JP5505098B2 - Wavelength multiplexing apparatus and detection method - Google Patents

Description

  The present invention relates to a wavelength division multiplexing apparatus and a detection method.

  With the increase in communication traffic, construction of an optical transmission network based on WDM (Wavelength Division Multiplexing) technology is progressing. In order to construct a more flexible network, development and introduction of terminal station devices, repeaters, OADMs (Optical Add Drop Multiplexers) that add and drop optical signals in units of optical wavelengths are progressing. Yes.

  In such an optical transmission network, a wavelength multiplexing filter for performing wavelength multiplexing is a key device. In the wavelength division multiplexing filter, the wavelength transmission characteristics are shifted due to causes such as power failure, power failure, temperature control circuit failure, device failure, and aging degradation. If the wavelength transmission characteristics of the wavelength multiplexing filter deviate, the signal quality deteriorates.

  For this reason, it is required to detect the shift of the wavelength transmission characteristics of the wavelength multiplexing filter at an early stage to issue an alarm, correct the shift of the wavelength transmission characteristics, or restore the normal state by protection or the like. As a method for detecting a shift in wavelength transmission characteristics, there are known methods for monitoring an increase in end-to-end errors, an increase in filter transmission loss due to a measurement wavelength, a power supply for a temperature control circuit, and the like ( For example, see the following Patent Document 1.)

JP 2000-78085 A

  However, the above-described prior art has a problem that a shift in wavelength transmission characteristics of the wavelength multiplexing filter cannot be detected with high accuracy. For example, in the method of monitoring the increase in errors, it is not possible to distinguish between an increase in errors due to a shift in wavelength transmission characteristics and an increase in errors due to factors other than the shift in wavelength transmission characteristics.

  Further, in the method of monitoring the increase in filter transmission loss due to the measurement wavelength, it is impossible to accurately detect the shift in wavelength transmission characteristics of the wavelength multiplexing filter at the signal wavelength. Further, since the method of monitoring the power supply of the temperature control circuit is indirect monitoring, for example, a shift in wavelength transmission characteristics of the wavelength multiplexing filter due to deterioration over time cannot be detected accurately.

  The disclosed wavelength division multiplexing apparatus and detection method are intended to solve the above-described problems, and are intended to accurately detect a shift in wavelength transmission characteristics of a wavelength division multiplexing filter.

  In order to solve the above-described problems and achieve the object, the disclosed technology includes a wavelength multiplexing filter that performs wavelength multiplexing of an optical signal, an input-side acquisition unit that acquires a spectrum of an optical signal input to the wavelength multiplexing filter, An output-side acquisition unit that acquires a spectrum of an optical signal output from the wavelength multiplexing filter, and a wavelength transmission of the wavelength multiplexing filter based on a difference between the spectra acquired by the input-side acquisition unit and the output-side acquisition unit It is a requirement to include a detection unit that detects a deviation in characteristics.

  According to the disclosed wavelength multiplexing apparatus and detection method, it is possible to accurately detect a shift in wavelength transmission characteristics of the wavelength multiplexing filter.

1 is a diagram illustrating a configuration example of an OADM according to a first embodiment. 3 is a diagram illustrating a configuration example of a signal selection unit according to the first embodiment; FIG. It is a graph which shows the loss of the optical signal by the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter. It is a figure which shows the structural example 1 of OCM. It is a figure which shows the structural example 2 of OCM. It is a figure which shows the structural example 3 of OCM. It is a graph which shows the example of a measurement by the input side OCM of a 40-Gbps optical signal. It is a graph which shows the example of a measurement by the output side OCM of a 40-Gbps optical signal. It is a graph (the 1) which shows the example of a measurement by OCM of the optical signal of 10 Gbps. It is a graph (the 2) which shows the example of a measurement by OCM of the optical signal of 10 Gbps. It is a graph which shows the relationship between the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter, and the penalty of an optical signal. It is a figure which shows an example of the threshold value memorize | stored in a threshold value memory | storage part. 3 is a flowchart illustrating an example of processing according to the first exemplary embodiment. It is a figure which shows an example of the communication system to which OADM is applied. It is a figure which shows the determination example 1 of the classification of an optical signal. It is a figure which shows the determination example 2 of the classification of an optical signal. FIG. 5 is a diagram illustrating a configuration example of a signal selection unit according to a second embodiment. It is a figure which shows an example of the threshold value memorize | stored in a threshold value memory | storage part. 10 is a flowchart illustrating an example of processing according to the second exemplary embodiment. It is a figure which shows an example of the communication system to which OADM is applied. It is a figure which shows the example of generation | occurrence | production of the signal interruption in the line | wire of a communication system. FIG. 4 is a diagram illustrating a configuration example of an OADM according to a third embodiment. FIG. 9 is a diagram illustrating a configuration example of a signal selection unit according to a third embodiment. It is a figure which shows the structural example of TERM concerning Embodiment 4. FIG. FIG. 9 is a diagram illustrating a configuration example of a signal selection unit according to a fourth embodiment. It is a graph which shows the example of a measurement by the output side OCM of a 40-Gbps optical signal. It is a graph which shows the example of the inversion spectrum of an optical signal of 40 Gbps. 10 is a flowchart illustrating an example of processing according to the fourth exemplary embodiment. FIG. 10 is a diagram illustrating a configuration example of a signal selection unit according to a fifth embodiment; 10 is a flowchart illustrating an example of processing according to the fifth exemplary embodiment. FIG. 10 is a diagram illustrating a configuration example of a signal selection unit according to a sixth embodiment; 14 is a flowchart illustrating an example of processing according to the sixth exemplary embodiment.

  Hereinafter, preferred embodiments of the disclosed technology will be described in detail with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a diagram illustrating a configuration example of an OADM according to the first embodiment. An OADM 100 illustrated in FIG. 1 is a wavelength multiplexing apparatus according to the first embodiment. As shown in FIG. 1, the OADM 100 includes couplers 111 and 112, a receiver 120, a signal selector 130, a demultiplexer 140, receivers 151 to 15n, transmitters 161 to 16n, and a multiplexer. 170, a transmission unit 180, an input-side OCM 191 (Optical Channel Monitor), and an output-side OCM 192.

  A wavelength-multiplexed WDM optical signal is input to the OADM 100. The coupler 111 branches the WDM optical signal input to the OADM 100 and outputs each branched WDM optical signal to the receiving unit 120 and the input side OCM 191. The receiving unit 120 receives and amplifies the WDM optical signal output from the coupler 111. The receiving unit 120 outputs the amplified WDM optical signal to the signal selecting unit 130.

  The signal selection unit 130 includes a wavelength multiplexing filter that performs wavelength multiplexing of an optical signal. Specifically, the signal selection unit 130 performs signal selection for each channel of the WDM optical signal output from the reception unit 120. For example, the signal selection unit 130 branches the WDM optical signal output from the reception unit 120. Then, the signal selection unit 130 outputs one of the branched WDM optical signals to the demultiplexing unit 140. In addition, the signal selection unit 130 performs signal selection for each channel between the other of the branched WDM optical signals and the WDM optical signal output from the multiplexing unit 170, and the WDM optical signal subjected to signal selection is selected. Is output to the transmission unit 180.

  The demultiplexer 140 demultiplexes the WDM optical signal output from the signal selector 130 and outputs the demultiplexed optical signals to the receivers 151 to 15n. Each of the receivers 151 to 15n receives the optical signal transmitted from the demultiplexing unit 140. Thereby, an optical signal of an arbitrary channel included in the WDM optical signal received by the receiving unit 120 can be received (dropped). The transmitters 161 to 16n output optical signals having different wavelengths to the multiplexing unit 170, respectively. Multiplexer 170 multiplexes the optical signals output from transmitters 161-16 n and outputs the multiplexed WDM optical signal to signal selector 130.

