Transceiver and optical communication system

Abstract

Provided is a transceiver constituted by a transmitter and a receiver. The transmitter comprises: an optical transmitter that generates an optical signal by modulating, on the basis of data to be transmitted, laser light output from a transmission-side laser, and that transmits the generated optical signal; a transmission-side sweep control unit that calculates a control target value of a central frequency sweep of the transmission-side laser according to sweep information related to a frequency sweep obtained from the outside; and a transmission-side laser control unit that changes the central frequency of the transmission-side laser according to the calculated control target value of the central frequency sweep of the transmission-side laser. The receiver comprises: an optical receiver that causes the optical signal transmitted from the transmitter to interfere with locally generated light output from a reception-side laser; a reception-side sweep control unit that calculates a control target value of a central frequency sweep of the reception-side laser according to the sweep information; and a reception-side laser control unit that changes the central frequency of the reception-side laser according to the control target value of the central frequency sweep of the reception-side laser which was calculated by the reception-side sweep control unit.　

Description

Transceiver and optical communication system

[0001] The present invention relates to a transceiver and an optical communication system.

[0002] In conventional WDM (Wavelength Division Multiplexing) network technology, signals with various frequency bandwidths are stored in frequency space. For example, image G101 in FIG. 8 shows signals 1, 2, and 3 with various frequency bandwidths. However, as shown in image G102, unused areas may occur due to changes in demand over time. Under the circumstances shown in image G102, when a signal 4 requiring a large bandwidth, as shown in image G103, needs to be allocated, the allocation may not be possible due to the availability of frequencies. Therefore, a technology called "frequency defragmentation" has been proposed in the past, which organizes frequency bands in use to make band allocation easier (see, for example, Patent Document 1). As shown in image G104, frequency defragmentation allows signal 4 requiring a large bandwidth to be allocated.

[0003] JP 2012-119999 A

[0004] Seiji Okamoto, "Research on high-precision distortion compensation of ultra-multilevel signals in digital coherent optical transmission," doctoral dissertation

[0005] However, with conventional technology, it is necessary to duplicate the optical signal at the destination and also duplicate the electrical signal. This means that two transceivers are required to defragment one signal. This has led to the problem of high costs for defragmentation.

[0006] In view of the above circumstances, an object of the present invention is to provide a technique that can reduce the cost of defragmentation compared to the conventional technique.

[0007] One aspect of the present invention is a transceiver comprising a transmitter and a receiver, wherein the transmitter comprises an optical transmitter that generates an optical signal by modulating laser light output from a transmitting-side laser based on data to be transmitted, and transmits the generated optical signal, a transmitting-side sweep control unit that calculates a control target value for a center frequency sweep of the transmitting-side laser in accordance with sweep information regarding frequency sweep obtained from an external device, and a transmitting-side laser control unit that changes the center frequency of the transmitting-side laser in accordance with the control target value for the center frequency sweep of the transmitting-side laser calculated by the transmitting-side sweep control unit; and the receiver comprises an optical receiver that causes local oscillator light output from a receiving-side laser to interfere with the optical signal transmitted from the transmitter, a receiving-side sweep control unit that calculates a control target value for the center frequency sweep of the receiving-side laser in accordance with the sweep information, and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for the center frequency sweep of the receiving-side laser calculated by the receiving-side sweep control unit.

[0008] One aspect of the present invention is a transceiver comprising a transmitter and a receiver, wherein the transmitter comprises an optical transmitter that generates an optical signal by modulating laser light output from a transmitting-side laser based on data to be transmitted, and transmits the generated optical signal; a transmitting-side sweep control unit that calculates a control target value for a center frequency sweep of the transmitting-side laser in accordance with sweep information regarding frequency sweep obtained from an external device; and a transmitting-side laser control unit that changes the center frequency of the transmitting-side laser in accordance with the control target value for the center frequency sweep of the transmitting-side laser calculated by the transmitting-side sweep control unit; and the receiver comprises an optical receiver that causes local oscillator light output from a receiving-side laser to interfere with the optical signal transmitted from the transmitter, a receiving processing unit that calculates an amount of deviation of the center frequency of the receiving-side laser from the center frequency of the transmitting-side laser, a receiving-side sweep control unit that calculates a control target value for the center frequency sweep of the receiving-side laser in accordance with the amount of deviation calculated by the receiving processing unit, and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for the center frequency sweep of the receiving-side laser calculated by the receiving-side sweep control unit.

