Optical wavelength multiplexing transmission device and optical wavelength multiplexing transmission system

Abstract

To provide an optical wavelength multiplexing transmission device, or the like, capable of compensating an SRS tilt at high speed in a multiband system.SOLUTION: An optical wavelength multiplexing transmission device 2A includes: a control unit 18; a correction coefficient calculation unit 80 including an acquisition unit 81, a generated tilt amount calculation unit 82, an estimation calculation unit 83, a coefficient calculation unit 84, and an update unit 85. The control unit is configured to calculate a compensation amount by using an optical power value and a predetermined calculation expression for each wavelength band, and compensate a tilt of a wavelength multiplexing signal based on the compensation amount. The acquisition unit is configured to acquire transmission line characteristics that indicates an optical power value in each wavelength band for each transmission distance of the transmission line. The generated tilt amount calculation unit is configured to calculate a generated tilt amount of the transmission line, based on the transmission line characteristics. The estimation calculation unit is configured to calculate an estimated compensation amount to compensate the tilt of the wavelength multiplexing signal, by using the generated tilt amount of the transmission line and the predetermined calculation expression. The coefficient calculation unit is configured to calculate a correction coefficient to correct the predetermined calculation expression, based on the estimated compensation amount and the compensation amount calculated in the calculation unit. The update unit is configured to update the correction coefficient.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical wavelength multiplexing transmission device and an optical wavelength multiplexing transmission system Regarding. [Background technology]

[0002] In recent years, for example, for high-speed, large-capacity communications, optical wavelength division multiplexing (WDM) transmission systems have become known, which multiplex and transmit optical signals of multiple wavelengths. Furthermore, to expand transmission capacity, multi-band systems using multiple optical wavelength bands, such as the C-band (Conventional Band) and the L-band (Long Band), have become known. The C-band is an optical wavelength band, for example, from 1530 nm to 1565 nm. The L-band is an optical wavelength band, for example, from 1565 nm to 1625 nm. In WDM transmission systems, a large power deviation (tilt) occurs between the short-wavelength side and the long-wavelength side during optical fiber transmission due to, for example, wavelength-dependent loss (WDL) and stimulated Raman scattering (SRS). As a result, for example, the optical power of the short-wavelength optical signal decreases, degrading the signal quality on the receiving side. Therefore, tilt compensation is required to suppress the degradation of signal quality on the receiving side.

[0003] However, in a multi-band system, the wider the optical wavelength band used, the larger the tilt that occurs between the shortest and longest wavelengths of the transmitted optical signal becomes compared to a single-band system that uses only a single optical wavelength band. For example, tilt due to WDL depends on the characteristics of the optical fiber in the transmission path, and is not dependent on the number of wavelengths, which fluctuates during operation, so the amount of tilt can be estimated and compensated for relatively easily. In contrast, tilt due to SRS depends on the number of wavelengths, which fluctuates during operation, so tilt compensation according to the number of wavelengths is required.

[0004] Therefore, a known tilt compensation technique for multiband systems is to monitor the spectrum of the signal wavelength at the receiving WDM device, feed back the monitoring results to the transmitting WDM device, and then compensate for the tilt at the transmitting WDM device based on the monitoring results.This method can achieve high-precision tilt compensation according to the number of wavelengths that changes during operation, as well as tilt that occurs in the transmission path between the receiving WDM device and the transmitting WDM device.

[0005] However, because the transmitting WDM device receives the monitoring results from the receiving WDM device, it takes time to perform tilt compensation. For example, if the number of wavelengths changes suddenly due to an optical fiber break or equipment failure, tilt compensation may not be completed in time, and signal errors may occur due to deterioration of signal quality on the receiving side.

[0006] Another method for achieving high-speed tilt compensation is to monitor the input power of a WDM signal input to a transmission amplifier in a WDM device and compensate for the tilt within the WDM signal based on the input power. However, while this method can compensate for tilt within WDM signals in the same optical wavelength band, it cannot compensate for SRS tilt that occurs between WDM signals in different optical wavelength bands in a multi-band system. Therefore, the present applicant has proposed a WDM device that can compensate for SRS tilt in a multi-band system quickly and with high accuracy.

[0007] The WDM device includes a demultiplexing unit, a detecting unit, a first compensating unit, a second compensating unit, and a multiplexing unit. The demultiplexing unit demultiplexes optical wavelength multiplexed signals for each optical wavelength band from a multiplexed signal containing optical wavelength multiplexed signals of multiple optical wavelength bands. The detecting unit detects the power value of each optical wavelength multiplexed signal for each optical wavelength band. The first compensating unit compensates for tilt in the optical wavelength multiplexed signal for each optical wavelength band based on the power value for each optical wavelength band. The second compensating unit compensates for the power of the optical wavelength multiplexed signal for each optical wavelength band based on the power value for each optical wavelength band to reduce the power difference between the optical wavelength multiplexed signals after tilt compensation. The multiplexing unit multiplexes the optical wavelength multiplexed signals after power compensation and outputs a multiplexed signal. As a result, SRS tilt can be compensated for quickly and accurately in a multi-band system. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-17451 [Patent Document 2] Japanese Patent Application Publication No. 2019-16986 [Patent Document 3] Japanese Patent Application Publication No. 2019-186735 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the amount of tilt compensation for the SRS tilt in high-speed tilt control is calculated using values ​​pre-designed for the assumed transmission path conditions (fiber type, loss coefficient, e.g., lamp loss, which is the loss at the connection point between the optical transmission device and the optical fiber). Therefore, the control error of the tilt compensation amount increases depending on the transmission path conditions (the magnitude of connector loss and loss coefficient).

[0010] For example, if the power on the short wavelength side is increased too much, increasing nonlinear effects, signal quality will deteriorate. Also, if the power on the long wavelength side is reduced too much, degrading the OSNR (Optical Signal to Noise Ratio), signal quality will also deteriorate. In particular, in the C-band and L-band transmissions that will become mainstream in the future, the bandwidth of the signal light will expand and the number of wavelengths will increase. As a result, the amount of SRS tilt that occurs will also increase, and the impact of control errors in the amount of tilt compensation will become greater.

[0011] Therefore, in order to control the tilt compensation amount optimized for each transmission path actually used, it is necessary to determine the tilt compensation amount suitable for each transmission path when the system is constructed or during system operation. However, at present, it is difficult to directly determine the tilt compensation amount for high-speed SRS tilt compensation.

[0012] It is also possible to transmit multiple wavelengths through optical fiber and observe the power deviation for each wavelength after transmission using a spectrum analyzer, etc. However, this power deviation includes the effects of WDL in addition to SRS, so in order to observe only SRS, it is necessary to devise a way to remove these other effects.

[0013] In one aspect, an object of the present invention is to provide an optical wavelength division multiplexing transmission device or the like that can compensate for SRS tilt quickly and with high precision in a multi-band system. [Means for solving the problem]

[0014] An optical wavelength multiplexing transmission device according to one embodiment includes a demultiplexing unit, a detection unit, a calculation unit, a control unit, a multiplexing unit, an acquisition unit, an occurred tilt amount calculation unit, an estimation calculation unit, a coefficient calculation unit, and an update unit. The demultiplexing unit demultiplexes a wavelength multiplexed signal for each wavelength band from a multiplexed signal including wavelength multiplexed signals of a plurality of wavelength bands. The detection unit detects the optical power value of each wavelength multiplexed signal for each wavelength band. The calculation unit calculates a compensation amount for compensating for tilt of the wavelength multiplexed signal using the optical power value detected by the detection unit and a predetermined calculation formula. The control unit compensates for tilt of the wavelength multiplexed signal based on the compensation amount calculated by the calculation unit. The multiplexing unit combines the wavelength multiplexed signals compensated by the control unit and outputs the combined signals to a transmission path. The acquisition unit acquires transmission path characteristics indicating the optical power value of each wavelength band for each transmission distance of the transmission path. The occurred tilt amount calculation unit calculates the occurred tilt amount of the transmission path based on the transmission path characteristics. The estimation calculation unit calculates an estimated compensation amount for compensating for tilt of the wavelength multiplexed signal using the amount of tilt generated in the transmission path calculated by the generated tilt amount calculation unit and the predetermined calculation formula. The coefficient calculation unit calculates a correction coefficient for correcting the predetermined calculation formula based on the estimated compensation amount calculated by the estimation calculation unit and the current compensation amount calculated by the calculation unit. The update unit updates the correction coefficient calculated by the coefficient calculation unit. [Effects of the Invention]