  The transmission unit 180 amplifies the WDM optical signal output from the signal selection unit 130 and transmits the amplified WDM optical signal to the subsequent stage of the OADM 100. The coupler 112 branches a part of the WDM optical signal transmitted by the transmission unit 180 and outputs the branched WDM optical signal to the output OCM 192.

  The input-side OCM 191 is an input-side acquisition unit that acquires the spectrum of an optical signal input to the signal selection unit 130 (wavelength multiplexing filter). Specifically, the input-side OCM 191 monitors the power (spectrum) at each wavelength of the optical signal for each optical signal included in the WDM optical signal output from the coupler 111. The input side OCM 191 outputs the monitor result to the signal selection unit 130.

  The output-side OCM 192 is an output-side acquisition unit that acquires the spectrum of the optical signal output from the signal selection unit 130 (wavelength multiplexing filter). Specifically, the output OCM 192 monitors the power (spectrum) at each wavelength of the optical signal for each optical signal included in the WDM optical signal output from the coupler 112. The output side OCM 192 outputs the monitor result to the signal selection unit 130.

  In addition, although the structure which provides the coupler 111 in the front | former stage of the receiving part 120 was demonstrated, it is good also as a structure which provides the coupler 111 between the receiving part 120 and the signal selection part 130. FIG. Further, although the configuration in which the coupler 112 is provided in the subsequent stage of the transmission unit 180 has been described, the coupler 112 may be provided between the signal selection unit 130 and the transmission unit 180.

  FIG. 2 is a diagram of a configuration example of the signal selection unit according to the first embodiment. As shown in FIG. 2, the signal selection unit 130 includes a coupler 210, demultiplexing units 221 and 222, switches 231 to 23 m, variable attenuators 241 to 24 m, a multiplexing unit 250, and an attenuation control unit 260. A threshold storage unit 270, a detection unit 280, and a filter control unit 290.

  The coupler 210 branches the WDM optical signal output from the receiving unit 120 and outputs each branched WDM optical signal to the demultiplexing unit 140 (see FIG. 1) and the demultiplexing unit 221. The demultiplexing unit 221 demultiplexes the WDM optical signal output from the coupler 210. The demultiplexing unit 221 outputs the demultiplexed optical signals to the switches 231 to 23m, respectively. The demultiplexing unit 222 demultiplexes the WDM optical signal output from the multiplexing unit 170 (see FIG. 1). The demultiplexing unit 222 outputs the demultiplexed optical signals to the switches 231 to 23m, respectively.

  Each of the switches 231 to 23m selects one of the optical signal output from the demultiplexing unit 221 and the optical signal output from the demultiplexing unit 222. The switches 231 to 23m output the selected optical signals to the variable attenuators 241 to 24m, respectively. By controlling the switches 231 to 23m, an optical signal of an arbitrary channel included in the WDM optical signal received by the receiving unit 120 can be output (through) to the subsequent stage. Further, by controlling the switches 231 to 23m, an optical signal of an arbitrary channel included in the WDM optical signal output from the demultiplexing unit 222 can be output (added) to the subsequent stage.

  The variable attenuators 241 to 24m attenuate the optical signals output from the switches 231 to 23m, respectively, according to the control of the attenuation amount control unit 260. Each of the variable attenuators 241 to 24 m outputs the attenuated optical signal to the multiplexing unit 250. The multiplexing unit 250 multiplexes each optical signal output from the variable attenuators 241 to 24m. Multiplexer 250 outputs the multiplexed WDM optical signal to transmitter 180.

  Here, the demultiplexing unit 221 and the multiplexing unit 250 are wavelength multiplexing filters that perform wavelength multiplexing of optical signals. For these wavelength division multiplexing filters, filters capable of shifting wavelength transmission characteristics by external control are used. For example, a filter capable of controlling wavelength transmission characteristics at a temperature such as AWG (Array Waveguide Gratings) can be used as the wavelength multiplexing filter.

  Alternatively, a WSS (Wavelength Selectable Switch) liquid crystal type or the like may be used for the wavelength multiplexing filter. Alternatively, the wavelength multiplexing filter may be a filter such as LCOS (Liquid Crystal On Silicon) that can control wavelength transmission characteristics with a voltage or current.

  Based on the power of each channel output from the output-side OCM 192, the attenuation amount control unit 260 controls each attenuation amount of the variable attenuators 241 to 24m so that the power of each channel becomes a target value. Alternatively, the attenuation amount control unit 260 may set the gain of each channel to a target value based on the power of each channel output from the output-side OCM 192 and the power of each channel output from the input-side OCM 191. Each attenuation may be controlled.

  The threshold storage unit 270 stores a threshold for each type of optical signal (see, for example, FIG. 12). The detection unit 280 detects a shift in wavelength transmission characteristics of the wavelength multiplexing filters (for example, the demultiplexing unit 221 and the multiplexing unit 250) in the OADM 100 based on the difference between the spectra acquired by the input side OCM 191 and the output side OCM 192. It is a detection unit.

  In addition, the detection unit 280 may detect the direction (wavelength direction) of wavelength transmission characteristic deviation based on the difference between the spectra acquired by the input-side OCM 191 and the output-side OCM 192. Further, the detection unit 280 may detect a shift in wavelength transmission characteristics that exceeds a threshold value stored in the threshold value storage unit 270. The detection unit 280 outputs the detection result of the wavelength transmission characteristic deviation to the filter control unit 290.

  The filter control unit 290 is a characteristic control unit that controls the wavelength transmission characteristics of the wavelength multiplexing filters (for example, the demultiplexing unit 221 and the multiplexing unit 250) based on the detection result output from the detection unit 280. For example, the filter control unit 290 shifts the wavelength transmission characteristic of the wavelength multiplexing filter in the direction opposite to the shift direction detected by the detection unit 280.

  FIG. 3 is a graph showing optical signal loss due to a shift in wavelength transmission characteristics of the wavelength multiplexing filter. In FIG. 3, the horizontal axis indicates the wavelength. The wavelength λs on the horizontal axis indicates the wavelength (center wavelength) of the optical signal. The vertical axis represents the loss of the optical signal. A characteristic 301 indicates a loss characteristic of the optical signal in the case where there is no shift in wavelength transmission characteristics in the wavelength multiplexing filters such as the demultiplexing unit 221 and the multiplexing unit 250. As shown by the characteristic 301, when there is no shift in the wavelength transmission characteristic of the wavelength multiplexing filter, the loss of the optical signal is minimum (L0) at the wavelength λs of the optical signal.

  A characteristic 302 indicates a loss characteristic of the optical signal when the wavelength transmission characteristic of the wavelength multiplexing filter is shifted to the long wavelength side. A characteristic 303 indicates a loss characteristic of the optical signal when the wavelength transmission characteristic of the wavelength multiplexing filter is shifted to the short wavelength side. As shown by the characteristics 302 and 303, when the wavelength multiplex filter has a shift in wavelength transmission characteristics, a loss L1 (> L0) occurs at the wavelength λs of the optical signal. As described above, when a wavelength transmission characteristic shift occurs in the wavelength multiplexing filters such as the demultiplexing unit 221 and the multiplexing unit 250, the loss of the optical signal increases.

  FIG. 4 is a diagram illustrating a configuration example 1 of the OCM. Although a configuration example of the input side OCM 191 is described in FIG. 4, the same applies to the configuration of the output side OCM 192. As shown in FIG. 4, the input side OCM 191 includes a diffraction grating 410 and a PD array 420. The diffraction grating 410 spatially demultiplexes the optical signal input to the input side OCM 191 for each wavelength. Each optical signal demultiplexed by the diffraction grating 410 is output to the PD array 420.

  The PD array 420 includes a plurality of PDs, and each of the wavelengths separated by the diffraction grating 410 is received by the plurality of PDs. In addition, the PD array 420 outputs each signal indicating the light reception power in a plurality of PDs. Thereby, the power (spectrum) of each wavelength of the optical signal input to the input side OCM 191 can be obtained. Moreover, since the power of each wavelength can be monitored simultaneously, a highly accurate spectrum can be obtained.

