Optical communication system and wavelength dispersion compensation method

Abstract

Provided is an optical communication system comprising a control device in an optical transmission path for transmitting an optical signal between a service providing device and a user device, wherein the control device has a network control unit that notifies the service providing device of an optical signal wavelength and an optical signal transmission distance in a path established between the service providing device and the user device. The service providing device has: a control unit that, for each combination of optical signal transmission distance and optical signal wavelength, adjusts a tap coefficient of a filter on the basis of the optical signal sent from the user device; and a compensation unit that uses the filter configured to have a tap coefficient adjusted for each combination to compensate for optical signal wavelength dispersion.

Description

Optical communication system and wavelength dispersion compensation method

[0001] The present invention relates to an optical communication system and a chromatic dispersion compensation method.

[0002] In order to realize high-speed, large-capacity communication in optical communication systems, it is necessary to compensate for chromatic dispersion that occurs in optical signals transmitted through optical fibers. The main transmission methods in optical communication systems are digital coherent and intensity modulation and direct detection (IM-DD).

[0003] In the digital coherent system, the cost of the equipment is high, but it is possible to compensate for chromatic dispersion with high precision. In contrast, in the IM-DD system, the cost of the equipment is low, but it is not possible to compensate for chromatic dispersion with high precision. However, in order not to hinder the emergence of cost-effective services, it is desirable that the cost of the equipment is low. For this reason, highly accurate compensation for chromatic dispersion in the IM-DD system is being studied.

[0004] Non-Patent Document 1 discloses an IM-DD optical communication system for an electrical line concentration type network. In Non-Patent Document 1, the communication equipment (transmitter / receiver) in the central office where communications are concentrated is replaced with a coherent transmitter / receiver. In addition, the tap coefficients of the filter for compensating for chromatic dispersion are optimized for each user device before communication, and the tap coefficients are switched for each user device during communication.

[0005] Furthermore, the delay requirements for services provided to user devices may not be met in an electrical concentration network. Therefore, an all-photonics network (APN) is being considered with the aim of achieving high speed, large capacity, and meeting the delay requirements (see Non-Patent Document 2).

[0006] P. Torres-Ferrera, G. Rizzelli, H. Wang, V. Ferrero and R. Gaudino, "Experimental Demonstration of 100 Gbps / λ C-Band Direct-Detection Downstream PON Using Non-Linear and CD Compensation with 29 dB+ OPL Over 0 Km-100 Km," in Journal of Lightwave Technology, vol. 40, no. 2, pp. 547-556, January 15, 2022, doi: 10.1109 / JLT.2021.3129446. "Open All-Photonic Network Functional Architecture," [Online], January 27, 2022, IOWN Global Forum, [Retrieved June 26, 2023], Internet <URL: https: / / iowngf.org / wp-content / uploads / formidable / 21 / IOWN-GF-RD-Open-APN-Functional-Architecture-1.0-1.pdf>

[0007] However, when a chromatic dispersion compensation method intended for an electrical concentration network is applied to an all-photonics network, the throughput decreases due to the processing (ranging) required to acquire information on the transmission distance. Thus, there is a problem in that it is not possible to compensate for chromatic dispersion while suppressing the decrease in throughput.

[0008] In view of the above circumstances, an object of the present invention is to provide an optical communication system and a chromatic dispersion compensation method that are capable of compensating for chromatic dispersion while suppressing a decrease in throughput.

[0009] One aspect of the present invention is an optical communications system comprising a control device in an optical transmission path that transmits an optical signal between a service providing device and a user device, wherein the control device has a network control unit that notifies the service providing device of the transmission distance of the optical signal of the path established between the service providing device and the user device and the wavelength of the optical signal, and the service providing device has a control unit that adjusts the tap coefficient of a filter based on the optical signal transmitted from the user device for each combination of the transmission distance of the optical signal and the wavelength of the optical signal, and a compensation unit that compensates for chromatic dispersion of the optical signal using the filter in which the tap coefficient adjusted for each combination is set.

[0010] One aspect of the present invention is a chromatic dispersion compensation method performed by an optical communication system having a control device in an optical transmission path that transmits an optical signal between a service providing device and a user device, the chromatic dispersion compensation method including the steps of: the control device notifying the service providing device of the transmission distance of the optical signal of a path established between the service providing device and the user device and the wavelength of the optical signal; the service providing device adjusting a tap coefficient of a filter based on the optical signal transmitted from the user device for each combination of the transmission distance of the optical signal and the wavelength of the optical signal; the service providing device recording the adjusted tap coefficient in a storage device for each combination of the transmission distance of the optical signal and the wavelength of the optical signal; and the service providing device compensating for the chromatic dispersion of the optical signal using the filter in which the tap coefficient adjusted for each combination is set.

[0011] According to the present invention, it is possible to compensate for chromatic dispersion while suppressing a decrease in throughput.