[0015] In one embodiment, SRS tilt can be compensated for quickly and accurately in a multi-band system. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of a WDM system according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of the table configuration of the first coefficient table. [Figure 3] FIG. 3 is an explanatory diagram showing an example of the table configuration of the second coefficient table. [Figure 4] FIG. 4 is an explanatory diagram illustrating an example of a power profile that is a relationship between a transmission distance and a power detection value in the first embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of the processing operation of the correction coefficient calculation unit in the WDM device related to the first update processing. [Figure 6] FIG. 6 is a flow chart showing an example of the processing operation of the control unit in the WDM device related to the compensation processing. [Figure 7] FIG. 7 is an explanatory diagram illustrating an example of a WDM system according to the second embodiment. [Figure 8] FIG. 8 is an explanatory diagram illustrating an example of a power profile that is a relationship between a transmission distance and a power detection value in the second embodiment. [Figure 9] FIG. 9 is an explanatory diagram showing an example of the relationship between wavelength and the amount of tilt that occurs. [Figure 10] FIG. 10 is a flowchart showing an example of the processing operation of the correction coefficient calculation unit in the WDM device related to the second update processing. [Figure 11] FIG. 11 is an explanatory diagram illustrating an example of a WDM system according to the third embodiment. [Figure 12] FIG. 12 is an explanatory diagram showing an example of the power change tendency in the long wavelength band and the short wavelength band in the third embodiment. [Figure 13] FIG. 13 is a flowchart showing an example of the processing operation of the correction coefficient calculation unit in the WDM device related to the third update processing. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the optical wavelength multiplexing transmission device and optical wavelength multiplexing transmission disclosed in the present application will be described with reference to the drawings. system The following examples will be described in detail. Note that the disclosed technology is not limited to each example. The examples described below may be combined as appropriate within the scope of not causing any contradiction. [Example]

[0018] FIG. 1 is an explanatory diagram illustrating an example of a WDM system according to a first embodiment. The WDM system 1 according to the first embodiment includes a plurality of WDM devices 2, and the WDM devices 2 are connected to each other by an optical fiber 3 serving as a transmission path. The WDM system 1 is a multiband system that multiplexes optical signals of a plurality of optical wavelength bands. The WDM system 1 multiplexes a WDM signal in a first optical wavelength band, for example, a C-band, and a second WDM signal in a second optical wavelength band, for example, an L-band. Each WDM device 2 outputs a WDM signal obtained by multiplexing the first WDM signal in the C-band and the second WDM signal in the L-band to the optical fiber 3, and is also capable of demultiplexing the first WDM signal in the C-band and the second WDM signal in the L-band from the WDM signal received from the optical fiber 3. The WDM system 1 illustrated in FIG. 1 includes, for example, an upstream WDM device 2A and a downstream WDM device 2B.

[0019] 1 includes a demultiplexing unit 11, a first receiving amplifier 12A, a second receiving amplifier 12B, a first WSS (Wavelength Selective Switch) 13A, and a second WSS 13B. The WDM device 2 also includes a first OCM (Optical Channel Monitor) 14A, a second OCM 14B, a first transmitting amplifier 15A, a second transmitting amplifier 15B, a multiplexing unit 16, a first detecting unit 17A, a second detecting unit 17B, and a control unit 18. The WDM device 2 also includes a first optical transmission group 19A, a second optical transmission group 19B, a monitoring control unit 61, and a correction coefficient calculation unit 80.

[0020] The demultiplexing unit 11 demultiplexes the WDM signal into a first WDM signal in the C band and a second WDM signal in the L band, and outputs the first WDM signal to a first receiving amplifier 12A and the second WDM signal to a second receiving amplifier 12B.

[0021] The first receiving amplifier 12A is an optical amplifier that optically amplifies the first WDM signal and outputs the optically amplified first WDM signal to the first WSS 13A. The first WSS 13A is a wavelength selective switch that optically adds an optical signal from the first optical transmission group 19A to the first WDM signal. The first WSS 13A outputs the optically added first WDM signal to the first transmitting amplifier 15A. The first transmitting amplifier 15A is an optical amplifier that tilt-compensates the first WDM signal and power-compensates the tilt-compensated first WDM signal. The first transmitting amplifier 15A then outputs the tilt-compensated and power-compensated first WDM signal to the multiplexer 16.

[0022] The second receiving amplifier 12B is an optical amplifier that optically amplifies the second WDM signal and outputs the optically amplified second WDM signal to the second WSS 13B. The second WSS 13B is a wavelength selective switch that optically adds an optical signal from the second optical transmission group 19B to the second WDM signal. The second WSS 13B outputs the optically added second WDM signal to the second transmitting amplifier 15B. The second transmitting amplifier 15B is an optical amplifier that tilt compensates the second WDM signal and power compensates the tilt-compensated second WDM signal. The second transmitting amplifier 15B then outputs the tilt-compensated and power-compensated second WDM signal to the multiplexer 16.

[0023] The multiplexer 16 multiplexes the first WDM signal from the first transmission amplifier 15A and the second WDM signal from the second transmission amplifier 15B, and outputs the WDM signal to the optical fiber 3 connected by an optical connector (not shown). The first detector 17A is a detector that detects a first power value, which is the output power of the first WDM signal, from the WDM signal output by the multiplexer 16 and transmitted between the multiplexer 16 and the optical fiber 3, and notifies the control unit 18 of the first power value. The second detector 17B is a detector that detects a second power value, which is the output power of the second WDM signal, from the WDM signal output by the multiplexer 16 and transmitted between the multiplexer 16 and the optical fiber 3, and notifies the control unit 18 of the second power value.

[0024] The first transmitting amplifier 15A includes a first preamplifier 21A, a first tilt compensator 22A, a first postamplifier 23A, and a first power compensator 24A. The first preamplifier 21A and the first postamplifier 23A are, for example, erbium-doped fiber amplifiers (EDFAs).

[0025] The first preamplifier 21A optically amplifies the first WDM signal from the first WSS 13A and outputs the optically amplified first WDM signal to the first tilt compensator 22A. The first tilt compensator 22A is a first compensator such as a variable attenuator that compensates for tilt in the first WDM signal in a direction that reduces the amount of tilt. The first tilt compensator 22A can change the gain deviation with respect to wavelength by approximately 1 dB by increasing the tilt by ±1 dB, for example. The first tilt compensator 22A outputs the tilt-compensated first WDM signal to the first postamplifier 23A. The first postamplifier 23A amplifies the tilt-compensated first WDM signal and outputs the amplified first WDM signal to the first power compensator 24A. The first power compensator 24A is a second compensator such as a variable attenuator that power compensates the tilt-compensated first WDM signal. The first power compensator 24A performs power compensation on the entire first WDM signal to reduce the power difference between the first WDM signal and the second WDM signal, and outputs the power-compensated first WDM signal to the multiplexer 16.

[0026] The second transmitting amplifier 15B includes a second preamplifier 21B, a second tilt compensator 22B, a second postamplifier 23B, and a second power compensator 24B. The second preamplifier 21B and the second postamplifier 23B are, for example, erbium-doped fiber amplifiers (EDFAs).

[0027] The second preamplifier 21B optically amplifies the second WDM signal from the second WSS 13B and outputs the optically amplified second WDM signal to the second tilt compensator 22B. The second tilt compensator 22B is a first compensator, such as a variable attenuator, that performs tilt compensation in a direction that reduces the amount of tilt in the second WDM signal. The second tilt compensator 22B can change the gain deviation with respect to wavelength by approximately 1 dB by increasing the tilt by ±1 dB, for example. The second tilt compensator 22B outputs the tilt-compensated second WDM signal to the second postamplifier 23B. The second postamplifier 23B amplifies the tilt-compensated second WDM signal and outputs the amplified second WDM signal to the second power compensator 24B. The second power compensator 24B is a second compensator, such as a variable attenuator, that performs power compensation for the tilt-compensated second WDM signal. The second power compensator 24B performs power compensation on the entire second WDM signal to reduce the power difference between the first WDM signal and the second WDM signal, and outputs the power-compensated second WDM signal to the multiplexer 16.

[0028] The first detector 17A has a PD (Photo Diode) 17A1. The PD 17A1 in the first detector 17A extracts a first WDM signal from the WDM signal output by the multiplexer 16, and detects a first power value by electrically converting the output power of the extracted first WDM signal to the optical fiber 3. The first detector 17A then outputs the detected first power value to a first calculator 42 and a second calculator 43, which will be described later.

[0029] The second detector 17B includes a PD 17B1. The PD 17B1 in the second detector 17B extracts a second WDM signal from the WDM signal output by the multiplexer 16, and detects a second power value by electrically converting the output power of the extracted second WDM signal to the optical fiber 3. The second detector 17B then outputs the detected second power value to a first calculator 42 and a second calculator 43, which will be described later.

[0030] The first OCM 14A is a monitoring unit that monitors the optical power of each wavelength in the first WDM signal from the first WSS 13A and notifies the first WSS 13A of the monitoring results. Based on the monitoring results from the first OCM 14A, the first WSS 13A controls the optical power of each wavelength in the first WDM signal so that the power deviation of each wavelength falls within a predetermined range. Note that the predetermined range is, for example, a range of power deviation that does not affect tilt compensation. As a result, the first WSS 13A inputs the power-controlled first WDM signal to the first transmit amplifier 15A, thereby improving the accuracy of tilt compensation of the first WDM signal performed by the first transmit amplifier 15A.

[0031] The second OCM 14B is a monitoring unit that monitors the optical power of each wavelength in the second WDM signal from the second WSS 13B and notifies the second WSS 13B of the monitoring results. Based on the monitoring results from the second OCM 14B, the second WSS 13B controls the optical power of each wavelength in the second WDM signal so that the power deviation of each wavelength in the second WDM signal falls within a predetermined range. As a result, the second WSS 13B inputs the power-controlled second WDM signal to the second transmit amplifier 15B, thereby improving the accuracy of tilt compensation of the second WDM signal performed by the second transmit amplifier 15B.