  FIG. 5 is a diagram illustrating a configuration example 2 of the OCM. Although a configuration example of the input side OCM 191 will be described in FIG. 5, the configuration of the output side OCM 192 is the same. As illustrated in FIG. 5, the input-side OCM 191 may include a variable filter 510 and a PD 520. The variable filter 510 transmits the optical signal input to the input side OCM 191 to the PD 520. In addition, the variable filter 510 temporally changes the band through which the optical signal is transmitted.

  The PD 520 receives the optical signal transmitted through the variable filter 510 and outputs a signal indicating the received light power. Thereby, the power (spectrum) of each wavelength of the optical signal input to the input side OCM 191 can be obtained. The variable filter 510 may be, for example, a filter that changes the wavelength transmission characteristics by changing the refractive index of the thin film with a heater, or a filter that changes the wavelength transmission characteristics by moving the thin film mechanically. Thereby, since the input side OCM 191 can be realized with a small number of PDs, the cost of the input side OCM 191 can be reduced.

  FIG. 6 is a diagram illustrating a configuration example 3 of the OCM. In FIG. 6, the same components as those shown in FIG. The input-side OCM 191 and the output-side OCM 192 shown in FIG. 1 may be realized by the OCM 600 shown in FIG. The OCM 600 includes a switch 610, a variable filter 510, and a PD 520.

  The switch 610 temporally switches between the optical signal output from the coupler 111 and the optical signal output from the coupler 112 and outputs the optical signal to the variable filter 510. The variable filter 510 transmits the optical signal output from the switch 610. Thereby, the power (spectrum) of each wavelength can be obtained for each optical signal output from the couplers 111 and 112. Thereby, the input side OCM 191 and the output side OCM 192 can be realized by one OCM 600.

  FIG. 7 is a graph showing an example of measurement by an input-side OCM of a 40 Gbps optical signal. 7 and 8 show measurement examples of a 40 Gbps optical signal included in the WDM optical signal input to the signal selection unit 130. FIG. In FIG. 7, the horizontal axis indicates the wavelength, and the vertical axis indicates the power of the optical signal. A spectrum 710 is a spectrum of a 40 Gbps optical signal input to the input side OCM 191.

  Measurement points 711 to 715 are measurement points by the input side OCM 191. The wavelengths of the measurement points 711 to 715 are i-2, i-1, i, i + 1, and i + 2, respectively. In addition, the powers of the measurement points 711 to 715 measured by the input-side OCM 191 (relative values with respect to the peak, the same applies hereinafter) are Pin (i−2), Pin (i−1), Pin (i), and Pin (i + 1), respectively. , Pin (i + 2).

  FIG. 8 is a graph illustrating an example of measurement by the output-side OCM of a 40 Gbps optical signal. In FIG. 8, the horizontal axis indicates the wavelength, and the vertical axis indicates the power and transmittance of the optical signal. A spectrum 810 is a spectrum of a 40 Gbps optical signal included in the optical signal input to the output side OCM 192. Measurement points 811 to 815 are measurement points by the output side OCM 192.

  The wavelengths of the measurement points 811 to 815 are i−2, i−1, i, i + 1, and i + 2 which are the same as the measurement points 711 to 715 of the input-side OCM 191, respectively. Further, the powers of the measurement points 811 to 815 measured by the output-side OCM 192 (relative values with respect to the peak, the same applies hereinafter) are respectively set to Pout (i−2), Pout (i−1), Pout (i), and Pout (i + 1). , Pout (i + 2).

  A wavelength transmission characteristic 820 indicates a wavelength transmission characteristic for an optical signal of a wavelength multiplexing filter such as the demultiplexing unit 221 or the multiplexing unit 250. In the example shown in FIG. 8, the wavelength transmission characteristics of the wavelength multiplexing filter are shifted to the short wavelength side. In this case, the wavelength 821 having the highest transmittance in the wavelength transmission characteristic 820 is shifted to the shorter wavelength side than the center wavelength λs of the optical signal.

  For this reason, in the spectrum 810, the power on the longer wavelength side than the center wavelength λs is attenuated. Therefore, the power Pout (i + 1) indicated by the measurement point 814 is smaller than the power Pin (i + 1) indicated by the measurement point 714 in FIG. Further, the power Pout (i + 2) indicated by the measurement point 815 is smaller than the power Pin (i + 2) indicated by the measurement point 715 in FIG.

  When there is no deviation in the wavelength transmission characteristics of wavelength multiplexing filters such as the demultiplexing unit 221 and the multiplexing unit 250, the spectrum 810 has almost the same waveform as the spectrum 710. Therefore, Pin (i-2), Pin (i-1), Pin (i), Pin (i + 1), and Pin (i + 2) are Pout (i-2), Pout (i-1), and Pout (i, respectively. ), Pout (i + 1), Pout (i + 2).

  FIG. 9 is a graph (part 1) illustrating a measurement example by OCM of a 10 Gbps optical signal. 9 and 10 show measurement examples of a 10 Gbps optical signal included in the WDM optical signal input to the signal selection unit 130. FIG. In FIG. 9, the horizontal axis indicates the wavelength, and the vertical axis indicates the power of the optical signal. A spectrum 910 is a spectrum of a 10 Gbps optical signal input to the input side OCM 191.

  Measurement points 911 to 915 are measurement points by the input side OCM 191. The wavelengths of the measurement points 911 to 915 are i-2, i-1, i, i + 1, and i + 2, respectively. The powers of the measurement points 911 to 915 are Pin (i−2), Pin (i−1), Pin (i), Pin (i + 1), and Pin (i + 2), respectively.

  FIG. 10 is a graph (part 2) illustrating an example of measurement by an OCM of a 10 Gbps optical signal. In FIG. 10, the horizontal axis indicates the wavelength, and the vertical axis indicates the power of the optical signal. A spectrum 1010 is a spectrum of a 10 Gbps optical signal included in the WDM optical signal input to the output side OCM 192. Measurement points 1011 to 1015 are measurement points by the output side OCM 192.

  The wavelengths of the measurement points 1011 to 1015 are the same wavelengths i−2, i−1, i, i + 1, and i + 2 as the measurement points 911 to 915 of the input-side OCM 191, respectively. The powers of the measurement points 1011 to 1015 are Pout (i−2), Pout (i−1), Pout (i), Pout (i + 1), and Pout (i + 2), respectively.

  In the example shown in FIG. 10, the wavelength transmission characteristics of wavelength multiplexing filters such as the demultiplexing unit 221 and the multiplexing unit 250 are shifted to the short wavelength side. In this case, in the spectrum 1010, the power on the longer wavelength side than the center wavelength λs is attenuated, similarly to the spectrum 810. Therefore, the power Pout (i + 1) indicated by the measurement point 1014 is smaller than the power Pin (i + 1) indicated by the measurement point 914 in FIG. Further, the power Pout (i + 2) indicated by the measurement point 1015 is smaller than the power Pin (i + 2) indicated by the measurement point 915 in FIG.

  When there is no deviation in wavelength transmission characteristics of wavelength multiplexing filters such as the demultiplexing unit 221 and the multiplexing unit 250, the spectrum 1010 has almost the same waveform as the spectrum 910. Therefore, Pin (i-2), Pin (i-1), Pin (i), Pin (i + 1), and Pin (i + 2) are Pout (i-2), Pout (i-1), and Pout (i, respectively. ), Pout (i + 1), Pout (i + 2).

  FIG. 11 is a graph showing the relationship between the shift of the wavelength transmission characteristic of the wavelength multiplexing filter and the penalty of the optical signal. In FIG. 11, the horizontal axis indicates a shift in wavelength transmission characteristics in wavelength multiplexing filters such as the demultiplexing unit 221 and the multiplexing unit 250. The vertical axis indicates the penalty (for example, Q value) of the optical signal due to the shift of the wavelength transmission characteristic of the wavelength multiplexing filter. The penalty allowable value 1110 is an allowable value of the penalty of the optical signal defined by the system.

