Optical switch control method

Abstract

The present disclosure is a controller that controls an optical switch which switches a path of an optical signal of a terminal, wherein, prior to switching of the path, the controller causes the terminal to extinguish light.

Description

Optical switch control method

[0001] The present disclosure relates to wavelength path services and fiber path services using optical nodes configured with optical switches.

[0002] The All Photonic Network (APN) has been proposed (see, for example, Non-Patent Document 1). Since the APN also incorporates access areas, the input strength for each path differs due to the near-far problem caused by the difference in distance between the terminal and the in-office equipment. Furthermore, the fiber path service described in Non-Patent Document 1 accommodates Distributed Acoustic Sensing (DAS) signals with high peak strength and Quantum Key Distribution (QKD) signals with weak power in the same optical switch.

[0003] However, because conventional optical switches are designed to accommodate signals with similar strength and allowable leakage, when they are applied to networks that accommodate signals with different strengths and allowable leakage, there is a possibility that inter-path crosstalk will exceed the allowable range of the path in paths transmitting weak signals. Here, crosstalk often refers to static crosstalk, which is crosstalk that constantly leaks into paths other than the desired path after route setting. In addition to static crosstalk, there is also dynamic crosstalk, which temporarily leaks into paths other than the desired path when switching routes. Hereinafter, when simply referred to as "crosstalk," static crosstalk is meant.

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

[0005] The present disclosure aims to make available an optical switch whose dynamic crosstalk value exceeds the tolerance range of the path.

[0006] The present disclosure remotely controls a terminal to turn off the light before changing the setting of an optical switching device such as an optical switch, and turns on the light after changing the setting.

[0007] The controller of the present disclosure controls an optical switch that switches the path of an optical signal of a terminal, and causes the terminal to turn off the optical signal before the path of the optical switch is switched.

[0008] In the path switching method of the present disclosure, a controller of an optical switch that switches the path of an optical signal from a terminal causes the terminal to turn off the light before switching the path of the optical switch.

[0009] The controller of the present disclosure may cause the terminal to emit light after the optical switch switches the path.

[0010] The extinction or the path switching may be detected by a response. For example, the controller of the present disclosure detects a response of extinction or extinction completion from the terminal and switches the optical switch. In the case of the extinction response, the optical switch is switched after a time from the response to the extinction completion.

[0011] For example, the controller of the present disclosure detects a response from the optical switch indicating switching or completion of switching and causes the terminal to emit light. In the case of a response to switching, the controller switches the optical switch after a time period from the response to the completion of switching.

[0012] The network system of the present disclosure includes a controller of the present disclosure and an optical switch configured to switch paths of optical signals transmitted and received by the terminals under control of the controller, wherein the optical switch may have a dynamic crosstalk value that exceeds a tolerance range set for the paths of the optical signals.

[0013] The above disclosures can be combined as much as possible.

[0014] According to the present disclosure, an optical switch can be used in which the dynamic crosstalk value exceeds the allowable range of the path.

[0015] 1 shows an example of an APN configuration. 2 shows an example of dynamic crosstalk in an optical switch. 3 shows an example of dynamic crosstalk in an optical switch. 4 shows an example of a system configuration of the present disclosure. 5 shows an example of a path switching method. 6 shows an example of a system configuration of the present disclosure. 7 shows an example of a path switching method. 8 shows an example of a system configuration of the present disclosure. 9 shows an example of a path switching method. 10 shows an example of a system configuration of the present disclosure. 11 shows an example of a path switching method. 12 shows an example of a system configuration of the present disclosure. 13 shows an example of a path switching method.

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0017] (Configuration of Network System) Fig. 1 shows an example of the configuration of a network system. The network system of the present disclosure is an All Photonic Network (APN) that includes an APN gateway (hereinafter abbreviated as "APN-G") 92, an APN exchange (hereinafter abbreviated as "APN-I") 93, and a controller 91, which function as in-station devices. The APN includes, as in-home devices, an APN transceiver (APN-T), a terminal 83 equipped with an APN-T, and other terminals and termination devices 94. However, a configuration that does not include an APN-I may also be adopted.

[0018] The APN-G92 sets routes connecting the terminals 83 and termination devices 94 that send and receive the fiber path signals, which are main signals, and the wavelength path signals, to the opposing devices, and transmits the wavelength path signals, wavelength multiplexed signals, and fiber path signals to the opposing devices by returning them within the APN-G92 or via the APN-I93 or another APN-G92. The APN-G92 sets routes connecting the terminals 83 and termination devices 94 that send and receive control signals to the controller 91, and terminates control signals from the terminals 83 and termination devices 94 within the APN-G92 or transmits them directly to the controller 91, and terminates control signals from the controller 91 within the APN-G92 or transmits them directly to the terminals 83 and termination devices 94. For example, in the configuration of FIG. 1, if the controller 91 and the terminals 83 and termination devices 94 send and receive control signals directly, the APN-G92 only forwards them without sending or receiving them.

[0019] For transmission and reception, for example, an FXC (Fiber cross connect) 71, which is an optical switch that distributes optical path routes as optical signals, a WSS (Wavelength Selective Switch) 72 that multiplexes / demultiplexes optical signals of wavelength paths and switches their routes, an optical amplifier 73, a return unit 74, an AWG (Arrayed Wavelength Grating) that multiplexes / demultiplexes optical signals of wavelength paths, etc. can be used. The AWG can be used as an optical multiplexer (MUX) and an optical demultiplexer (DEMUX), or as part thereof. The AWG and WSS 72 function as a "multiplexer," a "demultiplexer," and a "multiplexer / demultiplexer." In this application, attention is focused on the multiplexing function of a multiplexer and a multiplexer / demultiplexer. For this reason, the terms "multiplexer" or "multiplexer or multiplexer / demultiplexer" will be used to represent "multiplexer," "demultiplexer," and "multiplexer / demultiplexer." The APN-G92 functions as an "optical switch."

[0020] Hereinafter, the functional unit that switches paths in the APN-G 92 will be referred to as an “optical switching device” or “optical switch.” In the following embodiment, the terminal 83 and the termination device 94 have the function of transmitting and receiving main signals, and the terminal 83, the termination device 94, and the controller 91 have the function of transmitting and receiving control signals.

[0021] In the following embodiment, an example is shown in which the terminal 83 is the target of quenching, but the target of quenching is not limited to the terminal 83. For example, if the control signal does not affect the main signal, the main signal of the terminal 83 and the terminating device 94 may be quenched. Also, if the control signal affects the main signal, the control signal of the terminal 83, the terminating device 94, and the controller 91 may be quenched.

[0022] In this disclosure, the term "optical switch" includes not only FXC, which corresponds to core multiplexing, but also WSS, since similar issues exist in WDM (wavelength division multiplexing)-related WSS. Also, in this disclosure, the term "optical switch" includes optical switches and WSSs that switch between multiple cores in a core that performs SDM (spatial division multiplexing) and may be used in an APN.

[0023] (Example of Dynamic Crosstalk Occurrence) An example of dynamic crosstalk in an optical switch is shown with reference to Figure 2. Dynamic crosstalk is leakage that occurs when paths are switched between connection terminals of an optical switch, i.e., when the connection of the connection terminals is changed. The change in connection between the connection terminals of an optical switch is caused by path switching between the connection terminals.