[0009] One aspect of the present invention is an optical communication system comprising a transmitter, a receiver, and one or more wavelength filters, wherein the transmitter comprises an optical transmitter that generates an optical signal by modulating laser light output from a transmitting laser based on data to be transmitted, and transmits the generated optical signal; a transmitting sweep control unit that calculates a control target value for a center frequency sweep of the transmitting laser in accordance with sweep information related to frequency sweep obtained from an external device; and a transmitting laser control unit that changes the center frequency of the transmitting laser in accordance with the control target value for the center frequency sweep of the transmitting laser calculated by the transmitting sweep control unit, and the one or more wavelength filters are configured to receive sweep information related to frequency sweep obtained from an external device. and a sweep control unit that controls the frequency band to be transmitted in accordance with information, wherein the receiver comprises an optical receiver that causes interference between local light output from a receiving-side laser and the optical signal transmitted from the transmitter and passed through the one or more wavelength filters, a reception processing unit that calculates the amount of deviation of the center frequency of the receiving-side laser from the center frequency of the transmitting-side laser, a receiving-side sweep control unit that calculates a control target value for sweeping the center frequency of the receiving-side laser in accordance with the amount of deviation calculated by the reception processing unit, and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for sweeping the center frequency of the receiving-side laser calculated by the receiving-side sweep control unit.

[0010] One aspect of the present invention is an optical communication system comprising a transmitter, a receiver, and one or more optical transmission devices each composed of a plurality of wavelength filters having a wavelength filter function, wherein the transmitter comprises an optical transmitter that generates an optical signal by modulating laser light output from a transmission-side laser based on data to be transmitted, and transmits the generated optical signal, a transmission-side sweep control unit that calculates a control target value for a center frequency sweep of the transmission-side laser in accordance with sweep information regarding frequency sweep obtained from an external device, and a transmission-side laser control unit that changes the center frequency of the transmission-side laser in accordance with the control target value for the center frequency sweep of the transmission-side laser calculated by the transmission-side sweep control unit, and the one or more optical transmission devices comprise and a sweep control unit that controls a frequency band to be transmitted through one or more wavelength filters located on a path connecting the transmitter and the receiver, wherein the receiver comprises: an optical receiver that causes interference between local light output from a receiving-side laser and the optical signal transmitted from the transmitter and passed through the one or more wavelength filters; a reception processing unit that calculates an amount of deviation of the center frequency of the receiving-side laser from the center frequency of the transmitting-side laser; a reception-side sweep control unit that calculates a control target value for sweeping the center frequency of the receiving-side laser in accordance with the amount of deviation calculated by the reception processing unit; and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for sweeping the center frequency of the receiving-side laser calculated by the reception-side sweep control unit.

[0011] According to the present invention, it is possible to reduce the cost of defragmentation compared to the conventional case.

[0012] FIG. 1 is a diagram for explaining the problems of the prior art and an overview of the present invention. FIG. 2 is a diagram for explaining a configuration example of an optical communication system in a first embodiment. FIG. 3 is a sequence diagram showing a processing flow of the optical communication system in the first embodiment. FIG. 4 is a diagram for explaining a configuration example of an optical communication system in a second embodiment. FIG. 5 is a diagram for explaining a configuration example of an optical communication system in a third embodiment. FIG. 6 is a diagram for explaining an example of frequency sweeping of a WSS in the third embodiment. FIG. 7 is a diagram for explaining frequency defragmentation.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] (Overview) Before describing the details of the present invention, the problems of the prior art and an overview of the present invention will be specifically described. FIG. 1 is a diagram for explaining the problems of the prior art and an overview of the present invention. Image G11 shows a signal in frequency space before frequency defragmentation. In the past, as shown in image G12, the source signal was duplicated at the destination frequency position and then deleted. As a result, frequency defragmentation was performed as shown in image G13. In this way, in the past, twice as many transmitters and receivers were required to duplicate the signal.

[0015] In contrast, in the present invention, as shown in image G14, frequency sweeping is performed while continuing communication (frequency sweeping from the position of frequency "A" to the position of frequency "B" shown in image G14), thereby performing frequency defragmentation without duplicating signals. This eliminates the need to duplicate signals, and therefore does not increase the number of transmitters and receivers. As a result, it is possible to reduce the cost of defragmentation compared to conventional methods. Below, a specific configuration for realizing the above processing will be described.

