Route identification system, monitoring device, and route identification method

Abstract

In order to make it easy to identify a currently used path in an optical transmission system having redundant paths, provided is a path identification system comprising: a path group in which one currently used path can be selected from the paths of a plurality of optical transmission lines disposed in parallel; and a monitoring device which sends and receives monitoring light to and from the path group. The path group is provided with: loopback circuits that are respectively disposed on a plurality of paths and that each loop back only monitoring light of a differing wavelength; a first optical switch that connects one end of one of the plurality of paths to a monitoring means; and a second optical switch that selects another end of one of the plurality of paths. The monitoring device is provided with: a monitoring light transmission unit that outputs monitoring light to the first optical switch; a monitoring light reception unit that receives monitoring light from the first optical switch and outputs wavelength information indicating the wavelength of the received monitoring light; and a control unit that, on the basis of the wavelength information and loopback information which records the wavelength of monitoring light looped back by a plurality of loopback means, identifies a loopback circuit in which the received monitoring light was looped back, and identifies, as the currently used path, the path on which the identified loopback circuit is disposed.

Description

Technical Field

[0001] The present invention relates to a path identification system and the like used in an optical transmission system.

Background Art

[0002] In a transmission system using optical fibers (hereinafter referred to as an "optical transmission system"), in order to ensure the reliability of communication, a configuration including redundant paths where a plurality of paths (routes) are laid in parallel may be adopted. When a failure occurs in one of the paths in operation (hereinafter referred to as the "active path"), the reliability of the optical transmission system can be enhanced by switching the path of the optical cable so that another one of the paths laid in parallel becomes the active path by means of an optical switch. As an optical transmission system having redundant paths, for example, an optical submarine cable system (hereinafter referred to as an "optical submarine system") is in operation.

[0003] For switching the path of the optical submarine system, an optical switch installed on the seabed is used. By giving a switching instruction from a land terminal (hereinafter referred to as a "land station") to the optical switch, the active path is configured. However, generally, an optical switch does not have a function of notifying the land station of the path switching state. Therefore, the land station cannot obtain information from the optical switch as to which of the plurality of paths is selected as the active path.

[0004] Therefore, in a general optical submarine system, a monitoring device of the land station transmits monitoring light to the optical cable, measures the intensity of the monitoring light looped back from an optical repeater on the active path, and obtains the distance from the land station to the optical repeater from the intensity. Then, by comparing the obtained distance with the actual distance from the land station to the optical repeater, the path used as the active path is identified. Alternatively, the land station calculates the position of the optical repeater from the position of the reflection point of the monitoring light, and identifies the path where the optical repeater is installed at that position as the active path. For detecting the position of the reflection point, for example, an OTDR (Optical Time Domain Reflectometer) is used.

[0005] In relation to the present invention, Patent Document 1 describes an optical amplification relay device equipped with a function to loop back the main signal. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-292038 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, when the distances between each optical repeater installed in multiple redundant paths and the onshore monitoring equipment are roughly equal, it is impossible to determine which redundant path is being used as the primary path from the intensity of the looped-back monitoring light. Furthermore, if there are multiple paths with reflection points at the same distance, it is impossible to identify the primary path even when using an OTDR. In other words, monitoring equipment for typical optical submarine systems with redundant paths has the challenge of sometimes being unable to identify the primary path.

[0008] (Purpose of the invention) The present invention aims to provide a technique for easily identifying the currently used path in an optical transmission system with redundant paths. [Means for solving the problem]

[0009] The route identification system of the present invention is A set of paths from which one active path can be selected from multiple optical transmission paths arranged in parallel, The system includes monitoring means for transmitting and receiving monitoring light to and from the aforementioned group of paths, The aforementioned group of routes is Loopback means, which are arranged in each of the aforementioned multiple paths and loop back only monitoring light of different wavelengths from each other, A first optical switching means that connects one of the ends of the plurality of paths to the monitoring means, The system includes a second optical switching means for selecting one of the other ends of the plurality of paths, The monitoring means is A monitoring light transmitting means that outputs the monitoring light to the first optical switching means, A monitoring light receiving means that receives the monitoring light from the first light switching means and outputs wavelength information indicating the wavelength of the received monitoring light, The system includes control means that, based on the wavelength information and loopback information recording the wavelength of the monitoring light looped back by the plurality of loopback means, identifies the loopback means to which the received monitoring light was looped back, and identifies the path on which the identified loopback means is located as the active path.