[0032] The control unit 18 has a coefficient table 41, a first calculation unit 42, a second calculation unit 43, a first control unit 44, and a second control unit 45. The first calculation unit 42 calculates a first tilt compensation amount to be set in the first tilt compensation unit 22A using a first calculation formula A1, and calculates a second tilt compensation amount to be set in the second tilt compensation unit 22B using a first calculation formula A2. The first control unit 44 controls the first tilt compensation unit 22A based on the first tilt compensation amount, and controls the second tilt compensation unit 22B based on the second tilt compensation amount.

[0033] The second calculation unit 43 uses a second calculation formula B1 to calculate a first power compensation amount to be set in the first power compensation unit 24A, and also uses a second calculation formula B2 to calculate a second power compensation amount to be set in the second power compensation unit 24B. The second control unit 45 controls the first power compensation unit 24A based on the first power compensation amount, and also controls the second power compensation unit 24B based on the second power compensation amount.

[0034] The coefficient table 41 has a first coefficient table 411 and a second coefficient table 412. FIG. 2 is an explanatory diagram showing an example of the table configuration of the first coefficient table 411. The first coefficient table 411 shown in FIG. 2 manages a coefficient 411B and a loss coefficient 411C in association with each fiber type 411A of the optical fiber 3. The first calculation unit 42 acquires the coefficient 411B and the loss coefficient 411C corresponding to the fiber type 411A of the optical fiber from the first coefficient table 411. The first calculation unit 42 calculates a first tilt compensation amount based on the acquired coefficient 411B and loss coefficient 411C, the first power value, the second power value, and a first calculation formula A1. The first tilt compensation amount is a compensation amount for compensating for an SRS tilt in the first WDM signal in the C band. The first calculation unit 42 calculates a second tilt compensation amount based on the acquired coefficient 411B and loss coefficient 411C, the first power value and the second power value, and the first calculation formula A2. The second tilt compensation amount is a compensation amount for compensating for the SRS tilt in the second WDM signal in the L band.

[0035] The second calculation unit 43 acquires a coefficient 411B and a loss coefficient 411C corresponding to the fiber type 411A of the optical fiber 3 from the first coefficient table 411. The second calculation unit 43 calculates a first power compensation amount based on the acquired coefficient 411B and loss coefficient 411C, the first power value and the second power value, and a second calculation formula B1. The first power compensation amount is a compensation amount calculated using the second power value and the loss coefficient of the second WDM signal to compensate for the total optical power difference between the optical wavelength bands generated by SRS. The second calculation unit 43 calculates a second power compensation amount based on the acquired coefficient 411B and loss coefficient 411C, the first power value and the second power value, and a second calculation formula B1. The second power compensation amount is a compensation amount calculated using the first power value and the loss coefficient of the first WDM signal to compensate for the total optical power difference between the optical wavelength bands generated by SRS.

[0036] The first control unit 44 controls the first tilt compensator 22A to reduce the amount of tilt in the first WDM signal based on the first tilt compensation amount, and the first control unit 44 controls the second tilt compensator 22B to reduce the amount of tilt in the second WDM signal based on the second tilt compensation amount.

[0037] The second control unit 45 controls the first power compensator 24A based on the first power compensation amount to reduce the power difference between the first WDM signal and the second WDM signal. The second control unit 45 controls the second power compensator 24B based on the second power compensation amount to reduce the power difference between the first WDM signal and the second WDM signal. As a result, during multiband transmission, the power deviation for each wavelength in multiple optical wavelength bands can be controlled to fall within a predetermined range in the opposing WDM device 2 connected via optical fiber 3.

[0038] The first calculation unit 42 refers to the coefficient table 41 and calculates the first tilt compensation amount using a first calculation formula A1 of (first power value × coefficient a) + (second power value × coefficient b) × K. The first calculation unit 42 also calculates the second tilt compensation amount using a first calculation formula A2 of (second power value × coefficient c) + (first power value × coefficient d) × L. The coefficients a, b, c, and d are loss coefficients for each fiber type that are set in advance when the system is constructed. K and L are first correction coefficients.

[0039] The second calculation unit 43 calculates the first power compensation amount using a second calculation formula B1 of (second power value x coefficient e) x M. The second calculation unit 43 calculates the second power compensation amount using a second calculation formula B2 of (first power value x coefficient f) x N. The coefficients e and f are loss coefficients for each fiber type that are set in advance when the system is constructed. M and N are second correction coefficients.

[0040] 3 is an explanatory diagram showing an example of the table configuration of the second coefficient table 412. The second coefficient table 412 is a table that manages a first correction coefficient K that corrects the first arithmetic formula A1, a first correction coefficient L that corrects the first arithmetic formula A2, a second correction coefficient M that corrects the second arithmetic formula B1, and a second correction coefficient N that corrects the second arithmetic formula B2.

[0041] The correction coefficient calculation unit 80 includes an acquisition unit 81, an induced tilt amount calculation unit 82, an estimation calculation unit 83, a coefficient calculation unit 84, and an update unit 85. The acquisition unit 81 acquires a power profile, which is a transmission line characteristic in the longitudinal direction of the transmission line indicating the optical power value (amount of attenuation) of each wavelength band for each transmission distance of the transmission line, from the downstream WDM device 2B via the monitoring control unit 61. The downstream WDM device 2B has almost the same configuration as the upstream WDM device 2A, but includes a first optical receiving group 20A connected to the first WSS 13A in the downstream WDM device 2B and a second optical receiving group 20B connected to the second WSS 13B in the downstream WDM device 2B. The first optical receiving group 20A receives a first WDM signal wavelength-selected by the first WSS 13A. The second optical receiving group 20B receives a second WDM signal wavelength-selected by the second WSS 13B. The first optical receiving group 20A acquires a power profile from the received first WDM signal and notifies the monitor and control unit 61 in the downstream WDM device 2B of the acquired power profile. Furthermore, the second optical receiving group 20B acquires a power profile from the received second WDM signal and notifies the monitor and control unit 61 in the downstream WDM device 2B of the acquired power profile. Then, the monitor and control unit 61 in the downstream WDM device 2B notifies the upstream WDM device 2A of the power profiles received from the first receiving group and the second receiving group.

[0042] 4 is an explanatory diagram showing an example of a power profile, which is the relationship between the transmission distance and the power detection value in the first embodiment. The acquisition unit 81 acquires, from the downstream WDM device 2B via the monitoring control unit 61, a power profile indicating the optical power value for each transmission distance of an arbitrary wavelength band among a plurality of wavelength bands for each transmission distance of the transmission path, when the system is constructed or when the system is operating stably. Note that, as a technology for acquiring the power profile, for example, the technology disclosed in Japanese Patent Application Laid-Open No. 2018-133725, which is capable of measuring the power profile without affecting the main signal during system operation, may be used. Alternatively, an OTDR (Optical Time Domain Reflectometer) may be used, and the technology may be changed as appropriate.

[0043] The generated tilt amount calculation unit 82 calculates the amount of generated tilt of the transmission line based on the power profile. The generated tilt amount calculation unit 82 calculates the amount of generated tilt for each transmission distance from the power profile of an arbitrary wavelength band, and calculates the amount of generated tilt of the transmission line from the amount of generated tilt for each transmission distance. The generated tilt amount calculation unit 82 calculates the amount of generated tilt for each transmission distance by substituting the power profile into (Equation 1). Note that SRSCoeff_fibertype is the amount of generated tilt at infinite length for each optical fiber type (for example, the amount of generated tilt that occurs when operating with the maximum number of wavelengths in the system), and is stored in advance in memory. FiberLossCoeff_base is the loss coefficient used when calculating SRSCoeff_fibertype. FiberLossCoeff_actual is the loss coefficient of the transmission line actually used, calculated from the measured power profile.

[0044]

number

[0045] The estimation calculation unit 83 calculates an estimated compensation amount for compensating for tilt of the wavelength-multiplexed signal using the amount of tilt generated in the transmission line calculated by the generated tilt amount calculation unit 82 and a predetermined calculation formula. The estimation calculation unit 83 has a first estimation calculation unit 83A and a second estimation calculation unit 83B. The first estimation calculation unit 83A calculates a first tilt estimated compensation amount for compensating for tilt in the wavelength-multiplexed signal using the amount of tilt generated in the transmission line calculated by the generated tilt amount calculation unit 82 and a first calculation formula A1. The first estimation calculation unit 83A calculates a second tilt estimated compensation amount for compensating for tilt in the wavelength-multiplexed signal using the amount of tilt generated in the transmission line calculated by the generated tilt amount calculation unit 82 and a first calculation formula A2. The second estimation calculation unit 83B calculates a first power estimated compensation amount for compensating for power for each wavelength band using the amount of tilt generated in the transmission line calculated by the generated tilt amount calculation unit 82 and a second calculation formula B1. The second estimation calculation unit 83B calculates a second estimated power compensation amount for compensating for the power for each wavelength band using the tilt amount generated in the transmission line calculated by the tilt amount calculation unit 82 and a second calculation formula B2.

