Monitoring device and monitoring method

Abstract

According to the present invention, a determination unit determines whether or not inadequate light, which does not satisfy a predetermined standard, is included in multiplexed light that passes through a monitoring target path. A restriction unit performs control to prevent a light signal from flowing into the path when the inadequate light is included in the multiplexed light.

Description

[Technical Field]

[0001] The present invention relates to a monitoring device and a monitoring method. [Background technology]

[0002] In recent years, there has been a demand for the realization of a transparent, low-latency optical access network using a Photonic Gateway (hereinafter referred to as "PG") (see, for example, Non-Patent Document 1). A plurality of user devices (CPE: Customer Premises Equipment) are connected to the PG, and a wavelength to be used is set for each user device. In the following description, when an optical signal flows from a source to a destination, a position relatively closer to the source is called a "preceding stage," and a position relatively closer to the destination is called a "rear stage." [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] "A new system architecture for realizing all-photonics networks," Journal of the Institute of Electronics, Information and Communication Engineers, Vol. 104, No. 5, pp. 471-477, 2021.<URL:https: / / www.journal.ieice.org / bin / pdf_link.php?fname=k104_5_471&lang=J&year=2021> Summary of the Invention [Problem to be solved by the invention]

[0004] Light that is either of an unacceptable intensity or contains wavelengths other than those specified is called non-compliant light. In a transparent network, non-compliant light must not be allowed to pass. For example, non-compliant light may be input from a user device that is not under control. However, networks that include PGs do not have a means to block or stop the output of non-compliant light. This problem is not limited to networks using PGs, but is a common problem for all transparent networks. In view of the above circumstances, an object of the present invention is to provide a technique that can block or stop the output of non-compliant light in a transparent network. [Means for solving the problem]

[0005] One aspect of the present invention is a monitoring device that monitors a route through which multiplexed light, which is light output from multiple devices, flows, and the monitoring device is equipped with a determination unit that determines whether the multiplexed light passing through the route contains non-compliant light that does not meet predetermined standards, and a restriction unit that controls the light to not flow through the route if the multiplexed light contains non-compliant light.

[0006] One aspect of the present invention is a monitoring method comprising the steps of receiving multiplexed light in which light output from multiple devices is multiplexed, determining whether the received multiplexed light includes non-compliant light that does not meet predetermined standards, and, if the multiplexed light includes non-compliant light, controlling the light so that it does not flow. [Effects of the Invention]

[0007] According to the above aspect, it is possible to cut off or stop the output of non-compliant light in a network that includes a PG. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of a desired wavelength and remaining wavelengths when the desired wavelength in a monitoring system is one wavelength. [Figure 2] FIG. 1 is a schematic block diagram showing the configuration of a monitoring system according to an embodiment 1-1. [Figure 3] 1 is a schematic block diagram showing a first configuration example of a monitoring device according to embodiment 1-1. [Figure 4] FIG. 2 is a diagram illustrating a first configuration example of a separation unit. [Figure 5] FIG. 10 is a diagram illustrating a second configuration example of the separation unit. [Figure 6] FIG. 10 is a diagram illustrating a third exemplary configuration of the separator. [Figure 7] FIG. 10 is a diagram illustrating a fourth exemplary configuration of the separator. [Figure 8] 10 is a flowchart showing a monitoring process performed by a monitoring device of a first configuration example according to embodiment 1-1. [Figure 9] FIG. 10 is a diagram illustrating a second configuration example of the monitoring device according to embodiment 1-1. [Figure 10] 10 is a flowchart showing a monitoring process performed by a monitoring device according to a second configuration example of embodiment 1-1. [Figure 11] FIG. 10 is a diagram illustrating a third configuration example of a monitoring device according to embodiment 1-1. [Figure 12] 10 is a flowchart showing a monitoring process performed by a monitoring device of a third configuration example according to embodiment 1-1. [Figure 13] FIG. 10 is a schematic block diagram showing a configuration according to a first modified example of the monitoring system according to embodiment 1-1. [Figure 14] FIG. 10 is a schematic block diagram showing a configuration according to a second modified example of the monitoring system according to embodiment 1-1. [Figure 15] FIG. 1 is a schematic block diagram showing the configuration of a monitoring system according to an embodiment 1-2. [Figure 16] FIG. 1 is a diagram showing a first configuration example of a separation device according to embodiment 1-2. [Figure 17] FIG. 10 is a diagram showing a second configuration example of a separation device according to embodiment 1-2. [Figure 18] FIG. 10 is a schematic block diagram showing a first modified example of the monitoring system according to the embodiment 1-2. [Figure 19]FIG. 1 is a schematic block diagram showing the configuration of a monitoring system according to embodiments 1-3. [Figure 20] FIG. 10 is a schematic block diagram showing a first modified example of the monitoring system according to the first to third embodiments. [Figure 21] FIG. 1 is a schematic block diagram showing the configuration of a monitoring system according to embodiments 1-4. [Figure 22] FIG. 2 is a diagram illustrating a first configuration example of a monitoring device according to embodiment 2-1. [Figure 23] 10 is a flowchart showing a monitoring process performed by a monitoring device of a first configuration example according to embodiment 2-1. [Figure 24] FIG. 10 is a diagram illustrating a second configuration example of a monitoring device according to embodiment 2-1. [Figure 25] FIG. 10 is a diagram illustrating a third configuration example of a monitoring device according to embodiment 2-1. [Figure 26] 10 is a flowchart showing a monitoring process performed by a monitoring device of a third configuration example according to embodiment 2-1. [Figure 27] FIG. 10 is a diagram illustrating a configuration of a monitoring system according to a first configuration example of a third embodiment. [Figure 28] 11 is a flowchart showing a monitoring process performed by the monitoring system according to the third embodiment. [Figure 29] FIG. 10 is a schematic diagram showing the configuration of a light distribution system according to a fourth embodiment. [Figure 30] FIG. 2 is a schematic block diagram illustrating the configuration of a control unit according to at least one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the embodiments will be described in detail with reference to the drawings. The monitoring system 11 described in the following embodiment monitors a path, such as an optical fiber, through which multiplexed light, consisting of light output from multiple user devices, flows. The multiple user devices connected to the path communicate using light of a wavelength set by a management device (not shown) that manages a network including the path. The monitoring system 11 detects user devices outputting non-compliant light among the multiple user devices connected to the path. Non-compliant light is light that does not meet a predetermined standard. For example, non-compliant light is light that contains components other than the compliant wavelength at an unacceptable intensity or light that is above a lower limit of the non-compliant intensity. The unacceptable intensity of components other than the compliant wavelength may be, for example, 1 / 100 (-20 dB) or 1 / 1000 (-30 dB) or more of the intensity of the compliant wavelength component, or may be an absolute value such as -30 dBm. The lower limit of the non-compliant intensity may be, for example, an intensity that is harmful to workers, an intensity that increases the probability of an optical fuse phenomenon, an intensity that increases the risk of burning an open end, or an intensity that increases the risk of equipment damage. For example, it may be +10 dBm. In the following description, the user device that outputs the optical signal is referred to as the "primary side," and the user device that receives the optical signal is referred to as the "secondary side." In single-core bidirectional communication, the same transmission line is the primary side for the device itself and the secondary side for the opposing device.

[0010] In the following description, the desired wavelength refers to a suitable wavelength range, and the remaining wavelength refers to a wavelength range other than the desired wavelength. Figure 1 is a schematic diagram of the desired wavelength and the remaining wavelength when there is one desired wavelength in the monitoring system 11. There may be multiple desired wavelengths for one user device. The suitable wavelength range varies depending on the wavelengths that the user device can use. For example, at the time of initial connection (when no wavelengths are set in the user device), the suitable wavelength range is the wavelength range that can be used for the initial connection, and after a wavelength is set in the user device after the initial connection, the set wavelength range becomes the suitable wavelength range.

[0011] <Embodiment 1-1> A monitoring system 11 according to embodiment 1-1 is provided on a path of a network or the like, and detects a user device that outputs light of an incompatible wavelength among a plurality of user devices connected to the path.

[0012] <Configuration of Monitoring System 11> 2 is a schematic block diagram showing the configuration of a monitoring system 11 according to embodiment 1-1. The monitoring system 11 according to embodiment 1-1 includes an optical multiplexer / splitter 120 and a monitoring device 130. The optical multiplexer / splitter 120 is provided on a path to be monitored, and splits and outputs light input from the primary side to the secondary side and the monitoring device 130 side. The monitoring device 130 detects a user device that outputs light of an incompatible wavelength based on the light input from the optical multiplexer / splitter 120.

[0013] FIG. 3 is a schematic block diagram showing a first configuration example of the monitoring device 130 according to embodiment 1-1. The monitoring device 130 according to the embodiment 1-1 includes an optical multiplexer / splitter 160, a plurality of splitters 217, a measurement unit 132, and a control unit 50. The optical multiplexer / splitter 160 splits the light input from the optical multiplexer / splitter 120 provided on the path, and outputs the split light to each of the plurality of splitters 217.

[0014] 《Separation section 217》 The demultiplexer 217 processes the input optical signal (hereinafter referred to as the "demultiplexed input signal"). The demultiplexer 217 has three ports: an input port, a first output port, and a second output port. The demultiplexer 217 wavelength-demultiplexes an optical signal (demultiplexed input signal) input from the input port into a signal of a desired wavelength (hereinafter referred to as a "desired demultiplexed signal") set in the user device by a management device (not shown) that manages the network, and a signal of a remaining wavelength (hereinafter referred to as a "residual demultiplexed signal"), which is the other wavelength components. The desired demultiplexed signal is output from the first output port, and the residual demultiplexed signal is output from the second output port. However, in embodiment 1-1, the desired demultiplexed signal is not used in the monitoring device 130, so the first output port of the demultiplexer 217 may be non-reflection terminated. The demultiplexer 217 obtains wavelength setting data from the management device and sets the wavelength to be demultiplexed. The configuration of the demultiplexer 217 will be described later.

[0015] Depending on the characteristics (suppression ratio, cutoff power) of the filter used in the processing in the separation unit 217, if there is a residual wavelength component, the desired separated signal will be slightly mixed with the residual wavelength component, and if there is a desired wavelength component, the residual separated signal will be slightly mixed with the desired wavelength component. However, if the ratio of the desired signal in the separated input signal is significantly large, the desired signal will account for the majority of the desired separated signal and the residual separated signal, and if the ratio of the residual signal in the separated input signal is significantly large, the residual signal will account for the majority of the desired separated signal and the residual separated signal. This can also occur depending on the suppression ratio of the filter.

[0016] (First configuration example of the separator 217) FIG. 4 is a diagram showing a first configuration example of the separator 217. The separator 217 according to the first configuration example includes an FBG (Fiber Bragg Grating). An FBG is configured by inscribing a diffraction grating into an optical fiber. When light is incident on the FBG, only light with a specific wavelength component according to the spacing of the diffraction grating is reflected, while light with other wavelength components passes through. By utilizing such characteristics and selecting an FBG that reflects light of a desired wavelength for the corresponding user device, the separator 217 can be configured using an FBG.

[0017] The separation unit 217 includes a circulator 211 and an FBG 212. The circulator 211 inputs an optical signal input from the primary side of the path to the FBG 212. The circulator 211 outputs an optical signal input from the FBG 212 to the secondary side of the path. The circulator 211 may be configured using, for example, an optical multiplexer / demultiplexer. When the circulator 211 is configured using a 2×2 optical multiplexer / demultiplexer, two ports on one side function as an input port and an output port, one of the two ports on the opposite side is connected to the FBG 212, and the other port is configured as a non-reflective termination. The circulator 211 may also be configured using a 2×1 optical multiplexer / demultiplexer so as not to have an open end. In this case, two ports on one side function as an input port and an output port, and one port on the opposite side is connected to the FBG 212. The FBG 212 reflects an optical signal of a desired wavelength and transmits optical signals of the remaining wavelengths. By such reflection and transmission, the desired separated signal and the residual separated signal are separated from the separated input signal. In the embodiment 1-1, since the desired separated signal is not used in the monitoring device 130, the separator 217 may be configured as a two-port device having an input port and an output port for outputting the residual separated signal, without including the circulator 211. In other words, the separator 217 according to the embodiment 1-1 may be configured to include an FBG 212 between the input port and the output port.

