Method for detecting wavelength deviation

Abstract

A detector 50 disclosed herein detects a wavelength deviation of a signal according to whether a multiplexer output to which a signal is added is an intensity corresponding to the addition.

Description

Wavelength deviation detection method

[0001] The present disclosure relates to a method for detecting wavelength shifts.

[0002] An All Photonic Network (APN) has been proposed (see, for example, Non-Patent Document 1). Generally, an APN comprises, as in-station devices, an APN gateway (APN-G), an APN exchange (APN-I), and a controller that controls them. Generally, an APN also comprises, as in-home devices, an APN transceiver (APN-T), a terminal equipped with an APN-T, and other terminals. An APN-G transmits and receives wavelength-multiplexed signals to and from other APN-Gs and APN-Is.

[0003] In this way, there is a possibility that wavelength deviations may occur in the multiplexed signals. However, in the conventional configuration, there is no established method for detecting wavelength deviations in the individual multiplexed signals.

[0004] Open All-Photonic Network Functional Architecture, Version 2.0, October 19, 2023. https: / / iowngf. org / wp-content / uploads / formidable / 21 / IOWN-GF-RD-Open_APN_Functional_Architecture-2.0. pdf

[0005] The present disclosure aims to provide a method for detecting wavelength shift.

[0006] To achieve the above object, the present disclosure employs a technique of adding a signal to the input of a combiner and detecting a wavelength shift depending on whether the output from the combiner shows an increase in intensity in response to the addition of the signal.

[0007] Specifically, the detector of the present disclosure detects the wavelength shift of a signal based on whether the output of a multiplexer to which a signal has been added has an intensity corresponding to the addition. Here, the multiplexer may be a multiplexer / demultiplexer. In other words, the detector detects the wavelength shift of the added signal from its matching wavelength based on whether the output from the multiplexer when a signal, for example a signal from a terminal, is added to the input to the multiplexer that multiplexes wavelengths has an increased intensity corresponding to the addition of the signal. Note that addition also includes negative addition, i.e., deletion.

[0008] Furthermore, the detection method of the present disclosure detects a wavelength shift of the added signal depending on whether the output of a multiplexer to which a signal has been added has an intensity corresponding to the addition. Here, the multiplexer may be a multiplexer / demultiplexer. In other words, a signal, for example, a signal from a terminal, is added to the input of a multiplexer that multiplexes wavelengths, and the wavelength shift of the added signal from its matching wavelength is detected depending on whether the output from the multiplexer has an increased intensity corresponding to the addition of the signal.

[0009] Furthermore, the wavelength deviation may be detected based on a difference in the output intensity of the multiplexer before and after the addition. Here, the multiplexer may be a multiplexer / demultiplexer. In other words, the output intensity from the multiplexer before and after the addition of the signal may be acquired, and the wavelength deviation from the compatible wavelength of the added signal may be detected based on the difference in the acquired intensities.

[0010] Alternatively, the total intensity after the multiplexer may be estimated according to the output intensity of the signal to be added or the input intensity to the multiplexer, and the wavelength deviation may be detected based on the estimated value and the actual measured value. For example, the total intensity after the multiplexer may be estimated according to the intensity of the added signal before the multiplexer, and the wavelength deviation may be detected based on the estimated value and the actual measured value. Alternatively, the intensity of the added signal before the multiplexer may be acquired, and an estimate of the total intensity of the added signal after the multiplexer and one or more signals input to the multiplexer before the addition may be calculated according to the intensity of the added signal before the multiplexer, and the wavelength deviation of the added signal from the matching wavelength may be detected based on the estimate and the actual measured value of the intensity of the output from the multiplexer. Here, the multiplexer may be a multiplexer / demultiplexer.

[0011] Alternatively, the intensity after the multiplexer may be estimated according to the intensity of a signal added to a device upstream of the multiplexer, and the wavelength deviation may be detected based on the estimated value and the actual measured value. Alternatively, the intensity of the signal, for example, the signal input from a terminal, may be acquired from a device upstream of the multiplexer, for example, an optical switch, to which the signal is input, and an estimated value of the total intensity of the added signal after the multiplexer and one or more signals input to the multiplexer before the addition according to the intensity of the added signal input to the device upstream of the multiplexer, and the wavelength deviation of the added signal from the compatible wavelength may be detected based on the estimated value and the actual measured value of the intensity of the output from the multiplexer. Here, the multiplexer may be a multiplexer / demultiplexer.

[0012] Furthermore, a pumping control value for the optical amplifier output from the multiplexer may be estimated according to the strength of the additional signal before the multiplexer, and the wavelength shift may be detected based on the estimated value and the actual measured value. Optical amplifier control includes control to maintain a constant gain regardless of addition or deletion of input light or increase or decrease in input signal strength, or control to maintain a constant sum of output strengths (constant output strength). To maintain a constant gain, it is necessary to increase the pumping strength in accordance with an increase in input signal strength due to the addition of input light. In the case of optical pumping, the pumping strength is increased. In the case of current pumping, such as in a semiconductor optical amplifier, the applied current is increased. To increase the pumping strength, for example, the applied current of the pumping light source is increased. To maintain a constant output strength, it is necessary to decrease the pumping strength in accordance with an increase in input signal strength. In the case of optical pumping, the pumping strength is decreased. In the case of current pumping, the applied current is decreased. To decrease the pumping strength, for example, the applied current of the pumping light source is decreased. When adjusting the input attenuation or output attenuation of an optical amplifier, attenuation is performed according to the increase. In either case, in the case of wavelength misalignment, the multiplexer or multiplexer / demultiplexer attenuates the signal more excessively than in the case of an appropriate wavelength, resulting in a smaller added input intensity, and the multiplexer control value is smaller than estimated. That is, if the gain is constant, the increase in pump light intensity, the increase in applied current, and the increase in applied current of the pump light source will be smaller than estimated, and the added input intensity can be estimated from these values. If the output intensity is constant, the decrease in pump light intensity, the decrease in applied current, the decrease in applied current of the pump light source, and the increase in attenuation will be smaller than estimated, and the added input intensity can be estimated from these values. Therefore, for example, the method may: acquire the added signal intensity before the multiplexer / combiner; calculate the pump light intensity, current value, pump light source current value, and attenuation of the attenuator at the optical amplifier output from the multiplexer according to the added signal intensity before the multiplexer; and detect wavelength misalignment from the matched wavelength based on the calculated optical intensity, current value, and attenuation and the actual measured values ​​of the optical intensity, current value, and attenuation of the optical amplifier.

[0013] Furthermore, the intensities of the multiple signals input to the multiplexer may be constant either at their outputs, or at a device input upstream of the multiplexer or at the input to the multiplexer, and the output intensity from the multiplexer may be estimated, and the wavelength shift may be detected based on the estimated value and the actual measured value. In other words, the output intensity of the signals from the multiple terminals, the input intensity of the signals to an optical switcher equipped with the multiplexer, for example, the input intensity of the signals input from the multiple terminals, or the input intensity of the signals input to the multiplexer may be constant, thereby estimating the output intensity from the multiplexer, and the wavelength shift from the compatible wavelength may be detected based on the estimated output intensity and the actually measured output intensity from the multiplexer.

[0014] The above disclosures can be combined as much as possible.

[0015] According to the present disclosure, wavelength shift can be detected.

[0016] FIG. 1 shows an example of the configuration of an APN. FIG. 2 is a diagram illustrating an overview of the wavelength shift detection method of the present disclosure, where (A) shows a light intensity measurement before multiplexing an additional signal, and (B) shows a light intensity measurement after multiplexing an additional signal. FIG. 3 shows an example of the configuration of a detector. FIG. 4 shows an example of a wavelength shift detection method. FIG. 5 shows an example of a wavelength shift detection method. FIG. 6 shows an example of a wavelength shift detection method. FIG. 7 shows an example of a wavelength shift detection method. FIG. 8 shows an example of a wavelength shift detection method. FIG. 9 shows an example of a wavelength shift detection method. FIG. 10 shows an example of a wavelength shift detection method. FIG. 11 shows an example of a wavelength shift detection method. FIG. 12 is a graph illustrating the number of detectable paths according to significant digits. FIG. 13 is a graph illustrating the relationship between the number of paths and the additional intensity increment required for detection.

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0018] (Configuration of Network System) Fig. 1 shows an example of the configuration of a network system. The network system of the present disclosure is an All Photonic Network (APN) that includes an APN gateway (hereinafter abbreviated as "APN-G") 92, an APN exchange (hereinafter abbreviated as "APN-I") 93, and a controller 91, which function as in-station devices. The APN includes, as in-home devices, an APN transceiver (hereinafter abbreviated as "APN-T"), a terminal 83 equipped with the APN-T, and a termination device 94. However, a configuration that does not include the APN-I 93 may also be adopted.

[0019] The APN-G92 sets routes connecting the terminals 83 and termination devices 94 that transmit and receive the fiber path signals, which are main signals, and the wavelength path signals, to the opposing devices, and loops back the wavelength path signals, wavelength multiplexed signals, and fiber path signals within the APN-G92 or forwards them to the opposing devices via the APN-I93 or another APN-G92. The APN-G92 also sets routes connecting the terminals 83 and termination devices 94 that transmit and receive control signals to the controller 91, and terminates control signals from the terminals 83 and termination devices 94 within the APN-G92 or directly to the controller 91, and terminates control signals from the controller 91 within the APN-G92 or directly to the terminals 83 and termination devices 94. For example, in the configuration of FIG. 1, if the controller 91 and the terminals 83 and termination devices 94 transmit and receive control signals directly, the APN-G92 only forwards them without transmitting or receiving them. For transmission and reception, for example, a fiber cross connect (FXC) 71, which is an optical switch that distributes optical path routes as optical signals, a wavelength selective switch (WSS) 72 that multiplexes / demultiplexes optical signals of wavelength paths and switches their routes, an optical amplifier 73, a return unit 74, an arrayed wavelength grating (AWG) that multiplexes / demultiplexes optical signals of wavelength paths, etc. can be used. The AWG can be used as an optical multiplexer (MUX) and an optical demultiplexer (DEMUX), or as part thereof. The AWG and WSS 72 function as a "multiplexer," a "demultiplexer," and a "multiplexer / demultiplexer." In this application, attention is focused on the multiplexing function of a multiplexer and a multiplexer / demultiplexer. For this reason, the terms "multiplexer" or "multiplexer or multiplexer / demultiplexer" will be used to represent "multiplexer," "demultiplexer," and "multiplexer / demultiplexer." The APN-G92 functions as an "optical switch."

