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

Abstract

One aspect of the present invention is an optical communication system comprising: a management device that allocates a frequency in response to a connection request transmitted by a subscriber device and including destination information indicating a subscriber device that is a transmission destination of an optical signal; a plurality of Contention-type optical distribution devices; an optical switch that is positioned between the optical distribution device and the subscriber device and that does not multiplex an optical signal; and a control unit that controls the operation of the optical distribution device and the optical switch. The control unit includes an optical transmission device that, when a plurality of optical signals having the same frequency transmitted from different subscriber devices are input to the optical switch, controls the operation of the optical switch to cause each optical signal input to the optical switch to be output to a different optical distribution device. The management device transmits the destination information to the optical transmission device. The optical transmission device controls the operation of the optical distribution device on the basis of the destination information.

Description

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

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

[0002] In optical communications that transmit optical signals sent from subscriber devices, there is a technology that uses a contention-type optical multiplexer to transmit optical signals to a destination while reducing delay (see Patent Document 1). An optical multiplexer has optical add / drop functions and outputs propagated optical signals to a destination path.

[0003] More specifically, the optical multiplexer outputs propagated optical signals to the destination paths, and for upstream optical signals with the same destination path, it multiplexes the signals and outputs them to the destination paths. Furthermore, for multiplexed downstream optical signals, the optical multiplexer extracts an optical signal with a frequency to be sent to that path from the multiplexed optical signals for each destination path, and outputs it to that path.

[0004] The optical multiplexer is, for example, a multicast switch or a WSS (Wavelength Selective Switch). Note that multiplexing is performed by a device that generates a composite wave of light, such as a coupler. A direction is a path along which an optical signal propagates. Therefore, a direction refers to, for example, a core of an optical fiber. If the optical fiber is multi-core, each core is a different direction from the others.

[0005] International Publication No. 2021 / 131001

[0006] However, because this technology uses a contention-type optical distributor, if optical signals transmitted from different subscriber devices have the same frequency, collisions can occur, preventing each optical signal from reaching its destination. To address this issue, a different frequency has traditionally been assigned to each subscriber device. In other words, the same wavelength has not been used for two signals traveling in different directions. However, this increases the number of frequencies used in proportion to the number of subscriber devices in operation, potentially making it difficult to keep up with the increasing traffic volume each year.

[0007] In view of the above circumstances, an object of the present invention is to provide a technique that enables allocation of the same frequency to different subscriber devices in optical communications using a contention-type optical multiplexer.

[0008] One aspect of the present invention is an optical communication system comprising: a management device that allocates frequencies in response to connection requests sent from subscriber devices, the connection requests including destination information indicating the subscriber devices to which optical signals are to be sent; a plurality of contention-type optical distributors; an optical switch located between the optical distributors and the subscriber devices and that does not multiplex optical signals; and a control unit that controls the operation of the optical distributors and the optical switch, wherein when a plurality of optical signals having the same frequency sent from different subscriber devices are input to the optical switch, the control unit controls the operation of the optical switch to output each optical signal input to the optical switch to a different optical distributor; and an optical transmission device, wherein the management device transmits the destination information to the optical transmission device, and the optical transmission device controls the operation of the optical distributors based on the destination information.

[0009] One aspect of the present invention is an optical transmission device comprising a plurality of contention-type optical distributors, an optical switch located between the optical distributors and subscriber devices that does not multiplex optical signals, and a control unit that controls the operation of the optical distributors and the optical switch, wherein when a plurality of optical signals having the same frequency transmitted from different subscriber devices are input to the optical switch, the control unit controls the operation of the optical switch to output each optical signal input to a different optical distributor.

[0010] One aspect of the present invention is an optical communication method executed by an optical communication system comprising: a management device that allocates frequencies in response to connection requests sent by subscriber devices, the connection requests including destination information indicating the subscriber devices to which optical signals are to be sent; a plurality of contention-type optical distributors; an optical switch located between the optical distributors and the subscriber devices and that does not multiplex optical signals; and a control unit that controls the operation of the optical distributors and the optical switch, wherein when a plurality of optical signals having the same frequency sent from different subscriber devices are input to the optical switch, the control unit controls the operation of the optical switch to output each optical signal input to the optical switch to a different optical distributor; and an optical communication system in which the management device transmits the destination information to the optical transmission device, the optical communication method including a control step in which the optical transmission device controls the operation of the optical distributors based on the destination information.