[0018] (Second configuration example of the separator 217) 5 is a diagram showing a second configuration example of the separator 217. The separator 217 according to the second configuration example includes a TFF (Thin Film Filter). The TFF is a wavelength filter that reflects a portion of light that is input so as to intersect with the film surface and transmits the remainder. The TFF can vary the wavelength of light that is reflected or transmitted depending on the angle of incidence of the light. The TFF is controlled to transmit a desired separated signal of a corresponding user device and to reflect the remaining separated signal. The demultiplexer 217 includes a circulator 211 and a TFF 214. The circulator 211 inputs an optical signal input from the primary side of the path to the TFF 214. The circulator 211 inputs an optical signal input from the TFF 214 to the monitoring device 130. The configuration of the circulator 211 is as described above.

[0019] 3 and 4, the light traveling direction is opposite to that of the drawing. The light traveling direction of circulator 211 is opposite to that of circulator 211 in FIG. 3 and 4, respectively, depending on whether the element in separator 217 is configured to reflect light of a suitable wavelength, such as FBG 212, or to transmit light of a suitable wavelength, such as TFF 214.

[0020] The TFF 214 transmits an optical signal of the desired wavelength and reflects an optical signal of the remaining wavelength. The optical signal reflected by the TFF 214 (the remaining demultiplexed signal) is input to the monitoring device 130 via the circulator 211. Through such reflection and transmission, the desired demultiplexed signal and the remaining demultiplexed signal are separated from the demultiplexed input signal. Note that in the configuration of FIG. 4 that transmits the desired wavelength, the circulator 211 may be configured using an optical multiplexer / demultiplexer, as in the configuration of FIG. 3 that reflects the desired wavelength. This also applies to other configurations.

[0021] (Third Configuration Example of Separator 217) FIG. 6 illustrates a third exemplary configuration of the demultiplexer 217. The demultiplexer 217 includes a circulator 211 and a TFF 214. The circulator 211 inputs an optical signal input from the primary side of the path to the TFF 214. The circulator 211 outputs an optical signal input from the TFF 214 to the secondary side of the path. The circulator 211 may be configured using, for example, an optical multiplexer / demultiplexer, as in the first exemplary configuration described in FIG. 3. The TFF 214 reflects an optical signal of a desired wavelength for a corresponding user device and transmits an optical signal of a residual wavelength. Through such reflection and transmission, the desired demultiplexed signal and the residual demultiplexed signal are demultiplexed from the demultiplexed input signal. In the embodiment 1-1, since the desired demultiplexed signal is not used in the monitoring device 130, the demultiplexer 217 may be configured as a two-port device without the circulator 211, having an input port and an output port for outputting the residual demultiplexed signal. That is, the separator 217 according to the embodiment 1-1 may have a configuration including the TFF 214 between the input port and the output port.

[0022] (Fourth Configuration Example of Separator 217) FIG. 7 illustrates a fourth exemplary configuration of the demultiplexer 217. The demultiplexer 217 includes an arrayed-waveguide grating (AWG) 215 and a multiplexer 216. The AWG 215 outputs optical signals input from the primary side of the path from ports corresponding to the wavelengths. Of the multiple output ports of the AWG 215, the output ports from which desired demultiplexed signals of the corresponding user devices are output are connected to the secondary side of the path. The remaining output ports are connected to the multiplexer 216. The multiplexer 216 multiplexes the multiple residual demultiplexed signals input from the AWG 215 and outputs the multiplexed signal to the monitoring device 130. The multiplexer 216 may be any device capable of multiplexing optical signals of multiple wavelengths. For example, the multiplexer 216 may be configured using an AWG. In this case, the multiple output ports from which the residual demultiplexed signals of the AWG 215 are output are connected to input ports of the multiplexer 216 (AWG) corresponding to the wavelengths of the respective residual signals. The multiplexer 216 may be configured using an optical multiplexer / branch. An isolator may be provided between the demultiplexer 170 and the monitoring device 130. Note that the multiplexer 216 should preferably have wavelength transmission characteristics equivalent to or less than those of the AWG 215, for example, one with greater crosstalk between adjacent channels, i.e., adjacent ports, in order to prevent output non-compliant wavelength components from being blocked by the multiplexer / demultiplexer and going undetected.

[0023] (Another configuration example of the separation unit 217) Alternatively, the separator 217 may be configured using a waveguide-type ring resonator, a lattice-type optical filter, a Mach-Zehnder interferometer, or the like. The waveguide-type ring resonator may be, for example, a micro ring resonator (MRR) with a resonator length of several tens of micrometers and a resonant wavelength interval (free spectral range: FSR) of several tens of nanometers. The ring resonator may have a racetrack shape, rather than a perfect circle, in which the coupling section is a parallel linear waveguide. This configuration facilitates design of the coupling coefficient at the coupling section. Specifically, the waveguide-type ring resonator receives an optical signal from the primary side of the path at the input port, outputs a desired demultiplexed signal from the drop port to the secondary side of the path, and outputs a residual demultiplexed signal from the through port to the monitoring device 130. It is desirable to connect a reflectionless termination or an isolator to the add port. A lattice optical filter is composed of, for example, a delay line, a symmetric Mach-Zehnder interferometer-type variable coupling coupler, and a phase adjustment unit. By changing the phase shift value of the optical filter, any filter characteristic can be obtained, with the performance upper limit determined by the asymmetric Mach-Zehnder interferometer. This utilizes the property that the characteristics appear periodically for each FSR (Free Spectral Range) determined by ΔL. In a lattice optical filter, the path length difference between each asymmetric MZI that makes up the lattice is ΔL. When signal light is input to the port on the primary side, the first port on the secondary side outputs a compatible wavelength component, and the second port on the secondary side outputs an incompatible wavelength component, by adjusting the delay ΔL, the coupling ratio of the variable coupling coupler, and the phase θ of the phase shifter. When using a Mach-Zehnder interferometer, a pair of FBGs is installed in each arm of the Mach-Zehnder interferometer. If the distances from the input directional coupler constituting the Mach-Zehnder interferometer to the two gratings are the same, their reflected light will merge and interfere, and then be output from the lower-left port. Therefore, it is necessary not only to match the characteristics of the two gratings, but also to match the distance from the directional coupler to a precision of at least one wavelength, for example, one-tenth of a wavelength or less. Therefore, after forming the grating, a method is required to adjust the optical length by so-called trimming, which involves irradiating the area between the grating and the directional coupler with ultraviolet light to change the refractive index.

[0024] "Measurement Section 132"

[0025] The measuring unit 132 measures the intensity of the light output from the separating unit 217. For example, the measuring unit 132 may be realized by a combination of a photoelectric conversion element such as a PD (photodiode) or an APD (avalanche photodiode) and a circuit that measures voltage.

[0026] <<Control unit 50>> The control unit 50 performs control to detect a user device that outputs light of an incompatible wavelength. As shown in FIG.

[0027] The determination unit 136 determines whether the intensity of the multiplexed light measured by the measurement unit 132 exceeds a no-signal threshold. The no-signal threshold is set to an intensity that is acceptable for components other than the wavelength that is to be matched, for example, an intensity at which it is considered that no signal is being received.

[0028] The limiting unit 137 outputs instructions related to the output of the optical signal to the user equipment. Specifically, when the user equipment is to be limited in the output of the optical signal, the limiting unit 137 outputs a limiting instruction to the user equipment. The output limiting may be, for example, stopping the output or reducing the output intensity. When the user equipment is to be released from the output limit of the optical signal, the limiting unit 137 outputs a limit-removal instruction to the user equipment. The limit-removal may be, for example, starting or resuming the output or increasing the output intensity. The instruction from the limiting unit 137 may be transmitted via communication using a predetermined carrier, or may be transmitted by multiplexing the main signal using frequency division multiplexing or time division multiplexing such as AMCC (Auxiliary Management and Control Channel), or may be transmitted via a specific communication route. Alternatively, the limiting unit 137 may issue a notification related to the output limit to a management device, and the management device, upon receiving the notification, may output an instruction to the user equipment.

[0029] FIG. 8 is a flowchart showing the monitoring process by the monitoring device 130 of the first configuration example according to embodiment 1-1. The monitoring device 130 according to the embodiment 1-1 executes the first monitoring process shown in Fig. 8 at every predetermined monitoring period. The limiting unit 137 transmits a signal light limiting instruction to all user devices connected to the route monitored by the monitoring device 130 (step S151).

[0030] Next, the monitoring device 130 inspects each user device as a suspect device for wavelength abnormalities in the following procedure from step S152 to step S158. "Wavelength abnormality" refers to an abnormality related to the output of light with an incompatible wavelength. A suspect device refers to a user device for which the suspicion of wavelength abnormality has not been resolved. First, the restriction unit 137 selects one of the suspect devices (step S152) and transmits an instruction to the suspect device to lift the restriction on the signal light (step S153). The measurement unit 132 measures the intensity of the residual demultiplexed signal input from the demultiplexer 217 corresponding to the selected user device (step S154). The residual demultiplexed signal received at this time is the residual demultiplexed signal demultiplexed from the light output from the user device selected in step S152.

[0031] The determination unit 136 determines whether the intensity of the residual separated signal measured in step S154 exceeds the no-signal threshold (step S155). If the intensity of the residual separated signal does not exceed the no-signal threshold (step S155: NO), the determination unit 136 determines that the user equipment selected in step S152 is normal. On the other hand, if the intensity of the residual separated signal exceeds the no-signal threshold (step S155: YES), the determination unit 136 determines that the user equipment selected in step S152 has a wavelength abnormality. The restriction unit 137 stores the ID of the user equipment selected in step S152 in an internal memory (step S156). After determining whether the user equipment selected in step S152 is normal, the restriction unit 137 transmits a restriction instruction to the user equipment (step S157).

[0032] The monitoring device 130 determines whether any suspicious devices remain (step S158). If any suspicious devices remain (step S158: NO), the monitoring device 130 returns the process to step S152 and inspects the remaining suspicious devices. On the other hand, if any suspicious devices remain, the monitoring device 130 transmits a restriction release instruction to user devices other than the user device stored in step S156 (step S159), and ends the process.

[0033] The processing of the monitoring device 130 is not limited to the first monitoring processing shown in FIG. 8. For example, in another embodiment, instead of the first monitoring processing, monitoring may be performed using the following procedure. The monitoring device 130 does not issue a restriction instruction in step S151 of FIG. 8, and instead of issuing a restriction release instruction in step S153, sends a restriction instruction only to the selected suspected device. The monitoring device 130 maintains the restricted state if the change in the measured value of the intensity before and after sending the restriction instruction in step S155 of FIG. 8 exceeds the no-signal threshold. The monitoring device 130 sends a restriction release instruction if the change in the measured value of the intensity before and after sending the restriction instruction in step S155 of FIG. 8 does not exceed the no-signal threshold. That is, if the amount of change before and after the restriction is equal to or greater than the no-signal threshold, i.e., if the residual separated signal decreases by more than the no-signal threshold, the output of the residual component was non-zero, and therefore the target user device can be presumed to be suspect. On the other hand, if the amount of change before and after the restriction is less than the no-signal threshold, i.e., if the residual separated signal does not decrease by more than the no-signal threshold, then the output of the residual component can be presumed to be non-zero, and therefore the target user device can be presumed not to be suspect. In this case, the restriction instruction is not transmitted in step S157, and the restriction release instruction is not transmitted in step S159. Also, recording the suspected device in step S156 is not necessarily performed. In another embodiment, no restriction instruction is issued in step S151, and instead of a restriction removal instruction, a restriction instruction is sent only to the selected suspected device in step S153, and in step S155, whether the suspected device is non-compliant is recorded based on the change in the measured intensity before and after the restriction instruction is sent, and regardless of whether the suspicion has been resolved, a restriction removal instruction is sent instead of a restriction instruction in step S157, and if it is determined in step S158 that the suspected device has disappeared, a restriction instruction is output instead of a restriction removal instruction in step S159 to the device recorded as non-compliant in step S156, and the process ends.

[0034] The monitoring device 130 detects user devices that output light of incompatible wavelengths based on the intensity of the residual demultiplexed signals, but this is not limited to this. For example, in another embodiment, the monitoring device 130 may detect user devices that output light of incompatible wavelengths based on the intensity of the desired demultiplexed signals. That is, in the monitoring device 130, the first output port of the demultiplexer 217 may be connected to the measurement unit 132, and the second output port may be terminated. In this case, in step S154, the determination unit 136 measures the intensity of the desired demultiplexed signals output from the demultiplexers 217 other than the demultiplexer 217 related to the suspected device. Since no other user devices than the suspect device are outputting light, if the desired split signal corresponding to at least one other user device exceeds the no-signal threshold (is non-zero), it is determined that the suspect device is outputting light of an incompatible wavelength. In this case, the monitoring device 130 can identify which user device's desired light is leaking the incompatible light. In addition, the monitoring device 130 according to another embodiment may limit the optical output of one user device and release the limit on the other user devices, and detect user devices that output optical signals with incompatible wavelengths based on the intensity of the desired demultiplexed signals. In this case, the determining unit 136 measures the intensity of the desired demultiplexed signals output from the demultiplexer 217 associated with the one user device whose optical output was limited in step S154. Since only one user device with limited output power does not output light, if the intensity of the desired demultiplexed signal of that user device is non-zero (above the no-signal threshold), it is determined that one of the other user devices is outputting light of an incompatible wavelength. Note that in this case, it is not possible to determine whether the user device whose output has been stopped is outputting light of an incompatible wavelength. Therefore, for example, the monitoring device 130 stops multiple user devices and searches for combinations where the intensity of the desired demultiplexed signals of the multiple user devices becomes zero (below the no-signal threshold), and determines that the user device whose output power was not limited at that time is not suspect.