[0020] (Overview of Wavelength Shift Detection) An overview of a wavelength shift detection method according to the present disclosure will be described with reference to Fig. 2. The present disclosure employs a technique in which a signal is added to the input of a multiplexer (e.g., WSS 72), and wavelength shift is detected based on whether the output from the multiplexer (e.g., WSS 72) shows an increase in intensity in response to the addition of the signal.

[0021] Therefore, a multiplexer to which the present application can be applied is premised on the premise that the attenuation of an optical signal having an inappropriate wavelength is greater when the transmitted optical signal has an inappropriate wavelength than when the transmitted optical signal has an appropriate wavelength. Therefore, the application of the present application to a WSS in which there is no difference in attenuation between an optical signal having an appropriate wavelength and an optical signal having an inappropriate wavelength at the time of multiplexing wavelength signals during wavelength multiplexing, such as a multicast switch (MCS) that multiplexes using an optical coupler and then demultiplexes using a wavelength filter, is limited.

[0022] That is, even in a wavelength division multiplexing device in which optical signals with incompatible wavelengths are not significantly attenuated during wavelength multiplexing, the wavelength multiplexed signal is demultiplexed into individual wavelengths, so the intensity after demultiplexing can be determined from the decrease in intensity of signals with incompatible wavelengths due to wavelength shifts.

[0023] However, in a system in which optical attenuation does not change even with incompatible wavelengths when multiplexing with MCS or the like, it is fine if the range of wavelengths that other signals multiplexed with the optical signal of the incompatible wavelength do not include wavelengths with which the optical signal of the incompatible wavelength is shifted, but if the range of wavelengths with which the wavelength is shifted is not included, the optical signal of the incompatible wavelength with a shifted wavelength will be included in the other optical signals and will be demultiplexed, which poses a serious problem.

[0024] In APN-G92, wavelength elements such as AWG and WSS72 are used to multiplex main signals of multiple wavelengths (multiple wavelength signals) to generate a wavelength multiplexed signal, or to separate a wavelength multiplexed signal to generate main signals of different wavelengths (different wavelength signals). Specifically, wavelength elements such as wavelength filters, AWGs, and WSS72 are wavelength-dependent loss elements, and when a signal passes through them, there is little loss if the wavelength assigned to the main signal is appropriate, but there is a large loss if the wavelength is inappropriate.

[0025] Therefore, in the present disclosure, the increase in intensity of the signal (wavelength multiplexed signal in which one or more wavelength signals are multiplexed) that has passed through the wavelength-dependent loss element before the initial connection or switched additional signal is multiplexed ( FIG. 2(A) ) and after the multiplexing ( FIG. 2(B) ) is detected, and if the increase is not in accordance with the addition, the wavelength of the added signal (added wavelength signal) is detected as an inappropriate wavelength.

[0026] The number of additions may be a negative value. For example, minus one means the deletion of one path. When the number of additions is a negative number, an increase in intensity and an increase (increment) become a decrease in intensity and a decrease (decrement). Intensity can be converted to other optical intensities such as optical amplitude, but in this application, optical power is mainly used. Therefore, intensity is interpreted as optical power. This also applies to the following embodiments. In the case of addition, a wavelength shift is detected when the increase in the multiplexer output intensity is smaller than the increase that matches the input intensity of the added path. In the case of deletion, a wavelength shift is detected when the decrease in the multiplexer output intensity is smaller than the decrease that matches the input intensity of the deleted path. In other words, a wavelength shift is detected when the increase or decrease in the multiplexer output is small.

[0027] Therefore, the amount of wavelength shift can be estimated based on the smallness of the increment. The reason why the increase or decrease in the multiplexer output is smaller than that for the correct wavelength is because the difference in intensity (loss, attenuation) before and after the wavelength element of the optical path with the incorrect wavelength is greater than the value for the correct wavelength. Therefore, wavelength shift can be detected when the difference in intensity before and after the wavelength element of the path being added (or deleted) itself is large. However, in this application, the judgment is primarily based on the smallness of the increase or decrease in the wavelength-multiplexed signal output from the multiplexer. The appropriate loss amount can also be stored in advance, or measured by inputting reference light and then divided by the difference in attenuation due to the wavelength of the transmission line or wavelength-dependent loss element from the measured value of the reference light. It is easier to calculate the appropriate increment by storing the measurement results of the input intensity of the added signal and the appropriate loss when the signal passes through the wavelength element when the signal is at the correct wavelength.

[0028] Here, when a wavelength signal is added to a wavelength multiplexed signal in which one or more wavelength signals are multiplexed, the added wavelength signal (target signal) may coexist with other signals different from the added wavelength signal (target signal) (one or more existing wavelength signals that were included in the wavelength multiplexed signal before the target signal was multiplexed). Therefore, when detecting wavelength shifts, it is important to confirm that there is no change in the intensity of the other signals when the other signals are multiplexed. In the present disclosure, it is confirmed that there is no change in the input intensity of the other signals (excluding the influence of fluctuations in the existing signals). Details of excluding the influence of fluctuations in the existing signals will be described later.

[0029] Furthermore, in the present disclosure, if it is concluded that the cause of the insufficient output of the target signal is wavelength misalignment, to confirm that the insufficient input is not the cause, it is confirmed that the input intensity of the target signal is a predetermined value. Specifically, in the present disclosure, whether the input intensity of the target signal is a predetermined value is actually measured. Therefore, in the present disclosure, the input intensity when there is no wavelength misalignment is stored in advance.

[0030] The present disclosure is applicable to the extent that intensity changes due to additional signals can be measured, depending on the precision and accuracy of the detector, which will be described in detail later.

[0031] (Excluding the influence of fluctuations in existing signals) The absence of changes in the intensity of the wavelength-multiplexed signal due to fluctuations in the existing signal can be determined by checking that there is no change in the input intensity of the existing signal before and after the addition of the additional signal. If there is a change, the addition of the additional signal is temporarily removed and then re-added. Then, after confirming that there is no change in the input intensity of the existing signal before and after the addition of the additional signal, wavelength shift is determined.

[0032] Furthermore, after measuring the input strength of the existing signal and the strength of the wavelength-multiplexed signal, a signal is added, and if the input signal strength does not change before and after the addition, it is determined whether or not there is a wavelength shift. If the input signal strength of the existing signal changes before and after the addition, it is considered that it was not possible to determine whether there was a wavelength shift with this addition, so it is possible to retry by deleting and adding.

[0033] Furthermore, after measuring the input strength of an existing signal and the strength of a wavelength-multiplexed signal, if a signal is added and there is an existing signal whose input signal strength changes before and after the addition, the change in output corresponding to the change in input strength of the signal that has changed may be subtracted and compared.

[0034] (Configuration of detector) Next, the configuration of a detector 50 for detecting wavelength shift will be described with reference to Fig. 3. When configuring an APN-G using a ROADM or the like as in Non-Patent Document 1, one objective of the present disclosure is to utilize ROADM hardware that wavelength-division multiplexes signals using wavelength-dependent loss elements, thereby monitoring wavelength shifts without any additional hardware.

[0035] The detector 50 includes a receiving unit 51, a detecting unit 52, and a determining unit 53. The receiving unit 51 includes a pre-multiplexing receiving unit 51A, a post-multiplexing receiving unit 51B, and a setting receiving unit 51C. The detecting unit 52 includes a pre-multiplexing detecting unit 52A and a post-multiplexing detecting unit 52B. However, it is sufficient for the detector 50 to include either the receiving unit 51 or the detecting unit 52. The detector 50 may also have a function to remove the influence of fluctuations in the above-mentioned existing signal and a function to previously store the input intensity when there is no wavelength shift.

[0036] The detector 50 then detects the wavelength shift of the signal based on whether the output of the multiplexer to which the signal has been added has an intensity corresponding to the addition. In other words, the detector 50 detects the wavelength shift from the compatible wavelength based on whether the output when a signal, for example, a signal from a certain terminal 83, is added to a wavelength-dependent loss element, for example, an AWG or WSS 72, which multiplexes / demultiplexes the wavelengths of signals from a plurality of terminals 83, has an increased intensity corresponding to the addition of the signal.

[0037] Specifically, the minimum configuration for the detector 50 to obtain the intensity or intensity information after wavelength multiplexing using a wavelength-dependent loss element is to include either a post-multiplexing receiver 51B or a post-multiplexing detector 52B. For example, the detector 50 receives or detects a value and detects a wavelength shift if the difference from the previous value is not a predetermined value. The predetermined value is the constant value if the intensity per path is constant after multiplexing and increases or decreases with each pass, or an integer multiple of the value if the intensity increases or decreases with each multiple pass. If the detected value deviates from the predetermined value, the detector 50 determines that the added path itself is out of sync if only one path is added, or that one or all of the added paths are out of sync if multiple paths are added. The detector 50 may be equipped with both the receiver 51 and the detector 52 and calibrate these values ​​using statistical processing or the like.

[0038] Similarly, the minimum configuration for detector 50 to obtain intensity and intensity information before multiplexing using a wavelength-dependent loss element is to include either a pre-multiplexing receiver 51 A or a pre-multiplexing detector 52 A. Pre-multiplexing receiver 51 A and pre-multiplexing detector 52 A may be provided and used separately for each signal (wavelength signal) to be multiplexed or for each path to be multiplexed, or both may be provided and their values ​​may be calibrated by statistical processing or the like.

[0039] An example of how to calculate an estimated value is shown below. For example, it is assumed that a portion of a path input to a multiplexer passes through several optical amplifiers at only one stage each, that a plurality of optical amplifiers 73 through which a portion of a path input to the multiplexer passes are provided before multiplexing, that the input optical power to the optical amplifiers of a path that passes through an optical amplifier and inputs to the multiplexer is the same as the input optical power to the multiplexer of a path that does not pass through an optical amplifier and inputs to the multiplexer, and that either a new path is added or a portion of an existing path is deleted.

[0040] First, let's assume that the optical amplifier is operating in AGC (Automatic Gain Control) mode with a constant gain. In AGC mode, the optical power of the path passing through the optical amplifier is the intensity obtained by adding the gain to the value before input to the optical amplifier if the display is logarithmic, or multiplying it by the gain if the display is linear. The following will be shown in linear format, but the same calculation can be done with a logarithmic format.