[0046] The coefficient calculation unit 84 includes a first coefficient calculation unit 84A and a second coefficient calculation unit 84B. The first coefficient calculation unit 84A calculates a first correction coefficient K for correcting the first calculation formula A1 based on the first estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current first tilt compensation amount calculated by the first calculation unit 42. The current first tilt compensation amount is an actual tilt compensation amount that becomes flat using the first calculation formula A1. The first coefficient calculation unit 84A calculates a first correction coefficient L for correcting the first calculation formula A2 based on the second estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current second tilt compensation amount calculated by the first calculation unit 42. The current second tilt compensation amount is an actual tilt compensation amount that becomes flat using the first calculation formula A2.

[0047] The second coefficient calculation unit 84B calculates a second correction coefficient M for correcting the second calculation formula B1 based on the first estimated power compensation amount calculated by the second estimation calculation unit 83B and the current first power compensation amount calculated by the second calculation unit 43. The current first power compensation amount is the actual power compensation amount that eliminates the deviation using the second calculation formula B1. The second coefficient calculation unit 84B calculates a second correction coefficient N for correcting the second calculation formula B2 based on the second estimated power compensation amount calculated by the second estimation calculation unit 83B and the current second power compensation amount calculated by the second calculation unit 43. The current second power compensation amount is the actual power compensation amount that eliminates the deviation using the second calculation formula B2.

[0048] The update unit 85 updates the correction coefficients calculated by the coefficient calculation unit 84. The update unit 85 has a first update unit 85A and a second update unit 85B. The first update unit 85A updates the first correction coefficients 412A in the second coefficient table 412 using the first correction coefficients K and L calculated by the first coefficient calculation unit 84A. The second update unit 85B updates the second correction coefficients 412B in the second coefficient table 412 using the second correction coefficients M and N calculated by the second coefficient calculation unit 84B.

[0049] When a change in the number of wavelengths occurs due to a fault such as a break in the optical fiber, the first calculation unit 42 calculates a current first tilt compensation amount using the first correction coefficient K stored in the second coefficient table 412 and the first calculation formula A1. The first control unit 44 then controls the first tilt compensator 22A based on the first tilt compensation amount to reduce the amount of tilt in the first WDM signal. When a change in the number of wavelengths occurs, the first calculation unit 42 calculates a current second tilt compensation amount using the first correction coefficient L stored in the second coefficient table 412 and the first calculation formula A2. The first control unit 44 then controls the second tilt compensator 22B based on the second tilt compensation amount to reduce the amount of tilt in the second WDM signal.

[0050] When a change in the number of wavelengths occurs, the second calculation unit 43 calculates a current first power compensation amount using the second correction coefficient M stored in the second coefficient table 412 and the second calculation formula B1. Then, the second control unit 45 controls the first power compensation unit 24A based on the first power compensation amount to reduce the power difference between the first WDM signal and the second WDM signal. When a change in the number of wavelengths occurs, the second calculation unit 43 calculates a current second power compensation amount using the second correction coefficient N stored in the second coefficient table 412 and the second calculation formula B2. Then, the second control unit 45 controls the second power compensation unit 24B based on the second power compensation amount to reduce the power difference between the first WDM signal and the second WDM signal.

[0051] The monitoring control unit 61 communicates with other WDM devices 2 using an OSC (Optical Supervisory Channel).

[0052] The first OCM 14A in the upstream WDM device 2A monitors the optical power of each wavelength in the first WDM signal from the upstream first WSS 13A and notifies the monitoring control unit 61 of the monitoring results. Furthermore, the second OCM 14B in the upstream WDM device 2A monitors the optical power of each wavelength in the second WDM signal from the upstream second WSS 13B and notifies the monitoring control unit 61 of the monitoring results.

[0053] The first OCM 14A in the downstream WDM device 2B monitors the optical power for each wavelength in the first WDM signal from the downstream first WSS 13A and notifies the monitoring result to the monitoring control unit 61. Furthermore, the second OCM 14B in the downstream WDM device 2B monitors the optical power for each wavelength in the second WDM signal from the downstream second WSS 13B and notifies the monitoring result to the downstream monitoring control unit 61. The monitoring control unit 61 in the downstream WDM device 2B notifies the monitoring control unit 61 in the upstream WDM device 2A of the optical power for each wavelength of the downstream first WDM signal and the optical power for each wavelength of the downstream second WDM signal.

[0054] Next, the operation of the WDM system 1 of the first embodiment will be described. Fig. 5 is a flow chart showing an example of the processing operation of the correction coefficient calculation unit 80 in the WDM device 2 related to the first update processing. In Fig. 5, the acquisition unit 81 acquires the power profile of the transmission line (step S11). The acquisition unit 81 divides the acquired power profile of the transmission line into unit distances, for example, 1 km (step S12).

[0055] The acquiring unit 81 acquires an optical power value for each divided transmission distance (step S13). The tilt amount calculation unit 82 calculates the amount of tilt that occurs for each transmission distance based on the acquired optical power value for each transmission distance (step S14). The tilt amount calculation unit 82 calculates the amount of tilt that occurs in the transmission path based on the amount of tilt that occurs for each transmission distance (step S15).

[0056] The estimation calculation unit 83 calculates an estimated compensation amount for the transmission path based on the amount of tilt occurring in the transmission path (step S16). The estimated compensation amounts are, for example, a first estimated tilt compensation amount, a second estimated tilt compensation amount, a first estimated power compensation amount, and a second estimated power compensation amount. Specifically, the first estimation calculation unit 83A calculates a first estimated tilt compensation amount for compensating for the tilt in the first WDM signal using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a first calculation formula A1. The first estimation calculation unit 83A calculates a second estimated tilt compensation amount for compensating for the tilt in the second WDM signal using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a first calculation formula A2. The second estimation calculation unit 83B calculates the first estimated power compensation amount using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a second calculation formula B1. The second estimation calculation unit 83B calculates a second estimated power compensation amount using the amount of tilt occurring in the transmission path calculated by the amount-of-tilt calculation unit 82 and a second calculation formula B2.

[0057] The control unit 18 calculates the current compensation amount of the transmission path (step S17). Specifically, the current compensation amount is, for example, a first tilt compensation amount, a second tilt compensation amount, a first power compensation amount, and a second power compensation amount. The first calculation unit 42 calculates the first tilt compensation amount to compensate for the tilt in the first WDM signal using the optical power value and a first calculation formula A1. The first calculation unit 42 calculates the second tilt compensation amount to compensate for the tilt in the second WDM signal using the optical power value and a first calculation formula A2. The second calculation unit 43 calculates the first power compensation amount using the optical power value and a second calculation formula B1. The second calculation unit 43 calculates the second power compensation amount using the optical power value and a second calculation formula B2.

[0058] The coefficient calculation unit 84 calculates a correction coefficient based on the current compensation amount and the estimated compensation amount (step S18). Specifically, the first coefficient calculation unit 84A calculates a first correction coefficient K for correcting the first calculation formula A1 based on the first estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current first tilt compensation amount calculated by the first calculation unit 42. The first coefficient calculation unit 84A calculates a first correction coefficient L for correcting the first calculation formula A2 based on the second estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current second tilt compensation amount calculated by the first calculation unit 42. The second coefficient calculation unit 84B calculates a second correction coefficient M for correcting the second calculation formula B1 based on the first estimated power compensation amount calculated by the second estimation calculation unit 83B and the current first power compensation amount calculated by the second calculation unit 43. The second coefficient calculation unit 84B calculates a second correction coefficient N for correcting the second calculation formula B2 based on the second estimated power compensation amount calculated by the second estimation calculation unit 83B and the current second power compensation amount calculated by the second calculation unit 43.

[0059] The update unit 85 updates the calculated correction coefficients in the second coefficient table 412 (step S19), and ends the processing operation shown in Fig. 5. Specifically, the first update unit 85A updates the first correction coefficients in the second coefficient table 412 with the first correction coefficients K and L calculated by the first coefficient calculation unit 84A. The second update unit 85B updates the second correction coefficients in the second coefficient table 412 with the second correction coefficients M and N calculated by the second coefficient calculation unit 84B.

[0060] 6 is a flow chart showing an example of the processing operation of the control unit 18 in the WDM device 2 related to the compensation processing. In FIG. 6, the control unit 18 detects the optical power value for each wavelength band (step S21). The first calculation unit 42 reads out the first calculation formulas A1 and A2 and the first correction coefficients K and L from the coefficient table 41 (step S22).

[0061] The first calculation unit 42 calculates a first compensation amount based on the optical power value for each wavelength band, the first calculation formula, and the first correction coefficient (step S23). Specifically, the first compensation amount is a first tilt compensation amount and a second tilt compensation amount. The first calculation unit 42 calculates the first tilt compensation amount based on the optical power value for each wavelength band, the first calculation formula A1, and the first correction coefficient K. The first calculation unit 42 calculates the second tilt compensation amount based on the optical power value for each wavelength band, the first calculation formula A2, and the first correction coefficient L.

