Optical communication system, communication control device, and optical path opening method

Abstract

This optical communication system comprises: a communication control unit for controlling the opening of an optical path between one of a plurality of first communication devices and one of a plurality of second communication devices; and an optical multiplexing / demultiplexing unit for multiplexing / demultiplexing the signal light of control signals respectively transmitted between each of the plurality of first communication devices and the communication control device after the opening of the optical path. The communication control unit gives permission for the transmission of an upstream control signal respectively to each of the first communication devices on the basis of the respective reciprocal transmission time of the signal light reciprocating between the communication control device and each of the first communication devices and thereby controls the receive timing of the upstream control signal transmitted from each of the plurality of first communication devices to the communication control device so as to be different from each other.

Description

[Technical Field]

[0001] The present invention relates to an optical communication system, a communication control device, and an optical path opening method. This application claims priority based on PCT / JP2022 / 020660, filed in Japan on May 18, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Research into photonics technology-based APN (All Photonics Network) is underway with the aim of realizing a new network infrastructure that will enable higher speeds, larger capacities, drastically lower latency, and lower power consumption, all of which are not possible with current network communications (see, for example, Non-Patent Document 1). By providing end-to-end, full-mesh optical path connections that utilize wavelengths, APN can flexibly provide a high-speed, large-capacity, dedicated wavelength network for each function, while minimizing latency.

[0003] In an APN, when a new subscriber device is connected to the network, the subscriber device management and control unit in the APN controller recognizes that the subscriber device has been connected. The subscriber device management and control unit assigns a new wavelength from among unused wavelengths to the subscriber device and instructs the subscriber device to set the wavelength. At the same time, the optical distribution control unit in the APN controller selects the optimal signal light path depending on the subscriber device's communication partner (e.g., another subscriber device), and sets the signal light transmission path (hereinafter referred to as the "optical path") using the optical distribution means in the Photonic Gateway (hereinafter referred to as the "Ph-GW"). In this way, automatic opening of end-to-end optical paths is realized.

[0004] As described above, in a conventional optical communication system, the optical distribution control unit in the Ph-GW sets up port-to-port connections using the optical distribution means so that a subscriber device can communicate with the subscriber device management and control unit at the time of initial connection. As soon as the registration, authentication, and wavelength setting of the subscriber device are completed, the optical distribution control unit changes the settings of the port-to-port connections using the optical distribution unit and opens an optical path that directly connects the newly connected subscriber device to another subscriber device with which the subscriber device will communicate. However, in the configuration of a conventional optical communication system, once the optical path is opened, the communication path between the subscriber device and the subscriber device management and control unit is cut off, resulting in a state in which there is no control channel for transmitting control signals sent and received between the subscriber device management and control unit and the subscriber device.

[0005] Therefore, a method can be considered in which an optical multiplexing / demultiplexing means for multiplexing / demultiplexing the signal light carrying the main signal and the signal light carrying the control signal is newly provided on the optical fiber transmission line, and a management and control port for communicating with the subscriber device after the optical path is opened is newly provided in the subscriber device management and control unit.By connecting the management and control port for communicating with the subscriber device after the optical path is opened to the optical multiplexing / demultiplexing means, the optical communication system can transmit upstream control signals from the subscriber device to the subscriber device management and control unit, and downstream control signals from the subscriber device management and control unit to the subscriber device, even after the optical path is opened. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Takuya Kanai, Kazuaki Honda, Yasunari Tanaka, Makoto Kaneko, Kazutaka Hara, Junichi Kani, Tomoaki Yoshida, “Photonic Gateway Supporting All-Photonics Networks”, Institute of Electronics, Information and Communication Engineers General Conference, B-8-20, March 2021 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when providing the subscriber device management and control unit with management and control ports for communication with the subscriber devices after the optical paths are opened as described above, the same number of management and control ports as the number of optical paths is required, which poses a problem of increasing the scale of the configuration of the subscriber device management and control unit.

[0008] The present invention aims to provide a technology that enables control signals to be sent and received between a subscriber device management control unit and a subscriber device before and after the opening of an optical path, while preventing the configuration of the subscriber device management control unit from becoming large. [Means for solving the problem]

[0009] One aspect of the present invention is an optical communication system comprising a communication control unit that controls the opening of an optical path between one of a plurality of first communication devices and one of a plurality of second communication devices, and an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after the optical path is opened, wherein the communication control unit controls the reception timing of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by allowing each of the plurality of first communication devices to transmit an upstream control signal based on the respective round-trip propagation times of the signal light traveling back and forth between the communication control unit and each of the plurality of first communication devices.

[0010] Another aspect of the present invention is a communication control device that controls the opening of an optical path between one of a plurality of first communication devices and one of a plurality of second communication devices, and the communication control device is a communication control device that has a control unit that controls the reception timing of the upstream control signal transmitted from each of the plurality of first communication devices to the communication control device to be different from each other by allowing each of the plurality of first communication devices to transmit an upstream control signal based on the respective round-trip propagation times of signal light traveling between the communication control device and each of the plurality of first communication devices.

[0011] Furthermore, one aspect of the present invention is a computer-implemented optical path opening method for an optical communication system having a communication control unit that controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices, and an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after the optical path is opened, the optical path opening method including: an acquisition step of acquiring information indicating each round-trip propagation time of the signal light traveling back and forth between the communication control unit and each of the plurality of first communication devices; and a control step of controlling the reception timing of the upstream control signal transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by allowing each of the plurality of first communication devices to transmit an upstream control signal based on the round-trip propagation time.

[0012] Another aspect of the present invention is an optical path opening method by a computer of a communication control device that controls the opening of an optical path between one of a plurality of first communication devices and one of a plurality of second communication devices, the optical path opening method comprising: an acquisition step of acquiring information indicating each round-trip propagation time of signal light traveling back and forth between the communication control device and each of the plurality of first communication devices; and a control step of controlling the reception timing of the upstream control signal transmitted from each of the plurality of first communication devices to the communication control device to be different from each other by allowing each of the plurality of first communication devices to transmit an upstream control signal based on the round-trip propagation time. [Effects of the Invention]

[0013] According to the present invention, it is possible to transmit and receive control signals between the subscriber device management and control unit and the subscriber devices before and after the opening of an optical path, while suppressing an increase in the scale of the configuration of the subscriber device management and control unit. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram for explaining a method for opening an optical path in a conventional optical communication system 1. [Figure 2] FIG. 1 is a diagram showing the overall configuration of a conventional optical communication system 1′. [Figure 3] 1 is a diagram illustrating the overall configuration of an optical communication system 1a according to a first embodiment of the present invention. [Figure 4] 3 is a flowchart showing the operation of the optical communication system 1a in the first embodiment of the present invention. [Figure 5] 10 is a diagram for explaining a method of adding a management control port b of a subscriber equipment management control unit 21 in the first embodiment of the present invention. FIG. [Figure 6] 10 is a diagram for explaining a method of adding a management control port b of a subscriber device management control unit 21 in the first embodiment of the present invention. FIG. [Figure 7] FIG. 2 is a diagram illustrating a configuration of an optical communication system according to a first modified example of the first embodiment of the present invention. [Figure 8] FIG. 2 is a diagram illustrating a configuration of an optical communication system according to a first modified example of the first embodiment of the present invention. [Figure 9] FIG. 10 is a diagram illustrating the configuration of an optical communication system 1c according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating the configuration of an optical communication system 1c according to a second embodiment of the present invention. [Figure 11] 10 is a flowchart showing the operation of an optical communication system 1c according to the second embodiment of the present invention. [Figure 12] FIG. 10 is a diagram illustrating the configuration of an optical communication system 1d according to a first modified example of the second embodiment of the present invention. [Figure 13] FIG. 10 is a diagram illustrating the configuration of an optical communication system 1d according to a first modified example of the second embodiment of the present invention. [Figure 14] FIG. 10 is a diagram illustrating a configuration of an optical communication system 1e according to a second modified example of the second embodiment of the present invention. [Figure 15] FIG. 10 is a diagram illustrating the configuration of a 1f optical communication system according to a third embodiment of the present invention. [Figure 16]FIG. 10 is a diagram illustrating the configuration of a 1f optical communication system according to a third embodiment of the present invention. [Figure 17] 10 is a flowchart showing the operation of the optical communication system 1f according to the third embodiment of the present invention. [Figure 18] FIG. 10 is a diagram for explaining the configuration of an optical communication system 1g according to a modified example of the third embodiment of the present invention. [Figure 19] FIG. 10 is a diagram illustrating the overall configuration of an optical communication system 1h according to a fourth embodiment of the present invention. [Figure 20] 10 is a flowchart showing the operation of an optical communication system 1h according to the fourth embodiment of the present invention. [Figure 21] FIG. 10 is a diagram showing the overall configuration of an optical communication system 1i according to a fifth embodiment of the present invention. [Figure 22] 10 is a flowchart showing the operation of the optical communication system 1i in the fifth embodiment of the present invention. [Figure 23] FIG. 13 is a diagram showing the overall configuration of an optical communication system 1j according to a first modified example of the fifth embodiment of the present invention. [Figure 24] FIG. 13 is a diagram illustrating the overall configuration of an optical communication system 1k according to a second modified example of the fifth embodiment of the present invention. [Figure 25] FIG. 11 is a diagram showing the overall configuration of an optical communication system 1l according to a sixth embodiment of the present invention. [Figure 26] 13 is a flowchart showing the operation of the optical communication system 1l in the sixth embodiment of the present invention. [Figure 27] FIG. 11 is a diagram illustrating the overall configuration of an optical communication system 1m according to a seventh embodiment of the present invention. [Figure 28] 13 is a flowchart showing the operation of the optical communication system 1m in the seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an optical communication system, a communication control device, and an optical path opening method according to an embodiment will be described with reference to the drawings.

[0016] For ease of understanding, the following description will first describe the configuration of an optical communication system 1, which is an example of a conventional optical communication system, as a comparison target with the optical communication system of the embodiment. Fig. 1 is a diagram for explaining a method for opening an optical path in the conventional optical communication system 1.

[0017] 1, the conventional optical communication system 1 includes a plurality of subscriber devices #k_1 (k=1, 2, . . . ), a plurality of subscriber devices #k_2 (k=1, 2, . . . ), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a wavelength multiplexing / demultiplexing unit 30-1 and a wavelength multiplexing / demultiplexing unit 30-2, a plurality of optical fiber transmission lines 50, and an optical communication network (NW) 60. The control unit 20-1 and the control unit 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0018] The light distribution means 10-1 and the light distribution means 10-2 are configured using, for example, optical switches, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs (Central Processing Units).

[0019] Hereinafter, as an example, an optical path opening method will be described in the case where subscriber device #k_1 is newly connected to the network and connects to subscriber device #k_2, which will be the communication partner, via the optical fiber transmission line 50, the optical distribution means 10-1, etc. Conversely, the optical path opening method in the case where subscriber device #k_2 is newly connected to the network and connects to subscriber device #k_1, which will be the communication partner, via the optical fiber transmission line 50, the optical distribution means 10-2, etc., is also similar to the configuration described below.

[0020] The light distribution means 10-1 has a plurality of ports. The light distribution means 10-1 is connected to a plurality of optical fiber transmission lines 50. The light distribution means 10-1 outputs an optical signal input from each port to a port that has a connection relationship set as a connection port for that port. The connection relationship between the plurality of ports can be changed and set as desired.

[0021] The subscriber device #k_1 is connected to the optical distribution unit 10-1 via the optical fiber transmission line 50. As shown in the upper diagram of Fig. 1, when the subscriber device #k_1 is initially connected to the network, the optical distribution control unit 22 changes the setting of the inter-port connection by the optical distribution unit 10-1 so that the subscriber device #k_1 and the subscriber device management control unit 21 can communicate with each other.

[0022] When the subscriber device #k_1 initially connects to the network, a management control signal required for registering and authenticating the subscriber device #k_1 to the network is exchanged between the subscriber device #k_1 and the subscriber device management control unit 21. Furthermore, when the subscriber device #k_1 initially connects to the network, a management control signal for instructing the emission wavelength to be used by the subscriber device #k_1 is transmitted from the subscriber device management control unit 21 to the subscriber device #k_1. As a channel for transmitting and receiving such a management control signal, for example, an AMCC (Auxiliary Management and Control Channel) or the like can be used.

[0023] 1, as soon as the registration, authentication, wavelength setting, etc. of the subscriber device #k_1 to the network are completed, the optical distribution control unit 22 again changes the setting of the inter-port connection by the optical distribution means 10-1 so that the optical signal transmitted from the subscriber device #k_1 is forwarded to the subscriber device #k_2 with which it is communicating. As a result, the optical communication system 1 can open an optical path that directly connects the subscriber device #k_1 and the subscriber device #k_2.

[0024] However, in such a configuration of the conventional optical communication system 1, once the optical path is opened, the communication path between the subscriber device #k_1 and the subscriber device management and control unit 21 is cut off, and therefore, as shown in the lower diagram of Fig. 1, there is no control channel for transmitting a downstream control signal transmitted from the subscriber device management and control unit 21 to the subscriber device #k_1, or for transmitting an upstream control signal transmitted from the subscriber device #k_1 to the subscriber device management and control unit 21. In this case, the subscriber device management and control unit 21 cannot monitor the status of the optical path and the status of the subscriber device #k_1 and perform optical path switching control, etc.

[0025] Therefore, a conceivable method is to provide an optical multiplexing / demultiplexing means 70 on the optical fiber transmission line 50 to multiplex / demultiplex an optical signal carrying a main signal and an optical signal carrying a control signal, and to provide a management and control port for communication with subscriber device #k_1 after the optical path is opened in the subscriber device management and control unit 21. By connecting the management and control port for communication with subscriber device #k_1 after the optical path is opened to the optical multiplexing / demultiplexing means 70, the optical communication system 1 becomes able to transmit upstream control signals from subscriber device #k_1 to the subscriber device management and control unit 21 and downstream control signals from the subscriber device management and control unit 21 to subscriber device #k_1 not only before the optical path is opened but also after the optical path is opened.

[0026] The following describes the overall configuration of an optical communication system 1', which is an example of a conventional optical communication system. Fig. 2 is an overall configuration diagram of the conventional optical communication system 1'. As shown in Fig. 2, the conventional optical communication system 1' includes a plurality of subscriber devices #k_1 (k = 1, 2, ...), a plurality of subscriber devices #k_2 (k = 1, 2, ...), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a wavelength multiplexing / demultiplexing unit 30-1 and a wavelength multiplexing / demultiplexing unit 30-2, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, and a plurality of optical multiplexing / demultiplexing units 70. The control units 20-1 and 20-2 are each configured to include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0027] The light distribution means 10-1 and the light distribution means 10-2 are configured using, for example, optical switches, etc. The optical multiplexing / demultiplexing means 70 is configured using, for example, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs.

[0028] In the following description, among the components of the conventional optical communication system 1' shown in Figure 2, those components having the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 described above will be given the same symbols and their descriptions may be omitted.

[0029] Note that while FIG. 2 illustrates the case where a signal is transmitted from subscriber device #k_1 (k=1, 2, . . .) to subscriber device #k_2 (k=1, 2, . . .), the same configuration as that described below is also applicable to the case where a signal is transmitted conversely from subscriber device #k_2 (k=1, 2, . . .) to subscriber device #k_1 (k=1, 2, . . .).

[0030] As shown in Fig. 2, an optical multiplexing / demultiplexing means 70 is provided for each of the multiple optical fiber transmission lines 50. The optical multiplexing / demultiplexing means 70 is configured using, for example, an optical coupler. The subscriber device management and control unit 21 is provided with a management and control port a, which is a management and control port for communication with subscriber device #k_1 before the optical path is opened, and a management and control port b, which is a management and control port for communication with subscriber device #k_1 after the optical path is opened. By connecting the optical multiplexing / demultiplexing means 70 and the management and control port b, the conventional optical communication system 1' can transmit upstream control signals from subscriber device #k_1 to the subscriber device management and control unit 21 and downstream control signals from the subscriber device management and control unit 21 to subscriber device #k_1, respectively, even after the optical path is opened.

[0031] The conventional optical communication system 1' shown in FIG. 2 controls the wavelength of an optical signal carrying a downstream control signal and the wavelength of an optical signal carrying a main signal to be different from each other. As a result, even if the frequency band of the downstream control signal and the frequency band of the main signal overlap, the conventional optical communication system 1' can prevent interference between the main signal and the downstream control signal during reception. Specifically, in the conventional optical communication system 1', subscriber device #k_1 separates the downstream control signal and the main signal, which have different wavelengths, and detects and demodulates the downstream control signal and the main signal, respectively. As a result, subscriber device #k_1 can receive both the downstream control signal and the main signal.

[0032] Before and after the optical path is opened, the subscriber device management and control unit 21 transmits downstream control signals addressed to the same subscriber device #k_1 from different management and control ports. Specifically, before the optical path is opened, the subscriber device management and control unit 21 transmits downstream control signals addressed to the subscriber device #k_1 from management and control port a, and after the optical path is opened, transmits downstream control signals addressed to the subscriber device #k_1 from management and control port b.

[0033] In a configuration such as the conventional optical communication system 1' shown in Figure 2, the same number of management control ports b (i.e., management control ports for communication with subscriber device #k_1 after the optical path is opened) as the number of optical paths to be opened are required. This results in an increase in the scale of the configuration of the subscriber device management control unit 21. An optical communication system according to an embodiment of the present invention that can solve this problem will be described below.

[0034] First Embodiment [Configuration of optical communication system] The configuration of the optical communication system 1a in the first embodiment will be described below. Fig. 3 is a diagram showing the overall configuration of the optical communication system 1a in the first embodiment of the present invention.

[0035] 3, the optical communication system 1a in the first embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . .), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a wavelength multiplexing / demultiplexing unit 30-1 and a wavelength multiplexing / demultiplexing unit 30-2, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1, and a plurality of second optical multiplexing / demultiplexing units 70-2. The control unit 20-1 and the control unit 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0036] The optical distribution means 10-1 and the optical distribution means 10-2 are configured using, for example, optical switches, etc. The first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2 are configured using, for example, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs.

[0037] In the following description, among the components of the optical communication system 1a in the first embodiment shown in Figure 3, those components having the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 above and the components of the conventional optical communication system 1' shown in Figure 2 above will be given the same symbols and their descriptions may be omitted.

[0038] Note that while Figure 3 illustrates the case where a signal is transmitted from subscriber device #k_1 (k = 1, 2,...) to subscriber device #k_2 (k = 1, 2,...), the same configuration as that described below is also used for the reverse case where a signal is transmitted from subscriber device #k_2 (k = 1, 2,...) to subscriber device #k_1 (k = 1, 2,...).

[0039] As shown in Figure 3, the optical communication system 1a in the first embodiment differs from the conventional optical communication system 1a' shown in Figure 2 above in that it is provided with a plurality of first optical multiplexing / demultiplexing means 70-1 and a plurality of second optical multiplexing / demultiplexing means 70-2.

[0040] The subscriber device #k_1 outputs an upstream control signal to be transmitted to the control unit 20-1 at a wavelength different from that of the carrier carrying the main signal. The subscriber device management control unit 21 of the control unit 20-2 outputs a downstream control signal to be transmitted to the subscriber device #k_2 at a wavelength different from that of the carrier carrying the main signal.

[0041] As shown in Fig. 3, a first optical multiplexing / demultiplexing unit 70-1 is provided in each of the multiple optical fiber transmission lines 50. The first optical multiplexing / demultiplexing unit 70-1 is configured using, for example, an optical filter. The subscriber device management and control unit 21 is provided with a management and control port a, which is a management and control port for communication with subscriber device #k_1 before the optical path is opened, and a management and control port b, which is a management and control port for communication with subscriber device #k_1 after the optical path is opened. By connecting the first optical multiplexing / demultiplexing unit 70-1 and the management and control port b, the optical communication system 1a in the first embodiment can transmit upstream control signals from subscriber device #k_1 to the subscriber device management and control unit 21 and downstream control signals from the subscriber device management and control unit 21 to subscriber device #k_1, even after the optical path is opened.