[0010] The monitoring device of the present invention is A monitoring light transmission means that outputs monitoring light to an optical transmission path, A monitoring light receiving means that receives the monitoring light and outputs wavelength information indicating the wavelength of the received monitoring light, A control means that has loopback information recording the wavelength of the monitoring light looped back by a plurality of loopback means on the optical transmission path, identifies the loopback means to which the received monitoring light was looped back based on the wavelength information and the loopback information, and identifies the path on which the identified loopback means is located as the active path, It is equipped with.

[0011] The route identification method of the present invention is A path identification method used in an optical transmission system comprising: a group of paths capable of selecting one active path from a plurality of parallel-arranged optical transmission paths; and monitoring means for sending and receiving monitoring light to and from the group of paths, One of the ends of the aforementioned plurality of paths is connected to the monitoring means by the first optical switching means, The other end of the aforementioned plurality of paths is selected by the second optical switching means, The monitoring light is output to the first optical switching means, Only the monitoring light of different wavelengths from each other is looped back by the loop-back means of each of the plurality of paths. Receives the monitoring light from the first optical switching means and outputs wavelength information indicating the wavelength of the received monitoring light. Based on the wavelength information and the loop-back information recording the wavelengths of the monitoring light looped back by the plurality of loop-back means, identifies the loop-back means to which the received monitoring light is looped back. Identifies the path in which the identified loop-back means is arranged as the active path. [[ID=,7]] Includes steps.

[0012] The control method of the monitoring device of the present invention is Outputs monitoring light to an optical transmission line. Receives the monitoring light. Outputs wavelength information indicating the wavelength of the received monitoring light. Based on the loop-back information recording the wavelengths of the monitoring light looped back by the plurality of loop-back means on the optical transmission line and the wavelength information, identifies the loop-back means to which the received monitoring light is looped back, and identifies the path in which the identified loop-back means is arranged as the active path. Includes steps.

[0013] On the recording medium of the present invention, A procedure for outputting monitoring light to an optical transmission line, A procedure for receiving the monitoring light, A procedure for outputting wavelength information indicating the wavelength of the received monitoring light, A procedure for recording, as loop-back information, the wavelengths of the monitoring light looped back by the plurality of loop-back means on the optical transmission line, A procedure for identifying the loop-back means to which the received monitoring light is looped back based on the loop-back information and the wavelength information, A procedure for identifying the path in which the identified loop-back means is arranged as the active path, are A program for causing a computer of the monitoring device to execute is recorded.

Effect of the Invention

[0014] The present invention provides a technique for easily identifying an active path in an optical transmission system having redundant paths.

Brief Description of the Drawings

[0015] [Figure 1] It is a block diagram showing a configuration example of an optical submarine system of the first embodiment. [Figure 2] It is a block diagram showing a configuration example of a monitoring device. [Figure 3] It is a diagram showing a configuration example of an optical repeater of the first embodiment. [Figure 4] It is a table showing an example of the transmission wavelength of an optical bandpass filter. [Figure 5] It is a block diagram showing a configuration example of a monitoring device applicable to the optical submarine system of the first embodiment. [Figure 6] It is a block diagram showing an example of the minimum configuration of an optical submarine system. [Figure 7] It is a block diagram showing a configuration example of an optical submarine system of the second embodiment. [Figure 8] It is a block diagram showing a configuration example of an optical repeater. [Figure 9] It is a block diagram showing a configuration example of an optical submarine system of the third embodiment.​​​​​​​​​​​​​​​​​​​​​ Embodiments of the present invention are described below. The arrows in each drawing are provided as examples to illustrate the direction of signals, etc., in the embodiments and do not imply any limitation of direction. Furthermore, unless otherwise specified by a black circle or the like, the intersection of lines does not signify the combination of signals, etc., with different directions. Elements that have already appeared in each drawing are given the same names and reference numerals, and redundant explanations are omitted in each embodiment.

[0017] (First Embodiment) Figure 1 is a block diagram showing an example configuration of the optical submarine system 1 according to the first embodiment. The optical submarine system 1 comprises a monitoring device 101, optical repeaters 201 and 202, optical switches 301 and 302, optical transceivers 401 and 402, and an optical multiplexer / demultiplexer 411. These elements are connected by fiber pairs (FPs), which are pairs of optical fibers. Each optical fiber in a fiber pair transmits light in opposite directions. Each fiber pair is an optical transmission path for the optical submarine system 1. In Figure 1, a configuration with redundant paths including optical repeaters 201 and 202 and optical switches 301 and 302 is referred to as path group 751.