  A characteristic 1101 indicates a penalty characteristic with respect to a shift of the wavelength transmission characteristic of the wavelength division multiplexing filter in a 40 Gbps DPSK (Differential Phase Shift Keying) optical signal. A characteristic 1102 indicates a penalty characteristic with respect to a shift of the wavelength transmission characteristic of the wavelength multiplexing filter in an optical signal of 40 Gbps DQPSK (Differential Quadrature Phase Shift Keying). A characteristic 1103 indicates a penalty characteristic with respect to a shift of the wavelength transmission characteristic of the wavelength multiplexing filter in an optical signal of 10 Gbps NRZ (Non Return to Zero).

  The threshold values TH_a1 to TH_c1 are threshold values for shifting wavelength transmission characteristics. Specifically, the threshold value TH_a1 corresponds to the magnitude of the shift of the wavelength transmission characteristic of the wavelength multiplexing filter in which the optical signal reaches the penalty allowable value 1110 in the characteristic 1101. The threshold value TH_b1 corresponds to the magnitude of the shift of the wavelength transmission characteristic of the wavelength multiplexing filter where the optical signal reaches the penalty allowable value 1110 in the characteristic 1102. The threshold value TH_c1 corresponds to the magnitude of deviation of the wavelength transmission characteristic of the wavelength multiplexing filter in which the optical signal reaches the penalty allowable value 1110 in the characteristic 1103.

  As indicated by the characteristics 1101 to 1103, the penalty characteristic with respect to the shift of the wavelength transmission characteristic varies depending on the type of the signal speed of the optical signal, the modulation method, and the like. For this reason, as indicated by the threshold values TH_a1 to TH_c1, the magnitude of the shift in the wavelength transmission characteristic at which the optical signal reaches the penalty allowable value 1110 also differs depending on the type of the optical signal, such as the signal speed and the modulation method. In the example of FIG. 11, the threshold value TH_a1 is the smallest and the threshold value TH_c1 is the largest.

  FIG. 12 is a diagram illustrating an example of the threshold value stored in the threshold value storage unit. The threshold storage unit 270 (for example, see FIG. 2) of the signal selection unit 130 stores, for example, a table 1200 shown in FIG. In the table 1200, the type of optical signal is associated with a threshold value. Specifically, a threshold TH_c1 is associated with NRZ of 10 Gbps. Also, the threshold TH_b1 is associated with 40 Gbps DQPSK. A threshold TH_a1 is associated with 40 Gbps DPSK. The table 1200 is created in advance based on the characteristics 1101 to 1103 and the penalty allowable value 1110 shown in FIG. 11, for example, and is stored in the threshold storage unit 270.

  FIG. 13 is a flowchart of an example of processing according to the first embodiment. The detection unit 280 and the filter control unit 290 (see, for example, FIG. 2) execute the following steps, for example, for the optical signals of the respective channels included in the WDM optical signal. First, the filter control unit 290 determines the type of the target optical signal (step S1301).

  Next, the detection unit 280 acquires the spectrum (input spectrum) of the target optical signal from the input-side OCM 191 (step S1302). For example, the detection unit 280 has powers Pin (i−2), Pin (i−1), Pin (i), and Pin (i + 1) at wavelengths i−2, i−1, i, i + 1, and i + 2 of the optical signal. , Pin (i + 2).

  Next, the detection unit 280 acquires the spectrum (output spectrum) of the target optical signal from the output OCM 192 (step S1303). For example, the detection unit 280 includes powers Pout (i−2), Pout (i−1), Pout (i), and Pout (i + 1) at wavelengths i−2, i−1, i, i + 1, and i + 2 of the optical signal. , Pout (i + 2).

  Next, the detection unit 280 calculates the difference between the input power and the output power of the target optical signal based on the spectrum acquired in step S1302 and the spectrum acquired in step S1303 (step S1304).

  Next, the detection unit 280 acquires a threshold value corresponding to the type of the optical signal determined in step S1301 from the threshold value storage unit 270 (step S1305). Next, the detection unit 280 determines whether or not the difference calculated in step S1304 is larger than the threshold acquired in step S1305 (step S1306). If the difference is not greater than the threshold value (step S1306: No), the series of processing ends.

  If the difference is larger than the threshold value in step S1306 (step S1306: YES), the detection unit 280 determines that a shift in wavelength transmission characteristics of the wavelength multiplexing filter exceeding the penalty allowable value 1110 has occurred, and proceeds to step S1307. . That is, the detection unit 280 determines whether or not the direction of the wavelength transmission characteristic shift is the short wavelength direction based on the difference between the spectrum acquired in step S1302 and the spectrum acquired in step S1303 (step S1303). S1307).

  For example, when Pin (i + 2)> Pout (i + 2) and Pin (i−2) ≦ Pout (i−2), the detection unit 280 determines that the shift direction is the short wavelength direction. In addition, when Pin (i + 2) ≦ Pout (i + 2) and Pin (i−2)> Pout (i−2), the detection unit 280 determines that the shift direction is the long wavelength direction.

  If the wavelength transmission characteristic shift direction is the short wavelength direction in step S1307 (step S1307: Yes), the filter control unit 290 shifts the wavelength transmission characteristic of the wavelength multiplexing filter to the long wavelength side (step S1308). Then, a series of processing is completed. For example, the filter control unit 290 shifts the wavelength transmission characteristics of at least one of the demultiplexing unit 221 and the multiplexing unit 250 to the long wavelength side.

  If the wavelength transmission characteristic shift direction is not the short wavelength direction in step S1307 (step S1307: No), the filter control unit 290 shifts the wavelength transmission characteristic of the wavelength multiplexing filter to the short wavelength side (step S1309). A series of processing ends. For example, the filter control unit 290 shifts the wavelength transmission characteristics of at least one of the demultiplexing unit 221 and the multiplexing unit 250 to the short wavelength side.

  Here, the case where the respective powers at the wavelengths i-2, i-1, i, i + 1, i + 2 of the optical signal are acquired has been described, but in general, the wavelengths ix,..., I,. , I + x may be acquired (in the above example, x = 2). In step S1307, if the direction of deviation cannot be determined, a series of processing may be terminated.

  Moreover, although the case where the difference between the input power and the output power and the threshold value are compared in step S1306 has been described, when the variable attenuators 241 to 24M perform constant level control, the loss amounts of the variable attenuators 241 to 24M You may compare with a threshold value.

  FIG. 14 is a diagram illustrating an example of a communication system to which OADM is applied. A communication system 1400 shown in FIG. 14 is a communication system to which the OADM 100 shown in FIG. 1 is applied. The communication system 1400 includes OADMs 1411 to 1415, a transmitter 1420, and a receiver 1430. The OADMs 1411 to 1415 are connected to each other in a ring shape.

  The transmitter 1420 is connected to the OADM 1411. The receiver 1430 is connected to the OADM 1414. The OADM 100 illustrated in FIG. 1 can be applied to at least one of the OADMs 1411 to 1415. In the communication system 1400, a line 1401 is set in which the optical signal transmitted from the transmitter 1420 is relayed in the order of OADMs 1411, 1412, 1413, and 1414 and received by the receiver 1430.

  FIG. 15 is a diagram illustrating a determination example 1 of the type of the optical signal. In FIG. 15, the same components as those shown in FIG. In the communication system 1400, the communication state is managed by the operation system 1510 (OpS). The operation system 1510 transmits a control signal including the type of optical signal to be transmitted to each of the OADMs 1411 to 1415.

  For example, in step S1301 illustrated in FIG. 13, the filter control unit 290 determines the type of the target optical signal based on the control signal transmitted by the operation system 1510. As described above, the filter control unit 290 can determine the type of the optical signal based on the control signal from the operation system 1510 that is the host system.

