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

Abstract

Provided is an optical communication system including: an optical switch that is connected to multiple optical transmission lines and outputs an optical signal input from one of the optical transmission lines to another one of the optical transmission lines; and a transfer unit that converts single-core transmission to two-core transmission or converts two-core transmission to single-core transmission at a position between a subscriber device and the optical switch, at a position between the subscriber device and the optical switch at a second port that is opposite a first port of the optical switch to which the subscriber device is directly or indirectly connected, or at the second port that is opposite the first port of the optical switch to which the subscriber device is directly or indirectly connected, and thus transfers optical signals such that uplink and downlink interference is prevented.　

Description

[Technical Field]

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

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

[0003] The optical SW 110 is connected to a plurality of optical transmission paths, and outputs an optical signal input from one of the optical transmission paths to the other optical transmission paths. The optical SW 110 shown in Fig. 8 has ports 111-1 to 111-6 and ports 112-1 to 112-6. The optical SW 110 and the WDM filter 140 are connected by a two-core optical transmission path. For example, the port 111-1 of the optical SW 110 and the WDM filter 140 are connected via the optical transmission path 135-1, and the port 111-2 of the optical SW 110 and the WDM filter 140 are connected via the optical transmission path 135-2.

[0004] The optical SW 110 and the control unit 115 are connected by a two-core optical transmission line. For example, the port 112-5 of the optical SW 110 and the control unit 115 are connected via the optical transmission line 136-1, and the port 112-6 of the optical SW 110 and the control unit 115 are connected via the optical transmission line 136-2.

[0005] The control unit 115 includes a subscriber device management and control unit 120 and an optical SW control unit 130. The subscriber device management and control unit 120 allocates wavelengths to the subscriber devices 105. The optical SW control unit 130 switches the path of the optical SW 110.

[0006] Conventionally, in terms of the number of optical transmission paths, in the optical access section between the optical switch 110 and the subscriber device 105 connected to the WDM filter 140, the upstream and downstream are often configured with a single core, with different wavelengths, but in relays, the same wavelength is often used for the upstream and downstream optical transmission paths. The example shown in Figure 8 assumes that an optical signal from the subscriber device 105 with a single core is transmitted using a two-core relay, and is converted to two cores by the WDM filter 140. Because the wavelengths for the upstream and downstream are different, the upstream and downstream can be separated by changing the passing wavelength band of each port of the WDM filter.

[0007] Even when the relay is a single core, an AWG (Arrayed Waveguide Grating) may be used to multiplex optical signals transmitted from multiple subscriber devices. Since the wavelengths that can be accommodated per port of an AWG are fixed, as shown in the configuration of Figure 8, the upstream and downstream signals must be separated once by a WDM filter 140 and then connected to separate ports of the AWG installed between the optical SW 110 and the optical transmission line.

[0008] First, in the sequence in which the subscriber device 105 sends a control signal to the subscriber device management and control unit 120 and the subscriber device management and control unit 120 notifies it of the wavelength to be used, the upstream port can be identified by the presence or absence of optical power according to the control signal, but the downstream port corresponding to that subscriber device 105 cannot be found without prior information. For this reason, it is necessary to decide in advance which downstream port should be used for the upstream port of a certain subscriber device 105. For example, it is necessary to decide in advance by a rule such as placing the upstream and downstream ports next to each other. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2021 / 131202 Summary of the Invention [Problem to be solved by the invention]

[0010] The optical transceiver included in the subscriber device 105 is preferably a wavelength-tunable optical transceiver, which allows communication at any wavelength. However, the passband of the WDM filter 140 limits the available wavelength range. For example, if the available wavelength range in the repeater section is 88 wavelengths in the c-band, wavelengths must be selected from that range for upstream and downstream transmissions. If the passband of the port of the WDM filter 140 connected to port 111-1 of the optical SW 110 is set to wavelengths 1-44 and the passband of the port of the WDM filter 140 connected to port 111-2 of the optical SW 110 is set to wavelengths 45-88, the available wavelength range for upstream and downstream transmissions is reduced by half. As a result, the subscriber device 105 communicates using wavelengths not used by other communications, including those in the repeater section. Therefore, the narrowing of the available wavelength range leads to lost communication opportunities.

