 40b, and the multicast forwarding unit 14 may be implemented in another device. The same applies when the multicast forwarding unit 14 is the multicast forwarding unit 14a or 14b.

[0163] (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.

[0164] 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.

[0165] Some of the functional units (e.g., the control unit 12, the multicast forwarding units 14, 14a, 14b, and 14c) 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 to realize the function. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0166] 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.

[0167] Although an embodiment of the present invention has been described above in detail 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]

[0168] The present invention can be applied to optical communication system technology that performs return communication via an optical distribution unit. [Explanation of symbols]

[0169] 10-1 to 10-P, 11-1 to 11-P...optical switches, 12...control unit, 121...wavelength management and control unit, 122...optical switch control unit, 14, 14a, 14b...multicast forwarding unit, 15...edge node, 16-1 to 16-3...subscriber device, 30, 30-1 to 30-P, 30a, 30a-1 to 30a-P, 30b, 30b-1 to 30b-P, 40, 40-1 to 40-P, 40a, 40a-1 to 40a-P, 40b, 40b-1 to 40b-P...optical distribution unit, 31, 42...1×M optical switch, 32...signal multiplexing unit, 33, 43...N×M wavelength selective switch, 34, 45...1×N wavelength selective switch, 35, 44...1×M wavelength selective switch 41...Signal separation unit, 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...Upstream coupler, 149-1 to 149-P, 149-1 to 149-X...WSS

Claims

1. a plurality of first distribution units connected to the plurality of first optical transmission lines and configured to output an optical signal input from any one of the first devices to any one of the first optical transmission lines; a plurality of second distribution units connected to the plurality of second optical transmission lines and configured to output an optical signal input from any of the second optical transmission lines included in the plurality of second optical transmission lines to any of the second devices; a multicast forwarding unit that multicasts an optical signal transmitted from the first device connected to any one of the plurality of first distribution units to any one of the plurality of second distribution units to which one or more of the second devices are connected; Equipped with the multicast forwarding unit returns the optical signal forwarded from any one of the plurality of first distribution units to one or more second devices connected to any one of the plurality of second distribution units, and forwards the optical signal by multicast, via any one of the plurality of second distribution units; The multicast transfer unit is an optical communication device configured by a combination of a plurality of multiplexing / demultiplexing units that multiplex or demultiplex input optical signals.

2. each of the plurality of first distribution units includes a plurality of first optical switches and a plurality of signal multiplexing units; each of the plurality of second distribution units includes a plurality of second optical switches and a plurality of signal separation units; each of the plurality of first optical switches has one first port to which the first device is connected and a plurality of second ports to which the plurality of signal multiplexing units are connected, at least one second port of the plurality of second ports is connected to the multicast forwarding unit; each of the plurality of second optical switches has one first port to which the second device is connected and a plurality of second ports to which the plurality of signal separation units are connected, and at least one second port of the plurality of second ports is connected to the multicast forwarding unit; 2. The optical communication device according to claim 1.

3. each of the plurality of first distribution units includes a plurality of first optical switches and a plurality of signal multiplexing units; each of the plurality of second distribution units includes a plurality of second optical switches and a plurality of signal separation units; each of the plurality of first optical switches has one first port to which the first device is connected and a plurality of second ports to which the plurality of signal multiplexing units are connected, each of the plurality of second optical switches has one first port to which the second device is connected and a plurality of second ports to which the plurality of signal separation units are connected, at least one signal multiplexing unit among the plurality of signal multiplexing units is connected to the multicast forwarding unit; At least one signal demultiplexing unit among the plurality of signal demultiplexing units is connected to the multicast forwarding unit.

2. The optical communication device according to claim 1.

4. each of the plurality of first distribution units includes one or more first wavelength selective optical switches; each of the plurality of second distribution units includes one or more second wavelength selective optical switches; at least one port of one first wavelength selective type optical switch among the one or more first wavelength selective type optical switches is connected to the multicast forwarding unit; At least one port of one second wavelength selective type optical switch among the one or more second wavelength selective type optical switches is connected to the multicast forwarding unit.