[0011] According to the present invention, it becomes possible to allocate the same frequency to different subscriber devices in optical communications using a contention-type optical multiplexer.

[0012] An explanatory diagram for explaining an optical communication system according to an embodiment. A diagram showing an example of the hardware configuration of a subscriber device according to an embodiment. A diagram showing an example of the hardware configuration of an optical transmission device according to an embodiment. A diagram showing an example of the hardware configuration of a management device according to an embodiment. A diagram showing an example of the flow of processing executed by an optical communication system according to an embodiment.

[0013] 1 is an explanatory diagram illustrating an optical communication system 100 according to an embodiment. The optical communication system 100 includes a plurality of subscriber devices 1, at least one optical transmission device 2, and a management device 3. In the optical communication system 100, optical communication is performed between the subscriber devices 1.

[0014] The subscriber device 1 includes an optical transceiver 11 and a control unit 12. The control unit 12 includes a processor 91, such as a central processing unit (CPU), a graphics processing unit (GPU), or a neural network processing unit (NPU), and a memory 92, which are connected by a bus.

[0015] The optical transceiver 11 includes an optical transmitter (Tx) 111 and an optical receiver (Rx) 112. The optical transceiver 11 is a wavelength-tunable optical transmitter / receiver. For example, the optical transceiver 11 is an optical transceiver with an AMCC (Auxiliary Management and Control Channel) function. The optical transceiver 11 outputs an optical signal under the control of the control unit 12.

[0016] The subscriber device 1 sends a connection request to the management device 3 when the device itself obtains the destination information, the transmission target information, and the communication start instruction, such as when the destination information, the transmission target information, and the communication start instruction are input by a user or another device other than the device itself.

[0017] The destination information is information that indicates the subscriber device 1 of the communication partner. The transmission target information is information to be sent to the subscriber device 1 (i.e., the communication partner) indicated by the destination information. The communication start instruction is an instruction to start communication with the subscriber device 1 indicated by the destination information. The connection request is information that includes the destination information. The connection request can be said to be information that requests frequency allocation, since the management device 3 that receives it allocates a frequency to be used for communication with the communication partner indicated by the destination information.

[0018] When a frequency is assigned in response to a connection request, the subscriber device 1 outputs an optical signal of the assigned frequency that carries the information to be transmitted. After the connection request is transmitted, until the subscriber device 1 outputs the optical signal, an optical signal propagation path is formed in the optical communication system 100 that connects the subscriber device 1 that is the sender of the optical signal carrying the information to be transmitted to the subscriber device 1 indicated by the destination information.

[0019] The propagation path is formed by the operations of the management device 3 and the optical transmission device 2. The propagation path is formed until the subscriber device 1 outputs an optical signal of the assigned frequency, for example, until the management device 3 completes frequency allocation. Therefore, after frequency allocation, the subscriber device 1 simply needs to output an optical signal of the assigned frequency that carries the information to be transmitted.

[0020] The optical transmission device 2 includes a plurality of optical distributors 21, an optical switch 22, and a control unit 23 including a processor 93 such as a CPU, GPU, or NPU, and a memory 94, all connected by a bus.

[0021] The optical multiplexer 21 is a contention type optical multiplexer. The optical multiplexer outputs propagated optical signals to the destination path, and multiplexes upstream optical signals with the same destination path before outputting them to the destination path. For downstream optical signals that are multiplexed, the optical multiplexer 21 inputs multiplexed signals from multiple paths and outputs the required signals to each subscriber device.

[0022] Therefore, the optical distributor 21 is, for example, a multicast switch. The optical distributor 21 may also be, for example, a WSS (Wavelength Selective Switch).

