Control device, optical communication system, and path control method

Abstract

A control device according to the present invention comprises: a path selection unit that acquires information, related to an optical transmission path in each of a plurality of connection paths formed by a combination of a plurality of optical transmission paths connecting one or more first communication devices and one or more second communication devices, or information related to an optical transmission path in a path in the middle of each of the plurality of connection paths, and selects, on the basis of the acquired information related to the optical transmission path, an optimal connection path, from among the plurality of connection paths, that satisfies a condition capable of reducing the influence of wavelength dispersion; and a path control unit that controls the paths so that communication can be performed using the optimal path selected by the path selection unit.　

Description

Control device, optical communication system, and routing method

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

[0002] In optical communication systems that transmit optical signals using optical fibers, if the wavelength deviates from the zero-dispersion wavelength of the optical fiber, the effect of dispersion increases, leading to a larger penalty and making long-distance transmission difficult. To achieve long-distance transmission, it is necessary to set the wavelengths used between the communication devices of the users communicating to approach the zero-dispersion wavelength.

[0003] However, because optical fibers exhibit fluctuations in the zero-dispersion wavelength between 1300 and 1324 nm, there is a problem in that the wavelength cannot be set unless the zero-dispersion wavelength value for each optical fiber used is known.

[0004] Therefore, a conventional method has been proposed to set the wavelength using an OTDR (Optical Time Domain Reflectometer). In this method, light emitted from the OTDR of device A is transmitted to device B, and the light is returned to the OTDR of device A by a mirror in device B, thereby measuring the zero dispersion value and switching the path between the transmitter and receiver. However, this method has the problem of complicating the system because it requires additional equipment.

[0005] To address this problem, a technique for estimating the zero-dispersion wavelength has been proposed as follows (see, for example, Non-Patent Documents 1 and 2). First, the communication device, based on the frequency spectrum data of the optical signal transmitted from the communication partner, determines the notch frequency f at which the first notch appears at frequencies other than multiples of the transmission signal frequency (1x, 2x, etc.). ０The first step is to determine the dispersion D using the oscillation wavelength λ of the communication partner, the speed of light c, the chirp parameter α, and the distance L between the communication devices. The communication device then estimates the value of the zero-dispersion wavelength by measuring the amount of deviation from the zero-dispersion wavelength position in the optical fiber by dividing the calculated dispersion D by the value of the dispersion slope. Here, the oscillation wavelength can be calculated based on the operating conditions of the transmitter, such as its temperature, and the distance L between the communication devices can be calculated based on a timestamp from a low-speed signal.

[0006] As described above, conventionally, each time a connection is made between user communication devices, the value of the zero-dispersion wavelength between the users is estimated, and the oscillation wavelength of each communication device is adjusted to the estimated zero-dispersion wavelength. This suppresses waveform degradation due to wavelength dispersion and enables long-distance transmission. This configuration eliminates the need for additional equipment.

[0007] Yasunari Tanaka et al., “Penalty-free 100-km Transmission of 53-Gbps / λ IM-DD Signal Enabled by a Novel Zero-dispersion Wavelength Estimation and Optimization Method”, 2023 Opto-Electronics and Communications Conference (OECC).Yasunari Tanaka et al., “Zero-Dispersion Wavelength Estimation and Optimization Method for Penalty-Free and Equalizer-Free 53-Gbps / λ IM-DD Transmission Over 100 Km”, JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 42, NO. 6, MARCH 15, 2024.

[0008] Conventional communication devices use tunable lasers or arrays of lasers that allow for the selection of multiple wavelengths as the optical signal transmitter, thereby matching the oscillation wavelength of the communication device to the zero-dispersion wavelength. However, some communication devices may have a single fixed-wavelength laser as the optical signal transmitter. In such cases, where the communication device has only one fixed-wavelength laser, it is not possible to set the oscillation wavelength of the transmitter to the zero-dispersion wavelength. As a result, communication devices with a single fixed-wavelength laser have the problem of not being able to extend the transmission distance.

[0009] In view of the above circumstances, the present invention aims to provide a technology that can extend the transmission distance of a communication device equipped with a single fixed-wavelength laser as a transmission function.

[0010] One aspect of the present invention is a control device comprising: a path selection unit that acquires information about optical transmission paths in each of a plurality of connection paths formed by a combination of a plurality of optical transmission paths connecting one or more first communication devices and one or more second communication devices, or information about optical transmission paths in the intermediate paths of each of the plurality of connection paths, and selects an optimal connection path from the plurality of connection paths that satisfies conditions that can reduce the effects of wavelength dispersion based on the acquired information about optical transmission paths; and a path control unit that controls the path so that communication can be performed on the optimal path selected by the path selection unit.

[0011] One aspect of the present invention is an optical communication system comprising one or more first communication devices, one or more second communication devices, and a control device, wherein the one or more first communication devices and the one or more second communication devices transmit optical signals of a specific wavelength, and the control device acquires information about optical transmission paths in each of a plurality of connection paths formed by a combination of a plurality of optical transmission paths connecting the one or more first communication devices and the one or more second communication devices, or information about optical transmission paths in the intermediate paths of each of the plurality of connection paths, and based on the acquired information about optical transmission paths, selects the optimal connection path among the plurality of connection paths that satisfies the conditions for reducing the effects of wavelength dispersion, and a path control unit controls the path so that communication can be performed on the optimal path selected by the path selection unit.

[0012] One aspect of the present invention is a route control method that acquires information about optical transmission paths in each of a plurality of connection paths formed by a combination of a plurality of optical transmission paths connecting one or more first communication devices and one or more second communication devices, or information about optical transmission paths in the middle of each of the plurality of connection paths, selects the optimal connection path from the plurality of connection paths that satisfies the conditions for reducing the effects of wavelength dispersion, and controls the path so that communication can be performed on the selected optimal path.

[0013] This invention makes it possible to extend the transmission distance of a communication device equipped with a single fixed-wavelength laser as a transmission function.

[0014] This figure shows an example configuration of the optical communication system in the first embodiment. This figure shows an example of the user management table and the zero-dispersion wavelength estimation value table in the first embodiment. This is a sequence diagram showing the processing flow performed by the optical communication system in the first embodiment. This is a sequence diagram showing the processing flow performed by the optical communication system in the first embodiment. This is a diagram for explaining the method of selecting the optimal connection path by the path selection unit in the first embodiment. This figure shows an example configuration of the optical communication system in the second embodiment. This is a sequence diagram showing the processing flow performed by the optical communication system in the second embodiment. This is a sequence diagram showing the processing flow performed by the optical communication system in the second embodiment. This figure shows an example configuration of the optical communication system in the third embodiment. This figure shows an example of the transmission path table in the third embodiment. This is a sequence diagram showing the processing flow performed by the optical communication system in the third embodiment. This is a sequence diagram showing the processing flow performed by the optical communication system in the third embodiment. The zero-dispersion wavelength value and distance L × dispersion slope S ０ This figure shows the relationship with the value. This figure shows the estimated zero-dispersion wavelength for each connection path. This figure shows an example of a notch frequency table in the fourth embodiment. This figure shows an example of a wavelength dispersion table in the fifth embodiment. This figure shows an example of the configuration of an optical communication system in the sixth embodiment. This figure shows an example of the configuration of an optical communication system in the seventh embodiment. This figure shows an example of a zero-dispersion wavelength estimate table held by the control device in the seventh embodiment. This figure shows an example of the configuration of an optical communication system in the eighth embodiment. This figure illustrates other application examples of the optical communication system in each embodiment. This figure illustrates other application examples of the optical communication system in any embodiment from the third to the eighth embodiment.

[0015] One embodiment of the present invention will be described below with reference to the drawings.

[0016] (First Embodiment) Figure 1 shows an example of the configuration of an optical communication system 100 in the first embodiment. The optical communication system 100 includes a communication device 10, a communication device 20, an optical distribution unit 30, an optical distribution unit 40, and a control device 50. Each communication device 10 and 20 performs optical communication via the optical distribution unit 30 and the optical distribution unit 40. The communication device 10 and the communication device 20 are located in geographically separated locations (for example, different bases).

[0017] Figure 1 shows an example where there is one communication device 10 and one communication device 20, but the number of communication devices 10 and 20 is not particularly limited. In the following explanation, the direction from communication device 10 to communication device 20 will be described as the upward direction, and the direction from communication device 20 to communication device 10 will be described as the downward direction.

[0018] The following connections are made via optical transmission lines: between the communication device 10 and the optical distribution unit 30, between the optical distribution unit 30 and the optical distribution unit 40, between the optical distribution unit 40 and the communication device 20, between the optical distribution unit 30 and the control device 50, and between the optical distribution unit 40 and the control device 50. The optical transmission lines are made of optical fibers. One or more optical amplifiers or optical multiplexers / demultiplexers such as couplers may be installed in the optical transmission lines to amplify the optical signals. The communication device 10 and the communication device 20 communicate using two-core transmission with two optical transmission lines.

[0019] The communication device 10 and the optical distribution unit 30 are connected by two optical transmission lines f11 and f13. The optical distribution unit 30 and the optical distribution unit 40 are connected by three optical transmission lines F1, F2 and F3. The optical distribution unit 40 and the communication device 20 are connected by two optical transmission lines f21 and f23. The number of optical transmission lines connecting the optical distribution unit 30 and the optical distribution unit 40 is not particularly limited and may be two or fewer, or four or more.

[0020] Optical transmission path f11 is connected to the transmitting side of communication device 10, and optical transmission path f13 is connected to the receiving side of communication device 10. Similarly, optical transmission path f21 is connected to the transmitting side of communication device 20, and optical transmission path f23 is connected to the receiving side of communication device 20. In the following description, the zero-dispersion wavelength λ in the path connecting the transmitting side of communication device j (for example, communication device 10 or communication device 20), the optical transmission path Fk (where k is an integer of 1 or more), and the receiving side of communication device l (for example, communication device 20 or communication device 10) is described. ０ to λ ０ This is represented as (j, k, l). For a single optical transmission path, if we set the subscripts of other parts to 0, for example, the zero-dispersion wavelength λ of optical transmission path F2 can be represented. ０ to λ ０ This is represented as (0, 2, 0).

[0021] Communication device 10 is a device that communicates with communication device 20 located in a geographically different location. Communication device 10 uses a single wavelength-fixed laser to send an optical signal of a specific wavelength to the optical transmission path f11. For example, communication device 10 uses a wavelength λ １ It emits an optical signal. A fixed-wavelength laser is a laser capable of emitting only optical signals of a specific wavelength.

[0022] The communication device 10 sends a connection request to the control device 50 during the initial connection. The initial connection may be the timing when the communication device 10 first connects to the optical distribution unit 30, the timing when it reconnects to the optical distribution unit 30 after being disconnected once, or the timing when it communicates with another communication device 20. The connection request includes at least identification information for identifying the communication devices 10 and 20, wavelength information indicating the wavelengths used by the communication devices 10 and 20 for communication, and information indicating the communication partner.

[0023] Communication device 20 is a device that communicates with communication device 10 located in a geographically different location. Communication device 20 uses a single wavelength-fixed laser to send an optical signal of a specific wavelength to the optical transmission path f21. For example, communication device 20 uses a wavelength λ ２ The optical signal is transmitted. The communication device 20 transmits a connection request to the control device 50 during the initial connection.

[0024] The optical distribution unit 30 has a function to switch connections between ports in response to control from the control device 50. Through this function, the optical distribution unit 30 distributes optical signals by outputting an optical signal input to one port from another port. This allows the optical distribution unit 30 to connect the communication device 10 and the communication device 20 via different paths. The optical distribution unit 30 has multiple ports. For example, the optical distribution unit 30 has ports 31-1 to 31-2, ports 32-1 to 32-3, and port 33. The number of ports on the optical distribution unit 30 is an example and is not limited to the above number of ports.

[0025] The communication device 10 is connected to ports 31-1 and 31-2 of the optical distribution unit 30 via optical transmission lines f11 and f13. The optical distribution unit 40 is connected to ports 32-1 to 32-3 of the optical distribution unit 30 via optical transmission lines F1 to F3. The control device 50 is connected to port 33 of the optical distribution unit 30 via an optical transmission line. The optical distribution unit 30 is composed of, for example, an optical switch or a wavelength selector switch. The optical distribution unit 30 may be composed of a combination of multiple wavelength selector switches, or a combination of an optical switch and a wavelength selector switch.

[0026] The optical distribution unit 40 has a function to switch connections between ports in response to control from the control device 50. Through this function, the optical distribution unit 40 distributes optical signals by outputting an optical signal input to one port from another port. This allows the optical distribution unit 40 to connect the communication device 10 and the communication device 20 via different paths. The optical distribution unit 40 has multiple ports. For example, the optical distribution unit 40 has ports 41-1 to 41-2, ports 42-1 to 42-3, and port 43. The number of ports on the optical distribution unit 40 is an example and is not limited to the number of ports shown above.

[0027] The optical distribution unit 40 has ports 41-1 and 41-2 to which the communication device 20 is connected via optical transmission lines f21 and f23. The optical distribution unit 30 is connected to the optical distribution unit 40 has ports 42-1 to 42-3 to which the optical distribution unit 40 is connected via optical transmission lines F1 to F3. The optical distribution unit 40 has port 43 to which the control device 50 is connected via an optical transmission line. The optical distribution unit 40 is composed of, for example, an optical switch or a wavelength selector switch. The optical distribution unit 40 may be composed of a combination of multiple wavelength selector switches, or a combination of an optical switch and a wavelength selector switch.

[0028] The control device 50 is a device that controls the entire optical communication system 100. The control device 50 includes an estimation function, a route control function, and a selection function. The estimation function is a function for estimating the zero-dispersion wavelength in a specific route. The route control function is a function for controlling the connections between the ports of the optical distribution units 30 and 40. The selection function is a function for selecting the optimal connection route between the communication device 10 and the communication device 20. The connection route is a route composed of a combination of multiple optical transmission paths connecting the communication device 10 and the communication device 20.

[0029] In the configuration shown in Figure 1, there are three possible connection paths in the upstream direction: for example, the combination of optical transmission paths f11 + F1 + f23, the combination of optical transmission paths f11 + F2 + f23, and the combination of optical transmission paths f11 + F3 + f23. Here, the connection path represented by the combination of optical transmission paths f11 + F1 + f23 is the path through which the optical signal sent from the communication device 10 reaches the communication device 20 via the optical transmission paths in the order of optical transmission path f11, optical transmission path F1, and optical transmission path f23.

[0030] In the configuration shown in Figure 1, there are three possible connection paths in the downstream direction: for example, the combination of optical transmission paths f21 + F1 + f13, the combination of optical transmission paths f21 + F2 + f13, and the combination of optical transmission paths f21 + F3 + f13. Here, the connection path represented by the combination of optical transmission paths f21 + F1 + f13 is the path through which the optical signal sent from the communication device 20 reaches the communication device 10 via the optical transmission paths in the order of optical transmission path f21, optical transmission path F1, and optical transmission path f13.

[0031] The control device 50 selects, by means of a selection function, an optimal connection path in the upstream direction among a plurality of connection paths in the upstream direction, and selects an optimal connection path in the downstream direction among a plurality of connection paths in the downstream direction.

[0032] Further, the control device 50 holds a user management table and a zero-dispersion wavelength estimated value table. The user management table is a table in which information regarding the communication devices 10 and 20 that use the optical communication system 100 is registered. The zero-dispersion wavelength estimated value table is a table in which information regarding the zero-dispersion wavelength for each connection path is tabulated.

[0033] The control device 50 estimates the zero-dispersion wavelength for each connection path, and registers the value of the zero-dispersion wavelength for each estimated connection path in the zero-dispersion wavelength estimated value table. The zero-dispersion wavelength is an example of information regarding the optical transmission path. The control device 50 selects, based on the value of the zero-dispersion wavelength for each connection path registered in the zero-dispersion wavelength estimated value table and the information registered in the user management table, an optimal connection path for connecting between the communication device 10 and the communication device 20 in each of the upstream direction and the downstream direction. That is, the control device 50 selects an optimal connection path in the upstream direction for transmitting the optical signal sent from the communication device 10 to the communication device 20, and an optimal connection path in the downstream direction for transmitting the optical signal sent from the communication device 20 to the communication device 10. Then, the control device 50 controls the connection between the ports of the optical branching units 30 and 40 so as to connect the communication device 10 and the communication device 20 via the selected optimal connection path.

[0034] (Configuration example of the communication device 10) The communication device 10 includes a transmission unit 11 and a reception unit 12. The transmission unit 11 and the reception unit 12 are connected to different optical transmission paths. The transmission unit 11 is composed of one wavelength-fixed laser. The transmission unit 11 １ sends an optical signal having a wavelength of λ ２The optical signal is received via the optical transmission path f13.

[0035] (Example of the configuration of the communication device 20) The communication device 20 comprises a transmitting unit 21 and a receiving unit 22. The transmitting unit 21 and the receiving unit 22 are connected to different optical transmission paths. The transmitting unit 21 is composed of a single wavelength fixed laser. The transmitting unit 21 has a wavelength λ ２ The optical signal is sent to the optical transmission path f21. The transmitting unit 21 sends an optical signal including a connection request to the optical transmission path f21 during the initial connection. After the path control by the control device 50 is completed, the transmitting unit 21 sends an optical signal including the transmission data to the optical transmission path f21. The receiving unit 22 receives the wavelength λ transmitted from the communication device 10. １ The optical signal is received via the optical transmission path f23.