[0012] FIG. 1 is a diagram showing an example of the configuration of an optical communication system in a first embodiment. FIG. 2 is a diagram showing an example of a data table of tap coefficients in the first embodiment. FIG. 3 is a diagram showing an example of a data table of communication device information in the first embodiment. FIG. 4 is a flowchart showing an example of the operation of an optical communication system in a second embodiment. FIG. 5 is a flowchart showing an example of the operation of an optical communication system in a third embodiment. FIG. 6 is a flowchart showing an example of the operation of an optical communication system in a fourth embodiment. FIG. 7 is a flowchart showing an example of the operation of an optical communication system in a fifth embodiment. FIG. 8 is a diagram showing an example of the configuration of an optical communication system in a sixth embodiment. FIG. 9 is a diagram showing an example of the configuration of an optical communication system in a seventh embodiment. FIG. 10 is a diagram showing an example of the configuration of an optical communication system in an eighth embodiment. FIG. 11 is a diagram showing an example of the configuration of an optical communication system in a ninth embodiment. FIG. 12 is a diagram showing an example of the hardware configuration of a control device in each embodiment.

[0013] Embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) Fig. 1 is a diagram showing an example of the configuration of an optical communication system 1a in the first embodiment. The optical communication system 1a is a system that communicates using optical signals. The optical communication system 1a (point-to-multipoint communication system) includes a service providing device 2a, a gateway 3a, a concentrator 4, and N ("N" is an integer equal to or greater than 1) user devices 5a.

[0014] The service providing device 2a is a device, such as a server, that provides a service (e.g., a content distribution service) to each user device 5a. The service providing device 2a is provided, for example, in a data center. As an example, a filter for compensating for chromatic dispersion of an optical signal is provided only in the service providing device 2a. Therefore, the service providing device 2a may be more expensive than the user device 5a. The gateway 3a is provided at a position (a network relay point) that relays communication between the service providing device 2a and the user device 5a.

[0015] Hereinafter, the direction from the user device to the service providing device will be referred to as "upstream." Hereinafter, the direction from the service providing device to the user device will be referred to as "downstream."

[0016] The wavelength of the optical signal transmitted upstream and the wavelength of the optical signal transmitted downstream are the same for each combination of service providing equipment and user equipment. Also, the path (optical path) of the optical signal transmitted upstream and the path of the optical signal transmitted downstream are the same for each combination of service providing equipment and user equipment.

[0017] Control signals between the control device and each communication device are transmitted using a dedicated path in an optical transmission path that transmits optical signals. The control signals are transmitted using, for example, an Auxiliary Management and Control Channel (AMCC). In addition, in the optical transmission path, the path of the main signal and the path of the control signal are the same for each combination of communication devices that communicate with each other.

[0018] The service providing device 2 a (first communication device) includes a storage device 21 , a service control unit 22 , a DSP 23 , a DSP 24 , a service control communication device 25 a (transmitter / receiver), an IQ modulator 26 , and a coherent detector 27 .

[0019] The gateway 3a includes a control device 31a and an optical switch 32. The control device 31a includes a storage device 311, a network control unit 312, and a network control communicator 313.

[0020] The concentrator 4 concentrates optical transmission paths (optical fibers) connected to each user device 5a. The user device 5a (second communication device) includes a user control unit 51, a user-controlled communication device 52, an intensity modulator 53, and a direct detector 54.

[0021] First, the service providing device 2a will be described. The storage device 21 stores a data table of tap coefficients (database for registering tap coefficients).

[0022] 2 is a diagram showing an example of a data table of tap coefficients in the first embodiment. In the data table of tap coefficients, "transmission distance," "communication speed," "wavelength," and "tap coefficient" are associated with each other.

[0023] "Transmission distance" is the transmission distance from the service providing device 2a to the user device 5a. "Communication rate" is the communication rate of the main signal. "Wavelength" is the wavelength of the optical signal of the main signal. "Tap coefficient" is the tap coefficient of the filters provided in the DSP 23 and DSP 24. These filters are filters for compensating for chromatic dispersion. Here, instead of using the identification information of the user device 5a as a search key, the tap coefficient is selected from the data table using "transmission distance" and "wavelength" as search keys.

[0024] When a combination of the transmission distance, communication speed, wavelength of the optical signal, and tap coefficient is registered in the tap coefficient data table (when the optimized tap coefficient has been learned), the registered tap coefficient is set in the filter for downstream transmission provided in DSP 23 and the filter for upstream transmission provided in DSP 24.

[0025] 1, the description of the service providing device 2a will continue. The service control unit 22 uses control data to control the operation of each functional unit of the service providing device 2a. The service control unit 22 sets optimized tap coefficients in the DSPs 23 and 24 based on the transmission distance between the user device 5a and the service control communication unit 25a, the wavelength of the optical signal, and the communication speed of the main signal.

[0026] The DSP 23 (compensation unit) is a digital signal processor. The DSP 23 acquires downstream transmission data from a predetermined first device (not shown). The DSP 23 performs filtering on the downstream transmission data based on set tap coefficients so that the chromatic dispersion of the downstream optical signal is compensated in advance. The DSP 23 outputs a downstream transmission signal based on the filtered downstream transmission data to the IQ modulator 26.

[0027] The DSP 24 (compensation unit) is a digital signal processor. The DSP 24 performs filtering on the upstream received signal based on the set tap coefficients so as to compensate for the chromatic dispersion of the upstream transmitted optical signal. The DSP 24 outputs upstream received data based on the filtered upstream received signal to a predetermined first device (not shown).

[0028] The service control communication unit 25a uses the control signal to communicate with the network control communication unit 313. The IQ modulator 26 (In-Phase / Quadrature-Phase modulator) performs IQ quadrature modulation on the downstream transmission signal. The IQ modulator 26 transmits a downstream optical signal based on the downstream transmission signal to the gateway 3a.