[0023] The optical switch 22 is an optical switch that does not multiplex optical signals. One difference between the optical multiplexer 21 and the optical switch 22 is that the optical multiplexer 21 multiplexes optical signals of the upstream direction that have the same route, whereas the optical switch 22 does not multiplex optical signals, whether they are upstream or downstream optical signals.

[0024] Note that a direction refers to a path along which an optical signal propagates, such as each core of an optical fiber. For example, if the optical fiber is a multi-core optical fiber, each core is a different direction.

[0025] The optical switch 22 is, for example, a fiber cross connect. The optical switch 22 may also be, for example, a MEMS (Micro Electro Mechanical Systems).

[0026] The optical switch 22 is located between the optical distributor 21 and the subscriber device 1, which is the source of the optical signal carrying the information to be transmitted. The optical switch 22 receives an upstream optical signal transmitted by the subscriber device 1 and outputs it to the optical distributor 21, and receives a downstream optical signal propagating from the optical distributor 21 and outputs it to the subscriber device 1.

[0027] The control unit 23 controls the operations of the optical distributor 21 and the optical switch 22. The control unit 23 executes, for example, an optical switch control process. The optical switch control process is a process in which, when multiple optical signals having the same frequency transmitted from different subscriber devices 1 are input to the optical switch 22, the operation of the optical switch 22 is controlled to output each optical signal input to the optical switch 22 to a different optical distributor 21.

[0028] To facilitate understanding of the optical switch control process, a more specific example will be used for further explanation. For example, consider a case where a first subscriber device 1 transmits an optical signal with a frequency ω (hereinafter referred to as the "first signal") and a second subscriber device 1 transmits an optical signal with a frequency ω (hereinafter referred to as the "second signal"). Therefore, the frequency of the first signal is the same as the frequency of the second signal.

[0029] In such a case, if the first signal and the second signal are input to the same optical multiplexer 21, the first signal and the second signal will be multiplexed in the optical multiplexer 21. Multiplexing the same frequency makes it impossible to subsequently obtain the signal before multiplexing. Therefore, once the first signal and the second signal are multiplexed, they cannot be separated from each other. As a result, even if the first signal and the second signal are transmitted to the respective destination subscriber devices 1, they may not be received correctly.

[0030] Therefore, the control unit 23 controls the operation of the optical switch 22 so that the first signal and the second signal are input to different optical multiplexers 21. As described above, the optical switch 22 does not perform multiplexing. Therefore, the first signal and the second signal are not multiplexed in the optical switch 22.

[0031] In this way, an example of optical switch control processing is processing for controlling the operation of the optical switch 22 so that the first signal and the second signal are input to different optical distributors 21. If the first signal and the second signal are input to different optical distributors 21, the first signal and the second signal are not multiplexed by the optical distributor 21, and therefore both the first signal and the second signal can be transmitted to and correctly received by the respective destination subscriber devices 1.

[0032] In this way, the optical transmission device 2 and the optical communication system 100 including the optical transmission device 2 can allocate the same frequency to different subscriber devices in optical communication using a contention-type optical multiplexer.

[0033] The management device 3 manages the subscriber device 1 and the optical transmission device 2. Specifically, the management involves performing a frequency allocation process, a frequency notification process, and a management information notification process in response to a connection request sent by the subscriber device 1.

[0034] The frequency allocation process is a process of allocating a frequency to the subscriber device 1 that has sent the connection request in accordance with a predetermined rule regarding frequency allocation (hereinafter referred to as "allocation rule"). An example of the allocation rule will be described.

[0035] <First Rule> The allocation rule is, for example, Rule 1. Rule 1 is a rule that, among predetermined candidate frequencies for allocation, frequencies are allocated in order of the energy required to generate one photon, starting with the frequency that requires the least amount of energy, until the number of subscriber devices 1 to which the frequencies have been allocated reaches a predetermined number, and the predetermined number is two or more for at least some of the candidates.

[0036] <Effects of Rule 1> The less energy required to generate one photon, the less energy required to generate an optical signal. Therefore, when an optical signal is generated under Rule 1, the energy required to generate an optical signal in the optical communication system 100 can be reduced.