[0036] (Example of configuration of control device 50) The control device 50 comprises a communication unit 51, a communication unit 52, a control unit 53, and a storage unit 54. The communication unit 51 receives optical signals sent from the communication device 10 via the optical distribution unit 30. The communication unit 51 receives optical signals including, for example, connection requests. The communication unit 51 also sends optical signals including control instructions addressed to the communication device 10 to the optical distribution unit 30.

[0037] The communication unit 52 receives the optical signal transmitted from the communication device 20 via the optical distribution unit 40. The communication unit 52 receives, for example, an optical signal including a connection request. The communication unit 52 also sends an optical signal including a control instruction addressed to the communication device 20 to the optical distribution unit 40.

[0038] The control unit 53 controls the entire control device 50. The control unit 53 is configured using a processor such as a CPU (Central Processing Unit) and memory. By executing a program, the control unit 53 realizes the functions of the user management unit 531, the estimation unit 532, the route selection unit 533, and the route control unit 534.

[0039] The user management unit 531 manages information on communication devices 10 and 20, which are users of the optical communication system 100. For example, when a connection request is received, the user management unit 531 registers the identification information and wavelength information included in the received connection request into the user management table.

[0040] The estimation unit 532 estimates the zero-dispersion wavelength value for each connection path. Specifically, the estimation unit 532 first acquires signal waveform data based on the optical signals transmitted in each connection path in the upstream direction from the communication device 20. Using the acquired signal waveform data, the estimation unit 532 estimates the zero-dispersion wavelength value in the upstream direction for each connection path. Similarly, the estimation unit 532 acquires signal waveform data based on the optical signals transmitted in each connection path in the downstream direction from the communication device 10. Using the acquired signal waveform data, the estimation unit 532 estimates the zero-dispersion wavelength value in the downstream direction for each connection path. Existing methods are used for estimating the zero-dispersion wavelength. For example, the method described in Non-Patent Document 1 or 2 may be used as the method for estimating the zero-dispersion wavelength, or other methods may be used. In this way, the estimation unit 532 estimates the zero-dispersion wavelength value for each connection path using existing methods.

[0041] Furthermore, the estimation unit 532 also acquires information on the distance of each optical transmission path, which is used when estimating the value of the zero-dispersion wavelength. The information on the distance of each optical transmission path may be pre-registered or calculated based on a timestamp from a low-speed signal or the like. The dispersion slope value may be the dispersion slope value of the optical fiber being used, or it may be the dispersion slope value specified by standardization. The estimation unit 532 registers the estimated zero-dispersion wavelength value of each connection path in the zero-dispersion wavelength estimation value table. The estimation unit 532 is an example of an acquisition unit.

[0042] The route selection unit 533 selects the optimal connection route between the communication device 10 and the communication device 20 based on the zero-dispersion wavelength values ​​of each connection route registered in the zero-dispersion wavelength estimation table and the information registered in the user management table. The route selection unit 533 selects the optimal connection route from among multiple connection routes that satisfies the conditions for reducing the effects of wavelength dispersion as the optimal connection route between the communication device 10 and the communication device 20. Specifically, the route selection unit 533 calculates the absolute difference between the zero-dispersion wavelength value of each connection route and the oscillation wavelength value of the communication devices 10 and 20. For example, the route selection unit 533 calculates the absolute difference between the zero-dispersion wavelength value of each connection route in the upstream direction and the oscillation wavelength value of the communication device 10, and calculates the absolute difference between the zero-dispersion wavelength value of each connection route in the downstream direction and the oscillation wavelength value of the communication device 20.

[0043] The route selection unit 533 selects the route with the smallest difference in absolute values ​​calculated for each connection route in the upstream direction as the optimal connection route in the upstream direction (optimal route for communication device 10), and selects the route with the smallest difference in absolute values ​​calculated for each connection route in the downstream direction as the optimal connection route in the downstream direction (optimal route for communication device 20). The smaller the difference in absolute values, the more effectively waveform degradation due to wavelength dispersion in the connection route connecting communication device 10 and communication device 20 can be suppressed.

[0044] As described above, the route selection unit 533 selects the optimal connection route to be used for upstream communication and the optimal connection route to be used for downstream communication.

[0045] The route control unit 534 controls the connections between the ports of the optical distribution units 30 and 40. For example, the route control unit 534 controls the connections between the ports of the optical distribution units 30 and 40 so that bidirectional communication can be performed between the communication device 10 and the communication device 20 via the optimal connection path selected by the route selection unit 533.

[0046] The storage unit 54 stores a user management table and a zero-dispersion wavelength estimation table. The storage unit 54 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device.

[0047] Figure 2 shows an example of a user management table and a zero-dispersion wavelength estimation table in the first embodiment. Figure 2(A) shows an example of the user management table, and Figure 2(B) shows an example of the zero-dispersion wavelength estimation table. The user management table has multiple records representing information about users who use the optical communication system 100. The records in the user management table have identification information and values ​​of the oscillation wavelength. The identification information represents identification information for identifying the communication devices 10 and 20 that use the optical communication system 100. In Figure 2(A), the communication devices 10 and 20 are shown as the identification information. The value of the identification information can be any information that can uniquely identify the communication devices 10 and 20. The oscillation wavelength represents the wavelength oscillated by the transmitting units 11 and 21 of the communication devices 10 and 20.

[0048] The zero-dispersion wavelength estimation table has multiple records representing information about the zero-dispersion wavelength for each connection path. The records in the zero-dispersion wavelength estimation table include fiber combinations and estimated zero-dispersion values. Fiber combinations represent combinations of optical transmission paths that constitute each connection path. In Figure 2(B), the fiber combinations shown are the combination of optical transmission paths f11+F1+f23, f11+F2+f23, f11+F3+f23, f21+F1+f13, f21+F2+f13, and f21+F3+f13. The estimated zero-dispersion value represents the estimated zero-dispersion wavelength for each connection path.

[0049] (System Operation Example) Next, an example of the operation of the optical communication system 100 will be described. Figures 3 and 4 are sequence diagrams showing the processing flow of the optical communication system 100 in the first embodiment. At the start of processing in Figures 3 and 4, ports 31-1 and 33 of the optical distribution unit 30 are connected, ports 41-1 and 43 of the optical distribution unit 40 are connected, and no values ​​are registered in the zero-dispersion wavelength estimation value table.

[0050] First, assume that the communication device 10 is connected to the optical distribution unit 30 via optical transmission paths f11 and f13 by the user (step S101). More specifically, assume that the transmitting unit 11 of the communication device 10 is connected to the optical distribution unit 30 via optical transmission path f11, and the receiving unit 12 of the communication device 10 is connected to the optical distribution unit 30 via optical transmission path f13. At this time, assume that the communication device 20 is already connected to the optical distribution unit 40 and registered in the user management table. Note that the communication device 20 may have already performed an initial connection in the same way as the communication device 10, not limited to the situation described above.

[0051] After connecting to the optical distribution unit 30, the communication device 10 generates an optical signal including a connection request and sends the generated optical signal to the optical transmission path f11. The connection request includes the identification information of the communication device 10 and the wavelength λ １ The information includes wavelength information indicating the device and information indicating the communication device 20. The optical signal transmitted from the communication device 10 is transferred to the control device 50 via the optical distribution unit 30. The communication unit 51 of the control device 50 receives the optical signal transmitted from the communication device 10. The communication unit 51 obtains a connection request from the received optical signal and outputs it to the control unit 53.

[0052] The user management unit 531 of the control unit 53 registers the combination of identification information and wavelength information included in the connection request output from the communication unit 51 in the user management table. The route control unit 534 understands that the communication device 10 will communicate with the communication device 20 based on the information indicating the communication device 20 included in the connection request. The route control unit 534 then assigns the upstream connection route for connecting the communication device 10 and the communication device 20 to the communication device 10 in a predetermined order (step S102). The predetermined order may be determined by any criteria.

[0053] The upstream connection paths assigned to the communication device 10 are three: a connection path consisting of a combination of optical transmission paths f11 + F1 + f23 (hereinafter referred to as the "first connection path"), a connection path consisting of a combination of optical transmission paths f11 + F2 + f23 (hereinafter referred to as the "second connection path"), and a connection path consisting of a combination of optical transmission paths f11 + F3 + f23 (hereinafter referred to as the "third connection path"). Here, the path control unit 534 assigns the first connection path to the communication device 10. The path control unit 534 controls the connection relationships between the ports of the optical distribution units 30 and 40 so that the connection is made using the first connection path assigned to the communication device 10 (step S103).

[0054] Specifically, the route control unit 534 generates route control information instructing the optical distribution unit 30 to connect port 31-1 and port 32-1, and notifies the optical distribution unit 30 of the generated route control information via a control line (not shown). The control line is an electrical line for transmitting electrical signals. Similarly, the route control unit 534 generates route control information instructing the optical distribution unit 40 to connect port 41-2 and port 42-1, and notifies the optical distribution unit 40 of the generated route control information via a control line (not shown).

[0055] The optical distribution unit 30 switches the connections between ports based on the route control information notified by the control device 50 (step S104). For example, the optical distribution unit 30 switches the connections between ports to connect port 31-1 and port 32-1. That is, the optical distribution unit 30 switches the connections between ports so that the optical signal sent from the transmission unit 11 of the communication device 10 is input to the optical distribution unit 40 via the optical transmission paths f11 and F1.

[0056] The optical distribution unit 40 switches the connections between ports based on the routing information notified by the control device 50 (step S105). For example, the optical distribution unit 40 switches the connections between ports to connect port 41-2 and port 42-1. That is, the optical distribution unit 40 switches the connections between ports so that the optical signal input via the optical transmission path F1 is input to the receiving unit 22 of the communication device 20 via the optical transmission path f23.

[0057] After the path control of the optical distribution units 30 and 40 is completed, the transmitting unit 11 of the communication device 10 transmits the wavelength λ １ A light signal is generated, and the generated wavelength λ １ The optical signal is sent to the optical transmission path f11 (step S106). The communication device 10 may be notified by the control device 50 via a control line that the routing control of the optical distribution units 30 and 40 is complete, or it may determine that the routing control of the optical distribution units 30 and 40 is complete after a predetermined time has elapsed. Wavelength λ sent from the communication device 10 １ The optical signal is input to port 31-1 of the optical distribution unit 30 via the optical transmission path f11.

[0058] The optical dispersion unit 30 receives the wavelength λ input to port 31-1. １ The optical signal is output from port 32-1 (step S107). The wavelength λ output from port 32-1 of the optical distribution unit 30 １ The optical signal is input to port 42-1 of the optical distribution unit 40 via the optical transmission path F1. The optical distribution unit 40 receives the wavelength λ input to port 42-1. １ The optical signal is output from port 41-2 (step S108). The wavelength λ output from port 41-2 of the optical distribution unit 40 １ The optical signal is input to the communication device 20 via the optical transmission path f23.

[0059] The receiving unit 22 of the communication device 20 receives the wavelength λ input via the optical transmission path f23. １ The receiving unit 22 receives the optical signal at the received wavelength λ (step S109). １ The optical signal is converted into an electrical signal. As a result, the receiving unit 22 receives the wavelength λ １ The device generates signal waveform data based on the optical signal. The transmission unit 21 of the communication device 20 generates an optical signal including the generated signal waveform data and sends the generated optical signal to the optical transmission path f21 (step S110).

[0060] The optical signal transmitted from the communication device 20 is input to port 41-1 of the optical distribution unit 40. The optical distribution unit 40 outputs the optical signal input to port 41-1 from port 43 (step S111). The communication unit 52 of the control device 50 receives the optical signal transmitted from the communication device 20. The communication unit 52 acquires signal waveform data from the received optical signal and outputs it to the control unit 53.

[0061] The estimation unit 532 estimates the zero-dispersion wavelength based on the acquired signal waveform data (step S112). For example, the estimation unit 532 estimates the zero-dispersion wavelength in the first connection path. Here, the zero-dispersion wavelength in the first connection path is λ ０（１，１，２） The estimation unit 532 determines the estimated zero-dispersion wavelength value λ. ０（１，１，２） The data is registered in the zero-dispersion wavelength estimation table, associated with the first connection path (step S113). For example, the estimation unit 532 registers the information of the first connection path (f11 + F1 + f23) in the fiber combination item of the zero-dispersion wavelength estimation table, and enters λ in the estimated zero-dispersion value item. ０（１，１，２） The information is registered. This registers the information shown in the first row of Figure 3 (B).

[0062] Subsequently, the communication device 10, the communication device 20, and the control device 50 perform the processes from step S102 to step S113 on other connection paths in the upstream direction (step S114). Here, the other connection paths in the upstream direction are the second connection path and the third connection path. When the processes from step S102 to step S113 are performed on other connection paths in the upstream direction, the control device 50 only needs to control the connections between the ports of the optical distribution units 30 and 40 so that the optical signals sent from the communication device 10 pass through the optical transmission paths F2 and F3. This makes it possible to perform the same processes as described above on other connection paths in the upstream direction.

[0063] Then, the estimation unit 532 estimates the zero-dispersion wavelength in the second connection path and the third connection path, respectively. Here, the zero-dispersion wavelength in the second connection path is λ ０（１，２，２） And the zero-dispersion wavelength in the third connection path is λ ０（１，３，２）The estimation unit 532 registers the zero-dispersion wavelength values ​​of each estimated connection path in the zero-dispersion wavelength estimation table, associating them with the second and third connection paths, respectively. For example, the estimation unit 532 registers the information of the second connection path (f11 + F2 + f23) in the fiber combination item of the zero-dispersion wavelength estimation table, and enters λ in the estimated zero-dispersion value item. ０（１，２，２） Register the information, register the information for the third connection path (f11 + F3 + f23) in the fiber combination item, and enter λ in the estimated zero variance item. ０（１，３，２） The information is registered. This registers the information shown in the second and third lines of Figure 3(B).

[0064] Next, the optical communication system 100 performs the same processing in the downstream direction as in steps S102 to S114 (step S115). An example of the processing in the downstream direction will be explained. The route control unit 534 assigns the downstream connection routes for connecting the communication device 10 and the communication device 20 to the communication device 20 in a predetermined order.

[0065] The downstream connection paths assigned to the communication device 20 are three: a connection path consisting of the combination of optical transmission paths f21 + F1 + f13 (hereinafter referred to as the "fourth connection path"), a connection path consisting of the combination of optical transmission paths f21 + F2 + f13 (hereinafter referred to as the "fifth connection path"), and a connection path consisting of the combination of optical transmission paths f21 + F3 + f13 (hereinafter referred to as the "sixth connection path"). Here, the path control unit 534 assigns the fourth connection path out of the three connection paths to the communication device 20. The path control unit 534 controls the connection relationships between the ports of the optical distribution units 30 and 40 so that the connection is made using the fourth connection path assigned to the communication device 20.

[0066] Specifically, the route control unit 534 generates route control information instructing the optical distribution unit 30 to connect port 32-1 and port 31-2, and to connect port 31-1 and port 33, and notifies the optical distribution unit 30 of the generated route control information via a control line (not shown). Similarly, the route control unit 534 generates route control information instructing the optical distribution unit 40 to connect port 41-1 and port 42-1, and notifies the optical distribution unit 40 of the generated route control information via a control line (not shown).

[0067] The optical distribution unit 40 switches the connections between ports based on the routing control information notified by the control device 50. For example, the optical distribution unit 40 switches the connections between ports to connect port 41-1 and port 42-1. That is, the optical distribution unit 40 switches the connections between ports so that the optical signal sent from the communication device 20 is input to the optical distribution unit 30 via the optical transmission paths f21 and F1.

[0068] The optical distribution unit 30 switches the connections between ports based on the routing control information notified by the control device 50. For example, the optical distribution unit 30 switches the connections between ports to connect port 31-2 and port 32-1, and port 31-1 and port 33. In this way, the optical distribution unit 30 switches the connections between ports so that the optical signal input via the optical transmission path F1 is input to the receiving unit 12 of the communication device 10 via the optical transmission path f13. The optical distribution unit 30 also switches the connections between ports to connect port 31-1 and port 33 so that the signal waveform data acquired by the communication device 10 can be transferred to the control device 50.

[0069] After the path control of the optical distribution units 30 and 40 is completed, the transmitting unit 21 of the communication device 20 transmits the wavelength λ ２ A light signal is generated, and the generated wavelength λ ２ The optical signal is sent to the optical transmission path f21. The communication device 20 may be notified by the control device 50 via a control line that the routing control of the optical distribution units 30 and 40 is complete, or it may determine that the routing control of the optical distribution units 30 and 40 is complete after a predetermined time has elapsed. Wavelength λ sent from the communication device 20 ２The optical signal is input to port 41-1 of the optical distribution unit 40 via the optical transmission path f21.