[0041] Specifically, the input optical power to the optical amplifier of the path that passes through the optical amplifier and inputs to the multiplexer and the input optical power to the multiplexer of the path that does not pass through the optical amplifier and inputs to the multiplexer are P, the optical amplifier j (j=1 to jmax) through which the path input to the multiplexer passes, the gain of the optical amplifier j is the AGC value j, and the number of input paths to the optical amplifier j is n0. ｊ , input path n0 to optical amplifier j ｊ The number of paths whose outputs are multiplexed by the multiplexer is n ｊ , the number of paths that do not pass through the optical amplifier is nx, and the number of input paths to one optical amplifier i (1≦i≦jmax) among the optical amplifiers j is n0′ ｉ From n0' ｉ The number of paths input from the optical amplifier i to the multiplexer is n ｉ From n' ｉ That is, by adding a path (either adding or deleting), the number of input paths to the multiplexer becomes nx + n ｉ +Σn ｊ (j≠i, 1≦j≦jmax) to nx+n' ｉ +Σn ｊ (j≠i, 1≦j≦jmax).

[0042] The number of paths of this optical amplifier i is n ｉ , n0 ｉ From n' ｉ , n0' ｉWhen increasing or decreasing the number of paths, the determining unit 53 uses the difference between the following values ​​before and after the increase or decrease: Before increase or decrease: constant value P×number of paths not passing through an optical amplifier nx+(constant value P×AGC value i)×n ｉ +Σ(constant value P×AGC value j)×n ｊ (j≠i, 1≦j≦jmax) After increase or decrease: constant value P×number of paths not passing through an optical amplifier nx+(constant value P×AGC value i)×n' ｉ +Σ(constant value P×AGC value j)×n ｊ (j≠i, 1≦j≦jmax) That is, the increase (or decrease) in the multiplexer output is P×AGC value i×(n' ｉ -n ｉ ), and if the change is smaller than that, the determining unit 53 determines that there is a wavelength shift in one of the added paths (or one of the deleted paths).

[0043] For example, if one path with a wavelength shift is increased or decreased, P x AGC value i x n ｉ is P x AGC value i x n' ｉ = P × AGC value i × (n ｉ ±1), and P × AGC value i × (n ｉ +α) < P × AGC value i × (n ｉ +1) = P × AGC value i × n' ｉ or P × AGC value i × (n ｉ −α)>P×AGC value i×(n ｉ -1) = P × AGC value i × n' ｉ , 0≦α<1. In this way, the range of change due to attenuation caused by wavelength shift is smaller than the estimated increase or decrease amount. Here, α is the intensity ratio of the path remaining due to the wavelength shift.

[0044] Next, let us consider ALC (Automatic Level Control) operation with constant output intensity. In ALC operation, the optical amplifier path is linearly displayed, and the value obtained by dividing the optical amplifier output by the number of paths is used instead of the value before input to the optical amplifier. In addition, the intensity of each path passing through the optical amplifier, which increases or decreases, is divided by the optical amplifier output, and the value obtained by dividing the optical amplifier output by the increased or decreased number of paths is used instead of the value before input to the optical amplifier.

[0045] Specifically, the input optical power to the optical amplifier of the path that passes through the optical amplifier and inputs to the multiplexer and the input optical power to the multiplexer of the path that does not pass through the optical amplifier and inputs to the multiplexer are P, the optical amplifier j (j=1 to jmax) through which the path input to the multiplexer passes, the output optical power of the optical amplifier j is the ALC value j, and the number of input paths to the optical amplifier j is n0. ｊ , input path n0 to optical amplifier j ｊ The number of paths whose outputs are multiplexed by the multiplexer is n ｊ , the number of paths that do not pass through the optical amplifier is nx, and the number of input paths to one optical amplifier i (1≦i≦jmax) among the optical amplifiers j is n0′ ｉ From n0' ｉ The number of paths input from the optical amplifier i to the multiplexer is n ｉ From n' ｉ That is, by adding a path (either adding or deleting), the number of input paths to the multiplexer becomes nx + n ｉ +Σn ｊ (j≠i, 1≦j≦jmax) to nx+n' ｉ +Σn ｊ (j≠i, 1≦j≦jmax).

[0046] The number of paths of this optical amplifier i is n ｉ , n0 ｉ From n' ｉ , n0' ｉ When increasing or decreasing the number of paths, the determining unit 53 uses the difference between the following values ​​before and after the increase or decrease: Before increase or decrease: constant value P × number of paths not passing through an optical amplifier nx + ALC value i × n ｊ / n0 ｊ +ΣALC value j×n ｊ / n0 ｊ (j≠i, 1≦j≦jmax) After increase or decrease: constant value × number of paths not passing through an optical amplifier + ALC value i × n' ｊ / n0' ｊ +ΣALC value j×n ｊ / n0 ｊ (j≠i, 1≦j≦jmax) That is, the increase (or decrease) in the multiplexer output is the ALC value i×(n′ ｊ / n0' ｊ -n ｊ / n0 ｊ), and if the change is smaller than that, the determining unit 53 determines that there is a wavelength shift in one of the added paths (or one of the deleted paths).

[0047] For example, if one path with a wavelength shift is increased or decreased, the ALC value i×n ｉ / n0 ｉ is the ALC value i×n' ｉ / n0' ｉ = ALC value i × (n ｉ ±1) / (n0 ｉ ±1) and the ALC value i × ((n ｉ +α) / n'0 ｉ ) = ALC value i × (n ｉ +α) / (n0 ｉ +1) < ALC value i × (n ｉ +1) / (n0 ｉ +1) = ALC value i × ((n' ｉ ) / n0' ｉ ) and ALC value i × ((n ｉ −α) / n′0 ｉ ) = ALC value i × (n ｉ −α) / (n0 ｉ −1) > ALC value i × (n ｉ −1) / (n0 ｉ -1) = ALC value i × ((n' ｉ ) / n0' ｉ ), 0≦α<1. In this way, the range of change due to attenuation caused by wavelength shift is smaller than the estimated increase or decrease amount. Here, α is the intensity ratio of the path remaining due to the wavelength shift.

[0048] Also, only the numerator increases or decreases by α, while the denominator increases or decreases by 1. This is because the optical amplifier is placed before the input to the multiplexer, and so the output intensity of the optical amplifier is not attenuated when it is shared with the existing paths. This differs from the case where the signal intensity is detected from changes in the intensity of existing paths, such as the OSC signal output by the multiplexer, as described below. In this case, for example, when a wavelength-shifted path is added, the intensity of the wavelength-shifted path at the output of the multiplexer is attenuated from its original value, and the input to the optical amplifier after the multiplexer is reduced. Therefore, if the output of the optical amplifier is the ALC value, the number of paths before the addition is n, and the original input intensity of all paths is the same, the intensity of the OSC, etc., is not the ALC value / (n+1) estimated from the ALC value / (n), but is the ALC value / (n+α), which changes the denominator and becomes a value greater than the estimate.

[0049] If an optical amplifier is in ACC (Automatic Current Control) operation with a constant pumping intensity and a constant current value of the pumping light source, it is treated in the same way as AGC operation in the linear region where the gain is constant, and in the saturated region, the saturated output is treated as the ALC output and is treated in the same way as ALC operation. When ALC operation and AGC operation are mixed, it is desirable to convert them into a unified system, either linear or logarithmic, and make a judgment.

[0050] The optical amplifier through which the increasing or decreasing path passes may be determined from the post-multiplexing intensity, the total number of paths that can be determined from the number of changes in the increasing or decreasing direction of the post-multiplexing intensity, or the variation width of the post-multiplexing intensity. For example, if only AGC operation is performed, the determination may be made from the number of paths that can be operated by AGC or the new number of optical amplifiers for each sum of input intensities, or if only ALC operation is performed, the number of paths that provide an allowable intensity, the amount of change in optical intensity depending on the number of paths, etc.

[0051] In the example above, the paths to be wavelength-multiplexed are amplified by an optical amplifier before being wavelength-multiplexed by the multiplexer. In contrast to this example, we consider a case where the intensity due to wavelength shift after multiplexing is determined by the output of the optical amplifier from the wavelength-multiplexed signal output by the multiplexer. In this case, if the AGC operation or linear region is in operation, the value is measured by adding only the gain in a logarithmic display, or by multiplying only the gain in a linear display. If the ALC operation or saturated region is in operation, the output intensity is roughly constant, so the intensity change is measured by demultiplexing one of the signals that was multiplexed before the increase or decrease in the path. For example, if an OSC (Optical Supervisor Channel) signal for collective monitoring of wavelength-multiplexed signals between nodes is included in the wavelengths subject to ALC by the optical amplifier, it is suitable to demultiplex it and monitor its optical power. When one wavelength shift path is added to the number of multiplexer input paths n, the OSC intensity changes from the original 1 / n to 1 / (n+α), which is larger than the 1 / (n+1) when there is no wavelength shift, and when it is deleted, it becomes 1 / (n-α), which is smaller than the 1 / (n-1) when there is no wavelength shift. In this way, if the wavelength signals contained in the original to the changed wavelength multiplexed signal are extracted after the wavelength multiplexed signal is amplified by ALC, instead of the increment of the change in the wavelength multiplexed signal, the increase or decrease in the intensity change will be smaller than when there is no wavelength shift. The judgment unit 53 may make a judgment based on this change.

[0052] A setting receiver 51C may be added to the minimum configuration of the detector 50. In this case, the time change in the multiplexed value due to the increase or decrease may be compared with the appropriate additional intensity from the setting receiver, the change in the appropriate intensity, or the sum of the appropriate intensities of the individual paths being increased or decreased, or the multiplexed value may be compared with the appropriate intensity from the setting receiver or the sum of the appropriate intensities of the individual paths after the increase or decrease. Compared to a case where the setting receiver 51C is not provided, the intensity after multiplexing may vary for each path, and it is easier to determine which path passes through which optical amplifier. When the setting receiver 51C is not provided, the variation must be within a predetermined range, for example, the intensity change due to the allowable wavelength shift. In the case of multiple paths being used simultaneously, the variation among the multiple paths must be within the intensity change.

[0053] A pre-multiplexing receiver 51A or a pre-multiplexing detector 52A may be added to the minimum configuration of the detector 50. In this case, the post-multiplexing value is compared with the sum of the intensities of the multiplexed paths. The difference between the pre-multiplexing value and the post-multiplexing value for each path (loss if no optical amplifier is inserted; if an optical amplifier is inserted, a logarithmic display is used; in AGC operation, the value obtained by subtracting the gain from the loss; in ALC operation, the value obtained by dividing the ALC output by the number of conductive paths and then subtracting the loss from the optical amplifier output) can be used. Compared to a case where the pre-multiplexing receiver 51A or the pre-multiplexing detector 52A is not installed, changes in post-multiplexing intensity due to fluctuations in the pre-multiplexing intensity of existing paths can be detected, reducing erroneous determinations of wavelength shifts in the increased or decreased paths. By storing input intensities and values ​​for each path in advance, it is possible to accommodate cases where the loss for each path differs.