[0035] (Second Configuration Example of Monitoring Device 130) 9 is a diagram showing a second configuration example of the monitoring device 130 according to embodiment 1-1. The monitoring device 130 according to the second configuration example includes a spectrum analyzer 138 instead of the optical multiplexer / splitter 160, the separator 217, and the measuring unit 132 of the first configuration example. Other configurations of the monitoring device 130 according to the second configuration example are the same as those of the first configuration example. The spectrum analyzer 138 measures the distribution of wavelength components included in the received signal, i.e., the relationship between wavelength and intensity.

[0036] FIG. 10 is a flowchart showing the monitoring process by the monitoring device 130 according to the second configuration example of embodiment 1-1. The monitoring device 130 according to the second configuration example of the embodiment 1-1 executes the monitoring process shown in Fig. 10 at predetermined monitoring intervals. The limiting unit 137 transmits a signal light limiting instruction to all user devices connected to the route monitored by the monitoring device 130 (step S171).

[0037] Next, the monitoring device 130 treats each user device as a suspect device and inspects for wavelength abnormalities in the following procedure from step S172 to step S178. First, the restriction unit 137 selects one of the suspect devices (step S172) and transmits an instruction to the suspect device to remove the restriction on the signal light (step S173). The spectrum analyzer 138 measures the distribution of wavelength components of the light input from the optical multiplexer / demultiplexer 120 (step S174).

[0038] The determination unit 136 determines whether the intensity of the component related to the remaining wavelength of the user device selected in step S172, among the wavelength components measured in step S174, exceeds the no-signal threshold (step S175). If the intensity of the remaining wavelength component does not exceed the no-signal threshold (step S175: NO), the determination unit 136 determines that the user device selected in step S172 is normal. On the other hand, if the intensity of the remaining wavelength component exceeds the no-signal threshold (step S175: YES), the determination unit 136 determines that the user device selected in step S172 has a wavelength abnormality. At this time, the determination unit 136 can identify whether incompatible light is leaking to the desired wavelength of another user device by checking whether the wavelength of the component exceeding the no-signal threshold is the desired wavelength of another user device. The restriction unit 137 stores the ID of the user device selected in step S172 in a storage device (such as a memory) (not shown) (step S176). After determining whether the user device selected in step S172 is normal, the restriction unit 137 transmits a restriction instruction to the user device (step S177).

[0039] The monitoring device 130 determines whether any suspicious devices remain (step S178). If any suspicious devices remain (step S178: NO), the monitoring device 130 returns the process to step S172 and inspects the remaining suspicious devices. On the other hand, if any suspicious devices remain, the monitoring device 130 transmits a restriction release instruction to user devices other than the user device stored in step S176 (step S179), and ends the process.

[0040] Note that the processing of the monitoring device 130 is not limited to the first monitoring processing shown in Fig. 10. For example, in another embodiment, a restriction instruction is not issued in step S171, and instead of a restriction release instruction in step S173, a restriction instruction is sent only to the selected suspected device, and if the change in the measured value of the intensity of the residual wavelength component before and after sending the restriction instruction in step S175 exceeds the no-signal threshold, the restricted state is maintained, and if it does not exceed the no-signal threshold, a restriction release instruction is sent. In this case, the recording of the suspected device in step S156, the sending of the restriction instruction in step S157, and the sending of the restriction release instruction in step S159 are not performed. In another embodiment, no restriction instruction is issued in step S171, and instead of a restriction removal instruction, a restriction instruction is sent only to the selected suspected device in step S173, and in step S175, whether the suspected device is non-compliant is recorded based on the change in the measured intensity before and after the restriction instruction is sent, and regardless of whether the suspicion has been resolved, a restriction removal instruction is sent instead of the restriction instruction in step S177, and if it is determined in step S178 that the suspected device has disappeared, a restriction instruction is output instead of the restriction removal instruction in step S159 to the device recorded as non-compliant in step S176, and the process ends.

[0041] In another embodiment, instead of the spectrum analyzer 138, a multiplexer / demultiplexer that outputs multiple wavelengths to different outputs, such as an AWG 215 having at least one input port and multiple output ports, and a measurement unit 132 that measures the intensity of light input from each of the multiple ports may be provided. In this case, the measurement unit 132 can measure the intensity of light input from the port corresponding to the desired wavelength of each user device as the intensity of the desired wavelength, and measure the sum of the intensities of light input from the other ports as the intensity of the remaining wavelengths. With this configuration, there is no need for wavelength sweeping like with the spectrum analyzer 138, and therefore the measurement processing time can be shortened.

[0042] (Third Configuration Example of Monitoring Device 130) FIG. 11 is a diagram illustrating a third exemplary configuration of the monitoring device 130 according to embodiment 1-1. The monitoring device 130 according to the third exemplary configuration includes a dithering instruction unit 139 in addition to the components of the first exemplary configuration. Other components of the monitoring device 130 according to the third exemplary configuration are the same as those of the first exemplary configuration. The dithering instruction unit 139 outputs a dithering instruction and a dithering cancellation instruction to the user equipment. The dithering instruction is an instruction to modulate (or superimpose modulation on) an optical signal with a frequency or time series pattern that differs for each user equipment. Hereinafter, the frequency or time series pattern that modulates the optical signal according to the dithering instruction will be referred to as a dithering component. The dithering component allows the user device that transmitted the optical signal modulated with the dithering component to be uniquely identified. On the other hand, the dithering cancellation instruction instructs the user device to stop modulating the optical signal with the dithering component.

[0043] Furthermore, the measurement unit 132 according to the third exemplary configuration has a function of extracting the intensity of the dithering component of each user device from the received intensity of the optical signal. If the dithering component is a frequency, the measurement unit 132 extracts the intensity of the frequency component. If the dithering component is a pattern, the measurement unit 132 extracts the intensity of the component corresponding to the pattern. The measurement unit 132 includes, for example, a lock-in amplifier.

[0044] 12 is a flowchart showing the monitoring process by the monitoring device 130 of the third configuration example according to embodiment 1-1. The monitoring device 130 executes the monitoring process shown in FIG. 12 at every predetermined monitoring cycle. The dithering instruction unit 139 determines a different pattern for each of the user devices connected to the route monitored by the monitoring device 130, and transmits a dithering instruction to each user device using the determined pattern (step S121). An example of a modulation pattern is one in which the intensity of the optical signal is changed at a different frequency for each user device. In this case, the dithering instruction unit 139 determines the frequencies of each user device to be frequencies that are not multiples or divisors of each other. Another example of a modulation pattern is one in which the intensity or wavelength of the optical signal is changed at a different timing for each user device. In this case, the dithering instruction unit 139 determines the timings for changing the intensity for each user device to be timings that do not overlap with each other.

[0045] The measuring unit 132 measures the intensity of each residual separated signal input from each separating unit 217 for a certain period (step S122). The measuring unit 132 detects a dithering component of a frequency set for the corresponding user device in the residual separated wavelength of the corresponding user device from the time series of the intensity of each residual separated signal for the certain period (step S123).

[0046] Next, the monitoring device 130 selects the user devices one by one (step S124) and executes the following process. The determination unit 136 determines whether the dithering component set for the selected user device is detected in the remaining separation wavelength of the selected user device at a level exceeding the no-signal threshold (step S125). If the dithering component set for the corresponding user device is not detected or is detected at a level below the no-signal threshold (step S125: NO), the determination unit 136 determines that the corresponding user device is normal. On the other hand, if the dithering component set for the corresponding user device is detected at a level exceeding the no-signal threshold (step S125: YES), the determination unit 136 determines that the corresponding user device has a wavelength abnormality. In this case, the limiting unit 137 transmits a signal light limiting instruction to the corresponding user device (step S126). This allows the output of optical signals by user devices that output light with incompatible wavelengths to be stopped. When the monitoring device 130 performs the above-described determination process for each user device, the dithering instruction unit 139 transmits a dithering cancellation signal to the user device that is determined to be normal (step S127).

[0047] The monitoring device 130 detects user devices outputting light with incompatible wavelengths based on the intensity of the residual demultiplexed signals, but this is not limited to this. For example, in another embodiment, the monitoring device 130 may detect user devices outputting light with incompatible wavelengths based on the intensity of the desired demultiplexed signals. That is, in the monitoring device 130, the first output port of the demultiplexer 217 may be connected to the measurement unit 132, and the second output port may be terminated. In this case, the determination unit 136 measures the intensity of the desired demultiplexed signals output from demultiplexers 217 other than the demultiplexer 217 associated with the suspected device in step S122. If the intensity of the dithering component associated with the suspected device in the desired demultiplexed signals output from at least one demultiplexer 217 exceeds the no-signal threshold, it is determined that the suspected device is outputting light with incompatible wavelengths. In this case, the monitoring device 130 can identify which user device the incompatible light is leaking into.

[0048] In another embodiment, the control unit 50 of the monitoring device 130 equipped with the spectrum analyzer 138 as shown in Fig. 9 may also be equipped with a dithering instruction unit 139 as shown in Fig. 11. In this case, the spectrum analyzer 138 can perform the same processing by determining whether the intensity of the residual wavelength component of each user device exceeds the no-signal threshold in step S125 shown in Fig. 12. In another embodiment, instead of the optical multiplexer / demultiplexer 160 and the multiple demultiplexers 217, a multiplexer / demultiplexer that outputs multiple wavelengths to different outputs, such as a single AWG 215 with at least one input port and multiple output ports, may be provided. In this case, the measurement unit 132 measures the intensity of light input from the port corresponding to the desired wavelength of each user device as the intensity of the desired wavelength component, and measures the sum of the intensities of light input from the other ports as the intensity of the remaining wavelength component. The control unit 50 can then perform similar processing by determining whether the intensity of the remaining wavelength component of each user device exceeds the no-signal threshold in step S125 shown in FIG. 12. As described above, even in a configuration with a single multiplexer / demultiplexer instead of the optical multiplexer / demultiplexer 160 and multiple demultiplexers 217, it is possible to detect user devices that output light of incompatible wavelengths based on the intensity of the desired demultiplexed signal. In this case, the control unit 50 can perform similar processing by measuring the intensity of light input from the port corresponding to the desired wavelength of each user device as the intensity of the desired wavelength component and determining whether or not the dithering component of the suspect device is included.

[0049] Actions and Effects As described above, the monitoring device 130 according to embodiment 1-1 controls the user equipment (UE) to stop transmitting optical signals by transmitting a stop signal to the UE when the intensity of the residual demultiplexed signal from the demultiplexer 217 exceeds the no-signal threshold. The wavelength included in the residual demultiplexed signal is a wavelength that has not been set for the UE by the host device. In other words, the intensity of the residual demultiplexed signal exceeding the no-signal threshold indicates that the multiplexed light contains light with an incompatible wavelength. Note that in the initial state until the desired wavelength is set by the host device, the demultiplexer 217 passes light of all wavelengths to the secondary side and does not need to demultiplex the light. Note that if user equipment in the initial state and user equipment with the desired wavelength set exist together due to the addition of user equipment, the demultiplexer 217 may initialize and re-verify user equipment that was previously stopped due to a mismatch. As long as there are user equipment in the initial state, even if there is non-compatible light corresponding to the initial state, it may be assumed that the mismatch is due to the user equipment in the initial state. The monitoring device 130 may not identify non-compatible UTs, but may identify non-compatible UTs after the desired wavelength is set. Furthermore, until the desired wavelength is set, the monitoring device 130 may initially set a wavelength that can be used as the desired wavelength, and after the desired wavelength is set, change the desired wavelength to the set wavelength and execute the above-mentioned monitoring process. In this way, the monitoring device 130 can control the PG so that non-compliant light is not conducted.