[0016] 2 is a diagram showing an example of the configuration of an optical communication system 100 according to a first embodiment. The optical communication system 100 includes a control device 10 and a transceiver 20.

[0017] The control device 10 transmits to the transceiver 20 sweep information related to frequency sweep for performing defragmentation in the transceiver 20. The control device 10 also transmits sweep information to transceivers that are communicating with the transceiver 20. This allows the transceiver 20 to continue communication with the other transceiver. The control device 10 is configured using an information processing device such as a personal computer. The sweep information includes, for example, information such as the sweep start time, sweep speed, and sweep time. The sweep start time indicates the time at which defragmentation is performed in the transceiver 20. The sweep speed indicates the speed (Hz / s) at which the frequency is swept. The sweep time indicates the time (seconds) for which the frequency is swept.

[0018] The transceiver 20 communicates with other transceivers using optical signals. The transceiver 20 performs defragmentation in accordance with sweep information transmitted from the control device 10. The transceiver 20 communicates with the other transceiver while sweeping the frequency in accordance with the sweep information. This allows the transceiver 20 to perform defragmentation while continuing communication.

[0019] Next, a specific configuration of the transceiver 20 will be described. The transceiver 20 includes a transmitter 30 and a receiver 40. The transmitter 30 generates an optical signal by modulating laser light output from a laser based on data to be transmitted, and transmits the generated optical signal. The receiver 40 performs coherent detection by causing interference between the local oscillator light output from the laser and the optical signal transmitted from the transceiver of the other party.

[0020] (Configuration of Transmitter 30) The transmitter 30 includes a digital signal processing device 31, a plurality of amplifiers 32, an optical transmitter 33, a sweep control unit 34, and an LD control unit 35.

[0021] A client signal, which is data to be transmitted, is input to the digital signal processing device 31. The digital signal processing device 31 performs signal processing on the input client signal. The digital signal processing device 31 is made up of a framer 311 and a transmission signal processing unit 312. The transmission signal processing unit 312 is made up of an error correction coding unit 313, a signal modulation unit 314, and multiple DACs 315.

[0022] The framer 311 frames the input client signal. The error correction encoder 313 performs error correction encoding on the client signal framed by the framer 311. The signal modulator 314 modulates the framed client signal after the error correction encoding. For example, the signal modulator 314 performs QPSK (Quadrature Phase Shift Keying) on ​​the framed client signal after the error correction encoding.

[0023] Each DAC 315 performs digital-to-analog conversion on the input modulated signal. Four lane signals, XI, XQ, YI, and YQ, are output from each DAC 315. The four lane signals output from each DAC 315 are amplified by each amplifier 32 and input to the optical transmitter 33.

[0024] The optical transmitter 33 is composed of an LD 331, two optical modulators 332 and 333, and a PBC 334. The LD 331 outputs laser light under the control of the LD control unit 35. The LD 331 is one type of transmitting laser. The optical modulator 332 modulates the laser light based on the X-polarized signals (signals XI and XQ) and the laser light output from the LD 331. In this way, the optical modulator 332 generates an X-polarized optical signal. The optical modulator 333 modulates the laser light based on the Y-polarized signals (signals YI and YQ) and the laser light output from the LD 331. In this way, the optical modulator 333 generates a Y-polarized optical signal. The PBC 334 combines the X-polarized optical signal generated by the optical modulator 332 and the Y-polarized optical signal generated by the optical modulator 333. The PBC 334 is a polarization beam combiner. The optical signal combined by the PBC 334 is sent to or input from an optical fiber transmission line.

[0025] The sweep control unit 34 calculates a control target value for the center frequency sweep of the LD 331 according to the sweep information obtained from the control device 10. The sweep control unit 34 stores in advance a function or table data that can identify the relationship between the laser center frequency and the current or temperature. The sweep control unit 34 calculates a control target value that satisfies the sweep speed at regular intervals at the timing of the sweep start time included in the sweep information. The control target value is a current control target value or a temperature control target value. The sweep control unit 34 is one aspect of a transmission-side sweep control unit.

[0026] The LD control unit 35 changes the center frequency of the LD 331 in accordance with the control target value calculated by the sweep control unit 34. The LD control unit 35 is one aspect of a transmission-side laser control unit.