[0011] In view of the above circumstances, an object of the present invention is to provide a technique that can alleviate the restrictions on the wavelength ranges that can be used for upstream and downstream transmissions. [Means for solving the problem]

[0012] One aspect of the present invention is an optical communication device comprising: an optical switch connected to a plurality of optical transmission paths and outputting an optical signal input from one of the optical transmission paths to another optical transmission path; and a transfer unit that converts from single-core transmission to two-core transmission, or from two-core transmission to single-core transmission, between a subscriber device and the optical switch, or at a second port opposite to a first port of the optical switch to which the subscriber device is directly or indirectly connected, and transfers the optical signal so as not to cause interference between the upstream and downstream.

[0013] One aspect of the present invention is an optical communication system comprising: an optical switch connected to a plurality of optical transmission paths and outputting an optical signal input from one of the optical transmission paths to another optical transmission path; a transfer unit between a subscriber device and the optical switch that converts the input optical signal from single-core transmission to two-core transmission, or from two-core transmission to single-core transmission, by multiplexing or demultiplexing the input optical signal, and transfers the optical signal so as not to cause interference between the upstream and downstream; an upstream / downstream determination unit that determines which of the multiple ports of the transfer unit are for upstream and downstream based on information on the wavelengths used for upstream and downstream assigned to the subscriber device; and an optical switch control unit that controls the connection between the ports of the optical switch depending on the determination result of the upstream / downstream determination unit.

[0014] One aspect of the present invention is an optical communication method in which an optical switch is connected to multiple optical transmission paths, outputs an optical signal input from one of the optical transmission paths to another optical transmission path, and converts from single-core transmission to two-core transmission, or from two-core transmission to single-core transmission, between a subscriber device and the optical switch, or at a second port of the optical switch opposite to the first port to which the subscriber device is directly or indirectly connected, thereby transferring the optical signal so as not to cause interference between the upstream and downstream.

[0015] One aspect of the present invention is an optical communications method in which an optical switch is connected to multiple optical transmission paths, and outputs an optical signal input from one of the optical transmission paths to another optical transmission path, and a transfer unit converts the input optical signal from one-core transmission to two-core transmission, or from two-core transmission to one-core transmission, by multiplexing or demultiplexing the input optical signal between a subscriber device and the optical switch, and transfers the optical signal so as not to cause interference between the upstream and downstream directions, and determines which of the multiple ports the transfer unit has as an upstream port and which as a downstream port based on information on the wavelengths used for the upstream and downstream directions assigned to the subscriber device, and controls the connection between the ports of the optical switch depending on the determination result. [Effects of the Invention]

[0016] The present invention makes it possible to alleviate restrictions on the wavelength ranges available for upstream and downstream use. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating an example of the configuration of an optical communication system according to a first embodiment. [Figure 2] FIG. 3 is a sequence diagram illustrating a processing flow of the optical communication system according to the first embodiment. [Figure 3] FIG. 10 is a diagram for explaining another problem of the related art. [Figure 4] FIG. 10 is a diagram illustrating an example of the configuration of an optical communication system according to a second embodiment. [Figure 5] FIG. 10 is a sequence diagram illustrating a processing flow of the optical communication system according to the second embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of the configuration of an optical communication system according to a third embodiment. [Figure 7] FIG. 11 is a diagram illustrating an example of a connection relationship between other ports of the optical SW in the third embodiment. [Figure 8] FIG. 1 is a diagram illustrating an example of the configuration of an optical communication system including a conventional optical communication device. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First embodiment) FIG. 1 is a diagram showing an example of the configuration of an optical communication system 1 according to the first embodiment. The optical communication system 1 includes one or more subscriber devices 10, a circulator 20, an optical SW 30, and a control unit 40. The subscriber devices 10 and the circulator 20, the circulator 20 and the optical SW 30, and the optical SW 30 and the control unit 40 are connected using optical transmission paths. The optical transmission paths are, for example, optical fibers. The circulator 20 and the optical SW 30 are examples of functional units that constitute an optical communication device.

[0019] The subscriber device 10 includes an optical transceiver. The optical transceiver is a wavelength-tunable optical transmitter / receiver. Therefore, the subscriber device 10 can communicate using any wavelength. The wavelength used by the subscriber device 10 for communication is assigned by the control unit 40. 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 10 is controlled via a control signal superimposed by the AMCC. The subscriber device 10 is, for example, an ONU (Optical Network Unit) installed in a subscriber's home.

