Optical repeater and optical repeater method

Abstract

Provided is an optical relay device (10) comprising: a first reception unit (11) that receives a first optical signal; a second reception unit (12) that receives a second optical signal; a measurement unit (13) that sequentially measures the quality of the first optical signal and the quality of the second optical signal; a first compensation unit (14) that compensates for the first optical signal on the basis of the quality of the first optical signal measured by the measurement unit; a second compensation unit (15) that compensates for the second optical signal on the basis of the quality of the second optical signal measured by the measurement unit; a first transmission unit (16) that transmits the first optical signal which has been wavelength-converted; and a second transmission unit (17) that transmits the second optical signal which has been wavelength-converted.

Description

Optical repeater, wavelength converter, optical communication system, and optical repeater method

[0001] The present disclosure relates to an optical repeater, a wavelength converter, an optical communication system, and an optical repeater method.

[0002] In core networks that support high-capacity communications, development of technologies to meet the need for increased capacity has been progressing, including wavelength division multiplexing (WDM), which multiplexes and transmits optical signals of multiple different wavelengths on a single optical fiber, and advanced modulation methods such as dual polarization differential quadrature phase shift keying (DP-QPSK) and 16-quadrature amplitude modulation (16-QAM).

[0003] With the advancement of 5G (5th Generation) services in wireless communications, there is a growing need not only for higher capacity but also for lower network latency.

[0004] In an optical communication system, the same wavelength cannot be used within an optical fiber, so optical signals arriving at an optical repeater (relay node) with the same wavelength but traveling on different routes cannot be accommodated in the same optical fiber. Therefore, an optical repeater converts the wavelength of an optical signal on one route so that the optical signal on that route and the optical signal on another route can be accommodated in the same optical fiber.

[0005] Patent Document 1 discloses a technique for easily monitoring the transmission quality of each optical signal of a wavelength-multiplexed optical signal in a transmission path.

[0006] Japanese Patent Application Laid-Open No. 2005-341161

[0007] However, in related technologies, for example, if signal processing such as error detection and correction is minimized in order to reduce delays associated with relaying, it is possible that optical signals may not be transmitted properly.

[0008] In view of the above-mentioned problems, an object of the present disclosure is to provide a technology that can more appropriately transmit an optical signal in an optical communication system in which the wavelength of the optical signal is converted by an optical repeater device along the path.

[0009] In a first aspect of the present disclosure, there is provided an optical repeater device having a first receiving unit that receives a first optical signal, a second receiving unit that receives a second optical signal, a measuring unit that sequentially measures the quality of the first optical signal and the quality of the second optical signal, a first compensating unit that compensates the first optical signal based on the quality of the first optical signal measured by the measuring unit, a second compensating unit that compensates the second optical signal based on the quality of the second optical signal measured by the measuring unit, a first transmitting unit that transmits the wavelength-converted first optical signal, and a second transmitting unit that transmits the wavelength-converted second optical signal.

[0010] Furthermore, in a second aspect of the present disclosure, there is provided an optical communication system including an optical repeater and a management device, wherein the optical repeater includes a first receiving unit that receives a first optical signal, a second receiving unit that receives a second optical signal, a measurement unit that sequentially measures the quality of the first optical signal and the quality of the second optical signal, a first compensation unit that compensates the first optical signal based on the quality of the first optical signal measured by the measurement unit, a second compensation unit that compensates the second optical signal based on the quality of the second optical signal measured by the measurement unit, a first transmission unit that transmits the wavelength-converted first optical signal, and a second transmission unit that transmits the wavelength-converted second optical signal, and the management device switches the reception unit that receives the first optical signal from the first reception unit to the second reception unit based on the quality of the first optical signal measured by the measurement unit.

[0011] Furthermore, in a third aspect of the present disclosure, there is provided a wavelength conversion device having a first receiving unit that receives a first optical signal, a second receiving unit that receives a second optical signal, a measuring unit that sequentially measures the quality of the first optical signal and the quality of the second optical signal, a first compensating unit that compensates the first optical signal based on the quality of the first optical signal measured by the measuring unit, a second compensating unit that compensates the second optical signal based on the quality of the second optical signal measured by the measuring unit, a first transmitting unit that transmits the wavelength-converted first optical signal, and a second transmitting unit that transmits the wavelength-converted second optical signal.

[0012] Furthermore, a fourth aspect of the present disclosure provides an optical relay method including receiving a first optical signal at a first receiving unit, receiving a second optical signal at a second receiving unit, sequentially measuring the quality of the first optical signal and the quality of the second optical signal, compensating the first optical signal based on the measured quality of the first optical signal, transmitting the wavelength-converted first optical signal, and compensating the second optical signal based on the measured quality of the second optical signal, and transmitting the wavelength-converted second optical signal.

[0013] According to one aspect, in an optical communication system in which the wavelength of an optical signal is converted by an optical repeater in a path, the optical signal can be transmitted more appropriately.

[0014] 1 is a diagram illustrating an example of the configuration of an optical repeater according to an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of an optical communication system according to an embodiment. FIG. 3 is a diagram illustrating an example of processing of an optical repeater according to an embodiment. FIG. 4 is a diagram illustrating an example of information recorded in a measurement result table according to an embodiment. FIG. 5 is a diagram illustrating an example of a more detailed configuration of an optical repeater according to an embodiment. FIG. 6 is a diagram illustrating an example of the configuration of a wavelength conversion device according to an embodiment. FIG. 7 is a diagram illustrating an example of the configuration of a coherent receiver front end (FE) according to an embodiment. FIG. 8 is a diagram illustrating an example of the configuration of a coherent transmitter front end according to an embodiment. FIG. 9 is a diagram illustrating an example of the configuration of a wavelength conversion device according to an embodiment. FIG. 10 is a diagram illustrating an example of the configuration of a wavelength conversion device according to an embodiment. FIG. 11 is a diagram illustrating an example of the hardware configuration of a computer of a determination unit (control unit) according to an embodiment.