[0037] <Second Rule> The allocation rule is, for example, Rule 2. Rule 2 states that, from among predetermined candidate frequencies for allocation, frequencies are allocated in descending order of the optical receiving sensitivity of the optical receiver 112 until the number of subscriber devices 1 to which the frequencies have been allocated reaches a predetermined number, and that the predetermined number is two or more for at least some of the candidates.

[0038] <Effects of the Second Rule> When the optical receiver 112 receives an optical signal of a frequency for which the optical receiver 112 has a higher optical sensitivity, the signal strength of the optical signal may be smaller than when the optical receiver 112 receives an optical signal of a frequency for which the optical sensitivity is lower. Therefore, when frequencies are allocated in accordance with the second rule, it is possible to reduce the energy required to generate an optical signal in the optical communication system 100.

[0039] The allocation rule may be, for example, Rule 3. Rule 3 is a rule that, among predetermined candidate frequencies for allocation, frequencies are allocated in ascending order of the value obtained by dividing the energy required to generate one photon by the optical sensitivity of the optical receiver 112, until the number of subscriber devices 1 to which the frequencies have been allocated reaches a predetermined number, and the predetermined number is two or more for at least some of the candidates.

[0040] <Effects of Rule 3> When frequencies are allocated according to Rule 3, it is possible to reduce the energy required to generate an optical signal that can be detected by a communication partner. Therefore, when frequencies are allocated according to Rule 3, it is possible to reduce the energy required to generate an optical signal in the entire optical communication system 100.

[0041] As exemplified by the first to third rules, the allocation rule may be a rule that at least some of the predetermined candidate frequencies for allocation are allocated to two or more subscriber devices 1.

[0042] The frequency notification process is a process of notifying the subscriber device 1 that is the source of the connection request of the frequency assigned to the subscriber device 1 in the frequency assignment process. Upon receiving the notification of the frequency assigned in the frequency assignment process, the subscriber device 1 that is the source of the connection request outputs an optical signal of the assigned frequency that carries the information to be transmitted. The output optical signal propagates to the optical transmission device 2.

[0043] Communication between the subscriber device 1 and the management device 3 may be carried out using an optical signal of a predetermined frequency different from the frequency that can be assigned by the frequency assignment process, or may be carried out by superimposing a signal on the optical signal at a speed slower than the information to be transmitted.

[0044] The management information notification process is a process of transmitting management information to the optical transmission device 2. The management information includes at least connection device information, which is information indicating the subscriber device 1 that has made the connection request, and frequency information indicating each frequency assigned to each subscriber device 1 that has made the connection request. The management information may also include information indicating, for each subscriber device 1 that has made a connection request, a set of information indicating the subscriber device 1 that has made the connection request and destination information transmitted by that subscriber device 1 (hereinafter referred to as "destination information group information").

[0045] The connection device information and frequency information included in the management information are used in the optical switch control process. If the connection device information and frequency information acquired by the optical transmission device 2 indicate that optical signals of the same frequency are transmitted from multiple subscriber devices 1, the control unit 23 executes the optical switch control process. In such a case, the control unit 23 controls the operation of the optical switch 22 based on the connection device information and frequency information so that optical signals from different subscriber devices 1 are transmitted to different optical multiplexers 21.

[0046] Furthermore, the control unit 23 executes an optical distributor control process. The optical distributor control process is a process for controlling the operation of each optical distributor 21 based on the destination information included in the destination information group information so that each optical signal is transmitted from the optical distributor 21 to the subscriber device 1 indicated by the destination information. The optical distributor control process may be executed on the optical distributor 21 to which the optical signal is transmitted from the optical switch 22 by the optical switch control process.

[0047] An example of control of the operation of the optical distributor 21 so that each optical signal is transmitted from the optical distributor 21 to the subscriber device 1 indicated by the destination information will be described. One example is a process of connecting an input port and an output port based on the destination information and output route information so that the optical signal is transmitted to the subscriber device 1 indicated by the destination information. With this connection, the optical signal input to the input port is output from the output port so that it is transmitted to the subscriber device 1 indicated by the destination information.