[0024] Examples of leakage due to dynamic crosstalk include the following: (i) For example, leakage occurring when a connection between connection terminals is changed from a connection terminal that is the target of connection change to a connection terminal other than the connection terminal that is the target of connection change. In other words, leakage occurring when a path that connects and constitutes the connection terminal that is the target of path switching is switched to a path that is not the target of path switching and that connects and constitutes a connection terminal other than the connection terminal that is the target of path switching. (ii) For example, leakage occurring when a connection between connection terminals is changed from a connection terminal other than the connection terminal that is the target of connection change to a connection terminal that is the target of connection change. In other words, leakage occurring when a path that is not the target of path switching and that connects and constitutes a connection terminal other than the connection terminal that is the target of path switching is switched to a path that connects and constitutes a connection terminal that is the target of path switching. Note that connection terminals are also called "terminals" or "ports," and paths are also called "paths."

[0025] This embodiment shows a 5x5 schematic diagram (excerpted from https: / / www.fiberlabs.co.jp / tech-explan / about-switch / ) of a MEMS optical switch, which is an optical switch that uses micro-machined micromirrors. This switch switches paths by collimating light emitted from input and output optical fibers Fi1, Fi2, Fi3, Fi4, and Fi5 using lenses, reflecting the light off two MEMS mirrors M1 and M2, which can change the angle, and making the light incident on the target input and output optical fibers Fo1, Fo2, Fo3, Fo4, and Fo5.

[0026] The thick lines indicate the selected paths. The free-space optical system includes M1 and M2 that couple (connect) input and output light from the fiber to mirrors with negligible diffusion. M1 and M2 are mirror groups with mirrors corresponding to each fiber. Each mirror of M1 couples (connects) the input and output of the corresponding fiber to a predetermined mirror of M2, and each mirror of M2 couples (connects) the input and output of the corresponding fiber to a predetermined mirror of M1. The input and output fibers may be connection terminals (ports) that couple (connect) the fibers.

[0027] 2(b), when transitioning from a connection state to the output optical fiber Fo5 shown in Fig. 2(a) to a connection state to the output optical fiber Fo1 shown in Fig. 2(b), light from the MEMS mirror M1 is reflected by reflection points P2, P3, P4, etc. that constitute the mirror group of the MEMS mirror M2 on the trajectory scanned by the light beam from the fiber, and light leaks to the output optical fibers Fo2, Fo3, Fo4 that are not the connection targets. This is dynamic crosstalk.

[0028] Static crosstalk is mainly caused by the spread of signal light at the coupling point and the distance between coupling points in the coupling system from the free-space optics to the fiber where crosstalk occurs, the spread of signal light at the reflection point and the distance between reflection points, and the spread of signal light due to diffraction and the distance between diffraction points. For example, it is the sum of at least one of the following: (i) Persistent leakage into undesired mirrors near the reflection points due to beam spread at the MEMS mirror M1 and the MEMS mirror M2. For example, in the case of the MEMS mirror M2, if the desired mirror is P2, the spread of the beam incident on P2 causes the beam skirt to overlap with undesired mirrors P1 and P3, resulting in persistent leakage. (ii) Leakage into undesired fibers at the coupling point (or input point) in the coupling system from the free-space system to the fiber. For example, when the desired fiber is Fo2, the beam incident on Fo2 expands and the beam base overlaps with undesired fibers Fo1 and Fo3, resulting in constant leakage for each path.

[0029] When calculating the sum of leakage, if the leakage due to crosstalk is deemed sufficiently small, the leakage of leakage can be ignored. For example, if the leakage is at -10 dB crosstalk, the leakage of leakage will be smaller than the crosstalk of -20 dB relative to the initial input, and can therefore be ignored. Suppose the leakage source path is the route of input / output fiber Fi5, P1 of MS mirror M2, and input / output fiber Fo5, the leakage destination path is the route of input / output fiber Fi3, P3 of MS mirror M2, and Fo3, and there is an intermediate route of input / output fiber Fi4, P2 of MS mirror M2, and Fo4. In this case, the leakage of leakage is the leakage from the leakage source path P1 to the intermediate path P2, and the leakage from the coupling system of the intermediate path Fo4 to the coupling system of the leakage destination Fo3. In this specification, the estimated values ​​are first-order approximations that mainly take into account only leakage, and second-order approximations that include leakage of leakage and the like are not performed.

[0030] 3, an example of dynamic crosstalk in the optical switch 82 is shown. The optical switch 82 is a small optical switch, for example, an optical switch (unit switch, unit switching device) configured with a 2×2 switch. ２The optical crossbar (hereinafter sometimes abbreviated as XB) switch is a 4x4 optical crossbar (XB) switch in which multiple switches are combined. XB switches are used to represent combinations of switches such as series or parallel degenerate XB switches and Clos switches. In this example, the thermo-optic effect is used to change the path length difference between the multiple paths that make up the unit switches that make up the optical switch 82, and a schematic diagram of a 4x4 optical crossbar (XB) switch is shown in which Mach-Zehnder switches (MZ) are cascaded together to serve as unit switches that switch the output route. The circle in the diagram represents one MZ, the dotted lines represent selectable paths between the MZs, and the thick lines represent the selected path.

[0031] When transitioning from the connection state from XB switch X11 to X44 shown in Figure 3(a) to the connection state from XB switch X11 to X14 shown in Figure 3(b), depending on the switching order of the unit switches, light leaks to output ports P2 and P3 as the paths of XB switches X11, X22, and X33 are switched. This is dynamic crosstalk. Note that static crosstalk can be approximated by the sum of crosstalk between unit switches constituting a certain path and unit switches constituting other paths.

[0032] If both paths share the same unit switch but do not share the path connecting the unit switches, the crosstalk from the shared unit switch itself will be the main crosstalk. When one of the unit switches constituting one path is switched, if the signal is directly input to one of the unit switches constituting the other path, the crosstalk will be the crosstalk of the unit switch itself plus the crosstalk of one stage of unit switch. When one of the unit switches constituting one path is switched, if the signal is directly input to a unit switch that directly inputs to one of the unit switches constituting the other path, the crosstalk will be the crosstalk of the unit switch itself plus the crosstalk of two stages of unit switch. If the display is linear, the crosstalk will be the crosstalk multiplied by each other, and if the display is logarithmic, the crosstalk will be added together.

[0033] Here, the number of stages is the number of unit switches constituting the path connecting the unit switches constituting each path involved in crosstalk, and is referred to as the number of hops in this application. That is, the number of hops is the number of unit switches included in the path connecting the unit switches that are passed through by switching the unit switch constituting one path before inputting to the unit switch constituting the other path, when a larger optical switch is constituted by connecting multiple switches, for example, multiple unit switches in a hierarchical structure or the like. For example, if the number of hops between adjacent unit switches is 1, the number of hops becomes 2 when one unit switch is sandwiched between the paths.

[0034] If the unit switch is a 2x2 switch and the crosstalk between paths within the unit switch is X dB, the crosstalk to paths not connected by the route is 2X dB for one hop, 3X dB for two hops, and (n+1)X dB for n hops. If crosstalk other than that at the unit switch can be ignored, the crosstalk to paths formed by a given route is the sum of the crosstalk of the unit switches that make up the route. Therefore, a given distant route is determined not by the number of hops of one unit switch that makes up the route, but by the number of hops of all unit switches that make up the route. If the crosstalk of the unit switch is sufficiently small, the loss within the optical switch is sufficiently small, and there are multiple unit switches with similar hop counts, the crosstalk can be approximated by the sum of the crosstalk of the unit switches with that number of hops. Note that with a hop count of 0, multiple paths do not share routes between unit switches, so there is only one unit switch with a hop count of 0.