[0015] The principles of the present disclosure will be described with reference to some exemplary embodiments. It should be understood that these embodiments are set forth for illustrative purposes only, to aid those skilled in the art in understanding and practicing the present disclosure, without implying any limitation on the scope of the disclosure. The disclosure described herein may be implemented in various ways other than those described below.

[0016] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. (Embodiment 1) <Configuration of Optical Repeater 10> The configuration of the optical repeater 10 according to the embodiment will be described with reference to FIG. 1. FIG. 1 is a diagram illustrating an example of the configuration of the optical repeater 10 according to the embodiment. In the example of FIG. 1, the optical repeater 10 includes a first receiving unit 11, a second receiving unit 12, a measuring unit 13, a first compensating unit 14, a second compensating unit 15, a first transmitting unit 16, and a second transmitting unit 17. Note that the number of pairs of receiving units, compensating units, and transmitting units may be two or more and is not limited to the example of FIG. 1. Note that in the present disclosure, the light of the optical signal, the analog electrical signal converted from the optical signal, and the digital data converted from the optical signal may be simply referred to as an "optical signal."

[0018] The first receiving unit 11 is a port that receives a first optical signal. The second receiving unit 12 is a port that receives a second optical signal. The first optical signal and the second optical signal may be optical signals that have different source nodes (optical repeaters, terminals, etc.) or different destination (destination) nodes.

[0019] The measurement unit 13 sequentially measures the quality of the first optical signal and the quality of the second optical signal. The first compensation unit 14 compensates the first optical signal based on the quality of the first optical signal measured by the measurement unit 13. The second compensation unit 15 compensates the second optical signal based on the quality of the second optical signal measured by the measurement unit 13.

[0020] The first transmitting unit 16 is a port that transmits the wavelength-converted first optical signal. The first transmitting unit 16 may transmit the first optical signal having a wavelength different from the wavelength of the first optical signal received by the first receiving unit 11 to a destination node.

[0021] The second transmitting unit 17 is a port that transmits the wavelength-converted second optical signal. The second transmitting unit 17 may transmit the second optical signal, which has a wavelength different from the wavelength of the second optical signal received by the second receiving unit 12, to a destination node.

[0022] (Embodiment 2) <System Configuration> Next, the configuration of an optical communication system 1 according to an embodiment will be described with reference to Figure 2. The optical communication system 1 may be, for example, an all-photonics network that uses O-A-O (Optical to Analog to Optical) wavelength conversion, which converts the wavelength of an optical signal by analog signal processing without performing digital signal processing. Furthermore, the optical communication system 1 may include, for example, an optical repeater that converts an optical signal of a certain wavelength into a digital signal and reconverts it into an optical signal of a different wavelength without performing digital signal processing such as error detection and correction.

[0023] Fig. 2 is a diagram illustrating an example of the configuration of an optical communication system 1 according to an embodiment. In the example of Fig. 2, the optical communication system 1 includes optical repeaters 10A to 10G (hereinafter, when there is no need to distinguish between them, they will also be simply referred to as "optical repeaters 10") and a management device 20. The management device 20 may be referred to as, for example, an NMS (Network Management System) or a network manager. Note that the number of optical repeaters 10 and management devices 20 is not limited to the example of Fig. 2.

[0024] In the example of Figure 2, optical repeaters 10A-D form a ring network R1. Optical repeaters 10D-G form a ring network R2. Optical repeater 10D connects ring networks R1 and R2. The optical repeater 10 may have a function to convert electrical signals of data transmitted from a terminal into optical signals and transmit the optical signals. The optical repeater 10 may also have a function to convert received optical signals into electrical signals and transmit the signals to the terminal.

[0025] The management device 20 is connected to one or more optical repeaters 10 via signal lines (e.g., optical fibers or LAN (Local Area Network) cables). Each optical repeater 10 is connected to two or more other optical repeaters 10 via optical transmission paths (e.g., optical fibers). The connection form (network topology) of the management device 20 and each optical repeater 10 may be, for example, a mesh shape or a ring shape.

[0026] <Processing> Next, an example of processing of the optical repeater 10 according to the embodiment will be described with reference to FIGS. 3 and 4 . FIG. 3 is a flowchart showing an example of processing of the optical repeater 10 according to the embodiment. Note that the following processing may be executed, for example, when the first receiving unit 11 receives the first optical signal and the first transmitting unit 16 transmits (relays, forwards) the first optical signal. Below, processing for the first set of the first receiving unit 11, the first compensating unit 14, and the first transmitting unit 16 will be described. However, similar processing is also executed for the second set of the second receiving unit 12, the second compensating unit 15, and the second transmitting unit 17. Because the measurement unit 13 is shared by both the first set and the second set, the measurement unit 13 may execute processing for the first set and processing for the second set sequentially (intermittently at different timings).

[0027] In step S101, the measurement unit 13 refers to the measurement result table 401 and detects that it is time to measure the quality of the first optical signal received by the first receiving unit 11. In the example of FIG. 4 , the measurement result table 401 records the communication start date and time, quality, compensation parameters, and next measurement timing in association with a pair of a port ID and a wavelength ID. The port ID is identification information of a physical port connecting each optical fiber in the optical repeater 10. The wavelength ID is identification information of the wavelength (band) of the optical signal. The communication start date and time is the date and time when communication by the optical signal started. The quality is the quality of the optical signal. The quality may be, for example, a Q value. The compensation parameters are compensation parameters for the optical signal calculated based on parameters when the measurement unit 13 performs error detection to measure the quality of the optical signal. The communication start date and time may be recorded by the measurement unit 13, for example, when communication by the optical signal starts.