[0048] The input port is a port where an optical signal is input, and the output port is a port where an optical signal is output. The output route information is predetermined information that indicates, for each optical distributor 21, the relationship between the subscriber device 1 indicated by the destination information and the route from which the optical signal is output.

[0049] A direction is a path along which an optical signal propagates. Therefore, a direction refers to, for example, a core of an optical fiber. If the optical fiber has multiple cores, each core is a different direction.

[0050] In addition, if the connection device information and frequency information acquired by the optical transmission device 2 do not indicate that optical signals of the same frequency are transmitted from multiple subscriber devices 1, the operation of the control unit 23 and the operation of the optical distributor 21 may be similar to well-known technology, for example, similar to the technology of Patent Document 1.

[0051] 2 is a diagram showing an example of the hardware configuration of the subscriber device 1 according to the embodiment. The subscriber device 1 includes a control unit 12 having a processor 91 and a memory 92 connected by a bus as described above, and executes a program. By executing the program, the subscriber device 1 functions as a device including an optical transceiver 11, a control unit 12, an interface unit 13, and a storage unit 14.

[0052] More specifically, the processor 91 reads a program stored in the storage unit 14 and stores the read program in the memory 92. When the processor 91 executes the program stored in the memory 92, the subscriber device 1 functions as a device including the optical transceiver 11, the control unit 12, the interface unit 13, and the storage unit 14.

[0053] The control unit 12 controls the operation of each functional unit included in the subscriber device 1. The control unit 12 controls, for example, the operation of the optical transceiver 11. When the control unit 12 receives the transmission target information, destination information, and a communication start instruction via, for example, the interface unit 13, it controls the operation of the interface unit 13 to transmit a connection request to the management device 3.

[0054] When the control unit 12 receives the allocated frequency from the management device 3 through the frequency notification process, the control unit 12 controls the operation of the optical transceiver 11 to cause the optical transceiver 11 to output an optical signal of the notified frequency that carries the information to be transmitted. The control unit 12 acquires, for example, information stored in the memory unit 14. Specifically, the process of acquiring the information stored in the memory unit 14 is a read process.

[0055] The interface unit 13 includes a communication interface for connecting the subscriber device 1 to an external device. The interface unit 13 communicates with the external device via wired or wireless communication. The external device is, for example, the management device 3. The interface unit 13 communicates with the management device 3 to send a connection request to the management device 3. The interface unit 13 acquires information indicating the frequency allocated by the frequency allocation process through communication with the management device 3.

[0056] The interface unit 13 may be configured to include input devices such as a mouse, keyboard, touch panel, microphone, etc. The interface unit 13 may be configured as an interface that connects these input devices to the subscriber device 1. In this way, the interface unit 13 accepts input of various information to the subscriber device 1 via the input device or communication interface.

[0057] For example, destination information, transmission target information, and a communication start instruction are input to the interface unit 13. The destination information, transmission target information, and communication start instruction are input to the subscriber device 1 by, for example, a user via an input device or a communication interface provided in the interface unit 13.

[0058] The interface unit 13 outputs, for example, various types of information. The interface unit 13 includes a display device such as a CRT (Cathode Ray Tube) display, a liquid crystal display, or an organic EL (Electro-Luminescence) display. The interface unit 13 may be configured as an interface that connects these display devices to the subscriber device 1. The display device of the interface unit 13 outputs, for example, information input to a communication interface or input device of the interface unit 13.

[0059] The storage unit 14 is configured using a computer-readable storage medium device (non-transitory computer-readable recording medium) such as a magnetic hard disk device or a semiconductor storage device. The storage unit 14 stores various information related to the subscriber device 1. The storage unit 14 stores various information generated by the operation of the control unit 12, for example. The storage unit 14 stores information acquired by the interface unit 13, for example.

[0060] 3 is a diagram illustrating an example of a hardware configuration of the optical transmission device 2 according to an embodiment. The optical transmission device 2 includes a control unit 23 including a processor 93 and a memory 94 connected by a bus, and executes a program. By executing the program, the optical transmission device 2 functions as a device including a plurality of contention-type optical distributors 21, an optical switch 22, the control unit 23, an interface unit 24, and a storage unit 25.