[0042] After the optical path is opened, the first optical multiplexing / demultiplexing means 70-1 transfers an upstream control signal transmitted from the subscriber device #k_1 to the subscriber device management and control unit 21 of the control unit 20-1 to the second optical multiplexing / demultiplexing means 70-2. After the optical path is opened, the first optical multiplexing / demultiplexing means 70-1 wavelength-multiplexes a signal light including a downstream control signal transmitted from the subscriber device management and control unit 21 of the control unit 20-2 to the subscriber device #k_2 and a signal light including a main signal.

[0043] The second optical multiplexing / demultiplexing means 70-2 is connected to a plurality of first optical multiplexing / demultiplexing means 70-1. The second optical multiplexing / demultiplexing means 70-2 multiplexes upstream control signals input from a plurality of first optical multiplexing / demultiplexing means 70-1 and outputs the multiplexed signals to management control port b of the subscriber equipment management control unit of the control unit 20-1. The second optical multiplexing / demultiplexing means 70-2 also splits downstream control signals output from management control port b of the subscriber equipment management control unit of the control unit 20-2 and outputs the splitted signals to the first optical multiplexing / demultiplexing means 70-1.

[0044] The subscriber device #k_1 outputs an optical signal including an upstream control signal only during the time period permitted by the subscriber device management control unit 21 of the control unit 20-1. The subscriber device #k_1 stops outputting the optical signal during the time period other than the time period permitted by the subscriber device management control unit 21 of the control unit 20-1. In other words, the optical signal including the upstream control signal is a burst optical signal.

[0045] The subscriber device management control unit 21 of the control unit 20-1 stores, for example, in a storage medium (not shown) provided in the own device, the round trip time (RTT) in the transmission of signal light between each of the subscriber devices #k_1 (k=1, 2, . . .) and its own subscriber device management control unit 21. The subscriber device management control unit 21 controls so that an upstream control signal transmitted from the subscriber device #k_1, which is a burst signal light, does not arrive at its own subscriber device management control unit 21 in the same time zone as upstream control signals transmitted from other subscriber devices #k_1.

[0046] Specifically, the subscriber device management control unit 21 of the control unit 20-1 refers to the RTT value stored in, for example, the storage medium (not shown). The subscriber device management control unit 21 issues a transmission permission for the optical signal including the upstream control signal to each subscriber device #k_1 at a timing determined based on the RTT value.

[0047] The subscriber device management and control unit 21 of the control unit 20-1 performs optical-electrical conversion on the signal light including the upstream control signal, and then identifies the subscriber device #k_1 that is the sender of the received upstream control signal based on the identifier included in the upstream control signal. For example, the identifier may be an ID (Identifier) ​​assigned to the subscriber device #k_1 by the subscriber device management and control unit 21 of the control unit 20-1, or the MAC (Media Access Control) address of the subscriber device #k_1.

[0048] The signal light including the downstream control signal is a signal light in which downstream control signals addressed to each subscriber device #k_2 are time-multiplexed. After optical-electrical conversion of the signal light including the downstream control signal, subscriber device #k_2 selectively receives a downstream control signal addressed to itself from the time-multiplexed downstream control signals based on an identifier included in the downstream control signal. For example, the identifier may be an ID assigned to subscriber device #k_2 by the subscriber device management control unit 21 of the control unit 20-2, or the MAC address of subscriber device #k_2.

[0049] The wavelength of the signal light including the upstream control signal transmitted by each subscriber device #k_1 is within the wavelength range that is transmitted through the input / output ports of the first optical multiplexing / demultiplexing means 70-1 from the port connected to the optical distribution means 10-1 (the port on the left side of the first optical multiplexing / demultiplexing means 70-1 connected to the optical distribution means 10-1 in FIG. 3) to the port connected to the second optical multiplexing / demultiplexing means 70-2 (the port on the upper right side of the first optical multiplexing / demultiplexing means 70-1 connected to the optical distribution means 10-1 in FIG. 3). Note that the wavelengths of the signal light including the upstream control signal transmitted by each subscriber device #k_1 may all be the same wavelength or may be different wavelengths.

[0050] The wavelength of the signal light including the downstream control signal transmitted by the subscriber device management control unit 21 of the control unit 20-2 is within the wavelength range that is transmitted from the port connected to the second optical multiplexing / demultiplexing unit 70-2 (the upper left port of the first optical multiplexing / demultiplexing unit 70-1 connected to the optical distribution unit 10-2 in Figure 3) to the port connected to the optical distribution unit 10-2 (the right port of the first optical multiplexing / demultiplexing unit 70-1 connected to the optical distribution unit 10-2 in Figure 3) among the input / output ports of the first optical multiplexing / demultiplexing unit 70-1.

[0051] The optical communication system 1a illustrated in Fig. 3 is configured such that there is a section in which the signal light (hereinafter referred to as "rightward signal light") transmitted from left to right in Fig. 3 (i.e., from subscriber device #k_1 to subscriber device #k_2) and the signal light (hereinafter referred to as "leftward signal light") transmitted from right to left (i.e., from subscriber device #k_2 to subscriber device #k_1) flow through the same optical fiber core. However, the configuration is not limited to this, and it is also possible to configure such that there is a section in which the rightward signal light and the leftward signal light flow through different optical fiber cores.

[0052] When there is a section in which rightward and leftward optical signals travel through the same optical fiber core (for example, as shown in FIG. 3), reflection of one optical signal in the optical fiber transmission line deteriorates the reception characteristics of the other optical signal (the optical signal traveling in the opposite direction). To prevent such deterioration of reception characteristics, for example, the subscriber device management control unit 21 sets the wavelengths of the rightward and leftward optical signals to different wavelengths, or issues transmission permissions to subscriber devices #k_1 and #k_2 so that the rightward and leftward optical signals are transmitted at different times.

[0053] In the optical communication system 1a illustrated in Fig. 3, the wavelength of the signal light including the upstream control signal and the wavelength of the signal light including the downstream control signal are different from each other. However, in the case where there is no section in which the rightward signal light and the leftward signal light flow through the same optical fiber core, as in the optical communication system 1a illustrated in Fig. 3, the wavelength of the signal light including the upstream control signal and the wavelength of the signal light including the downstream control signal can be the same wavelength.

[0054] 3, an optical distribution means (e.g., an optical switch) may be used instead of the second optical multiplexing / demultiplexing means 70-2 (e.g., an optical filter). In this case, for example, a configuration may be adopted in which the connection relationship between the ports of the optical distribution means is dynamically set in accordance with the timing at which the signal light including the upstream control signal from each subscriber device #k_1 arrives at the optical distribution means. Then, the arriving signal light including the upstream control signal may be received at the management control port b of the subscriber device management control unit 21 of the control unit 20-1.

[0055] [Operation of optical communication system] An example of the operation of the optical communication system 1a will be described below. Fig. 4 is a flowchart showing the operation of the optical communication system 1a in the first embodiment of the present invention. The operation of the optical communication system 1a shown in the flowchart of Fig. 4 starts when a new subscriber device #k_1 is connected to the network.

[0056] When a new subscriber device #k_1 is connected to the network, the subscriber device management control unit 21 of the control unit 20-1 detects the connection of the new subscriber device #k_1 to the network (step S101). When the subscriber device management control unit 21 detects the connection of the new subscriber device #k_1 to the network, the optical distribution control unit 22 changes the setting of the inter-port connection in the optical distribution means 10-1 so that the management control port a of the subscriber device management control unit 21 and the new subscriber device #k_1 are communicatively connected (step S102).

[0057] The subscriber device management control unit 21 assigns a wavelength to be assigned to the new subscriber device #k_1 from among the unused wavelengths. The subscriber device management control unit 21 transmits and receives management control information to the new subscriber device #k_1 using the management control port a. The subscriber device management control unit 21 instructs the new subscriber device #k_1 to set a wavelength, and assigns a wavelength to the subscriber device #k_1 (step S103).

[0058] When a wavelength is assigned to the new subscriber device #k_1, the optical distribution control unit 22 changes the setting of the port connection in the optical distribution means 10-1 again, thereby opening an optical path. At this time, the management control port b of the subscriber device management control unit 21 and the new subscriber device #k_1 are connected for communication (step S104).

[0059] The subscriber device management control unit 21 of the control unit 20-1 refers to the RTT value for each subscriber device #k_1 stored in advance in, for example, a storage medium (not shown) provided in the control unit. As described above, the RTT here refers to the RTT of the signal light between the subscriber device management control unit 21 of the control unit 20-1 and each subscriber device #k_1. The subscriber device management control unit 21 uses the management control port b to grant each subscriber device #k_1 permission to transmit an upstream control signal based on the RTT value so that the upstream control signals, which are burst signal light transmitted from each subscriber device #k_1, do not collide (step S105).

[0060] Each subscriber device #k_1 transmits an upstream control signal to the subscriber device management and control unit 21 at a timing corresponding to the transmission permission notified from the subscriber device management and control unit 21 (step S106). This completes the operation of the optical communication system 1a shown in the flowchart of FIG.

[0061] [Addition of management control port b] When new subscriber devices #k_1 are successively connected to the optical communication system 1a, it is conceivable that the number of subscriber devices #k_1 will exceed the number that can be accommodated by one management control port b of the subscriber device management control unit 21. In such a case, for example, it is sufficient to add a management control port b of the subscriber device management control unit 21 of the control unit 20-1.

[0062] 5 and 6 are diagrams for explaining a method for adding a management control port b of the subscriber device management control unit 21 in the first embodiment of the present invention. Note that Fig. 5 only shows the configuration in which the subscriber device management control unit 21 of the control unit 20-1 receives an upstream control signal, and does not show the configuration in which the subscriber device management control unit 21 of the control unit 20-2 transmits a downstream control signal.

[0063] 5 shows an example of the configuration of the optical communication system 1a when management control ports b, which transmit and receive signal light with the same wavelength, are added in parallel to the subscriber device management and control unit 21. In FIG. 5, the wavelengths of the signal light including the upstream control signals transmitted from each subscriber device #k_1 are the same. When a management control port b is added, a second optical multiplexing and demultiplexing unit 70-2 connected to the added management control port b is also added. In the optical communication system 1a shown in FIG. 5, it is predetermined which second optical multiplexing and demultiplexing unit 70-2 an upstream control signal transmitted from which subscriber device #k_1 will be transmitted to the subscriber device management and control unit 21 via.

[0064] Fig. 6 shows an example of the configuration of an optical communication system 1a when management control ports b, which transmit and receive signal light with different wavelengths, are added in parallel to the subscriber device management control unit 21. As shown in Fig. 6, a wavelength multiplexing and demultiplexing unit 30-3 is provided between the second optical multiplexing and demultiplexing unit 70-2 and the control unit 20-1. In Fig. 6, the wavelengths of signal light containing upstream control signals transmitted from subscriber devices #k_1 communicating with different management control ports b are different from each other.

[0065] The second optical multiplexing / demultiplexing means 70-2 multiplexes the optical signals including the upstream control signals transmitted from each subscriber device #k_1, and outputs the multiplexed optical signals to the wavelength multiplexing / demultiplexing means 30-3. The wavelength multiplexing / demultiplexing means 30-3 separates the multiplexed optical signals by wavelength, and transfers each of the separated optical signals (including the upstream control signals) to a management control port b (of the subscriber device management control unit 21) predetermined for each wavelength.

[0066] When a management control port b is added, it is sufficient to add an output destination for the signal light from the wavelength multiplexing / demultiplexing means 30-3, as shown in Fig. 6. Therefore, in this case, there is no need to add a second optical multiplexing / demultiplexing means 70-2 or the like in conjunction with the addition of the management control port b.

[0067] As described above, the optical communication system 1a according to the first embodiment of the present invention includes a plurality of first optical multiplexing / demultiplexing units 70-1 and a plurality of second optical multiplexing / demultiplexing units 70-2. The subscriber device #k_1 outputs an upstream control signal addressed to the subscriber device management and control unit 21 of the control unit 20-1 at a wavelength different from that of the optical carrier carrying the main signal. The subscriber device management and control unit 21 of the control unit 20-2 outputs a downstream control signal addressed to the subscriber device #k_2 at a wavelength different from that of the optical carrier carrying the main signal. After the optical path is opened, the first optical multiplexing / demultiplexing unit 70-1 transfers the upstream control signal light from the subscriber device #k_1 to the subscriber device management and control unit 21 of the control unit 20-1 to the second optical multiplexing / demultiplexing unit 70-2. After the optical path is opened, the first optical multiplexing / demultiplexing unit 70-1 wavelength-multiplexes the downstream control signal light from the subscriber device management and control unit 21 of the control unit 20-2 to the subscriber device #k_2 with the signal light of the main signal. The second optical multiplexing / demultiplexing means 70-2 is connected to each of the plurality of first optical multiplexing / demultiplexing means 70-1, multiplexes the upstream control signals input from each of the plurality of first optical multiplexing / demultiplexing means 70-1, and outputs the multiplexed signal to management control port b of the subscriber equipment management control unit 21 of the control unit 20-1. The second optical multiplexing / demultiplexing means 70-2 also branches the downstream control signal output from management control port b of the subscriber equipment management control unit 21 of the control unit 20-2, and outputs the multiple multiplexed signals to each of the plurality of first optical multiplexing / demultiplexing means 70-1.

[0068] As explained above, the subscriber device #k_1 outputs signal light (burst signal light) of an upstream control signal including an upstream control signal to the subscriber device management and control unit 21 of the control unit 20-1 only during the permitted time period. The subscriber device management and control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21, and gives each subscriber device #k_1 permission to transmit an upstream control signal based on the RTT value so that the upstream control signals, which are burst signal light transmitted from each subscriber device #k_1, do not collide.

[0069] With this configuration, the optical communication system 1a in the first embodiment of the present invention makes it possible to share the management control port b of the subscriber device management and control unit 21 among multiple subscriber devices #k_1. As a result, the optical communication system 1a eliminates the need to provide a management control port b of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1a in the first embodiment of the present invention, with a simple configuration of the subscriber device management and control unit 21, can send and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after an optical path is once opened.

[0070] (First Modification of the First Embodiment) An optical communication system according to a first modified example of the first embodiment of the present invention will now be described. Fig. 7 is a diagram illustrating the configuration of an optical communication system according to a first modified example of the first embodiment of the present invention. Note that Fig. 7 only illustrates the configuration in which the subscriber equipment management and control unit 21 of the control unit 20-1 receives an upstream control signal, and does not illustrate the configuration in which the subscriber equipment management and control unit 21 of the control unit 20-2 transmits a downstream control signal.

[0071] Note that while Figure 7 illustrates the case where a signal is transmitted from subscriber device #k_1 (k = 1, 2,...) to subscriber device #k_2 (k = 1, 2,...), the same configuration as that described below is also used for the reverse case where a signal is transmitted from subscriber device #k_2 (k = 1, 2,...) to subscriber device #k_1 (k = 1, 2,...).

[0072] 7, the optical communication system according to the first modification of the first embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . . ) (not shown), an optical distribution unit 10-1 and an optical distribution unit 10-2 (not shown), a control unit 20-1 and an optical distribution unit 20-2 (not shown), a wavelength multiplexing / demultiplexing unit 30-1 and an optical multiplexing / demultiplexing unit 30-2 (not shown), a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1, and a plurality of second optical multiplexing / demultiplexing units 70-2. The control units 20-1 and 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0073] The optical distribution means 10-1 and the optical distribution means 10-2 are configured using, for example, optical switches, etc. The first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2 are configured using, for example, optical couplers, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs.

[0074] In the following description, among the components of the optical communication system in the first variant of the first embodiment shown in Figure 7, the components that have the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication system 1a in the first embodiment shown in Figure 3 above will be given the same symbols and will not be described.

[0075] The configuration of the optical communication system in the first variant of the first embodiment shown in FIG. 7 differs from the configuration of the optical communication system 1a in the first embodiment shown in FIG. 3 above in that the subscriber device management control unit 21 further includes a management control port c.

[0076] The optical communication system according to the first modification of the first embodiment is used when a main signal is processed near the control units 20-1 and 20-2. The processing here refers to, for example, regenerative repeat processing, network function processing, and service function processing. As shown in FIG. 7, in the optical communication system according to the first modification of the first embodiment, the subscriber device management and control unit 21 issues transmission permission for the upstream control signal and the main signal to each subscriber device #k_1 so that the upstream control signal and the main signal are time-multiplexed onto the same wavelength. After completing the above processing, the subscriber device management and control unit 21 transmits the signal light including the main signal to the subscriber device #k_2 (not shown), which is the communication partner.

[0077] With the above-described configuration, in the optical communication system according to the first modification of the first embodiment of the present invention, each subscriber device #k_1 can time-multiplex and transmit an upstream control signal and a main signal on the same wavelength. Furthermore, with the above-described configuration, the optical communication system according to the first modification of the first embodiment of the present invention allows the management control port b of the subscriber device management and control unit 21 to be shared among multiple subscriber devices #k_1. This eliminates the need to provide a management control port b of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system according to the first modification of the first embodiment of the present invention, with a simple configuration of the subscriber device management and control unit 21, can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after an optical path is opened.

[0078] (Second Modification of the First Embodiment) An optical communication system 1b according to a second modification of the first embodiment of the present invention will be described below. The optical communication system 1a according to the first embodiment described above is configured to use wavelength multiplexing / demultiplexing means with wavelength selectivity, such as an optical filter, as the first optical multiplexing / demultiplexing means 70-1. In contrast, the optical communication system 1b according to the second modification of the first embodiment is configured to use optical multiplexing / demultiplexing means without wavelength selectivity, such as an optical coupler, as the first optical multiplexing / demultiplexing means 70-1.

[0079] 8 is a diagram illustrating the configuration of an optical communication system according to a second modification of the first embodiment of the present invention. As shown in FIG. 8, the optical communication system according to the second modification of the first embodiment of the present invention includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . .), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a wavelength multiplexing / demultiplexing unit 30-1 and a wavelength multiplexing / demultiplexing unit 30-2, a plurality of wavelength filters 40, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1, and a plurality of second optical multiplexing / demultiplexing units 70-2. The control units 20-1 and 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0080] The optical distribution means 10-1 and the optical distribution means 10-2 are configured using, for example, optical switches, etc. The second optical multiplexing / demultiplexing means 70-2 is configured using, for example, optical multiplexing / demultiplexing means without wavelength selectivity, such as an optical coupler, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs.

[0081] Note that Figure 8 illustrates an example of signal transmission from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as that described below applies to the reverse case of signal transmission from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0082] In the following description, among the components of the optical communication system in the second variant of the first embodiment shown in Figure 8, the components that have the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication system 1a in the first embodiment shown in Figure 3 above will be given the same symbols and will not be described.

[0083] The configuration of the optical communication system 1b in the second variant of the first embodiment shown in FIG. 8 differs from the configuration of the optical communication system 1a in the first embodiment shown in FIG. 3 above in that it further includes a wavelength filter 40.

[0084] In the optical communication system 1b according to the second modification of the first embodiment, as described above, an optical multiplexing / demultiplexing means without wavelength selectivity, such as an optical coupler, is used as the first optical multiplexing / demultiplexing means 70-1, and therefore a wavelength filter 40 is further provided. The wavelength filter 40 blocks signal light wavelengths including the main signal and transmits signal light including the upstream control signal. After the optical path is opened, the first optical multiplexing / demultiplexing means 70-1 branches a portion of the signal light including the upstream control signal transmitted from the subscriber device #k_1 to the subscriber device management control unit 21 of the control unit 20-1, and transfers the branched portion to the second optical multiplexing / demultiplexing means 70-2.

[0085] In addition, after the optical path is opened, the first optical multiplexing / demultiplexing means 70-1 wavelength-multiplexes the signal light including the downstream control signal and the signal light including the main signal, which are transmitted from the subscriber device management control unit 21 of the control unit 20-2 to the subscriber device #k_1.

[0086] The other signal light containing the upstream control signal branched by the first optical multiplexing / demultiplexing means 70-1 is also transferred to the wavelength multiplexing / demultiplexing means 30-1, but because the wavelength of the signal light containing the upstream control signal differs from the wavelength of the signal light containing the main signal, it is blocked by the wavelength multiplexing / demultiplexing means 30-1. As a result, the signal light containing the upstream control signal transmitted from subscriber device #k_1 is not transmitted beyond the wavelength multiplexing / demultiplexing means 30-1.

[0087] Therefore, similar to the optical communication system 1a in the first embodiment shown in FIG. 3 described above, when there is no section in which rightward signal light and leftward signal light flow through the same optical fiber core, as in the optical communication system 1b illustrated in FIG. 8, the wavelength of the signal light including the upstream control signal and the wavelength of the signal light including the downstream control signal can be made the same wavelength.