[0020] The circulator 20 has at least three or more ports. In the following description, it is assumed that the circulator 20 has three ports (for example, a first port 21, a second port 22, and a third port 23). The first port 21 of the circulator 20 is connected to the subscriber device 10 via an optical transmission line. The second port 22 of the circulator 20 is connected to the optical SW30 via the optical transmission line 50-1. The third port 23 of the circulator 20 is connected to the optical SW30 via the optical transmission line 50-1. An optical signal input to the first port 21 is output from the second port 22. An optical signal input to the second port 22 is output from the third port 23. An optical signal input to the third port 23 is output from the first port 21.

[0021] In this way, the circulator 20 has directionality and port selectivity but does not have wavelength selectivity. Therefore, the optical signal output by the subscriber device 10 can be output to the optical SW 30 regardless of the wavelength of the optical signal. Furthermore, the circulator 20 can forward the optical signal forwarded from the optical SW 30 to the subscriber device 10 regardless of the wavelength of the optical signal. The circulator 20 is one aspect of a forwarding unit.

[0022] The optical SW30 is an optical switch having M (M is an integer of 2 or more) ports 31 and N (N is an integer of 2 or more) ports 32. In the embodiment, the numbers M and N are described as 6. An optical signal input to a port of the optical SW30 is output from another port. For example, an optical signal input to port 31 of the optical SW30 is output from port 32. The connection relationship between the port 31 and the port 32 of the optical SW30 is set under the control of the control unit 40.

[0023] The second port 22 of the circulator 20 is connected to port 31-1 of the optical SW30 via optical transmission path 50-1, the third port 23 of the circulator 20 is connected to port 31-2 of the optical SW30 via optical transmission path 50-2, the control unit 40 is connected to port 32-5 of the optical SW30 via optical transmission path 60-1, and the control unit 40 is connected to port 32-6 of the optical SW30 via optical transmission path 60-2.

[0024] An optical transmission line for two-core connection to other devices is connected to each of the pair of ports 32-1 and 32-2 and the pair of ports 32-3 and 32-4 of the optical SW 30. The other devices are optical SWs, circulators, etc. installed at locations different from the locations where the optical SW 30 and the control unit 40 are installed.

[0025] The control unit 40 controls at least the subscriber device 10 and the optical SW 30. Here, the control of the subscriber device 10 includes, for example, allocating an emission wavelength to the subscriber device 10, issuing an instruction to stop light, issuing an instruction to change wavelength, etc. The control of the optical SW 30 includes, for example, setting connections between ports of the optical SW 30 and setting optical paths, etc.

[0026] The control unit 40 includes a subscriber device management control unit 41 and an optical SW control unit 42. The subscriber device management control unit 41 assigns wavelengths to the subscriber device 10. When the subscriber device management control unit 41 assigns wavelengths to the subscriber device 10, the optical SW control unit 42 sets up a path between the ports of the optical SW 30 so that the subscriber device 10 and the subscriber device management control unit 41 are connected.

[0027] The subscriber device management control unit 41 stores a management table. The management table includes information for identifying the subscriber device 10, information on the wavelength assigned to the subscriber device 10, and information on the optical SW 30 to which the subscriber device 10 is connected (for example, information on the port to which the subscriber device 10 is connected).

[0028] The optical SW control unit 42 controls the connection between ports of the optical SW 30. Specifically, the optical SW control unit 42 controls the connection between ports of the optical SW 30 so that an optical signal transmitted from the subscriber device 10 is forwarded to the destination subscriber device. For example, if the destination subscriber device is connected to path 2, the optical SW control unit 42 controls the connection between ports so that port 31-1 and port 32-3 are connected. Controlling the connection between ports means setting a path so that a certain port is connected to another port.

[0029] Furthermore, the optical SW control unit 42 controls the connection between ports of the optical SW 30 so that an optical signal addressed to the subscriber device 10 is forwarded to the subscriber device 10. For example, when the subscriber device to be communicated with is connected to path 2, the optical SW control unit 42 controls the connection between ports so as to connect port 31-2 and port 32-4. The control unit 40 is composed of one or more processors. Note that each functional unit of the control unit 40 is realized by implementing the control unit 40 in a single server.