[0062] The first control unit 44 performs in-band tilt compensation based on the calculated first compensation amount (step S24). Specifically, the first control unit 44 controls the first tilt compensator 22A, which performs in-band tilt compensation, based on the calculated first tilt compensation amount. The first control unit 44 controls the second tilt compensator 22B, which performs in-band tilt compensation, based on the calculated second tilt compensation amount. As a result, the first tilt compensator 22A tilt-compensates the first WDM signal to reduce the amount of tilt in the first WDM signal. The second tilt compensator 22B tilt-compensates the second WDM signal to reduce the amount of tilt in the second WDM signal.

[0063] The second calculation unit 43 reads out second calculation formulas B1 and B2 and second correction coefficients M and N from the coefficient table 41 (step S25). The second calculation unit 43 calculates a second compensation amount based on the optical power value for each wavelength band, the second calculation formula, and the second correction coefficient (step S26). Specifically, the second compensation amount is the first power compensation amount and the second power compensation amount. The second calculation unit 43 calculates the first power compensation amount based on the optical power value for each wavelength band, the second calculation formula B1, and the second correction coefficient M. The second calculation unit 43 calculates the second power compensation amount based on the optical power value for each wavelength band, the second calculation formula B2, and the second correction coefficient N.

[0064] The second control unit 45 performs inter-band power compensation based on the calculated second compensation amount (step S27), and the processing operation shown in FIG. 6 is terminated. Specifically, the second control unit 45 controls the first power compensator 24A, which performs inter-band power compensation, based on the calculated first power compensation amount. The second control unit 45 controls the second power compensator 24B, which performs inter-band power compensation, based on the calculated second power compensation amount. As a result, the first power compensator 24A compensates the output power of the tilt-compensated first WDM signal to reduce the power difference between the tilt-compensated first WDM signal and the second WDM signal. The second power compensator 24B compensates the output power of the tilt-compensated second WDM signal to reduce the power difference between the tilt-compensated first WDM signal and the second WDM signal.

[0065] The WDM device 2 of the first embodiment acquires a power profile, which is a transmission line characteristic indicating the optical power value of each wavelength band for each transmission distance of the transmission line, and calculates the amount of tilt occurring in the transmission line based on the power profile. The WDM device 2 calculates an estimated compensation amount for compensating for the tilt of the WDM signal using the calculated amount of tilt occurring in the transmission line and a predetermined calculation formula. The WDM device 2 calculates a correction coefficient for correcting the predetermined calculation formula based on the calculated estimated compensation amount and the current compensation amount, and updates the calculated correction coefficient. As a result, the predetermined calculation formula is corrected using the correction coefficient calculated based on the estimated compensation amount calculated from the amount of tilt occurring and the current compensation amount, thereby reducing control errors in the compensation amount. Furthermore, in a multi-band system, even if the number of wavelengths changes during operation, SRS tilt compensation for each optical wavelength band can be achieved quickly and accurately.

[0066] The first estimation calculation unit 83A calculates a first estimated tilt compensation amount for compensating for tilt in the first WDM signal using the calculated amount of tilt occurring in the transmission line and a first calculation formula A1. The first estimation calculation unit 83A also calculates a second estimated tilt compensation amount for compensating for tilt in the second WDM signal using the calculated amount of tilt occurring in the transmission line and a first calculation formula A2. The first coefficient calculation unit 84A calculates a first correction coefficient K for correcting the first calculation formula A1 based on the calculated first estimated tilt compensation amount and the current first tilt compensation amount. The first coefficient calculation unit 84A also calculates a first correction coefficient L for correcting the first calculation formula A2 based on the calculated second estimated tilt compensation amount and the current second tilt compensation amount. The first update unit 85A updates the calculated first correction coefficients K and L. As a result, the first arithmetic expressions A1 and A2 are corrected by the first correction coefficients K and L calculated based on the estimated tilt compensation amount calculated from the generated tilt amount and the current tilt compensation amount, so that the control error of the tilt compensation amount can be reduced.

[0067] The second estimation calculation unit 83B calculates a first power estimated compensation amount that compensates for power for each wavelength band using the calculated amount of tilt occurring in the transmission line and second calculation formula B1. The second estimation calculation unit 83B also calculates a second power estimated compensation amount that compensates for power for each wavelength band using the calculated amount of tilt occurring in the transmission line and second calculation formula B2. The second coefficient calculation unit 84B calculates a second correction coefficient M that corrects the second calculation formula B1 based on the calculated first power estimated compensation amount and the current first power compensation amount. The second coefficient calculation unit 84B also calculates a second correction coefficient N that corrects the second calculation formula B2 based on the calculated second power estimated compensation amount and the current second power compensation amount. The second update unit 85B updates the calculated second correction coefficients M and N. As a result, the second arithmetic expressions B1 and B2 are corrected by the second correction coefficients M and N calculated based on the estimated power compensation amount calculated from the amount of tilt that has occurred and the current power compensation amount, thereby reducing the control error of the power compensation amount.

[0068] The acquisition unit 81 acquires a power profile indicating the optical power value for each transmission distance of an arbitrary wavelength band among a plurality of wavelength bands for each transmission distance of the transmission path. The tilt amount calculation unit 82 calculates the amount of tilt generated for each transmission distance from the power profile of the arbitrary wavelength band, and calculates the amount of tilt generated for the transmission path from the amount of tilt generated for each transmission distance. As a result, for example, when building a system or during system operation, it is possible to determine the amount of compensation appropriate for each transmission path using the power profile of the arbitrary wavelength band.

[0069] In the first embodiment, the acquiring unit 81 in the WDM device 2 acquires a power profile indicating the optical power value for each transmission distance of an arbitrary wavelength band among a plurality of wavelength bands for each transmission distance of the transmission line. However, the acquiring unit 81 may acquire a first power profile indicating the optical power value for each transmission distance of a first wavelength band among a plurality of wavelength bands for each transmission distance of the transmission line, and may also acquire a second power profile indicating the optical power value for each transmission distance of a second wavelength band. Therefore, this embodiment will be described below as a second embodiment. [Example]

[0070] FIG. 7 is an explanatory diagram showing an example of a WDM system 1A according to a second embodiment. The same components as those in the WDM system 1 shown in FIG. 1 are designated by the same reference numerals, and redundant description of the components and operations will be omitted. The WDM device 2 shown in FIG. 1 differs from the WDM device 2A1 shown in FIG. 7 in that the acquisition unit 81 includes a first acquisition unit 81A and a second acquisition unit 81B. Furthermore, the generated tilt amount calculation unit 82 includes a first change amount calculation unit 82A, a second change amount calculation unit 82B, and a generated amount calculation unit 82C. The WDM device 2B1 also has substantially the same configuration as the WDM device 2A1. The WDM device 2B1 includes a first optical receiving group 20A and a second optical receiving group 20B.

[0071] The acquisition unit 81 has a first acquisition unit 81A and a second acquisition unit 81B. The first acquisition unit 81A acquires a first power profile indicating optical power values ​​for each transmission distance of a first wavelength band, for example, a short wavelength band, among a plurality of wavelength bands for each transmission distance of a transmission line, when the system is constructed or when the system is operated stably. The second acquisition unit 81B acquires a second power profile indicating optical power values ​​for each transmission distance of a second wavelength band, for example, a long wavelength band, among a plurality of wavelength bands for each transmission distance of a transmission line, when the system is constructed or when the system is operated stably.

[0072] The generated tilt amount calculation unit 82 has a first change amount calculation unit 82A, a second change amount calculation unit 82B, and an generated amount calculation unit 82C. The first change amount calculation unit 82A calculates a first power change amount of the transmission path from the first power profile acquired by the first acquisition unit 81A. The second change amount calculation unit 82B calculates a second power change amount of the transmission path from the second power profile acquired by the second acquisition unit 81B. The generated amount calculation unit 82C calculates the generated tilt amount of the transmission path based on the first power change amount and the second power change amount.

[0073] 8 is an explanatory diagram showing an example of a power profile, which is a relationship between a transmission distance and a power detection value in the second embodiment. As shown in FIG. 8, the first change amount calculation unit 82A calculates a first estimated power profile at the input end of the transmission line when the first power profile in the short wavelength band is extrapolated using the gradient near the input end of the transmission line. The first change amount calculation unit 82A calculates a first power change amount, which is the amount of power change due to SRS in the short wavelength band, as the difference between the first power profile and the first estimated power profile. Note that the WDL amount is subtracted from the first power change amount.

[0074] The second change amount calculation unit 82B calculates a second estimated power profile at the input end of the transmission line when the second power profile in the long wavelength band is extrapolated using the gradient near the input end of the transmission line, as shown in Fig. 8. The second change amount calculation unit 82B calculates a second power change amount, which is the amount of power change due to SRS in the long wavelength band, from the difference between the second power profile and the second estimated power profile. Note that the WDL amount is subtracted from the second power change amount.

[0075] 9 is an explanatory diagram showing an example of the relationship between wavelength and the amount of tilt that occurs. The amount-of-tilt calculation unit 82C calculates the amount of tilt that occurs in the transmission line by plotting the first amount of power change due to SRS in the short wavelength band and the second amount of power change due to SRS in the long wavelength band for each wavelength as shown in FIG.