[0054] Also, both the pre-multiplex receiving unit 51A and the pre-multiplex detecting unit 52A may be provided, and either one may be selected depending on the path.

[0055] The system may include a setting receiver 51C and a pre-multiplexing receiver 51A or a pre-multiplexing detector 52A. In this case, the timing of adding or removing paths, the input intensity, loss, and gain of each path, the number of paths passing through the optical amplifier including the number of paths not passing through the optical amplifier or the target multiplexer, the operating mode, gain, ALC value, AGC value, and operating state in ACC operation of the optical amplifier can be used for judgment, and erroneous judgment due to input fluctuations of existing paths can be prevented.

[0056] (Basic Flow of Wavelength Shift Detection Method) Next, a basic flow of a wavelength shift detection method using the detector 50 will be described with reference to Fig. 4. In step S11, the wavelength of the additional path is set, and an additional signal is input to the WSS 72 using a predetermined terminal 83. The wavelength of the additional path can be set using the controller 91 or the like.

[0057] The detector 50 detects the wavelength shift based on the difference in the multiplexer output intensity before and after the signal is added. In other words, the detector 50 acquires the intensities of the output from the WSS 72 before and after the additional signals from the multiple terminals 83 are multiplexed, and detects the wavelength shift from the compatible wavelength of the added signal based on the difference in the acquired intensities.

[0058] In step S12, the detector 50 determines whether there is an increase in output according to the set path. Specifically, if the intensity of the wavelength-multiplexed signal output from the WSS 72 does not increase according to the intensity of the additionally input signal, the detector 50 detects this as a wavelength shift (step S14). On the other hand, if the intensity of the wavelength-multiplexed signal output from the WSS 72 increases according to the intensity of the additionally input signal, the detector 50 does not detect a wavelength shift (step S13).

[0059] (Flow for detecting wavelength shift by determining whether or not paths are increased or decreased using a predetermined method) Next, a method for detecting wavelength shift by determining whether or not paths are increased or decreased using a predetermined method will be described with reference to Fig. 5. In Fig. 5, the increase in intensity before and after an additional signal that has been initially connected or switched is multiplexed is detected, and if the increase does not correspond to the addition, it is detected that the wavelength is inappropriate. Here, the intensity is instructed to the light source, and the loss in the path is maintained or measured, and the loss (loss amount) may be input to the wavelength element as a subtracted value if the value is displayed logarithmically, or as a divided value if the value is displayed linearly.

[0060] Specifically, in step S21, the detector 50 uses either the receiving unit 51 or the detecting unit 52, or both, to acquire the intensity after the wavelength element (for example, the WSS 72).

[0061] In step S22, if there is an additional path passing through the wavelength element (step S22: Yes), the detector 50 acquires the intensity after the wavelength element using either or both of the receiving unit 51 and the detecting unit 52 (step S23). On the other hand, in step S22, if there is no additional path passing through the wavelength element (step S22: No), the detector 50 repeats the processes of steps S21 and S22.

[0062] In step S24, the detector 50 determines whether there is an increase in output in accordance with the set path. Specifically, if the intensity of the wavelength-multiplexed signal output from the WSS 72 does not increase in accordance with the intensity of the additionally input signal, the detector 50 detects this as a wavelength shift (step S26). On the other hand, if the intensity of the wavelength-multiplexed signal output from the WSS 72 increases in accordance with the intensity of the additionally input signal, the detector 50 does not detect a wavelength shift (step S25).

[0063] Alternatively, the number of paths may be reduced and an abnormality due to wavelength shift may be detected in the removed paths by determining whether the decrease in intensity is smaller than the decrease due to the removed paths. Alternatively, wavelength shift may be detected based on a change in intensity during measurement. In this case, steps S21 to S23 are integrated into a single process of determining whether there has been a change in intensity.

[0064] 6, the additional path intensity before the wavelength element may be detected, an estimated value of the total intensity after passing through the wavelength element according to the additional path intensity may be calculated, and wavelength shift may be detected based on the deviation from the estimated value. Specifically, in FIG. 6, only the intensity after multiplexing is measured, and the increase or decrease in the number of paths and the number of paths increased or decreased are estimated from the change in intensity, and wavelength shift is detected based on the deviation from the estimated value.

[0065] Specifically, in step S31, the detector 50 uses either the receiving unit 51 or the detecting unit 52, or both, to acquire the intensity after the wavelength element (for example, the WSS 72).

[0066] In step S32, if there is an additional path passing through the wavelength element (step S32: Yes), the detector 50 detects the additional path intensity before the wavelength element using either the receiving unit 51 or the detecting unit 52, or both, and calculates the corresponding post-element intensity (step S33). On the other hand, in step S32, if there is no additional path passing through the wavelength element (step S32: No), the detector 50 repeats the processes of steps S31 and S32. Note that in step S32, it is also possible to estimate whether there has been an increase or decrease in the number of paths and the number of paths that have been increased or decreased from the change in intensity only based on the intensity after multiplexing.

[0067] Thereafter, in step S34, the detector 50 detects (measures) the intensity after the wavelength element using either the receiving unit 51 or the detecting unit 52, or both.

[0068] In step S35, the detector 50 compares the actual measured value of the intensity after the wavelength element with the post-wavelength element intensity calculated from the additional path intensity before the wavelength element, and determines whether the actual measured value includes an intensity increment after the wavelength element corresponding to the intensity before the wavelength element of the additional path. If the detector 50 determines that the actual measured value includes an intensity increment after the wavelength element corresponding to the intensity before the wavelength element of the additional path (step S35: Yes), it does not detect a wavelength shift (step S36). On the other hand, if the detector 50 determines that the actual measured value does not include an intensity increment after the wavelength element corresponding to the intensity before the wavelength element of the additional path (step S35: No), it detects a wavelength shift (step S37).

[0069] (When using actual output measurement values ​​at the terminal) Next, a method for detecting wavelength shift using actual output measurement values ​​at the terminal 83 will be described with reference to FIG. 7. In this embodiment, output measurement values ​​after the WSS 72 and at the terminal 83 are used. Specifically, measurement points are indicated by black circles in the figure. D ｉ indicates the measurement point at the terminal 83, and D ＷＳＳ indicates the measurement point at WSS72. ｉ The subscript i indicates that the measurement point is the i-th terminal 83. However, the measuring device may be shared by tapping and monitoring after multiplexing, or by switching the tapped signal using an optical switch or the like and monitoring it.

[0070] The measuring device may be a detector 52 included in the detector 50. Specifically, the measuring device may be a detector 52 including a pre-multiplexing detector provided in the terminal 83 for measuring actual output values ​​at the terminal 83, and a post-multiplexing detector 52B of the detector 52 provided in the vicinity of the multiplexer, for example, in the APN-G 92. As long as measurements can be made, the detector 52 itself and the determination unit 53 may be located in the terminal 83, somewhere in an access area between the terminal 83 and an intra-office device, for example, the APN-G 92, an intra-office device, for example, inside or near the APN-G 92, or the controller 91. For example, either the pre-multiplexing or post-multiplexing measurement points, or each of the measurement points, may be located near the output of the measurement target, and the measurement values ​​may be collected via some kind of connection line, for example, access fiber.

[0071] The measuring device may be a measuring device that passes the pre-multiplexing intensity information itself or an actual output measurement value included in the pre-multiplexing intensity information to a transmitter (not shown) that transmits the pre-multiplexing intensity information to a receiving unit 51 included in the detector 50. As long as measurements are possible, the receiving unit 51 itself and the determining unit 53 may be located in the terminal 83, somewhere in an access area on the way from the terminal 83 to an intra-office device, for example, an APN-G 92, in an intra-office device, for example, inside or near the APN-G 92, or in the controller 91. For example, either the pre-multiplexing or post-multiplexing signal, or each receiving point, may be located near the output to be measured, and the measured value may be collected via some kind of connection line, for example, an access fiber, or may be located near the determining unit 53.

[0072] In the latter case, the measurement value at the terminal 83 may be acquired by receiving the value measured at the terminal 83 at the receiver 51 of the detector 50 in FIG. 3 in response to an inquiry from the APN-G 92 or the controller 91, or as performance monitor information, a TCA (Threshold Crossing Alert, or a Threshold Crossing Alarm), an alarm, or a stream thereof, which is issued from the terminal 83 to the APN-G 92 or the controller 91, or the like. That is, pre-multiplexing intensity information received by the pre-multiplexing receiver 51A of the receiver 51 constituting the detector 50 in FIG. 3 is used.

[0073] Here, the measuring instrument is a measuring instrument that measures the output of the light source of the terminal 83, and the output corrected for losses and gains from the light source, such as a modulator, to the terminal output may be corrected when transmitted from the terminal 83, or may be corrected on the receiving side. The measuring instrument may be a measuring instrument that measures the optical output of the terminal 83 by splitting a signal within the terminal 83, or a measuring instrument that measures the optical output of the terminal 83 by splitting a signal outside the terminal 83. When measuring the optical output outside the terminal 83, the input from the terminal 83 to the network, for example, the input intensity to the access fiber, may be measured, and the measurement may be performed at a measurement point where the signal passes through as is, excluding losses due to splitting during measurement, or may be performed by a device that multiplexes and splits the signal light in a device on the customer side, such as an APN-S, beyond the APN-G92. In this case, the terminal output varies depending on the losses and gains up to those devices, but the value may be corrected for these losses and gains. The correction only needs to determine the loss or gain that would be incurred if the wavelength were correct, and the excess loss or gain that would be incurred if the wavelength were incorrect, up to the measurement point after output from a multiplexer or multiplexer / demultiplexer that multiplexes the signal light.

[0074] Similarly, a terminator (not shown) may be provided located in front of the transmission path that receives the output of terminal 83 and forwards it toward APN-G92, and if measurements are to be taken there, that terminator may be provided, or a repeater may be provided that relays the signal to the transmission path, and if measurements are to be taken there, that repeater may be provided, or the entrance may be provided when measurements are taken at the entrance of APN-G92, or an optical switch such as a fiber cross connect (FXC) or wavelength cross connect (WXC) that is located closer to terminal 83 than the multiplexer or multiplexer / demultiplexer that multiplexes the main signal light into a wavelength-multiplexed signal inside APN-G92, or before or after that, and the measured values ​​may be received and acquired by the receiver 51 of the detector 50 in Figure 3 as a stream of inquiry responses, performance monitor information, TCAs, alarms, or the like. Instead of the detector receiving and acquiring the signal using the receiving unit 51, the pre-multiplexing detection unit 52A of the detection unit 52 may detect the signal at a functional unit or location located closer to the terminal 83 than the terminal 83, terminator, repeater, entrance to APN-G92, or multiplexer or multiplexer / demultiplexer that multiplexes the main signal inside APN-G92.