[0030] 2 is a sequence diagram for explaining the flow of processing in the optical communication system 1 in the first embodiment. At the start of the processing in FIG. 2, the connection relationships between the ports of the optical SW 30 are assumed to be set as shown in FIG.

[0031] The subscriber device 10 transmits an optical signal of a wavelength assigned by the control unit 40 using an optical transceiver (step S101). The optical signal transmitted from the subscriber device 10 is input to the first port 21 of the circulator 20 via an optical transmission line. The optical signal input to the first port 21 of the circulator 20 is output from the second port 22 (step S102). The optical signal output from the second port 22 of the circulator 20 is input to the port 31-1 of the optical SW30 via the optical transmission line 50-1 (step S103).

[0032] Port 31-1 of optical SW30 is connected to port 32-3. Therefore, an optical signal input to port 31-1 of optical SW30 is output from port 32-3. In this manner, optical SW30 forwards the input optical signal to another device (step S104). Assume that a response to the optical signal forwarded to another device is input to port 32-4 of optical SW30 (step S105).

[0033] Port 32-4 of optical SW30 is connected to port 31-2. Therefore, an optical signal input to port 32-4 of optical SW30 is output from port 31-2. In this way, optical SW30 transfers the input optical signal to another device (step S106). The optical signal output from port 31-2 of optical SW30 is input to the third port 23 of the circulator 20. The optical signal input to the third port 23 of the circulator 20 is output from the first port 21 (step S107).

[0034] The optical signal output from the first port 21 of the circulator 20 is input to the subscriber device 10 via the optical transmission line 50-2 (step S108), whereby the subscriber device 10 receives the optical signal (step S109).

[0035] The optical communication system 1 configured as described above can reduce the restrictions on the wavelength ranges available for use in the upstream and downstream directions. Specifically, the optical communication system 1 uses a circulator 20 as a single-core to two-core converter between the subscriber device 10 and the optical SW30. By using the circulator 20, interference between the upstream and downstream signals does not occur, and the same wavelength can be used for both the upstream and downstream directions. This makes it possible to reduce the restrictions on the wavelength ranges available for use in the upstream and downstream directions.

[0036] In the past, as shown in FIG. 3, when communication is performed between the subscriber device 105-1 installed at point A and the subscriber device 105-2 installed at point B, the passband of the WDM filter 140-1 connected to the subscriber device 105-1 at point B must be reversed from that of the subscriber device 105-1 installed at point A. That is, the passband of the upstream signal of the subscriber device 105-1 must be set to the passband of the downstream signal of the WDM filter 140-2 connected to the subscriber device 105-2, and the passband of the downstream signal of the subscriber device 105-1 must be set to the passband of the upstream signal of the WDM filter 140-2. As a result, the upstream wiring and downstream wiring for converting between one core and two cores must be different for each base station, which leads to complication of on-site wiring work. In contrast, in the optical communication system 1 according to the first embodiment, a circulator is used instead of a WDM filter, so that the upstream and downstream wiring can be the same at each base station, thereby eliminating the complication of on-site wiring work.

[0037] Furthermore, consider a case where subscriber-to-device 105-1 installed at point A, subscriber-to-device 105-2 installed at point B, and subscriber-to-device 105-3 (not shown) installed at point C communicate with each other. For example, if the passbands of WDM filter 140-2 and WDM filter 140-3 connected to subscriber-to-device 105-3 are inverted with respect to the passband of WDM filter 140-1, communication is possible between subscriber device 105-1 and subscriber device 105-2 and between subscriber device 105-1 and subscriber device 105-3, but communication is not possible between subscriber device 105-2 and subscriber device 105-3. In other words, there is a problem that communication between any two subscriber devices cannot be provided for three or more subscriber devices. In contrast, in the optical communication system 1 of the first embodiment, by using a circulator, the upstream and downstream wiring can be the same at each point, and even in a situation where there are three or more subscriber devices, optical signals can be transferred to the subscriber devices regardless of wavelength, making it possible to realize communication between any two subscriber devices.