[0029] The coherent detector 27 performs coherent detection processing on the received upstream optical signal, and outputs an upstream reception signal based on the received upstream optical signal to the DSP 24.

[0030] Next, the gateway 3a will be described. The control device 31a centrally controls the paths and wavelengths of optical signals between each communication device of the service providing device 2a and each communication device of each user device 5a. The storage device 311 stores a data table of communication device information (a data table for registering transceiver information (TRx information)).

[0031] 3 is a diagram showing an example of a data table of communication device information in the first embodiment. In the data table of communication device information, "communication device identification information," "communication device placement," "transmission distance," "communication speed," "upper wavelength limit," and "lower wavelength limit" are associated with each other. The "communication device identification information" may be associated with a service type.

[0032] "Identification information of a communication device" is identification information assigned to a communication device. In FIG. 3, "#0" is assigned to the service control communication device 25a as an example. Also, "#1" is assigned to the user control communication device 52 as an example. "Location of a communication device" indicates the device in which the communication device is located. In other words, "location of a communication device" indicates whether the communication device is located in a service providing device or in a user device.

[0033] "Transmission distance" represents the transmission distance of the optical signal between the communication device and the gateway 3a. In FIG. 3, the transmission distance between the service control communication device 25a "#0" and the gateway 3a is "20", and the transmission distance between the user control communication device 52 "#1" and the gateway 3a is "40", so the transmission distance between the service control communication device 25a "#0" and the user control communication device 52 "#1" is "60 (= 20 + 40)". "Communication speed" represents the communication speed of the main signal. "Upper wavelength limit" represents the upper limit of the wavelength of the optical signal of the main signal. "Lower wavelength limit" represents the lower limit of the wavelength of the optical signal of the main signal.

[0034] Returning to Fig. 1, the description of the gateway 3a continues. The network control unit 312 uses control data to control the operation of each functional unit of the control device 31a. The network control communicator 313 uses control signals to communicate with the service control communicator 25a. The network control communicator 313 also uses control signals to communicate with the user control communicator 52.

[0035] The optical switch 32 relays optical signals (main signals and control signals) between the service providing device 2a and the user device 5a. Here, the optical switch 32 relays control signals between the service control communicator 25a and the network control communicator 313. The optical switch 32 also relays control signals between the user control communicator 52 and the network control communicator 313.

[0036] Next, the user device 5a will be described. The user control unit 51 uses control data to control the operation of each functional unit of the user device 5a. The user control communicator 52 uses control signals to communicate with the network control communicator 313.

[0037] The intensity modulator 53 acquires upstream transmission data from a predetermined second device (not shown). The intensity modulator 53 performs intensity modulation on the upstream transmission data. The IQ modulator 26 transmits an upstream optical signal based on the upstream transmission data to the gateway 3a via the concentrator 4.

[0038] The direct detector 54 performs direct detection processing on the received downstream optical signal and outputs downstream reception data based on the received downstream optical signal to a predetermined second device (not shown).

[0039] Next, an example of operation of the optical communication system 1a will be described. Fig. 4 is a flowchart showing an example of operation of the optical communication system 1a in the first embodiment. The service control communicator 25a notifies the network control unit 312 of the communicator information of the service control communicator 25a (step S101). The network control unit 312 registers the communicator information of the service control communicator 25a in a data table of communicator information (step S102).

[0040] The user-controlled communicator 52 notifies the network control unit 312 of the communicator information of the user-controlled communicator 52 and the connection destination information of the user-controlled communicator 52 (step S103). The network control unit 312 registers the communicator information of the user-controlled communicator 52 in the data table of communicator information (step S104).

[0041] The network control unit 312 selects, in the data table of communication device information, communication device information for the service control communication device 25a based on the connection destination information for the user control communication device 52. The network control unit 312 establishes a path between the user control communication device 52 and the service control communication device 25a based on the communication device information for the service control communication device 25a and the communication device information for the user control communication device 52.

[0042] The network control unit 312 notifies the service control unit 22 of the establishment of the route, the wavelength of the optical signal to be used, and connection destination information of the service control communication unit 25a (information of the user control communication unit 52) ​​via the service control communication unit 25a (step S105). The service control communication unit 25a and the service control unit 22 acquire this information (step S106). The network control unit 312 notifies the user control unit 51 of the establishment of the route and the wavelength of the optical signal to be used via the user control communication unit 52 (step S107). The user control unit 51 and the user control communication unit 52 acquire this information (step S108).

[0043] The service providing device 2a transitions to a state (waiting state) in which it waits for a test signal from the user device 5a. The service control communication device 25a notifies the network control unit 312 that the state of the service providing device 2a has entered the wait state (step S109). The network control unit 312 notifies the user control unit 51 via the user control communication device 52 of permission to transmit a known test signal (step S110). The user control unit 51 and the user control communication device 52 obtain permission to transmit the known test signal (step S111).

[0044] The user-controlled communication device 52 transmits a test signal to the service providing device 2a via the concentrator 4 and the optical switch 32. The frequency of the test signal is the same as the frequency of the main signal (step S112). The coherent detector 27 performs coherent detection processing on the received test signal. The service control unit 22 and the DSP 24 optimize (adjust) the tap coefficients set in the DSP 24 through a predetermined learning process using the test signal (step S113).