[0070] The optical distribution unit 40 receives the wavelength λ input to port 41-1. ２ The optical signal is output from port 42-1. The wavelength λ output from port 42-1 of the optical distribution unit 40 ２ The optical signal is input to port 32-1 of the optical distribution unit 30 via the optical transmission path F1. The optical distribution unit 30 receives the wavelength λ input to port 32-1. ２ The optical signal is output from port 31-2. The wavelength λ output from port 31-2 of the optical distribution unit 30 ２ The optical signal is input to the communication device 10 via the optical transmission path f13.

[0071] The receiving unit 12 of the communication device 10 receives the wavelength λ input via the optical transmission path f13. ２ The receiver 12 receives the optical signal at the received wavelength λ. ２ The optical signal is converted into an electrical signal. As a result, the receiving unit 12 receives the wavelength λ ２ The device generates signal waveform data based on the optical signal. The transmitting unit 11 of the communication device 10 generates an optical signal including the generated signal waveform data and sends the generated optical signal to the optical transmission path f 11.

[0072] The optical signal transmitted from the communication device 10 is input to port 31-1 of the optical distribution unit 30. The optical distribution unit 30 outputs the optical signal input to port 31-1 from port 33. The communication unit 51 of the control device 50 receives the optical signal transmitted from the communication device 10. The communication unit 51 acquires signal waveform data from the received optical signal and outputs it to the control unit 53.

[0073] The estimation unit 532 estimates the zero-dispersion wavelength based on the acquired signal waveform data. For example, the estimation unit 532 estimates the zero-dispersion wavelength in the fourth connection path. Here, the zero-dispersion wavelength in the fourth connection path is λ ０（２，１，１） The estimation unit 532 determines the estimated zero-dispersion wavelength value λ. ０（２，１，１）The data is then registered in the zero-dispersion wavelength estimation table, corresponding to the fourth connection path. For example, the estimation unit 532 registers the information of the fourth connection path (f21 + F1 + f13) in the fiber combination item of the zero-dispersion wavelength estimation table, and enters λ in the estimated zero-dispersion value item. ０（２，１，１） The information is registered. This registers the information shown in the fourth row of (B) in Figure 3.

[0074] Subsequently, the communication device 10, the communication device 20, and the control device 50 perform the same processing on other connection paths in the downstream direction. Here, the other connection paths in the downstream direction are the fifth connection path and the sixth connection path. When performing the same processing on other connection paths in the downstream direction, the control device 50 only needs to control the connections between the ports of the optical distribution units 30 and 40 so that the optical signals sent from the communication device 20 pass through the optical transmission paths F2 and F3. This makes it possible to perform the same processing as described above on other connection paths in the downstream direction.

[0075] Then, the estimation unit 532 estimates the zero-dispersion wavelength in the fifth connection path and the sixth connection path, respectively. Here, the zero-dispersion wavelength in the fifth connection path is λ ０（２，２，１） And the zero-dispersion wavelength in the sixth connection path is λ ０（２，３，１） The estimation unit 532 registers the zero-dispersion wavelength values ​​of each estimated connection path in the zero-dispersion wavelength estimation table, associating them with the fifth and sixth connection paths, respectively. For example, the estimation unit 532 registers the information for the fifth connection path (f21 + F2 + f13) in the fiber combination item of the zero-dispersion wavelength estimation table, and enters λ in the estimated zero-dispersion value item. ０（２，２，１） Register the information, register the information for the sixth connection path (f21 + F3 + f13) in the fiber combination item, and enter λ in the estimated zero variance item. ０（２，３，１） The information is registered. This registers the information shown in the 5th and 6th lines of Figure 3(B).

[0076] Subsequently, the route selection unit 533 selects the optimal connection route for each of the communication devices 10 and 20 based on the user management table and the zero-dispersion wavelength estimation table (step S116). Specifically, the route selection unit 533 refers to the user management table and the zero-dispersion wavelength estimation table and selects the oscillation wavelength (λ) for each of the communication devices 10 and 20. １ , λ ２ ) and the difference in absolute value between that and the estimated zero-dispersion wavelength value (estimated zero-dispersion value) are calculated.

[0077] The oscillation wavelength of the communication device 10 is λ １ Therefore, the value of the zero-dispersion wavelength (estimated zero-dispersion value) for each connection path in the upstream direction is λ ０（１，１，２） , λ ０（１，２，２） , λ ０（１，３，２） Therefore, the path selection unit 533 selects the oscillation wavelength λ. １ This is the absolute difference between the estimated zero-dispersion wavelength value (estimated zero-dispersion value) of each connection path in the upstream direction and │λ. １ -λ ０（１，１，２） │and, │λ １ -λ ０（１，２，２） │and, │λ １ -λ ０（１，３，２） Perform the calculation │. │λ １ -λ ０（１，１，２） The result of │ is "a", and │λ １ -λ ０（１，２，２） The result of │ is “b”, and │λ １ -λ ０（１，３，２） Let's assume the result of │ is "c".

[0078] The oscillation wavelength of the communication device 20 is λ ２ Therefore, the value of the zero-dispersion wavelength (estimated zero-dispersion value) for each connection path in the downstream direction is λ ０（２，１，１） , λ ０（２，２，１） , λ ０（２，３，１） Therefore, the path selection unit 533 selects the oscillation wavelength λ. ２ And the difference in absolute value between this and the estimated zero-dispersion wavelength (estimated zero-dispersion value) is │λ ２ -λ ０（２，１，１） │and, │λ ２ -λ ０（２，２，１） │and, │λ ２ -λ ０（２，３，１） Perform the calculation │. │λ ２ -λ ０（２，１，１）The result of │ is "d", and │λ ２ -λ ０（２，２，１） The result of │ is “e”, │λ ２ -λ ０（２，３，１） Let's assume the result of │ is "f".

[0079] Figure 5 shows the difference in absolute values ​​calculated for each communication device 10 and 20 by the route selection unit 533. The route selection unit 533 selects the connection route with the smallest difference in absolute values ​​for each communication device 10 and 20. Here, communication device 10 (oscillation wavelength λ １ For ), the difference in absolute value is smallest for "b", and the communication device 20 (oscillation wavelength λ ２ For this case, the smallest difference in absolute value is assumed to be "f". In this case, the route selection unit 533 selects the second connection route, where the difference in absolute value is "b", as the optimal connection route to use for uplink communication. The route selection unit 533 also selects the sixth connection route, where the difference in absolute value is "f", as the optimal connection route to use for downlink communication.

[0080] The route control unit 534 controls the connection relationships between the ports of the optical distribution units 30 and 40 so that they are connected via the connection paths selected by the route selection unit 533 (for example, the second connection path and the sixth connection path) (step S117). Specifically, the route control unit 534 generates route control information instructing the optical distribution unit 30 to connect port 31-1 and port 32-2, and port 31-2 and port 32-3, and notifies the optical distribution unit 30 of the generated route control information via a control line (not shown). Similarly, the route control unit 534 generates route control information instructing the optical distribution unit 40 to connect port 41-1 and port 42-3, and port 41-1 and port 42-2, and notifies the optical distribution unit 40 of the generated route control information via a control line (not shown).

[0081] The optical distribution unit 30 switches the connections between ports based on the route control information notified by the control device 50 (step S118). For example, the optical distribution unit 30 switches the connections between ports to connect port 31-1 and port 32-2, and port 31-2 and port 32-3. That is, the optical distribution unit 30 switches the connection path so that the optical signal sent from the transmission unit 11 of the communication device 10 is input to the optical distribution unit 40 via optical transmission lines f11 and F2, and switches the connections between ports so that the optical signal sent from the transmission unit 21 of the communication device 20 is input to the communication device 10 via optical transmission lines F3 and f13.

[0082] The optical distribution unit 40 switches the connections between ports based on the route control information notified by the control device 50 (step S119). For example, the optical distribution unit 40 switches the connections between ports to connect port 41-2 and port 42-2, and to connect port 41-1 and port 42-3 of the optical distribution unit 40. That is, the optical distribution unit 40 switches the connection path so that the optical signal sent from the transmission unit 21 of the communication device 20 is input to the optical distribution unit 30 via optical transmission lines f21 and F2, and switches the connections between ports so that the optical signal sent from the transmission unit 11 of the communication device 10 is input to the communication device 20 via optical transmission lines F3 and f23.

[0083] As a result of the processing from step S117 to step S119, the optical signal sent from the communication device 10 is transmitted to the communication device 20 via the optical transmission paths f11, F2, and f23, and the optical signal sent from the communication device 20 is transmitted to the communication device 10 via the optical transmission paths f21, F3, and f13. Subsequently, communication is initiated between the communication device 10 and the communication device 20 (step S120).

[0084] In the examples shown in Figures 3 and 4, the process involves estimating the zero-dispersion wavelength in one connection path and then estimating the zero-dispersion wavelength in other connection paths. However, the estimation of the zero-dispersion wavelength may be performed all at once after the signal waveform data for all connection paths has been obtained. In this configuration, the control device 50 controls each device to acquire signal waveform data for the first connection path, and then acquire signal waveform data for the other connection paths (for example, the second to sixth connection paths). The control device 50 then only needs to estimate the zero-dispersion wavelength for all connection paths after the signal waveform data for all connection paths has been obtained.

[0085] The timing for switching to another connection path may be after a predetermined time (for example, 10 seconds) has elapsed from the start time of path assignment, or the communication devices 10 and 20 may switch at a time interval known in advance, or they may communicate with the control device 50 by preparing a low-speed control channel, a different wavelength, or a different line control that is different from the main signal. In this case, it is possible for the communication devices 10 and 20 and the control device 50 to have functions for reading high speed, low speed, or waveform.

[0086] In Figures 3 and 4, the explanation was based on the example where no values ​​for any connection path are registered in the zero-dispersion wavelength estimation table. However, it is also possible that zero-dispersion wavelength values ​​are already registered in the zero-dispersion wavelength estimation table for some or all connection paths. In this case, the control device 50 does not need to estimate the zero-dispersion wavelength for connection paths where zero-dispersion wavelength values ​​are already registered, or it may re-estimate the zero-dispersion wavelength.

[0087] According to the optical communication system 100 configured as described above, the control device 50 includes a path selection unit 533 that acquires the value of the zero-dispersion wavelength in each of the multiple connection paths formed by a combination of multiple optical transmission paths connecting the communication device 10 and the communication device 20, and selects the optimal connection path from the multiple connection paths that satisfies the conditions for reducing the effects of wavelength dispersion based on the acquired zero-dispersion wavelength value, and a path control unit 534 that controls the path so that communication can be performed on the optimal path selected by the path selection unit 533.

[0088] As a result, even when communication devices 10 and 20 equipped with a single fixed-wavelength laser as a transmitting function are connected, a connection path with a zero-dispersion wavelength value close to the oscillation wavelength of the fixed-wavelength laser can be selected as the optimal path. Therefore, the transmission penalty due to wavelength dispersion can be reduced. Consequently, it becomes possible to extend the transmission distance of communication devices 10 and 20 equipped with a single fixed-wavelength laser as a transmitting function.

[0089] The control device 50 selects the connection path that has the smallest absolute difference between the oscillation wavelength of the communication devices 10 and 20 and the zero-dispersion wavelength in each connection path, as the optimal connection path that satisfies the conditions for reducing the effects of wavelength dispersion. The smaller the absolute difference between the oscillation wavelength of the communication devices 10 and 20 and the zero-dispersion wavelength in each connection path, the smaller the transmission penalty due to wavelength dispersion. Therefore, the transmission penalty due to wavelength dispersion can be reduced. As a result, it becomes possible to extend the transmission distance of the communication devices 10 and 20, which are equipped with a single fixed-wavelength laser as a transmission function.

[0090] (Second Embodiment) In the first embodiment, a configuration was shown in which the control device estimates the zero-dispersion wavelength. In the second embodiment, a configuration will be described in which the user-side communication device estimates the zero-dispersion wavelength.

[0091] Figure 6 shows an example configuration of the optical communication system 100a in the second embodiment. The optical communication system 100a comprises a communication device 10a, a communication device 20a, an optical distribution unit 30, an optical distribution unit 40, and a control device 50a. The optical communication system 100a differs from the first embodiment in that it includes communication devices 10a, 20a, and 50a instead of communication device 10, 20, and 50. The differences will be explained below in detail.

[0092] Communication devices 10a and 20a perform optical communication via optical distribution unit 30 and optical distribution unit 40. Communication devices 10a and 20a are located in geographically separated locations (for example, different bases). In the optical communication system 100a, although the reference numerals are different from those of the communication device 10, communication device 20 and control device 50 shown in the first embodiment (e.g., communication device 10a, communication device 20a and control device 50a), the relationship between the uplink and downlink directions and the connection relationships between the devices are the same as in the first embodiment.

[0093] The communication devices 10a and 20a perform the same processing as the communication devices 10 and 20 in the first embodiment, except that they are newly equipped with a function to estimate the zero-dispersion wavelength.

[0094] The control device 50a performs the same processing as the control device 50 in the first embodiment, except that it does not have a function to estimate the zero-dispersion wavelength.

[0095] Communication devices 10a and 20a estimate the zero-dispersion wavelength for each connection path. For example, communication device 10a estimates the zero-dispersion wavelength for each connection path in the upstream direction, and communication device 20a estimates the zero-dispersion wavelength for each connection path in the downstream direction. Communication devices 10a and 20a notify the control device 50a of the estimated zero-dispersion wavelength values ​​for each connection path. Based on the notified zero-dispersion wavelength values ​​for each connection path and the information registered in the user management table, the control device 50a selects the optimal connection path for connecting communication device 10a and communication device 20a in both the upstream and downstream directions. Then, the control device 50a controls the connection between the ports of the optical distribution units 30 and 40 so that communication device 10a and communication device 20a are connected via the selected optimal connection path.

[0096] (Example of the configuration of the communication device 10a) The communication device 10a comprises a transmitting unit 11, a receiving unit 12, and an estimation unit 13a. The communication device 10a differs from the communication device 10 in that it newly includes an estimation unit 13a. The estimation unit 13a estimates the value of the zero-dispersion wavelength for each connection path in the downstream direction. Specifically, the estimation unit 13a estimates the value of the zero-dispersion wavelength for each connection path in the downstream direction based on the optical signals transmitted in each connection path in the downstream direction. The estimation unit 13a may estimate the value of the zero-dispersion wavelength for each connection path in the downstream direction by an existing method (for example, the method described in Non-Patent Documents 1 and 2) or by other methods.

[0097] (Example of the configuration of the communication device 20a) The communication device 20a comprises a transmitting unit 21, a receiving unit 22, and an estimation unit 23a. The communication device 20a differs from the communication device 20 in that it newly includes an estimation unit 23a. The estimation unit 23a estimates the value of the zero-dispersion wavelength for each connection path in the uplink direction. Specifically, the estimation unit 23a estimates the value of the zero-dispersion wavelength for each connection path in the uplink direction based on the optical signals transmitted in each connection path in the uplink direction. The estimation unit 23a may estimate the value of the zero-dispersion wavelength for each connection path in the uplink direction by an existing method (for example, the method described in Non-Patent Documents 1 and 2) or by other methods.

[0098] (Example of configuration of control device 50a) The control device 50a comprises a communication unit 51, a communication unit 52, a control unit 53a, and a storage unit 54. The control device 50a differs from the control device 50 in that it has a control unit 53a instead of a control unit 53. The control unit 53a controls the entire control device 50a. The control unit 53a is configured using a processor such as a CPU and memory. The control unit 53a realizes the functions of the user management unit 531, the route selection unit 533, and the route control unit 534 by executing a program. Thus, the control unit 53a does not include an estimation unit 532.

[0099] When the zero-dispersion wavelength values ​​for each connection path are registered in the zero-dispersion wavelength estimation table, the route selection unit 533 selects the optimal connection path between the communication device 10a and the communication device 20a based on the zero-dispersion wavelength values ​​for each connection path and the information registered in the user management table. The method for selecting the optimal connection path is the same as in the first embodiment.

[0100] (System Operation Example) Next, an example of the operation of the optical communication system 100a will be described. Figures 7 and 8 are sequence diagrams showing the flow of processing performed by the optical communication system 100a in the second embodiment. At the start of processing in Figures 7 and 8, it is assumed that port 31-1 and port 33 of the optical distribution unit 30 are connected, port 41-1 and port 43 of the optical distribution unit 40 are connected, and no values ​​are registered in the zero-dispersion wavelength estimation value table. In Figures 7 and 8, the same processing as in Figures 3 and 4 is denoted by the same reference numerals as in Figures 3 and 4, and its explanation is omitted.

[0101] After the processing from step S101 to step S109 is completed, the estimation unit 23a acquires the signal waveform data generated by the receiving unit 22. Based on the acquired signal waveform data, the estimation unit 23a estimates the zero-dispersion wavelength (step S201). For example, the estimation unit 23a estimates the zero-dispersion wavelength in the first connection path. The transmission unit 21 generates an optical signal including the value of the zero-dispersion wavelength in the first connection path estimated by the estimation unit 23a, and sends the generated optical signal to the optical transmission path f21 (step S202).

[0102] The optical signal transmitted from the communication device 20a is input to port 41-1 of the optical distribution unit 40. The optical distribution unit 40 outputs the optical signal input to port 41-1 from port 43 (step S203). The communication unit 52 of the control device 50a receives the optical signal transmitted from the communication device 20a. The communication unit 52 obtains the zero-dispersion wavelength value from the received optical signal and outputs it to the control unit 53a.