[0075] Whether to use the detector unit 52 or the receiver unit 51 of the detector 50 depends on the location of the detector 50, whether it receives intensity information or detects intensity using the detector unit 52. If, due to the network configuration, the terminal 83 is located away from the APN-G92 and the detector 50 is located within the APN-G92, the output of the terminal 83 is often received as pre-multiplexing intensity information by the pre-multiplexing receiver unit 51A of the receiver unit 51 of the detector 50. If only pre-multiplexing intensity information and post-multiplexing intensity information are received, the detector unit 52 may not be provided. If only pre-multiplexing intensity information is received and post-multiplexing intensity is detected, the post-multiplexing receiver unit 51B of the receiver unit 51 and the pre-multiplexing detector unit 52A of the detector unit 52 may not be provided. If only pre-multiplexing intensity information is detected and post-multiplexing intensity information is received, the pre-multiplexing receiver unit 51A of the receiver unit 51 and the post-multiplexing detector unit 52B of the detector unit 52 may not be provided. When only the pre-multiplexing intensity and the post-multiplexing intensity are detected, the receiving unit 51 does not need to be provided.

[0076] Alternatively, multiple values ​​may be used and statistical processing may be performed to obtain the results based on the differences in loss and gain at each measurement point. For example, suppose there are measurement points A, B, and C, in order, between the terminal 83 and the multiplexer or multiplexer / demultiplexer that multiplexes the main signal, and there is loss from measurement point A to B and gain from measurement point B to C. When statistically processing these three values, for example, the value at measurement point C may be matched, and the value at measurement point A may be subjected to simple averaging or weighted averaging, with the loss up to B subtracted from the value at measurement point A and the gain up to C added, the value at measurement point B may be added to the value at measurement point B, and the value at measurement point C may be left unchanged. The weighting, such as for weighted averaging, may be increased if the reliability is high and decreased if the reliability is low, depending on the reliability of the values ​​at each measurement point. The loss and gain from that measurement point to the multiplexer or demultiplexer may be adjusted by aligning the values ​​at each measurement point. To address erroneous measurements, damage to the measurement function, or damage to information between transmission and reception, outliers may be eliminated by majority vote or other means, and only other information or intensity may be used. The intensity after multiplexing can also be detected by the post-multiplexing detection unit 52B of the detection unit 52, or the post-multiplexing intensity information can be received by the post-multiplexing receiving unit 51B of the receiving unit 51, and the same applies to statistical processing of multiple intensities and information.

[0077] For example, when applied to an OpenROADM MSA, the detection unit 52 may be provided in an Xponder (transponder / muxponder / switchponder) or remote transponder, which is the terminal itself corresponding to the terminal 83, or in a pluggable transceiver or pluggable optical system that outputs signal light in the terminal 83, etc.

[0078] When receiving at the receiving unit 51, the set value may be used as long as the output matches the set value. For example, the target-transmit-power value of the OTSi (Optical Tributary Signal) or Och (Optical Channel) set by Edit-config may be received from the terminal 83 or a controller that controls the transceiver. When actually measuring, the opticalPowerOutput value obtained by Get-config may be received from the terminal 83 or a controller that controls the transceiver, or the performance monitor value or performance monitor streaming may be received directly.

[0079] If the APN-G92 is represented by an SRG (Shared Risk Group) or a Degree (DEG), the add / drop port of the SRG is the inlet of the APN-G92, and the actual measured value at the inlet of the APN-G92 is received, the measured value at the OTSi on the SRG port may be used or received. Instead of the value of OSTi, the value at the network media channel (NMC) where the OSTi is located, the value at the SRG port where the NMC is located, the value at the MC, the value at the OMS where the MC is located, the value at the OTS where the OMS is located, or the value at the DEG port where the OTS is located may be used. For example, the value at the nmc (Network Media Channel)-ctp (Connection Termination Point) interface of the SRG port pair may be obtained. If the actual measured value is received within the APN-G92, the value of the mc (Media Channel)-ctp interface of the DEG's TTP (trail termination point) received by the DEG from the SFG may be used. Here, one or more NMCs are set to the MC, and the NMC-CTP is set to the SRG or DEG, with one set to the SRG port. In the DEG, multiple NMC-CTPs can be set to one MC-TTP, the MC-TTP to the OMS, the OMS to the OTS, and the OTS to the DEG port. The value may be obtained using the target set value and the opticalPowerOutputDrift, which is the deviation from that value.

[0080] In the case of the ONF (Open Networking Foundation) Transport API (TAPI), the setting values ​​are those set by PUT or acquired by GET, and the measurement values ​​are those acquired by GET. The measurement values ​​are obtained at the CEP (connection-end-point) of the OTSiMC, MC, OMS, and OTS_MEDIA layers. For example, it can be obtained from the power measurement pac of the mc-connection-end-point-spec of the MC CEP, the oms-connection-end-point-spec of the OMS CEP, or the ots-media-connection-end-point-spec of the OTS_MEDIA CEP. For example, it is measured-output-power, which is the output power measured by the CEP in the terminal 83, measured-output-power, or measured-input-power, which is the input power, measured by the APN-G. Here, both OMS and OTS are OMS / OTS Optical signal maintenance entities and are positioned in the Media layer. OMS (Optical Multiplexing Section) corresponds to a link between node equipments and is a section where wavelength-multiplexed signals are transmitted without adding or dropping, and OTS (Optical Transmission Section) corresponds to a link between node equipments and is a section where wavelength-multiplexed signals are transmitted without adding or dropping.

[0081] In the case of the Optical Internetworking Forum (OIF) Common Management Interface Specification (CMIS), the measurement is performed by the pluggable module, and the measurement function of the pluggable module is made part of the detection unit. The measurement value may be obtained via a low-rate two-wire serial interface used for communication between the host and the pluggable module, such as TWI (Two Wire Interface) or I2C (Inter-Integrated Circuit), or the value may be obtained and the information received by the receiving unit may be transmitted. For example, the value may be the Tx output optical power performed for the receiving lane in real-time lane monitoring.

[0082] In the case of OpenConfig, the terminal output is the output-power under / components / component / transceiver / state / , which is the output optical power of the entire transceiver at terminal 83, i.e., the total of the physical channels equipped by the transceiver, or the output-power under / components / component / optical-channel / state / , or the output-power under / components / component / transceiver / physical-channels / channel / state / , which is the output optical power of the corresponding physical channel. If observing at the entrance of ANP-G92, it is sufficient to use input-power under / components / component / optical-channel / state / , which is the total input optical power from the entire transceiver of the terminal, i.e., the physical channels equipped in the transceiver.

[0083] Although examples of several standards have been given above, the present invention is not limited to these examples. Furthermore, optical power (intensity) detection and reception similar to this example may be applied to other embodiments of the present application.

[0084] Specifically, the detector 50 estimates the total intensity after the WSS 72 according to the output intensity of the signal to be added or the input intensity to the WSS 72, and detects the wavelength shift based on the estimated value and the actual measurement value. For example, the detector 50 acquires the added signal intensity before the WSS 72, calculates an estimate of the total intensity of the added signal after the WSS 72 according to the added signal intensity before the WSS 72 and one or more signals input to the WSS 72 before the addition, and detects the wavelength shift from the compatible wavelength of the added signal based on the estimate and the actual measurement value of the output intensity of the WSS 72. Here, a WSS is exemplified as the multiplexer, but other multiplexers or multiplexer / demultiplexers, such as an AWG, may also be used. This also applies to other embodiments of the present application.

[0085] In this example, the output intensity I_T ｉ Measurement and notification at the terminal 83, loss L from each terminal 83 to the WSS 72 output ｉ (=L_M ｉ +L_A ｉ ) is known. This is because the optical power at the terminal output changes at the input to the multiplexer (WSS72 in the figure) due to the loss and gain of the access fiber, the intra-office equipment, for example, the optical switch (FXC in the figure) of the APN-G92. Therefore, it is sufficient to subtract the amount of optical power decrease due to loss from the terminal output to the multiplexer input, and add the amount of optical power increase due to gain. An example is shown below. If the loss from the APN-G92 input to WSS72 is L_M ｉ and the loss from the terminal 83 to the APN-G 92 is L_A ｉ Let's say.

[0086] When it is assumed that a wavelength multiplexed signal is added from terminal i0 83, the intensity Imux after multiplexing is originally Σ(I_T ｉ -L ｉ ) is assumed. Therefore, |Σ(I_T ｉ -L ｉ )-Imux|>δ, that is, if the absolute value of the difference between the estimated value and the measured value exceeds δ, it is detected that the wavelength of the additional terminal 83 is shifted. ｉ is the output intensity measured by the i-th terminal 83, L ｉis the loss from each terminal 83 to the WSS 72 output, δ is the allowable error, Σ is the sum from the first terminal 83 to the i-th terminal 83, and | | is an operation that takes the absolute value. The reason for determining using the absolute value is that the post-multiplexing intensity due to the addition or deletion of a wavelength-shifted path will be smaller than the expected intensity.

[0087] Loss L ｉ is different for each wavelength λk, and its value is L ｉｋ Then, the formula that gives the difference between the estimated and measured values ​​of the intensity after multiplexing is as follows: |Σ(I_T-L ｉｋ ) -Imux |>δ

[0088] Furthermore, if there is a terminal with a wavelength shift among the existing terminals 83 before the addition, the determination may be made based on the difference between the intensity Imux after the addition and the intensity Imux after the addition. In this case, the determination may be made based on the following formula. ｉｋ In some cases, L ｉ It is. | I_T ｉ -L ｉｋ −((Imux_after addition)−(Imux_before addition))|>δ In other words, if the absolute value of the difference between the estimated increment and the actually measured increment exceeds δ, it may be detected that the wavelength of the additional terminal 83 is shifted.