[0027] (Configuration of Receiver 40 ) The receiver 40 includes an optical receiver 41 , a plurality of amplifiers 42 , a digital signal processor 43 , a sweep control unit 44 , and an LD control unit 45 .

[0028] The optical receiver 41 is composed of an LO 411, a homodyne detector 412, and a photodetector 413. The LO 411 outputs local light. Furthermore, the LO 411 outputs laser light in accordance with the control of the LD control unit 45. The LO 411 is one form of a receiving-side laser. The homodyne detector 412 is composed of existing devices such as a polarization beam splitter and a 90° optical hybrid. The optical signal homodyne-detected by the homodyne detector 412 is converted by each photodetector 413 into electrical signals XI, XQ, YI, and YQ, and input to each amplifier 42. The amplifier 42 amplifies the four-lane signals output from the optical receiver 41.

[0029] Four-lane signals are input to the digital signal processing device 43. The digital signal processing device 43 performs signal processing on the input four-lane signals. The digital signal processing device 43 is made up of a received signal processing unit 431 and a framer 432. The received signal processing unit 431 is made up of a plurality of ADCs 433, a signal demodulation unit 434, and an error correction decoding unit 435.

[0030] Each ADC 433 performs analog-to-digital conversion on the four-lane signals input. Four lane signals, XI, XQ, YI, and YQ, are output from each ADC 433. The signal demodulation unit 434 compensates for waveform distortions, such as chromatic dispersion and polarization mode dispersion, in the optical fiber transmission line for the four-lane signals output from each ADC 433. The error correction decoding unit 435 performs error correction decoding processing. The framer 432 restores the client signal from the signal that has been subjected to error correction decoding processing.

[0031] The sweep control unit 44 calculates a control target value for the center frequency sweep of the LO 411 in accordance with the sweep information obtained from the control device 10. The sweep control unit 44 stores in advance a function or table data that can identify the relationship between the laser center frequency and the current or temperature. The sweep control unit 44 calculates a control target value that satisfies the sweep speed at regular intervals at the timing of the sweep start time included in the sweep information. The sweep control unit 44 is one aspect of the receiving-side sweep control unit.

[0032] The LD control unit 45 changes the center frequency of the LO 411 in accordance with the control target value calculated by the sweep control unit 44. The LD control unit 45 is one aspect of a receiving-side laser control unit.

[0033] 3 is a sequence diagram showing the flow of processing in the optical communication system 100 according to the first embodiment. Note that the processing in FIG. 3 will be described for the case where defragmentation is performed. The control device 10 transmits sweep information to the transceiver 20 (step S101). Note that, although not shown in FIG. 3, the control device 10 also transmits sweep information to a transceiver that is a communication partner of the transceiver 20. The communication partner transceiver has a configuration similar to that of the transceiver 20. Here, the description will be given assuming that the communication partner transceiver performs reception and is equipped with a receiver 40.

[0034] The sweep control unit 34 of the transceiver 20 acquires the sweep information transmitted from the control device 10 (step S102). When the sweep start time included in the acquired sweep information arrives, the sweep control unit 34 calculates a control target value that satisfies the sweep speed based on a function or table data stored in advance (step S103). The sweep control unit 34 instructs the LD control unit 35 to control the LD 331 so as to satisfy the calculated control target value (step S104). In response to the instruction from the sweep control unit 34, the LD control unit 35 changes the center frequency of the LD 331 so as to satisfy the control target value (step S105).

[0035] The transceiver 20 performs the processes from step S103 to step S105 at regular intervals until the sweep time included in the sweep information has elapsed. The transceiver 20 performs frequency sweep in this manner. As a result, defragmentation is completed after the sweep time included in the sweep information has elapsed.

[0036] Note that the same processing as that of the transceiver 20 is performed in the transceiver that is the communication partner. Specifically, the sweep control unit 44 of the transceiver that is the communication partner acquires sweep information transmitted from the control device 10. When the sweep start time included in the acquired sweep information arrives, the sweep control unit 44 calculates a control target value that satisfies the sweep speed based on a function or table data stored in advance. The sweep control unit 44 instructs the LD control unit 45 to control the LO 411 so as to satisfy the calculated control target value. In response to the instruction from the sweep control unit 44, the LD control unit 45 changes the center frequency of the LO 411 so as to satisfy the control target value.