[0103] The control unit 53a registers the acquired zero-dispersion wavelength value in the zero-dispersion wavelength estimation value table, associating it with the first connection path (step S204). Subsequently, the communication device 10a, the communication device 20a, and the control device 50a perform the processes from step S102 to step S204 on the other connection paths in the upstream direction (step S205). The other connection paths in the upstream direction are the second connection path and the third connection path. When the processes from step S102 to step S204 are performed on the other connection paths in the upstream direction, the control device 50a only needs to control the connection between the ports of the optical distribution units 30 and 40 so that the optical signal sent from the communication device 10a passes through the optical transmission paths F2 and F3. This makes it possible to perform the same processes as described above on the other connection paths in the upstream direction.

[0104] The estimation unit 23a estimates the zero-dispersion wavelengths for the second and third connection paths at different timings. For example, the estimation unit 23a estimates the zero-dispersion wavelength for the third connection path after it has estimated the zero-dispersion wavelength for the second connection path and notified the control device 50a. The transmission unit 21 of the communication device 20a notifies the control device 50a at different timings of the zero-dispersion wavelength values ​​for the other connection paths (the second and third connection paths) in the uplink direction estimated by the estimation unit 23a. As a result, the control device 50a registers the zero-dispersion wavelength values ​​for the other connection paths in the uplink direction notified by the communication device 20a in the zero-dispersion wavelength estimation value table, associating them with the second and third connection paths, respectively.

[0105] Next, the optical communication system 100a performs the same processing in the downstream direction as in steps S102 to S205 (step S206). An example of the processing in the downstream direction will be explained. The route control unit 534 assigns the downstream connection routes for connecting the communication device 10a and the communication device 20a to the communication device 20a in a predetermined order.

[0106] The connection paths in the downstream direction assigned to the communication device 20a are three: the fourth connection path, the fifth connection path, and the sixth connection path. Here, assuming that the path control unit 534 assigns the fourth connection path to the communication device 20a among the three connection paths, the path control unit 534 controls the connection relationship between the ports of the optical oscillator units 30 and 40 so as to connect via the fourth connection path assigned to the communication device 20a. Since this process has also been described in the first embodiment, the description is omitted.

[0107] After the path control of the optical oscillator units 30 and 40 is completed, the transmission unit 21 of the communication device 20a ２ generates an optical signal with a wavelength of λ ２ and sends the generated optical signal with a wavelength of λ ２ to the optical transmission line f21. The communication device 20a may be notified from the control device 50a via the control line that the path control of the optical oscillator units 30 and 40 has been completed, or may determine that the path control of the optical oscillator units 30 and 40 has been completed when a predetermined time has elapsed. The optical signal with a wavelength of λ ２ sent from the communication device 20a is input to the port 41-1 of the optical oscillator unit 40 via the optical transmission line f21.

[0108] The optical oscillator unit 40 outputs the optical signal with a wavelength of λ ２ input to the port 41-1 from the port 42-1. The optical signal with a wavelength of λ 6 ２ output from the port 42-1 of the optical oscillator unit 40 is input to the port 32-1 of the optical oscillator unit 30 via the optical transmission line F1. The optical oscillator unit 30 outputs the optical signal with a wavelength of λ <000009> ２ input to the port 32-1 from the port 31-2. The optical signal with a wavelength of λ ２ output from the port 31-2 of the optical oscillator unit 30 is input to the communication device 10a via the optical transmission line f13.

[0109] The receiving unit 12 of the communication device 10a receives the optical signal with a wavelength of λ ２ input via the optical transmission line f13. The receiving unit 12 converts the received optical signal with a wavelength of λ <000009>[ ２ into an electrical signal. Thereby, the receiving unit 12 receives the optical signal with a wavelength of λ <... ２The system generates signal waveform data based on the optical signal. The estimation unit 13a acquires the signal waveform data generated by the receiving unit 12. The estimation unit 13a estimates the zero-dispersion wavelength based on the acquired signal waveform data. For example, the estimation unit 13a estimates the zero-dispersion wavelength in the fourth connection path. The transmission unit 21 generates an optical signal including the value of the zero-dispersion wavelength in the fourth connection path estimated by the estimation unit 13a, and sends the generated optical signal to the optical transmission path f13.

[0110] The optical signal transmitted from the communication device 10a is input to port 31-2 of the optical distribution unit 30. The optical distribution unit 30 outputs the optical signal input to port 31-2 from port 33. The communication unit 51 of the control device 50a receives the optical signal transmitted from the communication device 10a. The communication unit 51 obtains the zero-dispersion wavelength value from the received optical signal and outputs it to the control unit 53a.

[0111] The control unit 53a registers the acquired zero-dispersion wavelength value in the zero-dispersion wavelength estimation table, associating it with the fourth connection path. Subsequently, the communication device 10a, the communication device 20a, and the control device 50a perform the same processing for the other connection paths in the downstream direction. Here, the other connection paths in the downstream direction are the fifth connection path and the sixth connection path. When performing the same processing for the other connection paths in the downstream direction, the control device 50a only needs to control the connection between the ports of the optical distribution units 30 and 40 so that the optical signal sent from the communication device 20a passes through the optical transmission paths F2 and F3. This makes it possible to perform the same processing as described above for the other connection paths in the downstream direction.

[0112] The estimation unit 13a estimates the zero-dispersion wavelengths for the fifth and sixth connection paths at different timings. For example, the estimation unit 13a estimates the zero-dispersion wavelength for the sixth connection path after it has estimated the zero-dispersion wavelength for the fifth connection path and notified the control device 50a. The transmission unit 11 notifies the control device 50a of the zero-dispersion wavelength values ​​for the other connection paths in the downstream direction (the fifth and sixth connection paths) estimated by the estimation unit 13a. As a result, the control device 50a registers the zero-dispersion wavelength values ​​for the other connection paths in the downstream direction notified by the communication device 10a in the zero-dispersion wavelength estimation value table, associating them with the fifth and sixth connection paths, respectively. After that, the processing in step S116 is executed.

[0113] In the examples shown in Figures 7 and 8, the process is shown in which communication devices 10a and 20a estimate the zero-dispersion wavelength for one connection path and then estimate the zero-dispersion wavelength for the other connection paths. However, the estimation of the zero-dispersion wavelength performed by communication devices 10a and 20a may be performed collectively after the signal waveform data for each connection path in the relevant direction has been obtained. For example, communication device 10a may estimate the zero-dispersion wavelength collectively after the signal waveform data for all connection paths in the uplink direction has been obtained, and communication device 20a may estimate the zero-dispersion wavelength collectively after the signal waveform data for all connection paths in the downlink direction has been obtained. In this configuration, the control device 50a controls each device so that the estimation of the zero-dispersion wavelength for the other connection paths (for example, the second to sixth connection paths) is performed after the estimation of the zero-dispersion wavelength for the first connection path has been performed.

[0114] The timing for switching to another connection path may be a predetermined time (for example, 10 seconds) elapsed from the start time of step S102, or the communication devices 10a and 20a may switch at a predetermined time interval, or they may communicate with the control device 50a by preparing a low-speed control channel, a different wavelength, or a different line control that is different from the main signal. In this case, it is possible for the communication devices 10a and 20a and the control device 50a to have functions for reading high speed, low speed, or waveform.

[0115] With the optical communication system 100a configured as described above, the same effects as in the first embodiment can be obtained even when the communication devices 10a and 20a, which are user-side devices, are configured to estimate the zero-dispersion wavelength of each connection path.

[0116] (Third Embodiment) In the first and second embodiments, the zero-dispersion wavelength in the connection path between communication devices was estimated when selecting a connection path. As an alternative method for selecting a connection path, the zero-dispersion wavelength can be estimated in the intermediate path between communication devices, and the connection path can be selected based on the estimation result. In the third embodiment, a configuration is described in which the zero-dispersion wavelength is estimated in the intermediate path between communication devices to select the optimal connection path.

[0117] Figure 9 shows an example configuration of the optical communication system 100b in the third embodiment. The optical communication system 100b comprises a communication device 10, a communication device 20, an optical distribution unit 30, an optical distribution unit 40, and a control device 50b. The optical communication system 100b differs from the first embodiment in that it includes a control device 50b instead of a control device 50. The differences will be explained below in detail.

[0118] In the optical communication system 100b, although the reference numerals are different from those of the control device 50 shown in the first embodiment, such as control device 50b, the relationship between the uplink and downlink directions and the connection relationships between devices are the same as in the first embodiment.

[0119] The control device 50b is a device that controls the entire optical communication system 100b. The control device 50b does not estimate the zero-dispersion wavelength in the connection path between the communication device 10 and the communication device 20, but rather estimates the zero-dispersion wavelength in an intermediate path. Here, an intermediate path is a path other than the path connecting the communication device 10 to the communication device 20 (end-to-end path). Examples of intermediate paths include the optical transmission path connecting the communication device 10 and the optical distribution unit 30, a combination of optical transmission paths connecting the communication device 10, the optical distribution unit 30 and the optical distribution unit 40, the optical transmission path connecting the communication device 20 and the optical distribution unit 40, and a combination of optical transmission paths connecting the communication device 20, the optical distribution unit 40 and the optical distribution unit 30.

[0120] Furthermore, the control device 50b holds a transmission path table. The transmission path table is a table in which information about optical fibers is listed. Information about the optical fibers connecting between optical oscillator sections (for example, between the optical oscillator section 30 and the optical oscillator section 40) is registered in the transmission path table. For example, in the transmission path table, data of a combination of the value of the zero-dispersion wavelength, the distance L, and the dispersion slope S ０ or data of a combination of the value of the zero-dispersion wavelength and the distance L×dispersion slope S ０ is registered for each of the optical transmission paths F1, F2, and F3. Note that, in the transmission path table, the above information is registered for the number of optical transmission paths connecting between optical oscillator sections.

[0121] Based on the estimated result of the zero-dispersion wavelength in the above-mentioned intermediate path and the transmission path table, the control device 50b estimates the zero-dispersion wavelength for each connection path and registers the value of the zero-dispersion wavelength for each estimated connection path in the zero-dispersion wavelength estimated value table. Based on the value of the zero-dispersion wavelength registered in the zero-dispersion wavelength estimated value table and the information registered in the user management table, the control device 50b selects an optimal connection path for connecting between the communication device 10 and the communication device 20 in the upstream direction and the downstream direction, respectively. Then, the control device 50b controls the connection between the ports of the optical oscillator sections 30 and 40 so as to connect the communication device 10 and the communication device 20 through the selected connection path. Thus, the control device 50b is the same as the control device 50 in the first embodiment except for the method of estimating the zero-dispersion wavelength of each connection path.

[0122] (Configuration example of the control device 50b) The control device 50b includes a communication unit 51, a communication unit 52, a control unit 53b, and a storage unit 54b. The control unit 53b controls the entire control device 50b. The control unit 53b is configured using a processor such as a CPU and a memory. By executing a program, the control unit 53b realizes the functions of a user management unit 531b, an estimation unit 532b, a path selection unit 533, and a path control unit 534.

[0123] The user management unit 531b manages information on communication devices 10 and 20, which are users of the optical communication system 100. Furthermore, the user management unit 531b controls the communication units 51 and 52 to transmit optical signals of specific wavelengths. This is to obtain signal waveform data necessary for estimating the zero-dispersion wavelength in some paths.

[0124] The estimation unit 532b estimates the zero-dispersion wavelength value for each connection path. Specifically, the estimation unit 532b first estimates the zero-dispersion wavelength value for each intermediate path. For example, the estimation unit 532b estimates the zero-dispersion wavelength value for optical transmission path f11, optical transmission path f21, optical transmission path f13, and optical transmission path f23. Next, the estimation unit 532b estimates the zero-dispersion wavelength value for each connection path based on the estimated zero-dispersion wavelength values ​​for each intermediate path and the transmission path table.

[0125] The storage unit 54b stores a user management table, a zero-dispersion wavelength estimation table, and a transmission path table. The storage unit 54b is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device.

[0126] Figure 10 shows an example of a transmission path table in the third embodiment. The transmission path table has multiple records representing information about the optical fiber. The records in the transmission path table shown in Figure 10(A) are the fiber, the zero-dispersion wavelength value, the distance L, and the dispersion slope S. ０ It has the value of . Fibers represent optical transmission paths that directly connect devices. In Figure 10 (A), optical transmission paths F1, F2, and F3 are shown as fibers. The zero-dispersion wavelength value represents the zero-dispersion wavelength value of the optical fiber that is each associated optical transmission path. Distance L represents the length of the optical fiber that is each associated optical transmission path. Dispersion slope S ０ This represents the distributed slope of each optical fiber, which is the corresponding optical transmission path.

[0127] Furthermore, the records in the transmission path table shown in Figure 10(B) include the fiber, the zero-dispersion wavelength value, and the distance L × dispersion slope S. ０It has the value of . Fiber represents an optical transmission path that directly connects devices. The zero-dispersion wavelength value represents the zero-dispersion wavelength value of the optical fiber, which is the corresponding optical transmission path. Distance L × Dispersion Slope S ０ This represents the product of the length (distance) of each associated optical transmission path (optical fiber) and the dispersion slope of the optical fiber.

[0128] (System Operation Example) Next, an example of the operation of the optical communication system 100b will be described. Figures 11 and 12 are sequence diagrams showing the flow of processing performed by the optical communication system 100b in the third embodiment. At the start of processing in Figures 11 and 12, it is assumed that port 31-1 and port 33 of the optical distribution unit 30 are connected, and port 41-1 and port 43 of the optical distribution unit 40 are connected. In Figures 11 and 12, the same processing as in Figures 3 and 4 is denoted by the same reference numerals as in Figures 3 and 4, and its explanation is omitted.

[0129] In step S101, after the communication device 10 is connected to the optical distribution unit 30, the transmitting unit 11 of the communication device 10 transmits the wavelength λ １ A light signal is generated, and the generated wavelength λ １ The optical signal is sent to the optical transmission path f11 (step S301). The wavelength λ sent from the communication device 10 １ The optical signal is input to port 31-1 of the optical distribution unit 30 via the optical transmission path f11.

[0130] The optical dispersion unit 30 receives the wavelength λ input to port 31-1. １ The optical signal is output from port 33 (step S302). The wavelength λ output from port 33 of the optical distribution unit 30 １ The optical signal is input to the control device 50b via the optical transmission path. In this third embodiment, the optical signal sent from the communication device 10 is input to the control device 50b as shown by path R1 so that the control device 50b can estimate the zero-dispersion wavelength along the intermediate path.

[0131] The communication unit 51 of the control device 50b receives the wavelength λ input via the optical transmission path. １ The optical signal is received (step S303). The communication unit 51 receives the wavelength λ １The optical signal is converted into an electrical signal. As a result, the communication unit 51 receives the wavelength λ １ The system generates signal waveform data based on the optical signal. The communication unit 51 outputs the generated signal waveform data to the control unit 53b. The estimation unit 532b estimates the zero-dispersion wavelength based on the signal waveform data output from the communication unit 51 (step S304). For example, the estimation unit 532b estimates the zero-dispersion wavelength in the optical transmission path f11. Here, the zero-dispersion wavelength λ in the optical transmission path f11 is... ０ to λ ０ Let the values ​​be (1, 0, 0).

[0132] Subsequently, the user management unit 531b controls the communication unit 52 to estimate the zero-dispersion wavelength in the optical transmission path f23 connecting the receiving unit 22 of the communication device 20, which is the communication partner of the communication device 10, and the optical distribution unit 40, by setting the wavelength λ ａ The communication unit 52 transmits an optical signal at wavelength λ according to the control of the user management unit 531b. ａ The optical signal is sent to the optical transmission path (step S305). The wavelength λ sent from the communication unit 52 ａ The optical signal is input to port 43 of optical distribution unit 40 via an optical transmission path.

[0133] The optical dispersion unit 40 receives the wavelength λ input to the port 43. ａ The optical signal is output from port 41-2 (step S306). The wavelength λ output from port 41-2 of the optical distribution unit 40 ａ The optical signal is input to the communication device 20 via the optical transmission path f23. In this third embodiment, the optical signal sent from the control device 50b is input to the communication device 20 in such a way as shown by path R2, so that the control device 50b can estimate the zero-dispersion wavelength along the intermediate path.

[0134] The receiving unit 22 of the communication device 20 receives the wavelength λ input via the optical transmission path f23. ａ The receiving unit 22 receives the optical signal at the received wavelength λ (step S307). ａ The optical signal is converted into an electrical signal. As a result, the receiving unit 22 receives the wavelength λ ａThe optical signal generates signal waveform data. The transmitting unit 21 of the communication device 20 generates an optical signal including the generated signal waveform data and sends the generated optical signal to the optical transmission path f21 (step S308). As a result, the optical signal sent from the communication device 20 is input to port 41-1 of the optical distribution unit 40.