  FIG. 16 is a diagram illustrating a determination example 2 of the type of the optical signal. In FIG. 16, the same parts as those shown in FIG. 7 or FIG. As shown in the spectrum 710 and the spectrum 910, the spectrum of the optical signal varies depending on the type of the optical signal. Therefore, the detection unit 280 stores various types of spectra of the optical signal in advance, and determines the type of the optical signal based on the power (spectrum) of each wavelength output from the input side OCM 191 and the output side OCM 192. be able to.

  As described above, according to the OADM 100 according to the first embodiment, each spectrum of the optical signal before and after the wavelength multiplexing filter that performs wavelength multiplexing of the optical signal is acquired, and the difference of each acquired spectrum is used to obtain the wavelength multiplexing filter. A shift in wavelength transmission characteristics can be directly detected. Thereby, the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter can be detected accurately.

  Further, the wavelength transmission characteristic of the wavelength multiplexing filter is detected by detecting the direction of deviation of the wavelength transmission characteristic of the wavelength multiplexing filter using the difference of each spectrum and controlling the wavelength transmission characteristic of the wavelength multiplexing filter based on the detected direction of deviation. The deviation of the transmission characteristics can be accurately corrected. For this reason, the reliability of a communication system (for example, communication system 1400) can be improved.

  In addition, the OADM 100 may be provided with a notification unit that notifies the user of the detection result of the wavelength transmission characteristic deviation of the wavelength multiplexing filter. As a result, the user can adjust the wavelength transmission characteristics of the wavelength multiplexing filter, replace the wavelength multiplexing filter, and the like. For this reason, the reliability of a communication system (for example, communication system 1400) can be improved.

(Embodiment 2)
A configuration example of the wavelength division multiplexing apparatus according to the second exemplary embodiment is the same as that of the OADM 100 illustrated in FIG.

  FIG. 17 is a diagram of a configuration example of the signal selection unit according to the second embodiment. In FIG. 17, the same components as those shown in FIG. As illustrated in FIG. 17, the signal selection unit 130 according to the second embodiment may be configured to omit the filter control unit 290 illustrated in FIG. 2. The detection unit 280 outputs the detection result of the wavelength transmission characteristic shift to the attenuation amount control unit 260.

  The attenuation amount control unit 260 has a function as a blocking control unit that blocks the optical signal based on the detection result of the wavelength transmission characteristic deviation output from the detection unit 280. Specifically, the attenuation amount control unit 260 maximizes the attenuation amount of the variable attenuator corresponding to the channel in which the shift of the wavelength transmission characteristic is detected by the detection unit 280 among the variable attenuators 241 to 24m. Thereby, it is possible to block the optical signal of the channel in which the shift of the wavelength transmission characteristic is detected.

  FIG. 18 is a diagram illustrating an example of the threshold value stored in the threshold value storage unit. The threshold storage unit 270 (for example, see FIG. 17) of the signal selection unit 130 stores, for example, a table 1800 shown in FIG. In the table 1800, the type of the optical signal and the filter control threshold are associated with each other. Specifically, a threshold TH_c2 is associated with NRZ of 10 Gbps. A threshold TH_b2 is associated with 40 Gbps DQPSK. The threshold TH_a2 is associated with 40 Gbps DPSK. The table 1800 is created in advance based on, for example, the characteristics 1101 to 1103 shown in FIG. 11 and the penalty allowance allowed by the system, and is stored in the threshold storage unit 270.

  FIG. 19 is a flowchart of an example of processing according to the second embodiment. The detection unit 280 and the attenuation amount control unit 260 (see, for example, FIG. 17) execute, for example, the following steps for the optical signals of the respective channels included in the WDM optical signal. Steps S1901 to S1906 shown in FIG. 19 are the same as steps S1301 to S1306 shown in FIG. If the difference is larger than the threshold value in step S1906 (step S1906: Yes), the attenuation amount control unit 260 blocks the target optical signal (step S1907), and ends the series of processes. Thereby, the channel in which the shift of the wavelength transmission characteristic of the wavelength multiplexing filter exceeds the threshold can be shut down.

  FIG. 20 is a diagram illustrating an example of a communication system to which OADM is applied. 20, the same components as those illustrated in FIG. 14 are denoted by the same reference numerals, and description thereof is omitted. A communication system 1400 illustrated in FIG. 20 is a communication system to which the OADM 100 including the signal selection unit 130 illustrated in FIG. 17 is applied. A communication system 1400 shown in FIG. 20 has redundant lines. The communication system 1400 includes a coupler 2010 and a switch 2020 in addition to the configuration shown in FIG.

  The coupler 2010 branches the optical signal transmitted from the transmitter 1420. The optical signal branched by the coupler 2010 is transmitted to the OADM 1414 through a line 2001 that relays in the order of the OADMs 1411, 1415, and 1414 and a line 2002 that relays in the order of the OADMs 1411, 1412, 1413, and 1414.

  The switch 2020 outputs either the optical signal transmitted to the OADM 1414 via the line 2001 or the optical signal transmitted to the OADM 1414 via the line 2002 to the receiver 1430. The receiver 1430 receives the optical signal output from the switch 2020. Here, the switch 2020 outputs the optical signal transmitted to the OADM 1414 via the line 2001 to the receiver 1430. In this case, the line 2001 becomes a working line, and the line 2002 becomes a redundant line.

  FIG. 21 is a diagram illustrating an example of occurrence of signal interruption in a communication system line. In FIG. 21, the same components as those shown in FIG. In the communication system 1400 shown in FIG. The disconnection of the line 2001 is detected by the switch 2020, for example.

  When the switch 2020 detects a signal disconnection on the line 2001, the switch 2020 outputs an optical signal transmitted to the OADM 1414 via the line 2002 to the receiver 1430. Accordingly, the line between the transmitter 1420 and the receiver 1430 can be switched from the line 2001 to the line 2002, and communication between the transmitter 1420 and the receiver 1430 can be continued.

  In the communication system 1400 having such a redundant line, for example, it is assumed that the detection unit 280 of the OADM 1415 detects a deviation exceeding the threshold value of the wavelength transmission characteristic of the wavelength multiplexing filter. In this case, the attenuation amount control unit 260 of the OADM 1411 blocks the optical signal in which the deviation exceeding the threshold is detected. As a result, the signal is disconnected on the line 2001, and the line between the transmitter 1420 and the receiver 1430 is switched from the line 2001 to the line 2002 by the switch 2020.

  As described above, the OADM 100 according to the second embodiment acquires each spectrum of the optical signal before and after the wavelength multiplexing filter that performs wavelength multiplexing of the optical signal, and uses the difference between the acquired spectra to transmit the wavelength of the wavelength multiplexing filter. Detect deviations in characteristics. Thereby, the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter can be detected accurately.

  Further, by blocking the optical signal based on the detection result of the shift of the wavelength transmission characteristic of the wavelength multiplexing filter, it is possible to shut down the channel having the shifted wavelength transmission characteristic. For example, when applied to a communication system having a redundant configuration (for example, the communication system 1400 shown in FIG. 20), when the wavelength transmission characteristic is shifted, the communication quality can be improved by switching to another line. Further, even in a communication system without a redundant configuration, it is possible to avoid continuing transmission of an optical signal with a wavelength transmission characteristic shifted. For this reason, the reliability of a communication system (for example, communication system 1400) can be improved.

(Embodiment 3)
FIG. 22 is a diagram of a configuration example of the OADM according to the third embodiment. 22, the same components as those illustrated in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. As illustrated in FIG. 22, the OADM 100 according to the third embodiment includes an OSC transmission unit 2210, a coupler 2220, and an OSC reception unit 2230 in addition to the configuration illustrated in FIG. In this case, the input side OCM 191 shown in FIG. 1 may be omitted.

  The output side OCM 192 outputs the monitor result to the signal selection unit 130 and the OSC transmission unit 2210. The OSC transmission unit 2210 outputs the monitoring result output from the output side OCM 192 to the coupler 2220 as an OSC (Optical Supervisor Channel) signal. The coupler 112 outputs the WDM optical signal output from the transmission unit 180 to the coupler 2220.