[0076] 10 is a flow diagram showing an example of the processing operation of the correction coefficient calculation unit 80 in the WDM device 2A1 related to the second update processing. In FIG. 10, the acquisition unit 81 acquires the power profile of each wavelength of the transmission path (step S31). The acquisition unit 81 acquires, for example, a first power profile of a first wavelength band in the short wavelength band through the first acquisition unit 81A, and acquires, for example, a second power profile of a second wavelength band in the long wavelength band through the second acquisition unit 81B (step S32).

[0077] The generated tilt amount calculation unit 82 calculates the generated tilt amount of the transmission path based on the first power profile and the second power profile (step S33). Specifically, the first change amount calculation unit 82A calculates a first estimated power profile from the first power profile. The first change amount calculation unit 82A calculates a first power change amount due to SRS in the short wavelength band based on the difference between the first power profile and the first estimated power profile. The second change amount calculation unit 82B calculates a second estimated power profile from the second power profile. The second change amount calculation unit 82B calculates a second power change amount due to SRS in the long wavelength band based on the difference between the second power profile and the second estimated power profile. The generated amount calculation unit 82C calculates the generated tilt amount of the transmission path shown in FIG. 9 based on the first power change amount due to SRS in the short wavelength band and the second power change amount due to SRS in the long wavelength band.

[0078] The estimation calculation unit 83 calculates an estimated compensation amount for the transmission path based on the amount of tilt occurring in the transmission path (step S34). The estimated compensation amounts are, for example, a first estimated tilt compensation amount, a second estimated tilt compensation amount, a first estimated power compensation amount, and a second estimated power compensation amount. Specifically, the first estimation calculation unit 83A calculates a first estimated tilt compensation amount for compensating for tilt in the first WDM signal using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a first calculation formula A1. The first estimation calculation unit 83A calculates a second estimated tilt compensation amount for compensating for tilt in the second WDM signal using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a first calculation formula A2. The second estimation calculation unit 83B calculates the first estimated power compensation amount using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a second calculation formula B1. The second estimation calculation unit 83B calculates a second estimated power compensation amount using the amount of tilt occurring in the transmission path calculated by the amount-of-tilt calculation unit 82 and a second calculation formula B2.

[0079] The control unit 18 calculates the current compensation amount of the transmission path (step S35). Specifically, the current compensation amount is, for example, a first tilt compensation amount, a second tilt compensation amount, a first power compensation amount, and a second power compensation amount. The first calculation unit 42 calculates the first tilt compensation amount to compensate for the tilt in the first WDM signal using the optical power value and a first calculation formula A1. The first calculation unit 42 calculates the second tilt compensation amount to compensate for the tilt in the second WDM signal using the optical power value and a first calculation formula A2. The second calculation unit 43 calculates the first power compensation amount using the optical power value and a second calculation formula B1. The second calculation unit 43 calculates the second power compensation amount using the optical power value and a second calculation formula B2.

[0080] The coefficient calculation unit 84 calculates a correction coefficient based on the current compensation amount and the estimated compensation amount (step S36). Specifically, the first coefficient calculation unit 84A calculates a first correction coefficient K for correcting the first calculation formula A1 based on the first estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current first tilt compensation amount calculated by the first calculation unit 42. The first coefficient calculation unit 84A calculates a first correction coefficient L for correcting the first calculation formula A2 based on the second estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current second tilt compensation amount calculated by the first calculation unit 42. The second coefficient calculation unit 84B calculates a second correction coefficient M for correcting the second calculation formula B1 based on the first estimated power compensation amount calculated by the second estimation calculation unit 83B and the current first power compensation amount calculated by the second calculation unit 43. The second coefficient calculation unit 84B calculates a second correction coefficient N for correcting the second calculation formula B2 based on the second estimated power compensation amount calculated by the second estimation calculation unit 83B and the current second power compensation amount calculated by the second calculation unit 43.

[0081] The update unit 85 updates the calculated correction coefficients in the second coefficient table 412 (step S37), and ends the processing operation shown in Fig. 10. Specifically, the first update unit 85A updates the first correction coefficients in the second coefficient table 412 with the first correction coefficients K and L calculated by the first coefficient calculation unit 84A. The second update unit 85B updates the second correction coefficients in the second coefficient table 412 with the second correction coefficients M and N calculated by the second coefficient calculation unit 84B.

[0082] The WDM device 2A1 of the second embodiment acquires a first power profile, which is a first transmission line characteristic for each transmission distance in a first wavelength band, and acquires a second power profile, which is a second transmission line characteristic for each transmission distance in a second wavelength band. The WDM device 2A1 calculates a first power change amount in the transmission line from the first power profile and calculates a second power change amount in the transmission line from the second power profile. Furthermore, the WDM device 2A1 calculates the amount of tilt occurring in the transmission line based on the first power change amount and the second power change amount. As a result, for example, during system construction or system operation, it is possible to determine the amount of compensation appropriate for each transmission line using the power profiles of multiple wavelength bands.

[0083] The WDM device 2A1 calculates a first amount of power change in the transmission line based on the first power profile and a first estimated power profile obtained by extrapolating the first power profile using the gradient near the input end of the transmission line.The WDM device 2A1 calculates a second amount of power change in the transmission line based on the second power profile and a second estimated power profile obtained by extrapolating the second power profile using the gradient near the input end of the transmission line.As a result, the first amount of power change and the second amount of power change can be obtained.

[0084] In the example shown, the acquisition unit 81 of the WDM device 2A calculates the amount of tilt occurring in the transmission line using the power profiles for each transmission distance of the first wavelength band and the second wavelength band among a plurality of wavelength bands for each transmission distance of the transmission line. However, the number of wavelength bands is not limited to two, and three or more wavelength bands may be used, and this can be changed as appropriate.

[0085] In the above-described first embodiment, a power profile indicating an optical power value for each transmission distance of an arbitrary wavelength band among a plurality of wavelength bands for each transmission distance of a transmission path is acquired. However, the acquiring unit 81 may acquire characteristics for each number of wavelengths, and such an embodiment will be described below as a third embodiment. [Example]

[0086] FIG. 11 is an explanatory diagram showing an example of a WDM system 1B according to a third embodiment. The same components as those in the WDM system 1 shown in FIG. 1 are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The WDM device 2 shown in FIG. 1 differs from the WDM device 2 shown in FIG. 1 in that the latter includes a pseudo light source 91 and a characteristics acquisition unit 81C. Furthermore, the generated tilt amount calculation unit 82 includes a first trend calculation unit 82D, a second trend calculation unit 82E, and a generated amount calculation unit 82F. The WDM device 2B2 has substantially the same configuration as the WDM device 2A2.

[0087] The pseudo light source 91 generates pseudo signals of multiple wavelength patterns on the transmission line. The pseudo light source 91 is connected to the first WSS 13A and the second WSS 13B, and adds the pseudo signal from the first WSS 13A to the first WDM signal, and also adds the pseudo signal from the second WSS 13B to the second WDM signal.

[0088] The first OCM 14A in the downstream WDM device 2B2 monitors the optical power of each wavelength of the pseudo signal in the first WDM signal from the downstream first WSS 13A and notifies the monitoring result to the monitoring control unit 61. Furthermore, the second OCM 14B in the downstream WDM device 2B monitors the optical power of each wavelength of the pseudo signal in the second WDM signal from the downstream second WSS 13B and notifies the monitoring result to the downstream monitoring control unit 61. The monitoring control unit 61 in the downstream WDM device 2B notifies the monitoring control unit 61 in the upstream WDM device 2A of the optical power of each wavelength of the downstream pseudo signal and the optical power of each wavelength of the downstream pseudo signal.

[0089] The acquisition unit 81 includes a characteristics acquisition unit 81C. The characteristics acquisition unit 81C acquires, from the monitoring and control unit 61, transmission path characteristics indicating the optical power value of each wavelength for each wavelength pattern of the pseudo signal when the system is constructed or when the system is operating stably.

[0090] FIG. 12 is an explanatory diagram showing an example of power change trends in the long wavelength band and the short wavelength band in the third embodiment. The generated tilt amount calculation unit 82 includes a first trend calculation unit 82D, a second trend calculation unit 82E, and an generated amount calculation unit 82F. The first trend calculation unit 82D calculates a first change trend that indicates a change trend of optical power values ​​according to the number of wavelengths of an arbitrary short wavelength side channel from the transmission path characteristics for each wavelength pattern. As shown in FIG. 12, the first trend calculation unit 82D calculates the first change trend by plotting optical power values ​​when the number of wavelengths is 20%, optical power values ​​when the number of wavelengths is 50%, and optical power values ​​when the number of wavelengths is 100%, and then extrapolates the first change trend to obtain the optical power value when the number of wavelengths is 0%.

[0091] Furthermore, the second trend calculation unit 82E calculates a second change trend that indicates the change trend of the optical power value according to the number of wavelengths of an arbitrary long wavelength side Ch from the transmission path characteristics for each wavelength pattern. As shown in Fig. 12, the second trend calculation unit 82E calculates the second change trend by plotting the optical power value when the number of wavelengths is 20%, the optical power value when the number of wavelengths is 50%, and the optical power value when the number of wavelengths is 100%, and extrapolates the second change trend to obtain the optical power value when the number of wavelengths is 0%.