[0088] With the above-described configuration, the optical communication system 1b according to the second modification of the first embodiment can use an optical multiplexing / demultiplexing unit without wavelength selectivity, such as an optical coupler, as the first optical multiplexing / demultiplexing unit 70-1. Furthermore, with the above-described configuration, the optical communication system 1b according to the second modification of the first embodiment can share the management and control port b of the subscriber device management and control unit 21 among multiple subscriber devices #k_1. This eliminates the need to provide a management and control port b of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1b according to the second modification of the first embodiment of the present invention can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after an optical path is opened, with a simple configuration of the subscriber device management and control unit 21.

[0089] <Second embodiment> An optical communication system 1c according to a second embodiment of the present invention will now be described. Figures 9 and 10 are diagrams for explaining the configuration of the optical communication system 1c according to the second embodiment of the present invention. Figure 9 shows the state of the optical communication system 1c before the optical path of subscriber device #k_1 (k=1) is opened, and Figure 10 shows the state of the optical communication system 1c after the optical path of subscriber device #k_1 (k=1) is opened.

[0090] 9 and 10 illustrate the case where a signal is transmitted from subscriber device #k_1 (k=1, 2, . . .) to subscriber device #k_2 (k=1, 2, . . .), but the same configuration as that described below is also used for the case where a signal is transmitted conversely from subscriber device #k_2 (k=1, 2, . . .) to subscriber device #k_1 (k=1, 2, . . .).

[0091] 9 and 10, an optical communication system 1c in the second embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . .), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a wavelength multiplexing / demultiplexing unit 30-1 and a wavelength multiplexing / demultiplexing unit 30-2, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1, and a plurality of second optical multiplexing / demultiplexing units 70-2. The control unit 20-1 and the control unit 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0092] The optical distribution means 10-1 and the optical distribution means 10-2 are configured using, for example, optical switches, etc. The first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2 are configured using, for example, optical couplers, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs.

[0093] In the following description, among the components of the optical communication system 1c in the second embodiment shown in Figures 9 and 10, the components having the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication system 1a in the first embodiment shown in Figure 3 above will be given the same symbols and will not be described.

[0094] The configuration of the optical communication system 1c in the second embodiment shown in Figures 9 and 10 differs from the configuration of the optical communication system 1a in the first embodiment shown in Figure 3 above in that the same management control port (management control port c in Figure 9) of the subscriber device management control unit 21 is used to receive upstream control signals and send downstream control signals before and after the opening of the optical path.

[0095] Specifically, in the optical communication system 1a in the first embodiment shown in Fig. 3, the subscriber device management and control unit 21 includes a management control port a that transmits and receives information required for registration, authentication, and optical path opening with subscriber device #k_1 or subscriber device #k_2 before the optical path is opened, and a management control port b that transmits and receives control signals with subscriber device #k_1 or subscriber device #k_2 after the optical path is opened. In contrast, in the optical communication system 1c in the second embodiment shown in Fig. 9 and Fig. 10, one management control port c of the subscriber device management and control unit 21 transmits and receives control signals with subscriber device #k_1 or subscriber device #k_2 regardless of whether the optical path is opened or not.

[0096] 9 shows the state of the optical communication system 1c before the optical path of subscriber device #k_1 (k=1) is opened. The management and control port c of the subscriber device management and control unit 21 of the control unit 20-1 transmits and receives control signals to and from subscriber device #k_1 before the optical path is opened via the second optical multiplexing and demultiplexing unit 70-2 and the optical distribution unit 10-1. The management and control port c of the subscriber device management and control unit 21 of the control unit 20-1 transmits and receives control signals to and from subscriber devices after the optical path is opened via the second optical multiplexing and demultiplexing unit 70-2, the first optical multiplexing and demultiplexing unit 70-1, and the optical distribution unit 10-1. The management and control port c of the subscriber device management and control unit 21 of the control unit 20-2 transmits and receives control signals to and from subscriber device #k_2 before the optical path is opened via the second optical multiplexing and demultiplexing unit 70-2 and the optical distribution unit 10-2. In addition, the management control port c of the subscriber device management control unit 21 of the control unit 20-2 transmits and receives control signals to and from the subscriber device after the optical path is opened via the second optical multiplexing / demultiplexing means 70-2, the first optical multiplexing / demultiplexing means 70-1, and the optical distribution means 10-2.

[0097] When a new subscriber device #k_1 is connected to the optical distribution means 10-1, the optical distribution control unit 22 sets the port-to-port connection of the optical distribution means 10-1 so that the subscriber device #k_1 communicates with the management control port c of the subscriber device management control unit 21 of the control unit 20-1 via the optical distribution means 10-1 and the second optical multiplexing / demultiplexing means 70-2.

[0098] The subscriber device management control unit 21 of the control unit 20-1 transmits, from the management control port c, a signal (hereinafter referred to as a "search signal") to the subscriber device #k_1 newly connected to the optical distribution means 10-1, requesting that the subscriber device #k_1 return a response signal to its own subscriber device management control unit 21. The response signal is a signal that the subscriber device #k_1 returns to the subscriber device management control unit 21 in response to the search signal transmitted from the subscriber device management control unit 21 to the subscriber device #k_1 upon receiving the search signal.

[0099] In addition, the subscriber device management control unit 21 of the control unit 20-1 may be configured to periodically send a search signal to the subscriber device #k_1, or may be configured to send a search signal to the subscriber device #k_1 only when the connection of a new subscriber device #k_1 requesting the opening of an optical path is detected.

[0100] The subscriber device management control unit 21 of the control unit 20-1 measures the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management control unit 21 through the transmission and reception of the search signal, the response signal, and subsequent other control signals between the subscriber device #k_1 and the control unit 20-1.

[0101] Before opening an optical path for the newly connected subscriber device #k_1, the subscriber device management control unit 21 of the control unit 20-1 gives permission to transmit an upstream control signal to each of the subscriber devices #k_1 for which an optical path has already been opened. At this time, the permission to transmit the upstream control signal is given so that the signal light including the upstream control signal transmitted from another subscriber device #k_1 for which an optical path has already been opened does not reach its own subscriber device management control unit 21 during a period in which the signal light including the upstream control signal including a response signal returned by the newly connected subscriber device #k_1 in response to a search signal transmitted from its own subscriber device management control unit 21 can reach its own subscriber device management control unit 21.

[0102] Specifically, based on the RTT values ​​of the control signals between each subscriber device #k_1 and its own subscriber device management control unit 21, the subscriber device management control unit 21 identifies the timing of transmission permission so that the upstream control signals do not arrive at its own subscriber device management control unit 21 at the same timing, and gives transmission permission for the upstream control signal to each of the other subscriber devices #k_1 for which an optical path has already been opened at the above-mentioned identified timing.

[0103] 10 shows the state of the optical communication system 1c after the optical path of the subscriber device #k_1 (k=1) is opened. As soon as the registration, authentication, wavelength setting, etc. of the newly connected subscriber device #k_1 are completed, the optical distribution control unit 22 changes the setting of the port connection of the optical distribution means 10-1 so that the signal light including the main signal transmitted from the subscriber device #k_1 is forwarded to the subscriber device #k_2 with which it is communicating, and the optical distribution control unit 22 changes the setting of the port connection of the optical distribution means 10-2. As a result, a new optical path that directly connects the subscriber devices #k_1 and #k_2 is opened.

[0104] As with the optical communication system 1a in the first embodiment shown in FIG. 3 described above, when there is no section in which rightward signal light and leftward signal light flow through the same optical fiber core, as in the optical communication system 1c illustrated in FIG. 9, the wavelength of the signal light including the upstream control signal and the wavelength of the signal light including the downstream control signal can be made the same wavelength.

[0105] In the optical communication system 1c according to the second embodiment shown in Fig. 9, a wavelength-selective wavelength multiplexing / demultiplexing means such as an optical filter is used as the first optical multiplexing / demultiplexing means 70-1. However, as in the optical communication system 1b according to the second modification of the first embodiment shown in Fig. 8, an optical multiplexing / demultiplexing means without wavelength selectivity such as an optical coupler may be used as the first optical multiplexing / demultiplexing means 70-1. Even in a configuration using such an optical multiplexing / demultiplexing means without wavelength selectivity, as described above, if there is no section in which rightward signal light and leftward signal light flow through the same optical fiber core, the wavelength of the signal light including the upstream control signal and the wavelength of the signal light including the downstream control signal can be made the same wavelength.

[0106] 9, the optical distribution unit 10-1 and the optical distribution unit 10-2 are configured using, for example, a fiber cross connect (FXC) that outputs light input from each port to another port (which is set as a connection port corresponding to the input port) regardless of wavelength. For example, the optical distribution unit 10-1 and the optical distribution unit 10-2 may be a space optical switch using a micro electro mechanical system (MEMS) or a piezoelectric actuator.

[0107] [Operation of optical communication system] An example of the operation of the optical communication system 1c will be described below. Fig. 11 is a flowchart showing the operation of the optical communication system 1c in the second embodiment of the present invention. The operation of the optical communication system 1c shown in the flowchart of Fig. 11 starts when a new subscriber device #k_1 is connected to the network.

[0108] When a new subscriber device #k_1 is connected to the network, the subscriber device management control unit 21 of the control unit 20-1 detects the connection of the new subscriber device #k_1 to the network (step S201). When the subscriber device management control unit 21 detects the connection of the new subscriber device #k_1 to the network, the optical distribution control unit 22 changes the setting of the inter-port connection in the optical distribution unit 10-1 so that the management control port c of the subscriber device management control unit 21 and the new subscriber device #k_1 are communicatively connected (via the second optical multiplexing / demultiplexing unit 70-2 and the optical distribution unit 10-1) (step S202).

[0109] The subscriber device management control unit 21 assigns a wavelength to be assigned to the new subscriber device #k_1 from among the unused wavelengths. The subscriber device management control unit 21 transmits and receives management control information to the new subscriber device #k_1 using the management control port c. The subscriber device management control unit 21 instructs the new subscriber device #k_1 to set a wavelength, and assigns a wavelength to the subscriber device #k_1 (step S203).

[0110] In addition, the subscriber device management control unit 21 measures the RTT of the control signal between the subscriber device #k_1 and its own subscriber device management control unit 21 through the transmission and reception of management control information (e.g., a search signal, a response signal, and other subsequent control signals) between the subscriber device #k_1 and itself (step S204).

[0111] When a wavelength is assigned to the new subscriber device #k_1, the optical distribution control unit 22 opens an optical path by reconfiguring the port connection settings in the optical distribution unit 10-1. At this time, the management control port c of the subscriber device management control unit 21 and the new subscriber device #k_1 are communicatively connected (via the second optical multiplexing / demultiplexing unit 70-2, the first optical multiplexing / demultiplexing unit 70-1, and the optical distribution unit 10-1) (step S205).

[0112] The subscriber device management control unit 21 of the control unit 20-1 uses the management control port c to grant permission to each subscriber device #k_1 to transmit an upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, based on the RTT value measured for each subscriber device #k_1, so that the upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, does not collide (step S206).

[0113] Each subscriber device #k_1 transmits an upstream control signal to the subscriber device management and control unit 21 at a timing corresponding to the transmission permission notified from the subscriber device management and control unit 21 (step S207). This completes the operation of the optical communication system 1c shown in the flowchart of FIG.

[0114] As described above, the optical communication system 1c according to the second embodiment of the present invention includes a plurality of first optical multiplexing / demultiplexing units 70-1 and a plurality of second optical multiplexing / demultiplexing units 70-2. The subscriber device #k_1 outputs an upstream control signal addressed to the subscriber device management and control unit 21 of the control unit 20-1 at a wavelength different from that of the optical carrier carrying the main signal. The subscriber device management and control unit 21 of the control unit 20-2 outputs a downstream control signal addressed to the subscriber device #k_2 at a wavelength different from that of the optical carrier carrying the main signal. After the optical path is opened, the first optical multiplexing / demultiplexing unit 70-1 transfers the signal light of the upstream control signal from the subscriber device #k_1 to the subscriber device management and control unit 21 of the control unit 20-1 to the second optical multiplexing / demultiplexing unit 70-2. After the optical path is opened, the first optical multiplexing / demultiplexing unit 70-1 wavelength-multiplexes the signal light of the downstream control signal from the subscriber device management and control unit 21 of the control unit 20-2 to the subscriber device #k_2 with the signal light of the main signal. The second optical multiplexing / demultiplexing means 70-2 is connected to each of the plurality of first optical multiplexing / demultiplexing means 70-1, multiplexes the upstream control signals input from each of the plurality of first optical multiplexing / demultiplexing means 70-1, and outputs the multiplexed signals to the management and control port c of the subscriber equipment management and control unit 21 of the control unit 20-1. The second optical multiplexing / demultiplexing means 70-2 also branches the downstream control signal output from the management and control port c of the subscriber equipment management and control unit 21 of the control unit 20-2, and outputs the multiple multiplexed signals to each of the plurality of first optical multiplexing / demultiplexing means 70-1.

[0115] As explained above, the subscriber device #k_1 outputs signal light (burst signal light) of an upstream control signal including an upstream control signal to the subscriber device management and control unit 21 of the control unit 20-1 only during the permitted time period. The subscriber device management and control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21, and grants permission to each subscriber device #k_1 to transmit an upstream control signal based on the value of the RTT so that the burst signal light transmitted from each subscriber device #k_1 does not collide.

[0116] Furthermore, in the optical communication system 1c of the second embodiment, the same management control port c transmits and receives control signals to and from the subscriber device #k_1 before and after the optical path is opened. The management control port c transmits and receives control signals to and from the subscriber device #k_1 before the optical path is opened via the second optical multiplexing / demultiplexing means 70-2 and the optical distribution means 10-1. Also, the management control port c transmits and receives control signals to and from the subscriber device #k_1 after the optical path is opened via the second optical multiplexing / demultiplexing means 70-2, the first optical multiplexing / demultiplexing means 70-1, and the optical distribution means 10-1.

[0117] With the above-described configuration, the optical communication system 1c according to the second embodiment of the present invention uses the same management control port c to transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 before and after the optical path is opened. This allows the configuration of the subscriber device management and control unit 21 to be further simplified compared to the optical communication system 1a according to the first embodiment. Furthermore, with the above-described configuration, the optical communication system 1c according to the second embodiment allows the management control port c of the subscriber device management and control unit 21 to be shared among multiple subscriber devices #k_1. As a result, the optical communication system 1c does not need to provide a management control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1c according to the second embodiment of the present invention has a simple configuration of the subscriber device management and control unit 21 and can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after the optical path is opened.

[0118] (First modified example of the second embodiment) An optical communication system 1d according to a first modified example of the second embodiment of the present invention will now be described. Figures 12 and 13 are diagrams for explaining the configuration of the optical communication system 1d according to the first modified example of the second embodiment of the present invention. Figure 12 shows the state of the optical communication system 1d before the optical path of subscriber device #k_1 (k=1) is opened, and Figure 13 shows the state of the optical communication system 1d after the optical path of subscriber device #k_1 (k=1) is opened.

[0119] 12 and 13 illustrate the case where a signal is transmitted from subscriber device #k_1 (k=1, 2, . . .) to subscriber device #k_2 (k=1, 2, . . .), but the same configuration as that described below is also used for the case where a signal is transmitted conversely from subscriber device #k_2 (k=1, 2, . . .) to subscriber device #k_1 (k=1, 2, . . .).

[0120] 12 and 13, an optical communication system 1d according to a first modification of the second embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . .), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a wavelength multiplexing / demultiplexing unit 30-1 and a wavelength multiplexing / demultiplexing unit 30-2, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1, and a plurality of second optical multiplexing / demultiplexing units 70-2. The control unit 20-1 and the control unit 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0121] The optical distribution means 10-1 and the optical distribution means 10-2 are configured using, for example, optical switches, etc. The first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2 are configured using, for example, optical couplers, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs.

[0122] In the following description, among the components of the optical communication system 1d in the first variant of the second embodiment shown in Figures 12 and 13, the components having the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication system 1c in the second embodiment shown in Figures 9 and 10 above will be given the same symbols and will not be described.

[0123] The configuration of the optical communication system 1d in the first variant of the second embodiment shown in Figures 12 and 13 differs from the configuration of the optical communication system 1c in the second embodiment shown in Figures 9 and 10 described above in that the position where the first optical multiplexing and demultiplexing means 70-1 is located in the optical communication system 1d is different.

[0124] Specifically, in the configuration of the optical communication system 1c in the second embodiment shown in the above-mentioned Figures 9 and 10, the first optical multiplexing / demultiplexing means 70-1 is arranged between the optical distribution means 10-1 and the wavelength multiplexing / demultiplexing means 30-1, and between the optical distribution means 10-2 and the wavelength multiplexing / demultiplexing means 30-2, whereas in the configuration of the optical communication system 1d in the first variant of the second embodiment shown in Figures 12 and 13, the first optical multiplexing / demultiplexing means 70-1 is arranged between the optical distribution means 10-1 and the subscriber device #k_1, and between the optical distribution means 10-2 and the subscriber device #k_2.

[0125] In the optical communication system 1d according to the first modification of the second embodiment, the wavelength multiplexing / demultiplexing unit 30-1 and the wavelength multiplexing / demultiplexing unit 30-2 wavelength-multiplex the signal light of each optical path. For example, the wavelength multiplexing / demultiplexing unit 30-1 and the wavelength multiplexing / demultiplexing unit 30-2 are configured using an arrayed waveguide grating (AWG) or a wavelength selective switch (WSS).

[0126] With the above-described configuration, the optical communication system 1d according to the first modification of the second embodiment can have the first optical multiplexing / demultiplexing unit 70-1 disposed between the optical distribution unit 10-1 and the subscriber device #k_1, and between the optical distribution unit 10-2 and the subscriber device #k_2. Furthermore, with the above-described configuration, the optical communication system 1d according to the first modification of the second embodiment can share the management and control port c of the subscriber device management and control unit 21 among multiple subscriber devices #k_1. This eliminates the need to provide a management and control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1d according to the first modification of the second embodiment of the present invention can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after an optical path is opened, with a simple configuration of the subscriber device management and control unit 21.

[0127] (Second Modification of the Second Embodiment) An optical communication system 1e according to a second modified example of the second embodiment of the present invention will be described below. Fig. 14 is a diagram for explaining the configuration of an optical communication system 1e according to a second modified example of the second embodiment of the present invention.

[0128] Note that while Figure 14 illustrates the case where a signal is transmitted from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), the same configuration as that described below is also used for the reverse case where a signal is transmitted from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0129] 14, an optical communication system 1e according to a second modification of the second embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . .), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1, and a plurality of second optical multiplexing / demultiplexing units 70-2. The control unit 20-1 and the control unit 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0130] The first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2 are configured using, for example, optical couplers, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs.

[0131] In the following description, among the components of the optical communication system 1e in the second variant of the second embodiment shown in Figure 14, the components that have the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication system 1c in the second embodiment shown in Figures 9 and 10 above will be given the same symbols and will not be described.

[0132] The configuration of the optical communication system 1e in the second variant of the second embodiment shown in FIG. 14 differs from the configuration of the optical communication system 1d in the first variant of the second embodiment shown in the above-mentioned FIGS. 12 and 13 in that it does not include wavelength multiplexing / demultiplexing means 30-1 and wavelength multiplexing / demultiplexing means 30-2.

[0133] When the light distribution unit 10-1 and the light distribution unit 10-2 can set a transmission path for each wavelength, the wavelength multiplexing / demultiplexing unit 30-1 and the wavelength multiplexing / demultiplexing unit 30-2 can be omitted, as in the configuration of an optical communication system 1e in a second modification of the second embodiment shown in Fig. 14. As the light distribution unit 10-1 and the light distribution unit 10-2 that can set a transmission path for each wavelength, for example, a WSS or a multicast switch (MCS) can be used.

[0134] By having the above-described configuration, the optical communication system 1e in the second modified example of the second embodiment of the present invention makes it possible to omit the installation of the wavelength multiplexing / demultiplexing unit 30-1 and the wavelength multiplexing / demultiplexing unit 30-2. Furthermore, by having the above-described configuration, the optical communication system 1e in the second modified example of the second embodiment of the present invention makes it possible to share the management control port c of the subscriber device management and control unit 21 among multiple subscriber devices #k_1. As a result, the optical communication system 1e does not need to provide a management control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1e in the second modified example of the second embodiment of the present invention has a simple configuration of the subscriber device management and control unit 21, and once an optical path is opened, it is possible to send and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1.