  The coupler 2220 combines the WDM optical signal output from the coupler 112 with the OSC signal output from the OSC transmission unit 2210, and transmits the combined WDM optical signal to the subsequent stage of the OADM 100. As a result, the monitoring result of the optical signal output from the wavelength multiplexing filter can be transmitted to the communication device subsequent to the OADM 100.

  Similarly, the communication device in the previous stage of the OADM 100 monitors the spectrum of the optical signal output from the wavelength multiplexing filter and transmits an OSC signal including the monitoring result to the OADM 100. The coupler 111 branches the WDM optical signal transmitted from the communication device in the previous stage of the OADM 100 and outputs each branched WDM optical signal to the receiving unit 120 and the OSC receiving unit 2230.

  The OSC reception unit 2230 is an input side acquisition unit that acquires the spectrum of the optical signal input to the signal selection unit 130 (wavelength multiplexing filter). Specifically, the OSC receiving unit 2230 receives an OSC signal included in the optical signal output from the coupler 111. The OSC reception unit 2230 outputs the spectrum included in the received OSC signal to the signal selection unit 130.

  FIG. 23 is a diagram of a configuration example of the signal selection unit according to the third embodiment. In FIG. 23, the same components as those shown in FIG. As illustrated in FIG. 23, the detection unit 280 detects a shift in wavelength transmission characteristics of the wavelength multiplexing filter in the OADM 100 based on the difference between the spectra acquired by the OSC reception unit 2230 and the output-side OCM 192.

  As described above, the OADM 100 according to the third embodiment acquires each spectrum of the optical signal before and after the wavelength multiplexing filter that performs wavelength multiplexing of the optical signal, and uses the difference between the acquired spectra to transmit the wavelength of the wavelength multiplexing filter. Detect deviations in characteristics. Thereby, the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter can be detected accurately.

  The OADM 100 acquires the spectrum of the optical signal before the wavelength multiplexing filter by receiving it from the communication device that transmitted the optical signal. Accordingly, for example, a shift in wavelength transmission characteristics of the wavelength multiplexing filter can be accurately detected without providing the input-side OCM 191 that monitors the spectrum of the optical signal in front of the wavelength multiplexing filter.

(Embodiment 4)
FIG. 24 is a diagram illustrating a configuration example of a TERM according to the fourth embodiment. In FIG. 24, the same components as those shown in FIG. A TERM 2400 illustrated in FIG. 24 is a wavelength multiplexing apparatus according to the fourth embodiment. The TERM 2400 is a transmission node (terminal node) that transmits a WDM optical signal. The TERM 2400 includes a coupler 112, a signal selection unit 130, transmitters 161 to 16n, a multiplexing unit 170, a transmission unit 180, and an output-side OCM 192.

  FIG. 25 is a diagram of a configuration example of a signal selection unit according to the fourth embodiment. In FIG. 25, the same components as those shown in FIG. As illustrated in FIG. 25, the signal selection unit 130 includes a demultiplexing unit 222, variable attenuators 241 to 24m, a multiplexing unit 250, an attenuation control unit 260, a threshold storage unit 270, and a detection unit 280. And a filter control unit 290.

  The demultiplexing unit 222 outputs the demultiplexed optical signals to the variable attenuators 241 to 24m, respectively. The variable attenuators 241 to 24 m attenuate the respective optical signals output from the demultiplexing unit 222 according to the control of the attenuation amount control unit 260.

  The detection unit 280 is a calculation unit that calculates an inverted spectrum obtained by inverting the spectrum acquired by the output-side OCM 192 in the wavelength direction around the center wavelength λs (for example, ITU-grid) of the optical signal. The detection unit 280 is a detection unit that detects a shift in the wavelength transmission characteristics of the wavelength multiplexing filter based on the difference between the spectrum acquired by the output-side OCM 192 and the calculated inverted spectrum.

  FIG. 26 is a graph illustrating an example of measurement by the output-side OCM of a 40 Gbps optical signal. FIGS. 26 and 27 show measurement examples of a 40 Gbps optical signal included in the WDM optical signal output from the signal selection unit 130. In FIG. 26, the horizontal axis indicates the wavelength, and the vertical axis indicates the power of the optical signal. A spectrum 2610 is a spectrum of a 40 Gbps optical signal input to the output side OCM 192.

  Measurement points 2611 to 2615 are measurement points by the output side OCM 192. The wavelengths of the measurement points 2611 to 2615 are i-2, i-1, i, i + 1, and i + 2, respectively. Further, the powers of the measurement points 2611 to 2615 measured by the output side OCM 192 are Pin (i−2), Pin (i−1), Pin (i), Pin (i + 1), and Pin (i + 2), respectively. In the example shown in FIG. 26, the wavelength transmission characteristics of the wavelength multiplexing filter are shifted to the short wavelength side. In this case, the spectrum 2610 attenuates the power on the longer wavelength side than the center wavelength λs. Therefore, the spectrum 2610 has an asymmetric waveform with the center wavelength λs as the center.

  FIG. 27 is a graph illustrating an example of an inverted spectrum of a 40 Gbps optical signal. In FIG. 27, the same parts as those shown in FIG. In FIG. 27, the horizontal axis indicates the wavelength, and the vertical axis indicates the power of the optical signal. An inversion spectrum 2710 is an inversion spectrum obtained by inverting the spectrum 2610 shown in FIG. 26 in the wavelength direction around the center wavelength λs of the optical signal.

  Measurement points 2711 to 2715 are measurement points at which power is calculated by the detection unit 280. The wavelengths of the measurement points 2711 to 2715 are i−2, i−1, i, i + 1, and i + 2, which are the same as those of the measurement points 2611 to 2615, respectively. Further, the powers of the measurement points 2711 to 2715 calculated by the detection unit 280 are Pout (i−2), Pout (i−1), Pout (i), Pout (i + 1), and Pout (i + 2), respectively.

  Since the spectrum 2610 has an asymmetric waveform with the center wavelength λs as the center, the inverted spectrum 2710 and the spectrum 2610 have different waveforms. Specifically, in the spectrum 2610, since the power on the longer wavelength side than the center wavelength λs is attenuated, the power of the inverted spectrum 2710 is higher than the power of the spectrum 2610 on the longer wavelength side than the center wavelength λs. On the other hand, the power of the spectrum 2610 is higher than the power of the inverted spectrum 2710 on the shorter wavelength side than the center wavelength λs.

  Accordingly, the power Pout (i + 1) indicated by the measurement point 2714 is higher than the power Pin (i + 1) indicated by the measurement point 2614. Further, the power Pout (i + 2) indicated by the measurement point 2715 is higher than the power Pin (i + 2) indicated by the measurement point 2615 in FIG.

  When there is no deviation in the wavelength transmission characteristics of the wavelength multiplexing filter such as the multiplexing unit 250, the spectrum 2610 has a symmetrical waveform with the center wavelength λs as the center. For this reason, the inverted spectrum 2710 has substantially the same waveform as the spectrum 2610. Therefore, Pin (i-2), Pin (i-1), Pin (i), Pin (i + 1), and Pin (i + 2) are Pout (i-2), Pout (i-1), and Pout (i, respectively. ), Pout (i + 1), Pout (i + 2).

  FIG. 28 is a flowchart illustrating an example of processing according to the fourth embodiment. The detection unit 280 and the filter control unit 290 (see, for example, FIG. 25) execute, for example, the following steps for the optical signals of the respective channels included in the WDM optical signal. First, the filter control unit 290 determines the type of the target optical signal (step S2801).

  Next, the detection unit 280 acquires the spectrum (output spectrum) of the target optical signal from the output OCM 192 (step S2802). For example, the detection unit 280 has powers Pin (i−2), Pin (i−1), Pin (i), and Pin (i + 1) at wavelengths i−2, i−1, i, i + 1, and i + 2 of the optical signal. , Pin (i + 2).