[0092] The generated amount calculation unit 82F calculates the amount of tilt generated in the transmission path, which is the amount of power change for each number of wavelengths, based on the first change trend and the second change trend. The generated amount calculation unit 82F calculates the amount of power change due to WDL as the difference between the optical power value for 0% wavelengths in the first change trend and the optical power value for 0% wavelengths in the second change trend. Furthermore, as shown in FIG. 12, the generated amount calculation unit 82F calculates the amount of tilt generated in the transmission path for each number of wavelengths based on the amount of power change for each number of wavelengths between the first change trend and the second change trend. The generated amount calculation unit 82F calculates, for example, the amount of tilt generated for 20% wavelengths, the amount of tilt generated for 50% wavelengths, and the amount of tilt generated for 100% wavelengths.

[0093] 13 is a flow chart showing an example of the processing operation of the correction coefficient calculation unit 80 in the WDM device 2 related to the third update processing. In FIG. 13, the quasi-light source 91 emits a quasi-signal (step S41). The characteristic acquisition unit 81C determines whether or not there is an unset wavelength allocation pattern candidate (step S42).

[0094] If there is an unset wavelength allocation pattern candidate (step S42: Yes), the characteristics acquisition unit 81C sets the unset wavelength allocation pattern (step S43). The characteristics acquisition unit 81C acquires the wavelength deviation of the wavelength allocation pattern (step S44), and proceeds to step S42 to determine whether there is an unset wavelength allocation pattern candidate.

[0095] If there is no unset wavelength allocation pattern candidate (step S42: No), the characteristics acquisition unit 81C extracts the optical power values ​​of the short wavelength band and the long wavelength band from the wavelength deviation for each wavelength allocation pattern (step S45).

[0096] The generated tilt amount calculation unit 82 obtains a first power change trend in the short wavelength band and a second power change trend in the long wavelength band based on the optical power values ​​of the short wavelength band and the long wavelength band (step S46). Specifically, the first trend calculation unit 82D obtains the first power change trend in the short wavelength band based on the optical power values ​​of the short wavelength band. The second trend calculation unit 82E obtains the second power change trend in the long wavelength band based on the optical power values ​​of the long wavelength band.

[0097] The generated amount calculation unit 82F in the generated tilt amount calculation unit 82 calculates the generated tilt amount of the transmission path according to the number of wavelengths based on the first power change tendency in the short wavelength band and the second power change tendency in the long wavelength band (step S47).

[0098] The estimation calculation unit 83 calculates an estimated amount of compensation for the transmission path based on the amount of tilt occurring in the transmission path corresponding to the current number of wavelengths (step S48). The estimated compensation amounts are, for example, a first estimated tilt compensation amount, a second estimated tilt compensation amount, a first estimated power compensation amount, and a second estimated power compensation amount. Specifically, the first estimation calculation unit 83A calculates a first estimated tilt compensation amount for compensating for the tilt in the first WDM signal using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a first calculation formula A1. The first estimation calculation unit 83A calculates a second estimated tilt compensation amount for compensating for the tilt in the second WDM signal using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a first calculation formula A2. The second estimation calculation unit 83B calculates the first estimated power compensation amount using the amount of tilt occurring in the transmission path calculated by the tilt amount calculation unit 82 and a second calculation formula B1. The second estimation calculation unit 83B calculates a second estimated power compensation amount using the amount of tilt occurring in the transmission path calculated by the amount-of-tilt calculation unit 82 and a second calculation formula B2.

[0099] The control unit 18 calculates the current compensation amount of the transmission path (step S49). Specifically, the current compensation amount is, for example, a first tilt compensation amount, a second tilt compensation amount, a first power compensation amount, and a second power compensation amount. The first calculation unit 42 calculates the first tilt compensation amount to compensate for the tilt in the first WDM signal using the optical power value and a first calculation formula A1. The first calculation unit 42 calculates the second tilt compensation amount to compensate for the tilt in the second WDM signal using the optical power value and a first calculation formula A2. The second calculation unit 43 calculates the first power compensation amount using the optical power value and a second calculation formula B1. The second calculation unit 43 calculates the second power compensation amount using the optical power value and a second calculation formula B2.

[0100] The coefficient calculation unit 84 calculates a correction coefficient based on the current compensation amount and the estimated compensation amount (step S50). Specifically, the first coefficient calculation unit 84A calculates a first correction coefficient K for correcting the first calculation formula A1 based on the first estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current first tilt compensation amount calculated by the first calculation unit 42. The first coefficient calculation unit 84A calculates a first correction coefficient L for correcting the first calculation formula A2 based on the second estimated tilt compensation amount calculated by the first estimation calculation unit 83A and the current second tilt compensation amount calculated by the first calculation unit 42. The second coefficient calculation unit 84B calculates a second correction coefficient M for correcting the second calculation formula B1 based on the first estimated power compensation amount calculated by the second estimation calculation unit 83B and the current first power compensation amount calculated by the second calculation unit 43. The second coefficient calculation unit 84B calculates a second correction coefficient N for correcting the second calculation formula B2 based on the second estimated power compensation amount calculated by the second estimation calculation unit 83B and the current second power compensation amount calculated by the second calculation unit 43.

[0101] The update unit 85 updates the calculated correction coefficients in the second coefficient table 412 (step S51), and ends the processing operation shown in Fig. 13. Specifically, the first update unit 85A updates the first correction coefficients in the second coefficient table 412 with the first correction coefficients K and L calculated by the first coefficient calculation unit 84A. The second update unit 85B updates the second correction coefficients in the second coefficient table 412 with the second correction coefficients M and N calculated by the second coefficient calculation unit 84B.

[0102] The WDM device 2A2 of the third embodiment acquires transmission line characteristics indicating the optical power value of each wavelength for each wavelength pattern from pseudo signals of multiple wavelength patterns generated in the transmission line. The WDM device 2A2 calculates a first change trend indicating the change trend of the optical power value according to the number of wavelengths on the arbitrary short wavelength side from the transmission line characteristics for each wavelength pattern, and calculates a second change trend indicating the change trend of the optical power value according to the number of wavelengths on the arbitrary long wavelength side from the transmission line characteristics for each wavelength pattern. The WDM device 2A2 calculates the amount of tilt occurring in the transmission line based on the first change trend and the second change trend. As a result, for example, during system construction or system operation, the transmission line characteristics indicating the optical power value of each wavelength for each wavelength pattern can be used to determine the amount of compensation appropriate for each transmission line.

[0103] In the WDM device 2A2 of the third embodiment, the transmission path characteristics for each wavelength pattern are obtained using a pseudo signal from the pseudo light source 91. However, the present invention is not limited to the pseudo light source 91, and for example, the first optical transmission group 19A or the second optical transmission group 19B may be used as the pseudo light source 91, and modifications can be made as appropriate.

[0104] Furthermore, the WDM device 2 is configured as a single package including the demultiplexing unit 11, first and second receiving amplifiers 12A and 12B, first and second WSSs 13A and 13B, first and second transmitting amplifiers 15A and 15B, multiplexing unit 16, first and second detecting units 17A and 17B, and control unit 18. An optical connector is connected to the input stage of the demultiplexing unit 11, and an optical connector is connected to the output stage of the multiplexing unit 16. The WDM device 2 has also been described in the form of a single package.

[0105] However, the WDM device 2 may be configured not in a single package but in, for example, three packages. The first package includes, for example, a first receiving amplifier 12A, a first WSS 13A, and a first transmitting amplifier 15A. The second package includes, for example, a second receiving amplifier 12B, a second WSS 13B, and a second transmitting amplifier 15B. The third package includes a demultiplexing unit 11, a multiplexing unit 16, first and second detecting units 17A and 17B, and a control unit 18.

[0106] The first receiving amplifier 12A in the first package and the demultiplexing unit 11 in the third package are connected by an optical connector, and the second receiving amplifier 12B in the second package and the demultiplexing unit 11 in the third package are connected by an optical connector. Furthermore, the first transmitting amplifier 15A in the first package and the multiplexing unit 16 in the third package are connected by an optical connector, and the second transmitting amplifier 15B in the second package and the multiplexing unit 16 in the third package are connected by an optical connector. The input stage of the demultiplexing unit 11 in the third optical package is connected by an optical connector, and the output stage of the multiplexing unit 16 is connected by an optical connector. Furthermore, the control unit 18 in the third package and the first transmitting amplifier 15A in the first package are connected by an electrical connector, and the control unit 18 in the third package and the second transmitting amplifier 15B in the second package are connected by an electrical connector.

[0107] For convenience of explanation, the WDM device 2 is exemplified as outputting a WDM signal obtained by multiplexing a first WDM signal in the C band and a second WDM signal in the L band. However, the WDM device 2 can also be applied to outputting a WDM signal obtained by multiplexing a second WDM signal in the S band, which has a short wavelength of 1460 nm to 1530 nm, and the first WDM signal in the C band. The first WDM signal is not limited to the C band but can be the L band or S band, and the second WDM signal is not limited to the L band but can be the C band or S band, and these bands can be changed as appropriate. Although the WDM device 2 is exemplified as outputting a WDM signal including two optical wavelength bands, the WDM device 2 can also be applied to outputting a WDM signal including three or more optical wavelength bands, for example.