[0135] <Third embodiment> An optical communication system 1f according to the third embodiment of the present invention will now be described. Figures 15 and 16 are diagrams for explaining the configuration of the optical communication system 1f according to the third embodiment of the present invention. Figure 15 shows the state of the optical communication system 1c before the optical path of the subscriber device #k_1 (k=1) is opened, and Figure 16 shows the state of the optical communication system 1c after the optical path of the subscriber device #k_1 (k=1) is opened.

[0136] 15 and 16 illustrate the case where a signal is transmitted from subscriber device #k_1 (k=1, 2, . . .) to subscriber device #k_2 (k=1, 2, . . .), but the same configuration as that described below is also used for the case where a signal is transmitted conversely from subscriber device #k_2 (k=1, 2, . . .) to subscriber device #k_1 (k=1, 2, . . .).

[0137] 15 and 16, an optical communication system 1c according to the third embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . .), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a wavelength multiplexing / demultiplexing unit 30-1 and a wavelength multiplexing / demultiplexing unit 30-2, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1 and a plurality of second optical multiplexing / demultiplexing units 70-2, a plurality of dispersion compensation units 80-1 and a plurality of dispersion compensation units 80-2. The control units 20-1 and 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0138] The optical distribution means 10-1 and the optical distribution means 10-2 are configured using, for example, optical switches, etc. The first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2 are configured using, for example, optical couplers, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs, etc. The dispersion compensation means 80-1 and the dispersion compensation means 80-2 are configured using, for example, dispersion shifted fibers.

[0139] In the following description, among the components of the optical communication system 1f in the third embodiment shown in Figures 15 and 16, components having the same configuration as the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, the components of the optical communication system 1a in the first embodiment shown in Figure 3 above, and the components of the optical communication system 1c in the second embodiment shown in Figures 9 and 10 above will be given the same symbols and will not be described.

[0140] The configuration of the optical communication system 1f in the third embodiment shown in Figures 15 and 16 differs from the configuration of the optical communication system 1c in the second embodiment shown in Figures 9 and 10 described above in that a plurality of dispersion compensation means 80-1 are connected to the optical distribution means 10-1, and a plurality of dispersion compensation means 80-2 are connected to the optical distribution means 10-2.

[0141] As an example, the optical communication system 1f in the third embodiment has a configuration in which a plurality of dispersion compensating means 80-1 and a plurality of dispersion compensating means 80-2 are added to the configuration of the optical communication system 1d in the first modified example of the second embodiment shown in Figures 12 and 13. However, the configuration is not limited to this, and for example, the optical communication system 1f may have a configuration in which a plurality of dispersion compensating means 80-1 and a plurality of dispersion compensating means 80-2 are added to the configuration of the optical communication system 1a in the first embodiment shown in Figure 3 or to the configuration of the optical communication system 1c in the second embodiment shown in Figures 9 and 10.

[0142] When an optical path is opened, the subscriber device management and control units 21 of the control units 20-1 and 20-2 determine whether chromatic dispersion compensation is necessary along the route of the optical path. Furthermore, if chromatic dispersion compensation is necessary, the subscriber device management and control units 21 determine the amount of chromatic dispersion compensation. Then, if the subscriber device management and control units 21 determine that chromatic dispersion compensation is necessary, the light distribution control unit 22 sets the connection relationship between the ports of the light distribution units 10-1 and 10-2 so that the light passes through the dispersion compensation units 80-1 and 80-2 that achieve the required amount of chromatic dispersion compensation.

[0143] Before opening an optical path, in the process of transmitting and receiving control signals to and from a subscriber device #k_1 newly connected to the optical distribution means 10-1, the subscriber device management and control unit 21 of the control unit 20-1 measures the RTT of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21. Then, the subscriber device management and control unit 21 multiplies the speed of light propagating through the optical fiber transmission line 50 by the measured RTT value to calculate the distance between its own subscriber device management and control unit 21 and the newly connected subscriber device #k_1.

[0144] Here, when the first optical multiplexing / demultiplexing means 70-1, the second optical multiplexing / demultiplexing means 70-2, the subscriber device management control unit 21 (control unit 20-1), and the optical distribution unit 10-1 are located close to each other, the subscriber device management control unit 21 of the control unit 20-1 can calculate the distance between the optical distribution unit 10-1 and the newly connected subscriber device #k_1.

[0145] Similarly, when the first optical multiplexing / demultiplexing means 70-1, the second optical multiplexing / demultiplexing means 70-2, the subscriber device management control unit 21 (control unit 20-2), and the optical distribution unit 10-2 are located close to each other, the subscriber device management control unit 21 of the control unit 20-2 can calculate the distance between the optical distribution unit 10-2 and the subscriber device #k_2, which is the communication partner of the newly connected subscriber device #k_1.

[0146] As a result, if the distance between the optical distribution means 10-1 and the optical distribution means 10-2 is known, the subscriber device management control unit 21 of the control unit 20-1 can calculate the distance between the subscriber devices that are the endpoints of the optical path to be opened (i.e., between the newly connected subscriber device #k_1 and the subscriber device #k_2 that is the communication partner of the subscriber device #k_1).

[0147] The subscriber device management control unit 21 of the control unit 20-1 and the control unit 20-2 calculates the accumulated chromatic dispersion amount when the optical path is opened, using the wavelengths to be assigned to the newly connected subscriber devices #k_1 and #k_2 and the calculated distance between the subscriber devices that are the endpoints of the opened optical path. In addition, the subscriber device management control unit 21 calculates the allowable chromatic dispersion amount for obtaining a predetermined reception quality based on the characteristics (e.g., signal speed, modulation method, etc.) of the optical transceiver (not shown) in the newly connected subscriber device #k_1.

[0148] Then, the optical distribution control units 22 of the control units 20-1 and 20-2 set the connection relationship between the ports of the optical distribution unit 10-1 and the optical distribution unit 10-2 so that the transmission path passes through the dispersion compensation unit 80-1 and the dispersion compensation unit 80-2, which compensate for the difference between the accumulated chromatic dispersion amount calculated by the subscriber device management control unit 21 and the allowable chromatic dispersion amount.

[0149] In the optical communication system 1f according to the third embodiment, the wavelength multiplexing / demultiplexing means 30-1 and the wavelength multiplexing / demultiplexing means 30-2 wavelength-multiplex the signal light of each optical path. For example, the wavelength multiplexing / demultiplexing means 30-1 and the wavelength multiplexing / demultiplexing means 30-2 are configured using AWG, WSS, or the like.

[0150] [Operation of optical communication system] An example of the operation of the optical communication system 1f will be described below. Fig. 17 is a flowchart showing the operation of the optical communication system 1f in the third embodiment of the present invention. The operation of the optical communication system 1f shown in the flowchart of Fig. 17 starts when a new subscriber device #k_1 is connected to the network.

[0151] When a new subscriber device #k_1 is connected to the network, the subscriber device management control unit 21 of the control unit 20-1 detects the connection of the new subscriber device #k_1 to the network (step S301). The subscriber device management control unit 21 assigns a wavelength to be assigned to the new subscriber device #k_1 from among unused wavelengths. The subscriber device management control unit 21 transmits and receives management control information to the new subscriber device #k_1 using the management control port c. The subscriber device management control unit 21 instructs the new subscriber device #k_1 to set a wavelength and assigns a wavelength to the subscriber device #k_1 (step S302).

[0152] In addition, the subscriber device management control unit 21 of the control unit 20-1 measures the RTT of the control signal between the subscriber device #k_1 and its own subscriber device management control unit 21 through the transmission and reception of management control information (e.g., a search signal, a response signal, and other subsequent control signals) between the subscriber device #k_1 and itself (step S303).

[0153] The subscriber device management and control unit 21 of the control unit 20-1 calculates the distance (hereinafter also referred to as the "first distance") between its own subscriber device management and control unit 21 and the newly connected subscriber device #k_1 by multiplying the speed of light propagating through the optical fiber transmission line 50 by the measured RTT value (step S304). Furthermore, the subscriber device management and control unit 21 calculates the distance (hereinafter also referred to as the "second distance") between the newly connected subscriber device #k_1 and subscriber device #k_2, the communication partner of the newly connected subscriber device #k_1, based on the first distance and the known distance between the optical distribution unit 10-1 and the optical distribution unit 10-2 (step S305).

[0154] The subscriber device management control unit 21 of the control unit 20-1 calculates the accumulated chromatic dispersion amount when the optical path is opened, using the second distance and the wavelength assigned to the newly connected subscriber device #k_1. The subscriber device management control unit 21 also calculates the allowable chromatic dispersion amount for obtaining a predetermined reception quality based on the characteristics (e.g., signal speed, modulation method, etc.) of the optical transceiver (not shown) in the newly connected subscriber device #k_1 (step S306).

[0155] When a wavelength is assigned to the new subscriber device #k_1, the optical distribution control units 22 of the control units 20-1 and 20-2 set the connection relationship between the ports of the optical distribution unit 10-1 and 10-2 so that the optical path passes through the dispersion compensation unit 80-1 and the dispersion compensation unit 80-2, which compensate for the difference between the accumulated chromatic dispersion amount calculated by the subscriber device management control unit 21 and the allowable chromatic dispersion amount (step S307).

[0156] When the optical path is opened, the subscriber device management control unit 21 of the control unit 20-1 uses the management control port c to give each subscriber device #k_1 permission to send an upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, based on the RTT value measured for each subscriber device #k_1, so that the upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, does not collide (step S308).

[0157] Each of the subscriber devices #k_1 transmits an upstream control signal to the subscriber device management and control unit 21 at a timing corresponding to the transmission permission notified by the subscriber device management and control unit 21 (step S309).

[0158] Each dispersion compensator 80-1 compensates for the chromatic dispersion of the signal light including the main signal transmitted from the subscriber device #k_1 by an appropriate amount of chromatic dispersion compensation, and transmits the signal light toward the communicating subscriber device #k_2 (step S310). This completes the operation of the optical communication system 1f shown in the flowchart of FIG.

[0159] As described above, the optical communication system 1f according to the third embodiment of the present invention includes a plurality of first optical multiplexing / demultiplexing units 70-1 and a plurality of second optical multiplexing / demultiplexing units 70-2. The subscriber device #k_1 outputs an upstream control signal addressed to the subscriber device management and control unit 21 of the control unit 20-1 at a wavelength different from that of the optical carrier carrying the main signal. The subscriber device management and control unit 21 of the control unit 20-2 outputs a downstream control signal addressed to the subscriber device #k_2 at a wavelength different from that of the optical carrier carrying the main signal. After the optical path is opened, the first optical multiplexing / demultiplexing unit 70-1 transfers the upstream control signal light from the subscriber device #k_1 to the subscriber device management and control unit 21 of the control unit 20-1 to the second optical multiplexing / demultiplexing unit 70-2. After the optical path is opened, the first optical multiplexing / demultiplexing unit 70-1 wavelength-multiplexes the signal light of the downstream control signal from the subscriber device management and control unit 21 of the control unit 20-2 to the subscriber device #k_2 with the signal light of the main signal. The second optical multiplexing / demultiplexing means 70-2 is connected to each of the plurality of first optical multiplexing / demultiplexing means 70-1, multiplexes the upstream control signals input from each of the plurality of first optical multiplexing / demultiplexing means 70-1, and outputs the multiplexed signals to the management and control port c of the subscriber equipment management and control unit 21 of the control unit 20-1. The second optical multiplexing / demultiplexing means 70-2 also branches the downstream control signal output from the management and control port c of the subscriber equipment management and control unit 21 of the control unit 20-2, and outputs the multiple multiplexed signals to each of the plurality of first optical multiplexing / demultiplexing means 70-1.

[0160] As explained above, the subscriber device #k_1 outputs signal light (burst signal light) of an upstream control signal including an upstream control signal to the subscriber device management and control unit 21 of the control unit 20-1 only during the permitted time period. The subscriber device management and control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21, and grants permission to each subscriber device #k_1 to transmit an upstream control signal based on the RTT value so that the burst signal light transmitted from each subscriber device #k_1 does not collide.

[0161] Furthermore, the optical communication system 1f in the third embodiment includes a plurality of dispersion compensators 80-1 and a plurality of dispersion compensators 80-2. The subscriber device management and control units 21 of the control units 20-1 and 20-2 determine whether chromatic dispersion compensation is required when an optical path is opened, and if it is determined that chromatic dispersion compensation is required, calculate the required amount of chromatic dispersion compensation. The light distribution control units 22 of the control units 20-1 and 20-2 set the connection relationship between the ports of the light distribution unit 10-1 and the light distribution unit 10-2 so that the light passes through the dispersion compensator 80-1 and the dispersion compensator 80-2 that satisfies the required amount of chromatic dispersion compensation.

[0162] With this configuration, the optical communication system 1f according to the third embodiment measures the distance between the subscriber device management and control unit 21 and the subscriber device #k_1 based on the measurement result of the RTT of the control signal between the subscriber device management and control unit 21 of the control unit 20-1 and the subscriber device #k_1. Therefore, the optical communication system 1f does not need to add a function specialized for measuring the distance between the subscriber device management and control unit 21 and the subscriber device #k_1. The optical communication system 1f includes multiple dispersion compensators 80-1 and 80-2, and can perform the necessary chromatic dispersion compensation for each optical path based on the measured distance. This allows the optical communication system 1f according to the third embodiment to extend the transmission distance of the main signal. Furthermore, the optical communication system 1f according to the third embodiment of the present invention allows the management and control port c of the subscriber device management and control unit 21 to be shared among multiple subscriber devices #k_1. This eliminates the need to provide a management and control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1f in the third embodiment of the present invention has a simple configuration of the subscriber device management control unit 21, and once the optical path is opened, it is possible to send and receive control signals between the subscriber device management control unit 21 and the subscriber device #k_1.

[0163] (Modification of the third embodiment) An optical communication system 1g according to a modification of the third embodiment of the present invention will now be described. Fig. 18 is a diagram illustrating the configuration of the optical communication system 1g according to the modification of the third embodiment of the present invention.

[0164] Note that Figure 18 illustrates an example of signal transmission from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as that described below applies to the reverse case of signal transmission from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0165] 18, an optical communication system 1g according to a modification of the third embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, . . .), a plurality of subscriber devices #k_2 (k=1, 2, . . .), an optical distribution unit 10-1 and an optical distribution unit 10-2, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission lines 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing units 70-1, a plurality of second optical multiplexing / demultiplexing units 70-2, a plurality of dispersion compensation units 80-1, and a plurality of dispersion compensation units 80-2. The control unit 20-1 and the control unit 20-2 each include a subscriber device management control unit 21 and an optical distribution control unit 22.

[0166] The first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2 are configured using, for example, optical couplers, optical filters, etc. The control units 20-1 and 20-2 are configured using, for example, processors such as CPUs, etc. The dispersion compensation means 80-1 and 80-2 are configured using, for example, dispersion shifted fibers.

[0167] In the following description, among the components provided in the optical communication system 1g in the modified example of the third embodiment shown in Figure 18, the components provided in the conventional optical communication system 1 shown in Figure 1 described above, the components provided in the conventional optical communication system 1' shown in Figure 2 described above, the components provided in the optical communication system 1a in the first embodiment shown in Figure 3 described above, the components provided in the optical communication system 1c in the second embodiment shown in Figures 9 and 10 described above, and the components provided in the optical communication system 1f in the third embodiment shown in Figures 15 and 16 described above will be given the same symbols and will not be described.

[0168] The configuration of the optical communication system 1g in the modified example of the third embodiment shown in Figures 15 and 16 differs from the configuration of the optical communication system 1f in the third embodiment shown in Figures 15 and 16 described above in that it does not include wavelength multiplexing / demultiplexing means 30-1 and wavelength multiplexing / demultiplexing means 30-2.

[0169] If the light distribution means 10-1 and the light distribution means 10-2 can set transmission paths for each wavelength, the wavelength multiplexing / demultiplexing means 30-1 and the wavelength multiplexing / demultiplexing means 30-2 can be omitted, as in the configuration of an optical communication system 1g in the third embodiment shown in Fig. 18. Note that the same dispersion compensation means 80-1 and the dispersion compensation means 80-2 can be shared between optical paths that require the same amount of chromatic dispersion compensation.

[0170] As the light distribution means 10-1 and the light distribution means 10-2 capable of setting a transmission path for each wavelength, for example, a WSS or a multicast switch (MCS) can be used.

[0171] By having the above-described configuration, the optical communication system 1g in the first modified example of the third embodiment makes it possible to omit the installation of the wavelength multiplexing / demultiplexing unit 30-1 and the wavelength multiplexing / demultiplexing unit 30-2. Furthermore, by having the above-described configuration, the optical communication system 1g in the first modified example of the third embodiment makes it possible to share the management control port c of the subscriber device management and control unit 21 among multiple subscriber devices #k_1. As a result, the optical communication system 1g does not need to provide a management control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1g in the first modified example of the second embodiment of the present invention has a simple configuration of the subscriber device management and control unit 21, and once an optical path is opened, it is possible to send and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1.

[0172] As described above, the optical communication systems in the first to third embodiments and the modified examples of each of these embodiments are all systems in which the network configuration between subscriber device #k_1 and the optical distribution means 10-1 and the network configuration between subscriber device #k_2 and the optical distribution means 10-2 are PP (Point to Point) connection topologies, and the network configuration between subscriber device #k_1 and the control unit 20-1 and the network configuration between subscriber device #k_2 and the control unit 20-2 are P-MP (Point to Multipoint) connection topologies.

[0173] On the other hand, the optical communication systems in the fourth to seventh embodiments described below and the modified examples of each of these embodiments are all systems in which the network configuration between subscriber device #k_1 and the optical distribution means 10-1, the network configuration between subscriber device #k_2 and the optical distribution means 10-2, the network configuration between subscriber device #k_1 and the control unit 20-1, and the network configuration between subscriber device #k_2 and the control unit 20-2 are all P-MP (Point to Multipoint) connection topologies.

[0174] Furthermore, the optical communication systems in the fourth to seventh embodiments and each of the modified examples of each of these embodiments described below are all configured in the same way as the optical communication systems in the second to third embodiments and each of the modified examples of each of these embodiments described above, in that the same management control port c of the subscriber device management control unit 21 sends and receives control signals to and from subscriber device #k_1 and subscriber device #k_2, regardless of whether the optical path is opened or not.

[0175] <Fourth embodiment> An optical communication system 1h according to the fourth embodiment of the present invention will now be described. Fig. 19 is a diagram showing the overall configuration of the optical communication system 1h according to the fourth embodiment of the present invention.

[0176] As shown in FIG. 19, the optical communication system 1h in the fourth embodiment includes a plurality of subscriber devices #k_1 (k=1, 2, ...), a plurality of subscriber devices #k_2 (k=1, 2, ...), an optical distribution means 10-1 and an optical distribution means 10-2, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission paths 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing means 70-1, and a plurality of second optical multiplexing / demultiplexing means 70-2.

[0177] In the following description, among the components of the optical communication system 1h in the fourth embodiment shown in Figure 19, the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication systems in each of the above-mentioned embodiments will be given the same symbols and their descriptions may be omitted.

[0178] The optical distribution means 10-1 is configured to include a route switching means 15-1 and a plurality of wavelength multiplexing / demultiplexing means 30-1. The optical distribution means 10-2 is configured to include a route switching means 15-2 and a plurality of wavelength multiplexing / demultiplexing means 30-2. The control units 20-1 and 20-2 are configured to include a subscriber device management control unit 21 and an optical distribution control unit 22, respectively.

[0179] As shown in Figure 19, in the optical communication system 1h of the fourth embodiment, a first optical multiplexing / demultiplexing means 70-1 and a second optical multiplexing / demultiplexing means 70-2 are provided in the optical fiber transmission path 50 between the subscriber device #k_1 and the optical distribution means 10-1, and in the optical fiber transmission path 50 between the subscriber device #k_2 and the optical distribution means 10-2, respectively.