  Next, the detection unit 280 performs inversion of the spectrum acquired in step S2802 (step S2803). By the inversion operation in step S2803, the detection unit 280, for example, each power Pout (i-2), Pout (i-1), Pout (i) at wavelengths i-2, i-1, i, i + 1, i + 2 of the optical signal. ), Pout (i + 1), Pout (i + 2).

  Next, the detection unit 280 calculates the power difference between the input spectrum of the target optical signal and the inverted spectrum (each spectrum) based on the spectrum acquired in step S2802 and the inverted spectrum obtained in step S2803. (Step S2804).

  Steps S2805 to S2809 shown in FIG. 28 are the same as steps S1305 to S1309 shown in FIG. However, in step S2807, the detection unit 280 determines that the direction of deviation is the short wavelength direction when Pin (i + 2)> Pout (i + 2) and Pin (i−2) ≦ Pout (i−2). To do. In addition, when Pin (i + 2) ≦ Pout (i + 2) and Pin (i−2)> Pout (i−2), the detection unit 280 determines that the shift direction is the long wavelength direction.

  As described above, the TERM 2400 according to the fourth embodiment acquires the spectrum of the optical signal after the wavelength multiplexing filter that performs wavelength multiplexing of the optical signal, and calculates the inverted spectrum obtained by inverting the acquired spectrum in the wavelength direction. And the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter is detected using the difference of the acquired spectrum and the calculated inversion spectrum. Thereby, the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter can be detected accurately.

  Further, the wavelength transmission characteristic of the wavelength multiplexing filter is detected by detecting the direction of deviation of the wavelength transmission characteristic of the wavelength multiplexing filter using the difference of each spectrum and controlling the wavelength transmission characteristic of the wavelength multiplexing filter based on the detected direction of deviation. The deviation of the transmission characteristics can be accurately corrected. For this reason, the reliability of a communication system can be improved.

(Embodiment 5)
A configuration example of the wavelength division multiplexing apparatus according to the fifth embodiment is the same as that of the TERM 2400 illustrated in FIG.

  FIG. 29 is a diagram of a configuration example of a signal selection unit according to the fifth embodiment. 29, the same components as those illustrated in FIG. 25 are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 29, the signal selection unit 130 according to the fifth embodiment may be configured without the filter control unit 290 shown in FIG. The detection unit 280 outputs the detection result of the wavelength transmission characteristic shift to the attenuation amount control unit 260.

  The attenuation amount control unit 260 has a function as a blocking control unit that blocks the optical signal based on the detection result of the wavelength transmission characteristic deviation output from the detection unit 280. Specifically, the attenuation amount control unit 260 maximizes the attenuation amount of the variable attenuator corresponding to the channel in which the shift of the wavelength transmission characteristic is detected by the detection unit 280 among the variable attenuators 241 to 24m. Thereby, it is possible to block the optical signal of the channel in which the shift of the wavelength transmission characteristic is detected. About the threshold value memorize | stored in the threshold value memory | storage part 270, it is the same as that of the table 1800 shown in FIG.

  FIG. 30 is a flowchart of an example of processing according to the fifth embodiment. The detection unit 280 and the attenuation amount control unit 260 (see, for example, FIG. 29) execute, for example, the following steps for the optical signals of the respective channels included in the WDM optical signal. Steps S3001 to S3006 shown in FIG. 30 are the same as steps S2801 to S2806 shown in FIG. In step S3006, when the difference is larger than the threshold (step S3006: Yes), the attenuation amount control unit 260 blocks the target optical signal (step S3007), and ends the series of processes. Thereby, the channel in which the shift of the wavelength transmission characteristic of the wavelength multiplexing filter exceeds the threshold can be shut down.

  As described above, the TERM 2400 according to the fifth embodiment acquires the spectrum of the optical signal after the wavelength multiplexing filter that performs wavelength multiplexing of the optical signal, and calculates the inverted spectrum obtained by inverting the acquired spectrum in the wavelength direction. And the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter is detected using the difference of the acquired spectrum and the calculated inversion spectrum. Thereby, the shift | offset | difference of the wavelength transmission characteristic of a wavelength multiplexing filter can be detected accurately.

  Also, by blocking the optical signal based on the detected wavelength transmission characteristic deviation of the wavelength multiplexing filter, it is possible to shut down the channel having the wavelength transmission characteristic deviation. For example, by applying to a communication system having a redundant configuration, when the wavelength transmission characteristic is shifted, it is possible to switch to another line and improve communication quality. Further, even in a communication system without a redundant configuration, it is possible to avoid continuing transmission of an optical signal with a wavelength transmission characteristic shifted. For this reason, the reliability of a communication system can be improved.

(Embodiment 6)
A configuration example of the wavelength division multiplexing apparatus according to the sixth embodiment is the same as that of the TERM 2400 illustrated in FIG.

  FIG. 31 is a diagram illustrating a configuration example of a signal selection unit according to the sixth embodiment. In FIG. 31, the same components as those shown in FIG. 25 are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 31, in the signal selection unit 130 according to the sixth embodiment, the detection unit 280 outputs the detection result of the shift in wavelength transmission characteristics to either the filter control unit 290 or the attenuation amount control unit 260. .

  The attenuation amount control unit 260 has a function as a blocking control unit that blocks the optical signal based on the detection result of the wavelength transmission characteristic deviation output from the detection unit 280. Specifically, among the variable attenuators 241 to 24m, the attenuation amount of the variable attenuator corresponding to the channel in which the shift of the wavelength transmission characteristic is detected by the detection unit 280 is maximized. Thereby, it is possible to block the optical signal of the channel in which the shift of the wavelength transmission characteristic is detected.

  FIG. 32 is a flowchart of an example of processing according to the sixth embodiment. The attenuation amount control unit 260, the detection unit 280, and the filter control unit 290 (see, for example, FIG. 31) execute, for example, the following steps for the WDM optical signal. First, the detection unit 280 performs processing for detecting a shift in wavelength transmission characteristics of the wavelength multiplexing filter for each channel included in the target WDM optical signal (step S3201).

  Step S3201 can be realized, for example, by performing steps S2801 to S2806 shown in FIG. 28 for each channel. For example, if the difference is larger than the threshold value in step S2806, it is determined that there is a shift in wavelength transmission characteristics of the wavelength multiplexing filter for the target channel. On the other hand, when the difference is equal to or smaller than the threshold, it is determined that there is no shift in wavelength transmission characteristics of the wavelength multiplexing filter for the target channel.

  Next, the detection unit 280 determines whether or not a shift in wavelength transmission characteristic has been detected for at least one of the channels in step S3201 (step S3202). If no shift in wavelength transmission characteristic is detected for any channel (step S3202: No), the series of processing ends.

  If a shift in wavelength transmission characteristic is detected for at least one of the channels in step S3202 (step S3202: Yes), whether or not a shift in wavelength transmission characteristic is detected in only one channel in step S3201. Is determined (step S3203). If a shift in wavelength transmission characteristics is detected for only one channel (step S3203: YES), the attenuation control unit 260 determines that the wavelength of the light source has shifted, and the process proceeds to step S3204. In other words, the attenuation amount control unit 260 blocks the optical signal of the channel in which the wavelength transmission characteristic shift is detected (step S3204), and ends the series of processes.

  If a shift in wavelength transmission characteristic is detected in a plurality of channels in step S3203 (step S3203: No), the attenuation amount control unit 260 determines that the wavelength transmission characteristic of the wavelength multiplexing filter has shifted, and the process proceeds to step S3205. To do. Steps S3205 to S3207 shown in FIG. 32 are the same as steps S2807 to S2809 shown in FIG.