[0045] The service control unit 22 sets the optimized tap coefficients in the DSP 23. The service control unit 22 associates the optimized tap coefficients with the user device 5a that transmitted the test signal and registers them in the tap coefficient data table (step S114). The service control unit 22 instructs the user control unit 51 to start communication of the main signal (step S115). The user control unit 51 receives the instruction to start communication of the main signal via the user-controlled communication unit 52 (step S116).

[0046] As described above, the optical communication system 1a includes a control device 31a in an optical transmission path that transmits an optical signal between the service providing device 2a and the user device 5a. The network control unit 312 notifies the service control unit 22 of the transmission distance and wavelength of the optical signal of the path established between the service providing device 2a and the user device 5a. The service control unit 22 adjusts the tap coefficients of the filter based on the optical signal transmitted from the user device for each combination of the transmission distance and wavelength of the optical signal. The service control unit 22 records the adjusted tap coefficients in the storage device 21 for each combination of the transmission distance and wavelength of the optical signal. The service control unit 22 compensates for chromatic dispersion of the optical signal using a filter in which the adjusted tap coefficients are set for each combination.

[0047] This makes it possible to compensate for chromatic dispersion while suppressing a decrease in throughput.

[0048] Second Embodiment The second embodiment is mainly different from the first embodiment in that second and subsequent user devices are newly connected to the optical communication system (network). The second embodiment will be described focusing on the differences from the first embodiment.

[0049] 5 is a flowchart showing an example of the operation of the optical communication system 1a in the second embodiment. Steps S201 to S208 are the same as steps S101 to S108 shown in FIG.

[0050] In the second embodiment, a time division multiplexed (TDM) optical signal is transmitted. When a second or subsequent user device 5a is newly connected (added) to the optical communication system (network), the network control unit 312 notifies the service control unit 22 of a new connection request.

[0051] The service control unit 22 sets a time window for authentication to ensure the timing of transmitting the test signal from the user device 5a. The service control unit 22 transitions to a state (waiting state) in which it waits for a test signal from the user device 5a. The service control communication unit 25a notifies the network control unit 312 that the state of the service providing device 2a has entered the waiting state and information about the timing of transmitting the test signal (step S209).

[0052] The network control unit 312 notifies the user control unit 51 of permission to transmit the known test signal and information on the transmission timing of the test signal via the user-controlled communication device 52 (step S210). The user control unit 51 and the user-controlled communication device 52 acquire the permission to transmit the known test signal and information on the transmission timing of the test signal (step S211).

[0053] The user-controlled communication device 52 transmits the test signal to the service providing device 2a via the concentrator 4 and the optical switch 32 at the notified transmission timing (step S212). The coherent detector 27 performs coherent detection processing on the received test signal. The service control unit 22 and the DSP 24 optimize the tap coefficients set in the DSP 24 by a predetermined learning process using the test signal (step S213).

[0054] The service control unit 22 sets the optimized tap coefficients in the DSP 23. The service control unit 22 associates the optimized tap coefficients with the user device 5a that transmitted the test signal and registers them in the tap coefficient data table (step S214). The service control unit 22 instructs the user control unit 51 to start communication of the main signal in a predetermined time window (step S215). The user control unit 51 receives the instruction to start communication of the main signal via the user control communication unit 52 (step S216).

[0055] As described above, the service control unit 22 ensures the timing of transmission of the test signal from the user device 5a. The user-controlled communication device 52 transmits the test signal to the service providing device 2a at the notified transmission timing via the concentrator 4 and the optical switch 32. The service control unit 22 and the DSP 24 optimize the tap coefficients set in the DSP 24 by a predetermined learning process using the test signal.

[0056] As a result, even when a second or subsequent user device 5a is newly connected to the optical communication system, it is possible to compensate for chromatic dispersion while suppressing a decrease in throughput.

[0057] Third Embodiment The third embodiment is mainly different from the second embodiment in that an optical signal subjected to frequency division multiplexing (FDM) is transmitted. The third embodiment will be described focusing on the differences from the second embodiment.

[0058] 6 is a flowchart showing an example of the operation of the optical communication system 1a in the third embodiment. Steps S301 to S308 are the same as steps S101 to S108 shown in FIG.

[0059] In the third embodiment, a frequency-division multiplexed optical signal is transmitted. When a second or subsequent user device 5 a is newly connected to the optical communication system (network), the network control unit 312 notifies the service control unit 22 of a new connection request.

[0060] The service control unit 22 sets a frequency for authentication to secure the transmission frequency of the test signal from the user device 5a. The service control unit 22 transitions to a state (waiting state) in which it waits for a test signal from the user device 5a. The service control communication unit 25a notifies the network control unit 312 that the state of the service providing device 2a has entered the wait state and information about the transmission frequency of the test signal (step S309).

[0061] The network control unit 312 notifies the user control unit 51 of permission to transmit the known test signal and information about the transmission frequency of the test signal via the user-controlled communication device 52 (step S310). The user control unit 51 and the user-controlled communication device 52 acquire the permission to transmit the known test signal and information about the transmission frequency of the test signal (step S311).

[0062] The user-controlled communication device 52 transmits a test signal of the notified transmission frequency to the service providing device 2a via the concentrator 4 and the optical switch 32 (step S312). The coherent detector 27 performs coherent detection processing on the received test signal. The service control unit 22 and the DSP 24 optimize the tap coefficients set in the DSP 24 through a predetermined learning process using the test signal (step S313).