[0038] (Second embodiment) In the second embodiment, a configuration in which a circulator is provided on the port 32 side of the optical SW 30 (between the optical SW 30 and another device) will be described. 4 is a diagram showing an example of the configuration of an optical communication system 1a in the second embodiment. The optical communication system 1a includes one or more subscriber devices 10, a circulator 20a, an optical SW 30, and a control unit 40. The subscriber devices 10 and the optical SW 30, the circulator 20a and the optical SW 30, and the optical SW 30 and the control unit 40 are connected using optical transmission paths. The circulator 20a and the optical SW 30 are examples of functional units that constitute an optical communication device.

[0039] The optical communication system 1a differs in configuration from the optical communication system 1 in that the circulator 20a is connected to the port 32 side of the optical SW 30, rather than between the subscriber device 10 and the optical SW 30. The other configurations of the optical communication system 1a are the same as those of the optical communication system 1. Therefore, the differences from the optical communication system 1 will be explained.

[0040] A first port 21 of the circulator 20a is connected to a port 32 (port 32-3 in FIG. 4) of the optical SW 30 via an optical transmission line. A second port 22 and a third port 23 of the circulator 20a are connected to an optical transmission line (path 2 in FIG. 4) that is connected to another device.

[0041] Fig. 5 is a sequence diagram for explaining the flow of processing in the optical communication system 1a in the second embodiment. At the start of the processing in Fig. 5, the connection relationship between the ports of the optical SW 30 is assumed to be set as shown in Fig. 4.

[0042] The subscriber device 10 transmits an optical signal with a wavelength assigned by the control unit 40 using the optical transceiver (step S201). The optical signal transmitted from the subscriber device 10 is input to port 31 of the optical SW 30 via the optical transmission line. In the example shown in FIG. 4, the subscriber device 10 is connected to port 31-2 of the optical SW 30 via the optical transmission line 50. Therefore, the optical signal transmitted from the subscriber device 10 is input to port 31-2 of the optical SW 30 via the optical transmission line 50.

[0043] Port 31-1 of optical SW30 is connected to port 32-3. Therefore, an optical signal input to port 31-1 of optical SW30 is output from port 32-3. Since port 32-3 is connected to first port 21 of circulator 20a, optical SW30 transfers the input optical signal to first port 21 of circulator 20a (step S203). The optical signal input to first port 21 of circulator 20a is output from second port 22 (step S204).

[0044] The optical signal output from the second port 22 of the circulator 20a is transferred to another device via the optical transmission path. Assume that a response to the optical signal transferred to the other device is input to the third port 23 of the circulator 20a (step S205). The optical signal input to the third port 23 of the circulator 20a is output from the first port 21 (step S206).

[0045] The optical signal output from the first port 21 of the circulator 20 is input to port 32-3 of the optical SW 30 via the optical transmission line. The optical signal input to port 32-3 of the optical SW 30 is output from port 31-2. The optical signal output from port 31-2 of the optical SW 30 is input to the subscriber device 10 via the optical transmission line 50. In this way, the optical SW 30 forwards the input optical signal to the subscriber device 10. As a result, the subscriber device 10 receives the optical signal (step S208).

[0046] According to the optical communication system 1a configured as described above, the number of ports required for the optical SW 30 when transferring optical signals can be reduced compared to the first embodiment. Specifically, in the optical communication system 1 in the first embodiment, the circulator 20 and the optical SW 30 are connected by a two-core optical transmission line, and the port 32 side of the optical SW 30 is also connected by a two-core optical transmission line. In contrast, in the optical communication system 1a in the second embodiment, the subscriber device 10 and the optical SW 30 are connected by a single-core optical transmission line, and the port 32 of the optical SW 30 and the circulator 20a are connected by a single-core optical transmission line. This makes it possible to reduce the number of ports required for the optical SW 30 when transferring optical signals.

[0047] (Third embodiment) In the third embodiment, a WDM filter is provided between the subscriber device 10 and the optical SW 30, and whether each port of the WDM filter is used as an upstream port or a downstream port is changed depending on the wavelength range. In the following description, the direction from the subscriber device 10 toward the optical SW 30 is defined as the upstream direction, and the direction from the optical SW 30 toward the subscriber device 10 is defined as the downstream direction.

[0048] 6 is a diagram showing an example of the configuration of an optical communication system 1b according to the third embodiment. The optical communication system 1b includes one or more subscriber devices 10, a WDM filter 25, an optical SW 30, and a control unit 40b. The subscriber devices 10 and the WDM filter 25, the WDM filter 25 and the optical SW 30, and the optical SW 30 and the control unit 40b are connected via optical transmission paths. The WDM filter 25 and the optical SW 30 are examples of functional units constituting an optical communication device.