[0050] Furthermore, when non-compliant light is included in the multiplexed light, the monitoring device 130 according to the first and second configuration examples controls the optical signals from some of the multiple user devices to flow and the optical signals from the other user devices to not flow, and then determines whether the intensity of the optical signals from some of the user devices exceeds a no-signal threshold. Specifically, the monitoring device 130 stops the output of optical signals from the connected user devices, and then causes them to output optical signals one after another. This allows the monitoring device 130 to identify user devices with wavelength abnormalities and control the flow of optical signals from those user devices.

[0051] Although the monitoring device 130 according to the first and second exemplary configurations identifies user devices with wavelength abnormalities by switching between user devices that output optical signals one by one, this is not a limitation. For example, in another embodiment, the monitoring device 130 may identify user devices with wavelength abnormalities by switching between user devices that do not output optical signals one by one. In this case, the determining unit 136 determines that a user device is outputting non-compliant light if the difference between the optical intensity of the optical signal of a user device before and after the restriction exceeds the no-signal threshold. Furthermore, in another embodiment, the monitoring device 130 may identify user devices with wavelength abnormalities by, for example, binary search. In this case, the monitoring device 130 stops the optical signals of half of the connected user devices. If the intensity of the multiplexed light received immediately after stopping the optical signals does not fall below the no-signal threshold, the monitoring device 130 stops the optical signals of the other half of the user devices that are not within the acceptable range, and continues this process until a wavelength abnormality is identified. On the other hand, if the intensity of the multiplexed light received immediately after stopping the optical signal falls below the no-signal threshold, the monitoring device 130 causes half of the user devices that stopped the signal to output an optical signal. If the intensity of the multiplexed light received immediately after stopping the optical signal falls below the no-signal threshold, the suspicion of a wavelength anomaly is eliminated for the user devices that output the optical signal. By repeating the above procedure, the monitoring device 130 can identify the user device that outputs non-compliant light.

[0052] Furthermore, the monitoring device 130 according to the third exemplary configuration can identify a user device that outputs non-compliant light by observing the dithering component while maintaining the output of an optical signal to the user device.

[0053] According to the monitoring device 130 of each of the configuration examples of the above-described embodiment 1-1, each user device operates in accordance with the restriction instruction and restriction removal instruction from the monitoring device 130, thereby detecting non-conformity of each user device and controlling the transmission of non-conforming light. On the other hand, even if some user devices do not comply with the restriction instruction and restriction removal instruction, the monitoring device 130 can determine whether the other user devices are non-conforming. For example, if only one user device has a wavelength abnormality and only that user device does not comply, when a restriction signal is transmitted to each user device in step S153 or S173, the other user devices will stop outputting in accordance with the restriction signal, while only the user device with the wavelength abnormality does not stop outputting. Therefore, the monitoring device 130 measures the optical intensity after transmitting the restriction instruction in step S153 or S173 and resets the no-signal threshold based on the difference from the measured intensity, thereby determining the output of a user device with normal output. Furthermore, if a user device with normal output does not comply with the instruction, it can be identified even if there are multiple user devices that do not comply with the instruction. In this case, the monitoring device 130 may determine whether the user device follows the instruction based on a confirmation response or the like to the user device.

[0054] Instead of the optical multiplexer / demultiplexer 160 and the multiple demultiplexers 217 shown in FIGS. 3 and 11, the monitoring device 130 may include a multiplexer / demultiplexer, such as an AWG 215, that outputs multiple wavelengths to different outputs. The AWG 215 has at least one input port and multiple output ports. All of the multiple output ports of the AWG 215 are connected to the monitoring device 130, and the intensity of each port is measured individually. The AWG 215 outputs an optical signal input from the primary side of the path from a port corresponding to the wavelength. Therefore, light of the desired wavelength for each user device is output from a different output port. As a result, when determining whether or not a certain user device is incompatible, the monitoring device 130 can identify the port through which the desired wavelength of the user device is input and determine whether or not the mismatch exists based on the light input to that port or based on the light input to ports other than the identified port.

[0055] First Modified Example FIG. 13 is a schematic block diagram showing a configuration according to a first modification of the monitoring system 11 according to embodiment 1-1. The monitoring system 11 according to the first modification includes, in addition to the configuration according to embodiment 1-1, a blocking unit 150 located downstream of the optical multiplexer / splitter 120. The blocking unit 150 switches between passing and blocking an input optical signal according to instructions from the monitoring device 130. The blocking unit 150 may be, for example, a fiber cross connect (FXC) controlled to connect or disconnect a path, an optical switch (OS), an optical attenuator with a desired suppression ratio, a semiconductor optical amplifier (SOA) with a desired suppression ratio that controls gain to switch between passing and blocking, and a modulator with a desired suppression ratio. When the blocking unit 150 is implemented using a modulator, the following specific configurations can be adopted. For example, the modulator may be a device that uses the electrorefractive ER effect, which changes the refractive index by controlling the carrier (conduction electrons and holes) concentration, or a device that changes the optical absorption rate by applying an electric field. The blocking unit 150 may also be a device that uses the electroabsorption (EA) effect. Among the ER types, those with a wide cutoff wavelength (for example, a Mach-Zehnder type) are particularly suitable. Note that, regardless of the configuration of the cutoff unit 150, the wavelengths that it can cut off include compatible and non-compatible target wavelengths. The target wavelengths include at least wavelengths that may be assigned to user devices by a management device. It is also preferable that the target wavelengths include wavelengths that are unlikely to be assigned but may cause problems for communication devices due to nonlinear optical effects such as the Raman effect and four-wave mixing, and wavelengths that may affect the gain and wavelength-related gain characteristics of an optical amplifier (not shown) on the path. Note that the configuration of the demultiplexer 217 and the configuration of the monitoring device 130 may be those shown in the configuration examples of embodiment 1-1.

[0056] The monitoring device 130 according to the first modification performs the following processing in addition to the monitoring processing of embodiment 1-1. The limiting unit 137 of the monitoring device 130 outputs a blocking instruction to the blocking unit 150 when the intensity of at least one residual separated signal exceeds the no-signal threshold. This causes the blocking unit 150 to block light input from the primary side. This allows the monitoring device 130 to output a blocking instruction to the blocking unit 150 when there is one or more residual separated signals whose intensity exceeds the no-signal threshold, thereby preventing non-compliant light from being conducted to the secondary side of the path. The limiting unit 137 of the monitoring device 130 outputs an opening instruction to the blocking unit 150 after the intensity of the residual separated signal related to the user device to be blocked no longer exceeds the no-signal threshold. Note that the monitoring system 11 shown in Fig. 13 blocks light output from all user devices if any one of the multiple user devices is to be blocked. As a result, the blocking unit 150 conducts the light input from the primary side of the path to the secondary side.

[0057] In this way, the monitoring device 130 according to the first modification of embodiment 1-1 includes the blocking unit 150, and thus can prevent non-compliant light from being conducted to the secondary side even when a user device outputs an optical signal without following the instruction of the monitoring device 130. Note that if a user device 20 that outputs light with a non-compliant wavelength does not follow the restriction instruction, the signal light of not only that user device 20 but also other user devices 20 remains blocked.

[0058] Second Variation 14 is a schematic block diagram showing a configuration according to a second modified example of the monitoring system 11 according to embodiment 1-1. According to the second modified example, the blocking unit 150 of the monitoring system 11 may be provided in a stage preceding the optical multiplexer / splitter 120. The monitoring device 130 executes a monitoring process similar to that of embodiment 1-1, for example, and then outputs a blocking instruction to the blocking unit 150 if the intensity of the residual separated signal remains above the no-signal threshold because the user device does not follow the restriction instruction.

[0059] <Embodiment 1-2> Fig. 15 is a schematic block diagram showing the configuration of a monitoring system 11 according to embodiment 1-2. In the monitoring system 11 according to embodiment 1-1, multiplexed light is input from one port on the primary side, while the monitoring system 11 according to embodiment 1-2 has multiple ports on the primary side, and signal light is input from each of multiple user devices. As shown in Fig. 15, the monitoring system 11 according to embodiment 1-2 includes a demultiplexer 170 and a monitoring device 130. The demultiplexer 170 includes multiple input ports to which signal light from the user devices is input, a first output port that outputs a desired demultiplexed signal, and a second output port that outputs a residual demultiplexed signal.

[0060] First Configuration Example of Separation Device 170 FIG. 16 is a diagram illustrating a first configuration example of a demultiplexer 170 according to embodiment 1-2. The demultiplexer 170 according to the first configuration example includes an AWG 215 having multiple input ports. The AWG 215 receives multiple optical signals input from the input ports on the primary side of the path and outputs them from output ports corresponding to their respective wavelengths. In general, an AWG is configured with two slab waveguides and multiple arrayed waveguides that connect the two slab waveguides and have a predetermined difference in waveguide length. As a result, light input to each port of the input slab waveguide is focused onto a port of the output slab waveguide corresponding to its wavelength due to dispersion caused by a phase difference imparted by the arrayed waveguide. Therefore, when multiple user devices are connected to input ports of the AWG 215 corresponding to their desired wavelengths, the desired demultiplexed signals of all the user devices are output from a single output port. Note that the "input port of the AWG 215 corresponding to the desired wavelength" refers to an input port from which the desired wavelength is output. Of the multiple output ports of the AWG 215, the output port from which an optical signal (desired signal) of the desired demultiplexed signal wavelength is output is connected to the secondary side of the path. The remaining output ports are connected to the monitoring device 130. An isolator may be provided between the demultiplexer 170 and the monitoring device 130.

[0061] When the monitoring system 11 includes a separation device 170 according to the first configuration example, the monitoring device 130 has the same configuration and performs the same monitoring process as in the first embodiment. That is, when the monitoring device 130 has the configuration shown in Fig. 3, the monitoring device 130 may perform the monitoring process shown in Fig. 8 or a monitoring process according to a modified example thereof, when the monitoring device 130 has the configuration shown in Fig. 9, the monitoring device 130 may perform the monitoring process shown in Fig. 10 or a monitoring process according to a modified example thereof, and when the monitoring device 130 has the configuration shown in Fig. 11, the monitoring device 130 may perform the monitoring process shown in Fig. 12 or a monitoring process according to a modified example thereof.

[0062] Second Configuration Example of Separation Device 170 17 is a diagram showing a second configuration example of the demultiplexer 170 according to embodiment 1-2. The demultiplexer 170 according to the second configuration example includes a plurality of demultiplexing sections 217 and an optical multiplexer / splitter 218. The input ports of the multiple demultiplexers 217 are connected to corresponding user devices. Each demultiplexer 217 wavelength-demultiplexes the input signal into a desired demultiplexed signal for the corresponding user device and a residual demultiplexed signal. The desired demultiplexed signal is output from a first output port of the demultiplexer 217, and the residual demultiplexed signal is output from a second output port of the demultiplexer 217. Each demultiplexer 217 may have a configuration similar to that of the demultiplexer 217 shown in Figures 4 to 7, for example. The first output port of each demultiplexer 217 is connected to an input port of an optical multiplexer / demultiplexer 218. The second output port of each demultiplexer 217 is connected to a monitoring device. The output port of the optical multiplexer / demultiplexer 218 is connected to the secondary side of the path.

[0063] 17, the demultiplexer 170 includes an optical multiplexer / splitter 218 on the secondary side, thereby outputting light from one output port on the secondary side of the monitoring system 11, but this is not limiting. For example, in another embodiment, a multiplexer 216 may be provided instead of the optical multiplexer / splitter 218, and each demultiplexer 217 may be connected to an input port of the multiplexer 216 corresponding to the desired wavelength component. Furthermore, for example, if the monitoring system 11 has multiple ports on the secondary side, the demultiplexer 170 may not include the multiplexer 216.

[0064] Each second output port of the demultiplexer 170 according to the second exemplary configuration outputs the surplus demultiplexed signal of the corresponding user device. Therefore, when the monitoring system 11 includes the demultiplexer 170 according to the second exemplary configuration, the measurement unit of the monitoring device 130 can monitor the surplus demultiplexed signal of each user device without restricting the output of each user device, and determine whether or not non-compliant light exists. In other words, in this case, the monitoring device 130 does not need to include the optical multiplexer / demultiplexer 160 and the demultiplexer 217 in the configuration shown in FIG. 3. 2, when an optical multiplexer / splitter 120 is provided for each user device, the monitoring device shown in FIG. 3 may not include an optical multiplexer / splitter 160, and light from the corresponding user devices may be directly input to the multiple separators 217 of the monitoring device 130. In other words, the multiple separators 217 of the monitoring device 130 may function as the multiple separators 217 of the separator 170.