[0063] The service control unit 22 sets the optimized tap coefficients in the DSP 23. The service control unit 22 associates the optimized tap coefficients with the user device 5a that transmitted the test signal and registers them in the tap coefficient data table (step S314). The service control unit 22 instructs the user control unit 51 to start communication of the main signal using an optical signal of a predetermined frequency (step S315). The user control unit 51 receives the instruction to start communication of the main signal via the user control communication device 52 (step S316).

[0064] As described above, the service control unit 22 secures the transmission frequency of the test signal from the user device 5a. The user-controlled communication device 52 transmits the test signal to the service providing device 2a at the notified transmission frequency via the concentrator 4 and the optical switch 32. The service control unit 22 and the DSP 24 optimize the tap coefficients set in the DSP 24 by a predetermined learning process using the test signal.

[0065] As a result, even when a second or subsequent user device 5a is newly connected to the optical communication system, it is possible to compensate for chromatic dispersion while suppressing a decrease in throughput.

[0066] (Fourth Embodiment) In the fourth embodiment, the main difference from the first to third embodiments is that the path and wavelength of the optical signal are changed. In the fourth embodiment, the differences from the first to third embodiments will be mainly described.

[0067] In an all-photonics network, the combination of optical signal paths and wavelengths is dynamically changed. Therefore, when the combination of paths and wavelengths is changed, the service providing device must relearn the tap coefficients. Here, until the relearning of the tap coefficients is complete, the communication device (transmitter / receiver) of the service providing device and the communication device (transmitter / receiver) of the user device accessing it cannot communicate directly. Therefore, the service providing device and the user device communicate with each other while the control device, service providing device, and user device cooperate with each other.

[0068] 7 is a flowchart showing an example of the operation of the optical communication system 1a in the fourth embodiment. The network control unit 312 notifies the service control unit 22 of the establishment of a route, the wavelength of the optical signal to be used, and the connection destination information of the service control communication unit 25a (information of the user control communication unit 52) ​​via the service control communication unit 25a (step S401).

[0069] The service control communication device 25a and the service control device 22 acquire this information (step S402). The network control device 312 notifies the user control device 51 of the establishment of the route and the wavelength of the optical signal to be used via the user control communication device 52 (step S403). The user control device 51 and the user control communication device 52 acquire this information (step S404).

[0070] The service control unit 22 compares the received transmission information with the transmission distance information registered in the tap coefficient data table. The service control unit 22 also compares the wavelength information of the optical signal registered in the tap coefficient data table with the wavelength information of the received optical signal. The service control unit 22 determines whether the received transmission information and wavelength are registered in the tap coefficient data table (step S405).

[0071] If it is determined that the received transmission information and wavelength are registered in the tap coefficient data table (step S405: not required), relearning (re-optimization) of the tap coefficients is not required, and the service control communication device 25a notifies the network control unit 312 that the state of the service providing device 2a has entered, for example, a waiting state. The network control unit 312 notifies the user control unit 51 via the user control communication device 52 of permission to transmit a known test signal (step S406). The user control unit 51 and the user control communication device 52 obtain permission to transmit a known test signal (step S407).

[0072] The service control unit 22 instructs the user control unit 51 to start communication of the main signal (step S408). The user control unit 51 receives the instruction to start communication of the main signal via the user control communication device 52 (step S409).

[0073] If it is determined that the received transmission information and wavelength are not registered in the tap coefficient data table (step S405: required), the tap coefficients need to be re-learned (re-optimized), and the service control unit 22 returns to step S213 illustrated in FIG. 5 or step S313 illustrated in FIG. 6.

[0074] As described above, the service control unit 22 records the adjusted tap coefficients for each combination of the transmission distance of the optical signal and the wavelength of the optical signal in the storage device 21. The service control unit 22 determines whether or not the adjusted tap coefficients associated with the changed combination are stored in the storage device 21. If the adjusted tap coefficients associated with the changed combination are not stored in the storage device 21, the service control unit 22 readjusts (re-learns) the adjusted tap coefficients for the changed combination.

[0075] This makes it possible to compensate for chromatic dispersion while suppressing a decrease in throughput even when the path and wavelength of an optical signal are changed.

[0076] Fifth Embodiment In the fifth embodiment, the main difference from the first to fourth embodiments is the method of acquiring information on the transmission distance between the control device and the communication device (the method of measuring the distance). In the fifth embodiment, the differences from the first to fourth embodiments will be mainly described.

[0077] 8 is a flowchart showing an example of operation of the optical communication system 1a according to the fifth embodiment. The network control unit 312 executes Point-to-Multipoint discovery (P2MP discovery) processing for the service providing device 2a and each user device 5a. Here, transmission distance information is acquired by ranging in the PtMP discovery processing (step S501).

[0078] Steps S502 to S505 are the same as steps S105 to S108 illustrated in Fig. 4. After step S505 is completed, the optical communication system 1a may execute steps S109 to S116 illustrated in Fig. 4.

[0079] As described above, the network control unit 312 executes the PtMP discovery process for the service providing device 2 a and each user device 5 a. As a result, even when the control device 31 a establishes a communication link with a user device 5 a detected by PtMP discovery, it is possible to compensate for chromatic dispersion while suppressing a decrease in throughput.