[0180] The first optical multiplexing / demultiplexing means 70-1 is connected to a plurality of subscriber devices #k_1 or a plurality of subscriber devices #k_2. The first optical multiplexing / demultiplexing means 70-1 is also connected to a port of the path switching means 15-1 of the optical distribution means 10-1 or a port of the path switching means 15-2 of the optical distribution means 10-2 via the second optical multiplexing / demultiplexing means 70-2.

[0181] The subscriber device #k_1 transmits the signal light carrying the upstream control signal to the control unit 20-1 at a wavelength different from the wavelength assigned as the signal light carrying the main signal. C_UP It shall be transmitted by

[0182] On the other hand, the subscriber device management and control unit 21 transmits the signal light carrying the downstream control signal to the subscriber device #k_2 at a wavelength different from the wavelength assigned as the signal light carrying the main signal. C_DOWN It shall be transmitted by

[0183] Note that Figure 19 illustrates an example of signal transmission from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as described below applies to the reverse case of signal transmission from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0184] The first optical multiplexing / demultiplexing means 70-1 multiplexes signal light carrying one or more main signals and signal light carrying upstream control signals input from each connected subscriber device #k_1, and outputs the multiplexed signal light toward the second optical multiplexing / demultiplexing means 70-2. The first optical multiplexing / demultiplexing means 70-1 also branches the signal light multiplexed with signal light carrying one or more main signals and signal light carrying downstream control signals input from the second optical multiplexing / demultiplexing means 70-2, and outputs the branched signal light toward each connected subscriber device #k_2.

[0185] The first optical multiplexing / demultiplexing means 70-1 is configured using, for example, an optical coupler or an optical splitter.

[0186] The second optical multiplexing / demultiplexing means 70-2 separates the signal light input from the first optical multiplexing / demultiplexing means 70-1 into signal light carrying the main signal and signal light carrying the upstream control signal. The second optical multiplexing / demultiplexing means 70-2 then outputs the signal light carrying the main signal toward the optical distribution means 10-1, and outputs the signal light carrying the upstream control signal toward the subscriber equipment management and control unit 21. The second optical multiplexing / demultiplexing means 70-2 also multiplexes the signal light carrying the main signal input from the optical distribution means 10-2 with the signal light carrying the downstream control signal input from the subscriber equipment management and control unit 21, and outputs the multiplexed signal light toward the first optical multiplexing / demultiplexing means 70-1.

[0187] The second optical multiplexing / demultiplexing means is configured using, for example, a wavelength filter.

[0188] The optical distribution means 10-1 and the optical distribution means 10-2 have optical distribution means that multiplex signal light input from a lower port in any combination and output it from any upper port, and output signal light input from the upper port from any lower port.

[0189] As shown in Fig. 19, the light distribution unit 10-1 includes a path switching unit 15-1 and a plurality of wavelength multiplexing / demultiplexing units 30-1, and functions as a light distribution unit. The light distribution unit 10-2 includes a path switching unit 15-2 and a plurality of wavelength multiplexing / demultiplexing units 30-2, and functions as a light distribution unit. The path switching unit 15-1 is configured using, for example, a matrix switch. The wavelength multiplexing / demultiplexing unit 30-1 is configured using, for example, an optical coupler or a wavelength selective switch (WSS). The configurations of the light distribution unit 10-1 and the light distribution unit 10-2 shown in Fig. 19 are merely examples.

[0190] As another configuration example, it is also possible to configure optical distribution means 10-1 functioning as an optical distribution means by combining, for example, path switching means 15-1 configured using a multicast switch made up of multiple 1xM optical switches and multiple Nx1 optical couplers (or splitters) with, for example, wavelength multiplexing / demultiplexing means 30-1 configured using a WSS having multiple input ports and multiple output ports. Similarly, it is also possible to configure optical distribution means 10-2 functioning as an optical distribution means by combining, for example, path switching means 15-2 configured using a multicast switch made up of multiple 1xM optical switches and multiple Nx1 optical couplers (or splitters) with, for example, wavelength multiplexing / demultiplexing means 30-2 configured using a WSS having multiple input ports and multiple output ports.

[0191] The subscriber device #k_1 outputs an optical signal including an upstream control signal only during the time period permitted by the subscriber device management control unit 21 of the control unit 20-1. The subscriber device #k_1 stops outputting the optical signal during the time period other than the time period permitted by the subscriber device management control unit 21 of the control unit 20-1. In other words, the optical signal including the upstream control signal is a burst optical signal.

[0192] The subscriber device management control unit 21 of the control unit 20-1 stores, for example, in a storage medium (not shown) provided in its own device, the round trip time (RTT) in the transmission of signal light between each of the subscriber devices #k_1 (k=1, 2, . . .) and its own subscriber device management control unit 21. The subscriber device management control unit 21 controls so that an upstream control signal transmitted from the subscriber device #k_1, which is a burst signal light, does not arrive at its own subscriber device management control unit 21 in the same time zone as upstream control signals transmitted from other subscriber devices #k_1.

[0193] Specifically, the subscriber device management control unit 21 of the control unit 20-1 refers to the RTT value stored in, for example, the storage medium (not shown). The subscriber device management control unit 21 issues a transmission permission for the optical signal including the upstream control signal to each subscriber device #k_1 at a timing determined based on the RTT value.

[0194] The subscriber device management and control unit 21 of the control unit 20-1 performs optical-electrical conversion on the signal light including the upstream control signal, and then identifies the subscriber device #k_1 that is the sender of the received upstream control signal based on the identifier included in the upstream control signal. For example, the identifier can be an ID assigned to the subscriber device #k_1 by the subscriber device management and control unit 21 of the control unit 20-1, or the MAC address of the subscriber device #k_1.

[0195] The signal light including the downstream control signal is a signal light in which downstream control signals addressed to each subscriber device #k_2 are time-multiplexed. After optical-electrical conversion of the signal light including the downstream control signal, subscriber device #k_2 selectively receives a downstream control signal addressed to itself from the time-multiplexed downstream control signals based on an identifier included in the downstream control signal. For example, the identifier may be an ID assigned to subscriber device #k_2 by the subscriber device management control unit 21 of the control unit 20-2, or the MAC address of subscriber device #k_2.

[0196] The wavelength λ of the signal light including the upstream control signal transmitted by each subscriber device #k_1 C_UPis a wavelength within the wavelength range that is transmitted from the port connected to the first optical multiplexing / demultiplexing means 70-1 (the left port of the second optical multiplexing / demultiplexing means 70-2 connected to the first optical multiplexing / demultiplexing means 70-1 in FIG. 19) to the port connected to the subscriber equipment management and control unit 21 (the upper port of the second optical multiplexing / demultiplexing means 70-2 connected to the subscriber equipment management and control unit 21 in FIG. 19) among the input / output ports of the second optical multiplexing / demultiplexing means 70-2. Note that the wavelengths of the signal lights including the upstream control signals transmitted by each subscriber device #k_1 may all be the same wavelength or may be different wavelengths.

[0197] The wavelength λ of the signal light including the downstream control signal transmitted by the subscriber equipment management control unit 21 of the control unit 20-2 C_DOWN is a wavelength within the wavelength range that is transmitted from the port connected to the subscriber equipment management and control unit 21 (the upper port of the second optical multiplexing and demultiplexing means 70-2 connected to the subscriber equipment management and control unit 21 in Figure 19) to the port connected to the first optical multiplexing and demultiplexing means 70-1 (the right port of the second optical multiplexing and demultiplexing means 70-2 connected to the first optical multiplexing and demultiplexing means 70-1 in Figure 19) among the input / output ports of the second optical multiplexing and demultiplexing means 70-2.

[0198] The optical communication system 1h illustrated in Fig. 19 is configured such that there is a section in which rightward signal light transmitted from left to right (i.e., from subscriber device #k_1 to subscriber device #k_2) and leftward signal light transmitted from right to left (i.e., from subscriber device #k_2 to subscriber device #k_1) flow through the same optical fiber core. However, the configuration is not limited to this, and it is also possible to configure such that there is a section in which the rightward signal light and the leftward signal light flow through different optical fiber cores.

[0199] When there is a section in which rightward and leftward optical signals travel through the same optical fiber core (for example, as shown in FIG. 19), reflection of one optical signal in the optical fiber transmission line deteriorates the reception characteristics of the other optical signal (the optical signal traveling in the opposite direction). To prevent such deterioration of reception characteristics, for example, the subscriber device management control unit 21 sets the wavelengths of the rightward and leftward optical signals to different wavelengths, or issues transmission permissions to subscriber devices #k_1 and #k_2 so that the rightward and leftward optical signals are transmitted at different times.

[0200] In the optical communication system 1h illustrated in Fig. 19, the wavelength of the signal light including the upstream control signal and the wavelength of the signal light including the downstream control signal are different from each other. However, if there is no section in which the rightward signal light and the leftward signal light flow through the same optical fiber core, the wavelength of the rightward signal light and the wavelength of the leftward signal light can be the same. For example, in this case, the wavelength of the signal light including the upstream control signal and the wavelength of the signal light including the downstream control signal can be the same.

[0201] [Operation of optical communication system] An example of the operation of the optical communication system 1h will be described below. Fig. 20 is a flowchart showing the operation of the optical communication system 1h in the fourth embodiment of the present invention. The operation of the optical communication system 1h shown in the flowchart of Fig. 20 starts when a new subscriber device #k_1 is connected to the network.

[0202] When a new subscriber device #k_1 is connected to the network, the subscriber device management control unit 21 of the control unit 20-1 detects the connection of the new subscriber device #k_1 to the network (step S401).

[0203] When the subscriber device management control unit 21 detects that a new subscriber device #k_1 has been connected to the network, it assigns a wavelength to be allocated to the new subscriber device #k_1 from among unused wavelengths. The subscriber device management control unit 21 transmits and receives management control information to the new subscriber device #k_1 using the management control port c. The subscriber device management control unit 21 instructs the new subscriber device #k_1 to set a wavelength and allocates a wavelength to the new subscriber device #k_1. This opens an optical path (step S402).

[0204] The subscriber device management control unit 21 of the control unit 20-1 uses the management control port c to grant permission to each subscriber device #k_1 to transmit an upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, based on the RTT value measured for each subscriber device #k_1, so that the upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, does not collide (step S403).

[0205] Each subscriber device #k_1 transmits an upstream control signal to the subscriber device management and control unit 21 at a timing corresponding to the transmission permission notified from the subscriber device management and control unit 21 (step S404). This completes the operation of the optical communication system 1h shown in the flowchart of FIG.

[0206] As described above, the optical communication system 1h according to the fourth embodiment of the present invention includes a plurality of first optical multiplexing / demultiplexing means 70-1 and a plurality of second optical multiplexing / demultiplexing means 70-2. The subscriber device #k_1 outputs a main signal and an upstream control signal addressed to the subscriber device management and control unit 21 of the control unit 20-1 to the first optical multiplexing / demultiplexing means 70-1 at mutually different wavelengths. The first optical multiplexing / demultiplexing means 70-1 multiplexes signals transmitted from the plurality of subscriber devices #k_1 and outputs the multiplexed signals to the second optical multiplexing / demultiplexing means 70-2. The second optical multiplexing / demultiplexing means 70-2 separates the multiplexed signal input from the first optical multiplexing / demultiplexing means 70-1 into a main signal and an upstream control signal, outputs the main signal to the optical distribution means 10-1, and outputs the upstream control signal to the management and control port c of the subscriber device management and control unit 21 of the control unit 20-1. Furthermore, the subscriber device management and control unit 21 of the control unit 20-2 outputs a downstream control signal addressed to subscriber device #k_2 at a wavelength different from that of the optical carrier carrying the main signal. The second optical multiplexing and demultiplexing unit 70-2 multiplexes the main signal input from the optical distribution unit 10-2 with the downstream control signal input from management and control port C of the subscriber device management and control unit 21, and outputs the multiplexed signal toward the first optical multiplexing and demultiplexing unit 70-1. The first optical multiplexing and demultiplexing unit 70-1 branches the signal input from the second optical multiplexing and demultiplexing unit 70-2 and outputs it toward multiple subscriber devices #k_2.

[0207] Then, the subscriber device #k_1 outputs signal light (burst signal light) of an upstream control signal including an upstream control signal to the subscriber device management and control unit 21 of the control unit 20-1 only during the permitted time period. The subscriber device management and control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21, and grants permission to each subscriber device #k_1 to transmit an upstream control signal based on the RTT value so that the burst signal light transmitted from each subscriber device #k_1 does not collide.

[0208] Furthermore, in the optical communication system 1h of the fourth embodiment, the same management control port c transmits and receives control signals to and from subscriber device #k_1 before and after the optical path is opened. The management control port c transmits and receives upstream control signals to and from subscriber device #k_1 before the optical path is opened via the second optical multiplexing / demultiplexing means 70-2 and the optical distribution means 10-1. Similarly, the management control port c transmits and receives upstream control signals to and from subscriber device #k_1 after the optical path is opened via the second optical multiplexing / demultiplexing means 70-2 and the first optical multiplexing / demultiplexing means 70-1.

[0209] With the above-described configuration, the optical communication system 1h according to the fourth embodiment of the present invention transmits and receives control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 using the same management and control port c before and after the optical path is opened. This allows the configuration of the subscriber device management and control unit 21 to be further simplified compared to the optical communication system 1a according to the first embodiment. Furthermore, with the above-described configuration, the optical communication system 1h according to the fourth embodiment allows the management and control port c of the subscriber device management and control unit 21 to be shared among multiple subscriber devices #k_1. As a result, the optical communication system 1h does not need to provide a management and control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1h according to the fourth embodiment of the present invention can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after the optical path is opened, with a simple configuration of the subscriber device management and control unit 21.

[0210] <Fifth embodiment> An optical communication system 1i according to the fifth embodiment of the present invention will be described below. Fig. 21 is a diagram showing the overall configuration of the optical communication system 1i according to the fifth embodiment of the present invention.

[0211] As shown in FIG. 21, the optical communication system 1i in the fifth embodiment includes a plurality of subscriber devices #k_1 (k=1, 2,...), a plurality of subscriber devices #k_2 (k=1, 2,...), an optical distribution means 10-1 and an optical distribution means 10-2, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission paths 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing means 70-1, a plurality of second optical multiplexing / demultiplexing means 70-2, a plurality of third optical multiplexing / demultiplexing means 70-3, a plurality of fourth optical multiplexing / demultiplexing means 70-4, and a plurality of optical amplification means 75.

[0212] In the following description, among the components of the optical communication system 1i in the fifth embodiment shown in Figure 21, the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication systems in each of the above-mentioned embodiments will be given the same symbols and their descriptions may be omitted.

[0213] The optical distribution means 10-1 is configured to include a route switching means 15-1 and a plurality of wavelength multiplexing / demultiplexing means 30-1. The optical distribution means 10-2 is configured to include a route switching means 15-2 and a plurality of wavelength multiplexing / demultiplexing means 30-2. The control units 20-1 and 20-2 are configured to include a subscriber device management control unit 21 and an optical distribution control unit 22, respectively.

[0214] As shown in Figure 21, in the optical communication system 1i of the fifth embodiment, similar to the optical communication system 1h of the fourth embodiment shown in Figure 19 described above, a first optical multiplexing / demultiplexing means 70-1 and a second optical multiplexing / demultiplexing means 70-2 are provided in the optical fiber transmission path 50 between the subscriber device #k_1 and the optical distribution means 10-1, and in the optical fiber transmission path 50 between the subscriber device #k_2 and the optical distribution means 10-2, respectively.

[0215] Furthermore, as shown in FIG. 21, in the optical communication system 1i of the fifth embodiment, a third optical multiplexing / demultiplexing means 70-3, an optical amplifying means 75, and a second optical multiplexing / demultiplexing means 70-2 are provided in the optical fiber transmission line 50 between the first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2.

[0216] The first optical multiplexing / demultiplexing means 70-1 is connected to a plurality of subscriber devices #k_1 or a plurality of subscriber devices #k_2. The first optical multiplexing / demultiplexing means 70-1 is also connected to a port of the optical distribution means 10-1 or 10-2 via a third optical multiplexing / demultiplexing means 70-3, an optical amplifying means 75, a fourth optical multiplexing / demultiplexing means 70-4, and a second optical multiplexing / demultiplexing means 70-2.

[0217] The subscriber device #k_1 transmits the signal light carrying the upstream control signal to the control unit 20-1 at a wavelength different from the wavelength assigned as the signal light carrying the main signal. C_UP It shall be transmitted by

[0218] On the other hand, the subscriber device management and control unit 21 transmits the signal light carrying the downstream control signal to the subscriber device #k_2 at a wavelength different from the wavelength assigned as the signal light carrying the main signal. C_DOWN It shall be transmitted by

[0219] Note that Figure 21 illustrates the case where a signal is transmitted from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as described below applies to the case where a signal is transmitted conversely from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0220] The first optical multiplexing / demultiplexing means 70-1 multiplexes the signal light carrying one or more main signals and the signal light carrying upstream control signals input from each connected subscriber device #k_1, and outputs the multiplexed signal to the third optical multiplexing / demultiplexing means 70-3. The first optical multiplexing / demultiplexing means 70-1 also branches the signal light carrying one or more main signals and the signal light carrying downstream control signals input from the third optical multiplexing / demultiplexing means 70-3, and outputs the multiplexed signal to each connected subscriber device #k_2.

[0221] The first optical multiplexing / demultiplexing means 70-1 is configured using, for example, an optical coupler or a splitter. When an optical coupler or a splitter is used as the first optical multiplexing / demultiplexing means 70-1, the signal light undergoes branching loss when passing through the first optical multiplexing / demultiplexing means 70-1. In order to compensate for this branching loss, the optical communication system 1i in the fifth embodiment includes an optical amplification means 75 between the first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2.

[0222] In the optical communication system 1i according to the fifth embodiment, the wavelength λ of the signal light including the upstream control signal is C_UP and the wavelength λ of the signal light including the downstream control signal C_DOWN However, if the wavelength is outside the wavelength band in which the optical amplifying means 75 has gain, as shown in Figure 21, the third optical multiplexing / demultiplexing means 70-3 and the fourth optical multiplexing / demultiplexing means 70-4 transmit the signal light including the upstream control signal and the signal light including the downstream control signal bypassing the optical amplifying means 75.

[0223] For example, in order for the subscriber device management and control unit 21 to receive the upstream control signal with a quality equal to or higher than a predetermined quality (for example, a bit error rate equal to or lower than a predetermined value), and for the subscriber devices #k_1 and #k_2 to receive the downstream control signal with a quality equal to or higher than a predetermined quality (for example, a bit error rate equal to or lower than a predetermined value), if it is necessary to amplify the optical intensity between the subscriber device management and control unit 21 and the subscriber devices #k_1 and #k_2, the wavelength λ of the signal light including the upstream control signal may be further increased. C_UP and an optical amplifier having a gain for a wavelength λ of signal light including a downstream control signal. C_DOWNand an optical amplifying means having a gain for the third optical multiplexing / demultiplexing means 70-3 and the fourth optical multiplexing / demultiplexing means 70-4 may be provided in the detour path between the third optical multiplexing / demultiplexing means 70-3 and the fourth optical multiplexing / demultiplexing means 70-4.

[0224] For the upstream control signal, the third optical multiplexing / demultiplexing means 70-3 demultiplexes the multiplexed signal light input from the first optical multiplexing / demultiplexing means 70-1 into signal light including the main signal and signal light including the upstream control signal. The third optical multiplexing / demultiplexing means 70-3 outputs the signal light including the main signal toward the optical amplifying means 75, and outputs the signal light including the upstream control signal toward the fourth optical multiplexing / demultiplexing means 70-4 via a detour route that does not pass through the optical amplifying means 75.

[0225] For the upstream control signal, the fourth optical multiplexing / demultiplexing means 70-4 multiplexes the signal light including the main signal input from the optical amplifying means 75 with the signal light including the upstream control signal input from the third optical multiplexing / demultiplexing means 70-3 via a detour route that does not pass through the optical amplifying means 75. The fourth optical multiplexing / demultiplexing means 70-4 outputs the multiplexed signal light toward the second optical multiplexing / demultiplexing means 70-2.