[0037] As described above, the same sweep information is transmitted from the control device 10 to the transceiver 20 and the transceiver with which it is communicating. Therefore, the transceiver 20 and the transceiver with which it is communicating switch frequencies at the same time. As a result, defragmentation can be performed while maintaining communication up to the destination wavelength.

[0038] In the optical communication system 100 configured as described above, the transmitter 30 includes an optical transmitter 33 that generates an optical signal by modulating the laser light output from the LD 331 based on data to be transmitted and transmits the generated optical signal, a sweep control unit 34 that calculates a control target value for the center frequency sweep of the LD 331 in accordance with sweep information obtained from the control device 10, and an LD control unit 35 that changes the center frequency of the LD 331 in accordance with the control target value for the center frequency sweep of the LD 331 calculated by the sweep control unit 34. The receiver 40 includes an optical receiver 41 that causes interference between the local oscillator light output from the LO 411 and the optical signal transmitted from the transmitter 30, a sweep control unit 44 that calculates a control target value for the center frequency sweep of the LO 411 in accordance with the sweep information, and an LD control unit 45 that changes the center frequency of the LO 411 in accordance with the control target value for the center frequency sweep of the LO 411 calculated by the sweep control unit 44.

[0039] This allows defragmentation by sweeping the frequency while continuing communication without signal duplication. This reduces the number of transceivers required for frequency defragmentation compared to conventional methods, making it possible to reduce the cost of defragmentation compared to conventional methods.

[0040] Second Embodiment In the first embodiment, a configuration was described in which both the transmitter and the receiver acquired sweep information from the control device. In the second embodiment, a configuration will be described in which only the transmitter acquires sweep information from the control device and performs frequency sweeping, and the receiver performs frequency sweeping based on a received signal.

[0041] 4 is a diagram showing an example of the configuration of an optical communication system 100a according to the second embodiment. The optical communication system 100a includes a control device 10a and a transceiver 20a.

[0042] The control device 10a transmits the sweep information to the transmitter 30 included in the transceiver 20. The control device 10a is configured using an information processing device such as a personal computer.

[0043] The transceiver 20a communicates with other transceivers using optical signals. The transceiver 20a performs defragmentation in accordance with sweep information transmitted from the control device 10a. Specifically, the transmitter 30 included in the transceiver 20a performs a frequency sweep in accordance with the sweep information transmitted from the control device 10a, and the receiver 40a performs a frequency sweep based on the received signal to perform defragmentation. The transceiver 20a communicates with the other transceiver while sweeping the frequency in accordance with the sweep information. This allows the transceiver 20a to perform defragmentation while continuing communication.

[0044] Next, the specific configuration of the transceiver 20a will be described. The transceiver 20a includes a transmitter 30 and a receiver 40a. The transceiver 20a differs in configuration from the transceiver 20 in that the transceiver 20a includes a receiver 40a instead of the receiver 40. The transmitter 30 included in the transceiver 20a performs the same processing as the transceiver 20. The following description will focus on the differences from the transceiver 20.

[0045] (Configuration of receiver 40a) The receiver 40a includes an optical receiver 41, a plurality of amplifiers 42, a digital signal processing device 43a, a sweep control unit 44a, and an LD control unit 45. The receiver 40a is different in configuration from the receiver 40 in that the receiver 40a includes a digital signal processing device 43a and a sweep control unit 44a instead of the digital signal processing device 43 and the sweep control unit 44. The following description will focus on the differences from the receiver 40.

[0046] The digital signal processing device 43a performs signal processing on the input four-lane signals. The digital signal processing device 43a is composed of a received signal processing unit 431a and a framer 432. The received signal processing unit 431a performs processing similar to that of the received signal processing unit 431 in the first embodiment. Furthermore, the received signal processing unit 431a calculates the amount of deviation of the center frequency of the LO 411 from the center frequency of the LD 331 provided in the transmitter 30. The received signal processing unit 431a may calculate the amount of deviation of the center frequency of the LO 411 from the center frequency of the LD 331 provided in the transmitter 30 using, for example, an existing frequency offset estimation circuit.