[0065] In the embodiment 1-2, the multiple light beams having the remaining wavelengths output by the demultiplexer 170 are output to the monitoring device 130 without being multiplexed. However, in other embodiments, the light beams having the remaining wavelengths of the demultiplexer 170 may be multiplexed by a multiplexer / demultiplexer or a multiplexer / splitter and output to the monitoring device 130. In this case, the monitoring device 130 may have the same configuration and perform the same monitoring process as in the embodiment 1-1. That is, when the monitoring device 130 has the configuration shown in FIG. 3, the monitoring device 130 may perform the monitoring process shown in FIG. 8 or a monitoring process according to a modification thereof. When the monitoring device 130 has the configuration shown in FIG. 9, the monitoring device 130 may perform the monitoring process shown in FIG. 10 or a monitoring process according to a modification thereof. When the monitoring device 130 has the configuration shown in FIG. 11, the monitoring device 130 may perform the monitoring process shown in FIG. 12 or a monitoring process according to a modification thereof.

[0066] First Modified Example 18 is a schematic block diagram showing a first modified example of the monitoring system 11 according to embodiment 1-2. According to the monitoring system 11 according to the first modified example, a blocking unit 150 is provided between each input port of the demultiplexer 170 and the user device. Note that the blocking unit 150 may be disposed near the demultiplexer 170 as shown in FIG. 18, or may be disposed near each user device. This allows the monitoring system 11 to select a user device and control whether or not to allow signal light to pass through.

[0067] The limiting unit 137 of the monitoring device 130 according to the first modification may output a blocking instruction to the blocking unit 150 instead of a limiting instruction to the user device, and may output an opening instruction to the blocking unit 150 instead of a restriction release instruction to the user device. This allows the monitoring device 130 to control so that unnecessary light does not flow to the secondary side of the path, as in embodiment 1-1. Furthermore, according to the first modification, even when the user device outputs an optical signal without following the instructions of the monitoring device 130, the optical signal can be reliably blocked. Furthermore, as in the third configuration example according to embodiment 1-1, when the monitoring device 130 outputs a dithering instruction and a dithering cancellation instruction, the monitoring device 130 may output the dithering instruction and the dithering cancellation instruction to the blocking unit 150. That is, upon receiving the dithering instruction, the blocking unit 150 superimposes modulation by a dithering component on the light input from the user device. This allows the monitoring system 11 to dither the light output from the user device even when the user device does not follow the instructions of the monitoring device 130.

[0068] Second Variation The monitoring system 11 according to the second modification may include a blocking unit 150 downstream of the demultiplexer 170. In this case, the monitoring device 130 executes a monitoring process similar to that of the embodiment 1-1, for example, and then outputs a blocking instruction to the blocking unit 150 downstream of the demultiplexer 170 if the strength of the residual separated signal remains above the no-signal threshold because the user device does not follow the restriction instruction.

[0069] <Embodiment 1-3> Fig. 19 is a schematic block diagram showing the configuration of a monitoring system 11 according to embodiment 1-3. In the monitoring system 11 according to embodiment 1-1, multiplexed light is input from one port on the primary side, while the monitoring system 11 according to embodiment 1-2 has multiple ports on the primary side, and signal light is input from each of multiple user devices. As shown in Fig. 19, the monitoring system 11 according to embodiment 1-3 includes an optical multiplexer / demultiplexer 120 used for multiplexing and a monitoring device 130. The optical multiplexer / demultiplexer 120 shown in Fig. 19 has multiple input ports to which signal light is input from the user devices, and two output ports.

[0070] The monitoring device 130 according to embodiment 1-3 may have the same configuration as that of embodiment 1-1. That is, when the monitoring device 130 has the configuration shown in Fig. 3, the monitoring device 130 may execute the monitoring process shown in Fig. 8 or a monitoring process according to a modification thereof, when the monitoring device 130 has the configuration shown in Fig. 9, the monitoring device 130 may execute the monitoring process shown in Fig. 10 or a monitoring process according to a modification thereof, and when the monitoring device 130 has the configuration shown in Fig. 11, the monitoring device 130 may execute the monitoring process shown in Fig. 12 or a monitoring process according to a modification thereof. If the optical multiplexer / splitter 120 outputs the light branched from each user device to the separation section 217 of the monitoring device 130 and also functions as the optical multiplexer / splitter 160 of Figure 3, the monitoring device 130 does not need to have the optical multiplexer / splitter 160 separate from the optical multiplexer / splitter 120 in the configuration shown in Figure 3.

[0071] First Modified Example Fig. 20 is a schematic block diagram showing a first modified example of the monitoring system 11 according to the first to third embodiments. According to the monitoring system 11 according to the first modified example, a blocking unit 150 is provided between each input port of the optical multiplexer / demultiplexer 120 and the user device. The blocking unit 150 may be disposed near the demultiplexer 170 as shown in Fig. 20, or may be disposed near each user device. This allows the monitoring system 11 to select a user device and control whether or not to allow signal light to pass through.

[0072] The limiting unit 137 of the monitoring device 130 according to the first modification may output a blocking instruction to the blocking unit 150 instead of a limiting instruction to the user device, and may output an opening instruction to the blocking unit 150 instead of a restriction release instruction to the user device. This allows the monitoring device 130 to control so that unnecessary light does not flow to the secondary side of the path, as in the case of the first to third embodiments. Furthermore, according to the first modification, even when the user device outputs an optical signal without following the instructions of the monitoring device 130, the optical signal can be reliably blocked. Furthermore, as in the third configuration example according to embodiment 1-1, when the monitoring device 130 outputs a dithering instruction and a dithering cancellation instruction, the monitoring device 130 may output the dithering instruction and the dithering cancellation instruction to the blocking unit 150. That is, upon receiving the dithering instruction, the blocking unit 150 superimposes modulation by a dithering component on the light input from the user device. This allows the monitoring system 11 to dither the light output from the user device even when the user device does not follow the instructions of the monitoring device 130.

[0073] Second Variation The monitoring system 11 according to the second modification may include a cutoff unit 150 downstream of the optical multiplexer / splitter 120. In this case, the monitoring device 130 executes a monitoring process similar to that of embodiment 1-1, for example, and then outputs a cutoff instruction to the cutoff unit 150 downstream of the demultiplexer 170 if the intensity of the residual separated signal remains above the no-signal threshold because the user device does not follow the restriction instruction.

[0074] <Embodiment 1-4> FIG. 21 is a schematic block diagram showing the configuration of a monitoring system 11 according to embodiments 1-4. The monitoring system 11 according to embodiments 1-4 includes two optical multiplexers / splitters 120, a plurality of separation units 217, and a monitoring device 130. As shown in FIG. 21, the optical multiplexers / splitters 120 are provided at the primary side end and the secondary side end of the monitoring system 11. The optical multiplexer / splitter 120 provided on the primary side has one input port and a plurality of output ports. The optical multiplexer / splitter 120 provided on the primary side splits light input to the input port and outputs the split light from the plurality of output ports. The optical multiplexer / splitter 120 provided on the secondary side has a plurality of input ports and one output port. The optical multiplexer / splitter 120 provided on the secondary side combines light input to the plurality of input ports and outputs the combined light from the output port.

[0075] The multiple demultiplexers 217 are provided corresponding to the user devices, respectively, and demultiplex the input light into a desired demultiplexed signal for each user device and a residual demultiplexed signal for output. An input port of the demultiplexer 217 is connected to an output port of the optical multiplexer / demultiplexer 120 on the primary side. A first output port of the demultiplexer 217 is connected to an input port of the optical multiplexer / demultiplexer 120 on the secondary side. A second output port of the demultiplexer 217 is connected to the monitoring device 130.

[0076] The monitoring device 130 according to embodiment 1-4 may have the same configuration as that of embodiment 1-1. That is, when the monitoring device 130 has the configuration shown in Fig. 3, the monitoring device 130 may execute the monitoring process shown in Fig. 8 or a monitoring process according to a modification thereof, when the monitoring device 130 has the configuration shown in Fig. 9, the monitoring device 130 may execute the monitoring process shown in Fig. 10 or a monitoring process according to a modification thereof, and when the monitoring device 130 has the configuration shown in Fig. 11, the monitoring device 130 may execute the monitoring process shown in Fig. 12 or a monitoring process according to a modification thereof. 21 is preferably at a level where coherent crosstalk, which occurs when a desired demultiplexed signal from one demultiplexer is multiplexed with a residual demultiplexed signal from another demultiplexer, can be ignored. Coherent crosstalk may be reduced by polarization multiplexing or multiplexing with a shift of at least the coherence length.

[0077] <Embodiment 2-1> The monitoring system 11 according to the above-described embodiments 1-1 to 1-4 detects, among a plurality of user devices connected to a route, a user device that outputs light of an incompatible wavelength. In contrast, the monitoring system 11 according to embodiment 2-1 detects, among a plurality of user devices connected to a route, a user device that outputs light of an incompatible intensity. The monitoring system 11 according to embodiment 2-1 includes an optical multiplexer / demultiplexer 120 and a monitoring device 130, as shown in FIG. 2 .

[0078] (First Configuration Example of Monitoring Device 130) FIG. 22 is a diagram showing a first configuration example of the monitoring device 130 according to embodiment 2-1. The monitoring device 130 according to the embodiment 2-1 includes a measurement unit 132 and a control unit 50. The control unit 50 functions as an acquisition unit 133, a storage unit 134, a range determination unit 135, a determination unit 136, and a restriction unit 137.

[0079] The measuring unit 132 measures the intensity of the multiplexed light output from the optical multiplexer / demultiplexer 120. For example, the measuring unit 132 may be realized by a combination of a photoelectric conversion element such as a PD (photodiode) or an APD (avalanche photodiode) and a circuit that measures voltage. The acquisition unit 133 acquires, from the management device, setting data indicating the wavelength and intensity of the optical signal set in the user device. The storage unit 134 stores the setting data acquired by the acquisition unit 133 and the maximum allowable value of the intensity of the multiplexed light determined by the range determination unit 135.

[0080] The range determination unit 135 determines the maximum allowable value of the intensity of the multiplexed light based on the setting data recorded in the storage unit 134. The maximum allowable value is calculated, for example, by multiplying the sum of the light intensities set for the user devices connected to the route monitored by the own device by a predetermined margin rate. For example, if the intensity set for each user device by configuration data or the like indicates the maximum light intensity to prevent damage to network equipment and the user device is required to transmit light at an intensity lower than the set value, the margin rate may be a value less than 1 (e.g., 0.8) in consideration of the safety of the network equipment. Also, if the intensity set for each user device is set to a sufficiently low intensity in consideration of the safety of the network equipment and some deviation in the intensity of light transmitted from the user device is allowed, the margin rate may be a value greater than or equal to 1 (e.g., 1.1). In this case, if the loss between the user device and the measurement unit 132 is known, the determination unit 136 may calculate the maximum allowable value by subtracting this loss. The maximum allowable value can be considered as the upper limit of the allowable range of the intensity of the multiplexed light. In another embodiment, if the intensity of the optical signal is set in advance and known, the storage unit 134 may store a predetermined maximum allowable value. If the intensity of the received light exceeds the maximum allowable value, the received multiplexed light may contain non-conforming light.

[0081] The determination unit 136 determines whether the intensity of the multiplexed light measured by the measurement unit 132 exceeds the maximum allowable value stored in the storage unit 134. The limiting unit 137 outputs an instruction related to the output of the signal light to the user equipment. Specifically, the limiting unit 137 outputs a restriction instruction to the user equipment when the user equipment is to limit the output of the signal light. The output restriction may be, for example, stopping the output or reducing the output intensity. The limiting unit 137 outputs a restriction release instruction to the user equipment when the user equipment is to release the output restriction of the signal light. The restriction release may be, for example, starting or resuming the output or increasing the output intensity. On the other hand, the instruction from the limiting unit 137 may be transmitted via communication using a predetermined carrier, or may be transmitted by multiplexing the main signal using frequency division multiplexing or time division multiplexing such as AMCC (Auxiliary Management and Control Channel), or may be transmitted via a specific communication route. Alternatively, the limiting unit 137 may issue a notification related to the output restriction to the PG or a higher-level device of the PG, and the PG or higher-level device that receives the notification may output an instruction to the user equipment.