[0049] The optical communication system 1b differs in configuration from the optical communication system 1 in that it includes a WDM filter 25 instead of the circulator 20 and a control unit 40b instead of the control unit 40. The other configurations of the optical communication system 1b are the same as those of the optical communication system 1. Therefore, the differences from the optical communication system 1 will be explained.

[0050] The control unit 40b includes a subscriber device management control unit 41b, an optical SW control unit 42b, and an upstream / downstream determination unit 43. The subscriber device management control unit 41b assigns wavelengths to the subscriber device 10. Furthermore, the subscriber device management control unit 41b holds information on the passband of each port (e.g., the second port 27 and the third port 28) of the WDM filter 25. After assigning an upstream wavelength and a downstream wavelength to the subscriber device 10, the subscriber device management control unit 41b notifies the upstream / downstream determination unit 43 of information on the assigned wavelengths (hereinafter referred to as "wavelength information").

[0051] Based on the wavelength information notified from the subscriber device management control unit 41b, the upstream / downstream determining unit 43 determines which of the multiple ports of the WDM filter 25 are upstream ports and which are downstream ports. Note that the upstream / downstream determining unit 43 is assumed to previously store information on the ports 31 of the optical SW 30 to which each port of the WDM filter 25 is connected.

[0052] 6, the upstream / downstream determining unit 43 holds information indicating that the second port 27 of the WDM filter 25 is connected to port 31-1 of the optical SW 30, and that the third port 28 of the WDM filter 25 is connected to port 31-2 of the optical SW 30. Information on the ports 31 of the optical SW 30 to which the ports of the WDM filter 25 are connected may be set in advance in the control unit 40b by an administrator.

[0053] The optical SW control unit 42b controls the connection between ports of the optical SW 30 according to the determination result of the upstream / downstream determination unit 43. Specifically, the optical SW control unit 42b controls the connection between ports of the optical SW 30 so that the port 31 of the optical SW 30, to which the port of the WDM filter 25 (e.g., the second port 27 or the third port 28) having the upstream wavelength in its passband is connected, is connected to the port 32 for the upstream direction. More specifically, the optical SW control unit 42b controls the connection between ports of the optical SW 30 so that the port 31 of the optical SW 30, to which the port of the WDM filter 25 (e.g., the second port 27 or the third port 28) having the downstream wavelength in its passband is connected, is connected to the port 32 for the downstream direction.

[0054] An example of specific processing in the optical communication system 1b will be described. Assume that the wavelength range available in the repeater section is 88 wavelengths in the c-band, and that the upstream and downstream wavelengths are selected from the 88 wavelengths in the c-band. The passband of the WDM filter 25 is wavelengths 1 to 44 for the second port 27 and wavelengths 45 to 88 for the third port. If the subscriber device management and control unit 41b assigns wavelength 10 as the upstream wavelength and wavelength 50 as the downstream wavelength to the subscriber device 10, the upstream / downstream determination unit 43 determines that the second port 27 of the WDM filter 25 is the upstream port and the third port 28 of the WDM filter 25 is the downstream port. The upstream / downstream determination unit 43 notifies the optical SW control unit 42b of this determination result.

[0055] The optical SW control unit 42b controls the connection between the ports of the optical SW 30 in accordance with the determination result notified by the upstream / downstream determination unit 43 so that the port 31-1 of the optical SW 30, to which the second port 27 of the WDM filter 25 is connected, is connected to the upstream port 32-3. Furthermore, in accordance with the determination result notified by the upstream / downstream determination unit 43, the optical SW control unit 42b controls the connection between the ports of the optical SW 30 in accordance with the determination result notified by the upstream / downstream determination unit 43 so that the port 31-2 of the optical SW 30, to which the third port 28 of the WDM filter 25 is connected, is connected to the downstream port 32-4.

[0056] The WDM filter 25 is an optical coupler (optical multiplexer / demultiplexer) that multiplexes or demultiplexes input optical signals. The WDM filter 25 has three ports (for example, a first port 26, a second port 27, and a third port 28). The first port 26 of the WDM filter 25 is connected to the subscriber device 10 via an optical transmission line. The second port 27 of the WDM filter 25 is connected to the optical SW30 via an optical transmission line 50-1. The third port 28 of the WDM filter 25 is connected to the optical SW30 via the optical transmission line 50-1.