[0135] The path control unit 534 of the control device 50b controls the wavelength λ of the communication unit 52 so that the optical signal transmitted from the communication device 20 is output from port 43 via port 41-1 of the optical distribution unit 40. ａ After the optical signal is transmitted, the connection between the ports of the optical distribution unit 40 should be controlled. As a result, the optical distribution unit 40 outputs the optical signal input to port 41-1 from port 43 (step S309). The communication unit 52 of the control device 50b receives the optical signal sent from the communication device 20. The communication unit 52 acquires signal waveform data from the received optical signal and outputs it to the control unit 53b.

[0136] The estimation unit 532b estimates the zero-dispersion wavelength based on the acquired signal waveform data (step S112). For example, the estimation unit 532b estimates the zero-dispersion wavelength in the optical transmission path f23. Here, the zero-dispersion wavelength λ in the optical transmission path f23 ０ to λ ０ Let (0,0,2). The above is the process for estimating the zero-dispersion wavelength along the path in the uplink direction. Next, in the optical communication system 100b, the same process as in steps S301 to S310 is performed when the communication device 20 transmits an optical signal (step S311). This corresponds to the process for estimating the zero-dispersion wavelength along the path in the downlink direction. An example will be given below when the communication device 20 transmits an optical signal.

[0137] As a prerequisite for this processing, the route control unit 534 generates route control information instructing the optical distribution unit 30 to connect port 31-2 and port 33, and notifies the optical distribution unit 30 of the generated route control information via a control line (not shown). Similarly, the route control unit 534 generates route control information instructing the optical distribution unit 40 to connect port 41-1 and port 43, and notifies the optical distribution unit 40 of the generated route control information via a control line (not shown).

[0138] The optical distribution unit 40 switches the connections between ports based on the routing information notified by the control device 50b. For example, the optical distribution unit 40 switches the connections between ports to connect port 41-1 and port 43. That is, the optical distribution unit 40 switches the connections between ports so that the optical signal input via the optical transmission path f21 is input to the control device 50b via the optical transmission path.

[0139] The optical distribution unit 30 switches the connections between ports based on the routing control information notified by the control device 50b. For example, the optical distribution unit 30 switches the connections between ports to connect port 31-2 and port 33. That is, the optical distribution unit 30 switches the connections between ports so that the optical signal sent from the control device 50b is input to the receiving unit 12 of the communication device 10 via the optical transmission path f13.

[0140] After the path control of the optical distribution units 30 and 40 is completed, the transmitting unit 21 of the communication device 20 transmits the wavelength λ ２ A light signal is generated, and the generated wavelength λ ２ The optical signal is sent to the optical transmission path f21. The communication device 20 may be notified by the control device 50b via a control line that the routing control of the optical distribution units 30 and 40 is complete, or it may determine that the routing control of the optical distribution units 30 and 40 is complete after a predetermined time has elapsed. Wavelength λ sent from the communication device 20 ２ The optical signal is input to port 41-1 of the optical distribution unit 40 via the optical transmission path f21.

[0141] The optical distribution unit 40 receives the wavelength λ input to port 41-1. ２ The optical signal is output from port 43. The wavelength λ output from port 43 of the optical distribution unit 40 ２ The optical signal is input to the control device 50b via the optical transmission path. The communication unit 52 of the control device 50b receives the wavelength λ input via the optical transmission path. ２ The communication unit 52 receives an optical signal of the received wavelength λ. ２ The optical signal is converted into an electrical signal. As a result, the communication unit 52 receives the wavelength λ ２The system generates signal waveform data based on the optical signal. The communication unit 52 outputs the generated signal waveform data to the control unit 53b. The estimation unit 532b estimates the zero-dispersion wavelength based on the signal waveform data output from the communication unit 52. For example, the estimation unit 532b estimates the zero-dispersion wavelength in the optical transmission path f21. Here, the zero-dispersion wavelength λ in the optical transmission path f21 is... ０ to λ ０ Let (2, 0, 0).

[0142] Subsequently, the user management unit 531b controls the communication unit 51 to estimate the zero-dispersion wavelength in the optical transmission path f13 connecting the receiving unit 12 of the communication device 10, which is the communication partner of the communication device 20, and the optical distribution unit 30, by setting the wavelength λ ａ The communication unit 51 transmits an optical signal at wavelength λ according to the control of the user management unit 531b. ａ The optical signal is sent to the optical transmission path. The wavelength λ is transmitted from the communication unit 51. ａ The optical signal is input to port 33 of optical distribution unit 30 via an optical transmission path.

[0143] The optical dispersion unit 30 receives the wavelength λ input to the port 33. ａ The optical signal is output from port 31-2. The wavelength λ output from port 31-2 of the optical distribution unit 30 ａ The optical signal is input to the communication device 10 via the optical transmission path f13. The receiving unit 12 of the communication device 10 receives the wavelength λ input via the optical transmission path f13. ａ The receiver 12 receives the optical signal at the received wavelength λ. ａ The optical signal is converted into an electrical signal. As a result, the receiving unit 12 receives the wavelength λ ａ The device generates signal waveform data based on the optical signal. The transmitting unit 11 of the communication device 10 generates an optical signal including the generated signal waveform data and sends the generated optical signal to the optical transmission path f 11. As a result, the optical signal sent from the communication device 10 is input to port 31-1 of the optical distribution unit 30.

[0144] The path control unit 534 of the control device 50b controls the wavelength λ of the communication unit 51 so that the optical signal transmitted from the communication device 10 is output from port 33 via port 31-1 of the optical distribution unit 30. ａAfter the optical signal is transmitted, the connection between the ports of the optical distribution unit 30 should be controlled. As a result, the optical distribution unit 30 outputs the optical signal input to port 31-1 from port 33. The communication unit 51 of the control device 50b receives the optical signal sent from the communication device 10. The communication unit 51 acquires signal waveform data from the received optical signal and outputs it to the control unit 53b.

[0145] The estimation unit 532b estimates the zero-dispersion wavelength based on the acquired signal waveform data. For example, the estimation unit 532b estimates the zero-dispersion wavelength in the optical transmission path f13. Here, the zero-dispersion wavelength λ in the optical transmission path f13 is... ０ to λ ０ Let (0,0,1). The above is the process for estimating the zero-dispersion wavelength for intermediate paths in the downstream direction. Subsequently, the estimation unit 532b estimates the zero-dispersion wavelength for each connection path based on the zero-dispersion wavelength values ​​for each intermediate path obtained by the above process and the transmission path table (step S312).

[0146] The method for estimating the zero-dispersion wavelength for each connection path in the third embodiment will be described. First, the estimation unit 532b calculates the distance L × dispersion slope S for each of the optical transmission paths f11, f13, f21, and f23. ０ The value of is calculated based on the following formula (1).

[0147]

[0148] λ in equation (1) ｉ , f ｎｉ , α ｉ i is the zero-dispersion wavelength λ ０ The wavelength λ used in the estimation ｉ It represents a value corresponding to the wavelength λ. ａ When using this, i = a, and f ｎａ , α ａ This is the result. Note that in equation (1), f ｎｉ wavelength λ ｉ Based on the frequency spectrum of the optical signal, α represents the notch frequency at which a notch appears at a frequency other than a multiple of the optical signal. ｉ represents the previously determined chirp value. Note that n is a non-negative integer. Furthermore, the "±" before the expression (1+2n) in equation (1) is based on the following conditions.

[0149] wavelength λ ０ However, wavelength λ ｉ Smaller than, and S ０ L is greater than 0 (for example, λ ０ <λ ｉ and 0 < S ０ The result is "+" if the condition L is met. On the other hand, wavelength λ ０ However, wavelength λ ｉ Larger than, and S ０ L is greater than 0 (for example, λ ０ >λ ｉ and 0 < S ０ If the condition L is met, the result will be "-". Note that in systems where the upper limit of distance L is fixed, the fixed upper limit L will be used. ｍａｘ Use [km] ０ L < 0.092L ｍａｘ The condition (i.e., 0 < S) ０ L < 0.092L ｍａｘ ) is added to the above conditions. For example, if it is less than 100 km, S ０ The condition L < 9.2 is added to each of the above conditions. For example, the upper limit of distance L can be determined based on the requirements of the transceiver used and the maximum transmission distance expected in the network configuration. Note that this is just one example, and the upper limit of distance L may be determined by other methods.

[0150] The estimation unit 532b uses the wavelength λ ０ If the value of is outside the zero-dispersion wavelength range (for example, wavelengths 1300-1324 nm for a standard single-mode fiber), then the wavelength λ is outside the zero-dispersion wavelength range. ０ The value of λ is excluded from the list of zero-dispersion wavelength candidates. ０ In other embodiments, it is also the case that values ​​outside the range of zero-dispersion wavelengths are excluded. The zero-dispersion wavelength values ​​in optical transmission paths f11, f13, f21, and f23, respectively, and distance L × dispersion slope S ０ The relationship with the value is shown in Figure 13.

[0151] Furthermore, the estimation unit 532b calculates the chromatic dispersion amount (= chromatic dispersion D × distance L) for each of the optical transmission paths f11, f13, f21, and f23. Then, the estimation unit 532b calculates the zero-dispersion wavelength value for each of the optical transmission paths f11, f13, f21, and f23, and the distance L × dispersion slope S for each of the optical transmission paths f11, f13, f21, and f23. ０ Based on the values ​​of , the chromatic dispersion amounts in optical transmission paths f11, f13, f21, and f23, and the transmission path table, the zero-dispersion wavelength for each connection path is estimated.

[0152] For example, the estimation unit 532b determines the zero-dispersion wavelength λ in the first connection path. ０（１，１，２） This is calculated based on the relationship shown in equation (2) below.

[0153]

[0154] Furthermore, the estimation unit 532b also estimates the zero-dispersion wavelength for each connection path using values ​​corresponding to each optical transmission path that constitutes the connection path. The estimation results for the zero-dispersion wavelength for each connection path are shown in Figure 14. Subsequently, the processing from step S119 onward is executed.

[0155] In the process described above, an example was shown using path R2 as a method for estimating the zero-dispersion wavelength in the optical transmission path f23, but other paths may be used. Another path is, for example, a path in which an optical signal sent from the transmitting unit 21 of the communication device 20 is input to the optical distribution unit 40 via the optical transmission path f21, and the optical signal is folded back in the optical distribution unit 40 and input to the receiving unit 22 of the communication device 20 via the optical transmission path f23. In this case, the values ​​corresponding to the combination of optical transmission paths f21 + f23 in Figure 14 and the value of optical transmission path f21 in Figure 13 can be determined in the same way.

[0156] With the optical communication system 100b configured as described above, the same effects as in the first embodiment can be obtained even when the zero-dispersion wavelength of each connection path is estimated using the results of estimating the zero-dispersion wavelength in the intermediate path.

[0157] (Modification 1) The intermediate path in the third embodiment is not limited to the path shown in the embodiment. For example, the intermediate path may be a path composed of optical transmission path f11 + F1 or a path composed of optical transmission path F2 + f23, which passes through the optical distribution units 30 and 40. In this case, the control device 50b determines the value of the zero-dispersion wavelength and the distance L × dispersion slope S in the path composed of each combination of optical transmission path f11 + F1, f12 + F2, f21 + f23... ０ The value of [the product of the zero-dispersion wavelength and the wavelength dispersion amount DL] is needed. For example, when estimating the zero-dispersion wavelength in the connection path of optical transmission lines f11 + F1 + f23, the control device 50b can estimate the zero-dispersion wavelength in the connection path of optical transmission lines f11 + F1 + f23 by estimating the zero-dispersion wavelength in the path R3 composed of optical transmission lines f11 + F1 and the zero-dispersion wavelength in the path of optical transmission line f23. Also, for example, when estimating the zero-dispersion wavelength in the connection path of optical transmission lines f11 + F2 + f23, the control device 50b can estimate the zero-dispersion wavelength in the connection path of optical transmission lines f11 + F2 + f23 by estimating the zero-dispersion wavelength in the path of optical transmission line f11 and the zero-dispersion wavelength in the path R4 composed of optical transmission lines F2 + f23. In this case, the control device 50b only needs to know the value of the product of the zero-dispersion wavelength and the wavelength dispersion amount DL for each of the optical transmission lines F1, F2, and F3. Furthermore, when determining the zero-dispersion wavelength along the optical transmission path f23, the control device 50b can estimate it by using the product of the zero-dispersion wavelength for the optical transmission path F2 and the wavelength dispersion amount DL.

[0158] (Modification 2) In the above-described embodiment, the control device 50b is shown to hold the transmission path table, but the transmission path table may be held by each communication device 10, 20. In this case, each communication device 10, 20 performs the same processing as the control device 50b.

[0159] (Fourth Embodiment) The first to third embodiments described a configuration based on zero-dispersion wavelength as a method for selecting the optimal connection path. The fourth embodiment describes a configuration for selecting the optimal connection path based on a value other than the zero-dispersion wavelength. For example, the fourth embodiment describes a configuration for selecting the optimal connection path based on the notch frequency value. The process in the fourth embodiment is applicable to any of the first to third embodiments, but the first embodiment will be used as an example here.

[0160] When selecting the optimal connection path based on the notch frequency value, the storage unit 54 of the control device 50 stores the notch frequency table shown in Figure 15 instead of the zero-dispersion wavelength estimation table. Figure 15 is a diagram showing an example of a notch frequency table in the fourth embodiment. The notch frequency table has multiple records representing information about the notch frequency for each connection path. The records in the notch frequency table have fiber combinations and notch frequency values. The fiber combination represents a combination of multiple optical transmission paths that constitute the connection path. The notch frequency represents the notch frequency value for each connection path.

[0161] Unlike the estimation unit 532 in the first embodiment, the estimation unit 532 does not estimate the zero-dispersion wavelength value for each connection path, but instead acquires the notch frequency based on the signal waveform data obtained for each connection path. The notch frequency is an example of information related to the optical transmission path. As a result, the estimation unit 532 acquires the notch frequency for each connection path. The estimation unit 532 registers the acquired notch frequency values ​​in the notch frequency table for each connection path.

[0162] The route selection unit 533 selects the optimal connection path from among multiple connection paths that satisfies the conditions for reducing the effects of wavelength dispersion, based on the notch frequency values ​​registered in the notch frequency table. Specifically, the route selection unit 533 selects the connection path with the largest notch frequency value among the notch frequency values ​​of each connection path as the optimal connection path for each communication device 10, 20. For example, the route selection unit 533 selects the connection path with the largest notch frequency value among the notch frequency values ​​of each connection path in the uplink direction as the optimal connection path in the uplink direction (optimal path for communication device 10), and selects the connection path with the largest notch frequency value among the notch frequency values ​​of each connection path in the downlink direction as the optimal connection path in the downlink direction (optimal path for communication device 20).

[0163] (System Operation Example) Next, an example of the operation of the optical communication system 100 in the fourth embodiment will be described. The basic processing flow is the same as in Figures 3 and 4, so it will be explained using Figures 3 and 4. When the processing from step S101 to step S111 is completed, in step S112, the estimation unit 532 obtains the notch frequency based on the acquired signal waveform data. For example, the estimation unit 532 obtains the notch frequency at which the first notch appears at a frequency other than a multiple of the transmission signal frequency (1x, 2x, etc.) based on the acquired signal waveform data.

[0164] As a result, the estimation unit 532 obtains the notch frequency in the first connection path. Here, the notch frequency in the first connection path is f ０（１，１，２） In step S113, the estimation unit 532 determines the acquired notch frequency value f ０（１，１，２） The first connection path is associated with the notch frequency table and registered. For example, the estimation unit 532 registers the information of the first connection path (f11 + F1 + f23) in the fiber combination item of the notch frequency table, and the notch frequency item f ０（１，１，２） The information is registered. This registers the information shown in the first row of Figure 15.

[0165] Subsequently, in step S114, the communication device 10, the communication device 20, and the control device 50 perform the same process as the process for acquiring the notch frequency in the first connection path in the other connection paths in the upstream direction. Here, the other connection paths in the upstream direction are the second connection path and the third connection path. As a result, the estimation unit 532 acquires the notch frequency in the second connection path and the third connection path, respectively. Here, the notch frequency in the second connection path is f ０（１，２，２） Let the notch frequency in the third connection path be f. ０（１，３，２） Let's assume that.

[0166] The estimation unit 532 determines the notch frequency value f of each connection path that it has estimated. ０（１，２，２） and f ０（１，３，２） The second connection path and the third connection path are registered in the notch frequency table, respectively. For example, the estimation unit 532 registers the information of the second connection path (f11 + F2 + f23) in the fiber combination item of the notch frequency table, and the notch frequency item f ０（１，２，２） Register the information, register the information for the third connection path (f11 + F3 + f23) in the fiber combination item, and enter the notch frequency item f ０（１，３，２） The information is registered. This registers the information shown in the second and third lines of Figure 15.

[0167] Next, in step S115, the optical communication system 100 performs the same processing in the downstream direction as in the upstream direction. The processing in the downstream direction is basically the same as the processing described in the first embodiment. The difference from the first embodiment is that the estimation unit 532 acquires the notch frequency based on the signal waveform data acquired in each connection path in the downstream direction.