[0047] The sweep control unit 44a calculates a control target value for sweeping the center frequency of the LO 411 according to the deviation calculated by the received signal processing unit 431a. Specifically, the sweep control unit 44a calculates the control target value so as to minimize the deviation. For example, the sweep control unit 44a calculates the control target value using a predetermined search algorithm so as to minimize the deviation. For example, a hill-climbing method may be used as the predetermined search algorithm. The sweep control unit 44a performs the above process each time a received signal is obtained. The sweep control unit 44a is one aspect of a receiving-side sweep control unit.

[0048] The LD control unit 45 immediately changes the center frequency of the LO 411 in accordance with the control target value calculated by the sweep control unit 44 .

[0049] In the optical communication system 100a configured as described above, the receiver 40a changes the center frequency of the LO 411 based on the deviation of the center frequency of the LO 411 from the center frequency of the LD 331 included in the transmitter 30. Specifically, the receiver 40a calculates a control target value so as to minimize the deviation and instantly changes the center frequency of the LO 411 according to the calculated control target value. In this way, in the optical communication system 100a, unlike the first embodiment, both the transmitter 30 and the receiver 40a do not acquire sweep information. Therefore, a deviation occurs in the timing of frequency sweeps performed by the transmitter 30 and the receiver 40a, but the receiver 40a instantly changes the center frequency of the LO 411 according to the deviation. This enables defragmentation by sweeping the frequency while continuing communication without signal duplication. Therefore, the number of transceivers required for frequency defragmentation can be reduced compared to conventional methods. This makes it possible to reduce the cost of defragmentation compared to conventional methods.

[0050] (Third Embodiment) In the first and second embodiments, the description is based on the premise that the transmitter and receiver are connected by a single link. In contrast, the present invention is also applicable to a configuration in which the transmitter and receiver are connected by multiple links. Therefore, in the third embodiment, a case will be described in which the technology of the present invention is applied to a network in which one or more wavelength filters are provided in the path between the transmitter and receiver.

[0051] Fig. 5 is a diagram showing an example of the configuration of an optical communication system 100b according to the third embodiment. The optical communication system 100b includes a control device 10, a transmitter 30, a receiver 40, and a WSS 50. While Fig. 5 shows one WSS 50, two or more WSSs 50 may be provided between the transmitter 30 and the receiver 40. For simplicity of explanation, Fig. 5 shows only the transmitter 30 and the receiver 40. However, the transmitter 30 corresponds to the transmitter 30 provided in the transceiver 20 shown in the first embodiment, and the receiver 40 corresponds to the receiver provided in the transceiver of the communication partner shown in the first embodiment.

[0052] The WSS 50 changes the frequency band to be transmitted in accordance with the sweep information obtained from the control device 10. Specifically, the WSS 50 includes a sweep control unit. The sweep control unit included in the WSS 50 calculates a control target value for the center frequency of the filter that transmits the signal light in accordance with the sweep information obtained from the control device 10. The sweep control unit stores in advance a function or table data that can identify the relationship between the center frequency of the filter and the current or temperature. The sweep control unit calculates a control target value that satisfies the sweep speed at regular intervals at the sweep start time included in the sweep information. The sweep control unit then controls the transmission of the frequency band of the center frequency of the filter according to the calculated control target value. The WSS 50 is a wavelength selective switch. Note that, although the WSS 50 is described here as an example, the WSS 50 is not limited to a wavelength selective switch, and any wavelength filter that has the function of transmitting wavelengths may be used.

[0053] 6 is a diagram showing an example of frequency sweeping by the WSS 50 in the third embodiment. As shown in Fig. 6, the passband of the filter of the WSS 50 is also swept in synchronization with the sweep timing of the center frequency of the transceiver 20 (e.g., the transmitter 30 and the receiver 40). This makes it possible to apply the present invention to a normal network.

[0054] According to the optical communication system 100b configured as described above, even when applied to a normal network environment, defragmentation can be performed by sweeping the frequency while continuing communication without signal duplication. Therefore, the number of transceivers required for frequency defragmentation can be reduced compared to the conventional method. Therefore, it is possible to reduce the cost of defragmentation compared to the conventional method.

[0055] Fourth Embodiment In the third embodiment, a configuration in which one or more wavelength filters are provided between a transmitter and a receiver has been described. In the fourth embodiment, a case in which the technology of the present invention is applied to a network that performs route control by providing a reconfigurable optical add / drop multiplexer (ROADM) that has a plurality of wavelength filters between a transmitter and a receiver will be described.