[0089] As a method for satisfying the premise of actually measuring the output intensity at the terminal 83, the controller 91 acquires the output value at the terminal 83. ｉThe loss may be measured using a measuring device such as an OTDR. In this case, the measuring device such as an OTDR is provided in the APN-G92. The loss may also be measured using a light source and intensity meter. In this case, a light source is provided in one of the terminal 83 and the APN-G92, and a measuring device in the other. If there is no difference in loss between the direction from terminal 83 to APN-G92 and the direction from APN-G92 to terminal 83, either side may be provided with a measuring device. If there is directionality, for example, if the loss in the section from terminal 83 to APN-G92 is high, the differential loss may be added to the loss in the direction from APN-G92 to terminal 83. The light source and measuring device may be provided on one side, and the light from the other side may be folded back as is. In this case, the folded loss is subtracted from the measured value and the result is divided by 2. If there is a difference in loss depending on the direction, for example, if the loss in the section from terminal 83 to APN-G92 is high, the folded loss and the difference are subtracted from the measured value, divided by 2, and the difference is added.

[0090] When a light source or measuring instrument is shared for measurement, the loss difference between the shared terminals 83 is corrected. For example, if the loss of terminal i 83 is Δi greater than the loss of the OTDR, Δi is added to the OTDR measurement value. When a light source or measuring instrument is permanently installed in the APN-G92 for measurement, as shown in the figure below, it may be provided on the terminal side of the APN-G92 to which the terminal 83 is connected, or it may be shared by multiple terminals 83 via an optical switch or the like (not shown). Sharing may be performed by the FXC 71, and it may be provided on the port opposite the terminal 83. If there is a difference between the loss at the wavelength of the optical signal used for measurement and the loss at the wavelength assigned to the terminal 83, the difference is corrected. The loss may be calculated by multiplying the transmission path length between the terminal 83 and the APN-G92 by the loss at the assigned wavelength per transmission path distance.

[0091] (Using Measured Input Values ​​at APN-G) Next, a method for detecting wavelength shifts using measured input values ​​at APN-G92 will be described with reference to FIG. 8 . In this embodiment, measured input values ​​between the APN-G92 inlet and the WSS72 are used. Specifically, the settable range of the input monitor is indicated by an arrow in the figure. However, after multiplexing, the measuring instrument can be shared by tapping and monitoring, or by switching the tapped signal using an optical switch or the like for monitoring. The inlet may be connected to a measuring instrument for measurement before input to the FXC71 or before multiplexing at the WSS72, or may be tapped and monitored, or the tapped signal may be switched using an optical switch or the like to share the measuring instrument. As described above, the measuring instrument may be the detector 52 included in the detector 50. The measuring instrument may be the pre-multiplexing detector 52A included in the detector 52. The measuring instrument may pass information to a transmitter that transmits it to a receiver 51 included in the detector 50. The measuring device may pass information to a transmitting unit that transmits the information to a pre-multiplexing receiving unit 51A included in the receiving unit 51.

[0092] Specifically, detector 50 estimates the strength after WSS 72 according to the strength of the signal added to the device upstream of WSS 72, and detects the wavelength shift based on the estimated value and the actual measurement value. For example, detector 50 acquires the strength of the additional signals input from, for example, multiple terminals 83 to APN-G 92, to which signals are input upstream of WSS 72, calculates an estimate of the total strength of one or more signals input to WSS 72 before the addition of the signal added after WSS 72 according to the strength of the additional signal input to APN-G 92, and detects the wavelength shift from the compatible wavelength of the added signal based on the estimate and the actual measurement value of the strength of the output of WSS 72.

[0093] In this example, the measurement of the input intensity to the APN-G92 is assumed. ｉ , a wavelength multiplexed signal from the i-th terminal 83, ｋ Assuming addition, the intensity Imux after multiplexing is originally ΣI ｉ -L_M×i. Therefore, |I ｉ If -L_M×i-Imux|>δ, that is, if the absolute value of the difference between the estimated value and the actual measured value exceeds δ, it is detected that the wavelength of the additional terminal 83 is shifted.ｉ is the measured input strength from the i-th terminal 83, L_M is the loss from the APN-G 92 input to the WSS 72 output, δ is the allowable error, and Σ is the sum from the 1st terminal 83 to the i-th terminal 83.

[0094] If the loss from APN-G92 input to WSS72 output differs for each terminal, use that value as L_M ｉ The decision formula is as follows: |Σ(I ｉ -L_M ｉ ) -Imux |>δ

[0095] Furthermore, the wavelength λ ｋ The value is different for each L_M ｉｋ Then, we get the following: |Σ(I ｉ -L_M ｉｋ ) -Imux |>δ

[0096] Furthermore, if there is a terminal with a wavelength shift among the existing terminals 83 before the addition, the difference between the multiplexed intensity Imux before and after the addition may be used for the determination. In this case, the determination may be made using the following formula: L_M ｉｋ In some cases L_M ｉ and L_M. |I ｉ -L_M ｉｋ −((Imux_after addition)−(Imux_before addition))|>δ In other words, if the absolute value of the difference between the estimated increment and the actually measured increment exceeds δ, it may be detected that the wavelength of the additional terminal 83 is shifted.

[0097] Here, the loss from the APN-G92 input to the WSS72 output is L_M ｉ YA L_M ｉｋ The loss is measured before the APN-G 92 is put into operation or before a line is set up in the wavelength-multiplexing WSS 72. Alternatively, the loss may be measured using light of a wavelength that does not affect the main signal multiplexed in the WSS 72, and the loss difference due to wavelength may be corrected.

[0098] Although the input values ​​to APN-G92 are measured at the entrance of APN-G92, they may be measured anywhere from the entrance to WSS72 instead of at the entrance of APN-G92. ｉ , L_M ｋThe value of L_M is the loss from the measurement point. Conversely, it may be measured anywhere from the demarcation point at the entrance of the terminal 83 or the terminating device to the entrance of the APN-G 92. In this case too, L_M, L_M ｉ , L_M ｋ The value of L_M is the loss from the measurement point. ｉ Is L ｉ To L_M ｋ Is L ｉｋ approaching.

[0099] (Using the Current Value of the Optical Amplifier at the Output Destination of the WSS) Next, a method for detecting wavelength shift using a control value, for example, a current value, of the optical amplifier 73 at the output destination of the WSS 72 will be described with reference to Fig. 9. In this embodiment, instead of measuring the intensity of the WSS 72 output, a control value, for example, a current value (shown by the black circle C in the figure) of the optical amplifier 73 at the output destination of the WSS 72 is measured. Ａ (measured value at 1000 kJ / s) is used.

[0100] The control value may be detected (measured) by a detector 52 included in the detector 50. The receiver 51 included in the detector 50 may receive post-multiplexing intensity information measured by an optical amplifier 73 or the like, or the post-multiplexing receiver 51B of the receiver 51 may receive the control value. The detected (measured) or received control value may be used, for example, as follows.

[0101] The control of the optical amplifier used in this embodiment includes, for example, control to keep the gain constant regardless of addition or deletion of input light or increase or decrease in input signal strength, or control to keep the total output strength constant (constant output strength).

[0102] To keep the gain constant, it is necessary to increase the pumping power in accordance with the increase in input signal strength due to the addition of input light. In the case of current pumping, the applied current is increased. In the case of optical pumping, the pumping light intensity is increased. To increase the pumping light intensity, for example, the applied current of the pumping light source is increased.

[0103] To maintain a constant output light intensity, it is necessary to reduce the pumping power in accordance with an increase in the input signal intensity. In the case of current pumping, the applied current is reduced. In the case of optical pumping, the pumping light intensity is reduced. To reduce the pumping light intensity, for example, the applied current to the pumping light source is reduced. When adjusting the input or output attenuation of the optical amplifier, attenuation is performed in accordance with the increase.

[0104] In either case, in the case of wavelength misalignment, the multiplexer or multiplexer / demultiplexer attenuates more than in the case of an appropriate wavelength, and the added input intensity becomes smaller, so the multiplexer control value becomes smaller than estimated. In other words, if the gain is constant, the increase in pump light intensity and the increase in applied current to the pump light source will be smaller than estimated, and the added input intensity can be estimated from these values. If the output intensity is constant, the decrease in pump light intensity, the decrease in applied current to the pump light source, and the increase in attenuation will be smaller than estimated, and the added input intensity can be estimated from these values.

[0105] In addition, when controlling an optical amplifier to keep the pumping light intensity constant or the current of the pumping light source constant, the control does not change according to the input light intensity.

[0106] The following describes an example of the control value, using a current value. Specifically, the detector 50 estimates a control value for excitation of the optical amplifier 73 output from the WSS 72 according to the strength of the additional signal before the WSS 72, and detects the wavelength shift based on the estimated value and the actual measured value.

[0107] When the input light to the optical amplifier 73 changes from (actual measurement value Imux_before addition) to (actual measurement value Imux_after addition), the gain changes to (actual measurement value Imux_after addition) / (actual measurement value Imux_before addition).

[0108] If the optical amplifier 73 is operating in a constant-gain AGC mode, the pump light intensity is increased to maintain a constant gain. If a current-driven pump light source such as an LD is used to pump the optical amplifier 73, the applied current is increased. If the change in the amount of current corresponding to the original applied current is an increase in accordance with the ratio of (actually measured value Imux_before addition) / (actually measured value Imux_after addition), it is determined that there is no wavelength shift. If the increase is smaller than the allowable error, it is determined that there is a wavelength shift.

[0109] If the optical amplifier 73 is operating in an ALC mode with a constant output intensity, the pumping light intensity is reduced to maintain a constant output. If a current-driven pumping light source such as an LD is used to pump the optical amplifier 73, the applied current value is reduced. If the change in the amount of current corresponding to the original applied current amount is reduced by an amount corresponding to the ratio of (actual measurement value Imux_before addition) / (actual measurement value Imux_after addition), it is determined that there is no wavelength shift. If the amount of reduction is smaller than the allowable error, it is determined that there is a wavelength shift.

[0110] In this example, instead of monitoring the multiplexer output intensity, the current value of the optical amplifier 73 is used, and therefore the optical amplifier 73 is used instead of an intensity measuring device that monitors the multiplexer output intensity. Therefore, in an example where the actual input measurement value at APN-G92 is used, there is no multiplexer output as shown in the figure. The same applies to other examples, such as when the input to APN-G92 is aligned in advance, when the output of terminal 83 is aligned in advance, when the actual output measurement value at terminal 83 is used, and when the input to the multiplexer is aligned in advance.

[0111] (When Intensity After WSS Is Measuring) Next, a method for detecting a wavelength shift while measuring the intensity after the WSS 72 will be described with reference to FIG.