[0080] Sixth Embodiment The sixth embodiment is mainly different from the first embodiment in that a PON (Passive Optical Network) communication device (PON transceiver) is used for communication of control signals. The sixth embodiment will be described focusing on the differences from the first embodiment.

[0081] 9 is a diagram illustrating an example of the configuration of an optical communication system 1b according to the sixth embodiment. The optical communication system 1b is a system that communicates using optical signals. The optical communication system 1b (point-to-multipoint communication system) includes a service providing device 2b, a gateway 3b, a concentrator 4, and N user devices 5b.

[0082] The service providing device 2b includes a storage device 21, a service control unit 22, a service control communication unit 25b (transmitter / receiver), a DSP 28, and a data communication unit 29. The data communication unit 29 includes an IQ modulator 26 and a coherent detector 27.

[0083] The gateway 3b includes a control device 31b and an optical switch 32. The control device 31b includes a storage device 311, a network control unit 312, and two network control communicators 313.

[0084] The user device 5b includes a user control unit 51, a user control communication unit 55b, and a data communication unit 56. The user control communication unit 55b includes an intensity modulator 53 and a direct detector .

[0085] The service providing device 2b will now be described. The service control unit 22 transmits communication device information of the service control communication device 25b and information on the transmission frequency or transmission timing of the test signal to the control device 31b via the service control communication device 25b. The service control unit 22 acquires a control signal transmitted upstream from the control device 31b via the service control communication device 25b. The service control unit 22 sets optimized tap coefficients in the DSP 28 based on the transmission distance between the user device 5b and the service control communication device 25b, etc.

[0086] The service control communication device 25b is a PON communication device (PON transceiver), and therefore the network control device 312 can measure the transmission distance between the network control device 312 and the service control communication device 25b by PtMP discovery.

[0087] The DSP 28 (compensation unit) is a digital signal processor. The service control unit 22 and the DSP 28 optimize the tap coefficients set in the DSP 28 by a predetermined learning process using a test signal.

[0088] The DSP 28 acquires downstream transmission data from a predetermined first device (not shown). The DSP 28 performs filtering on the downstream transmission data based on set tap coefficients so that chromatic dispersion of the downstream optical signal is compensated in advance. The DSP 28 outputs a downstream transmission signal based on the filtered downstream transmission data to the data communication device 29.

[0089] The DSP 28 performs filtering on the upstream received signal based on the set tap coefficients so as to compensate for chromatic dispersion of the upstream transmitted optical signal, and outputs upstream received data based on the filtered upstream received signal to a predetermined first device (not shown).

[0090] The data communication device 29 acquires the downstream transmission signal from the DSP 28. The data communication device 29 performs IQ quadrature modulation on the downstream transmission signal. The data communication device 29 transmits a downstream optical signal based on the downstream transmission signal to the gateway 3b. The data communication device 29 performs coherent detection processing on the received upstream optical signal. The data communication device 29 outputs an upstream reception signal based on the received upstream optical signal to the DSP 28.

[0091] The gateway 3b will now be described. The storage device 311 stores a data table of communication device information and a data table of tap coefficients. The network control unit 312 transmits the tap coefficients stored in the storage device 311 to the service control unit 22 via the network control communication device 313-1 and the service control communication device 25d.

[0092] The network control communicator 313-1 communicates with the service control communicator 25b using a control signal, and the network control communicator 313-2 communicates with the user control communicator 52 using a control signal.

[0093] The user device 5b will now be described. The user control unit 51 uses control data to control the operation of each functional unit of the user device 5b. The user-controlled communication unit 55b is a PON communication unit. Therefore, the network control unit 312 can measure the transmission distance between the network control unit 312 and the user-controlled communication unit 55b by PtMP discovery.

[0094] The data communication device 56 acquires upstream transmission data from a predetermined second device (not shown). The data communication device 56 performs predetermined modulation processing on the upstream transmission data. The data communication device 56 transmits an upstream optical signal (main signal) based on the upstream transmission data to the gateway 3b via the concentrator 4. The data communication device 56 performs predetermined reception processing on the downstream optical signal (main signal). The data communication device 56 outputs downstream reception data based on the downstream optical signal to the predetermined second device (not shown).

[0095] As described above, the service control communicator 25b and the user control communicator 55b are each a PON communicator (PON transceiver). The network control unit 312 measures the transmission distance using PtMP discovery. The service control unit 22 and the DSP 28 optimize the tap coefficients set in the DSP 28 by a predetermined learning process using a test signal based on the transmission distance and wavelength of the optical signal.

[0096] This makes it possible to compensate for chromatic dispersion while suppressing a decrease in throughput. Communication for registering the learned tap coefficients in the control device 31b is not required.

[0097] Seventh Embodiment The seventh embodiment is mainly different from the sixth embodiment in that a PON communication device (PON transceiver) is not used for communication of control signals. The seventh embodiment will be described focusing on the differences from the sixth embodiment.

[0098] 10 is a diagram illustrating a configuration example of an optical communication system 1c according to the seventh embodiment. The optical communication system 1c is a system that communicates using optical signals. The optical communication system 1c (point-to-multipoint communication system) includes a service providing device 2c, a gateway 3c, a concentrator 4, and N user devices 5c.