[0035] First Embodiment FIG. 4 illustrates an example system configuration of the present disclosure. The terminal 83, which represents the termination device 94 and the terminal 83, is a terminal in a network equipped with an optical switch such as an APN, and includes a light-emitting unit 31 that generates an optical signal. The terminal 83 may also be an APN-T that functions as an in-home device. This also applies to the following examples. The light-emitting unit 31 may employ any known means for emitting and extinguishing a predetermined light under control. For example, the light-emitting unit 31 of the terminal 83 may not emit light itself, but may be a functional unit that receives light from another source and controls the output toward the network, as long as the output is extinguished under control. This also applies to the following examples. The controller 81 controls the optical switch 82. While the figure only illustrates the direction in which an optical signal is output from the terminal 83 to the optical switch 82, an optical signal may also be provided in the direction in which it is input from the optical switch 82 to the terminal 83. This also applies to the following embodiments.

[0036] The optical switch 82 switches the path under the control of the controller 81, and switches the path of the optical signal transmitted and received by the terminal 83. The optical switch 82 is an optical switch provided in an APN such as the FXC 71, and any device that can set a path for an optical signal and switch the route of the set path can be used.

[0037] The system disclosed herein includes a controller 81 that causes the light-emitting unit 31 to turn off light when the optical switch 82 switches paths. In the path switching method disclosed herein, the controller 81 causes the light-emitting unit 31 to stop emitting light before the optical switch 82 switches paths. Then, the controller 81 causes the light-emitting unit 31 to emit light after the optical switch 82 switches paths.

[0038] The control device 81 has the following functions and can use a controller 91 provided in the APN: (i) understanding the path switching status of the optical switch 82; (ii) switching control to the optical switch 82; (iii) understanding the light emitting status of the light emitting unit 31; and (iv) controlling the light emitting unit 31 to emit or extinguish light.

[0039] FIG. 5 shows an example of a path switching method. When switching the path of the optical switch 82, the controller 81 controls the terminal 83 to turn off, thereby turning off the light-emitting unit 31 (S11). The timing of this control is before the path switching that changes the setting of the optical switch 82, i.e., before the connection of the connection terminal (port) is changed. The controller 81 determines whether the light-emitting unit 31 is turned off (S12). The controller 81 repeats step S12 until the light-emitting unit 31 is turned off. Alternatively, steps S11 and S12 are repeated. When the light-emitting unit 31 is turned off (Yes in S12), the controller 81 changes the setting of the optical switch 82, i.e., changes the connection of the connection terminal (port) (S13). The controller 81 determines whether the setting change of the optical switch 82 is complete (S14). The controller 81 repeats step S14 until the setting change of the optical switch 82 is complete. When the setting change of the optical switch 82 is completed (Yes in S14), the light emission control of the light emitting unit 31 is transmitted to the terminal 83. Note that although "light off?" is displayed, it may be changed to "output reduction?" to an optical output that keeps leakage due to dynamic crosstalk within an acceptable range. This also applies to the following examples.

[0040] The present disclosure extinguishes the light-emitting unit 31 involved in leakage during a setting change of the optical switch 82, thereby preventing dynamic crosstalk, which is crosstalk in which an optical signal leaks from the light-emitting unit in the optical switch 82 to an undesired light-receiving unit or the like. Therefore, the optical switch 82 may have a dynamic crosstalk value that exceeds the allowable range set for the optical signal path. Therefore, according to the present disclosure, even if the dynamic crosstalk value of an optical switch 82 exceeds the allowable range for the path, it can be reduced to below the allowable leakage for the path.

[0041] After confirming in step S12 that the light-emitting unit 31 has turned off, the controller 81 may switch the path (control the port switching) of the optical switch 82. In this case, the controller 81 may control the light emission of the light-emitting unit 31 after confirming that the path switching of the optical switch 82 has been completed.

[0042] Here, the change in the setting of the optical switch after extinction (change in the connection of the connection terminal (port), route switching) is the change in the setting of the optical switch after extinction is complete (change in the connection of the connection terminal (port), route switching), and light emission after the change in the setting of the optical switch (change in the connection terminal (port), route switching) is after the change in the setting of the optical switch (change in the connection terminal (port), route switching) is completed. This also applies to the following embodiments. An example of a method for determining whether the light-emitting unit 31 is extinguished in step S12 is shown below.

[0043] Second Embodiment An example of a system configuration of this embodiment is shown in Fig. 6. A terminal 83 includes a response unit 32 that, when the light-emitting unit 31 has been turned off, transmits a response to the controller 81 indicating that the light-emitting unit 31 has been turned off.

[0044] The response indicating the completion of extinction may be sent before the completion of extinction, as long as the time from reception of the response to the completion of extinction can be determined. In this case, the controller 81 may start the path switching control after the time elapses from reception of the response to the completion of extinction. This is the same for the light emission response and the switching response. This also applies to other embodiments of the present application to which these can be applied.

[0045] FIG. 7 shows an example of a path switching method. In this embodiment, step S12 includes step S21. In step S21, the controller 81 confirms the extinction of the light-emitting unit 31 by receiving a response indicating the completion of extinction from the terminal 83. In step S13, after confirming the extinction by a response from a response unit included in the terminal 83 to the controller 91, the controller 81 switches (switches) the path of the optical switch 82, confirms the completion of the path switching, and then controls the terminal 83 to emit light. Although not shown in FIG. 6, the optical switch 82 may also include a response unit, and the completion of the switching may be confirmed by a response from the response unit to the controller 91. In this case, step S14 in FIG. 7 becomes "Switching completion received?", similar to step S21. As with the extinction detection in the third embodiment, the switching may be detected by the optical switch 82. In that case, step S14 becomes "Switching detected?"

[0046] If the response is from a terminal, the optical switch may be switched upon detecting a response from the terminal of extinction or extinction completion. In the case of an extinction response, the optical switch is switched after a time has elapsed since the response until extinction completion. If the response is from an optical switch, the optical switch may be caused to emit light upon detecting a switching or switching completion response from the optical switch. In the case of a switching response, the optical switch is switched after a time has elapsed since the response until switching completion. These are also true for other embodiments of the present application to which they can be applied.

[0047] Here, the confirmation of the response may be made after a predetermined time has elapsed from the time of control to the time of completion. This is preferable in a configuration in which the main signal and the control signal described later are switched to the same path by the same optical switch 82, in which the controller is provided in the controller 91 or the APN-G 92 and not in the terminal 83, in which the main signal path from the terminal 83 is connected to the controller 81 by path switching, in which the controller 81 controls the terminal 83, and in which the path is connected to a device such as the terminal 83 opposite the terminal 83 by path switching and then light is emitted, because the control path from the controller 81 to the terminal 83 has already been cut off.

[0048] Third Embodiment An example of the system configuration of this embodiment is shown in Fig. 8. This embodiment includes a detector 33 that detects light from a light emitter 31.