[0057] An optical signal input to the first port 26 is output from the second port 27 or the third port 28 depending on the wavelength. It is assumed that the wavelength passbands of the second port 27 and the third port 28 of the WDM filter 25 are set in advance. The optical signals input from the second port 27 or the third port 28 are multiplexed and output from the first port 26.

[0058] When connecting the second port 27 and the third port 28 of the WDM filter 25 to any port of the optical SW 30, the port information must be separately set in the upstream / downstream determining unit 43. Alternatively, an operation rule may be set to connect the second port 27 and the third port 28 of the WDM filter 25 to, for example, port 31-(x+1) and port 31-(x+2) (x is an integer equal to or greater than 0) of the optical SW 30. In this case, the upstream / downstream determining unit 43 determines whether port 31-(x+1) or port 31-(x+2) is to be used as the upstream or downstream port, and there is no need to separately set the port information. The WDM filter 25 is one aspect of a forwarding unit.

[0059] Next, another example of specific processing in the optical communication system 1b will be described. When the subscriber device management and control unit 41b assigns wavelength 60 as the upstream wavelength and wavelength 20 as the downstream wavelength to the subscriber device 10, the upstream / downstream determination unit 43 determines that the second port 27 of the WDM filter 25 is the downstream port and the third port 28 of the WDM filter 25 is the upstream port. The upstream / downstream determination unit 43 notifies the optical SW control unit 42b of this determination result.

[0060] The optical SW control unit 42b controls the connection relationship between the ports of the optical SW 30 as shown in Fig. 7, in accordance with the determination result notified from the upstream / downstream determination unit 43. Fig. 7 is a diagram showing an example of the connection relationship between other ports of the optical SW 30 in the third embodiment. The optical SW control unit 42b controls the connection between the ports of the optical SW 30 so that the port 31-1 of the optical SW 30, to which the second port 27 of the WDM filter 25 is connected, is connected to the downstream port 32-4. Furthermore, in accordance with the determination result notified from the upstream / downstream determination unit 43, the optical SW control unit 42b controls the connection between the ports of the optical SW 30 so that the port 31-2 of the optical SW 30, to which the third port 28 of the WDM filter 25 is connected, is connected to the upstream port 32-3.

[0061] In the past, wavelengths for either the upstream or downstream transmissions were selected from one passband, but in the optical communication system 1b configured as described above, wavelengths for either the upstream or downstream transmissions can be selected from both passbands, thereby expanding the range of available wavelengths. Furthermore, the upstream and downstream wiring of the WDM filter 25 can be made the same at each base station, and the upstream and downstream can be changed remotely using the optical SW 30, eliminating the complexity of on-site wiring work. Furthermore, even in a situation where there are three or more subscriber devices, optical signals can be transferred to the subscriber devices regardless of wavelength, making it possible to realize communication between any of the subscriber devices.

[0062] In the conventional configuration shown in Fig. 3, if the repeater has one core and multiple wavelengths are multiplexed / demultiplexed using an AWG, there is no need to distinguish between upstream and downstream. In the third embodiment, if the repeater has two cores and the upstream and downstream signals are transmitted over different optical transmission paths, it is necessary to distinguish and control the upstream and downstream signals.

[0063] (Modifications common to the first and second embodiments) In the first and second embodiments, the explanation is based on the assumption that the repeater section has two cores, but the present invention can also be applied to the case where the repeater section has one core. Even when the repeater has one core, when multiplexing signals from multiple subscriber devices using an AWG, as mentioned above, it is necessary to separate the upstream and downstream signals once, and the configurations shown in the first and second embodiments can be used for this separation.

[0064] Some of the functional units of the control units 40 and 40b in the above-described embodiment may be implemented by a computer. In this case, a program for implementing the functions may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0065] 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.