[0028] The next measurement timing is information indicating the timing when the quality of the optical signal will be measured next. In the example of Fig. 4, it is recorded that the optical signal with wavelength L1 received at port P1 will be measured at time T1.

[0029] Next, the measurement unit 13 measures the quality of the first optical signal received by the first receiving unit 11 (step S102). Here, the measurement unit 13 may calculate (measure) the quality of the first optical signal based on, for example, an error rate (e.g., a bit error rate (BER) or a Q-factor) of the first optical signal based on an error correction code (ECC) of data based on the first optical signal received by the first receiving unit 11. In this case, a lower error rate indicates higher (better) quality. Note that the error correction code may be, for example, a code added so that errors occurring during data transmission can be corrected on the receiving side. The error correction code may be, for example, added in advance at the time of data transmission by forward error correction (FEC). Note that the measurement unit 13 may calculate the quality based on the error correction code using digital data that has been subjected to A / D (analog-to-digital) conversion of the first optical signal and then subjected to processes such as frequency compensation, polarization separation, and symbol mapping.

[0030] Next, the measurement unit 13 determines the timing for next measuring the quality of the first optical signal, etc., and records the determined timing in the measurement result table 401 (step S103). Here, the measurement unit 13 may record the quality, compensation parameters, next measurement timing, etc., in association with a combination of a port ID and a wavelength ID corresponding to the first optical signal, for example.

[0031] (Example of determining measurement frequency based on optical signal quality) The measurement unit 13 may determine the frequency at which to measure the quality of an optical signal based on the quality of the measured optical signal. In this case, for example, if the quality of the measured optical signal is a first quality, the measurement unit 13 may measure the quality of the optical signal at a first frequency, and if the quality of the measured optical signal is a second quality lower than the first quality, the measurement unit 13 may measure the quality of the optical signal at a second frequency higher than the first frequency. In this way, the lower the quality of the optical signal, the more frequently it is measured. Therefore, optical signals of lower quality can be compensated for more frequently.

[0032] (Example of Determining Measurement Frequency Based on Elapsed Time of Optical Signal Communication) The measurement unit 13 may determine the frequency of measuring the quality of the optical signal based on the elapsed time of the optical signal communication. In this case, for example, when the elapsed time of the optical signal communication is a first elapsed time, the measurement unit 13 may measure the quality of the optical signal at a third frequency. When the elapsed time of the optical signal communication is a second elapsed time longer than the first elapsed time, the measurement unit 13 may measure the quality of the optical signal at a fourth frequency lower than the third frequency. As a result, the shorter the elapsed time of the optical signal communication is, the more frequently the measurement is performed. Therefore, for example, an optical signal for which the operation of other optical repeaters 10 is relatively unstable shortly after communication has been established can be compensated for more frequently. Note that the measurement unit 13 may calculate the elapsed time of the optical signal communication as the time elapsed from the communication start date and time recorded in the measurement result table 401 to the current date and time.

[0033] Next, the measurement unit 13 determines whether compensation for the first optical signal is necessary based on the measured quality (step S104). Here, the measurement unit 13 may determine that compensation for the optical signal is necessary, for example, if the measured quality is less than a threshold. Furthermore, the measurement unit 13 may determine that the degree of compensation necessary is higher, for example, as the measured quality is lower.

[0034] When it is determined that compensation for the first optical signal is not necessary (NO in step S104), the first transmitting unit 16 transmits the first optical signal received by the first receiving unit 11 without compensation (step S105), and ends the processing. Here, the first transmitting unit 16 may wavelength-convert the first optical signal received by the first receiving unit 11 and transmit it.

[0035] On the other hand, when it is determined that compensation for the first optical signal is necessary (YES in step S103), the first compensating unit 14 compensates the first optical signal based on the measurement result of the quality of the first optical signal measured by the measuring unit 13 (step S106). Here, the first compensating unit 14 may perform a higher level of compensation, for example, the lower the measured quality. Note that each compensation process may be a compensation process in which the higher the level of compensation, the more complex the processing content and therefore the greater the power consumption and processing delay.

[0036] Next, the first transmitting unit 16 wavelength-converts the first optical signal compensated by the first compensating unit 14 and transmits the converted first optical signal (step S107), thereby completing the process. Here, the first transmitting unit 16 transmits the first optical signal at a second wavelength that is different from the first wavelength of the first optical signal received by the first receiving unit 11.

[0037] <Configuration of Optical Repeater 10> Next, a more detailed configuration of the optical repeater 10 according to the embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of a more detailed configuration of the optical repeater 10 according to the embodiment. In the example of Fig. 5, the optical repeater 10 includes one or more optical fibers 201, optical amplifiers (optical amplifiers, optical AMP) 202A, optical amplifiers 202B, optical switches (WSS, Wavelength Selective Switch) 203, optical amplifiers 204A, optical amplifiers 204B, optical switches 205A, optical switches 205B, one or more wavelength converters 206, one or more optical fibers 207, and a controller 208.

[0038] The optical amplifier 202 of the optical repeater 10 compensates for the transmission loss of the optical signal input from the optical fiber 201 on a fiber-by-fiber basis. The optical switch 203 switches the optical signal from the optical amplifier 202 on a wavelength-by-wavelength basis and outputs the signal to, for example, an optical amplifier 204A.

[0039] The optical amplifier 204 compensates for loss of the optical signal from the wavelength conversion port of the optical switch 203 and outputs the signal to the optical switch 205A. The optical switch 205A separates the optical signal in fiber units from the optical amplifier 204A into wavelength units and outputs the separated signals to the wavelength converter 206.