[0226] For the downstream control signal, the fourth optical multiplexing / demultiplexing means 70-4 demultiplexes the multiplexed signal light input from the second optical multiplexing / demultiplexing means 70-2 into signal light including the main signal and signal light including the downstream control signal. The fourth optical multiplexing / demultiplexing means 70-4 outputs the signal light including the main signal toward the optical amplifying means 75, and outputs the signal light including the downstream control signal toward the third optical multiplexing / demultiplexing means 70-3 via a detour route that does not pass through the optical amplifying means 75.

[0227] For the downstream control signal, the third optical multiplexing / demultiplexing means 70-3 multiplexes the signal light including the main signal input from the optical amplifying means 75 with the signal light including the downstream control signal input from the fourth optical multiplexing / demultiplexing means 70-4 via a detour route that does not pass through the optical amplifying means 75. The fourth optical multiplexing / demultiplexing means 70-4 outputs the multiplexed signal light toward the first optical multiplexing / demultiplexing means 70-1.

[0228] The third optical multiplexing / demultiplexing means 70-3 and the fourth optical multiplexing / demultiplexing means 70-4 are configured using, for example, wavelength filters.

[0229] As in the fourth embodiment, in the optical communication system 1i in the fifth embodiment, the signal light carrying the upstream control signal and the signal light carrying the downstream control signal are transmitted and received using a PON (Passive Optical Network) system. Therefore, for transmitting and receiving the signal light carrying the upstream control signal and the signal light carrying the downstream control signal, a technically mature and widely used optical transceiver for PON can be used.

[0230] For example, in GE-PON (Gigabit Ethernet-PON) and G-PON (Gigabit-PON), which are PONs with a communication speed of 1 Gbit / s, the wavelength bands of the signal light carrying the upstream control signal and the downstream control signal are within the O-band (Original band) (1290-1330 nm) and the S-band (Short wavelength band) (1480-1500 nm), respectively. On the other hand, the signal light carrying the main signal has a longer transmission distance than the wavelength bands of the signal light carrying the upstream control signal and the downstream control signal. Therefore, it is expected that the C-band (Conventional band), which has low transmission loss in a typical single-mode fiber, will be used as the wavelength band of the signal light carrying the main signal.

[0231] For example, the wavelength band used by digital coherent transceivers for long-distance transmission is generally the C-band. In this case, optical filters that separate signal light with wavelengths in the C-band from signal light with wavelengths in wavelength bands other than the C-band are used as the third optical multiplexing / demultiplexing means 70-3 and the fourth optical multiplexing / demultiplexing means 70-4, and an erbium-doped fiber amplifier (EDFA) or a semiconductor optical amplifier (SOA) having a gain band in the C-band is used as the optical amplifying means 75. This allows the signal light carrying the upstream control signal and the signal light carrying the downstream control signal to be diverted so as not to pass through the optical amplifying means 75, and the signal intensity of the signal light carrying the main signal can be amplified by the optical amplifying means 75.

[0232] [Operation of optical communication system] An example of the operation of the optical communication system 1i will be described below. Fig. 22 is a flowchart showing the operation of the optical communication system 1i in the fifth embodiment of the present invention. The operation of the optical communication system 1i shown in the flowchart of Fig. 22 starts when a new subscriber device #k_1 is connected to the network.

[0233] When a new subscriber device #k_1 is connected to the network, the subscriber device management control unit 21 of the control unit 20-1 detects the connection of the new subscriber device #k_1 to the network (step S501).

[0234] When the subscriber device management control unit 21 detects that a new subscriber device #k_1 has been connected to the network, it assigns a wavelength to be assigned to the new subscriber device #k_1 from among unused wavelengths. The subscriber device management control unit 21 transmits and receives management control information to the new subscriber device #k_1 using the management control port c. The subscriber device management control unit 21 instructs the new subscriber device #k_1 to set a wavelength and assigns a wavelength to the new subscriber device #k_1. This opens an optical path (step S502).

[0235] The subscriber device management control unit 21 of the control unit 20-1 uses the management control port c to grant permission to each subscriber device #k_1 to transmit an upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, based on the RTT value measured for each subscriber device #k_1, so that the upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, does not collide (step S503).

[0236] Each subscriber device #k_1 transmits an upstream control signal to the subscriber device management and control unit 21 at a timing corresponding to the transmission permission notified from the subscriber device management and control unit 21 (step S504). This completes the operation of the optical communication system 1i shown in the flowchart of FIG.

[0237] As described above, the optical communication system 1i according to the fifth embodiment of the present invention includes a plurality of first optical multiplexing / demultiplexing means 70-1 and a plurality of second optical multiplexing / demultiplexing means 70-2. The subscriber device #k_1 outputs a main signal and an upstream control signal addressed to the subscriber device management and control unit 21 of the control unit 20-1 to the first optical multiplexing / demultiplexing means 70-1 at mutually different wavelengths. The first optical multiplexing / demultiplexing means 70-1 multiplexes signals transmitted from the plurality of subscriber devices #k_1 and outputs the multiplexed signals to the second optical multiplexing / demultiplexing means 70-2. The second optical multiplexing / demultiplexing means 70-2 separates the multiplexed signal input from the first optical multiplexing / demultiplexing means 70-1 into a main signal and an upstream control signal, outputs the main signal to the optical distribution means 10-1, and outputs the upstream control signal to the management and control port c of the subscriber device management and control unit 21 of the control unit 20-1. Furthermore, the subscriber device management and control unit 21 of the control unit 20-2 outputs a downstream control signal addressed to subscriber device #k_2 at a wavelength different from that of the optical carrier carrying the main signal. The second optical multiplexing and demultiplexing unit 70-2 multiplexes the main signal input from the optical distribution unit 10-2 with the downstream control signal input from management and control port c of the subscriber device management and control unit 21, and outputs the multiplexed signal toward the first optical multiplexing and demultiplexing unit 70-1. The first optical multiplexing and demultiplexing unit 70-1 branches the signal input from the second optical multiplexing and demultiplexing unit 70-2 and outputs it toward multiple subscriber devices #k_2.

[0238] Then, the subscriber device #k_1 outputs signal light (burst signal light) of an upstream control signal including an upstream control signal to the subscriber device management and control unit 21 of the control unit 20-1 only during the permitted time period. The subscriber device management and control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21, and grants permission to each subscriber device #k_1 to transmit an upstream control signal based on the RTT value so that the burst signal light transmitted from each subscriber device #k_1 does not collide.

[0239] Furthermore, in the optical communication system 1i in the fifth embodiment, the same management control port c transmits and receives control signals to and from the subscriber device #k_1 before and after the optical path is opened. The management control port c transmits and receives control signals to and from the subscriber device #k_1 before the optical path is opened via the second optical multiplexing / demultiplexing means 70-2 and the optical distribution means 10-1. In addition, the management control port c transmits and receives control signals to and from the subscriber device #k_1 after the optical path is opened via the second optical multiplexing / demultiplexing means 70-2 and the first optical multiplexing / demultiplexing means 70-1.

[0240] With the above-described configuration, the optical communication system 1i according to the fifth embodiment of the present invention transmits and receives control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 using the same management and control port c before and after the optical path is opened. This allows the configuration of the subscriber device management and control unit 21 to be further simplified compared to the optical communication system 1a according to the first embodiment. Furthermore, with the above-described configuration, the optical communication system 1i according to the fifth embodiment allows the management and control port c of the subscriber device management and control unit 21 to be shared among multiple subscriber devices #k_1. This eliminates the need to provide a management and control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1i according to the fifth embodiment of the present invention can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after the optical path is opened, with a simple configuration of the subscriber device management and control unit 21.

[0241] As described above, the optical communication system 1i according to the fifth embodiment includes an optical amplifying means 75 for amplifying the signal light carrying the main signal between the first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2. This allows the optical communication system 1i according to the fifth embodiment to compensate for branching loss that occurs when the signal light carrying the main signal passes through the first optical multiplexing / demultiplexing means 70-1.

[0242] (First modified example of the fifth embodiment) An optical communication system j according to a first modified example of the fifth embodiment of the present invention will be described below. Fig. 23 is a diagram showing the overall configuration of an optical communication system 1j according to a first modified example of the fifth embodiment of the present invention.

[0243] As shown in Figure 23, the optical communication system 1j in the first variant of the fifth embodiment is configured to include a plurality of subscriber devices #k_1 (k = 1, 2, ...), a plurality of subscriber devices #k_2 (k = 1, 2, ...), an optical distribution means 10-1 and an optical distribution means 10-2, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission paths 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing means 70-1, a plurality of second optical multiplexing / demultiplexing means 70-2, a plurality of optical amplification means 75, a plurality of fourth optical multiplexing / demultiplexing means 70-4, and a plurality of fifth optical multiplexing / demultiplexing means 70-5.

[0244] In the following description, among the components provided in the optical communication system 1j in the first variant of the fifth embodiment shown in Figure 23, the components provided in the conventional optical communication system 1 shown in Figure 1 above, the components provided in the conventional optical communication system 1' shown in Figure 2 above, and the components provided in the optical communication systems in each of the above-mentioned embodiments will be given the same symbols and their descriptions may be omitted.

[0245] Note that Figure 23 illustrates an example of signal transmission from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as described below applies to the reverse case of signal transmission from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0246] As shown in FIG. 23, the optical communication system 1j in the first modified example of the fifth embodiment includes a configuration for multiplexing the signal light carrying the main signal and the signal light carrying the upstream control signal after the signal light carrying the main signal has passed through the optical amplifying means 75, and a configuration for separating the signal light carrying the main signal from the signal light carrying the downstream control signal before the signal light carrying the main signal passes through the optical amplifying means 75.

[0247] 23, in an optical communication system 1j according to a first modification of the fifth embodiment, a first optical multiplexing / demultiplexing unit 70-1 wavelength-multiplexes signal light carrying a main signal transmitted from each of a plurality of subscriber devices #k_1. The first optical multiplexing / demultiplexing unit 70-1 outputs the wavelength-multiplexed signal light toward an optical amplification unit 75. The optical amplification unit 75 amplifies the signal light input from the first optical multiplexing / demultiplexing unit 70-1. The optical amplification unit 75 outputs the amplified signal light toward a fourth optical multiplexing / demultiplexing unit 70-4.

[0248] The fifth optical multiplexing / demultiplexing means 70-5 time-multiplexes the signal light carrying the upstream control signal transmitted from each of the subscriber devices #k_1. The fifth optical multiplexing / demultiplexing means 70-5 outputs the time-multiplexed signal light toward the fourth optical multiplexing / demultiplexing means 70-4. The fourth optical multiplexing / demultiplexing means 70-4 multiplexes the signal light amplified by the optical amplification means 75 and the signal light time-multiplexed by the fifth optical multiplexing / demultiplexing means 70-5, and outputs the multiplexed signal light toward the second optical multiplexing / demultiplexing means 70-2.

[0249] 23, in the optical communication system 1j according to the first modification of the fifth embodiment, the fourth optical multiplexing / demultiplexing means 70-4 demultiplexes the signal light input from the second optical multiplexing / demultiplexing means 70-2 into the signal light carrying the main signal and the signal light carrying the downstream control signal. The fourth optical multiplexing / demultiplexing means 70-4 outputs the signal light carrying the main signal toward the optical amplifying means 75, and outputs the signal light carrying the downstream control signal toward the fifth optical multiplexing / demultiplexing means 70-5.

[0250] The optical amplifying means 75 amplifies the signal light carrying the main signal input from the fourth optical multiplexing / demultiplexing means 70-4. The optical amplifying means 75 outputs the amplified signal light carrying the main signal toward the first optical multiplexing / demultiplexing means 70-1. The first optical multiplexing / demultiplexing means 70-1 branches the signal light carrying the main signal input from the optical amplifying means 75 and outputs it toward each of the multiple subscriber devices #k_2. The fifth optical multiplexing / demultiplexing means 70-5 branches the signal light carrying the downstream control signal input from the fourth optical multiplexing / demultiplexing means 70-4 and outputs it toward each of the multiple subscriber devices #k_2.

[0251] As described above, the optical communication system 1j in the first modified example of the fifth embodiment includes an optical amplifying means 75 that amplifies the signal light carrying the main signal, between the first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2. This allows the optical communication system 1j in the first modified example of the fifth embodiment to compensate for branching loss that occurs when the signal light carrying the main signal passes through the first optical multiplexing / demultiplexing means 70-1.

[0252] (Second modified example of the fifth embodiment) An optical communication system 1k according to a second modified example of the fifth embodiment of the present invention will be described below. Fig. 24 is a diagram showing the overall configuration of the optical communication system 1k according to the second modified example of the fifth embodiment of the present invention.

[0253] As shown in Figure 24, the optical communication system 1k in the second variant of the fifth embodiment is configured to include a plurality of subscriber devices #k_1 (k = 1, 2, ...), a plurality of subscriber devices #k_2 (k = 1, 2, ...), an optical distribution means 10-1 and an optical distribution means 10-2, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission paths 50, an optical communication network (NW) 60, a plurality of first optical multiplexing / demultiplexing means 70-1, a plurality of second optical multiplexing / demultiplexing means 70-2, a plurality of third optical multiplexing / demultiplexing means 70-3, a plurality of optical amplification means 75, a plurality of optical amplification control devices 85, and a plurality of fourth optical multiplexing / demultiplexing means 70-4.

[0254] In the following description, among the components of the optical communication system 1k in the fifth embodiment shown in Figure 24, the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication systems in each of the above-mentioned embodiments will be given the same symbols and their descriptions may be omitted.

[0255] Note that Figure 24 illustrates an example of signal transmission from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as described below applies to the reverse case of signal transmission from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0256] As shown in Figure 24, the optical communication system 1k in the second variant of the fifth embodiment has a configuration in which an optical amplification control device 85 that controls the amplification factor of the signal light by the optical amplification means 75 is connected to the lower port of the first optical multiplexing and demultiplexing means 70-1 (i.e., the port on the opposite side to the upper port, which is the port on the optical communication network (NW) 60 side).

[0257] The optical amplification control device 85 transmits, to the first optical multiplexing / demultiplexing means 70-1, signal light carrying an upstream control signal addressed to the subscriber device management and control unit 21, just like the multiple subscriber devices #k_1. The optical amplification control device 85 also receives signal light in which downstream control signals are time-multiplexed and transmitted from the subscriber device management and control unit 21 to the multiple subscriber devices #k_2 and the optical amplification control device 85 (i.e., its own device).

[0258] The downstream control signal transmitted to the optical amplification control device 85 includes a setting instruction for the optical amplifying means 25 to specify the amplification factor of the signal light, etc. The optical amplification control device 85 controls the amplification factor of the signal light by the optical amplification control device 85 in accordance with this setting instruction.

[0259] As described above, the optical communication system 1k in the second modified example of the fifth embodiment includes an optical amplifying means 75 that amplifies the signal light carrying the main signal, between the first optical multiplexing / demultiplexing means 70-1 and the second optical multiplexing / demultiplexing means 70-2. This allows the optical communication system 1k in the second modified example of the fifth embodiment to compensate for branching loss that occurs when the signal light carrying the main signal passes through the first optical multiplexing / demultiplexing means 70-1.

[0260] Sixth Embodiment An optical communication system 1l according to the sixth embodiment of the present invention will be described below. Fig. 25 is a diagram showing the overall configuration of the optical communication system 1l according to the sixth embodiment of the present invention.

[0261] As shown in FIG. 25, the optical communication system 1l in the sixth embodiment includes a plurality of subscriber devices #k_1 (k=1, 2,...), a plurality of subscriber devices #k_2 (k=1, 2,...), a first optical distribution means 10a-1 and a first optical distribution means 10a-2, a second optical distribution means 10b-1 and a second optical distribution means 10b-2, a plurality of route control devices 86, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission paths 50, an optical communication network (NW) 60, and a plurality of second optical multiplexing / demultiplexing means 70-2.

[0262] In the following description, among the components of the optical communication system 1l in the sixth embodiment shown in Figure 25, the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication systems in each of the above-mentioned embodiments will be given the same symbols and their descriptions may be omitted.

[0263] Note that Figure 25 illustrates the case where a signal is transmitted from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as described below applies to the case where a signal is transmitted conversely from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0264] The first optical distribution unit 10a-1 includes a route switching unit 15-1 and a plurality of wavelength multiplexing / demultiplexing units 30-1. The first optical distribution unit 10a-2 includes a route switching unit 15-2 and a plurality of wavelength multiplexing / demultiplexing units 30-2. The control units 20-1 and 20-2 include a subscriber device management control unit 21 and an optical distribution control unit 22, respectively.

[0265] The second light distribution means 10b-1 and the second light distribution means 10b-2 are multicast switches configured with N 1×M (1 to M input / output) optical switches 17 and M N×1 (N to 1 input / output) optical couplers 16 (or M N×1 optical splitters). Note that the second light distribution means 10b-1 and the second light distribution means 10b-2 are not limited to this configuration, and may be configured with, for example, a matrix switch and an optical coupler (or optical splitter).

[0266] As shown in FIG. 25, the configuration of the optical communication system 1l in the sixth embodiment differs from the configuration of the optical communication system 1h in the fourth embodiment described above in that a second optical distribution means 10b-1 and a second optical distribution means 10b-2 are provided instead of the first optical multiplexing / demultiplexing means 70-1.

[0267] The second optical distribution means 10b-1 and the second optical distribution means 10b-2 multiplex the signal light input from the lower side ports (i.e., ports on the opposite side from the upper side ports on the optical communication network (NW) 60 side) in any combination and output the multiplexed signal light from any upper side port toward the second optical multiplexing / demultiplexing means 70-2. Also, the second optical distribution means 10b-1 and the second optical distribution means 10b-2 output the signal light input from the upper side ports (i.e., ports on the optical communication network (NW) 60 side) from one or more arbitrary lower side ports toward each of the plurality of subscriber devices #k_2 and the route control device 86.

[0268] As described above, in the optical communication system 11 of the sixth embodiment, a plurality of subscriber devices #k_1 and the route control device 86 are connected to a downstream port of the second optical distribution unit 10b-1, and a plurality of subscriber devices #k_2 and the route control device 86 are connected to a downstream port of the second optical distribution unit 10b-2. Also, a downstream port of the first optical distribution unit 10a-1 is connected to an upstream port of the second optical distribution unit 10b-1 via the second optical multiplexing / demultiplexing unit 70-2, and a downstream port of the first optical distribution unit 10a-2 is connected to an upstream port of the second optical distribution unit 10b-2 via the second optical multiplexing / demultiplexing unit 70-2.

[0269] In addition, the first optical distribution means 10a-1 and the first optical distribution means 10a-2 in the optical communication system 1l in the sixth embodiment function as functional units equivalent to the optical distribution means 10-1 and the optical distribution means 10-2 in the optical communication system 1h in the fourth embodiment described above.

[0270] The route control device 86, like the plurality of subscriber devices #k_1, outputs, toward the second optical distribution means 10b-1, signal light carrying an upstream control signal transmitted to the subscriber device management and control unit 21. The route control device 86 also receives signal light in which downstream control signals are time-multiplexed and transmitted from the subscriber device management and control unit 21 to the plurality of subscriber devices #k_2 and the route control device 86 (i.e., its own device).

[0271] An instruction to set up a port connection for the second optical distribution unit 10b-2 is included in the downstream control signal transmitted to the route control device 86. The route control device 86 controls the setting up of the port connection of the second optical distribution unit 10b-2 in accordance with the instruction to set up the port connection.

[0272] The second optical distribution means 10b-1 sets up inter-port connections so that the signal light including one or more main signals and the signal light including the upstream control signal, which are input to a lower port from a plurality of subscriber devices #k_1 that transmit and receive signal light carrying an upstream control signal to and from the same management control port c of the subscriber device management control unit 21 and the route control device 86, are output from the same upper port to the second optical multiplexing and demultiplexing means 70-2. As described above, the setting of this inter-port connection is performed under control of a setting instruction from the route control device 86.

[0273] The second optical distribution means 10b-2 also sets up inter-port connections so that the signal light, which is wavelength-multiplexed from the signal light including one or more main signals and the signal light including the downstream control signal input from the second optical multiplexing / demultiplexing means 70-2 to an upstream port, is output from a downstream port to a plurality of subscriber devices #k_2 that transmit and receive signal light carrying the downstream control signal to and from the same management control port c of the subscriber device management control unit 21, and to the route control device 86. As described above, the setting of this inter-port connection is performed under control of a setting instruction from the route control device 86.