[0049] The detector 33 may be located anywhere in the optical switch 82, for example, between the output of the light emitter 31 in the terminal 83 and the output of the optical switch 82, as long as it can determine whether the light is emitted or not. For example, if the detector 33 is located in the terminal 83, the detector 33 may detect the output intensity from the light emitter 31 by detecting a portion of the light branched off along an internal path from the light emitter to the optical switch 82. The detector 33 may also detect light along a path from the terminal 83 to the optical switch, for example, light other than the path from the terminal 83 to the optical switch 82 (e.g., light from one output of the light emitter from which light is output from multiple outputs). For example, the detector 33 may be located somewhere in the internal path of the optical switch, as indicated by the long, dashed circle in the figure. If the detector 33 is located in the optical switch 82, the detector 33 may be located anywhere between the input port of the optical switch 82 and the output port before switching. The detector 33 may be a means for detecting the input intensity of the optical switch 82 or the input intensity of the device to which the switch 82 is output.

[0050] 9 shows an example of a path switching method. In this embodiment, step S12 includes step S22 in which the controller 81 confirms that the light-emitting unit 31 is extinguished based on the detection result of the detector 33. In step S13, the controller 81 switches (switches) the path of the optical switch 82 after confirming that the light is extinguished based on the detection result of the detector 33. Then, after confirming a response that the path switching is complete (S14), the controller 81 controls the terminal 83 to emit light (S15).

[0051] Here, in step S22, the quenching of the switch input intensity is exemplified, but it is sufficient to know the quenching. For example, the following may be determined in step S22. - Quenching of the switch output intensity - Quenching of the monitor light branched off in the switch input path - Quenching of the monitor light branched off in the switch output path - Quenching of the input to a functional unit or device to which the switch output is input - Quenching of the input to an output destination device to which the switch output is input, for example, an optical amplifier - Reduction in the input to an output destination device to which the switch output is input, for example, an optical amplifier

[0052] Furthermore, while the detection unit 33 is an optical detection unit that detects light emission and extinction, it may also include a switching detection unit that detects switching. In this case, completion of switching is detected in step S14 of FIG. 9 . For example, if the optical switch uses heat to switch paths, the switching detection unit may detect heat distribution in the optical switch. For example, it may detect the temperature of the MZ involved in path switching, or the temperature of an arm on a specific side of the MZ involved in path switching. In optical switches that use micromirrors or optical switches that switch paths by changing fiber connections, path switching due to changes in the mirror angle or fiber connection may be detected by image processing or the like. It may also be detected from changes in the current or voltage applied to each MZ or mirror. The method of checking changes in the target to which the applied current or voltage is applied can also be applied to switches that switch the signal direction or path using piezos or the like. Assist light, the influence of which can be ignored due to leakage, for example, light having a wavelength, mode, polarization, or propagation direction different from that of the optical signal used as the main signal at the leakage destination, may be introduced, and the change in the port that detects the assist light on the exit side of the optical switch or the change in the detected position inside the switch may be detected to actually detect the path switching. Alternatively, as exemplified in the second embodiment, detection may be performed by the switching response from the optical switch 82.

[0053] Note that "switching completion" includes "detection of switching completion." This is because although Figures 9 and 10 show variations in only detecting extinction, there are also variations in detecting switching completion. In other words, "switching completion?" includes "switching completion received?" and "switching detected?"

[0054] Fourth Embodiment The system configuration of this embodiment is the same as that of the third embodiment, except that the detector 33 is provided in the optical switch 82. An example of a path switching method is shown in Fig. 10. In this embodiment, in step S12, the optical switch 82, rather than the controller 81, performs step S23 to confirm that the light-emitting unit 31 is extinguished based on the detection result of the detector 33.

[0055] Here, confirmation of the response may be substituted by the passage of a predetermined time from the start of control to the completion of control. This is preferable in a configuration in which the controller 91 controls the terminal 83 by connecting the main signal path from the terminal 83 to the controller 91 by path switching, which will be described later, and in which, when light is emitted after the path is connected to a device such as the terminal 83 opposite the terminal 83 by path switching, the control path from the controller 91 to the terminal 83 has already been cut off.

[0056] In this embodiment, as in the second and third embodiments, "Switching End?" may be used to detect the end of switching or to receive a notification of the end of switching. That is, "Switching End?" includes "Switching Completion Received?" and "Switching Detected?"

[0057] Fifth Embodiment Fig. 11 shows an example of a system configuration of this embodiment. This embodiment is based on wavelength allocation, but the same applies to route switching that does not involve wavelength allocation, in which dynamic crosstalk can have an effect. This also applies to other embodiments. In this embodiment, a controller 81 is provided in a controller 91, and an optical switch 82 is provided in an APN-G 92.

[0058] First, the terminal 83 sends an optical path setting request to the controller 91 via the APN-G92 (S101). Next, the controller 91 determines the route for communication between the terminal 83 and the opposing terminal 83, and, if necessary, the wavelength, and, if necessary, controls the terminal 83 via the APN-G92 regarding the wavelength (S102). The controller 91 controls the APN-G92 and has the function of managing wavelength resources and designing the optical path route for the entire APN. Next, the port connection within the APN-G92 is changed (route switching) (S103). Next, a route (path) between the two terminals 83 is opened using the route according to the control, and, if necessary, the wavelength according to the control (S104). Here, the request is illustrated only from the terminal 83 on the left side, but requests may be received from the terminals 83 on both sides, and the path may be opened only if the requests regarding the connection destinations match.

[0059] In S102 after wavelength design, if wavelength control is required, the controller 91 or the APN-G 92 under the control of the controller 91 performs remote wavelength control of the terminal 83. The optical switch 82 in the APN-G 92 changes the port connection in accordance with the determined route (switches the route connecting the terminal 83 with the opposite terminal 83).

[0060] Hereinafter, a procedure will be described for a control signal in which an auxiliary management and control channel (AMCC) is superimposed on a main signal, in which the terminal 83 is controlled from the controller 91 with the main signal path from the terminal 83 connected to the controller 91. Next, a procedure will be described as a second case in which, although the control signal is an auxiliary management and control channel (AMCC) superimposed on a main signal, part of the main signal is branched or the like, and the main signal path of the terminal 83 is requested or controlled via the controller 91 directly or indirectly via the APN-G 92 or the like, without switching the main signal path with the opposing terminal 83. Finally, a procedure other than AMCC will be described.

[0061] The use of AMCC is effective in achieving protocol-independent access control. The AMCC of the control signal is superimposed on the low-frequency band with the same wavelength as the client signal, so that the control signal and the client signal can be multiplexed separately in frequency.

[0062] In this embodiment, when AMCC is used to control the exchange of a main signal on which a control signal is superimposed between the terminal 83 and the controller 91, the controller 91 cannot control the terminal 83 to extinguish light before the port connection change (path switching) in step S103. Therefore, the terminal 83 continues to emit light, and the light reaches the APN-G92. Therefore, in this embodiment, the APN-G92 detects light emission and extinction. To do this, the terminal 83 emits light to allow the controller 91 to detect its connection to the APN-G92, and then extinguishes the light before switching the path to exchange control signals with the controller 91. Then, after detecting the light emission of the terminal 83, the controller 91 confirms that the light has been extinguished from the terminal 83 before changing the port connection (path switching) in step S103 (here, if the controller 91 is emitting downstream light to transmit a control signal, the controller 91 also extinguishes the light during the path switching). After step S103, the terminal 83 emits light due to a timer or control (from the controller 91 that has re-emitted light), and before the route switching that connects the path that is opened in step S104, the terminal 83 turns off the light due to control from the controller 91 before the re-extinction, and after the connection change, the terminal 83 emits light. Here, since it is not possible to directly control the light emission after the connection change (route switching), the light is emitted when time has elapsed controlled by a timer or the like.