[0040] The wavelength converter 206 converts the optical signal of the first wavelength from the optical switch 205A into an electrical signal, performs analog signal processing such as analog compensation on the electrical signal, and then converts it into an optical signal of the second wavelength and outputs it to the optical switch 205B. The wavelength converter 206 converts the optical signal into an electrical signal, but performs only analog signal processing on it, then converts it back into an optical signal of a different wavelength and relays it. While analog delays physically occur in the electrical circuit, they are negligibly small, at most a few nanoseconds. Therefore, compared to wavelength conversion using digital signal processing, it is possible to achieve a wavelength conversion function with low latency on a channel-by-channel basis.

[0041] Here, the wavelength converter 206 may perform analog compensation such as bandwidth compensation, PDL compensation (polarization dependent loss compensation), dispersion compensation, etc. Note that, since the same wavelength cannot be used within an optical fiber, optical signals arriving at the optical repeater 10 but on different routes cannot be accommodated in the same optical fiber. Therefore, the optical repeater 10 converts the wavelength of an optical signal on a certain route from a first wavelength to a second wavelength using the wavelength converter 206, so that the optical signal on that route converted to the second wavelength and an optical signal on another route with the first wavelength can be accommodated in the same optical fiber.

[0042] The optical switch 205B bundles the optical signals in wavelength units from the wavelength converter 206 in fiber units and outputs them to the optical amplifier 204B.

[0043] The optical amplifier 204B compensates for loss in the optical signal from the optical switch 205B and outputs the signal to the optical switch 203. The optical switch 203 receives the optical signal on a fiber-by-fiber basis from the optical amplifier 204B, performs switching on a wavelength-by-wavelength basis, and outputs the signal to the optical amplifier 202B. The optical amplifier 202B compensates for transmission loss in the optical signal from the optical switch 203 on a fiber-by-fiber basis, and outputs the signal to the optical fiber 207. The optical fiber 207 outputs the optical signal on a fiber-by-fiber basis from the optical amplifier 202B to another optical repeater 10. The controller 208 controls each device (e.g., the optical switch 203) within the optical repeater 10.

[0044] <<Configuration of Wavelength Converter 206>> Next, the configuration of the wavelength converter 206 according to the embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the configuration of the wavelength converter 206 according to the embodiment.

[0045] 6, the wavelength conversion device 206 has wavelength conversion units 2061 to 206N (N is an integer of 2 or more) and a measurement unit 13. The following mainly describes the wavelength conversion unit 2061 as an example, but the wavelength conversion units 2062 to 206N may also have the same configuration as the wavelength conversion unit 2061. Therefore, the second compensation unit 15 may have the same configuration as the first compensation unit 14. Note that the following processes and configurations can be used in appropriate combination.

[0046] The wavelength converter 2061 includes a coherent receiver front end 110, a first compensation unit 14, and a coherent transmitter front end 120. The wavelength converter 206N includes a coherent receiver front end 110A, a second compensation unit 15, and a coherent transmitter front end 120A.

[0047] The coherent receiving front end 110 is an example of the first receiving unit 11. The coherent transmitting front end 120 is an example of the first transmitting unit 16. The coherent receiving front end 110A is an example of the second receiving unit 12. The coherent transmitting front end 120A is an example of the second transmitting unit 17.

[0048] 6, the measurement unit 13 includes a selector 131, an A / D converter 132, a buffer memory 133, a demodulator 134, and a control unit 135. The control unit 135 controls the selector 131 and the demodulator 134.

[0049] The selector 131 selects an optical signal of one wavelength from the optical signals of each wavelength of the coherent receiving front ends of the wavelength converters 2061 to 206N based on an instruction from the control unit 135 and outputs the optical signal of one wavelength to the A / D converter 132 .

[0050] The buffer memory 133 temporarily records the optical signal data digitized by the A / D converter 132. The demodulator 134 performs error detection based on the data of each optical signal recorded in the buffer memory 133, and calculates the quality of each optical signal.

[0051] The first compensating unit 14 may determine compensation parameters for the first optical signal based on parameters obtained when the demodulator 134 (measurement unit 13) performs error detection to measure the quality of the first optical signal. In this case, the first compensating unit 14 may determine compensation parameters for the first optical signal using parameters obtained by analog compensation such as bandwidth compensation, PDL compensation (polarization dependent loss compensation), and dispersion compensation. The first compensating unit 14 may also determine compensation parameters for the first optical signal using parameters obtained by a digital compensator such as skew compensation, chromatic dispersion compensation, and polarization dispersion compensation. The first compensating unit 14 may also perform error correction and symbol mapping using data calculated by the demodulator 134 (e.g., data for symbol mapping and data for error detection).

[0052] The first compensation unit 14 may also determine a compensation process according to the quality of the first optical signal measured by the demodulator 134 (measurement unit 13). In this case, the first compensation unit 14 may perform a higher level of compensation as the quality calculated by the demodulator 134 (measurement unit 13) becomes lower. Note that each compensation process may be a compensation process in which the higher the level of compensation, the more complex the processing content and therefore the greater the power consumption and processing delay. In this case, the first compensation unit 14 may perform the first compensation process, for example, when the calculated quality is equal to or greater than a first threshold. The first compensation unit 14 may perform the second compensation process, for example, when the calculated quality is less than the first threshold and equal to or greater than a second threshold that is lower than the first threshold. The first compensation unit 14 may perform the third compensation process, for example, when the calculated quality is less than the second threshold and equal to or greater than a third threshold that is lower than the second threshold. The first compensation unit 14 may perform the fourth compensation process, for example, when the calculated quality is less than the third threshold. In this case, the first compensation process may be, for example, waveform distortion compensation. The second compensation process may be, for example, waveform distortion compensation and polarization separation (polarization dispersion) compensation. The third compensation process may be, for example, waveform distortion compensation, polarization separation compensation, and carrier phase compensation. The fourth compensation process may be, for example, waveform distortion compensation, polarization separation compensation, carrier phase compensation, and error detection and correction.