[0061] More specifically, the processor 93 reads out a program stored in the storage unit 25 and stores the read program in the memory 94. When the processor 93 executes the program stored in the memory 94, the optical transmission device 2 functions as a device including a plurality of contention-type optical distributors 21, an optical switch 22, a control unit 23, an interface unit 24, and a storage unit 25.

[0062] The control unit 23 controls the operation of each functional unit included in the optical transmission device 2. The control unit 23, for example, acquires management information. The control unit 23, for example, executes optical switch control processing. The control unit 23, for example, executes optical distributor control processing. The control unit 23, for example, acquires information stored in the memory unit 25. Specifically, the process of acquiring information stored in the memory unit 25 is reading.

[0063] The interface unit 24 includes a communication interface for connecting the optical transmission device 2 to an external device. The interface unit 24 communicates with the external device via wired or wireless communication. The external device is, for example, the management device 3. The interface unit 24 acquires management information through communication with the management device 3.

[0064] The interface unit 24 may be configured to include input devices such as a mouse, a keyboard, a touch panel, and a microphone. The interface unit 24 may be configured as an interface that connects these input devices to the optical transmission device 2. In this way, the interface unit 24 accepts input of various information to the optical transmission device 2 via the input device or communication interface.

[0065] The interface unit 24 outputs, for example, various types of information. The interface unit 24 includes a display device such as a CRT display, a liquid crystal display, or an organic EL display. The interface unit 24 may be configured as an interface that connects these display devices to the optical transmission device 2. The display device of the interface unit 24 outputs, for example, information input to an input device or a communication interface of the interface unit 24.

[0066] The storage unit 25 is configured using a computer-readable storage medium device (non-transitory computer-readable recording medium) such as a magnetic hard disk device or a semiconductor storage device. The storage unit 25 stores various information related to the optical transmission device 2. The storage unit 25 stores various information generated by the operation of the control unit 23, for example. The storage unit 25 stores information acquired by the interface unit 24, for example.

[0067] 4 is a diagram illustrating an example of the hardware configuration of the management device 3 according to an embodiment. The management device 3 includes a control unit 31 including a processor 95 and a memory 96 connected via a bus, and executes a program. By executing the program, the management device 3 functions as a device including the control unit 31, an interface unit 32, and a storage unit 33.

[0068] More specifically, the processor 95 reads the program stored in the storage unit 33 and stores the read program in the memory 96. When the processor 95 executes the program stored in the memory 96, the management device 3 functions as a device including the control unit 31, the interface unit 32, and the storage unit 33.

[0069] The control unit 31 controls the operation of each functional unit included in the management device 3. For example, when the control unit 31 receives a connection request via the interface unit 32, the control unit 31 executes a frequency allocation process and a management information notification process. After executing the frequency allocation process, the control unit 31 executes, for example, a frequency notification process. The control unit 31 acquires, for example, information stored in the memory unit 33. Specifically, the process of acquiring the information stored in the memory unit 33 is reading.

[0070] The interface unit 32 includes a communication interface for connecting the management device 3 to an external device. The interface unit 32 communicates with the external device via wired or wireless communication. The external device is, for example, the subscriber device 1. The interface unit 32 obtains a connection request by communicating with the subscriber device 1. The interface unit 32 transmits information indicating the frequency assigned by the frequency assignment process to the subscriber device 1 by communicating with the subscriber device 1. The external device is, for example, the optical transmission device 2. The interface unit 32 transmits management information to the optical transmission device 2 by communicating with the optical transmission device 2.

[0071] The interface unit 32 may be configured to include input devices such as a mouse, keyboard, touch panel, and microphone. The interface unit 32 may be configured as an interface that connects these input devices to the management device 3. In this way, the interface unit 32 accepts input of various information to the management device 3 via the input device or communication interface.

[0072] The interface unit 32 outputs, for example, various types of information. The interface unit 32 includes a display device such as a CRT display, a liquid crystal display, or an organic EL display. The interface unit 32 may be configured as an interface that connects these display devices to the management device 3. The display device of the interface unit 32 outputs, for example, information input to a communication interface or an input device of the interface unit 32.