[0063] For example, when a terminal 83 that is not connected to a connection terminal (port) of APN-G92 via an access fiber in the access area is connected (initial connection) via an access fiber in the access area, the terminal 83, the access fiber in the access area between the terminal 83 and APN-G92, etc., along the way to APN-G92, or in APN-G92, monitors the optical input from the terminal 83, and changes the connection of the connection terminal (port) (path switching) upon optical detection, and the request of S101 is implemented. Also, when a path between terminals 83 is established after the initial connection, and a connection change (switching) is made to change the connection partner, a part of the main signal is branched inside the terminal 83 and APN-G92 to extract a control signal from the main signal and notify the switching request of S101, or the terminal 83 notifies the presence of a request by extinguishing the main signal.

[0064] In the first case, a connection change (path switching) between the terminal 83 and the controller 91 is required before S101. However, in this case, extinction control is not possible, so the terminal 83 is controlled in advance to extinguish after the time required for the light emission of the terminal 83 to be detected has elapsed. This control may be replaced by preprogramming and setting the sequence of the terminal 83's operation. The controller 91 may switch the path for the control of S101 and S102 after a time sufficiently longer than the time it takes for the terminal 83 to extinguish after emitting light, or may switch the path after detecting extinction. After the path switching, the controller 91 emits light and executes S101 when a preprogrammed, predetermined time has elapsed, or when a signal is received from the controller 91. After S102, the controller 91 continues extinguishing the light in accordance with the control in S102 or a preconfigured setting for a time sufficient for the path switching to be performed in S103, and then emits light after the time has elapsed.

[0065] In the second case, since the path for the control of S101 and S102 has been established, after receiving remote control in S102, the light continues to be extinguished according to the control in S102 and the preset settings for a sufficient time for path switching to be carried out according to S103, and then the light is emitted after the time has elapsed.

[0066] In the third case, the light indicating the presence of a request may remain extinguished until it is detected by the APN-G 92 or the controller 91 and path switching is performed for the control of S101 and S102. After path switching, the light is turned on and S101 is performed when a predetermined time set in advance by programming has elapsed or when a signal is received from the controller 91. After S102, the light may remain extinguished in accordance with the control in S102 or a preset setting for a sufficient time for path switching to be performed in accordance with S103, and then the light may be turned on after the time has elapsed.

[0067] (Sixth embodiment) Fig. 12 shows an example of a system configuration of this embodiment. In this embodiment, the main signal path from the terminal 83 is connected to the controller 91, and the terminal 83 is controlled from the controller 91, and this is an example in which a control signal in which AMCC is superimposed on the main signal is used. Fig. 12 corresponds to the first process described above.

[0068] When a new terminal 83 is initially connected to the APN and the optical switch 82 detects the connection of the new terminal 83 by detecting transmission of an optical signal from the terminal 83 (S201), the optical switch 82 notifies the controller 91 of the connection (S202). After the detection in S201 and before the path switching in accordance with S203 is performed, the terminal 83 turns off its light. The path switching is performed after the time from when the terminal 83 emits light to notify the controller 91 of the initial connection until when the light is turned off, or after it is confirmed that the input optical signal itself is turned off.

[0069] The controller 91 controls the optical switch 82 to register the new terminal 83 and open a path for initial connection, and changes the connection (route switching) of the port through which the controller 91 communicates with the new terminal 83 via the management port (S203). After the path is established in S203, the terminal 83 emits light when a timer detects the passage of time or when it receives a signal from the controller 91. The controller 91 and the new terminal 83 communicate with each other using AMCC or other protocols that are independent of the client signal protocol. AMCC may be used to electrically multiplex and modulate the main signal and control signal, or optically modulate and multiplex using different optical modulators, or to combine modulated light. When the controller 91 transmits only the control signal to the terminal 83, the signal from the controller 91 may be modulated only by the control signal rather than AMCC. This is also true for other embodiments. Using AMCC or other protocols, the new terminal 83 requests a path from the controller 91 (here, it reports information about the requested path, such as the destination and available wavelength range) (S204). The requirements include not only information about the communication partner, but also quality requirements such as bandwidth, delay, and jitter.

[0070] The controller 91 calculates a path that satisfies this requirement (here, it determines the route of the optical path from the terminal 83 to the opposing terminal 83, etc., and determines the wavelength if necessary) (S205). After the path calculation, if it is necessary to control the wavelength, the wavelength is set by remote wavelength control of the terminal 83 from the controller 91 using AMCC. If it is not necessary to control the terminal 83 with respect to the wavelength, the time to re-emission, etc., this procedure may be omitted.

[0071] Before switching the route to the destination terminal 83 or the destination site, the terminal 83 turns off. The turning off may be performed together with the control in S205, or may be turned off after a predetermined time upon receiving control in S205. Next, after confirming that the terminal 83 and the controller 91 for switching the route of the main signal have turned off, the optical switch 82 changes the port connection according to the route allocation, thereby switching the route of the main signal connecting the terminal 83 and the destination terminal 83 (S206). After the route switching, the light is emitted again after a predetermined time has elapsed. In this way, dynamic crosstalk is reduced and signal continuity is achieved.

[0072] In this embodiment, first, in step S201, the terminal 83 emits light to identify the initial connection, and after being identified by the controller 91, the terminal 83 turns off the light. After the terminal 83 turns off the light, step S203 is executed, and the controller 91 notifies the optical switch 82 of a request signal from the terminal 83. However, during path switching, the downstream signal light is also turned off. After the path switching by the optical switch 82 connects the terminal 83 to the controller 91, the terminal 83 turns on the light due to the elapse of time on a timer or control by the controller 91, and step S204 is executed. When step S205 is completed, after control from the controller 91, the terminal 83 turns off the light due to control from the controller 91 or a timer, etc., and the controller 91 also turns off the light, and then the path is switched in step S206. After the path switching, the terminal 83 emits light.

[0073] (Seventh embodiment) Fig. 13 shows an example of a path switching method. In this embodiment, the main signal path from the terminal 83 is connected to the controller 91, and the terminal 83 is controlled from the controller 91, and a control signal in which AMCC is superimposed on the main signal is used. Fig. 13 corresponds to the third case.

[0074] S301: The terminal 83 requesting switching (hereinafter, the requesting terminal) turns off its light to notify the switching request. The controller 91 detects the switching request by detecting the extinction of the requesting terminal 83, and turns off its light in preparation for path switching to control the extinguished requesting terminal 83. The already-opposed terminal 83 opposite the requesting terminal 83 detects the switching request of the extinguished requesting terminal 83 by the extinguishing of the requesting terminal 83, and turns off its light in preparation for path switching to control the extinguished requesting terminal 83.

[0075] S303: With the previously opposed terminal 83 opposed to the request terminal 83 and the controller 91 remaining unlit, the request terminal and the controller 91 are connected by switching the path of the switch for request and control.

[0076] S302: After the path switching between the controller 91 and the requesting terminal 83 is completed, the controller 91 and, if necessary, the requesting terminal 83 emit light. The controller 91 may emit light after the path switching is completed, and the requesting terminal 83 may emit light in response to the light. The lights may also be emitted after a sufficient time has passed until the path switching is complete. The sufficient time can be estimated from the time required for each procedure. However, if the controller 91 has a backlog of connection requests, such as initial connection requests, or switching requests, such as a change in connection destination, waiting to be processed, it may take longer than the estimated time to complete the switching. In this case, if the controller 91 emits light and sends a request after the estimated time, but does not receive a response from the controller 91 by a predetermined time, the light may be turned off, and the cycle of emitting light and sending a request after a predetermined time may be repeated.