[0168] As a result, the estimation unit 532 obtains the notch frequencies for each of the fourth to sixth connection paths. Here, the notch frequency in the fourth connection path is f ０（２，１，１） Let the notch frequency in the fifth connection path be f ０（２，２，１） Let the notch frequency in the sixth connection path be f ０（２，３，１） The estimation unit 532 determines the acquired notch frequency value f ０（２，１，１） , f０（２，２，１） , f ０（２，３，１） These are then registered in the notch frequency table, corresponding to the fourth, fifth, and sixth connection paths, respectively.

[0169] For example, the estimation unit 532 registers information about the fourth connection path (f21 + F1 + f13) in the fiber combination item of the notch frequency table, and enters f ０（２，１，１） Register the information, register the information for the fifth connection path (f21 + F2 + f13) in the fiber combination item, and enter f in the notch frequency item. ０（２，２，１） Register the information, register the information for the sixth connection path (f21 + F3 + f13) in the fiber combination item, and enter f in the notch frequency item. ０（２，３，１） The information is registered. This registers the information shown in lines 4 to 6 of Figure 15.

[0170] Subsequently, in step S116, the route selection unit 533 selects the optimal connection path for each of the communication devices 10 and 20 based on the notch frequency table. Specifically, the route selection unit 533 refers to the notch frequency table and selects the connection path with the largest notch frequency value among the connection paths in the uplink direction. The connection paths in the uplink direction in the notch frequency table shown in Figure 15 are the first connection path (f11 + F1 + f23), the second connection path (f11 + F2 + f23), and the third connection path (f11 + F3 + f23). The route selection unit 533 selects the connection path with the largest notch frequency value among these connection paths as the optimal connection path to use for uplink communication.

[0171] Similarly, the route selection unit 533 refers to the notch frequency table and selects the connection path with the largest notch frequency value among the connection paths in the downlink direction. The connection paths in the downlink direction in the notch frequency table shown in Figure 15 are the fourth connection path (f21 + F1 + f13), the fifth connection path (f21 + F2 + f13), and the sixth connection path (f21 + F3 + f13). The route selection unit 533 selects the connection path with the largest notch frequency value among these connection paths as the optimal connection path to use for downlink communication.

[0172] In step S117, the route control unit 534 controls the connection relationship between the ports of the optical distribution units 30 and 40 so that they are connected via the connection route selected by the route selection unit 533. In the process of step S118, the optical distribution unit 30 switches the connection between ports based on the route control information notified by the control device 50. In step S119, the optical distribution unit 40 switches the connection between ports based on the route control information notified by the control device 50.

[0173] As a result of the processing from step S117 to step S119, the optical signal sent from the communication device 10 is transmitted to the communication device 20 via the optimal upstream connection path selected by the path selection unit 533, and the optical signal sent from the communication device 20 is transmitted to the communication device 10 via the optimal downstream connection path selected by the path selection unit 533. Subsequently, in step S120, communication is initiated between the communication device 10 and the communication device 20.

[0174] In the example above, the process is shown to acquire the notch frequency in one connection path and then acquire the notch frequency in another connection path. However, the acquisition of notch frequencies may be performed all at once after the signal waveform data for all connection paths has been obtained. In this configuration, the control device 50 controls each device to acquire the signal waveform data for the first connection path, and then acquire the signal waveform data for the other connection paths (for example, the second to the sixth connection paths).

[0175] According to the optical communication system 100 in the fourth embodiment configured as described above, the control device 50 determines the optimal connection path that satisfies the conditions for reducing the effects of wavelength dispersion, and the notch frequency f that appears when a specific frequency is attenuated due to wavelength dispersion. ０ The connection path with the largest value is selected. Therefore, the transmission penalty due to wavelength dispersion can be reduced. As a result, it becomes possible to extend the transmission distance of communication devices 10 and 20 equipped with a single fixed-wavelength laser as a transmission function.

[0176] (Modification) The method for selecting the optimal path in the fourth embodiment (for example, a selection direction based on notch frequency) may be applied to the second and third embodiments. For example, when the method for selecting the optimal path in the fourth embodiment is applied to the second embodiment, the communication device 10 and the communication device 20 are provided with estimation units 13a and 23a, as shown in the second embodiment. The control device 50 is not provided with estimation unit 532, as shown in the second embodiment.

[0177] The estimation unit 13a acquires the notch frequency value for each connection path in the downstream direction. Specifically, the estimation unit 13a acquires the notch frequency based on the optical signal transmitted in the fourth connection path in the downstream direction. As a result, the estimation unit 13a acquires the notch frequency of the fourth connection path. The transmission unit 11 of the communication device 10 then generates an optical signal including the notch frequency value for the fourth connection path acquired by the estimation unit 13a, and sends the generated optical signal to the optical transmission path f 11 to notify the control device 50b. Similarly, the estimation unit 13a acquires the notch frequencies of the fifth and sixth connection paths. The transmission unit 11 of the communication device 10 then generates an optical signal including the notch frequency values ​​for the fifth and sixth connection paths acquired by the estimation unit 13a, and sends the generated optical signal to the optical transmission path f 11 to notify the control device 50b.

[0178] Furthermore, the estimation unit 23a acquires the notch frequency value for each connection path in the upstream direction. Specifically, the estimation unit 23a acquires the notch frequency based on the optical signal transmitted in the first connection path in the upstream direction. In this way, the estimation unit 23a acquires the notch frequency of the first connection path. Then, the transmission unit 21 of the communication device 20 generates an optical signal including the notch frequency value of the first connection path acquired by the estimation unit 23a, and sends the generated optical signal to the optical transmission path f21 to notify the control device 50b. Similarly, the estimation unit 23a acquires the notch frequency of the second and third connection paths. Then, the transmission unit 21 of the communication device 20 generates an optical signal including the notch frequency values ​​of the second and third connection paths acquired by the estimation unit 23a, and sends the generated optical signal to the optical transmission path f21 to notify the control device 50b. After that, the control device 50b can select the optimal connection path based on the notch frequency value of each connection path.

[0179] (Fifth Embodiment) As a method for selecting the optimal connection path, the first to third embodiments showed a configuration based on zero-dispersion wavelength, and the fourth embodiment showed a configuration based on notch frequency. In the fifth embodiment, a configuration for selecting the optimal connection path based on a value other than zero-dispersion wavelength or notch frequency will be described. For example, in the fifth embodiment, a configuration for selecting the optimal connection path based on the dispersion amount value will be described. The process in the fifth embodiment is applicable to any of the first to third embodiments, but here we will explain using the first embodiment as an example.

[0180] When selecting the optimal connection path based on the dispersion value, the storage unit 54 of the control device 50 stores the wavelength dispersion table shown in Figure 16 instead of the zero-dispersion wavelength estimation table. Figure 16 is a diagram showing an example of a wavelength dispersion table in the fifth embodiment. The wavelength dispersion table has multiple records representing information about the wavelength dispersion for each connection path. The records in the wavelength dispersion table have fiber combinations and wavelength dispersion values. The fiber combination represents a combination of multiple optical transmission paths that constitute the connection path. The wavelength dispersion value represents the wavelength dispersion value in each connection path. The wavelength dispersion value is an example of information about optical transmission paths.

[0181] Unlike the estimation unit 532 in the first embodiment, the estimation unit 532 does not estimate the zero-dispersion wavelength value for each connection path, but rather estimates the wavelength dispersion amount for each connection path. For example, the estimation unit 532 estimates the notch frequency f ０ The chirp value α of the transmission unit 11 of the communication device 10, which was acquired in advance. １ , or the chirp value α of the transmitting unit 21 of the communication device 20. ２ Using these, the amount of wavelength dispersion is estimated based on the following equation (3).

[0182]

[0183] Note that in equation (3), the oscillation wavelength λ １ This shows the case where the oscillation wavelength λ １ The value of α should be the value of the oscillation wavelength of the transmitting units 11 and 21 of the communication devices 10 and 20. Also, the chirp value is different for the transmitting units 11 and 21 of the communication devices 10 and 20, respectively. Therefore, in equation (3), α should be either the value of the transmitting unit 11 of the communication device 10 or the value of the transmitting unit 21 of the communication device 20. For example, when using the chirp value of the transmitting unit 11 of the communication device 10, α in equation (3) should be α １ You can simply replace it with α, and if you use the chirp value of the transmitting unit 21 of the communication device 20, then replace α in equation (3) with α ２ You can simply replace it with that.

[0184] Furthermore, the notch frequency f in equation (3) ０The value used is obtained from the signal waveform data obtained in each connection path. Therefore, the oscillation wavelength of the transmitting unit 11 of the communication device 10 is λ １ When estimating the wavelength dispersion DL in the first connection path, the estimation unit 532 uses the notch frequency f in equation (3) above. ０ The notch frequency obtained based on the optical signal transmitted through the first connection path is used. This allows the estimation unit 532 to acquire the chromatic dispersion amount for each connection path. The estimation unit 532 registers the acquired chromatic dispersion values ​​in a chromatic dispersion table for each connection path.

[0185] The route selection unit 533 selects the optimal connection path from among multiple connection paths that satisfies the conditions for reducing the effects of wavelength dispersion, based on the wavelength dispersion values ​​registered in the wavelength dispersion table. Specifically, the route selection unit 533 selects the path with the smallest wavelength dispersion value among the wavelength dispersion values ​​of each connection path as the optimal connection path for each communication device 10, 20. For example, the route selection unit 533 selects the connection path with the smallest wavelength dispersion value among the wavelength dispersion values ​​of each connection path in the uplink direction as the optimal connection path in the uplink direction (optimal path for communication device 10), and selects the connection path with the smallest wavelength dispersion value among the wavelength dispersion values ​​of each connection path in the downlink direction as the optimal connection path in the downlink direction (optimal path for communication device 20).

[0186] (System Operation Example) Next, an example of the operation of the optical communication system 100 in the fifth embodiment will be described. The basic processing flow is the same as in Figures 3 and 4, so it will be explained using Figures 3 and 4. When the processing from step S101 to step S111 is completed, in step S112, the estimation unit 532 obtains the notch frequency based on the acquired signal waveform data. For example, the estimation unit 532 obtains the notch frequency at which the first notch appears at a frequency other than a multiple of the transmission signal frequency (1x, 2x, etc.) based on the acquired signal waveform data.

[0187] As a result, the estimation unit 532 obtains the notch frequency in the first connection path. Furthermore, the estimation unit 532 combines the obtained notch frequency with the previously obtained chirp value α of the transmission unit 11 of the communication device 10.１ and the oscillation wavelength λ of the transmitting unit 11 １ Using the above equation (3), the wavelength dispersion DL in the first connection path is estimated. Here, the wavelength dispersion DL in the first optical transmission path is D （１，１，２） L （１，１，２） The estimation unit 532 determines the estimated value D of the wavelength dispersion amount DL. （１，１，２） L （１，１，２） The data is registered in the wavelength dispersion table, corresponding to the first optical transmission path connection route. For example, the estimation unit 532 registers the information of the first connection route (f11 + F1 + f23) in the fiber combination item of the wavelength dispersion table, and enters D in the wavelength dispersion amount item. （１，１，２） L （１，１，２） The information is registered. This registers the information shown in the first row of Figure 16.

[0188] Subsequently, in step S114, the communication device 10, the communication device 20, and the control device 50 perform the same process as the process for acquiring the notch frequency in the first connection path in the other connection paths in the upstream direction. Here, the other connection paths in the upstream direction are the second connection path and the third connection path. As a result, the estimation unit 532 estimates the wavelength dispersion amount DL in the second connection path and the third connection path, respectively. Here, the wavelength dispersion amount DL in the second connection path is D （１，２，２） L （１，２，２） Let D be the wavelength dispersion amount DL in the third connection path. （１，３，２） L （１，３，２） Let's assume that.

[0189] The estimation unit 532 estimates the value D of the wavelength dispersion amount DL for each connection path. （１，２，２） L （１，２，２） and D （１，３，２） L （１，３，２） The second connection path and the third connection path are registered in the wavelength dispersion table, respectively. For example, the estimation unit 532 registers the information of the second connection path (f11 + F2 + f23) in the fiber combination item of the wavelength dispersion table, and D （１，２，２） L （１，２，２） Register the information, register the information for the third connection path (f11 + F3 + f23) in the fiber combination item, and enter D in the wavelength dispersion item. （１，３，２） L （１，３，２）The information is registered. This registers the information shown in the second and third lines of Figure 16.

[0190] Next, in step S115, the optical communication system 100 performs the same processing in the downstream direction as in the upstream direction. The processing in the downstream direction is basically the same as the processing described in the first embodiment. The difference from the first embodiment is that the estimation unit 532 estimates the amount of wavelength dispersion based on the signal waveform data acquired in each connection path in the downstream direction.

[0191] As a result, the estimation unit 532 estimates the amount of wavelength dispersion in each of the fourth to sixth connection paths. For example, the estimation unit 532 obtains the notch frequency in the fourth connection path. Furthermore, the estimation unit 532 combines the obtained notch frequency in the fourth connection path with the previously obtained chirp value α of the transmitting unit 21 of the communication device 20. ２ and the oscillation wavelength λ of the transmitting unit 21 ２ Using the above equation (3), the wavelength dispersion DL of the fourth connection path is estimated. Here, the wavelength dispersion DL in the fourth connection path is D （２，１，１） L （２，１，１） The estimation unit 532 determines the estimated value D of the wavelength dispersion amount DL. （２，１，１） L （２，１，１） The information is registered in the wavelength dispersion table, corresponding to the fourth connection path. For example, the estimation unit 532 registers the information of the fourth connection path (f21 + F1 + f13) in the fiber combination item of the wavelength dispersion table, and enters D in the wavelength dispersion amount item. （２，１，１） L （２，１，１） The information is registered. This registers the information shown in the fourth line of Figure 16.

[0192] Subsequently, the estimation unit 532 obtains the notch frequencies for the fifth and sixth connection paths, respectively. Furthermore, the estimation unit 532 combines the obtained notch frequencies for the fifth and sixth connection paths with the previously obtained chirp value α of the transmitting unit 21 of the communication device 20. ２ and the oscillation wavelength λ of the transmitting unit 21 ２Using the above equation (3), the wavelength dispersion DL of the fifth and sixth connection paths is estimated. Here, the wavelength dispersion DL in the fifth connection path is D （２，２，１） L （２，２，１） And the wavelength dispersion amount DL in the sixth connection path is D （２，３，１） L （２，３，１） The estimation unit 532 calculates the value D of the wavelength dispersion amount DL of each connection path. （２，２，１） L （２，２，１） and D （２，３，１） L （２，３，１） The data is registered in the wavelength dispersion table, corresponding to the fifth connection path and the sixth connection path, respectively. For example, the estimation unit 532 registers the information for the fifth connection path (f21 + F2 + f13) in the fiber combination item of the wavelength dispersion table, and enters D in the wavelength dispersion amount item. （２，２，１） L （２，２，１） Register the information, register the information for the sixth connection path (f21 + F3 + f13) in the fiber combination item, and enter D in the wavelength dispersion item. （２，３，１） L （２，３，１） The information is registered. This registers the information shown in lines 5 and 6 of Figure 16.

[0193] Subsequently, in step S116, the route selection unit 533 selects the optimal connection path for each of the communication devices 10 and 20 based on the wavelength dispersion table. Specifically, the route selection unit 533 refers to the wavelength dispersion table and selects the connection path with the smallest wavelength dispersion value among the connection paths in the uplink direction. The connection paths in the uplink direction in the wavelength dispersion table shown in Figure 16 are the first connection path (f11 + F1 + f23), the second connection path (f11 + F2 + f23), and the third connection path (f11 + F3 + f23). The route selection unit 533 selects the connection path with the smallest wavelength dispersion value among these connection paths as the optimal connection path to use for uplink communication.

[0194] Similarly, the route selection unit 533 refers to the wavelength dispersion table and selects the connection path with the smallest wavelength dispersion value among the connection paths in the downstream direction. The connection paths in the downstream direction in the notch frequency table shown in Figure 16 are the fourth connection path (f21 + F1 + f13), the fifth connection path (f21 + F2 + f13), and the sixth connection path (f21 + F3 + f13). The route selection unit 533 selects the connection path with the smallest wavelength dispersion value among these connection paths as the optimal connection path to use for downstream communication.

[0195] In step S117, the route control unit 534 controls the connection relationship between the ports of the optical distribution units 30 and 40 so that they are connected via the connection route selected by the route selection unit 533. In the process of step S118, the optical distribution unit 30 switches the connection between ports based on the route control information notified by the control device 50. In step S119, the optical distribution unit 40 switches the connection between ports based on the route control information notified by the control device 50.

[0196] As a result of the processing from step S117 to step S119, the optical signal sent from the communication device 10 is transmitted to the communication device 20 via the optimal upstream connection path selected by the path selection unit 533, and the optical signal sent from the communication device 20 is transmitted to the communication device 10 via the optimal downstream connection path selected by the path selection unit 533. Subsequently, in step S120, communication is initiated between the communication device 10 and the communication device 20.

[0197] In the example above, the process is shown in which the amount of chromatic dispersion in one connection path is estimated first, and then the amount of chromatic dispersion in other connection paths is estimated. However, the estimation of chromatic dispersion may be performed all at once after the signal waveform data for all connection paths has been obtained. In this configuration, the control device 50 controls each device to acquire signal waveform data for the first connection path, and then acquire signal waveform data for the other connection paths (for example, the second to the sixth connection paths).