[0112] Specifically, detector 50 keeps constant the intensities of multiple signals input to WSS 72, either at their output or at the input to APN-G 92 preceding WSS 72 or to WSS 72, estimates the output intensity from WSS 72, and detects wavelength shift based on the estimated value and the actual measured value. In other words, detector 50 estimates the output intensity from WSS 72 by keeping constant the output intensity of signals from multiple terminals 83, the input intensity of signals input from multiple terminals 83 to APN-G 92 including WSS 72, or the input intensity of signals input to WSS 72, and detects wavelength shift from the compatible wavelength based on the estimated output intensity and the actually measured output intensity from WSS 72.

[0113] First, a case where the outputs of the terminals 83 are aligned in advance will be described. In this example, the intensity after the WSS 72 is monitored. However, the measuring device may be shared by tapping and monitoring, or by switching the tapped signal using an optical switch or the like. As described above, the measuring device may be the detection unit 52 included in the detector 50. The measuring device may also be the pre-multiplexing detection unit 52A included in the detection unit 52. The measuring device may pass information to a transmission unit that transmits it to the receiving unit 51 included in the detector 50. The measuring device may pass information to a transmission unit that transmits it to the pre-multiplexing receiving unit 51A included in the receiving unit 51. If the measuring device is not the detection unit 52 included in the detector 50, the receiving unit 51 included in the detector 50 may receive the information from the measuring device directly or indirectly from the measuring device.

[0114] In this example, the output strength from all terminals 83 is made uniform, and the loss L ｉ (=L_M ｉ +L_A ｉ ) is known. If it is assumed that a wavelength multiplexed signal is added from the i-th terminal 83, the intensity Imux after multiplexing is originally Σ(I_T-L ｉ ) or I_T×i−ΣL ｉ Therefore, |I_T×i-ΣL ｉ -Imux |>δ or |Σ(I_T-L ｉ )-Imux|>δ, it is detected that the wavelength of the additional terminal 83 is shifted. In other words, if the absolute value of the difference between the estimated value and the actual measured value exceeds δ, it is detected that the wavelength of the additional terminal 83 is shifted. Here, I_T is the output intensity of the aligned terminal 83, L ｉ is the loss from each terminal 83 to the output of the WSS 72, δ is the allowable error, and Σ is the sum from the first terminal 83 to the i-th terminal 83.

[0115] The loss Li differs for each wavelength λk, and its value is L ｉｋ Then, it becomes as follows: |I_T×i-ΣL ｉｋ -Imux |>δ or |Σ(I_T-L ｉｋ ) -Imux |>δ

[0116] Furthermore, if there is a terminal with a wavelength shift among the existing terminals 83 before the addition, the determination may be made based on the difference between the intensity Imux after the addition and the intensity Imux after the addition. In this case, the determination may be made based on the following formula. ｉｋ In some cases, L ｉ |I_T-L ｉｋ −((Imux_after addition)−(Imux_before addition))|>δ In other words, if the absolute value of the difference between the estimated increment and the actually measured increment exceeds δ, it may be detected that the wavelength of the additional terminal 83 is shifted.

[0117] As a method for satisfying the premise of making the output intensity from all terminals 83 uniform, any of the following methods can be considered: 1. The output of terminal 83 is determined in advance, and terminal 83 outputs at the predetermined intensity. 2. The controller 91 remotely controls terminal 83 to instruct it to output at a predetermined intensity, and the controlled terminal 83 outputs at the predetermined intensity. 3. The controller 91 acquires the output value from terminal 83 and adjusts and controls the output so that it is at the predetermined intensity.

[0118] Loss L_A from terminal 83 to APN-G 92 ｉ The loss may be measured using a measuring device such as an OTDR. In this case, the measuring device such as an OTDR is provided in the APN-G92. The loss may also be measured using a light source and intensity meter. In this case, the light source is provided in one of the terminal 83 and the APN-G92, and the measuring device is provided in the other. If there is no difference in loss between the direction from terminal 83 to APN-G92 and the direction from APN-G92 to terminal 83, either side may be provided with the measuring device. If there is directionality, for example, if the loss in the section from terminal 83 to APN-G92 is high, the differential loss may be added to the loss in the direction from APN-G92 to terminal 83. The light source and measuring device may be provided on one side, and the light from the other side may be folded back as is. In this case, the folded loss is subtracted from the measured value and the result is divided by 2. If there is a difference in loss depending on the direction, for example, if the loss in the section from terminal 83 to APN-G92 is high, the folded loss and the difference are subtracted from the measured value, divided by 2, and the difference is added.

[0119] When a light source or measuring instrument is shared for measurement, the loss difference between the shared terminals 83 is corrected. For example, if the loss of terminal i 83 is Δi greater than the loss of the OTDR, Δi is added to the OTDR measurement value. When a light source or measuring instrument is permanently installed in the APN-G92 for measurement, as shown in the figure below, it may be provided on the terminal side of the APN-G92 to which the terminal 83 is connected, or it may be shared by multiple terminals 83 via an optical switch or the like (not shown). Sharing may be performed by the FXC 71, and it may be provided on the port opposite the terminal 83. If there is a difference between the loss at the wavelength of the optical signal used for measurement and the loss at the wavelength assigned to the terminal 83, the difference is corrected. The loss may be calculated by multiplying the transmission path length between the terminal 83 and the APN-G92 by the loss at the assigned wavelength per transmission path distance.

[0120] Next, a case where the input to the APN-G92 is aligned in advance will be described. In this example, the intensity after the WSS72 is also monitored. However, the measuring instrument may be shared by tapping and monitoring, or by switching the tapped signal using an optical switch or the like. As described above, the measuring instrument may be the detector 52 included in the detector 50. The measuring instrument may also be the pre-multiplexing detector 52A included in the detector 52. The measuring instrument may pass information to a transmitter that transmits it to a receiver 51 included in the detector 50. The measuring instrument may pass information to a transmitter that transmits it to a pre-multiplexing receiver 51A included in the receiver 51. If the measuring instrument is not the detector 52 included in the detector 50, the receiver 51 included in the detector 50 may receive the information from the measuring instrument directly or indirectly from the measuring instrument.

[0121] In this example, it is assumed that the input intensities of all terminals 83 to the APN-G 92 are the same. ｋ Assuming addition, the post-multiplexing intensity Imux is essentially (I-L_M) x i. Therefore, if |(I-L_M) x i-Imux| > δ, the wavelength of the added terminal is detected as being misaligned. In other words, if the absolute value of the difference between the expected value and the actual measured value exceeds δ, the wavelength of the added terminal is detected as being misaligned. Here, I is the aligned output intensity, L_M is the loss from the APN-G92 input to the WSS72 output, δ is the allowable error, and Σ is the sum from terminal 1 83 to terminal i 83.

[0122] If the loss from the APN-G92 input to the output at the WSS72 differs for each terminal 83, the value is set as L_M ｉ The judgment formula is as follows: |(I×i-ΣL_M ｉ )-Imux|>δ, or |Σ(IL_M ｉ ) -Imux |>δ

[0123] Furthermore, the wavelength λ ｋ The value is different for each L_M ｉｋ Then, we get the following: |(I×i-ΣL_M ｉｋ )-Imux|>δ, or |Σ(IL_M ｉｋ ) -Imux |>δ

[0124] Furthermore, if there is a terminal with a wavelength shift among the existing terminals 83 before the addition, the difference between the multiplexed intensity Imux before and after the addition may be used for the determination. In this case, the determination may be made using the following formula: L_M ｉｋ In some cases L_M ｉ or L_M. |I-L_M ｉｋ −((Imux_after addition)−(Imux_before addition))|>δ In other words, if the absolute value of the difference between the estimated increment and the actually measured increment exceeds δ, it may be detected that the wavelength of the additional terminal 83 is shifted.

[0125] Here, the loss from the APN-G92 input to the WSS72 output is L_M ｉ YA L_M ｉｋ The loss is measured before the APN-G92 is put into operation or before a line is set up in the wavelength-multiplexing WSS 72. Alternatively, the loss may be measured using light of a wavelength that does not affect the main signal multiplexed in the WSS 72, and the loss difference due to wavelength may be corrected.

[0126] As a method for satisfying the premise that the input strength to APN-G92 of all terminals 83 is uniform, any of the following methods can be considered: 1. The loss between terminal 83 and APN-G92 is measured in advance, and the input strength to APN-G92 as a result of the loss is output as a predetermined value, the value I mentioned above. For example, if the loss between terminal 83 and APN-G92 of terminal i is L_A ｉ Then, I + L_A ｉ2. An optical intensity meter may be placed on the APN-G 92 side, and the terminal 83 may be instructed to adjust the measured intensity from the terminal 83 to a predetermined value. This is similar to the case described below.

[0127] Loss L_A from terminal 83 to APN-G 92 ｉ The loss may be measured using a measuring device such as an OTDR. In this case, the measuring device such as an OTDR is provided in the APN-G92. The loss may also be measured using a light source and intensity meter. In this case, the light source is provided in one of the terminal 83 and the APN-G92, and the measuring device is provided in the other. If there is no difference in loss between the direction from terminal 83 to APN-G92 and the direction from APN-G92 to terminal 83, either side may be provided with the measuring device. If there is directionality, for example, if the loss in the section from terminal 83 to APN-G92 is high, the differential loss may be added to the loss in the direction from APN-G92 to terminal 83. The light source and measuring device may be provided on one side, and the light from the other side may be folded back as is. In this case, the folded loss is subtracted from the measured value and the result is divided by 2. If there is a difference in loss depending on the direction, for example, if the loss in the section from terminal 83 to APN-G92 is high, the folded loss and the difference are subtracted from the measured value, divided by 2, and the difference is added.

[0128] When a light source or measuring instrument is shared for measurement, the loss difference between the shared terminals 83 is corrected. For example, if the loss of terminal i is Δi greater than the loss of the OTDR, Δi is added to the OTDR measurement value. When a light source or measuring instrument is permanently installed in the APN-G92 for measurement, as shown in the figure below, it may be provided on the terminal side of the APN-G92 to which the terminal 83 is connected, or it may be shared by multiple terminals via an optical switch or the like (not shown). Sharing may be performed by the FXC 71, and it may be provided on the port opposite the terminal 83. If there is a difference between the loss at the wavelength of the optical signal used for measurement and the loss at the wavelength assigned to the terminal 83, the difference is corrected. The loss may be calculated by multiplying the transmission path length between the terminal 83 and the APN-G92 by the loss at the assigned wavelength per transmission path distance.