[0053] Furthermore, the first compensation unit 14 may compensate for the quality of the optical signal in accordance with the signal characteristics between the input of the coherent receiver front-end 110 and the output of the coherent transmitter front-end 120. In this case, data indicating the signal characteristics may be stored in advance in a storage device inside the wavelength converter 206, for example.

[0054] (Example of Analog Compensation) The first compensating unit 14 may perform compensation (analog compensation) on an analog electrical signal converted from an optical signal between the input of the coherent receiver front end 110 and the output of the coherent transmitter front end 120. In this case, the first compensating unit 14 may include, for example, an analog compensator including at least one of skew compensation, spectral compensation, and IQ imbalance compensation. In this case, the first compensating unit 14 may perform skew compensation using, for example, at least one of a phase shifter and an analog FIR (Finite Impulse Response) filter. Alternatively, the first compensating unit 14 may perform spectral compensation using, for example, an analog FIR filter. Alternatively, the first compensating unit 14 may perform IQ imbalance compensation using, for example, an FIR / DRV amplifier.

[0055] (Example of Digital Compensation) The first compensator 14 may perform compensation (digital compensation) on digital data converted from an optical signal between the input of the coherent receiver front end 110 and the output of the coherent transmitter front end 120. In this case, the first compensator 14 may include, for example, a digital compensator that performs at least one of skew compensation, chromatic dispersion compensation, and polarization dispersion compensation. In this case, an A / D converter is provided between the coherent receiver front end 110 and the selector 131 instead of the A / D converter 132 in FIG. 6 .

[0056] <<Configurations of the Coherent Receiving Front End 110 and the Coherent Transmitting Front End 120>> Next, configurations of the coherent receiving front end 110 and the coherent transmitting front end 120 according to the embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a diagram showing an example of the configuration of the coherent receiving front end 110 according to the embodiment. Fig. 8 is a diagram showing an example of the configuration of the coherent transmitting front end 120 according to the embodiment.

[0057] The coherent receiver front end 110 converts the optical signal into an electrical signal, performs coherent detection, and outputs the generated analog electrical signal SA1 by coherently detecting the input optical signal SO1 based on the local oscillator light r1.

[0058] The coherent transmission front end 120 converts the electrical signal into an optical signal and performs coherent modulation. The coherent transmission front end 120 coherently modulates an analog electrical signal SA2, which is a return of the analog electrical signal SA1, based on the transmitted light r2, and outputs the generated output optical signal SO2.

[0059] The input optical signal SO1 and the output optical signal SO2 are phase-modulated and polarization-multiplexed optical signals. The analog electrical signals SA1 and SA2 are four-lane (4-channel) signals including an XI signal for the I component (in-phase component) of the X polarization, an XQ signal for the Q component (quadrature component) of the X polarization, a YI signal for the I component of the Y polarization, and a YQ signal for the Q component of the Y polarization.

[0060] The frequency of the local light r1 is the frequency (carrier frequency) of the input optical signal SO1 to be received, and the frequency of the transmitted light r2 is the frequency of the output optical signal SO2 to be transmitted. For example, the local light r1 and the transmitted light r2 have different frequencies, but they may also have the same frequency. By changing the frequencies of the local light r1 and the transmitted light r2, the wavelength of the returned optical signal can be switched. In other words, the input optical signal SO1 can be converted into an output optical signal SO2 with a different wavelength.

[0061] The wavelength conversion device 206 may include a reference light source 140 that generates a local light beam r1 and a transmission light source 150 that generates a transmission light beam r2. The reference light source 140 may be located inside the coherent receiver front end 110, and the transmission light source 150 may be located inside the coherent transmitter front end 120.

[0062] In the example of FIG. 7, the coherent receiving front end 110 includes a polarization separator 111, 90-degree hybrid circuits 112-1 to 112-2, O / E converters 113-1 to 113-4, and amplifiers 114-1 to 114-4.

[0063] The polarization separator 111 separates the input optical signal SO1, which is an input polarization composite signal, into X-polarized and Y-polarized waves. The 90-degree hybrid circuits (coherent optical detectors) 112-1 to 112-2 perform coherent detection by causing the optical signal separated by the polarization separator 111 to interfere with the local light r1 of the reference light source 140, and the O / E converters 113-1 to 113-4, which are composed of photodiodes or the like, convert the detected signals into four-lane analog electrical signals. The 90-degree hybrid circuit 112-1 separates the X-polarized wave of the input optical signal SO1 into an I component and a Q component, and then the O / E converters 113-1 to 113-2 perform photoelectric conversion to generate XI signals and XQ signals. The 90-degree hybrid circuit 112-2 separates the Y polarization of the input optical signal SO1 into an I component and a Q component, and then O / E converters 113-3 to 113-4 perform photoelectric conversion to generate a YI signal and a YQ signal. Amplifiers 114-1 to 114-4 amplify the generated XI signal, XQ signal, YI signal, and YQ signal, respectively, and output them as a four-lane analog electrical signal SA1 to the first compensation unit 14. The first compensation unit 14 performs analog signal processing or digital signal processing on all or some of the XI signal, XQ signal, YI signal, and YQ signal (X polarization or Y polarization).

[0064] In the example of FIG. 8, the coherent transmission front end 120 includes amplifiers 121-1 to 121-4, MZM (Mach-Zehnder Modulators) 122-1 to 122-4, and a polarization combining unit 123.