[0073] The storage unit 33 is configured using a computer-readable storage medium device (non-transitory computer-readable recording medium) such as a magnetic hard disk device or a semiconductor storage device. The storage unit 33 stores various information related to the management device 3. The storage unit 33 stores, for example, various information generated by the operation of the control unit 31. The storage unit 33 stores, for example, information acquired by the interface unit 32.

[0074] 5 is a diagram showing an example of the flow of processing executed by the optical communication system 100 according to the embodiment. Note that, here, an example will be described in which the same frequency is assigned to multiple different subscriber devices 1 as a result of the execution of the frequency assignment processing.

[0075] A plurality of subscriber devices 1 acquire destination information, transmission target information, and a communication start instruction (step S101). Next, each subscriber device 1 to which the destination information, transmission target information, and communication start instruction have been input transmits a connection request to the management device 3 (step S102). Next, the management device 3 executes a frequency allocation process (step S103). By executing the frequency allocation process in step S103, a frequency is assigned to each subscriber device 1 that transmitted a connection request based on the connection request acquired in step S102, in accordance with the allocation rule. At this time, the same frequency is assigned to a plurality of subscriber devices 1.

[0076] Next, the management device 3 executes a management information notification process (step S104). By executing the management information notification process, the optical transmission device 2 acquires the management information. Next, the optical transmission device 2 executes an optical switch control process and an optical distributor control process to form a path along which the optical signal propagates from the subscriber device 1 to the subscriber device 1 indicated by the destination information (step S105).

[0077] Next, the management device 3 executes a frequency notification process (step S106). Note that the frequency notification process may be executed at any timing as long as the route has been formed by the time each subscriber device 1 outputs an optical signal. Therefore, for example, if the longest time required to form a route is predetermined, the frequency notification process may be executed after that time has elapsed.

[0078] Next, each subscriber device 1 outputs an optical signal of the frequency notified in step S106, which carries the information to be transmitted (step S107).

[0079] The optical transmission device 2 configured in this manner includes a plurality of optical multiplexers 21, which are contention-type optical multiplexers, as well as an optical switch 22 and a control unit 23, and executes optical switch control processing. As a result, even if optical signals of the same frequency are transmitted from different subscriber devices 1, the optical signals are not multiplexed. Therefore, the optical transmission device 2 makes it possible to allocate the same frequency to different subscriber devices in optical communications using contention-type optical multiplexers.

[0080] The optical communication system 100 configured as above also includes an optical transmission device 2. Therefore, the optical communication system 100 enables allocation of the same frequency to different subscriber devices in optical communication using a contention-type optical multiplexer.

[0081] (Modification) The number of output ports of the optical switch 22 may be greater than the number of input ports of one optical distributor 21. In this case, it is possible to distribute optical signals from a subscriber device to two or more optical distributors.

[0082] The optical communication system 100 may include multiple optical switches 22. In such a case, the upstream optical signal and the downstream optical signal among the optical signals may be input to different optical switches 22. By including multiple optical switches 22, even if one optical switch fails, communication may still be possible using the other optical switches 22. Therefore, by including different optical switches 22 for the upstream optical signal and the downstream optical signal, the optical communication system 100 can operate such that even if an error occurs in communication in one direction, communication in the other direction is not affected.

[0083] In transmission from the subscriber device 1 to the optical transmission device 2, the optical signal is transmitted through, for example, a single-core or multi-core optical fiber. In transmission from the optical transmission device 2 to the subscriber device 1, the optical signal is transmitted through, for example, a single-core or multi-core optical fiber.

[0084] The subscriber device 1 may be implemented using a plurality of information processing devices connected to each other via a network so that they can communicate with each other. In this case, the processes executed by the control unit 12 may be distributed among the plurality of information processing devices.

[0085] The optical transmission device 2 may be implemented using a plurality of information processing devices communicably connected via a network. In this case, the processes executed by the control unit 23 may be distributed among the plurality of information processing devices.