[0198] In the optical communication system 100 of the fifth embodiment configured as described above, the control device 50 selects the connection path with the smallest value of wavelength dispersion as the optimal connection path that satisfies the conditions for reducing the effects of wavelength dispersion. Therefore, the transmission penalty due to wavelength dispersion can be reduced. As a result, it becomes possible to extend the transmission distance of communication devices 10 and 20 equipped with a single fixed-wavelength laser as a transmission function.

[0199] (Modification) The method for selecting the optimal path in the fifth embodiment (for example, a selection direction based on wavelength dispersion) may be applied to the second and third embodiments. For example, when the method for selecting the optimal path in the fifth embodiment is applied to the second embodiment, the communication device 10 and the communication device 20 are provided with estimation units 13a and 23a, as shown in the second embodiment. The control device 50 is not provided with estimation unit 532, as shown in the second embodiment.

[0200] The estimation unit 13a estimates the wavelength dispersion value for each connection path in the downstream direction. Specifically, the estimation unit 13a estimates the wavelength dispersion based on the optical signal transmitted in the fourth connection path in the downstream direction. As a result, the estimation unit 13a obtains the wavelength dispersion value for the fourth connection path. The transmission unit 11 of the communication device 10 then generates an optical signal containing the wavelength dispersion value for the fourth connection path obtained by the estimation unit 13a, and sends the generated optical signal to the optical transmission path f 11 to notify the control device 50b. Similarly, the estimation unit 13a obtains the wavelength dispersion values ​​for the fifth and sixth connection paths, respectively. The transmission unit 11 of the communication device 10 then generates an optical signal containing the wavelength dispersion values ​​for the fifth and sixth connection paths, respectively, obtained by the estimation unit 13a, and sends the generated optical signal to the optical transmission path f 11 to notify the control device 50b.

[0201] Furthermore, the estimation unit 23a acquires the wavelength dispersion value for each connection path in the upstream direction. Specifically, the estimation unit 23a estimates the wavelength dispersion based on the optical signal transmitted in the first connection path in the upstream direction. As a result, the estimation unit 23a acquires the wavelength dispersion value of the first connection path. The transmission unit 21 of the communication device 20 then generates an optical signal including the wavelength dispersion value of the first connection path acquired by the estimation unit 23a, and sends the generated optical signal to the optical transmission path f21 to notify the control device 50b. Similarly, the estimation unit 23a acquires the wavelength dispersion values ​​for the second and third connection paths. The transmission unit 21 of the communication device 20 then generates an optical signal including the wavelength dispersion values ​​for the second and third connection paths acquired by the estimation unit 23a, and sends the generated optical signal to the optical transmission path f21 to notify the control device 50b. After that, the control device 50b can select the optimal connection path based on the wavelength dispersion value of each connection path.

[0202] (Sixth Embodiment) The first to fifth embodiments described a configuration for selecting the optimal connection path when one communication device is connected to the optical distribution unit. The sixth embodiment describes a configuration for selecting the optimal connection path when multiple communication devices are connected to the optical distribution unit.

[0203] Figure 17 shows an example configuration of the optical communication system 100c in the sixth embodiment. The optical communication system 100c comprises a plurality of communication devices 10, a plurality of communication devices 20, an optical distribution unit 30, an optical distribution unit 40, and a control device 50. The optical communication system 100c differs from the first embodiment in that it comprises multiple communication devices 10 and 20. Figure 17 shows that the optical communication system 100c comprises two communication devices 10-1 to 10-2 and two communication devices 20-1 to 20-2, but there should be two or more communication devices 10 and 20. The differences will be explained below.

[0204] Each communication device 10 has the same configuration as the communication device 10 in the first embodiment. That is, each communication device 10 transmits an optical signal of the same wavelength. Each communication device 20 has the same configuration as the communication device 20 in the first embodiment. That is, each communication device 20 transmits an optical signal of the same wavelength.

[0205] When multiple communication devices are connected to the optical distribution unit, two scenarios can be envisioned: one where multiple communication devices are connected to the same optical distribution unit simultaneously, and another where multiple communication devices are connected to the same optical distribution unit sequentially. First, we will explain the case where multiple communication devices are connected to the same optical distribution unit simultaneously.

[0206] In Figure 17, the communication device 10-1 and the optical distribution unit 30 are connected by two optical transmission lines f11 and f13, and the communication device 10-2 and the optical distribution unit 30 are connected by two optical transmission lines f31 and f33. For example, optical transmission line f31 is connected to the transmitting side of the communication device 10-2, and optical transmission line f33 is connected to the receiving side of the communication device 10-2. In addition, the optical distribution unit 40 and the communication device 20-1 are connected by two optical transmission lines f21 and f23, and the optical distribution unit 40 and the communication device 20-2 are connected by two optical transmission lines f41 and f43. For example, optical transmission line f41 is connected to the transmitting side of the communication device 20-2, and optical transmission line f43 is connected to the receiving side of the communication device 20-2.

[0207] As described above, each communication device 10 uses the same wavelength (for example, wavelength λ １ Each communication device 20 transmits an optical signal of the same wavelength (for example, wavelength λ). ２ The optical signal of the device is transmitted. Therefore, the control device 50 needs to assign a different connection path to each communication device 10 and a different connection path to each communication device 20.

[0208] Therefore, when multiple communication devices 10 are simultaneously connected to the optical distribution unit 30, the estimation unit 532 of the control device 50 estimates the zero-dispersion wavelength value of each connection path in the uplink direction for each communication device 10 in the same manner as in the first embodiment. The path selection unit 533 then calculates the difference in absolute value between the zero-dispersion wavelength value of each connection path in the uplink direction for each communication device 10 and the oscillation wavelength value of each communication device 10. The path selection unit 533 then selects the combination of optical transmission path Fk and communication device 10-p that has the smallest difference in the calculated absolute values. For example, if the combination of optical transmission path F1 and communication device 10-1 has the smallest difference in absolute values, the path selection unit 533 assigns the connection path including optical transmission path F1 to communication device 10-1.

[0209] Subsequently, the route selection unit 533 selects the combination of optical transmission path Fl and communication device 10-q that has the smallest absolute difference among connection paths other than the assigned optical transmission path Fk and communication device 10-p. For example, if the combination of optical transmission path F2 and communication device 10-2 has the smallest absolute difference, the route selection unit 533 assigns the connection path including optical transmission path F2 to communication device 10-2. By repeating this process, connection paths can be assigned to all communication devices 10. The same applies to communication device 20.

[0210] Furthermore, the control device 50 can store information in advance about the distance L of the optical transmission paths connected to the communication device 10 and the communication device 20, and by prioritizing paths in order of transmission distance, it is possible to secure a path that reduces the effects of wavelength dispersion. Specifically, the path selection unit 533 assigns the path using the optical transmission path F with the smallest absolute difference from the paths using the optical transmission path f with the longest distance (for example, any of optical transmission paths f11, f13, f21, f23, f31, f33, f41, f43). By repeating this process, connection paths can be assigned to all communication devices 10. The same applies to the communication device 20.

[0211] Next, we will explain the process when multiple communication devices are connected sequentially to the same optical distribution unit. When communication devices 10-1 and 10-2 are using optical transmission paths F1 and F2, and a new communication device 10-3 is connected to the optical distribution unit 30, the route selection unit 533 assigns an optical transmission path Fx other than the optical transmission paths F1 and F2 that are currently being used to the newly connected communication device 10-3. In this case, the route selection unit 533 assigns the optical transmission path Fx to the connection path that has the smallest absolute difference among the connection paths excluding the optical transmission paths F1 and F2 that are currently being used.

[0212] With the optical communication system 100c configured as described above, even when multiple communication devices 10 and 20 are connected to the same optical distribution units 30 and 40, the same effects as in the first embodiment can be obtained.

[0213] (Seventh Embodiment) The first to sixth embodiments described configurations for selecting the optimal connection path when a communication device is connected to the optical distribution unit with two cores. Depending on the communication device, it is also conceivable that it may be connected to the optical distribution unit with one core. Therefore, the seventh embodiment describes a configuration for selecting the optimal connection path when a communication device is connected to the optical distribution unit with one core.

[0214] Figure 18 shows an example configuration of an optical communication system 100d in the seventh embodiment. The optical communication system 100d comprises a communication device 10d, a communication device 20d, an optical distribution unit 30, an optical distribution unit 40, a control device 50, a multiplexing / demultiplexing device 60, and a multiplexing / demultiplexing device 70. Each communication device 10d and 20d performs optical communication via the optical distribution unit 30 and the optical distribution unit 40. The communication devices 10d and 20d are located in geographically separated locations (for example, different bases).

[0215] In the optical communication system 100d, a signal-multiplier / demultiplier device 60 is provided between the communication device 10d and the optical signal-splitting unit 30, and a signal-multiplier / demultiplier device 70 is provided between the communication device 20d and the optical signal-splitting unit 40. The following connections are made by optical transmission lines: between the communication device 10d and the signal-multiplier / demultiplier device 60, between the signal-multiplier / demultiplier device 60 and the optical signal-splitting unit 30, between the optical signal-splitting unit 30 and the optical signal-splitting unit 40, between the optical signal-splitting unit 40 and the signal-multiplier / demultiplier device 70, between the signal-multiplier / demultiplier device 70 and the communication device 20d, between the optical signal-splitting unit 30 and the control device 50, and between the optical signal-splitting unit 40 and the control device 50. In the seventh embodiment, a case in which the communication device 10d and the communication device 20d communicate by single-core bidirectional transmission using one optical transmission line will be described.

[0216] The communication device 10d is a device that communicates with a communication device 20d located in a geographically different location. The communication device 10d is connected to the signal multiplexing / demultiplexing device 60 via a single optical transmission path f11. The communication device 10d is a BOSA (Bi-directional Optical SubAssembly) module used, for example, in a single-core bidirectional network. The communication device 10d includes a communication unit 14. The communication unit 14 is an optical transceiver that integrates a transmitting unit that sends out an optical signal of a specific wavelength and a receiving unit that receives the optical signal.

[0217] The communication device 20d is a device that communicates with the communication device 10d located in a geographically different location. The communication device 20d is connected to the signal multiplexing / demultiplexing device 70 via a single optical transmission path f21. The communication device 20d is, for example, a BOSA module used in a single-core bidirectional network. The communication device 20d includes a communication unit 24. The communication unit 24 is an optical transceiver that integrates a transmitting unit that sends out an optical signal of a specific wavelength and a receiving unit that receives the optical signal.

[0218] The signal multiplexing / demultiplexing device 60 has multiple ports. One port of the signal multiplexing / demultiplexing device 60 is connected to the communication unit 14 of the communication device 10d, and the other ports of the signal multiplexing / demultiplexing device 60 are connected to different ports 31 of the optical distribution unit 30. This allows the signal multiplexing / demultiplexing device 60 to output an optical signal sent from the communication unit 14 of the communication device 10d to a port 31 of the optical distribution unit 30 (for example, port 31-1), and to output an optical signal output from another port 31 of the optical distribution unit 30 (for example, port 31-2) to the communication unit 14 of the communication device 10d. The signal multiplexing / demultiplexing device 60 is preferably a wavelength-independent device such as a circulator or a signal multiplexing / demultiplexing coupler.

[0219] The signal multiplexing / demultiplexing device 70 has multiple ports. One port of the signal multiplexing / demultiplexing device 70 is connected to the communication unit 24 of the communication device 20d, and the other ports of the signal multiplexing / demultiplexing device 70 are connected to different ports 41 of the optical distribution unit 40. This allows the signal multiplexing / demultiplexing device 70 to output an optical signal sent from the communication unit 24 of the communication device 20d to a port 41 of the optical distribution unit 40 (for example, port 41-1), and to output an optical signal output from another port 41 of the optical distribution unit 40 (for example, port 41-2) to the communication unit 24 of the communication device 20d. The signal multiplexing / demultiplexing device 70 is preferably a wavelength-independent device such as a circulator or a signal multiplexing / demultiplexing coupler.

[0220] The control device 50 is basically the same as the configuration in the first embodiment. However, as shown in Figure 18, when each communication device 10d and 20d is connected by a single core, there are three connection paths between the communication device 10d and the communication device 20d: optical transmission path f11+F1+f21, optical transmission path f11+F2+f21, and optical transmission path f11+F3+f21. Therefore, the estimation unit 532 estimates the zero-dispersion wavelengths in the above three connection paths. The zero-dispersion wavelength estimation value table held by the control device 50 is represented as shown in Figure 19.

[0221] The control device 50 selects the optimal connection path for connecting the communication device 10d and the communication device 20d in the upstream and downstream directions, based on the zero-dispersion wavelength values ​​for each connection path registered in the zero-dispersion wavelength estimation value table and the information registered in the user management table. That is, the control device 50 selects the optimal upstream connection path for transmitting the optical signal sent from the communication device 10d to the communication device 20d, and the optimal downstream connection path for transmitting the optical signal sent from the communication device 20d to the communication device 10d. The control device 50 then controls the connection between the ports of the optical distribution units 30 and 40 so that the communication device 10d and the communication device 20d are connected using the selected optimal connection path. The method for selecting the optimal connection path is the same as in the first embodiment.

[0222] With the optical communication system 100d configured as described above, even if the communication devices 10d and 20d are single-core bidirectional devices, the same effects as in the first embodiment can be obtained.

[0223] (Modification 1) In the seventh embodiment, the control device 50 may select the optimal connection path based on the notch frequency, as shown in the fourth embodiment, or it may select the optimal connection path based on the amount of wavelength dispersion, as shown in the fifth embodiment.

[0224] (Modification 2) The optical communication system 100d may be configured to estimate the zero-dispersion wavelength in the communication devices 10d and 20d, as shown in the second embodiment. In this configuration, the communication devices 10d and 20d include estimation units 13a and 23a. The control device 50 does not include an estimation unit 532. The specific processing is basically the same as in the second embodiment, except that the optical signal sent from the communication unit 14 of the communication device 10d is input to the optical distribution unit 30 via the multiplexing / demultiplexing device 60, and the optical signal output from the optical distribution unit 30 is input to the communication unit 14 via the multiplexing / demultiplexing device 60, and the optical signal sent from the communication unit 24 of the communication device 20d is input to the optical distribution unit 40 via the multiplexing / demultiplexing device 70, and the optical signal output from the optical distribution unit 40 is input to the communication unit 24 via the multiplexing / demultiplexing device 70.

[0225] (Modification 3) The optical communication system 100d may be configured to estimate the zero-dispersion wavelength in the intermediate path and to estimate the zero-dispersion wavelength of each connection path, as shown in the third embodiment. The specific processing is basically the same as in the third embodiment, except that the optical signal sent from the communication unit 14 of the communication device 10d is input to the optical distribution unit 30 via the multiplexing / demultiplexing device 60, and the optical signal output from the optical distribution unit 30 is input to the communication unit 14 via the multiplexing / demultiplexing device 60, and the optical signal sent from the communication unit 24 of the communication device 20d is input to the optical distribution unit 40 via the multiplexing / demultiplexing device 70, and the optical signal output from the optical distribution unit 40 is input to the communication unit 24 via the multiplexing / demultiplexing device 70.

[0226] (Eighth Embodiment) The seventh embodiment showed a configuration in which a single communication device performing bidirectional single-core transmission utilizes two ports on the optical distribution unit. The eighth embodiment describes a configuration in which a single communication device performing bidirectional single-core transmission utilizes one port on the optical distribution unit.

[0227] Figure 20 shows an example configuration of the optical communication system 100e in the eighth embodiment. The optical communication system 100e comprises a communication device 10e, a communication device 20e, an optical distribution unit 30, an optical distribution unit 40, and a control device 50. Each communication device 10e and 20e performs optical communication via the optical distribution unit 30 and the optical distribution unit 40. The communication devices 10e and 20e are located in geographically separated locations (for example, different bases).

[0228] In the optical communication system 100e, the communication devices 10e and 20e are equipped with a signal multiplexing / demultiplexing device and are connected to the optical distribution units 30 and 40 by a single optical transmission path f11 and f21. The communication device 10e comprises a transmitter 11, a receiver 12, and a signal multiplexing / demultiplexing device 15. The signal multiplexing / demultiplexing device 15 has multiple ports. The first port of the signal multiplexing / demultiplexing device 15 is connected to the transmitter 11, the second port of the signal multiplexing / demultiplexing device 15 is connected to the optical transmission path f11, and the third port of the signal multiplexing / demultiplexing device 15 is connected to the receiver 12. As a result, the signal multiplexing / demultiplexing device 15 outputs the optical signal transmitted from the transmitter 11 to the optical transmission path f11. The signal multiplexing / demultiplexing device 15 outputs the optical signal transmitted from the optical transmission path f11 to the receiver 12. The multiplexing / demultiplexing device 15 is preferably a wavelength-independent device such as a circulator or a multiplexing / demultiplexing coupler.