[0077] The controller 91 checks the light emission state of the requesting terminal while the optical switch 82 is switching the path, and switches the path during a time when light is not being emitted. That is, steps S303 and S302, or steps S301, S303 and S302, or steps S301, S303, S302 and S304 are repeated until the request is transmitted and received by the controller 91. Which occurs depends on whether the terminal re-emits light upon receiving a control light or the like from the controller, or whether the terminal re-emits light upon the passage of a predetermined time. In the former case, it also depends on whether the controller does not detect the presence of a connection request such as an initial connection and starts over from the notification of the presence of a request, etc.

[0078] S304: The requesting terminal transmits a switching request to the controller 91, including information on the new opposite terminal to which the requesting terminal is newly requesting connection (initial connection). If the new opposite terminal requesting connection is not registered or is currently communicating with another terminal and therefore cannot be connected, the requesting terminal receives a notification of this from the controller 91, and may re-request connection with another new opposite terminal, may request switching back, or may wait until registration or communication is completed. After the request-related exchange is completed, the requesting terminal remains extinguished until the connection is switched to the controller 91 to receive control of S309, or until S310 is completed if control of S309 is not required.

[0079] S305: If the new opposite terminal is in a switch-waiting or connection-waiting state, the controller 91 confirms that the requesting terminal previously connected to the controller 91, the controller 91 itself, and the new opposite terminal to which the controller 91 will newly connect are in an extinguished state before switching the route and connecting the new opposite terminal to the controller 91. The new opposite terminal then sends a request to the controller 91. If the new opposite terminal is in a standby state, the controller 91 has already acquired the request from the new opposite terminal, so this step can be omitted. Even if the new opposite terminal is already in a standby state, the controller 91 may still connect to the new opposite terminal and reconfirm the request. Reconfirming the request is preferable if the request content of the new opposite terminal changes during standby. If this step is omitted, the controller may proceed to S306, S309, S307, and S310. Alternatively, the controller may proceed to S306 and S307, and before the control in S307, the controller 91 may confirm that the requesting terminal previously connected to the controller 91, the controller 91 itself, and the new opposite terminal to which the controller 91 will newly connect are in an extinguished state, and then switch to a route connecting the new opposite terminal to the controller 91.

[0080] S306: The controller 91 determines the route between the requesting terminal and the new opposite terminal and, if necessary, the wavelength.

[0081] S307: Since the new opposite terminal remains connected to the controller 91, it receives control from the controller 91, including the emission wavelength (including the case where the wavelength remains the same), and turns off the light if necessary. The light continues to be turned off until the route is switched to connect to the requesting terminal.

[0082] S308: If there is no change in the wavelength of the requesting terminal and the requesting terminal is in a state where it will re-emit light after connecting with the new opposite terminal over time, etc., proceed to option No. Even if there is no change in the wavelength of the requesting terminal, if the requesting terminal is in a state where it will re-emit light after connecting with the new opposite terminal due to control received after reconnecting with the requesting terminal and controller 91, proceed to S309.

[0083] S309: After the route switching that connects the requesting terminal and the controller 91 is completed, the requesting terminal receives control from the controller 91. If the requesting terminal is emitting light, it will turn off the light before the switch to connect with the new opposite terminal begins. After the switch to connect the requesting terminal and the controller 91 is completed and before the switch to connect with the new opposite terminal begins, the requesting terminal may either emit light or turn off the light as long as no dynamic crosstalk accompanying the route switching occurs. S310: After the route switching that connects the requesting terminal and the new opposite terminal is completed, both terminals will emit light.

[0084] In the above case, if the terminal turns off the light, switches the route, and then lights up after connecting to the controller 91, it is desirable that the light be emitted upon receiving a control signal from the controller 91.If the terminal turns off the light, switches the route, and then lights up after connecting to the opposite terminal, it is desirable that the light be emitted after a predetermined time controlled by the controller 91 has elapsed.

[0085] The former is because there are cases where it is unclear how long it will take for the route switching to be completed after the light has gone out to connect to the controller 91, and there is a risk that the light will be emitted before the route switching to reconnect to the controller is completed. If this is not done, if the connection with the controller 91 cannot be confirmed even after waiting for a predetermined time, the terminal 83 will go out, and the station will have to take measures such as switching the route after confirming that the light has gone out from the terminal 83.

[0086] In the latter case, the controller 91 is not connected after the route switching, so immediate light emission from the controller 91 cannot be controlled. If, due to some accident, the route switching between the terminals 83 is not completed by the time of light emission, the controller 91 postpones the route switching if there is a risk that the route switching will not be completed before light emission, and turns off the light again before performing the route switching. If the terminal 83 that emitted light cannot confirm reception of a signal from the other terminal 83, it detects that the route switching has not been performed, turns off the light, waits for the route switching, and then emits light. This procedure of light emission and extinguishing while waiting for the route switching may be repeated until reception of a signal from each terminal 83 is confirmed. Such suppression of route switching when light is emitted before the route switching of the optical switch 82 is completed, waiting for extinguishing or confirming extinguishing and then performing the suppressed route switching, light emission at the terminal 83 under control of the controller 91, and extinguishing when no signal is received from the other terminal 83 and subsequent light emission may be performed in a manner other than that of this embodiment.

[0087] In this embodiment, steps S302 and S303 of the reference example are reversed, and the terminal 83 emits light after completing path switching of the optical switch 82 connecting the terminal 83 and the controller 91. If it is necessary to perform step S302 before step S303, the light is extinguished between steps S302 and S303, and after completing path switching connecting the requesting terminal and the controller 91, the light is emitted before step S304 to exchange connection requests. The downstream light from the controller 91 is also extinguished in the same way.

[0088] In this embodiment, the downstream light from the requesting terminal and the controller 91, and the new opposing terminal are in an extinguished state at step S305, and the downstream light from the controller 91 is emitted after the path switching connecting the controller 91 and the new opposing terminal is completed and before the wavelength control step S307.

[0089] In this embodiment, before the control of step S309, the downstream light from the controller 91 is turned off, and the request terminal and the new opposite terminal remain turned off while the path connecting the request terminal and the new opposite terminal is switched, and step S309 is performed, and after step S310, the request terminal and the new opposite terminal emit light. Here, wavelength control to the request terminal includes no wavelength change.

[0090] In addition, if the light emission control is not performed directly from the controller 91 after step S310, such as when the time elapses using a timer or the like in step S307, the downstream light of the controller 91 and the requesting terminal are turned off after step S309, a route is switched to connect the controller 91 and the new opposing terminal, and after the route switch is completed, light emission control is performed to connect the requesting terminal and the new opposing terminal, and step S310 is performed after the lights of the controller 91 and both terminals are turned off.

[0091] In this embodiment, the terminal 83 voluntarily turns off the light to notify that there is a switching request (S301). Therefore, the terminal 83 can communicate with the controller 91 at the timing requested by the terminal 83 without adding a new interface. The controller 91 also determines whether or not a wavelength change is necessary (S308). If necessary, the wavelength of the terminal 83 is remotely set using the same procedure as when the optical path was opened (S309).