2. The optical communication device according to claim 1.

5. the one or more first wavelength-selective optical switches are N (N is an integer of 1 or more)×M (M is an integer of 2 or more) wavelength-selective optical switches, the one or more second wavelength-selective optical switches are N×M wavelength-selective optical switches; At least one port out of M ports of each N×M wavelength selective optical switch is connected to the multicast forwarding unit.

5. The optical communication device according to claim 4.

6. the one or more first wavelength-selective optical switches are a 1×N (N is an integer equal to or greater than 1) wavelength-selective optical switch and a 1×M (M is an integer equal to or greater than 2) wavelength-selective optical switch, the one or more second wavelength-selective optical switches are a 1×N wavelength-selective optical switch and a 1×M wavelength-selective optical switch; the 1×N wavelength selective optical switch is connected to the 1×M wavelength selective optical switch; At least one port of the M ports of the 1×M wavelength selective optical switch is connected to the multicast forwarding unit.

5. The optical communication device according to claim 4.

7. The plurality of demultiplexing units included in the multicast forwarding unit include: one or more first signal multiplexing units that multiplex and output optical signals output from the one or more first wavelength selective optical switches; one or more second signal demultiplexing units that demultiplex an optical signal output from the one or more first signal multiplexing units or an optical signal based on the optical signal output from the one or more first signal multiplexing units, and output the demultiplexed signal to an optical transmission line to which the one or more second wavelength selective optical switches are connected; It is a combination of 7. The optical communication device according to claim 4.

8. the one or more first signal multiplexing units are a plurality of first signal multiplexing units, the one or more second signal separation units are a plurality of second signal separation units, one or more upper-level first signal multiplexing units that multiplex and output the plurality of optical signals output from the plurality of first signal multiplexing units; one or more upper second signal demultiplexing units that split the optical signal output from the upper first signal multiplexing unit and output the split optical signal to each of the plurality of second signal demultiplexing units; Further provided with 8. The optical communication device according to claim 7.

9. the one or more first signal multiplexing units are a plurality of first signal multiplexing units, the one or more second signal separation units are a plurality of second signal separation units, a plurality of higher-order first signal demultiplexing units that demultiplex and output the optical signals output from the plurality of first signal multiplexing units; a plurality of upper second signal multiplexing units that multiplex the optical signals output from the plurality of upper first signal demultiplexing units and output the multiplexed optical signals to the plurality of second signal demultiplexing units, respectively; Further provided with 8. The optical communication device according to claim 7.

10. a plurality of first distribution units connected to the plurality of first optical transmission lines and configured to output an optical signal input from any one of the first devices to any one of the first optical transmission lines; a plurality of second distribution units connected to the plurality of second optical transmission lines and configured to output an optical signal input from any of the second optical transmission lines included in the plurality of second optical transmission lines to any of the second devices; a multicast forwarding unit that multicasts an optical signal transmitted from the first device connected to any one of the plurality of first distribution units to any one of the plurality of second distribution units to which one or more of the second devices are connected; Equipped with the multicast forwarding unit returns the optical signal forwarded from any one of the plurality of first distribution units to one or more second devices connected to any one of the plurality of second distribution units, and forwards the optical signal by multicast, via any one of the plurality of second distribution units; The multicast transfer unit is an optical communication system configured by a combination of a plurality of multiplexing / demultiplexing units that multiplex or demultiplex input optical signals.

11. a plurality of first distribution units connected to a plurality of first optical transmission paths, and outputting an optical signal input from any one of the first devices to any one of the first optical transmission paths; a plurality of second distribution units are connected to a plurality of second optical transmission lines, and output an optical signal input from any of the second optical transmission lines included in the plurality of second optical transmission lines to any of the second devices; a multicast forwarding unit that multicasts an optical signal transmitted from the first device connected to any one of the plurality of first distribution units to any one of the plurality of second distribution units to which one or more of the second devices are connected; the multicast forwarding unit returns the optical signal forwarded from any one of the plurality of first distribution units to one or more second devices connected to any one of the plurality of second distribution units and forwards the optical signal by multicasting, via any one of the plurality of second distribution units; A transfer method in which the multicast transfer unit is configured by a combination of a plurality of multiplexing / demultiplexing units that multiplex or demultiplex input optical signals.

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