[0056] Fig. 7 is a diagram showing an example of the configuration of an optical communication system 100c according to the fourth embodiment. The optical communication system 100c includes a control device 10, a transmitter 30, a receiver 40, and a plurality of ROADMs 60. Although two ROADMs 60 are shown in Fig. 7, one or more ROADMs 60 may be provided between the transmitter 30 and the receiver 40. For simplicity of explanation, Fig. 7 shows only the transmitter 30 and the receiver 40. However, the transmitter 30 corresponds to the transmitter 30 provided in the transceiver 20 shown in the first embodiment, and the receiver 40 corresponds to the receiver provided in the transceiver of the communication partner shown in the first embodiment.

[0057] As shown in Fig. 7, the ROADM 60 includes a plurality of WSSs 50. The ROADM 60 can output an input optical signal from a predetermined port, thereby outputting the optical signal from a desired path. Furthermore, the ROADM 60 changes the frequency band that is transmitted through a specific WSS 50 in accordance with sweep information obtained from the control device 10. Specifically, the ROADM 60 includes a sweep control unit.

[0058] The sweep control unit included in the ROADM 60 calculates a control target value for the center frequency of the filter that transmits the signal light, according to the sweep information obtained from the control device 10. The sweep control unit stores in advance a function or table data that can identify the relationship between the center frequency of the filter and the current or temperature. The sweep control unit calculates a control target value that satisfies the sweep speed at regular intervals, at the sweep start time included in the sweep information. The sweep control unit then controls the specific WSS 50 to transmit the frequency band of the center frequency of the filter that corresponds to the calculated control target value.

[0059] For example, the sweep control unit included in the ROADM 60 controls the frequency bands that are transmitted through one or more WSSs 50 located on the path connecting the transmitter 30 and the receiver 40. In the example shown in Fig. 7, the one or more WSSs 50 located on the path connecting the transmitter 30 and the receiver 40 are WSSs 50-1, 50-2, 50-3, and 50-4. Therefore, the sweep control unit included in the ROADM 60 controls the frequency bands that are transmitted through WSSs 50-1, 50-2, 50-3, and 50-4 using the method described above.

[0060] According to the optical communication system 100c configured as described above, defragmentation can be performed by sweeping the frequency while continuing communication without signal duplication, even while controlling the path. Therefore, the number of transceivers required for frequency defragmentation can be reduced compared to the conventional system. Therefore, it is possible to reduce the cost of defragmentation compared to the conventional system.

[0061] Some or all of the functional units of the transceiver 20, 20a are realized as software by a processor such as a central processing unit (CPU) executing a program stored in a storage device having a non-volatile storage medium (non-transitory storage medium) and in the storage unit. The program may be recorded on a computer-readable non-transitory storage medium. Examples of computer-readable non-transitory storage media include portable media such as flexible disks, magneto-optical disks, read-only memories (ROMs), and compact disc read-only memories (CD-ROMs), and storage devices such as hard disks built into computer systems.

[0062] Some or all of the functional units of the transceiver 20, 20a may be realized using hardware including electronic circuits (electronic circuits 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).

[0063] 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.

[0064] The present invention is applicable to digital coherent transceivers.

[0065] REFERENCE SIGNS LIST 10...control device, 20, 20a...transmitter / receiver, 30...transmitter, 31, 43, 43a...digital signal processing device, 32, 42...amplifier, 33...optical transmitter, 34, 44...sweep control unit, 35, 45...LD control unit, 40, 40a...receiver, 50...WSS, 60...ROADM, 311, 432...framer, 312...transmission signal processing unit, 313...error correction coding unit, 314...signal modulation unit, 315...DAC, 331...LD, 332, 333...optical modulator, 334...PBC, 411...LO, 412...homodyne detector, 413...photodetector, 431, 431a...received signal processing unit, 433...ADC, 434...signal demodulation unit 435...Error correction decoding unit

Claims

1. A transceiver comprising a transmitter and a receiver, wherein the transmitter comprises: an optical transmitter that generates an optical signal by modulating laser light output from a transmitting-side laser based on data to be transmitted, and transmits the generated optical signal; a transmitting-side sweep control unit that calculates a control target value for a center frequency sweep of the transmitting-side laser in accordance with sweep information regarding frequency sweep obtained from an external device; and a transmitting-side laser control unit that changes the center frequency of the transmitting-side laser in accordance with the control target value for the center frequency sweep of the transmitting-side laser calculated by the transmitting-side sweep control unit; and the receiver comprises: an optical receiver that causes local oscillator light output from a receiving-side laser to interfere with the optical signal transmitted from the transmitter; a receiving-side sweep control unit that calculates a control target value for the center frequency sweep of the receiving-side laser in accordance with the sweep information; and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for the center frequency sweep of the receiving-side laser calculated by the receiving-side sweep control unit.