[0092] Eighth Embodiment FIG. 14 shows an example of a system configuration of this embodiment. In this embodiment, a terminal control unit 84 that controls a terminal 83 is provided in the APN-G 92. The terminal control unit 84 functions as part of the controller 91 or as an extension of the controller 91. Specifically, the terminal control unit 84 switches the route by switching the optical switch 82 to connect a main signal port connected to a predetermined terminal 83 to a main signal port connected to a terminal control unit, or to connect a control port connected to a predetermined terminal 83 to a control signal port connected to a terminal control unit, or to connect a control signal from the predetermined terminal 83 to a terminal control unit by switching the control signal, or to select a control signal for the predetermined terminal 83 using other means, such as the optical switch 82 or an electrical switch, to connect the predetermined terminal 83 to the terminal control unit, and then switches the route connecting the controller 91 and the terminal 83 by temporarily terminating the control signal at the terminal control unit 84 and passing it through the terminal control unit, or by switching the route to exchange control directly between the controller 91 and the predetermined terminal 83 without terminating the control signal at the terminal control unit. This is similar to other embodiments. In this embodiment, the main signal path from the terminal 83 is connected to the controller 91, and the terminal 83 is controlled from the controller 91, and this is an example in which a control signal in which AMCC is superimposed on the main signal is used.

[0093] An example of a route switching method is shown in Figure 15. When a fault such as a disconnection is detected, the controller 91 determines a new path to switch the route where the fault such as a disconnection was detected, and a wavelength if necessary (S401). Each terminal 83 turns off the light when it detects a loss of the received signal from the opposing terminal 83 or a deterioration in the quality of the received signal that requires switching. Here, even if there is a fault in one direction, the signal in both directions will be turned off due to the turning off of the opposing terminal 83. As a new route, the same route in the direction without any fault may be selected as a result.

[0094] Based on the determination, the controller 91 checks whether a wavelength change is necessary for each terminal 83 (S402). If this check determines that a wavelength change is necessary, the APN-G 92 changes the port connection within the optical switch 82, and if a wavelength change is necessary for both terminals 83, it switches to a route connecting one of the terminals 83 to the terminal control unit 84 (controller 91) (S403). The terminal control unit 84 then uses a control signal to control the terminal 83 to change the wavelength (S404), and the terminal 83 changes the transmission wavelength. At this time, control is performed to re-emit light at the time when the route switching is completed in S406. After the control, the controller 91 and the terminal 83 turn off the light (S405).

[0095] If the wavelength of both terminals 83 needs to be changed, steps S403 to S405 are performed for the other terminal 83. Finally, the APN-G 92 on the new route changes the port connections of the optical switches 82 that connect the terminals on the new route, and switches the route. For example, if both the old route and the new route pass through only the top two optical switches 82, the top two optical switches 82 are set. If the old route passes through only the top two optical switches 82 and the new route passes through three optical switches 82, three optical switches 82 are set. If the old route passes through three optical switches 82 and the new route passes through only the top two optical switches 82, at least the top two optical switches 82 are set.

[0096] In the last example, the unused path of the bottom optical switch 82 may also be blocked (S406). When the path switching to reconnect the terminals in S406 is completed, both terminals emit light, and communication resumes. If the controller 91 determines in step S401 to continue using the wavelength originally used, it determines in step S402 that control to change the wavelength of the terminal 83 is unnecessary. If both terminals are to re-emit light without controlling the re-emission time or other factors other than wavelength change (for example, if the terminal 83 is configured to re-emit light after a predetermined time has elapsed since it was extinguished due to a fault), steps S403 to S405 are skipped. If other control is required even without wavelength change, the controller 91 and terminal 83 are turned off in steps S403-S405, and the path switching to connect each terminal 83 to the controller 91 is controlled, and the light is extinguished.

[0097] In this embodiment, the downstream light from the controller 91 is extinguished before step S403, the downstream light of the controller 91 is turned on before control is given to the terminal 83 in step S404, the light is extinguished for the terminal 83 in step S405 until the route is switched to connect the terminals 83 to each other in step S406, and after the route switching is completed in step S406, the downstream light of the controller 91 is extinguished after the route switching is completed. For the extinguishing control, the route is switched in the extinguished state and the extinguishing control is also performed on the opposite terminal 83, and step S406 is entered with the opposite terminal 83 also in the extinguished state.

[0098] 16 shows an example of a system configuration of this embodiment. In this embodiment, the control signal is separated from the main signal before being input to the optical switch 82, making it possible to control the signal regardless of the main signal path. An input from a terminal 83 is separated by a filter 85 into a control signal directed to a controller 91 and a main signal directed to the FXC 71, which is the optical switch 82. The input to the terminal 83 is multiplexed by the filter 85 into the control signal from the controller 91 and the main signal from the FXC 71, which is the optical switch 82. The demultiplexing multiplexing will be exemplified below as wavelength division multiplexing using different wavelengths for the main signal and the control signal. However, other demultiplexing multiplexing methods may also be used, such as polarization division multiplexing using different polarizations, mode division multiplexing using different modes, core multiplexing using different cores, core wire multiplexing using different core wires, frequency division multiplexing using different modulation frequencies, time division multiplexing using different time slots, or a filter that demultiplexes according to a combination of the above including wavelength division multiplexing.

[0099] In this configuration, the main signal and control signal are sent and received through different ports (the main signal port of the optical switch 82 and the control (signal port) of the control signal relay unit), so it is necessary to determine which ports for each signal correspond to each other and which are sending and receiving signals from the same terminal 83.

[0100] When the terminal 83 sends a control signal to the APN-G 92, the filter 85 separates the control signal and sends it to the control signal relay unit 86. In the case of wavelength division multiplexing, the filter is a wavelength filter that separates and multiplexes the control signal and the main signal. In the case of other types of separation and multiplexing, the separation and multiplexing is performed using a filter equivalent to the separation and multiplexing method. Like the terminal control unit 84 described above, the control signal relay unit 86 is a functional unit that either terminates and relays the control signal or relays it without terminating it. It is considered an extension of the controller 91, and may be referred to below as the controller 91 instead of the control signal relay unit 86. The control signal relay unit 86 detects which port of the optical switch 82 the control signal arrived at and transmits it to the controller 91 along with the port number at which the control signal was detected. The controller 91 is previously provided with a correspondence table of control (signal) ports and main signal ports. This allows the controller 91 to determine the main signal port connected to the terminal 83 that sends and receives the control signal at that control signal port from the control (signal) port to which the control signal is input. Information about the newly identified terminal 83 may be added to a correspondence table showing the correspondence between the control (signal) port and the main signal port of the optical switch 82 .

[0101] In this embodiment, extinguishing of the control signal is not necessary because the exchange of control signals from the terminal 83 and the controller 91 does not result in crosstalk of the main signal. Therefore, at the time of initial connection, the main signal is not extinguished when switching the path for exchanging the control signal, but is extinguished before switching the main signal path, and is re-emitted after the path is switched.

[0102] Depending on the specifications of the transmitter used by the terminal 83, the light may be extinguished if the wavelength is changed, but not if it is not. Even if the light is extinguished, the extinguishing process does not continue from before the path switching of the optical switch 82 begins until it is completed, which is why the procedure described in this application is necessary. If the standard specifies the maximum delay time from the start of extinguishing control or wavelength conversion control to the start of extinguishing and the minimum delay time from the completion of extinguishing, it is possible to apply this application so that the path switching of the optical switch 82 occurs during that time. Even with such specifications, if a wavelength change is not involved, time is required from extinguishing to re-emission, and not extinguishing shortens the set time, so the light is usually not extinguished. However, in this application, to reduce dynamic crosstalk, the light is extinguished during the path switching of the optical switch 82, regardless of whether a wavelength change is performed. Not only in the case of path switching during initial connection, but also in the case of path switching due to a port connection change, the light is extinguished before the path switching of the signal and re-emission after the switching is completed, regardless of whether a wavelength change is required.