[0082] FIG. 23 is a flowchart showing the monitoring process by the monitoring device 130 of the first configuration example according to embodiment 2-1. Upon a predetermined trigger, the acquisition unit 133 of the monitoring device 130 receives the setting data from the management device and records it in the storage unit 134. Furthermore, based on the setting data recorded in the storage unit 134, the range determination unit 135 determines the maximum allowable value from the sum of the optical signal intensities set in the user devices connected to the route monitored by the monitoring device 130, and records this in the storage unit 134. Thereafter, the management device transmits the setting data to the monitoring device 130 every time the setting data is changed. The setting data transmitted by the management device only needs to include at least a portion related to the monitoring performed by the monitoring device 130. Furthermore, if the set intensity is known or will not be changed, the management device does not need to transmit the setting data. The predetermined triggers include the start-up of the management device, the addition of the monitoring device 130, the start-up of the monitoring device 130, the connection, addition, deletion, or setting change of a user device, a request from a user device, and a setting from the management device.

[0083] The monitoring device 130 according to the embodiment 2-1 repeatedly executes the monitoring process shown in FIG. The measuring unit 132 measures the intensity of the multiplexed light input from the optical multiplexer / demultiplexer 120 (step S1). If any of the user devices has stopped outputting optical signals, the maximum allowable value is determined based on the optical signal intensity set in the user device that is outputting the optical signal. The determination unit 136 determines whether the intensity of the multiplexed light measured in step S1 exceeds the maximum allowable value stored in the storage unit 134 (step S2).

[0084] If the intensity of the multiplexed light does not exceed the maximum allowable value (step S2: NO), the monitoring device 130 determines that the multiplexed light does not contain non-compliant light whose intensity does not meet the predetermined standard, does not restrict the optical signal, and returns the process to step S1. On the other hand, if the intensity of the multiplexed light exceeds the maximum allowable value (step S2: YES), the limiting unit 137 transmits (step S3) a signal light restriction instruction to all user devices connected to the path monitored by the monitoring device 130 (if P user devices are connected to the optical multiplexer / demultiplexer 120, then P user devices). Note that it is not necessary to transmit the instruction to any of the P user devices that are stopped.

[0085] Next, the monitoring device 130 inspects the multiple user devices for output abnormalities in the following steps S5 to S9. "Output abnormality" refers to an abnormality related to the output of light with an inappropriate intensity. First, the limiting unit 137 selects one or more suspicious devices from the connected user devices (step S4), and transmits an instruction to lift the limit on the signal light to the suspicious device (step S5).

[0086] The range determination unit 135 determines a temporary maximum allowable value from the sum of the intensities of the optical signals set for the user devices that resumed output of the optical signals in step S5, based on the setting data recorded in the storage unit 134 (step S6). The temporary maximum allowable value determined here is a temporary threshold used to search for user devices that output non-compliant optical signals, and is usually different from the maximum allowable value stored in the storage unit 134 referenced in step S3. The measurement unit 132 measures the intensity of the optical signal input from the optical multiplexer / demultiplexer 120 (step S7). The signal light received at this time is an optical signal output from one or more suspected devices that have resumed outputting signal light, or an optical signal output from a user device whose suspicion has been resolved and an optical signal output from one or more suspected devices multiplexed together.

[0087] The determination unit 136 determines whether the optical signal strength measured in step S7 exceeds the temporary allowable maximum value determined in step S6 (step S8). If the optical signal strength does not exceed the temporary allowable maximum value (step S8: NO), the determination unit 136 determines that the suspected device selected in step S4 is normal and does not limit the optical signal from the suspected device. In other words, the suspicion of an output abnormality for the user device selected in step S4 is eliminated. On the other hand, if the optical signal strength exceeds the temporary allowable maximum value (step S8: YES), the determination unit 136 determines that the user device selected in step S5 has an output abnormality. If multiple (A) user devices are selected in step S4, the determination unit 136 may select one user device or less than A user devices to determine which of them has an output abnormality, and perform the process from step S5. The limiting unit 137 again transmits an instruction to limit the optical signal to the user device in which the output abnormality has been detected (step S9).

[0088] The monitoring device 130 determines whether or not there are no more suspicious devices (step S10). If there are any more suspicious devices (step S10: NO), the monitoring device 130 returns to step S4 and checks the remaining suspicious devices. On the other hand, if there are no more suspicious devices (step S10: YES), the monitoring device 130 returns to step S1.

[0089] 23, since the user device that is no longer suspect in step S8 continues to output an optical signal, the temporary maximum allowable value in step S7 may change each time the loop from step S4 to step S10 is repeated. However, other embodiments are not limited to this.

[0090] For example, the same strength may be assigned to all user devices, each user device may be designated as a suspect device, and whether the suspect device is non-compliant may be recorded based on the determination in step S8. A restriction instruction may be sent in step S9 regardless of whether the suspicion has been resolved. After it is determined in step S10 that there are no more suspicious devices, a restriction release instruction may be sent to devices recorded as non-compliant, and the process may end. In this case, the temporary maximum allowable value does not change in the loop from step S4 to step S10. In another embodiment, a restriction instruction may not be issued in step S4, a restriction instruction may be sent in place of a restriction release instruction in step S5, and a restriction release instruction may be sent in place of a restriction instruction in step S9. In another embodiment, instead of issuing a restriction instruction in step S4, a restriction instruction may be sent instead of an output instruction in step S5, and whether or not the suspected device is non-compliant may be recorded based on the judgment in step S8. Regardless of whether or not the suspicion has been resolved, a restriction release instruction may be sent instead of a restriction instruction in step S9, and if it is judged in step S10 that the suspected device has disappeared, a restriction instruction may be output to the device recorded as non-compliant in step S8, and the process may end.

[0091] Note that the measuring unit 132 of the monitoring device 130 according to the first exemplary configuration measures the intensity of the light branched from the optical multiplexer / brancher 120, but is not limited to this. For example, the measuring unit 132 may measure the intensity of the desired separated signal or the residual separated signal. In this case, the monitoring device 130 may include the optical multiplexer / brancher 120 and a plurality of separators 217 in a stage preceding the measuring unit 132, as shown in FIG. 3. In this case, the measuring unit 132 may switch, in a time-division manner, the light output from the plurality of separators 217 to be measured.

[0092] (Second Configuration Example of Monitoring Device 130) 24 is a diagram showing a second configuration example of the monitoring device 130 according to embodiment 2-1. The monitoring device 130 according to the second configuration example includes a spectrum analyzer 138 instead of the measurement unit 132 of the first configuration example. Other configurations of the monitoring device 130 according to the second configuration example are the same as those of the first configuration example. The spectrum analyzer 138 measures the distribution of wavelength components included in the received signal, i.e., the relationship between wavelength and intensity. The monitoring device 130 according to the second configuration example differs from the first configuration example in steps S1 and S2, and steps S7 and S8 shown in Fig. 23. Specifically, this is as follows.

[0093] In step S1, spectrum analyzer 138 measures the distribution of wavelength components of the signal branched from optical multiplexer / brancher 120. In step S2, determination unit 136 determines, based on the distribution of wavelength components of the signal branched from optical multiplexer / brancher 120, whether or not there is one or more wavelengths whose intensity exceeds a no-signal threshold.

[0094] In step S7, spectrum analyzer 138 measures the distribution of wavelength components of the signal branched from optical multiplexer / brancher 120. In step S8, determination unit 136 determines, based on the distribution of wavelength components of the signal branched from optical multiplexer / brancher 120, whether or not there is one or more wavelengths whose intensity exceeds a no-signal threshold.

[0095] Note that, similar to the first configuration example, the monitoring device 130 according to another embodiment may, after determining that the suspicious device has disappeared, send a restriction release instruction to the device recorded as not being non-compliant, and then terminate the process. Furthermore, the monitoring device according to another embodiment may not issue a restriction instruction in step S4, send a restriction instruction instead of a restriction release instruction in step S5, and send a restriction release instruction instead of a restriction instruction in step S9. Furthermore, the monitoring device 130 according to another embodiment may not issue a restriction instruction in step S4, send a restriction instruction instead of an output instruction in step S5, record whether the suspicious device is non-compliant based on the determination in step S8, send a restriction release instruction instead of a restriction instruction in step S9 regardless of whether the suspicion has been resolved, and, when it is determined in step S10 that the suspicious device has disappeared, output a restriction instruction to the device recorded as non-compliant in step S8, and then terminate the process.

[0096] (Third Configuration Example of Monitoring Device 130) FIG. 25 is a diagram illustrating a third exemplary configuration of the monitoring device 130 according to embodiment 2-1. The monitoring device 130 according to the third exemplary configuration further includes a dithering instruction unit 139 in addition to the components of the first exemplary configuration. Other components of the monitoring device 130 according to the third exemplary configuration are the same as those of the first exemplary configuration. The dithering instruction unit 139 outputs a dithering instruction and a dithering cancellation instruction to the user device. The dithering instruction is an instruction to modulate the optical signal with a frequency or time series pattern that differs for each user device. Hereinafter, the frequency or time series pattern that modulates the optical signal according to the dithering instruction will be referred to as a dithering component. The dithering component allows the user device that transmitted the optical signal modulated with the dithering component to be uniquely identified. On the other hand, the dithering cancellation instruction instructs the user device to stop modulating the optical signal with the dithering component.

[0097] Furthermore, the measuring unit 132 according to the third exemplary configuration has a function of extracting the intensity of the dithering component of each user device from the received intensity of the optical signal. If the dithering component is a frequency, the measuring unit 132 extracts the intensity of the frequency component. If the dithering component is a pattern, the measuring unit 132 extracts the intensity of the component according to the pattern. The measuring unit 132 according to the third exemplary configuration includes, for example, a lock-in amplifier.

[0098] FIG. 26 is a flowchart showing the monitoring process by the monitoring device 130 of the third configuration example according to embodiment 2-1. Upon receiving a predetermined trigger, the acquisition unit 133 of the monitoring device 130 receives the setting data from the management device and stores it in the storage unit 134. Thereafter, the management device transmits the setting data to the monitoring device 130 every time the setting data is changed.

[0099] The monitoring device 130 according to the third configuration example repeatedly executes the monitoring process shown in Fig. 26. The measurement unit 132 measures the intensity of the multiplexed light input from the optical multiplexer / demultiplexer 120 (step S321). The determination unit 136 determines whether the intensity of the multiplexed light measured in step S321 exceeds the maximum allowable value recorded in the storage unit 134 (step S322).

[0100] If the intensity of the multiplexed light does not exceed the maximum allowable value (step S322: NO), the monitoring device 130 determines that the multiplexed light does not contain non-compliant light, does not restrict the optical signal, and returns the process to step S321. On the other hand, if the intensity of the multiplexed light exceeds the maximum allowable value (step S322: YES), the dithering instruction unit 139 determines a different pattern for each of the user devices connected to the route monitored by the monitoring device 130, and transmits a dithering instruction for the determined pattern to each user device (step S323). An example of a modulation pattern is one in which the intensity of the optical signal is changed at a different frequency for each user device. In this case, the dithering instruction unit 139 determines the frequencies of each user device to be frequencies that are not multiples or divisors of each other. Another example of a modulation pattern is one in which the intensity or wavelength of the optical signal is changed at a different timing for each user device. In this case, the dithering instruction unit 139 determines the timings for changing the intensity for each user device to be timings that do not overlap with each other. The determining unit 136 determines the maximum allowable amplitude of the dithering component for each user device based on the magnitude of the amplitude related to the dithering (step S324). Next, the measurement unit 132 measures the intensity of the multiplexed light input from the optical multiplexer / demultiplexer 120 for a certain period of time (step S325). The measurement unit 132 measures the amplitude of each dithering component of the frequency set for each user device from the time series of the intensity of the multiplexed light for the certain period of time (step S326). Note that the measurement unit 132 may simultaneously measure the amplitude of the dithering component for each user device, or may individually select and measure each frequency or time series pattern.

[0101] Next, the determining unit 136 identifies, from among the plurality of user devices, a dithering component whose amplitude exceeds the maximum allowable amplitude determined in step S324, based on the amplitude of each dithering component measured in step S326. The limiting unit 137 transmits a signal light limiting instruction to the identified user device (step S327). This stops the output of the optical signal by the user device that outputs non-compliant light. Then, the dithering instruction unit 139 transmits a dithering cancel signal to the other user devices (step S328).

[0102] In this way, the monitoring device 130 according to the third exemplary configuration can identify a user device that outputs non-compliant light by observing the dithering component while maintaining the output of an optical signal to the user device.

[0103] Actions and Effects In this way, the monitoring device 130 according to embodiment 2-1 controls the user device to stop the optical signal from flowing by transmitting a stop signal to the user device when the intensity of the received multiplexed light exceeds the allowable range according to the signal intensity preset in the user device. This allows the monitoring device 130 to control the non-compliant light so that it does not pass through.