[0066] 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]

[0067] The present invention is applicable to optical communication systems. [Explanation of symbols]

[0068] 10... subscriber device, 20, 20a... circulator, 25... WDM filter, 30... optical switch, 40, 40b... control unit, 41, 41b... subscriber device management control unit, 42, 42b... optical switch control unit, 43... upstream / downstream determination unit

Claims

1. an optical switch connected to a plurality of optical transmission lines and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a transfer unit that converts from single-core transmission to dual-core transmission, or from dual-core transmission to single-core transmission, and transfers optical signals so as not to cause interference between upstream and downstream signals; Equipped with a port of the optical switch connected to a subscriber device is designated as a first port, and a port of the optical switch connected to the other path is designated as a second port; the optical switch connects any one of a plurality of first ports to any one of a plurality of second ports, outputs the optical signal input to the first port from the second port, and outputs the optical signal input to the second port from the first port; the transfer unit is connected to the first port of the optical switch; the transfer unit is a circulator, the circulator has a first port, a second port, and a third port; the first port is connected to the subscriber device; the second port is connected to a first port for an upstream direction among a plurality of first ports included in the optical switch; the third port is connected to a first port for a downstream direction among a plurality of first ports included in the optical switch; the circulator outputs an optical signal input to the first port to the first port for upstream direction connected to the second port, and outputs an optical signal input to the third port to the subscriber device connected to the first port; Optical communication equipment.

2. a wavelength multiplexer / demultiplexer that multiplexes or demultiplexes an input optical signal on the second port side of the optical switch; Upstream and downstream optical signals are transmitted over a single fiber.

2. The optical communication device according to claim 1.

3. an optical switch connected to a plurality of optical transmission lines and configured to output an optical signal input from one of the optical transmission lines to another of the optical transmission lines; a transfer unit between the subscriber device and the optical switch that converts input optical signals from single-core transmission to dual-core transmission or from dual-core transmission to single-core transmission by multiplexing or demultiplexing the input optical signals, and transfers the optical signals so that interference between the upstream and downstream is prevented; an upstream / downstream determining unit that determines which of the multiple ports in the forwarding unit is an upstream port and which is a downstream port based on information on the wavelengths used for upstream and downstream assigned to the subscriber device; an optical switch control unit that controls connections between ports of the optical switch in accordance with a determination result of the upstream / downstream determination unit; Equipped with Optical communication system.

4. the optical switch control unit controls the connection between the ports of the optical switch so that the port of the optical switch connected to the port of the forwarding unit whose passband is the upstream wavelength is connected to a port for the upstream direction, and controls the connection between the ports of the optical switch so that the port of the optical switch connected to the port of the forwarding unit whose passband is the downstream wavelength is connected to a port for the downstream direction.

4. The optical communication system according to claim 3.

5. an optical switch connected to a plurality of optical transmission lines, and outputting an optical signal input from one of the optical transmission lines to another optical transmission line; The transfer unit converts from single-core transmission to dual-core transmission, or from dual-core transmission to single-core transmission, and transfers optical signals so that there is no interference between the upstream and downstream signals. a transfer unit that transfers optical signals so as not to cause interference between the upstream and downstream signals is a circulator; a port of the optical switch connected to a subscriber device is designated as a first port, and a port of the optical switch connected to the other path is designated as a second port; the optical switch connects any one of a plurality of first ports to any one of a plurality of second ports, outputs the optical signal input to the first port from the second port, and outputs the optical signal input to the second port from the first port; the transfer unit is connected to the first port of the optical switch; the circulator has a first port, a second port, and a third port; the first port is connected to the subscriber device; the second port is connected to a first port for an upstream direction among a plurality of first ports included in the optical switch; the third port is connected to a first port for a downstream direction among a plurality of first ports included in the optical switch; the circulator outputs an optical signal input to the first port to the first port for upstream direction connected to the second port, and outputs an optical signal input to the third port to the subscriber device connected to the first port; Optical communication method.

6. an optical switch connected to a plurality of optical transmission lines, and outputting an optical signal input from one of the optical transmission lines to another optical transmission line; a transfer unit converting the input optical signal from one-core transmission to two-core transmission, or from two-core transmission to one-core transmission, by multiplexing or demultiplexing the input optical signal between the subscriber device and the optical switch, and transferring the optical signal so that there is no interference between the upstream and downstream; determining an upstream port and a downstream port from among a plurality of ports of the forwarding unit based on information on wavelengths used for upstream and downstream assigned to the subscriber device; An optical communication method for controlling connections between ports of the optical switch in accordance with the determination result.

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