[0274] 25, the subscriber devices #1_1, #2_1, #3_1, and the route control device 86 transmit and receive signal light of an upstream control signal to and from the management control port c#1 of the subscriber device management control unit 21. The second optical distribution unit 10b-1 divides the wavelengths λ 1 , λ 2 , and λ 3 , respectively, into the wavelengths λ 1 , λ 2 , and λ 3 , which are downstream ports connected to the subscriber devices #1_1, #2_1, and #3_1. 1_1 , wavelength λ 2_1 , wavelength λ 3_1 Signal light including the main signal and wavelength λ C_UP and the signal light of the upstream control signal of wavelength λ 1 input from port #N, which is the downstream port connected to the route control device 86. C_UP The signal light is wavelength-multiplexed with the signal light of the upstream control signal and output from port #1, which is the upper port.

[0275] The second optical distribution unit 10b-2 also distributes the wavelength λ 1 input from the port #1, which is the upper port. 1_1 , wavelength λ 2_1 , wavelength λ 3_1 Signal light including the main signal and wavelength λ C_DOWN The signal light including the downstream control signal is output from ports #1, #2, #3 and #N which are lower-level ports connected to the subscriber device #1_2, the subscriber device #2_2, the subscriber device #3_2 and the route control device 86, respectively.

[0276] The subscriber device #k_2 selectively receives the signal light including the main signal and the signal light including the downstream control signal transmitted from the subscriber device #k_1, the communication partner, from among the signal light including one or more wavelength-multiplexed main signals and the signal light including the downstream control signal input from the second optical distribution means 10b-2. Also, the route control device 86 selectively receives the signal light including the downstream control signal from among the signal light including one or more wavelength-multiplexed main signals and the signal light including the downstream control signal input from the second optical distribution means 10b-2.

[0277] In order to compensate for the insertion loss of the second optical distribution means 10b-1 and the second optical distribution means 10b-2, similar to the configuration of the optical communication system 1i in the above-mentioned fifth embodiment, the optical communication system 1l in this embodiment may also be configured to further include optical amplification means between the second optical distribution means 10b-1 and the second optical multiplexing / demultiplexing means 70-2 and between the second optical distribution means 10b-2 and the second optical multiplexing / demultiplexing means 70-2.

[0278] [Operation of optical communication system] An example of the operation of the optical communication system 1l will be described below. Fig. 26 is a flowchart showing the operation of the optical communication system 1l in the sixth embodiment of the present invention. The operation of the optical communication system 1l shown in the flowchart of Fig. 26 starts when a new subscriber device #k_1 is connected to the network.

[0279] When a new subscriber device #k_1 is connected to the network, the subscriber device management control unit 21 of the control unit 20-1 detects the connection of the new subscriber device #k_1 to the network (step S601).

[0280] When the subscriber device management control unit 21 detects that a new subscriber device #k_1 has been connected to the network, it assigns a wavelength to be allocated to the new subscriber device #k_1 from among unused wavelengths. The subscriber device management control unit 21 transmits and receives management control information to the new subscriber device #k_1 using the management control port c. The subscriber device management control unit 21 instructs the new subscriber device #k_1 to set a wavelength and allocates a wavelength to the new subscriber device #k_1. This opens an optical path (step S602).

[0281] The subscriber device management control unit 21 of the control unit 20-1 uses the management control port c to grant permission to each subscriber device #k_1 to transmit an upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, based on the RTT value measured for each subscriber device #k_1, so that the upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, does not collide (step S603).

[0282] Each subscriber device #k_1 transmits an upstream control signal to the subscriber device management and control unit 21 at a timing corresponding to the transmission permission notified from the subscriber device management and control unit 21 (step S604). This completes the operation of the optical communication system 11 shown in the flowchart of FIG.

[0283] As described above, the optical communication system 1l according to the sixth embodiment of the present invention includes a plurality of second optical distribution units 10b-1 and 10b-2 and a plurality of second optical multiplexing / demultiplexing units 70-2. The subscriber device #k_1 outputs a main signal and an upstream control signal addressed to the subscriber device management and control unit 21 of the control unit 20-1 to the second optical distribution unit 10b-1 at mutually different wavelengths. The second optical distribution unit 10b-1 multiplexes signals transmitted from the plurality of subscriber devices #k_1 and outputs the multiplexed signals to the second optical multiplexing / demultiplexing unit 70-2. The second optical multiplexing / demultiplexing unit 70-2 separates the multiplexed signal output from the second optical distribution unit 10b-1 into a main signal and an upstream control signal, outputs the main signal to the optical distribution unit 10-1, and outputs the upstream control signal to the management and control port c of the subscriber device management and control unit 21 of the control unit 20-1. Furthermore, the subscriber device management and control unit 21 of the control unit 20-2 outputs a downstream control signal addressed to subscriber device #k_2 at a wavelength different from that of the optical carrier carrying the main signal. The second optical multiplexing and demultiplexing unit 70-2 multiplexes the main signal input from the optical distribution unit 10-2 with the downstream control signal input from the management and control port c of the subscriber device management and control unit 21, and outputs the multiplexed signal toward the second optical distribution unit 10b-2. The second optical distribution unit 10b-2 branches the signal output from the second optical multiplexing and demultiplexing unit 70-2 and outputs it toward multiple subscriber devices #k_2.

[0284] Then, the subscriber device #k_1 outputs signal light (burst signal light) of an upstream control signal including an upstream control signal to the subscriber device management and control unit 21 of the control unit 20-1 only during the permitted time period. The subscriber device management and control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21, and grants permission to each subscriber device #k_1 to transmit an upstream control signal based on the RTT value so that the burst signal light transmitted from each subscriber device #k_1 does not collide.

[0285] Furthermore, in the optical communication system 11 in the sixth embodiment, the same management control port c transmits and receives control signals to and from the subscriber device #k_1 before and after the optical path is opened. The management control port c transmits and receives control signals to and from the subscriber device #k_1 before the optical path is opened via the second optical multiplexing / demultiplexing means 70-2, the second optical distribution means 10b-1, or the second optical distribution means 10b-2. Moreover, the management control port c transmits and receives control signals to and from the subscriber device #k_1 after the optical path is opened via the second optical multiplexing / demultiplexing means 70-2, the second optical distribution means 10b-1, or the second optical distribution means 10b-2.

[0286] With the above-described configuration, the optical communication system 1l according to the sixth embodiment of the present invention transmits and receives control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 using the same management and control port c before and after the optical path is opened. This allows the configuration of the subscriber device management and control unit 21 to be further simplified compared to the optical communication system 1a according to the first embodiment. Furthermore, with the above-described configuration, the optical communication system 1l according to the sixth embodiment allows the management and control port c of the subscriber device management and control unit 21 to be shared among multiple subscriber devices #k_1. As a result, the optical communication system 1l does not need to provide a management and control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1l according to the sixth embodiment of the present invention can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after the optical path is opened, with a simple configuration of the subscriber device management and control unit 21.

[0287] Furthermore, the optical communication system 1l in the sixth embodiment can also include an optical amplifying means 75 that amplifies the signal light carrying the main signal between the second optical distribution means 10b-1, 10b-2 and the second optical multiplexing / demultiplexing means 70-2. This allows the optical communication system 1l in the sixth embodiment to compensate for branching loss that occurs when the signal light carrying the main signal passes through the first optical multiplexing / demultiplexing means 70-1.

[0288] Seventh Embodiment An optical communication system 1m according to the seventh embodiment of the present invention will now be described. FIG. 27 is a diagram showing the overall configuration of an optical communication system 1m according to the seventh embodiment of the present invention.

[0289] As shown in FIG. 27, the optical communication system 1m in the seventh embodiment is configured to include a plurality of subscriber devices #k_1 (k=1, 2,...), a plurality of subscriber devices #k_2 (k=1, 2,...), a wavelength multiplexing / demultiplexing means 30-4 and a wavelength multiplexing / demultiplexing means 30-5, a plurality of route control devices 86, a plurality of second optical multiplexing / demultiplexing means 70-2, an optical distribution means 10-1 and an optical distribution means 10-2, a control unit 20-1 and a control unit 20-2, a plurality of optical fiber transmission paths 50, and an optical communication network (NW) 60.

[0290] In the following description, among the components of the optical communication system 1m in the seventh embodiment shown in Figure 27, the components of the conventional optical communication system 1 shown in Figure 1 above, the components of the conventional optical communication system 1' shown in Figure 2 above, and the components of the optical communication systems in each of the above-mentioned embodiments will be given the same symbols and their descriptions may be omitted.

[0291] Note that Figure 27 illustrates the case where a signal is transmitted from subscriber device #k_1 (k = 1, 2, ...) to subscriber device #k_2 (k = 1, 2, ...), but the same configuration as described below applies to the case where a signal is transmitted conversely from subscriber device #k_2 (k = 1, 2, ...) to subscriber device #k_1 (k = 1, 2, ...).

[0292] The optical distribution means 10-1 includes a route switching means 15-1 and a plurality of wavelength multiplexing / demultiplexing means 30-1. The optical distribution means 10-2 includes a route switching means 15-2 and a plurality of wavelength multiplexing / demultiplexing means 30-2. The control units 20-1 and 20-2 include a subscriber device management control unit 21 and an optical distribution control unit 22, respectively.

[0293] As shown in Figure 27, the configuration of the optical communication system 1m in the seventh embodiment differs from the configuration of the optical communication system 1h in the aforementioned fourth embodiment in that a wavelength multiplexing / demultiplexing means 30-4 and a wavelength multiplexing / demultiplexing means 30-5 are provided instead of the first optical multiplexing / demultiplexing means 70-1.

[0294] The wavelength multiplexing / demultiplexing means 30-4 and the wavelength multiplexing / demultiplexing means 30-5 can set the wavelengths that are transmitted between the ports in wavelength units.

[0295] 27, the downstream port of the wavelength multiplexing / demultiplexing means 30-4 is connected to a plurality of subscriber devices #k_1 and the route control device 86, and the downstream port of the wavelength multiplexing / demultiplexing means 30-5 is connected to a plurality of subscriber devices #k_2 and the route control device 86. Also, as shown in Fig. 27, the upstream port of the wavelength multiplexing / demultiplexing means 30-4 is connected to a downstream port of the optical distribution means 10-1 via the second optical multiplexing / demultiplexing means 70-2, and the upstream port of the wavelength multiplexing / demultiplexing means 30-5 is connected to a downstream port of the optical distribution means 10-2 via the second optical multiplexing / demultiplexing means 70-2.

[0296] The wavelength multiplexing / demultiplexing means 30-4 and the wavelength multiplexing / demultiplexing means 30-5 are configured using, for example, a wavelength selective switch (WSS) or the like.

[0297] In the configuration of the optical communication system 1m illustrated in FIG. 27, the wavelength multiplexing / demultiplexing means 30-4 and the wavelength multiplexing / demultiplexing means 30-5 have multiple upstream ports, but the number of upstream ports provided in the wavelength multiplexing / demultiplexing means 30-4 and the wavelength multiplexing / demultiplexing means 30-5 may be one.

[0298] The route control device 86 transmits, to the wavelength multiplexing / demultiplexing means 30-4, signal light carrying an upstream control signal addressed to the customer device management and control unit 21, just like the multiple customer devices #k_1. The route control device 86 also receives, from the wavelength multiplexing / demultiplexing means 30-4, signal light in which downstream control signals are time-multiplexed and transmitted from the customer device management and control unit 21 to the multiple customer devices #k_2 and the route control device 86 (i.e., its own device).

[0299] The downstream control signal transmitted to the route control device 86 includes an instruction to set up port connections on a wavelength-by-wavelength basis for the wavelength multiplexing / demultiplexing means 30-5. The route control device 86 controls the setting of port connections on a wavelength-by-wavelength basis for the wavelength multiplexing / demultiplexing means 30-5 in accordance with this instruction to set up port connections on a wavelength-by-wavelength basis.

[0300] The wavelength multiplexing / demultiplexing means 30-4 sets up inter-port connections so that signal lights including one or more main signals and signal lights including upstream control signals, which are input to its lower-order port from a plurality of subscriber devices #k_1 that transmit and receive signal lights carrying upstream control signals to and from the same management control port c of the subscriber device management control unit 21 and the route control device 86, are output from the same upper-order port to the second optical multiplexing / demultiplexing means 70-2. As described above, the setting of this inter-port connection is performed under control of a setting instruction from the route control device 86.

[0301] At this time, the route control device 86 dynamically switches the port connection settings of the wavelength multiplexing / demultiplexing means 30-4 so that, with respect to the wavelength of the signal light carrying the upstream control signal, the signal light of the upstream control signal, which is a burst signal transmitted from each of the subscriber devices #k_1 and the route control device 86 during the period permitted by the subscriber device management control unit 21, is time-multiplexed and output from the upstream port connected to the second optical multiplexing / demultiplexing means 70-2.

[0302] The wavelength multiplexing / demultiplexing means 30-5 also sets the inter-port connections of the wavelength multiplexing / demultiplexing means 30-5 in wavelength units so that the signal light, which is input from the second optical multiplexing / demultiplexing means 70-2 to an upper port and is wavelength-multiplexed with signal light including one or more main signals and signal light including downstream control signals, is distributed from a lower port and output toward a plurality of subscriber devices #k_2 that transmit and receive signal light carrying downstream control signals to and from the same management control port c of the subscriber device management control unit 21, and toward the route control device 86. As described above, the setting of the inter-port connections in wavelength units is performed under control of a setting instruction from the route control device 86.

[0303] At this time, the route control device 86 sets the inter-port connections of the wavelength multiplexing / demultiplexing means 30-5 so that, with respect to the wavelength of the signal light carrying the main signal, the signal light including the wavelength-multiplexed main signal input from the second optical multiplexing / demultiplexing means 70-2 to the upper port is separated by wavelength and output from the lower port toward each of the multiple subscriber devices #k_2.

[0304] Also, at this time, the route control device 86 dynamically switches the settings of the port-to-port connections of the wavelength multiplexing / demultiplexing means 30-5 so that, with respect to the wavelength of the signal light carrying the downstream control signal, the signal light carrying the downstream control signal is distributed and output according to the destination of the downstream control signal from the lower-side ports connected to the destination subscriber device #k_1 or the route control device 86, respectively.

[0305] 27, the subscriber devices #1_1, #2_1, #3_1 and the route control device 86 transmit and receive signal light of an upstream control signal to and from the management control port c#1 of the subscriber device management control unit 21. The wavelength multiplexing and demultiplexing means 30-4 divides the wavelengths λ 1 , λ 2 , λ 3 , λ 4 , λ 5 , λ 6 , λ 7 , λ 8 , λ 9 , λ 10 , λ 11 , λ 12 , λ 13 , λ 14 , λ 15 , λ 16 , λ 17 , λ 18 , λ 19 , λ 20 , λ 21 , λ 22 , λ 23 , λ 24 , λ 25 , λ 26 , λ 27 , λ 28 , λ 29 , λ 30 , λ 31 , λ 32 , λ 33 , λ 34 , λ 35 , λ 36 , λ 37 , λ 38 , λ 39 , λ 40 , λ 41 , λ 42 , λ 43 , λ 44 , λ 45 , λ 46 , λ 47 , λ 48 , λ 49 , λ 50 , λ 51 , λ 52 , λ 53 , λ 54 , λ 55 , λ 56 , λ 57 , λ 58 , λ 59 , λ 59 , λ 59 , λ 59 , λ 59 1_1 , wavelength λ 2_1 , wavelength λ 3_1 Signal light including the main signal and wavelength λ C_UP and the signal light of the upstream control signal of wavelength λ 1 input from port #N, which is the downstream port connected to the route control device 86. C_UP The signal light is wavelength-multiplexed with the signal light of the upstream control signal and output from port #1, which is the upper port.

[0306] The wavelength multiplexer / demultiplexer 30-5 also receives the wavelength λ 1 from the port #1, which is the upper port. 1_1 , wavelength λ 2_1 , wavelength λ 3_1The wavelength multiplexing / demultiplexing means 30-5 separates the signal light including the main signal of the wavelength λ 1 input from the port #1 which is the upper port and outputs the separated signal light from the port #1, port #2, and port #3 which are the lower side ports connected to the subscriber device #1_2, the subscriber device #2_2, and the subscriber device #3_2, respectively. C_DOWN The signal light including the downstream control signal is output in this order from the lower ports, port #1, port #2, port #3 and port #N, which are connected to the subscriber device #1_2, subscriber device #2_2, subscriber device #3_2 and route control device 86, respectively.

[0307] In order to compensate for the insertion loss of the wavelength multiplexing / demultiplexing means 30-4 and the wavelength multiplexing / demultiplexing means 30-5, similar to the configuration of the optical communication system 1i in the above-mentioned fifth embodiment, the optical communication system 1m in this embodiment may also be configured to further include optical amplification means between the wavelength multiplexing / demultiplexing means 30-4 and the second optical multiplexing / demultiplexing means 70-2 and between the wavelength multiplexing / demultiplexing means 30-5 and the second optical multiplexing / demultiplexing means 70-2.

[0308] [Operation of optical communication system] An example of the operation of the optical communication system 1m will be described below. Fig. 28 is a flowchart showing the operation of the optical communication system 1m in the seventh embodiment of the present invention. The operation of the optical communication system 1m shown in the flowchart of Fig. 28 starts when a new subscriber device #k_1 is connected to the network.

[0309] When a new subscriber device #k_1 is connected to the network, the subscriber device management control unit 21 of the control unit 20-1 detects the connection of the new subscriber device #k_1 to the network (step S701).

[0310] When the subscriber device management control unit 21 detects that a new subscriber device #k_1 has been connected to the network, it assigns a wavelength to be assigned to the new subscriber device #k_1 from among unused wavelengths. The subscriber device management control unit 21 transmits and receives management control information to the new subscriber device #k_1 using the management control port c. The subscriber device management control unit 21 instructs the new subscriber device #k_1 to set a wavelength and assigns a wavelength to the new subscriber device #k_1. This opens an optical path (step S702).

[0311] The subscriber device management control unit 21 of the control unit 20-1 uses the management control port c to grant permission to each subscriber device #k_1 to transmit an upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, based on the RTT value measured for each subscriber device #k_1, so that the upstream control signal, which is a burst signal light transmitted from each subscriber device #k_1, does not collide (step S703).

[0312] Each subscriber device #k_1 transmits an upstream control signal to the subscriber device management and control unit 21 at a timing corresponding to the transmission permission notified from the subscriber device management and control unit 21 (step S704). This completes the operation of the optical communication system 1m shown in the flowchart of FIG.

[0313] As described above, the optical communication system 1m according to the seventh embodiment of the present invention includes a wavelength multiplexing / demultiplexing means 30-4, a wavelength multiplexing / demultiplexing means 30-5, and a plurality of second optical multiplexing / demultiplexing means 70-2. The subscriber device #k_1 outputs a main signal and an upstream control signal addressed to the subscriber device management and control unit 21 of the control unit 20-1 to the wavelength multiplexing / demultiplexing means 30-4 at mutually different wavelengths. The wavelength multiplexing / demultiplexing means 30-4 multiplexes signals transmitted from the plurality of subscriber devices #k_1 and outputs the multiplexed signals to the second optical multiplexing / demultiplexing means 70-2. The second optical multiplexing / demultiplexing means 70-2 separates the multiplexed signal output from the wavelength multiplexing / demultiplexing means 30-4 into a main signal and an upstream control signal, outputs the main signal to the optical distribution means 10-1, and outputs the upstream control signal to the management and control port c of the subscriber device management and control unit 21 of the control unit 20-1. Furthermore, the subscriber device management and control unit 21 of the control unit 20-2 outputs a downstream control signal addressed to subscriber device #k_2 at a wavelength different from that of the optical carrier carrying the main signal. The second optical multiplexing and demultiplexing unit 70-2 multiplexes the main signal input from the optical distribution unit 10-2 with the downstream control signal input from management and control port c of the subscriber device management and control unit 21, and outputs the multiplexed signal toward the wavelength multiplexing and demultiplexing unit 30-5. The wavelength multiplexing and demultiplexing unit 30-5 distributes the signal output from the second optical multiplexing and demultiplexing unit 70-2 toward multiple subscriber devices #k_2 and outputs it.

[0314] As explained above, the subscriber device #k_1 outputs signal light (burst signal light) of an upstream control signal including an upstream control signal to the subscriber device management and control unit 21 of the control unit 20-1 only during the permitted time period. The subscriber device management and control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management and control unit 21, and grants permission to each subscriber device #k_1 to transmit an upstream control signal based on the value of the RTT so that the burst signal light transmitted from each subscriber device #k_1 does not collide.