2. A transceiver comprising a transmitter and a receiver, wherein the transmitter comprises: an optical transmitter that generates an optical signal by modulating laser light output from a transmitting-side laser based on data to be transmitted, and transmits the generated optical signal; a transmitting-side sweep control unit that calculates a control target value for the sweep of the center frequency of the transmitting-side laser in accordance with sweep information regarding frequency sweep obtained from outside; and a transmitting-side laser control unit that changes the center frequency of the transmitting-side laser in accordance with the control target value for the sweep of the center frequency of the transmitting-side laser calculated by the transmitting-side sweep control unit; and the receiver comprises: an optical receiver that causes local oscillator light output from a receiving-side laser to interfere with the optical signal transmitted from the transmitter, a receiving processing unit that calculates the amount of deviation of the center frequency of the receiving-side laser from the center frequency of the transmitting-side laser, a receiving-side sweep control unit that calculates the control target value for the sweep of the center frequency of the receiving-side laser in accordance with the amount of deviation calculated by the receiving processing unit, and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for the sweep of the center frequency of the receiving-side laser calculated by the receiving-side sweep control unit.

3. An optical communication system comprising a transmitter, a receiver, and one or more wavelength filters, wherein the transmitter comprises: an optical transmitter that generates an optical signal by modulating laser light output from a transmitting laser based on data to be transmitted, and transmits the generated optical signal; a transmitting sweep control unit that calculates a control target value for sweeping the center frequency of the transmitting laser in accordance with sweep information regarding frequency sweep obtained from the outside; and a transmitting laser control unit that changes the center frequency of the transmitting laser in accordance with the control target value for sweeping the center frequency of the transmitting laser calculated by the transmitting sweep control unit, and the one or more wavelength filters comprise: a sweep control unit that controls a frequency band to be transmitted in accordance with sweep information regarding frequency sweep obtained from the outside; and the receiver comprises: an optical receiver that causes local light output from a receiving laser to interfere with the optical signal transmitted from the transmitter and passed through the one or more wavelength filters; a receiving processing unit that calculates the amount of deviation of the center frequency of the receiving laser from the center frequency of the transmitting laser; an optical communication system comprising: a receiving-side sweep control unit that calculates a control target value for sweeping the center frequency of the receiving-side laser in accordance with the deviation calculated by the receiving processing unit; and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for sweeping the center frequency of the receiving-side laser calculated by the receiving-side sweep control unit.

4. An optical communication system comprising a transmitter, a receiver, and one or more optical transmission devices each composed of a plurality of wavelength filters having wavelength filtering functions, wherein the transmitter comprises: an optical transmitter that generates an optical signal by modulating laser light output from a transmitting laser based on data to be transmitted, and transmits the generated optical signal; a transmitting sweep control unit that calculates a control target value for sweeping the center frequency of the transmitting laser in accordance with sweep information regarding frequency sweep obtained from the outside; and a transmitting laser control unit that changes the center frequency of the transmitting laser in accordance with the control target value for sweeping the center frequency of the transmitting laser calculated by the transmitting sweep control unit; and the one or more optical transmission devices comprise: a sweep control unit that controls a frequency band to be transmitted in one or more wavelength filters located on a path connecting the transmitter and the receiver in accordance with sweep information regarding frequency sweep obtained from the outside; and the receiver comprises: an optical receiver that causes local light output from a receiving laser to interfere with the optical signal transmitted from the transmitter and passed through the one or more wavelength filters; a receiving processing unit that calculates the amount of deviation of the center frequency of the receiving laser from the center frequency of the transmitting laser; an optical communication system comprising: a receiving-side sweep control unit that calculates a control target value for sweeping the center frequency of the receiving-side laser in accordance with the deviation calculated by the receiving processing unit; and a receiving-side laser control unit that changes the center frequency of the receiving-side laser in accordance with the control target value for sweeping the center frequency of the receiving-side laser calculated by the receiving-side sweep control unit.

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