[0104] According to embodiment 2-1, each user device operates in accordance with the restriction instruction and restriction removal instruction from the monitoring device 130, thereby preventing non-compliant light from being transmitted. On the other hand, even if some user devices do not comply with the restriction instruction and restriction removal instruction, the monitoring device 130 can still control the other user devices to prevent non-compliant light from being transmitted. For example, if only one user device is experiencing abnormal output and only that user device does not comply, when a restriction signal is transmitted to each user device in step S4, the other user devices will stop outputting in accordance with the restriction signal, while only the user device with abnormal output will not stop outputting. Therefore, the monitoring device 130 measures the light intensity after transmitting the restriction instruction in step S4 and determines the temporary maximum allowable value based on the difference from the measured intensity, thereby determining the output of a user device with normal output. If a user device with normal output does not comply with the instruction, it can be identified even if there are multiple user devices that do not comply with the instruction. In this case, the monitoring device 130 needs to determine whether the user device is complying with the instruction by, for example, sending an acknowledgment response to the user device.

[0105] First Modified Example The monitoring system 11 according to a first modification of the embodiment 2-1 detects a user device that outputs light of an inappropriate intensity among a plurality of user devices connected to a path. Furthermore, when an optical signal passing through the path contains light of an inappropriate intensity, the monitoring system 11 according to the first modification controls the optical signal so that it is not conducted to the secondary side of the path.

[0106] 13, the monitoring system 11 according to the first modification of the embodiment 2-1 includes a blocking unit 150 at a stage subsequent to the secondary port of the optical multiplexer / brancher 120. The blocking unit 150 switches between passing and blocking the input optical signal in accordance with an instruction from the monitoring device 130.

[0107] The monitoring device 130 according to the first modification of the embodiment 2-1 performs the following processing in addition to the monitoring processing of the embodiment 2-1. The limiting unit 137 of the monitoring device 130 outputs a blocking instruction to the blocking unit 150 when the intensity of the signal branched from the optical multiplexer / brancher 120 exceeds the maximum allowable value. As a result, the blocking unit 150 blocks the optical signal output by the optical multiplexer / brancher 120. Furthermore, the limiting unit 137 of the monitoring device 130 outputs an opening instruction to the blocking unit 150 after the intensity of the signal branched from the optical multiplexer / branch 120 no longer exceeds the maximum allowable value. As a result, the blocking unit 150 conducts the optical signal output by the optical multiplexer / branch 120 to the secondary side of the path.

[0108] In this way, the monitoring device 130 according to the first modification includes the blocking unit 150, thereby reliably preventing the conduction of the optical signal even when a user device outputs an optical signal without following the instruction of the monitoring device 130. If a user device 20 that outputs light with an incompatible intensity does not follow the restriction instruction, the signal light of not only that user device 20 but also other user devices 20 will remain blocked.

[0109] Second Variation According to a second modification, the blocking unit 150 of the monitoring system 11 may be provided before the separating unit 217, as shown in Fig. 14. In this case, when the blocking unit 150 blocks the signal light, the signal light is no longer input to the monitoring device 130. Therefore, the monitoring device 130 executes a monitoring process similar to that of embodiment 2-1, for example, and then outputs a blocking instruction to the blocking unit 150 if the intensity of the signal light remains above the maximum allowable value because the user device does not follow the restriction instruction.

[0110] <Embodiment 2-2> In the monitoring system 11 according to embodiment 2-1, multiplexed light is input from one port on the primary side, while in the monitoring system 11 according to embodiment 2-2, multiple ports are provided on the primary side, and signal light is input from each of multiple user devices. As shown in Fig. 19, the monitoring system 11 according to embodiment 2-2 includes an optical multiplexer / demultiplexer 120 used for multiplexing and a monitoring device 130. The optical multiplexer / demultiplexer 120 shown in Fig. 19 includes multiple input ports to which signal light is input from the user devices, and two output ports.

[0111] The monitoring device 130 according to embodiment 2-2 may have the same configuration as that of embodiment 2-1. That is, when the monitoring device 130 has the configuration shown in Fig. 22, the monitoring device 130 may execute the monitoring process shown in Fig. 23 or a monitoring process according to a modification thereof, when the monitoring device 130 has the configuration shown in Fig. 24, the monitoring device 130 may execute the monitoring process shown in Fig. 23 or a monitoring process according to a modification thereof, and when the monitoring device 130 has the configuration shown in Fig. 25, the monitoring device 130 may execute the monitoring process shown in Fig. 26 or a monitoring process according to a modification thereof.

[0112] First Modified Example According to the monitoring system 11 of the first modification of the embodiment 2-2, as shown in Fig. 20, a blocking unit 150 is provided between each input port of the optical multiplexer / demultiplexer 120 and each user device. The blocking unit 150 may be disposed near the demultiplexer 170 as shown in Fig. 20, or may be disposed near each user device. This allows the monitoring system 11 to select a user device and control whether or not to allow signal light to pass through.

[0113] The limiting unit 137 of the monitoring device 130 according to the first modification may output a blocking instruction to the blocking unit 150 instead of a limiting instruction to the user device, and may output an opening instruction to the blocking unit 150 instead of a restriction release instruction to the user device. This allows the monitoring device 130 to control so that unnecessary light does not flow to the secondary side of the path, as in the case of the first to third embodiments. Furthermore, according to the first modification, even when the user device outputs an optical signal without following the instructions of the monitoring device 130, the optical signal can be reliably blocked. Furthermore, when the monitoring device 130 outputs a dithering instruction and a dithering cancellation instruction as in the third configuration example according to embodiment 2-1, the monitoring device 130 may output the dithering instruction and the dithering cancellation instruction to the blocking unit 150.

[0114] Second Variation The monitoring system 11 according to the second modification may include a cutoff unit 150 downstream of the optical multiplexer / splitter 120. In this case, the monitoring device 130 executes a monitoring process similar to that of embodiment 2-1, for example, and then outputs a cutoff instruction to the cutoff unit 150 downstream of the demultiplexer 170 if the intensity of the residual separated signal remains above the no-signal threshold because the user device does not follow the restriction instruction.

[0115] Third Embodiment The monitoring systems 11 according to embodiments 1-1 to 1-4 detect user devices that output light of an inappropriate wavelength. The monitoring systems 11 according to embodiments 2-1 and 2-2 detect user devices that output light of an inappropriate intensity. In contrast, the monitoring system 11 according to embodiment 3 can detect both user devices that output light of an inappropriate wavelength and user devices that output light of an inappropriate intensity.

[0116] FIG. 27 is a diagram showing the configuration of a monitoring system 11 according to a first configuration example of the third embodiment. The monitoring system 11 according to the first configuration example of the third embodiment has the configuration shown in FIG. 27. That is, the monitoring device 130 according to the first configuration example of the third embodiment includes an optical multiplexer / splitter 120 and two monitoring devices 130A and 130B. The monitoring device 130A has the same configuration as the monitoring device 130 according to the first embodiment. That is, the monitoring device 130A may have the configuration shown in FIG. 3, FIG. 9, or FIG. 11. The monitoring device 130B has the same configuration as the monitoring device 130 according to the second embodiment. That is, the monitoring device 130B may have the configuration shown in FIG. 22, FIG. 24, or FIG. 25. The monitoring devices 130A and 130B may share the control unit 50. For example, the monitoring device 130 has the configuration shown in Fig. 3, and the control unit 50 regards the values ​​measured by the measurement unit 132 shown in Fig. 3 for both the desired separation wavelength and the remaining separation wavelength as the values ​​measured by the measurement unit 132 shown in Fig. 22. This configuration is suitable, for example, when using an AWG or the like whose 3 dB band extends to a wavelength midway between adjacent wavelengths. Also, when monitoring device 130A and monitoring device 130B are each equipped with a spectrum analyzer 138, monitoring system 11 may be equipped with only one monitoring device 130 as shown in FIG.

[0117] First Operation Example of Monitoring Device 130 In the monitoring system 11 according to the third embodiment, the monitoring device 130A detects the presence or absence of light of an incompatible wavelength, and the monitoring device 130B detects light of an incompatible intensity, in a predetermined monitoring cycle. For example, the monitoring device 130A first executes the monitoring process shown in the embodiment 1-1, and after the monitoring process of the monitoring device 130A, the monitoring device 130B executes the monitoring process shown in the embodiment 2-1. Alternatively, for example, the monitoring device 130B may first execute the monitoring process shown in the embodiment 2-1, and after the monitoring process of the monitoring device 130B, the monitoring device 130A may execute the monitoring process shown in the embodiment 1-1. Second Operation Example of Monitoring Device 130 The monitoring system 11 according to the third embodiment may detect light of an inappropriate wavelength and light of an inappropriate intensity in parallel. 28 is a flowchart showing the monitoring process performed by the monitoring system 11 according to embodiment 3. In this example, the monitoring device 130A has the configuration shown in FIG. 3, and the monitoring device 130B has the configuration shown in FIG. Upon a predetermined trigger, the acquisition unit 133 of the monitoring device 130B receives the setting data from the management device and records it in the storage unit 134. Furthermore, based on the setting data recorded in the storage unit 134, the range determination unit 135 determines the maximum allowable value for each wavelength from the wavelength and intensity of the optical signal set in the user device connected to the route monitored by the monitoring device 130, and records the determined value in the storage unit 134. For example, the range determination unit 135 can determine the maximum allowable value for each wavelength by calculating, for each wavelength, the sum of the intensity of the optical signal assigned to that wavelength in the setting data. Thereafter, the management device transmits the setting data to the monitoring device 130 every time the setting data is changed.

[0118] The monitoring system 11 according to the third embodiment executes the monitoring process shown in Fig. 28 at predetermined monitoring intervals. The limiting unit 137 of the monitoring device 130A transmits a signal light limiting instruction to all user devices connected to the route monitored by the monitoring device 130 (step S211).

[0119] Next, the restriction unit 137 of the monitoring device 130A selects one of the suspected devices (step S212) and transmits an instruction to the suspected device to lift the restriction on the signal light (step S213). At this time, the monitoring device 130A notifies the monitoring device 130B of the identification information of the selected suspected device. This allows the monitoring device 130A and the monitoring device 130B to share information about the selected suspected device. Thereafter, the monitoring device 130A and the monitoring device 130B each perform the detection process for non-compliant light in parallel. In other words, the processes from step S214 to step S216 and the processes from step S217 to step S219 below are executed in parallel.

[0120] The measurement unit 132 of the monitoring device 130A measures the intensity of the residual separated signal input from the separation unit 217 corresponding to the selected user equipment (step S214). The determination unit 136 of the monitoring device 130A determines whether the intensity of the residual separated signal measured in step S214 exceeds the no-signal threshold (step S215). If the intensity of the residual separated signal does not exceed the no-signal threshold (step S215: NO), the determination unit 136 of the monitoring device 130A determines that the user equipment selected in step S212 is normal. On the other hand, if the intensity of the residual separated signal exceeds the no-signal threshold (step S215: YES), the determination unit 136 of the monitoring device 130A determines that the user equipment selected in step S212 has a wavelength abnormality. The restriction unit 137 of the monitoring device 130A stores the ID of the user equipment selected in step S212 in its internal memory (step S216).

[0121] The measurement unit 132 of the monitoring device 130B measures the intensity of the optical signal input from the optical multiplexer / demultiplexer 120 (step S217). The determination unit 136 of the monitoring device 130B determines whether the intensity of the optical signal measured in step S217 exceeds the maximum allowable value (step S218). If the intensity of the optical signal does not exceed the maximum allowable value (step S218: NO), the determination unit 136 of the monitoring device 130B determines that the suspected device selected in step S212 is normal. On the other hand, if the intensity of the optical signal exceeds the maximum allowable value (step S218: YES), the determination unit 136 of the monitoring device 130B determines that the user device selected in step S212 has an output abnormality. The restriction unit 137 of the monitoring device 130B notifies the monitoring device 130A that the user device selected in step S212 has an output abnormality. Restriction unit 137 of monitoring device 130A stores the notified user device ID in an internal memory (step S219).

[0122] Monitoring device 130A and monitoring device 130B communicate with each other and notify each other that the incompatibility detection process for the suspect device selected in step S212 has been completed. When monitoring device 130A and monitoring device 130B each determine whether the user device selected in step S152 is normal or not, restriction unit 137 of monitoring device 130A transmits a restriction instruction to the user device (step S220).

[0123] The monitoring device 130A determines whether there are no more suspicious devices (step S221). If there are any more suspicious devices (step S221: NO), the monitoring device 130A returns the process to step S212 and inspects the remaining suspicious devices. On the other hand, if there are no more suspicious devices, the monitoring device 130A transmits a restriction release instruction to user devices other than the user devices stored in step S216 and step S219 (step S222), and ends the process.