[0065] The amplifiers 121-1 to 121-4 respectively amplify the XI signal, XQ signal, YI signal, and YQ signal of the analog electrical signal SA2 output from the first compensation unit 14 directly or via an A / D converter, and drive the MZ modulators 122-1 to 122-4. The MZ modulators (IQ optical modulators) 122-1 to 122-4 apply IQ modulation to the transmitted light r2 from the transmitting light source 150 in accordance with the XI signal, XQ signal, YI signal, and YQ signal applied thereto, respectively. The MZ modulators 122-1 to 122-2 generate X-polarized IQ-modulated optical signals based on the XI signal and XQ signal transmitted via the amplifiers 121-1 to 121-2. The MZ modulators 122-3 to 122-4 generate Y-polarized IQ-modulated optical signals based on the YI signal and YQ signal transmitted via the amplifiers 121-3 to 121-4. The polarization combiner 123 polarization-combines the generated X-polarized IQ-modulated optical signal and Y-polarized IQ-modulated optical signal, and outputs the combined optical signal as an output optical signal SO2.

[0066] <<First Modification of the Configuration of the Wavelength Converter 206>> Next, another example of the configuration of the wavelength converter 206 according to the embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of the configuration of the wavelength converter 206 according to the embodiment. In the example of Fig. 6, an example has been described in which an analog electrical signal converted from an optical signal, or digital data converted from an optical signal, is input to the measurement unit 13.

[0067] 9 will be described as an example in which light of an optical signal is input to the measurement unit 13. This allows for easier implementation even when the types (analog compensator or digital compensator) of the compensation units (e.g., the first compensation unit 14 and the second compensation unit 15) included in the wavelength conversion units 2061 to 206N are different.

[0068] In the example of Fig. 9, the same components as those in the example of Fig. 6 are assigned the same reference numerals, and redundant explanations will be omitted. The following mainly describes the differences between the example of Fig. 9 and the example of Fig. 6. The example of Fig. 9 differs from the example of Fig. 6 in that the measurement unit 13 has an optical switch 136 and a coherent receiver front end 110B instead of the selector 131.

[0069] The optical switch 136 outputs one or more optical signals selected from the optical signals input to each of the wavelength converters 2061 to 206N to the coherent receiver front end 110B based on an instruction from the control unit 135. The coherent receiver front end 110B converts the input optical signals into electrical signals and outputs them to the A / D converter 132.

[0070] <<Second Modification of the Configuration of the Wavelength Converter 206>> Next, another example of the configuration of the wavelength converter 206 according to the embodiment will be described with reference to Fig. 10. Fig. 10 is a diagram showing an example of the configuration of the wavelength converter 206 according to the embodiment. In the example of Fig. 9, an example was described in which light of one or more optical signals selected from the optical signals input to each of the wavelength converters 2061 to 206N is input to the measurement unit 13.

[0071] 10 will explain an example in which light of one or more optical signals selected from the optical signals output from each of the wavelength conversion units 2061 to 206N is input to the measurement unit 13. This allows for easier implementation, for example, as in the example of FIG. 9, even if the types (analog compensator or digital compensator) of the compensation units (for example, the first compensation unit 14 and the second compensation unit 15) included in the wavelength conversion units 2061 to 206N are different.

[0072] In the example of Fig. 10, the same components as those in Fig. 6 are assigned the same reference numerals, and redundant explanations will be omitted. The following mainly describes the differences between the example of Fig. 10 and the example of Fig. 6. The example of Fig. 10 differs from the example of Fig. 6 in that the measurement unit 13 has an optical switch 137 and a coherent receiver front end 110C instead of the selector 131.

[0073] The optical switch 137 outputs one or more optical signals selected from the optical signals output from each of the wavelength converters 2061 to 206N to the coherent receiver front end 110C based on an instruction from the control unit 135. The coherent receiver front end 110C converts the input optical signals into electrical signals and outputs them to the A / D converter 132.

[0074] <<Third Modification of the Configuration of the Wavelength Converter 206>> Next, another example of the configuration of the wavelength converter 206 according to the embodiment will be described with reference to Fig. 11. Fig. 11 is a diagram showing an example of the configuration of the wavelength converter 206 according to the embodiment.

[0075] 11 illustrates an example in which the receiving unit that receives an optical signal is switched based on the quality of the optical signal measured by the measuring unit 13. This allows the use of a more appropriate compensator, for example, when the types (analog compensator or digital compensator) of the compensation units (e.g., the first compensator 14 and the second compensator 15) included in the wavelength conversion units 2061 to 206N are different.

[0076] In the example of Fig. 11, the same components as those in Fig. 6 are denoted by the same reference numerals, and redundant explanations will be omitted. The following mainly describes the differences between the example of Fig. 11 and the example of Fig. 6.

[0077] 11 , the measurement unit 13 transmits information indicating the quality of each optical signal to the management device 20. Then, the management device 20 selects a wavelength conversion unit from among the wavelength conversion units 2061 to 206N that has a compensation unit suitable for compensating for the optical signal, based on the quality of the optical signal measured by the measurement unit 13. In this case, the management device 20 may select a wavelength conversion unit that has a compensation unit that can provide a higher level of compensation as the quality of the optical signal decreases.

[0078] The management device 20 then transmits, for example, a command indicating the wavelength conversion unit to which the optical signal is to be sent to the optical switch 205A. Based on the received command, the optical switch 205A switches the receiving unit that receives the optical signal from, for example, the first receiving unit 11 to another receiving unit (for example, the second receiving unit 12) that is available (not receiving the optical signal).