[0099] The service providing device 2c includes a storage device 21, a service control unit 22, a service control communication unit 25c (transmitter / receiver), a DSP 28, and a data communication unit 29. The data communication unit 29 includes an IQ modulator 26 and a coherent detector 27.

[0100] The gateway 3c includes a control device 31c and an optical switch 32. The control device 31c includes a storage device 311, a network control unit 312, two network control communicators 313, and a measurement unit 314.

[0101] The user device 5c includes a user control unit 51, a user control communication unit 55c, and a data communication unit 56. The user control communication unit 55c includes an intensity modulator 53 and a direct detector 54.

[0102] The service providing device 2c will now be described. The service control unit 22 transmits communication device information of the service control communication device 25c and information on the transmission frequency or transmission timing of the test signal to the control device 31c via the service control communication device 25b. The service control unit 22 acquires the control signal transmitted upstream from the control device 31b via the service control communication device 25c. The service control unit 22 sets optimized tap coefficients in the DSP 28 based on the transmission distance measured by the measurement unit 314, etc.

[0103] The service control communication device 25c does not have to be a PON communication device. In this case, the network control device 312 cannot measure the transmission distance between the network control device 312 and the service control communication device 25c by PtMP discovery.

[0104] The user-controlled communication device 55c does not have to be a PON communication device. In this case, the network control unit 312 cannot measure the transmission distance between the network control unit 312 and the user-controlled communication device 55c by PtMP discovery.

[0105] Therefore, the measurement unit 314 measures the transmission distance between the user control communicator 55c and the control device 31c. The measurement unit 314 measures the transmission distance between the service control communicator 25c, the user device 5c, and the control device 31c. The measurement unit 314 transmits information on each transmission distance to the service control unit 22 via the network control communicator 313-1 and the service control communicator 25c.

[0106] As described above, the measurement unit 314 measures the transmission distance between the user-controlled communication device 55c and the control device 31c. The service control unit 22 and the DSP 28 optimize the tap coefficients set in the DSP 28 by a predetermined learning process using the test signal.

[0107] This makes it possible to compensate for chromatic dispersion while suppressing a decrease in throughput. Communication for registering the learned tap coefficients in the control device 31b is not required.

[0108] Eighth Embodiment The eighth embodiment is mainly different from the sixth embodiment in that tap coefficients are registered in a storage device of a control device provided in a gateway. The eighth embodiment will be described focusing on the differences from the sixth embodiment.

[0109] 11 is a diagram illustrating an example of the configuration of an optical communication system 1d according to the eighth embodiment. The optical communication system 1d is a system that communicates using optical signals. The optical communication system 1d (point-to-multipoint communication system) includes a service providing device 2d, a gateway 3d, a concentrator 4, and N user devices 5d.

[0110] The service providing device 2d includes a service control unit 22, a service control communication unit 25d (transmitter / receiver), a DSP 28, and a data communication unit 29. The data communication unit 29 includes an IQ modulator 26 and a coherent detector 27.

[0111] The gateway 3d includes a control device 31d and an optical switch 32. The control device 31d includes a storage device 311, a network control unit 312, and two network control communicators 313.

[0112] The user device 5d includes a user control unit 51, a user control communication unit 55d, and a data communication unit 56. The user control communication unit 55d includes an intensity modulator 53 and a direct detector 54.

[0113] The storage device 311 stores a data table of communication device information and a data table of tap coefficients. The network control unit 312 transmits the tap coefficients stored in the storage device 311 to the service control unit 22 via the network control communication device 313-1 and the service control communication device 25d.

[0114] The network control communicator 313-1 communicates with the service control communicator 25b using a control signal, and the network control communicator 313-2 communicates with the user control communicator 52 using a control signal.

[0115] As described above, the service control unit 22 and the network control unit 312 record the adjusted tap coefficients for each combination of the transmission distance of the optical signal and the wavelength of the optical signal in the storage device 311. The service control unit 22 and the network control unit 312 determine whether or not the adjusted tap coefficients associated with the changed combination are stored in the storage device 311. If the adjusted tap coefficients associated with the changed combination are not stored in the storage device 311, the service control unit 22 and the network control unit 312 re-adjust (re-learn) the adjusted tap coefficients for the changed combination.

[0116] This makes it possible to compensate for chromatic dispersion while suppressing a decrease in throughput. Since the tap coefficients are registered in the control device 31d, the configuration of the service providing device 2d (data center) is simplified. Information on learned tap coefficients can be shared among multiple service providing devices 2d.

[0117] Ninth Embodiment The ninth embodiment is mainly different from the seventh embodiment in that tap coefficients are registered in a storage device of a control device provided in a gateway. The ninth embodiment will be described focusing on the differences from the seventh embodiment.

[0118] 12 is a diagram illustrating a configuration example of an optical communication system 1e according to the ninth embodiment. The optical communication system 1e is a system that communicates using optical signals. The optical communication system 1e (point-to-multipoint communication system) includes a service providing device 2e, a gateway 3e, a concentrator 4, and N user devices 5e.

[0119] The service providing device 2e includes a service control unit 22, a service control communication unit 25e (transmitter / receiver), a DSP 28, and a data communication unit 29. The data communication unit 29 includes an IQ modulator 26 and a coherent detector 27.

[0120] The gateway 3e includes a control device 31e and an optical switch 32. The control device 31e includes a storage device 311, a network control unit 312, two network control communicators 313, and a measurement unit 314.