[0129] Next, a case where the input to the WSS 72 is aligned in advance will be described. Next, a case where the input to the APN-G 92 is aligned in advance will be described. In this example, the intensity after the WSS 72 is monitored. However, the measuring device may be shared by tapping and monitoring, or by switching the tapped signal using an optical switch or the like and monitoring it. As described above, the measuring device may be the detection unit 52 included in the detector 50. If the measuring device is not the detection unit 52 included in the detector 50, the information of the measuring device may be received directly or indirectly from the measuring device by the receiving unit 51 included in the detector 50.

[0130] In this example, it is assumed that the input intensities to the WSS 72 (multiplexer) of the terminals are uniform. ｋ Assuming addition, the post-multiplexing intensity Imux is essentially (IB-L_B) x i. Therefore, if |(IB-L_B) x i-Imux| > δ, it is detected that the wavelength of the added terminal is misaligned. In other words, if the absolute value of the difference between the expected value and the actual measured value exceeds δ, it is detected that the wavelength of the added terminal 83 is misaligned. Here, IB is the input intensity to the combined multiplexer, L_B is the loss from the multiplexer input to the multiplexer output, δ is the allowable error, and Σ is the sum from terminal 1 83 to terminal i 83.

[0131] If the loss from the multiplexer input to the multiplexer output differs for each terminal 83, the value is expressed as L_B ｉ The judgment formula is as follows: |(IB×i-ΣL_B ｉ )-Imux|>δ, or |Σ(IB-L_B ｉ ) -Imux |>δ

[0132] Furthermore, the wavelength λ ｋ The value is different for each L_B ｉｋ Then, it becomes as follows. |(I×i-ΣL_MB ｉｋ )-Imux|>δ, or |Σ(IL_B ｉｋ ) -Imux |>δ

[0133] Furthermore, if there is a terminal with a wavelength shift in the existing terminal before the addition, the determination may be made based on the difference between the intensity Imux after the addition and before the addition. In this case, the determination may be made using the following formula: L_B ｉｋ In some cases, L_Bｉ or L_B. |IB-L_Bik-((Imux_after addition)-(Imux_before addition))|>δ In other words, if the absolute value of the difference between the estimated increment and the actually measured increment exceeds δ, it may be detected that the wavelength of the additional terminal 83 is shifted.

[0134] Here, the loss from the multiplexer input to the multiplexer output L_B ｉ YA L_M ｉｋ The loss is measured before the APN-G92 is put into operation or before the line is set up in the wavelength-multiplexed WSS 72. Alternatively, the loss may be measured using light of a wavelength that does not affect the main signal multiplexed in the WSS 72, and the loss difference due to wavelength may be corrected. If the effect of installation is negligible, the factory default value may be used.

[0135] As a method for satisfying the condition that the WSS72 input strength of the terminal 83 is made uniform, any of the following methods can be considered: 1. The loss between the terminal 83 and the WSS72 input is measured in advance, and the WSS72 input strength as a result of the loss is output at a value that becomes a predetermined value, the aforementioned IB. For example, if the loss between the terminal 83 and the WSS72 input of the i-th terminal 83 is L_AB, ｉ Then, I + L_AB ｉ 2. An optical intensity meter may be placed at the input of the WSS 72, and an instruction may be given to the terminal 83 to adjust the measured intensity from the terminal 83 to a predetermined value. This is similar to the case described later.

[0136] The loss between terminal 83 and WSS72 input is L_AB ｉ is the loss L_A from the terminal 83 to the entrance of the APN-G 92 ｉ and the loss from the APN-G92 entrance to the WSS72 entrance. ｉ L_A changes depending on the distance between the terminal 83 and the APN-G 92. ｉThe loss may be measured using a measuring device such as an OTDR. In this case, the measuring device such as an OTDR is provided in the APN-G92. The loss may also be measured using a light source and intensity meter. In this case, the light source is provided in one of the terminal 83 and the APN-G92, and the measuring device is provided in the other. If there is no difference in loss between the direction from terminal 83 to APN-G92 and the direction from APN-G92 to terminal 83, either side may be provided with the measuring device. If there is directionality, for example, if the loss in the section from terminal 83 to APN-G92 is high, the differential loss may be added to the loss in the direction from APN-G92 to terminal 83. The light source and measuring device may be provided on one side, and the light from the other side may be folded back as is. In this case, the folded loss is subtracted from the measured value and the result is divided by 2. If there is a difference in loss depending on the direction, for example, if the loss in the section from terminal 83 to APN-G92 is high, the folded loss and the difference are subtracted from the measured value, divided by 2, and the difference is added.

[0137] When a light source or measuring instrument is shared for measurement, the loss difference between the shared terminals 83 is corrected. For example, if the loss of terminal i 83 is Δi greater than the loss of the OTDR, Δi is added to the OTDR measurement value. When a light source or measuring instrument is permanently installed in the APN-G92 for measurement, as shown in the figure below, it may be provided on the terminal side of the APN-G92 to which the terminal 83 is connected, or it may be shared by multiple terminals via an optical switch or the like (not shown). Sharing may be performed by the FXC 71, and it may be provided on the port opposite the terminal 83. If there is a difference between the loss at the wavelength of the optical signal used for measurement and the loss at the wavelength assigned to the terminal 83, the difference is corrected. The loss may be calculated by multiplying the transmission path length between the terminal 83 and the APN-G92 by the loss at the assigned wavelength per transmission path distance.

[0138] (Regarding Detector Accuracy) Next, the accuracy of the detector 50 will be described. As described above, in the present disclosure, wavelength shifts are measured within the accuracy range of the detector 50. Here, in the present disclosure, the upper limit of paths for which wavelength shifts can be measured is determined by the accuracy of the intensity monitor of the output of the WSS 72. In other words, the change in intensity of the wavelength-multiplexed signal caused by adding a path is limited to a level that can be measured by a measuring device. Here, the measuring device may be the detection unit 52 provided in the detector 50.

[0139] For example, if the measurement of the measuring instrument does not depend on the number of significant digits and the smallest measurement unit does not change, it will depend on that unit. If the measurement result depends on the number of significant digits, the increase due to addition will also depend on the number of significant digits. For example, the input intensity I ｉ , loss L_M ｉｋ , the allowable error δ, the actual measured value Imux before addition, and the accuracy K, the wavelength shift can be detected only within the range that satisfies the following formula: ((I ｉ -L_M ｉｋ ) - δ) / (Imux_before addition) ≧ K

[0140] In terms of significant digits, in a linear display, if the significant digit number is 1, (additional intensity) / (total intensity)<10; if the significant digit number is 2, (additional intensity) / (total intensity)<99; if the significant digit number is 3, (additional intensity) / (total intensity)<999; in a logarithmic display, if the significant digit number is 1, 10 Log((additional intensity) / (total intensity))<10; if the significant digit number is 2, 10 Log((additional intensity) / (total intensity))<99; if the significant digit number is 3, 10 Log((additional intensity) / (total intensity))<999. As shown in FIG. 11 , an example of the display on a measuring instrument when paths of the same power are added is shown when the number of significant digits is rounded to the nearest significant digit. The total input is shown in logarithmic [dBm] units in the upper left of the figure. Note that 10 Log is used here because optical power is used as the optical intensity. Electric field strength, etc. may also be used as the optical intensity. However, modifications to the example formula, etc., are required.

[0141] (Detectable Range According to Significant Digits) Next, the detectable range according to significant digits of the detector 50 will be described with reference to FIGS. 12 and 13. Here, the intensity of all paths is assumed to be 2 mW (3 dBm). As shown in FIG. 12, in a linear mW display, up to 5, 50, and 500 paths can be detected with 1, 2, and 3 significant digits, respectively. The difference in mW display is 2, 2, and 2 with 1, 2, and 3 significant digits, respectively. In a logarithmic dBm display, up to 5, 6, and 53 paths can be detected with 1, 2, and 3 significant digits, respectively. The difference in dBm display is 1, 1, and 0.1 with 1, 2, and 3 significant digits, respectively. FIG. 13 is a graph showing the increment required for detection with one significant digit. As shown in the graph, at the sixth pass in linear display, a 3mW increase, or 2.5 times the original power, or 5mW for 2.5 passes, is required, while in logarithmic display, a 20mW increase, or 11 times the original power, or 22mW for 11 passes, is required. This does not include a margin due to output accuracy. If a margin were included, the number of detectable lines would decrease even further.

[0142] In cases where the detector 50 lacks significant digits or precision, a value that varies depending on the intensity may be used. For example, consider the case of detection using an optical amplifier. Assume that the optical amplifier is operating in AGC mode with constant gain or ALC mode with constant output. In the former case, the total input power increases, so this can be detected by an increase in the pump light intensity or the pump current of the laser used to generate the pump light. In the latter case, the total input power increases, so this can be detected by a decrease in the pump light intensity or the pump current of the laser used to generate the pump light. This is suitable when the input power is displayed logarithmically with few significant digits and the pump current is displayed linearly with many significant digits.

[0143] (Other Embodiments) The detector 50 of the present disclosure can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. The program of the present disclosure is a program for causing a computer to realize each function of the detector 50 according to the present disclosure, and is a program for causing a computer to execute each procedure of the method performed by the detector 50 according to the present disclosure.

[0144] 50: Detector 51: Receiver 51A: Pre-multiplexing receiver 51B: Post-multiplexing receiver 51C: Setting receiver 52: Detector 52A: Pre-multiplexing detector 52B: Post-multiplexing detector 53: Determinator 71: FXC 72: WSS 73: Optical amplifier 74: Loopback unit 83: Terminal 91: Controller 92: APN-G 93: APN-I

Claims

1. A detector that detects a wavelength shift of a signal depending on whether the output of a multiplexer to which a signal has been added has an intensity corresponding to the addition.

2. The detector according to claim 1, wherein the wavelength shift is detected based on a difference in output intensity of the combiner before and after the addition.

3. A detector as described in claim 1, which estimates the total intensity after the multiplexer depending on the output intensity of the signal to be added or the input intensity to the multiplexer or a device upstream of the multiplexer, and detects the wavelength shift based on the estimated value and the actual measured value.

4. The detector according to claim 1, wherein a control value for excitation of an optical amplifier output from the multiplexer is estimated according to the strength of the additional signal before the multiplexer, and the wavelength shift is detected based on the estimated value and an actual measurement value.

5. A detector as described in claim 1, wherein the intensities of the multiple signals input to the multiplexer are kept constant either at their output or at the input to a device upstream of the multiplexer or the multiplexer, the output intensity from the multiplexer is estimated, and the wavelength shift is detected based on the estimated value and the actual measured value.

6. A detection method for detecting a wavelength shift of a signal depending on whether the output of a multiplexer to which a signal has been added has an intensity corresponding to the addition.

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