[0079] <Hardware Configuration of Measurement Unit 13> Fig. 12 is a diagram showing an example of the hardware configuration of the computer 100 of the measurement unit 13 (control unit 135) according to the embodiment. In the example of Fig. 12, the computer 100 includes a processor 101, a memory 102, and a communication interface 103. These units may be connected via a bus or the like. The memory 102 stores at least a part of a program 104. The communication interface 103 includes an interface required for communication with other network elements.

[0080] When the program 104 is executed by the processor 101, memory 102, and other components in cooperation with each other, the computer 100 performs at least some of the processing of the embodiments of the present disclosure. The memory 102 may be of any type suitable for a local technology network. The memory 102 may be, by way of non-limiting example, a non-transitory computer-readable storage medium. The memory 102 may also be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. While only one memory 102 is shown in the computer 100, several physically distinct memory modules may be present in the computer 100. The processor 101 may be of any type. The processor 101 may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and, by way of non-limiting example, a processor based on a multi-core processor architecture. The computer 100 may have multiple processors, such as application-specific integrated circuit chips time-slaved to a clock that synchronizes the main processor.

[0081] Embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device.

[0082] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as instructions included in program modules, that execute on a target real or virtual processor or device to perform the processes or methods of the present disclosure. Program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or divided among program modules as desired in various embodiments. The machine-executable instructions of the program modules may be executed in local or distributed devices. In a distributed device, the program modules may be located in both local and remote storage media.

[0083] The program code for executing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus. When the program code is executed by the processor or controller, the functions / acts in the flowcharts and / or implementing block diagrams are performed. The program code may be executed entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine, or entirely on a remote machine or server.

[0084] The program can be stored and supplied to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible recording media. Examples of non-transitory computer-readable media include magnetic recording media, magneto-optical recording media, optical disk media, and semiconductor memory. Magnetic recording media include, for example, flexible disks, magnetic tapes, and hard disk drives. Magneto-optical recording media include, for example, magneto-optical disks. Optical disk media include, for example, Blu-ray discs, CD (Compact Disc)-ROM (Read Only Memory), CD-R (Recordable), and CD-RW (Rewritable). Semiconductor memory includes, for example, solid-state drives, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, and RAM (Random Access Memory). The program may also be supplied to a computer by various types of temporary computer-readable media. Examples of temporary computer-readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire or an optical fiber, or via a wireless communication path.

[0085] <Others> In optical communication networks such as core / metro networks that transmit large volumes of data, optical communications are connected between multiple ring networks using WSSs (Wavelength Selective Switches). The WSSs output input wavelength division multiplexing (WDM) signals to different output ports for each wavelength.

[0086] When connecting multiple nodes in an optical communication network, optical signals containing the same wavelength cannot be transmitted over the same optical fiber. Therefore, the wavelength is shifted in the optical repeater. When a received optical signal of a certain wavelength is converted into a digital signal, and after error detection and correction and signal quality monitoring are performed, the digital signal is reconverted into an optical signal of a different wavelength and relayed, issues arise in terms of power consumption and processing delays.

[0087] For this reason, for example, a method (analog wavelength conversion method) is being considered in which an optical signal of a certain wavelength is converted to an optical signal of another wavelength without converting it to a digital signal. Also, a method (digital wavelength conversion method) is being considered in which an optical signal of a certain wavelength is converted to a digital signal and then reconverted to an optical signal of a different wavelength without performing digital signal processing such as error detection and correction. These methods can reduce power consumption and processing delays because they do not perform digital signal processing such as error detection and correction. However, because these methods do not perform error detection, they cannot monitor signal quality based on error detection.

[0088] On the other hand, according to the present disclosure, for example, the quality of each optical signal is monitored intermittently, so that error detection can be performed while reducing power consumption and processing delay, thereby enabling appropriate transmission of optical signals.

[0089] <Modifications> The optical repeater 10 may be a device contained in a single housing, but the optical repeater 10 of the present disclosure is not limited to this. The control unit 135 of the optical repeater 10 and the like may be realized by cloud computing configured with one or more computers, for example. The optical repeater 10 and the management device 20 may be configured as an integrated device. The management device 20 may also perform at least some of the processing of each functional unit, such as the control unit 135 of the optical repeater 10. Such optical repeaters 10 are also included as examples of the "optical repeater" of the present disclosure.

[0090] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention.