[0124] The processing of the monitoring system 11 is not limited to the monitoring processing shown in Fig. 28. For example, if the configurations of the monitoring devices 130A and 130B are different, for example, if the monitoring device 130 is equipped with a spectrum analyzer, processing based on the distribution of wavelength components is performed as shown in Fig. 10, and if the monitoring device 130 is equipped with a dithering instruction unit 139, detection of non-compliant light is performed based on the dithering component as shown in Fig. 12. Furthermore, in the above-described monitoring processing, the monitoring device 130A transmits instructions to the user device, but this is not limiting, and the monitoring device 130B may transmit instructions instead.

[0125] In another embodiment, no restriction instruction is issued in step S211, and instead of issuing a restriction release instruction in step S213, a restriction instruction is sent only to the selected suspect device, and in step S215, if the change in the measured intensity before and after sending the restriction instruction exceeds the no-signal threshold, it is determined that the light is non-compliant, and in step S218, if the change in the measured intensity before and after sending the restriction instruction exceeds the maximum allowable value, it is determined that the light is non-compliant.

[0126] First Modified Example The monitoring system 11 according to the first modification of the third embodiment detects a user device that outputs non-compliant light among a plurality of user devices connected to a path. Furthermore, when the non-compliant light is included in the optical signal passing through the path, the monitoring system 11 according to the first modification controls the optical signal so that it is not conducted to the secondary side of the path.

[0127] 13, a monitoring system 11 according to a first modification of the third embodiment includes a blocking unit 150 at a stage subsequent to the secondary port of the optical multiplexer / brancher 120. The blocking unit 150 switches between passing and blocking the input optical signal in accordance with an instruction from the monitoring device 130.

[0128] The monitoring device 130 according to the first modification of the third embodiment performs the following processing in addition to the monitoring processing of the third embodiment. The limiting unit 137 of the monitoring device 130A outputs a blocking instruction to the blocking unit 150 when the intensity of the residual separated signal separated by the separating unit 217 exceeds the no-signal threshold. Furthermore, the limiting unit 137 of the monitoring device 130B outputs a blocking instruction to the blocking unit 150 when the intensity of the signal branched from the optical multiplexer / brancher 120 exceeds the maximum allowable value. As a result, the blocking unit 150 blocks the optical signal output by the optical multiplexer / brancher 120. Furthermore, after the strength of the residual separated signal no longer exceeds the no-signal threshold and the signal strength no longer exceeds the maximum allowable value, the limiting unit 137 of the monitoring device 130 outputs an open instruction to the blocking unit 150. As a result, the blocking unit 150 conducts the optical signal output by the optical multiplexer / brancher 120 to the secondary side of the path.

[0129] In this way, the monitoring device 130 according to the first modification includes the blocking unit 150, thereby reliably preventing the conduction of the optical signal even when a user device outputs an optical signal without following the instruction of the monitoring device 130. If a user device 20 that outputs light with an incompatible intensity does not follow the restriction instruction, the signal light of not only that user device 20 but also other user devices 20 will remain blocked.

[0130] Second Variation According to a second modification, the blocking unit 150 of the monitoring system 11 may be provided before the separating unit 217, as shown in Fig. 14. In this case, when the blocking unit 150 blocks the signal light, the signal light is no longer input to the monitoring device 130. Therefore, the monitoring device 130 performs a monitoring process similar to that of the third embodiment, for example, and then outputs a blocking instruction to the blocking unit 150 if the intensity of the residual separated signal exceeds the no-signal threshold or the intensity of the signal light remains above the maximum allowable value because the user device does not follow the restriction instruction.

[0131] Fourth Embodiment In the fourth embodiment, a light distribution system 10 including a monitoring system 11 will be described. The optical distribution system 10 is a system that outputs a desired signal from among input optical signals and distributes it to a destination. The optical distribution system 10 is used, for example, as a component of a PG (Photonic Gateway). The optical distribution system 10 used in a PG will be described below.

[0132] One or more user devices 20, transmission paths, or other networks are connected to the PG. The PG or a higher-level device of the PG according to the seventh embodiment sets the wavelength and intensity used for communication for each user device. The higher-level device of the PG is a device that controls a network that includes the PG as a component. In other words, the PG or the higher-level device of the PG is an example of a management device. Note that the PG or higher-level device according to other embodiments may set only the wavelength for the user device 20, but not the intensity. When the intensity is not set, the user device 20 outputs an optical signal within a predetermined intensity range. Each user device 20 under the control of the PG transmits an optical signal according to the set wavelength and intensity. The optical signal input from each user device 20, transmission path, or other network is transmitted by the PG to the appropriate destination user device 20, transmission path, or other network.

[0133] <Configuration of the optical distribution system> FIG. 29 is a schematic diagram illustrating the configuration of a light distribution system according to the fourth embodiment. The optical distribution system 10 includes an optical multiplexer / demultiplexer 110, a monitoring system 11, and an optical distribution device 140. The optical distribution device 140 has N ports on the primary side and M ports on the secondary side. One optical multiplexer / demultiplexer 110 and one monitoring system 11 are provided for each primary side port of the optical distribution device 140. The monitoring system 11 shown in FIG. 29 may have the configuration of any of the above-mentioned embodiments. However, if the monitoring system has multiple input ports corresponding to user devices as shown in FIG. 15 or FIG. 19, the optical multiplexer / demultiplexer 110 may not be provided. The optical distribution system shown in FIG. 29 is an example of a transparent network. In the fourth embodiment, a case where the monitoring system 11 is applied to an optical distribution system will be described. However, in other embodiments, the monitoring system 11 may monitor another transparent network.

[0134] The optical multiplexer / divider 110 has P ports on the primary side and at least one port on the secondary side. A user device 20 is connected to each port on the primary side of the optical multiplexer / demultiplexer 110. When a transmission line or another network is connected, the device transmitting to the port corresponds to the user device. In other words, the optical distribution system 10 is configured to be connectable to P×N user devices 20. The number P of ports on the primary side of the optical multiplexer / divider 110 may be different for each of the N optical multiplexers / dividers 110. A primary side port of the monitoring system 11 is connected to a secondary side port of the optical multiplexer / divider 110 directly or via a transmission path. A primary side port of the optical distribution device 140 is connected to a secondary side port of the monitoring system 11. That is, in the fourth embodiment, the optical multiplexer / splitter 110 and the optical multiplexer / splitter 120 multiplex P input optical signals, and branch the multiplexed signal into two optical signals at a predetermined branching ratio and output the two optical signals.

[0135] The optical distribution device 140 distributes an optical signal input to a port on the primary side to a port corresponding to the destination of the optical signal. Because a typical switch does not have a configuration for connecting ports on the same side, the optical distribution device 140 may be provided with a return transmission path connecting two different ports on the same side, enabling transmission between user devices connected to the same side of the switch. That is, when port A and port B on the same side of the switch are connected by a return transmission path, and an optical signal is transmitted from port C on the opposite side to port D, the optical distribution device 140 controls the connection between port A and port C and port B and port D, thereby transmitting the optical signal from port C on the same side to port D. The optical distribution device 140 may also be provided with a special switch capable of connecting ports on the same side.

[0136] Other Embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some processes may be executed in parallel. The monitoring device 130 according to the above-described embodiment may be configured by a single computer, or the configuration of the monitoring device 130 may be distributed across multiple computers, and the multiple computers may function as the monitoring device 130 by working together. Furthermore, although the monitoring device 130 according to the above-described embodiment is provided in the optical distribution system 10, this is not limiting. For example, the monitoring device 130 may monitor a communication path other than that of the optical distribution system 10. Furthermore, for example, in another embodiment, a combination of the monitoring device 130 and the blocking unit 150 may monitor a communication path other than that of the optical distribution system 10.

[0137] <Computer Configuration> FIG. 30 is a schematic block diagram showing the configuration of a control unit 50 according to at least one embodiment. The control unit 50 includes a processor 51 , a main memory 53 , a storage 55 , and an interface 57 . The control unit 50 described above may be implemented in a computer. In this case, the operation of each of the processing units described above is stored in the storage 55 in the form of a program. The processor 51 reads the program from the storage 55, loads it into the main memory 53, and executes the above-mentioned processing in accordance with the program. The processor 51 also allocates storage areas in the main memory 53 corresponding to each of the storage units described above in accordance with the program. Examples of the processor 51 include a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and a microprocessor.

[0138] The program may be for realizing some of the functions to be performed by the control unit 50. For example, the program may be combined with other programs already stored in storage or implemented in other devices to perform the functions. In other embodiments, the control unit 50 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor 51 may be realized by the integrated circuit. Such an integrated circuit is also included as an example of a processor.

[0139] Examples of storage 55 include a magnetic disk, a magneto-optical disk, an optical disk, and a semiconductor memory. Storage 55 may be an internal medium directly connected to the bus, or an external medium connected to control unit 50 via interface 57 or a communication line. In addition, when this program is distributed to control unit 50 via a communication line, control unit 50 that has received the program may load the program into main memory 53 and execute the above-mentioned processing. In at least one embodiment, storage 55 is a non-transitory tangible storage medium.

[0140] The program may also be a program for realizing part of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-described functions in combination with another program already stored in storage 55. [Explanation of symbols]

[0141] 10...Optical distribution system 11...Monitoring system 110...Optical multiplexer / splitter 120...Optical multiplexer / splitter 130...Monitoring device 132...Measurement unit 133...Acquisition unit 134...Memory unit 135...Range determination unit 136...Determination unit 137...Limitation unit 138...Spectrum analyzer 139...Dithering instruction unit 140...Optical distribution device 150...Blocking unit 160...Optical multiplexer / splitter 170...Demultiplexer 217...Demultiplexer 20...User device 50...Control unit 51...Processor 53...Main memory 55...Storage 57...Interface

Claims

1. A monitoring device that monitors paths through which light output from a plurality of devices flows, a determination unit that determines whether the light flowing through the path includes non-compliant light outside a range of wavelengths assigned to a specific device among the plurality of devices based on a sum of intensities of wavelengths other than the assigned wavelengths; a restriction unit that controls the light so that the light does not flow through the path when non-conforming light is included in the light; A monitoring device comprising:

2. the restriction unit controls the light from some of the plurality of devices to not flow and the light from other devices to flow, The monitoring device according to claim 1 , wherein the determination unit identifies the device that outputs non-compliant light based on the intensity of the non-compliant light when control is performed so that light from some of the devices does not flow and light from other devices flows.

3. A monitoring device for monitoring paths through which light output from multiple devices flows, a determination unit that determines whether the light flowing through the path includes non-compliant light that is outside a wavelength range assigned to a specific device among the plurality of devices; a restriction unit that controls the light so that the light does not flow through the path when non-conforming light is included in the light, The restriction unit individually outputs an instruction to restrict the output of light or an instruction to lift the restriction on the output of light to a device among the plurality of devices that is to be determined by the determination unit as to whether or not there is non-compliant light. Monitoring equipment.

4. A monitoring device for monitoring paths along which light output from multiple devices flows, a determination unit that determines whether the light flowing through the path includes non-compliant light that is outside a wavelength range assigned to a specific device among the plurality of devices; a restriction unit that controls the light so that the light does not flow through the path when non-conforming light is included in the light; a modulation instruction unit that outputs modulation instructions to the plurality of devices to modulate the light in different patterns; Equipped with the determination unit identifies a device that outputs non-compliant light based on the intensity of each signal component for each pattern separated from the light; The restriction unit controls the flow of light from a device that outputs non-compliant light among the plurality of devices. Monitoring equipment.

5. a blocking unit configured to be able to switch between passing and blocking the light is provided on the path, and the restriction unit outputs an instruction to block the light or an instruction to pass the light to the blocking unit corresponding to a device that is to be determined by the determination unit to have the non-compliant light among the plurality of devices. The monitoring device according to any one of claims 1 to 4.

6. determining whether or not light output from a plurality of devices flowing along a monitored route includes non-compliant light outside a wavelength range assigned to a specific device among the plurality of devices based on a sum of intensities of wavelengths other than the assigned wavelengths; a step of controlling the light so that the light does not flow along the path when the light includes non-conforming light; A monitoring method comprising:

7. The monitoring device according to claim 3; a plurality of devices connected to the path and limiting the output of the light based on the limiting instruction; A monitoring system comprising:

8. A path through which light output from multiple devices flows; A monitoring device according to any one of claims 1 to 5 that monitors the route; an optical distribution device that distributes the light flowing through the path to a port corresponding to the destination of the light and outputs the light; A communication system comprising:

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