  As described above, the TERM 2400 according to the sixth embodiment performs detection processing of a shift in wavelength transmission characteristics for each optical signal of a plurality of channels output from the signal selection unit 130 (wavelength multiplexing filter). When the wavelength transmission characteristics of the wavelength multiplexing filter deviate, the wavelength transmission characteristics usually shift in a plurality of channels. For this reason, when a shift in wavelength transmission characteristics is detected in only one channel, it is considered that the wavelength of the light source has shifted. Therefore, when a shift in wavelength transmission characteristic is detected in only one channel, the optical signal of the channel in which the shift in wavelength transmission characteristic is detected is blocked. As a result, the channel whose light source wavelength is shifted can be shut down.

  Further, when a shift in wavelength transmission characteristics is detected in a plurality of channels, it is considered that the wavelength transmission characteristics of the wavelength multiplexing filter have shifted. This is because the wavelength of the light source is normally controlled for each channel. Therefore, when a shift in wavelength transmission characteristic is detected in a plurality of channels, the shift in wavelength transmission characteristic of the wavelength multiplexing filter can be accurately corrected by controlling the wavelength transmission characteristic of the wavelength multiplexing filter. For this reason, the reliability of a communication system (for example, communication system 1400) can be improved.

  As described above, according to the wavelength division multiplexing apparatus and the detection method, it is possible to accurately detect a shift in wavelength transmission characteristics of the wavelength division multiplexing filter. In each of the above-described embodiments, the OADM 100 and the TERM 2400 are illustrated as wavelength multiplexing filters that perform wavelength multiplexing of optical signals. However, the wavelength multiplexing filter is not limited to the OADM 100 or the TERM 2400, and may be any filter that performs wavelength multiplexing of an optical signal and has wavelength transmission characteristics.

  The following additional notes are disclosed with respect to the above-described embodiments.

(Appendix 1) a wavelength multiplexing filter that performs wavelength multiplexing of an optical signal;
An input side acquisition unit for acquiring a spectrum of an optical signal input to the wavelength multiplexing filter;
An output side acquisition unit for acquiring a spectrum of an optical signal output from the wavelength multiplexing filter;
A detection unit for detecting a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectra acquired by the input side acquisition unit and the output side acquisition unit;
A wavelength division multiplexing apparatus comprising:

(Appendix 2) The detection unit detects the direction of the shift,
The wavelength multiplexing apparatus according to claim 1, further comprising a characteristic control unit that controls wavelength transmission characteristics of the wavelength multiplexing filter based on a direction detected by the detection unit.

(Supplementary note 3) The wavelength division multiplexing apparatus according to Supplementary note 1 or 2, further comprising: a cutoff control unit that cuts off the optical signal when the deviation is detected by the detection unit.

(Additional remark 4) The said input side acquisition part receives and acquires the spectrum of the said input optical signal from the communication apparatus which transmitted the said optical signal, Any one of Additional remark 1-3 characterized by the above-mentioned. The wavelength division multiplexing apparatus described.

(Additional remark 5) The wavelength division multiplexing apparatus as described in any one of additional remarks 1-4 provided with the notification part which notifies a user the detection result by the said detection part.

(Appendix 6) A wavelength multiplexing filter for performing wavelength multiplexing of an optical signal;
An acquisition unit for acquiring a spectrum of an optical signal output from the wavelength multiplexing filter;
A calculation unit that calculates a spectrum obtained by inverting the spectrum acquired by the acquisition unit in the wavelength direction;
A detection unit that detects a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectrum acquired by the acquisition unit and the spectrum calculated by the calculation unit;
A wavelength division multiplexing apparatus comprising:

(Supplementary Note 7) The detection unit performs the shift detection process for each optical signal of a plurality of channels output from the wavelength multiplexing filter,
A blocking control unit that blocks an optical signal of the one channel when the shift of only one channel is detected by the detection unit;
A characteristic control unit that controls transmission characteristics of the wavelength multiplexing filter when the shift of the plurality of channels is detected by the detection unit;
The wavelength division multiplexing apparatus according to appendix 6, further comprising:

(Additional remark 8) In the detection method of a wavelength multiplexing apparatus provided with the wavelength multiplexing filter which performs wavelength multiplexing of an optical signal,
A first acquisition step of acquiring a spectrum of an optical signal input to the wavelength multiplexing filter;
A second acquisition step of acquiring a spectrum of the optical signal output from the wavelength multiplexing filter;
A detection step of detecting a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectra acquired by the first acquisition step and the second acquisition step;
A detection method comprising:

(Additional remark 9) In the detection method of a wavelength multiplexing apparatus provided with the wavelength multiplexing filter which performs wavelength multiplexing of an optical signal,
An acquisition step of acquiring a spectrum of the optical signal output from the wavelength multiplexing filter;
A calculation step of calculating a spectrum obtained by inverting the spectrum acquired in the acquisition step in the wavelength direction;
A detection step of detecting a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectrum acquired by the acquisition step and the spectrum calculated by the calculation step;
A detection method comprising:

111, 112, 210, 2010, 2220 Coupler 120 Receiver 140, 221, 222 Demultiplexer 170, 250 Multiplexer 180 Transmitter 241-24m Variable attenuator 410 Diffraction grating 420 PD array 711-715, 811-815 911 to 915, 1011 to 1015, 2611 to 2615, 2711 to 2715 Measurement point 820 Wavelength transmission characteristic 1400 Communication system 1401, 2001, 2002 Line 2710 Inverted spectrum

Claims (8)

A wavelength multiplexing filter for performing wavelength multiplexing of an optical signal;
An input side acquisition unit for acquiring a spectrum of an optical signal input to the wavelength multiplexing filter;
An output side acquisition unit for acquiring a spectrum of an optical signal output from the wavelength multiplexing filter;
A detection unit for detecting a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectra acquired by the input side acquisition unit and the output side acquisition unit;
A wavelength division multiplexing apparatus comprising: The detection unit detects the direction of the shift,
The wavelength multiplexing apparatus according to claim 1, further comprising a characteristic control unit that controls wavelength transmission characteristics of the wavelength multiplexing filter based on a direction detected by the detection unit.   The wavelength division multiplexing apparatus according to claim 1, further comprising: a blocking control unit configured to block the optical signal when the shift is detected by the detection unit.   The wavelength according to any one of claims 1 to 3, wherein the input-side acquisition unit receives and acquires a spectrum of the input optical signal from a communication device that has transmitted the optical signal. Multiplex device. A wavelength multiplexing filter for performing wavelength multiplexing of an optical signal;
An acquisition unit for acquiring a spectrum of an optical signal output from the wavelength multiplexing filter;
A calculation unit that calculates a spectrum obtained by inverting the spectrum acquired by the acquisition unit in the wavelength direction;
A detection unit that detects a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectrum acquired by the acquisition unit and the spectrum calculated by the calculation unit;
A wavelength division multiplexing apparatus comprising: The detection unit performs the shift detection process for each optical signal of a plurality of channels output from the wavelength multiplexing filter,
A blocking control unit that blocks an optical signal of the one channel when the shift of only one channel is detected by the detection unit;
A characteristic control unit that controls transmission characteristics of the wavelength multiplexing filter when the shift of the plurality of channels is detected by the detection unit;
The wavelength multiplexing device according to claim 5, further comprising: In a detection method of a wavelength multiplexing device including a wavelength multiplexing filter that performs wavelength multiplexing of an optical signal,
A first acquisition step of acquiring a spectrum of an optical signal input to the wavelength multiplexing filter;
A second acquisition step of acquiring a spectrum of the optical signal output from the wavelength multiplexing filter;
A detection step of detecting a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectra acquired by the first acquisition step and the second acquisition step;
A detection method comprising: In a detection method of a wavelength multiplexing device including a wavelength multiplexing filter that performs wavelength multiplexing of an optical signal,
An acquisition step of acquiring a spectrum of the optical signal output from the wavelength multiplexing filter;
A calculation step of calculating a spectrum obtained by inverting the spectrum acquired in the acquisition step in the wavelength direction;
A detection step of detecting a shift in wavelength transmission characteristics of the wavelength multiplexing filter based on a difference between the spectrum acquired by the acquisition step and the spectrum calculated by the calculation step;
A detection method comprising:

Images