[0086] The management device 3 may be implemented using a plurality of information processing devices connected to each other via a network so as to be able to communicate with each other. In this case, the processes executed by the control unit 31 may be distributed among the plurality of information processing devices.

[0087] Note that all or part of the functions of the control unit 12, interface unit 13, memory unit 14, control unit 23, interface unit 24, memory unit 25, control unit 31, interface unit 32, and memory unit 33 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. The program may be transmitted via a telecommunications line.

[0088] 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.

[0089] 100...optical communication system, 1...subscriber device, 2...optical transmission device, 3...management device, 11...optical transceiver, 12...control unit, 13...interface unit, 14...storage unit, 21...optical distributor, 22...optical switch, 23...control unit, 24...interface unit, 25...storage unit, 31...control unit, 32...interface unit, 33...storage unit, 91...processor, 92...memory, 93...processor, 94...memory, 95...processor, 96...memory

Claims

1. An optical communication system comprising: a management device that assigns frequencies in response to connection requests sent by subscriber devices, the connection requests including destination information indicating the subscriber device to which the optical signals are to be sent; a plurality of contention type optical distributors; an optical switch that is located between the optical distributors and the subscriber devices and does not multiplex optical signals; and a control unit that controls operation of the optical distributor and the optical switch, wherein when a plurality of optical signals having the same frequency transmitted from different subscriber devices are input to the optical switch, the control unit controls operation of the optical switch to output each optical signal input to the optical switch to a different optical distributor; wherein the management device transmits the destination information to the optical transmission device, and the optical transmission device controls operation of the optical distributor based on the destination information.

2. The optical communication system according to claim 1, wherein the number of ports of said optical switch is greater than the number of ports of one of said optical distributors.

3. The optical communication system according to claim 1, wherein an upstream optical signal and a downstream optical signal among said optical signals are input to different optical switches.

4. The optical communication system of claim 1, wherein the allocation is performed according to the following rule: among predetermined candidate frequencies for allocation, the frequencies are allocated in order of the energy required to generate one photon, until the number of subscriber devices to which the frequencies have been allocated reaches a predetermined number, the predetermined number being 2 or more for at least some of the candidates.

5. The optical communication system according to claim 1, wherein the subscriber unit is equipped with an optical receiver, and the allocation is performed according to a rule that, among predetermined candidate frequencies for allocation, the frequencies are allocated in order of the optical receiver's optical sensitivity until the number of subscriber units to which the frequencies have been allocated reaches a predetermined number, and the predetermined number is 2 or more for at least some of the candidates.

6. The optical communication system according to claim 1, wherein the subscriber unit is equipped with an optical receiver, and the allocation is performed according to the following rule: among predetermined candidate frequencies for allocation, the frequencies are allocated in ascending order of the value obtained by dividing the energy required to generate one photon by the optical sensitivity of the optical receiver, until the number of subscriber units to which the frequencies have been allocated reaches a predetermined number, and the predetermined number is 2 or more for at least some of the candidates.

7. An optical transmission device comprising: a plurality of contention type optical distributors; an optical switch located between the optical distributors and subscriber devices and which does not multiplex optical signals; and a control unit which controls the operation of the optical distributor and the optical switch, wherein when a plurality of optical signals having the same frequency transmitted from different subscriber devices are input to the optical switch, the control unit controls the operation of the optical switch to output each optical signal input to the optical switch to a mutually different optical distributor.

8. An optical communication method executed by an optical communication system comprising: an optical transmission device comprising: a management device that assigns frequencies in response to a connection request sent by a subscriber device, the connection request including destination information indicating the subscriber device to which the optical signal is to be sent; a plurality of contention type optical distributors; an optical switch located between the optical distributors and the subscriber devices and that does not multiplex the optical signals; and a control unit that controls operation of the optical distributor and the optical switch, wherein when a plurality of optical signals having the same frequency transmitted from different subscriber devices are input to the optical switch, the control unit controls operation of the optical switch to output each optical signal input to the optical switch to a different optical distributor, and wherein the management device transmits the destination information to the optical transmission device, the optical communication method comprising: a control step in which the optical transmission device controls operation of the optical distributor based on the destination information.

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