[0121] The user device 5e includes a user control unit 51, a user control communication unit 55e, and a data communication unit 56. The user control communication unit 55e includes an intensity modulator 53 and a direct detector 54.

[0122] The service control communication device 25e does not have to be a PON communication device. In this case, the network control device 312 cannot measure the transmission distance between the network control device 312 and the service control communication device 25e by PtMP discovery.

[0123] The user-controlled communication device 55e does not have to be a PON communication device. In this case, the network control unit 312 cannot measure the transmission distance between the network control unit 312 and the user-controlled communication device 55e by PtMP discovery.

[0124] Therefore, the measurement unit 314 measures the transmission distance between the user control communicator 55e and the control device 31e. The measurement unit 314 measures the transmission distance between the service control communicator 25e, the user device 5e, and the control device 31e. The measurement unit 314 transmits information on each transmission distance to the service control unit 22 via the network control communicator 313-1 and the service control communicator 25e.

[0125] As described above, the measurement unit 314 measures the transmission distance between the user-controlled communication device 55e and the control device 31e. The service control unit 22 and the network control unit 312 record the adjusted tap coefficients in the storage device 311 for each combination of the transmission distance of the optical signal and the wavelength of the optical signal. The service control unit 22 and the network control unit 312 determine whether the adjusted tap coefficients associated with the changed combination are stored in the storage device 311. If the adjusted tap coefficients associated with the changed combination are not stored in the storage device 311, the service control unit 22 and the network control unit 312 readjust (re-learn) the adjusted tap coefficients for the changed combination.

[0126] This makes it possible to compensate for chromatic dispersion while suppressing a decrease in throughput. Since the tap coefficients are registered in the control device 31e, the configuration of the service providing device 2e (data center) is simplified. Information on learned tap coefficients can be shared among multiple service providing devices 2e.

[0127] 13 is a diagram showing an example of the hardware configuration of the control device 31 in each embodiment. The control device 31 corresponds to the control device 31a of the first embodiment, the control device 31b of the sixth embodiment, the control device 31c of the seventh embodiment, the control device 31d of the eighth embodiment, and the control device 31e of the ninth embodiment.

[0128] The control device 31 is realized as software by a processor 101, such as a CPU (Central Processing Unit), executing a program stored in a storage device 103 having a non-volatile recording medium (non-transitory recording medium) and a memory 102. The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as a flexible disk, a magneto-optical disk, a ROM (Read Only Memory), and a CD-ROM (Compact Disc Read Only Memory), and non-transitory recording media such as a hard disk or a solid state drive (SSD) built into a computer system. The communication unit 104 executes predetermined communication processing.

[0129] The control device 31 may be realized using hardware (accelerator) including an electronic circuit (electronic circuit or circuitry) using, for example, an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0130] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0131] The present invention is applicable to optical communication systems.

[0132] 1a, 1b, 1c, 1d, 1e...optical communication system, 2a, 2b, 2c, 2d, 2e...service providing device, 3a, 3b, 3c, 3d, 3e...gateway, 4...line concentrator, 5a, 5b, 5c, 5d, 5e...user device, 21...storage device, 22...service control device, 23...DSP, 24...DSP, 25a, 25b, 25c, 25d, 25e...service control communication device, 26...IQ modulator, 27...coherent detector, 28 ...DSP, 29...data communication device, 31, 31a...control device, 32...optical switch, 51...user control unit, 52...user controlled communication device, 53...intensity modulator, 54...direct detector, 55b, 55c, 55d, 55e...user controlled communication device, 56...data communication device, 101...processor, 102...memory, 103...storage device, 104...communication unit, 311...storage device, 312...network control unit, 313...network controlled communication device

Claims

1. An optical communications system comprising a control device in an optical transmission path that transmits an optical signal between a service providing device and a user device, wherein the control device has a network control unit that notifies the service providing device of the transmission distance of the optical signal of the path established between the service providing device and the user device and the wavelength of the optical signal, and the service providing device has a control unit that adjusts a tap coefficient of a filter based on the optical signal transmitted from the user device for each combination of the transmission distance of the optical signal and the wavelength of the optical signal, and a compensation unit that compensates for chromatic dispersion of the optical signal using the filter in which the tap coefficient adjusted for each combination is set.

2. The optical communication system of claim 1, wherein the control unit records the adjusted tap coefficients in a storage device for each combination of the transmission distance of the optical signal and the wavelength of the optical signal, and if the adjusted tap coefficients associated with the changed combination are not stored in the storage device, the control unit re-adjusts the adjusted tap coefficients for the changed combination.

3. A chromatic dispersion compensation method executed by an optical communication system having a control device in an optical transmission path that transmits an optical signal between a service providing device and a user device, comprising: a step by the control device notifying the service providing device of the transmission distance of the optical signal of the path established between the service providing device and the user device and the wavelength of the optical signal; a step by the service providing device adjusting a tap coefficient of a filter based on the optical signal transmitted from the user device for each combination of the transmission distance of the optical signal and the wavelength of the optical signal; a step by the service providing device recording the adjusted tap coefficient in a storage device for each combination of the transmission distance of the optical signal and the wavelength of the optical signal; and a step by the service providing device compensating for the chromatic dispersion of the optical signal using the filter in which the tap coefficient adjusted for each combination is set.

Images