[0103] (Tenth Embodiment) Fig. 17 shows an example of a system configuration of this embodiment. In this embodiment, the control signal is separated from the main signal before being input to the optical switch 82, and can be controlled regardless of the main signal path. In this example, the optical switch 82 is an FXC 71. A terminal control unit 84 conducts the control signal through a 1:N connection, for example, a PON. For example, a terminal 83 and the FXC 71 are connected by a filter 85, and the filter 85 is connected to an OLT 88 via a coupler 87. This constitutes a PON for control signals.

[0104] In this example, unlike the ninth embodiment, there is no correspondence table between the control port that exchanges the control signal of the terminal 83 with the controller 91 and the main signal port that exchanges the main signal of the terminal 83 with the opposing terminal 83, and there is no one-to-one correspondence between the control port and the main signal port of each terminal 83, so this is an example in which the correspondence is confirmed by the change in the main signal in response to control by the control signal.

[0105] Here, the control port is a port of the APN-G92 that exchanges control signals with the control port or the terminal 83. The main signal port is a port of the optical switch 82 of the APN-G92 that exchanges main signals with the opposing terminal 83 or site via the APN-G92 or the like. Control of the optical switch 82, which switches to a path that changes the connection between the main signal ports of the APN-G92 to which each terminal 83 is connected in order to switch the path of the main signal between the terminal 83 and the opposing terminal 83, is performed on the path connecting the controller 91 and the optical switch 82. The path connecting the controller 91 and the optical switch 82 may be via the optical switch itself or another optical switch 82. In this case, the port connecting the control unit of the optical switch 82 itself and the main signal port of the optical switch 82 is the control port that controls the optical switch 82 from the controller 91, i.e., the port that switches the path connecting the controller 91 and the terminal 83.

[0106] An example of the latter is when a 1:N connection, such as a PON connection, is applied to either the control signal or the main signal. In this example, the change in the main signal is exemplified as a change from extinction to emission of the main signal, but other changes, such as controlled emission to extinction, a controlled wavelength change, or a controlled dithering frequency, may also be used.

[0107] 18 shows an example of a route switching method at the time of initial connection. The controller 91 detects the physical connectivity between the newly connected terminal 83 and the APN-G 92 via the field access fiber (S501, S502, S503, S507). Here, although an example is given of a path request at the time of initial connection, the correspondence between the control port (or control signal port) and the main signal port is already known at the time of the switching request, so the process of confirming the correspondence can be omitted.

[0108] The controller 91 controls the emission of a main signal light to the terminal 83 requesting optical path setup only after the authentication and registration of the terminal 83 are successful (S502). The terminal 83 emits light in accordance with this control (S503). The optical switch 82 detects the emission and notifies the controller 91, which then detects that the port of the FXC 71 that newly detected the optical input is physically connected to the terminal 83 that requested the optical path setup (S504). After causing the terminal 83 to turn off the light, the controller 91 controls the optical switch 82 to switch the path so that the terminal 83 is connected to the opposite terminal (S505). The control in S505 is based on the premise that the controller 91 knows the connection port of the opposite terminal. Since the connection port of the opposite terminal is usually determined after S508, it is appropriate to switch the path in S505 simultaneously with or before or after S509 after S508. That is, it is desirable to switch the route (S505) after S508 when the main signal port to which the opposite terminal is connected becomes clear, but if only two terminals 83 are simultaneously requesting connection with each other, an estimate may be made and connection may be made at the time of S505. If the estimate is incorrect, the route may be switched back to the correct route after S508. A similar process is performed on the other terminal 83 to detect that it is connected (S506, S507, S508).

[0109] In the first step S501 of the sequence, the terminal 83 reports its type (DWDM, non-DWDM), the requested path type (wavelength path, fiber path), and the opposing terminal to be connected. Based on these reports, the controller 91 determines the wavelength path or fiber path after the initial connection (S505, S509).

[0110] The terminal 83 keeps the main signal light off until light emission permission is obtained (S512, S514). Even when multiple terminals 83 are connected to the APN at the same time, the controller 91 sequentially recognizes the physical connectivity between each terminal 83 and the APN-G 92 by staggering the start of light emission of the main signal light in steps S511 and S513 by a sufficient interval. The sufficient interval is equal to or longer than the time it takes for the controller 91 to control light emission, for the terminal 83 to emit light in response to the control, and for the controller 91 to confirm that the optical signal from the terminal 83 that emitted light in response to the control has arrived.

[0111] In this embodiment, as in the eighth embodiment, the control signal and the main signal have different wavelengths, and only the main signal is input to the FXC 71, so there is no need to extinguish the control signal. In this example, to identify the main signal port, the FXC 71 is extinguished before switching the path (S512, S514). After switching the path, the light is re-emitted (not shown). Note that re-emission may occur after the path switching of the optical switches 82 related to the terminals 83 at both ends is completed.

[0112] It is desirable to perform route switching (S505) after step S508, when the main signal port to which the opposing terminal is connected is clarified. However, if only two terminals are simultaneously requesting connection with each other, an estimate may be made and the connection may be made at the time of S505. If the estimate is incorrect, the route may be switched back to the correct route after S508. In this sense, it is also desirable to perform route switching (S505) after S508, when the main signal port of the opposing terminal 83 has been confirmed.

[0113] Although the above embodiment has shown an example of an APN, the present disclosure can also be applied to cases other than an APN where it is desired to avoid the effects of dynamic crosstalk in a network that uses an optical switch 82. Examples include the following: A network within a data center that includes an optical switch 82 in its path. A network that performs hitless switching or redundant switching using an optical switch 82. In a redundant PON, when some communicating ONUs remain, and the PON interface to which the other ONUs are connected is switched. In a PON, when an ONU that is communicating and that was connected to a PON interface other than the communicating ONU is switched to the PON interface connected to the other communicating ONU.

[0114] (Other Embodiments) The controller 81 of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. The program of the present disclosure is a program for causing a computer to realize each function of the controller 81 according to the present disclosure, and is a program for causing a computer to execute each procedure of the method executed by the controller 81 according to the present disclosure.

[0115] 31: Light emitting unit 32: Responder 33: Detector 71: FXC 72: WSS 81: Controller 82: Optical switch 83: Terminal 84: Terminal control unit 85: Filter 86: Control signal relay unit 87: Coupler 88: OLT 91: Controller 92: APN-G 93: APN-I 94: Termination device

Claims

1. A controller that controls an optical switch that switches the path of an optical signal of a terminal, the controller causing the terminal to turn off before the path of the optical switch is switched.

2. The controller according to claim 1, wherein the controller causes the terminal to emit light after the optical switch switches the path.

3. The controller according to claim 1, wherein the extinction or the path switching is detected in response.

4. A network system comprising: a controller according to claim 1 or 2; and an optical switch that switches the path of an optical signal of said terminal in accordance with the control of said controller.

5. The network system according to claim 4, wherein the optical switch has a dynamic crosstalk value that exceeds a tolerance range set for the path of the optical signal.

6. A path switching method, in which a controller of an optical switch that switches the path of an optical signal of a terminal causes the terminal to turn off the light before switching the path of the optical switch.

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