[0315] Furthermore, in the optical communication system 1m in the seventh embodiment, the same management control port c transmits and receives control signals to and from the subscriber device #k_1 before and after the optical path is opened. The management control port c transmits and receives control signals to and from the subscriber device #k_1 before the optical path is opened via the second optical multiplexing / demultiplexing means 70-2, the wavelength multiplexing / demultiplexing means 30-4, or the wavelength multiplexing / demultiplexing means 30-5. Also, the management control port c transmits and receives control signals to and from the subscriber device #k_1 after the optical path is opened via the second optical multiplexing / demultiplexing means 70-2, the wavelength multiplexing / demultiplexing means 30-4, or the wavelength multiplexing / demultiplexing means 30-5.

[0316] With the above-described configuration, the optical communication system 1m according to the seventh embodiment of the present invention transmits and receives control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 using the same management and control port c before and after the optical path is opened. This allows the configuration of the subscriber device management and control unit 21 to be further simplified compared to the optical communication system 1a according to the first embodiment. Furthermore, with the above-described configuration, the optical communication system 1m according to the seventh embodiment allows the management and control port c of the subscriber device management and control unit 21 to be shared among multiple subscriber devices #k_1. This eliminates the need to provide a management and control port c of the subscriber device management and control unit 21 for each subscriber device #k_1. Therefore, the optical communication system 1m according to the seventh embodiment of the present invention can transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after the optical path is opened, with a simple configuration of the subscriber device management and control unit 21.

[0317] As described above, in the optical communication systems in the above-mentioned embodiments and modified examples of each embodiment, the subscriber device management control unit 21 of the control unit 20-1 recognizes, for each subscriber device #k_1, the round trip propagation time (RTT) of the control signal between the subscriber device #k_1 and its own subscriber device management control unit 21, and grants permission to each subscriber device #k_1 to transmit the upstream control signal based on the value of the RTT so that the upstream control signals, which are burst signal light transmitted from each subscriber device #k_1, do not collide.

[0318] By having such a configuration, the optical communication system in each of the above-mentioned embodiments and modified examples of each embodiment makes it possible to share the management control port of the subscriber device management control unit 21 (management control port c in optical communication systems 1a to 1b and management control port c in optical communication systems 1c to 1m) among multiple subscriber devices #k_1, and makes it possible to send and receive control signals between the subscriber device management control unit 21 and subscriber device #k_1 after the optical path has been opened, with a simple configuration of the subscriber device management control unit 21 while preventing the configuration of the subscriber device management control unit from becoming large-scale.

[0319] Furthermore, according to the optical communication systems of the fourth to seventh embodiments described above, the signal light carrying the upstream control signal is transferred to the management control port of the subscriber device management and control unit 21, and the signal light carrying the downstream control signal is multiplexed with the signal light carrying the main signal, so there is no need to provide optical components equal to the number of optical paths.

[0320] Furthermore, when multiple subscriber devices are installed within the same base station or neighboring base stations, the first optical multiplexing / demultiplexing means 70-1 in the fourth and fifth embodiments, the second optical distribution means 10b-1 and the second optical distribution means 10b-2 in the sixth embodiment, and the wavelength multiplexing / demultiplexing means 30-4 and the wavelength multiplexing / demultiplexing means 30-5 in the seventh embodiment are provided within or near the base station where the subscriber devices are installed, and these functional units are configured to converge. Therefore, the optical fiber transmission path between the convergence point and the optical distribution means is shared by multiple subscriber devices #k_1 and #k_2.

[0321] This makes it possible to transmit and receive control signals between the subscriber device management and control unit 21 and the subscriber device #k_1 after the optical path is once opened, without providing optical fiber transmission paths corresponding to the number of subscriber devices. This also makes it possible to increase the number of subscriber devices #k_1 and #k_2 with which the subscriber device management and control unit 21 can transmit and receive control signals for a given number of ports of the optical distribution unit 10-1 and the optical distribution unit 10-2.

[0322] According to the above-described embodiment, the optical communication system includes a communication control unit and an optical multiplexing / demultiplexing unit. For example, the optical communication system is the optical communication systems 1a to 1g in the embodiment, the communication control unit is the subscriber device management and control unit 21 in the embodiment, and the optical multiplexing / demultiplexing unit is the first optical multiplexing / demultiplexing unit 70-1 and the second optical multiplexing / demultiplexing unit 70-2 in the embodiment. The communication control unit controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices. For example, the plurality of first communication devices are a plurality of subscriber devices #k_1 (k=1, 2, . . .) in the embodiment, and the plurality of second communication devices are a plurality of subscriber devices #k_2 (k=1, 2, . . .) in the embodiment. The optical multiplexing / demultiplexing unit multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after the optical path is opened. For example, the signal light of the control signal is signal light including an upstream control signal and signal light including a downstream control signal in the embodiment.

[0323] The communication control unit controls the reception timings of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by permitting each of the plurality of first communication devices to transmit an upstream control signal based on the round trip time (RTT) of each of the signal lights traveling back and forth between the communication control unit and each of the plurality of first communication devices. For example, the signal lights traveling back and forth in the embodiment are signal lights including downstream control signals transmitted from the customer device management and control unit 21 of the control unit 20-1 to the customer device #k_1, and signal lights including upstream control signals transmitted from the customer device #k_1 to the customer device management and control unit 21 of the control unit 20-1.

[0324] In the above optical communication system, the communication control unit controls the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit so that the upstream control signals are time-division multiplexed and transmitted.

[0325] In the above optical communication system, the optical multiplexing / demultiplexing unit may further multiplex / demultiplex the signal light of the control signal transmitted between each of the plurality of first communication devices and the communication control unit before the optical path is opened. For example, the optical communication system is optical communication systems 1d to 1g in the embodiments. That is, as in the configurations of optical communication systems 1d to 1g shown in FIGS. 12 to 16 and 18, respectively, the optical multiplexing / demultiplexing unit may be configured to multiplex / demultiplex not only the signal light of the control signal transmitted and received after the optical path is opened, but also the signal light of the control signal transmitted and received before the optical path is opened. In this case, the communication control unit may control the upstream control signal transmitted from each of the plurality of first communication devices to the communication control unit and the main signal transmitted from each of the first communication devices to one of the second communication devices so that they are time-division multiplexed and transmitted.

[0326] In the above optical communication system, the communication control unit may transmit and receive control signals using the same communication port before and after the optical path is opened. For example, the optical communication system is optical communication systems 1c to 1g in the embodiment, and the same communication port is management control port c of the subscriber device management control unit 21 in the embodiment.

[0327] The optical communication system may further include a dispersion compensator that compensates for chromatic dispersion occurring in a transmission path of the signal light between the first communication device and the second communication device. For example, the optical communication system may be any of the optical communication systems 1f to 1g in the embodiments, the signal light may be the signal light including the main signal in the embodiments, and the dispersion compensator may be the plurality of dispersion compensators 80-1 and 80-2 in the embodiments. In this case, the communication control unit may measure a first distance between the communication control unit and the first communication device based on a round trip time (RTT) and the speed of light, calculate a second distance between the first communication device and the second communication device based on the first distance, and calculate a required amount of chromatic dispersion compensation based on the second distance and the wavelength of the signal light transmitted from the first communication device. In this case, the dispersion compensator may compensate for the chromatic dispersion in the amount of chromatic dispersion compensation calculated by the communication control unit. For example, the round-trip propagation time is the RTT of the control signal between the subscriber device management control unit 21 of the control unit 20-1 in the embodiment and the subscriber device #k_1 newly connected to the network, the first distance is the distance between the subscriber device management control unit 21 of the control unit 20-1 in the embodiment and the subscriber device #k_1 newly connected to the network, the second distance is the distance between the subscriber device #k_1 newly connected to the network in the embodiment and the subscriber device #k_2 with which the subscriber device #k_1 communicates, and the wavelength of the signal light transmitted from the first communication device is the wavelength of the signal light including the main signal in the embodiment.

[0328] In the above optical communication system, the optical multiplexing / demultiplexing unit may multiplex signal light, which is input from each of the first communication devices and is obtained by multiplexing the signal light of the main signal and the signal light of the upstream control signal, and demultiplex the signal light, which is obtained by multiplexing the signal light of the main signal and the signal light of the downstream control signal, and output the demultiplexed signal light to each of the second communication devices. In this case, for example, the optical multiplexing / demultiplexing unit is the first optical multiplexing / demultiplexing means 70-1 in the embodiment.

[0329] In the above-described optical communication system, the optical multiplexing / demultiplexing unit may multiplex the signal light of the main signal output from each of the plurality of first communication devices, multiplexed, and then amplified, with the signal light of the upstream control signal output from each of the plurality of first communication devices, demultiplex the signal light obtained by multiplexing the signal light of the main signal and the signal light of the downstream control signal, and output the signal light of the main signal to the amplifier and output the signal light of the downstream control signal to the second communication device.

[0330] The optical communication system may further include a route control unit. For example, the route control unit is the route control device 86 in the embodiment. The route control unit controls switching of signal paths by the optical multiplexing / demultiplexing unit. For example, the optical multiplexing / demultiplexing unit is the second optical distribution unit 10b-1 and the second optical distribution unit 10b-2 in the embodiment. The route control unit controls the optical multiplexing / demultiplexing unit so that signal light input from the lower-order ports of the optical multiplexing / demultiplexing unit is multiplexed in any combination and output from any upper-order port, and so that signal light input from the upper-order port of the optical multiplexing / demultiplexing unit is output from one or more arbitrary lower-order ports.

[0331] The optical communication system may further include a route control unit. For example, the route control unit is the route control device 86 in the embodiment. The route control unit controls the setting of signal paths by the optical multiplexing / demultiplexing unit. For example, the optical multiplexing / demultiplexing unit is the wavelength multiplexing / demultiplexing means 30-4 and wavelength multiplexing / demultiplexing means 30-5 in the embodiment. The optical multiplexing / demultiplexing unit is configured to be able to set the wavelength that passes between the upper port and the lower port in wavelength units. The route control unit controls the connection between the ports of the optical multiplexing / demultiplexing unit in wavelength units, thereby controlling the setting of signal paths for the signal light of the upstream control signal and the signal light of the downstream control signal.

[0332] Furthermore, according to the above-described embodiment, the communication control device controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices. For example, the communication control device is a device including control units 20-1 and 20-2 in the embodiment, the plurality of first communication devices are the plurality of subscriber devices #k_1 (k=1, 2, . . . ) in the embodiment, and the plurality of second communication devices are the plurality of subscriber devices #k_2 (k=1, 2, . . . ) in the embodiment.

[0333] The communication control device includes a control unit. For example, the control unit is the customer equipment management and control unit 21 in the embodiment. The control unit controls the reception timing of the upstream control signal transmitted from each of the first communication devices to the communication control device so that the reception timing of the upstream control signal transmitted from each of the first communication devices to the communication control device is different from each other by permitting each of the first communication devices to transmit an upstream control signal based on the round-trip propagation time of each signal light traveling between the communication control device and each of the first communication devices. For example, the round-trip signal light is the signal light including the downstream control signal transmitted from the customer equipment management and control unit 21 of the control unit 20-1 to the customer equipment #k_1 in the embodiment, and the signal light including the upstream control signal transmitted from the customer equipment #k_1 to the customer equipment management and control unit 21 of the control unit 20-1.

[0334] A part of the configuration of the optical communication systems 1a to 1g in the above-described embodiments 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 may be loaded into a computer system and executed. Note that the term "computer system" herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" 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 a computer system. Furthermore, the term "computer-readable recording medium" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may be for implementing a part of the above-described functions, or may be capable of implementing the above-described functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0335] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Explanation of symbols]

[0336] 1, 1', 1a to 1g... optical communication system, 10-1, 10-2... optical distribution means, 20-1, 20-2... control unit, 21... subscriber device management control unit, 22... optical distribution control unit, 30-1, 30-2... wavelength multiplexing / demultiplexing means, 40... wavelength filter, 50... optical fiber transmission line, 60... optical communication network (NW), 70... optical multiplexing / demultiplexing means, 80-1, 80-2... dispersion compensation means, 91-1, 91-2... wavelength filter, 92-1, 92-2... photodiode (PD), 93... optical demultiplexing means

Claims

1. a communication control unit that controls the opening of an optical path between any one of the plurality of first communication devices and any one of the plurality of second communication devices; an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after an optical path is opened; Equipped with The communication control unit controls the reception timings of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by permitting each of the plurality of first communication devices to transmit an upstream control signal based on the round-trip propagation time of each signal light traveling between the communication control unit and each of the plurality of first communication devices. Optical communication system.

2. The optical multiplexing / demultiplexing unit a plurality of first optical multiplexing / demultiplexing units provided in a plurality of optical transmission lines respectively connected to the plurality of first communication devices; a second optical multiplexing / demultiplexing unit connected to the plurality of first optical multiplexing / demultiplexing units; Equipped with the first optical multiplexing / demultiplexing unit outputs the upstream control signal transmitted from the first communication device to the second optical multiplexing / demultiplexing unit; The second optical multiplexing / demultiplexing unit multiplexes the upstream control signals output from the plurality of first optical multiplexing / demultiplexing units and outputs the multiplexed signal to the communication control unit.

2. The optical communication system according to claim 1.

3. The communication control unit controls the uplink control signal transmitted from each of the plurality of first communication devices to the communication control unit so that the uplink control signal is transmitted in a time division multiplexed manner.

2. The optical communication system according to claim 1.

4. The communication control unit controls the upstream control signal transmitted from each of the plurality of first communication devices to the communication control unit and the main signal transmitted from each of the first communication devices to any one of the second communication devices so that they are time-division multiplexed and transmitted.

2. The optical communication system according to claim 1.

5. The communication control unit transmits and receives the control signal using the same communication port before and after the optical path is opened.

2. The optical communication system according to claim 1.

6. a dispersion compensator that compensates for chromatic dispersion occurring in a transmission path of signal light between the first communication device and the second communication device; Furthermore, the communication control unit measures a first distance between the communication control unit and the first communication device based on the round-trip propagation time and the speed of light, calculates a second distance between the first communication device and the second communication device based on the first distance, and calculates a required amount of chromatic dispersion compensation based on the second distance and a wavelength of the signal light transmitted from the first communication device; The dispersion compensator compensates for the chromatic dispersion of the chromatic dispersion compensation amount calculated by the communication controller.

6. An optical communication system according to any one of claims 1 to 5.

7. A communication control unit that controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices; an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after an optical path is opened; Equipped with the communication control unit controls reception timings of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by permitting each of the plurality of first communication devices to transmit an upstream control signal based on a round-trip propagation time of each signal light traveling back and forth between the communication control unit and each of the plurality of first communication devices; The optical multiplexing / demultiplexing unit The optical signal multiplexer combines the optical signal of the main signal and the optical signal of the upstream control signal, which are input from the plurality of first communication devices, and demultiplexes the optical signal multiplexed with the optical signal of the main signal and the optical signal of the downstream control signal, and outputs the demultiplexed optical signal to the plurality of second communication devices. Optical communication system.

8. A communication control unit that controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices; an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after an optical path is opened; Equipped with the communication control unit controls reception timings of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by permitting each of the plurality of first communication devices to transmit an upstream control signal based on a round-trip propagation time of each signal light traveling back and forth between the communication control unit and each of the plurality of first communication devices; The optical multiplexing / demultiplexing unit a first communication device that receives the first signal light from the first communication device and multiplexes the amplified main signal light, and a second communication device that receives the first signal light from the first communication device and multiplexes the upstream control signal light; a second communication device that receives the first signal light from the first communication device and multiplexes the upstream control signal light; a second communication device that receives the second signal light from the first communication device and multiplexes the upstream control signal light; a second communication device that receives the second signal light from the first communication device and multiplexes the downstream control signal light; a second communication device that receives the second signal light from the first communication device and multiplexes the upstream control signal light; a first communication device that receives the first ... second communication Optical communication system.

9. A communication control unit that controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices; an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after an optical path is opened; a path control unit that controls switching of signal paths by the optical multiplexing / demultiplexing unit; Equipped with the communication control unit controls reception timings of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by permitting each of the plurality of first communication devices to transmit an upstream control signal based on a round-trip propagation time of each signal light traveling back and forth between the communication control unit and each of the plurality of first communication devices; The route control unit controls the optical multiplexing / demultiplexing unit so that signal light input from a lower port of the optical multiplexing / demultiplexing unit is multiplexed in any combination and output from any upper port, and so that signal light input from the upper port of the optical multiplexing / demultiplexing unit is output from one or more of the lower port. Optical communication system.

10. A communication control unit that controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices; an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after an optical path is opened; a path control unit that controls setting of a signal path by the optical multiplexing / demultiplexing unit; Equipped with the communication control unit controls reception timings of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control unit to be different from each other by permitting each of the plurality of first communication devices to transmit an upstream control signal based on a round-trip propagation time of each signal light traveling back and forth between the communication control unit and each of the plurality of first communication devices; the optical multiplexing / demultiplexing unit is configured to be able to set a wavelength to be transmitted between an upper port and a lower port in wavelength units; The route control unit controls the setting of the signal paths of the signal light of the upstream control signal and the signal light of the downstream control signal by controlling the connection between ports of the optical multiplexing / demultiplexing unit in units of wavelengths. Optical communication system.

11. A communication control device that controls the opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices, the communication control device controls the reception timings of the upstream control signals transmitted from each of the plurality of first communication devices to the communication control device to be different from each other by permitting each of the plurality of first communication devices to transmit an upstream control signal based on the round-trip propagation time of each signal light traveling between the communication control device and each of the plurality of first communication devices via an optical multiplexing / demultiplexing unit; Equipped with The optical multiplexing / demultiplexing unit a plurality of first optical multiplexing / demultiplexing units provided in a plurality of optical transmission lines respectively connected to the plurality of first communication devices; a second optical multiplexing / demultiplexing unit connected to the plurality of first optical multiplexing / demultiplexing units; Equipped with the first optical multiplexing / demultiplexing unit outputs the upstream control signal transmitted from the first communication device to the second optical multiplexing / demultiplexing unit; The second optical multiplexing / demultiplexing unit multiplexes the upstream control signals output from the plurality of first optical multiplexing / demultiplexing units and outputs the multiplexed signals to the communication control device. Communications control device.

12. 1. A computer-implemented optical path establishment method for an optical communication system having a communication control unit that controls establishment of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices, and an optical multiplexing / demultiplexing unit that multiplexes / demultiplexes signal light of control signals transmitted between each of the plurality of first communication devices and the communication control unit after the optical path is established, the method comprising: an acquiring step of acquiring information indicating a round-trip propagation time of each signal light traveling between the communication control unit and each of the plurality of first communication devices; a control step of permitting each of the plurality of first communication devices to transmit an uplink control signal based on the round-trip propagation time, thereby controlling reception timings of the uplink control signals transmitted from each of the plurality of first communication devices to a communication control unit to be different from each other; An optical path opening method comprising:

13. 1. An optical path opening method by a computer of a communication control device that controls opening of an optical path between any one of a plurality of first communication devices and any one of a plurality of second communication devices, comprising: an acquisition step of acquiring information indicating a round-trip propagation time of each signal light traveling between the communication control device and each of the plurality of first communication devices via an optical multiplexing / demultiplexing unit; a control step of permitting each of the plurality of first communication devices to transmit an uplink control signal based on the round-trip propagation time, thereby controlling reception timings of the uplink control signals transmitted from each of the plurality of first communication devices to the communication control device to be different from each other; and The optical multiplexing / demultiplexing unit a plurality of first optical multiplexing / demultiplexing units provided in a plurality of optical transmission lines respectively connected to the plurality of first communication devices; a second optical multiplexing / demultiplexing unit connected to the plurality of first optical multiplexing / demultiplexing units; Equipped with the first optical multiplexing / demultiplexing unit outputs the upstream control signal transmitted from the first communication device to the second optical multiplexing / demultiplexing unit; The second optical multiplexing / demultiplexing unit multiplexes the upstream control signals output from the plurality of first optical multiplexing / demultiplexing units and outputs the multiplexed signals to the communication control device. How to activate an optical path.

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