[0091] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes. (Supplementary Note 1) An optical repeater comprising: a first receiving unit that receives a first optical signal; a second receiving unit that receives a second optical signal; a measuring unit that sequentially measures the quality of the first optical signal and the quality of the second optical signal; a first compensating unit that compensates the first optical signal based on the quality of the first optical signal measured by the measuring unit; a second compensating unit that compensates the second optical signal based on the quality of the second optical signal measured by the measuring unit; a first transmitting unit that transmits the wavelength-converted first optical signal; and a second transmitting unit that transmits the wavelength-converted second optical signal. (Supplementary Note 2) The optical repeater according to Supplementary Note 1, wherein the measuring unit determines a frequency at which the quality of the first optical signal is measured based on the measured quality of the first optical signal. (Supplementary Note 3) The optical repeater according to Supplementary Note 2, wherein the measurement unit measures the quality of the first optical signal at a first frequency when the measured quality of the first optical signal is a first quality, and measures the quality of the first optical signal at a second frequency higher than the first frequency when the measured quality of the first optical signal is a second quality lower than the first quality. (Supplementary Note 4) The optical repeater according to Supplementary Note 1, wherein the measurement unit determines the frequency at which to measure the quality of the first optical signal based on an elapsed time of communication using the first optical signal. (Supplementary Note 5) The optical repeater according to Supplementary Note 4, wherein the measurement unit measures the quality of the first optical signal at a third frequency when the elapsed time of communication using the first optical signal is a first elapsed time, and measures the quality of the first optical signal at a fourth frequency lower than the third frequency when the elapsed time of communication using the first optical signal is a second elapsed time longer than the first elapsed time. (Supplementary Note 6) The optical repeater according to Supplementary Note 1, wherein the first compensator determines a parameter for compensation of the first optical signal based on a parameter when the measurement unit performs error detection for measuring quality. (Supplementary Note 7) The optical repeater according to Supplementary Note 1, wherein the first compensator determines a compensation process according to the quality of the first optical signal measured by the measurement unit. (Supplementary Note 8) The optical repeater according to Supplementary Note 1, wherein the first compensator has an analog compensator that includes at least one of skew compensation, spectrum compensation, and IQ imbalance compensation.(Supplementary Note 9) The optical repeater according to Supplementary Note 1, wherein the first compensator has a digital compensator that performs at least one of skew compensation, chromatic dispersion compensation, and polarization dispersion compensation. (Supplementary Note 10) An optical communication system comprising an optical repeater and a management device, wherein the optical repeater comprises: a first receiving unit that receives a first optical signal; a second receiving unit that receives a second optical signal; a measurement unit that sequentially measures a quality of the first optical signal and a quality of the second optical signal; a first compensator that compensates the first optical signal based on the quality of the first optical signal measured by the measurement unit; a second compensator that compensates the second optical signal based on the quality of the second optical signal measured by the measurement unit; a first transmitting unit that transmits the wavelength-converted first optical signal; and a second transmitting unit that transmits the wavelength-converted second optical signal, and the management device switches the receiving unit that receives the first optical signal from the first receiving unit to the second receiving unit based on the quality of the first optical signal measured by the measurement unit. a second transmitting unit that transmits the wavelength-converted second optical signal. (Supplementary Note 11) A wavelength conversion device comprising: a first receiving unit that receives a first optical signal; a second receiving unit that receives a second optical signal; a measuring unit that sequentially measures a quality of the first optical signal and a quality of the second optical signal; a first compensating unit that compensates the first optical signal based on the quality of the first optical signal measured by the measuring unit; a second compensating unit that compensates the second optical signal based on the quality of the second optical signal measured by the measuring unit; a first transmitting unit that transmits the wavelength-converted first optical signal; and a second transmitting unit that transmits the wavelength-converted second optical signal. (Supplementary Note 12) An optical repeating method comprising: receiving a first optical signal by a first receiving unit; receiving a second optical signal by a second receiving unit; sequentially measuring the quality of the first optical signal and the quality of the second optical signal; compensating the first optical signal based on the measured quality of the first optical signal and transmitting the wavelength-converted first optical signal; and compensating the second optical signal based on the measured quality of the second optical signal and transmitting the wavelength-converted second optical signal.

[0092] 1 Optical communication system 10, 10A to 10G Optical repeater 11 First receiving unit 12 Second receiving unit 13 Measuring unit 14 First compensating unit 15 Second compensating unit 16 First transmitting unit 17 Second transmitting unit 20 Management device 131 Selector 132 A / D converter 133 Buffer memory 134 Demodulator 135 Control unit 136 Optical switch 137 Optical switch 206 Wavelength conversion device 2061 to 206N Wavelength conversion unit

Claims

1. a first receiving unit that receives a first optical signal; a second receiving unit that receives a second optical signal; a measurement unit that sequentially measures the quality of the first optical signal and the quality of the second optical signal; a first compensation unit that compensates the first optical signal based on the quality of the first optical signal measured by the measurement unit; a second compensation unit that compensates for the second optical signal based on the quality of the second optical signal measured by the measurement unit; a first transmitter that transmits the wavelength-converted first optical signal; a second transmitter that transmits the wavelength-converted second optical signal; An optical repeater device having the same.

2. the measurement unit determines a frequency for measuring the quality of the first optical signal based on the measured quality of the first optical signal.

2. The optical repeater according to claim 1.

3. the measurement unit measures the quality of the first optical signal at a first frequency when the measured quality of the first optical signal is a first quality, and measures the quality of the first optical signal at a second frequency when the measured quality of the first optical signal is a second quality lower than the first quality, 3. The optical repeater according to claim 2.

4. the measurement unit determines a frequency for measuring the quality of the first optical signal based on an elapsed time of communication using the first optical signal.

2. The optical repeater according to claim 1.

5. the measurement unit measures the quality of the first optical signal at a third frequency when an elapsed time of communication using the first optical signal is a first elapsed time; when an elapsed time of communication using the first optical signal is a second elapsed time that is longer than the first elapsed time, measuring the quality of the first optical signal at a fourth frequency that is lower than the third frequency; 5. The optical repeater according to claim 4.

6. the first compensation unit determines a compensation parameter for the first optical signal based on a parameter used when the error detection for measuring quality is performed by the measurement unit; 2. The optical repeater according to claim 1.

7. the first compensation unit determines a compensation process according to the quality of the first optical signal measured by the measurement unit; 2. The optical repeater according to claim 1.

8. the first compensation unit has an analog compensator including at least one of skew compensation, spectrum compensation, and IQ imbalance compensation; 2. The optical repeater according to claim 1.

9. the first compensation unit has a digital compensator that performs at least one of skew compensation, chromatic dispersion compensation, and polarization dispersion compensation; 2. The optical repeater according to claim 1.

10. receiving a first optical signal at a first receiving unit; receiving the second optical signal at a second receiving unit; measuring the quality of the first optical signal and the quality of the second optical signal in sequence; Compensating the first optical signal based on the measured quality of the first optical signal and transmitting the wavelength-converted first optical signal; compensating the second optical signal based on the measured quality of the second optical signal, and transmitting the wavelength-converted second optical signal; Optical relay method.

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