[0229] The communication device 20e comprises a transmitting unit 21, a receiving unit 22, and a signal multiplexing / demultiplexing device 25. The signal multiplexing / demultiplexing device 25 has multiple ports. The first port of the signal multiplexing / demultiplexing device 25 is connected to the transmitting unit 21, the second port of the signal multiplexing / demultiplexing device 25 is connected to the optical transmission path f21, and the third port of the signal multiplexing / demultiplexing device 25 is connected to the receiving unit 12. As a result, the signal multiplexing / demultiplexing device 25 outputs the optical signal transmitted from the transmitting unit 21 to the optical transmission path f21. The signal multiplexing / demultiplexing device 25 is preferably a wavelength-independent device such as a circulator or a signal multiplexing / demultiplexing coupler.

[0230] In the configuration shown in Figure 20, the wavelength λ transmitted by the communication device 10e １ The optical signal and the wavelength λ transmitted by the communication device 20e ２ The optical signal is transmitted through the same connection path. Therefore, the path selection unit 533 of the control device 50 selects, for example, the zero-dispersion wavelength λ that is closest to the two wavelengths. ０ｉ The connection path is selected as the optimal connection path. That is, the path selection unit 533 selects min(|(λ). １ +λ ２ ) / 2-λ ０ｉ |) λ ０ｉSelect the route shown. Note that this is just one example of a selection method; other selection methods are also acceptable.

[0231] With the optical communication system 100e configured as described above, even if the communication devices 10e and 20e are single-core bidirectional devices, the same effects as in the first embodiment can be obtained.

[0232] (Modification 1) In the eighth embodiment, the control device 50 may select the optimal connection path based on the notch frequency, as shown in the fourth embodiment, or it may select the optimal connection path based on the amount of wavelength dispersion, as shown in the fifth embodiment.

[0233] (Modification 2) The optical communication system 100e may be configured to estimate the zero-dispersion wavelength in the communication devices 10e and 20e, as shown in the second embodiment. In this configuration, the communication devices 10e and 20e include estimation units 13a and 23a. The control device 50 does not include an estimation unit 532. The specific processing is basically the same as in the second embodiment, except that the optical signal transmitted from the transmission unit 11 of the communication device 10e is input to the optical distribution unit 30 via the multiplexing / demultiplexing device 15, and the optical signal output from the optical distribution unit 30 is input to the receiving unit 12 via the multiplexing / demultiplexing device 15, and the optical signal transmitted from the transmission unit 21 of the communication device 20e is input to the optical distribution unit 40 via the multiplexing / demultiplexing device 25, and the optical signal output from the optical distribution unit 40 is input to the receiving unit 22 via the multiplexing / demultiplexing device 25.

[0234] (Modification 3) The optical communication system 100e may be configured to estimate the zero-dispersion wavelength in the intermediate path and to estimate the zero-dispersion wavelength of each connection path, as shown in the third embodiment. The specific processing is basically the same as in the third embodiment, except that the optical signal transmitted from the transmitting unit 11 of the communication device 10e is input to the optical distribution unit 30 via the multiplexing / demultiplexing device 15, and the optical signal output from the optical distribution unit 30 is input to the receiving unit 12 via the multiplexing / demultiplexing device 15, and the optical signal transmitted from the transmitting unit 21 of the communication device 20e is input to the optical distribution unit 40 via the multiplexing / demultiplexing device 25, and the optical signal output from the optical distribution unit 40 is input to the receiving unit 22 via the multiplexing / demultiplexing device 25.

[0235] (Modification 1 common to the first to eighth embodiments) In each of the embodiments described above, the optimal connection path may be configured to be updated at a predetermined timing. For example, the control devices 50, 50a, and 50b update the optimal connection path when a predetermined period (e.g., one month) has elapsed since the last selected path setting, when a new communication device is connected, or when an already connected communication device connects to another user's communication device. This makes it possible to appropriately select the optimal path even when the laser wavelength changes due to temperature or the like.

[0236] (Modification 2 common to the first to eighth embodiments) In each of the embodiments described above, the storage units 54 and 54b do not need to be provided within the control devices 50, 50a, and 50b, and may be stored in an external device different from the control devices 50, 50a, and 50b.

[0237] (Modification 3 common to the first to eighth embodiments) In each of the embodiments described above, the user management table, the zero-dispersion wavelength estimation table, the notch frequency table, and the wavelength dispersion table may be stored in volatile memory.

[0238] (Modification 4 common to the first to eighth embodiments) Each of the embodiments described above is also applicable to the configuration shown in Figure 21. Figure 21 is a diagram illustrating other application examples of the optical communication system in each embodiment. In Figure 21, the optical communication system 100 in the first embodiment is used as an example. In addition, although Figure 21 shows the configurations of multiple application examples, only one of the configurations may be used. Here, as examples of the configurations of multiple application examples, in Figure 21, there are configurations that use a path to which optical components are connected, configurations that use a path with only optical fibers, configurations that use a path to which both (a path to which optical components are connected and a path with only optical fibers) are connected (the order does not matter), or configurations that use only one optical distribution unit by utilizing a loopback path.

[0239] As shown in Figure 21, the optical communication system 100 includes a communication device 10, a communication device 20, an optical distribution unit 30, a control device 50, and an optical component 80. Each communication device 10 and 20 performs optical communication via the optical distribution unit 30 and the optical distribution unit 40. The optical component 80 is an optical amplifier, a dispersion compensation module, or an attenuator (optical attenuator), etc. In the example shown in Figure 21, the path shown as optical transmission path F1 is a configuration that uses a path with only optical fibers or a configuration that uses only one optical distribution unit by utilizing a loopback path. The path shown as optical transmission path F2 is a configuration that uses a path to which the optical component is connected. The path shown as optical transmission path F3 is a configuration that uses a path to which both a path to which the optical component is connected and a path with only optical fibers are connected.

[0240] As shown in the configurations in Figure 21, when the optical fiber is folded back into a single optical distribution unit 30, the communication device 10 and the communication device 20 can be connected to the same port on the optical distribution unit 30. The control device 50 can select the optimal path in the configuration shown in Figure 21 using the same method as shown in the first embodiment. The same applies to other embodiments.

[0241] (Modifications common to the third to eighth embodiments) In the third to eighth embodiments described above, the method shown in Figure 22 may be applied as a method for estimating the zero-dispersion wavelength in the intermediate path. Figure 22 is a diagram illustrating another application example of the optical communication system in any of the third to eighth embodiments. In Figure 22, the optical communication system 100b in the third embodiment will be explained as an example. In the configuration shown in Figure 22, the communication device 10 will be described as estimating the zero-dispersion wavelength in the intermediate path by sending optical signals of the same wavelength to different paths.

[0242] Here, the communication device 10 has a wavelength λ １ The optical signal is sent to the control device 50b via the path R1 of the optical transmission path f11, and further, the wavelength λ １The following example will be given of sending an optical signal via a path R5 composed of optical transmission lines f11 + F1 to the control device 50b, but similar means can be applied to other paths as well. First, the communication device 10 has a wavelength λ １ The optical signal is sent to the control device 50b via the path R1 of the optical transmission path f11. The estimation unit 532b of the control device 50b receives the wavelength λ from the communication unit 51. １ The notch frequency f of the optical signal ０１（１，０，０） This is obtained. This yields the following equation (4). Here, the notch frequency f ０１ In equation (4), the "1" in "01" represents the wavelength. Also, in equation (4), the unknown parameter is the product of the dispersion slope S and the distance L, S_ ０（１，０，０） L （１，０，０） and the zero dispersion wavelength λ ０（１，０，０） That is the case.

[0243]

[0244] Next, the communication device 10 uses a wavelength λ １ The optical signal is sent to the control device 50b via the path R5, which is composed of optical transmission lines f11 + F1. The estimation unit 532b of the control device 50b receives the wavelength λ from the communication unit 51. １ The notch frequency of the optical signal is obtained. This yields the following equation (5).

[0245]

[0246] As a result of the above process, since there are 2 unknown parameters in equations (4) and (5), the estimation unit 532b can find the unknown parameters by solving the system of equations. Note that solving the system of equations yields four solutions, so a method is used to narrow down the solution to one according to the conditions.

[0247] For example, the solution when "±1" on the right side of equation (4) is used as a negative sign is the wavelength λ １ However, wavelength λ ０（１，０，０） Smaller than, and S ０（１，０，０） L （１，０，０） (λ) is greater than 0 (for example, λ １ <λ ０（１，０，０） S ０（１，０，０） L （１，０，０）When the condition > 0 is met, the "±1" on the right side of equation (4) becomes "-". Note that in the case of a system where the upper limit of distance L is fixed, the fixed upper limit L （１，０，０）ｍａｘ Use [km] ０（１，０，０） L （１，０，０） <0.092 × L （１，０，０）ｍａｘ This will be added.

[0248] For example, the solution when "±1" on the right side of equation (4) is used as a positive value is the wavelength λ １ However, wavelength λ ０（１，０，０） Larger than, and S ０（１，０，０） L （１，０，０） (λ) is greater than 0 (for example, λ １ >λ ０（１，０，０） S ０（１，０，０） L （１，０，０） When the condition > 0 is met, the "±1" on the right side of equation (4) becomes "+". Note that in the case of a system where the upper limit of distance L is fixed, the fixed upper limit L （１，０，０）ｍａｘ Use [km] ０（１，０，０） L （１，０，０） <0.092 × L （１，０，０）ｍａｘ This will be added.

[0249] For example, the solution when "±1" on the right side of equation (5) is used as a negative sign is the wavelength λ １ However, wavelength λ ０（１，１，０） Smaller than, and S ０（１，１，０） L （１，１，０） (λ) is greater than 0 (for example, λ １ <λ ０（１，１，０） S ０（１，１，０） L （１，１，０） When the condition > 0 is met, the "±1" on the right side of equation (5) becomes "-". Note that in the case of a system where the upper limit of distance L is fixed, the fixed upper limit L （１，１，０）ｍａｘ Use [km] ０（１，１，０） L （１，１，０） <0.092 × L （１，１，０）ｍａｘ This will be added.

[0250] For example, the solution when "±1" on the right side of equation (5) is used as a positive value is the wavelength λ １ However, wavelength λ ０（１，１，０） Larger than, and S ０（１，１，０） L （１，１，０）(λ) is greater than 0 (for example, λ １ >λ ０（１，１，０） S ０（１，１，０） L （１，１，０） If the condition > 0 is met, then "±1" on the right side of equation (5) becomes "+". Note that in the case of a system where the upper limit of distance L is fixed, the fixed upper limit L （１，１，０）ｍａｘ Use [km] ０（１，１，０） L （１，１，０） <0.092 × L （１，１，０）ｍａｘ This will be added.

[0251] The estimation unit 532b narrows down the four solutions to one solution based on the above conditions. The estimation unit 532b also determines the wavelength λ for each transmission line. ０ If the value of is outside the zero-dispersion wavelength range (for example, wavelengths 1300-1324 nm for a standard single-mode fiber), then the wavelength λ is outside the zero-dispersion wavelength range. ０ The value of is excluded from the candidates for zero-dispersion wavelength. The estimation unit 532b similarly calculates the product S of the dispersion slope S and distance L in the optical transmission path f23. ０（０，０，２） L （０，０，２） And, wavelength λ ０（０，０，２） The estimation unit 532b calculates the zero-dispersion wavelength λ based on the following equations (6) and (7) for the connection path (optical transmission path f11 + F1 + f23) in the direction from communication device 10 to communication device 20. ０（１，１，２） It is possible to find this.

[0252]

[0253]

[0254] In the example above, we described the connection path in the direction from communication device 10 to communication device 20 (upstream direction), but the same applies to the connection path in the direction from communication device 20 to communication device 10 (downstream direction).

[0255] Furthermore, the zero-dispersion wavelength in the optical transmission path f23 on the receiving side of the communication device 20 may be determined by the method described above, or it may be estimated by an existing method using two different wavelengths from a tunable laser controlled by the control device 50b.

[0256] The above examples described the case of two-core transmission, but the same principles apply to one-core bidirectional transmission configurations (for example, the seventh and eighth embodiments). Furthermore, the above examples described the case where there are three optical transmission paths between the communication device 10 and the communication device 20, but the same principles apply even when there are four or more optical transmission paths between the communication device 10 and the communication device 20.

[0257] In the embodiments described above, some or all of the control devices 50, 50a, 50b, or the communication devices 10, 10d, 10e, 20, 20d, 20e may be implemented using a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. The term "computer system" as used herein includes hardware such as an OS (Operating System) and peripheral devices.

[0258] Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Additionally, "computer-readable recording media" may include those that dynamically hold programs for a short period, such as communication lines used when transmitting programs over networks like the Internet or telephone lines, as well as those that hold programs for a fixed period, such as volatile memory within computer systems acting as servers or clients. The above programs may also be recorded on computer-readable recording media. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and semiconductor storage devices (e.g., SSDs: Solid State Drives), as well as storage devices such as hard disks and semiconductor storage devices built into computer systems. The above programs may also be transmitted via telecommunication lines.

[0259] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0260] The present invention is applicable to optical communication systems that communicate via optical transmission paths.

[0261] 10, 10-1 to 10-2, 10a, 10d, 10e...communication device, 11, 21...transmitting unit, 12, 22...receiving unit, 13a, 23a, 532, 532b...estimation unit, 14, 24, 51, 52...communication unit, 15, 25, 60, 70...multiplexing / demultiplexing device, 20, 20-1 to 20-2, 20a, 20d, 20e...communication device, 30, 40...optical distribution unit, 50, 50a, 50b...control device, 53, 53a, 53b...control unit, 54, 54b...storage unit, 100, 100a, 100b, 100c, 100d, 100e...optical communication system, 531, 531b...user management unit, 533...route selection unit, 534... Route Control Unit

Claims

1. A control device comprising: a path selection unit that acquires information about optical transmission paths in each of a plurality of connection paths formed by a combination of a plurality of optical transmission paths connecting one or more first communication devices and one or more second communication devices, or information about optical transmission paths in the intermediate paths of each of the plurality of connection paths, and selects the optimal connection path among the plurality of connection paths that satisfies the conditions for reducing the effects of wavelength dispersion based on the acquired information about optical transmission paths; and a path control unit that controls the path so that communication can be performed on the optimal path selected by the path selection unit.

2. The control device according to claim 1, further comprising an acquisition unit that acquires information relating to optical transmission paths in each of the plurality of connection paths, or information relating to optical transmission paths in intermediate paths of each of the plurality of connection paths.

3. The control device according to claim 2, wherein the acquisition unit, when acquiring information about an optical transmission path in an intermediate path of each of the plurality of connection paths, further acquires information about an optical transmission path in the remaining path of each of the plurality of connection paths, and acquires final information about an optical transmission path in each of the plurality of connection paths based on the acquired information about an optical transmission path in an intermediate path and the information about an optical transmission path in the remaining path.

4. The information relating to the optical transmission path is an estimated value of the zero-dispersion wavelength, a notch frequency, or a chromatic dispersion amount, and the path selection unit selects the optimal connection path for connecting the communication devices based on the difference in absolute value between the oscillation wavelength of one or more first communication devices or one or more second communication devices and the zero-dispersion wavelength in each connection path, the notch frequency in each connection path, or the chromatic dispersion amount in each connection path, according to any one of claims 1 to 3.

5. The control device according to claim 4, wherein the path selection unit, when selecting an optimal connection path based on the difference in absolute value between the oscillation wavelength of one or more first communication devices or one or more second communication devices and the zero-dispersion wavelength in each connection path, selects the connection path with the smallest difference in absolute value as the optimal connection path; when selecting an optimal connection path based on the notch frequency in each connection path, selects the connection path with the highest notch frequency as the optimal connection path; and when selecting an optimal connection path based on the amount of wavelength dispersion in each connection path, selects the connection path with the smallest amount of wavelength dispersion as the optimal connection path.

6. The control device according to any one of claims 1 to 3, wherein the route selection unit refers to a storage unit that stores information regarding optical transmission paths in each of the plurality of connection paths, or information regarding optical transmission paths in intermediate paths of each of the plurality of connection paths, and selects the optimal connection path that satisfies the conditions for reducing the effects of wavelength dispersion based on the information stored in the storage unit.

7. An optical communication system comprising one or more first communication devices, one or more second communication devices, and a control device, wherein the one or more first communication devices and the one or more second communication devices transmit optical signals of a specific wavelength, and the control device comprises: a path selection unit that acquires information about optical transmission paths in each of a plurality of connection paths formed by a combination of a plurality of optical transmission paths connecting the one or more first communication devices and the one or more second communication devices, or information about optical transmission paths in the intermediate paths of each of the plurality of connection paths, and based on the acquired information about optical transmission paths, selects the optimal connection path among the plurality of connection paths that satisfies the conditions for reducing the effects of wavelength dispersion; and a path control unit that controls the path so that communication can be performed on the optimal path selected by the path selection unit.

8. A route control method comprising: acquiring information about optical transmission paths in each of a plurality of connection paths formed by a combination of a plurality of optical transmission paths connecting one or more first communication devices and one or more second communication devices, or information about optical transmission paths in the middle of each of the plurality of connection paths; selecting the optimal connection path from the plurality of connection paths that satisfies the conditions for reducing the effects of wavelength dispersion based on the acquired information about optical transmission paths; and controlling the path so that communication can be performed on the selected optimal path.

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