[0108] In this embodiment, the case where the first coefficient table 411 that manages the coefficient 411B and loss coefficient 411C for each fiber type 411A is provided is exemplified. However, it is also possible to input the coefficient 411B and loss coefficient 411C for each fiber type 411A to the control unit 18, or to have the control unit 18 measure the fiber type of the optical fiber 3 and set the coefficient and loss coefficient according to the measurement result, and other changes can be made as appropriate.

[0109] In the above embodiment, the wavelength ranges of the C band, the S band, and the L band are defined, but the wavelength ranges are not limited to these, and the ranges can be set or changed as appropriate.

[0110] Furthermore, in the above embodiment, the case where the C band and the L band are used is exemplified, but the present invention is not limited to the C band, the S band, and the L band. For example, the present invention may be applied to the O (Original) band (1260 nm to 1360 nm), the E (Extended) band (1360 nm to 1460 nm), or the U (Ultralong Wavelength) band (1625 nm to 1675 nm), and can be changed as appropriate.

[0111] Furthermore, for example, the WDM device 2 has been illustrated as having the first optical transmission group 19A and the second optical transmission group 19B built in, but it can also be applied when the first optical transmission group and the second optical transmission group are externally connected.

[0112] Furthermore, the components of each unit shown in the figure do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0113] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or MCU (Micro Controller Unit)). Needless to say, the various processing functions may be executed in whole or in part on a program analyzed and executed by a CPU (or a microcomputer such as an MPU or MCU), or on hardware using wired logic. [Explanation of symbols]

[0114] 2, 2A, 2A1, 2A2 WDM device 11 Demultiplexer 16 Multiplexing section 17A First detection unit 17B Second detection unit 22A First Tilt Compensation Unit 22B Second tilt compensation unit 24A First power compensation section 24B Second power compensation section 42 First Calculation Unit 43 Second Calculation Unit 44 First control section 45 Second control section 81 Acquisition Department 81A First Acquisition Section 81B Second Acquisition Section 81C Characteristic acquisition part 82 Tilt amount calculation unit 82A First change amount calculation unit 82B second change amount calculation unit 82C Generation amount calculation unit 82D First trend calculation unit 82E Second trend calculation unit 82F Generation amount calculation unit 83 Estimation calculation section 83A First estimation calculation unit 83B Second estimation calculation unit 84 Coefficient calculation section 84A First coefficient calculation unit 84B Second coefficient calculation unit 85 Update section 85A First Update 85B Second Update Section 91 Pseudo light source

Claims

1. a demultiplexing unit that demultiplexes a wavelength multiplexed signal for each wavelength band from a multiplexed signal including wavelength multiplexed signals of a plurality of wavelength bands; a detector for detecting an optical power value of each wavelength multiplexed signal for each wavelength band; a calculation unit that calculates a compensation amount for compensating for tilt of the wavelength multiplexed signal using the optical power value detected by the detection unit and a predetermined calculation formula; a control unit that compensates for the tilt of the wavelength multiplexed signal based on the amount of compensation calculated by the calculation unit; a multiplexing unit that multiplexes the wavelength-multiplexed signals compensated by the control unit and outputs the multiplexed signals to a transmission line; an acquisition unit that acquires transmission path characteristics indicating optical power values ​​of each wavelength band; an amount of tilt calculation unit that calculates an amount of tilt generated in the transmission path based on the transmission path characteristics; an estimation calculation unit that calculates an estimated compensation amount for compensating for tilt of the wavelength multiplexed signal using the amount of tilt generated in the transmission path calculated by the generated tilt amount calculation unit and the predetermined calculation formula; a coefficient calculation unit that calculates a coefficient to be used in the predetermined calculation formula based on the estimated compensation amount calculated by the estimation calculation unit, The calculation unit an optical wavelength division multiplexing transmission device, wherein the coefficient calculated by the coefficient calculation unit is used to calculate a compensation amount for compensating for tilt of the wavelength division multiplexed signal;

2. The calculation unit a first calculation unit that calculates a first compensation amount for compensating for tilt in the wavelength multiplexed signal by using the optical power value and a first calculation formula in the predetermined calculation formula; The control unit a first control unit that compensates for tilt in the wavelength multiplexed signal based on the first compensation amount; The estimation calculation unit a first estimation calculation unit that calculates a first estimated compensation amount for compensating for tilt in the wavelength multiplexed signal by using the amount of tilt generated in the transmission line calculated by the generated tilt amount calculation unit and the first calculation formula; The coefficient calculation unit a first coefficient calculation unit that calculates a first coefficient to be used in the first calculation formula based on the first estimated compensation amount calculated by the first estimation calculation unit; The first calculation unit 2. The optical wavelength division multiplexing transmission device according to claim 1, wherein the first compensation amount is calculated using the first coefficient calculated by the first coefficient calculation unit.

3. The calculation unit a second calculation unit that calculates a second compensation amount for compensating for power of each of the wavelength bands by using the optical power value and a second calculation formula in the predetermined calculation formula so that a power difference between the wavelength multiplexed signals becomes small, The control unit a second control unit that compensates for power for each of the wavelength bands based on the second compensation amount; The estimation calculation unit a second estimation calculation unit that calculates a second estimated compensation amount for compensating for power for each wavelength band by using the amount of tilt generated in the transmission line calculated by the generated tilt amount calculation unit and the second calculation formula; The coefficient calculation unit a second coefficient calculation unit that calculates a second coefficient to be used in the second calculation formula based on the second estimated compensation amount calculated by the second estimation calculation unit; The second calculation unit 3. The optical wavelength division multiplexing transmission device according to claim 1, wherein the second compensation amount is calculated using the second coefficient calculated by the second coefficient calculation unit.

4. The optical wavelength division multiplexing transmission device, outputting pseudo signals of a plurality of wavelength patterns to the transmission line; The acquisition unit a characteristics acquisition unit that acquires, from the pseudo signal, a transmission path characteristic indicating an optical power value of each wavelength for each of the wavelength patterns; The generated tilt amount calculation unit a first trend calculation unit that calculates a first change trend that indicates a change trend of an optical power value according to an arbitrary number of wavelengths on the short wavelength side from the transmission path characteristics for each of the wavelength patterns; a second trend calculation unit that calculates a second change trend that indicates a change trend of an optical power value according to an arbitrary number of wavelengths on the long wavelength side from the transmission path characteristics for each of the wavelength patterns; an occurrence amount calculation unit that calculates the occurrence amount of tilt of the transmission line based on the first change tendency and the second change tendency; 4. The optical wavelength division multiplexing transmission device according to claim 1, further comprising:

5. A demultiplexing unit that demultiplexes wavelength multiplexed signals for each wavelength band from a multiplexed signal including wavelength multiplexed signals of a plurality of wavelength bands; a detector for detecting a first optical power value of each wavelength multiplexed signal for each wavelength band; a calculation unit that calculates a compensation amount for compensating for tilt of the wavelength multiplexed signal using the first optical power value detected by the detection unit and a predetermined calculation formula; a control unit that compensates for the tilt of the wavelength multiplexed signal based on the amount of compensation calculated by the calculation unit; a multiplexing unit that multiplexes the wavelength-multiplexed signals compensated by the control unit and outputs the multiplexed signals to a transmission line; an acquisition unit that acquires a second optical power value for each wavelength in a downstream optical wavelength division multiplexing device; a coefficient calculation unit that calculates a coefficient to be used in the predetermined calculation formula based on the second optical power value, The calculation unit an optical wavelength division multiplexing transmission device, wherein the coefficient calculated by the coefficient calculation unit is used to calculate a compensation amount for compensating for tilt of the wavelength division multiplexed signal;

6. The optical wavelength division multiplexing transmission device, a pseudo light source for outputting a pseudo signal to the adjacent downstream optical wavelength division multiplexing transmission device; The second optical power value is 6. The optical wavelength division multiplexing transmission device according to claim 5, wherein the light emitted from the pseudo light source is measured.

7. An optical wavelength multiplexing transmission system having a first optical wavelength multiplexing transmission device and a second optical wavelength multiplexing transmission device, The first optical wavelength division multiplexing transmission device connected to the second optical wavelength division multiplexing transmission device via a transmission line, The first optical wavelength division multiplexing transmission device Demultiplexing a wavelength multiplexed signal for each wavelength band from a multiplexed signal including wavelength multiplexed signals of a plurality of wavelength bands; detecting a first optical power value of each wavelength multiplexed signal for each wavelength band; calculating a compensation amount for compensating for the tilt of the wavelength multiplexed signal using the detected first optical power value, a predetermined arithmetic expression, and a coefficient; Compensating for the tilt of the wavelength multiplexed signal based on the calculated compensation amount; each compensated wavelength multiplexed signal is multiplexed and output to the transmission line; The coefficients are: An optical wavelength multiplexing transmission system characterized in that the optical power is calculated based on a second optical power value of each wavelength obtained by measuring light transmitted from a pseudo light source mounted in the first optical wavelength multiplexing transmission device by a second optical wavelength multiplexing transmission device.

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