[0018] A fiber pair 11 connects the optical multiplexer / demultiplexer 411 to the optical switch 301. A fiber pair 12 connects the optical transceiver 402 to the optical switch 302. Optical switches 301 and 302 are, for example, both 2x4 optical switches. Optical switches 301 and 302 are switched so that fiber pair 11 and fiber pair 12 are connected by a first path or a second path. The first path is a path in which fiber pair 11 and fiber pair 12 are connected via optical switch 301, fiber pair 21, optical repeater 201, fiber pair 31, and optical switch 302. The second path is a path in which fiber pair 11 and fiber pair 12 are connected via optical switch 301, fiber pair 22, optical repeater 202, fiber pair 32, and optical switch 302. In this way, the optical switches 301 and 302 select the active path from a plurality of paths (first and second paths).

[0019] The monitoring device 101 sends the generated monitoring light to one optical fiber of the fiber pair 114. The monitoring light is looped back in a loopback circuit located within the optical submarine system 1. The loopback circuit will be described later. The monitoring device 101 receives the looped-back monitoring light from the other optical fiber of the fiber pair 114. Optical transceivers 401 and 402 transmit and receive user signals transmitted by the optical submarine system 1. For example, optical transceiver 401 transmits a user signal to optical transceiver 402 using wavelength division multiplexing (WDM) signal light and receives WDM signal light transmitted by optical transceiver 402. Hereinafter, WDM signal light will be simply referred to as "signal light". Optical transceiver 402 transmits other user signals to optical transceiver 401 using signal light and receives signal light transmitted by optical transceiver 401. The wavelengths of these signal lights do not overlap with the wavelength of the monitoring light.

[0020] The optical multiplexer / demultiplexer 411 combines (wavelength multiplexing) and demultiplexes (wavelength separation) the monitoring light transmitted and received by the monitoring device 101 and the signal light transmitted and received by the optical transceiver 401. Specifically, the optical multiplexer / demultiplexer 411 combines the monitoring light input from the monitoring device 101 and the signal light input from the optical transceiver 401, and outputs the combined light to the optical switch 301. In addition, the optical multiplexer / demultiplexer 411 receives light from the optical switch 301 that is a combination of the signal light output by the optical transceiver 402 and the monitoring light looped back in the optical submarine system 1. The optical multiplexer / demultiplexer 411 demultiplexes the signal light input from the optical switch 301 and the monitoring light. The optical multiplexer / demultiplexer 411 outputs the demultiplexed monitoring light to the monitoring device 101 and outputs the demultiplexed signal light to the optical transceiver 401.

[0021] Fiber pair 11 is connected to the two ports on the optical switch 301 on the optical multiplexer / demultiplexer 411 side. Fiber pairs 21 and 22 are connected to the four ports on the opposite side. When the optical switch 301 is in the first state, fiber pair 11 is connected to fiber pair 21. When the optical switch 301 is in the second state, fiber pair 11 is connected to fiber pair 22.

[0022] Furthermore, fiber pair 12 is connected to the two ports on the optical transceiver 401 side of optical switch 302. Fiber pairs 31 and 32 are connected to the four ports on the opposite side. When optical switch 302 is in the first state, fiber pair 12 is connected to fiber pair 31. When optical switch 301 is in the second state, fiber pair 12 is connected to fiber pair 32. Figure 1 shows the case where both optical switch 301 and optical switch 302 are in the first state, and as a result, optical switch 301 and optical switch 302 are connected via the first path.

[0023] Optical switches 301 and 302 are controlled by a control signal. The control signal controls optical switches 301 and 302 such that the optical path between them is either a first path or a second path. That is, optical switches 301 and 302 are controlled so that both are in the first state or both are in the second state. The monitoring device 101 may transmit the control signal using a control channel. Alternatively, optical transceivers 401 or 402 may transmit the control signal using a control channel included in the signal light they transmit. Optical switches 301 and 302 may be equipped with optical taps that can branch the light containing the control signal. In this case, optical switches 301 and 302 extract the control signal from the light branched from the optical tap.

[0024] Figure 2 is a block diagram showing an example configuration of the monitoring device 101. The monitoring device 101 comprises a monitoring light transmitting unit 111, a monitoring light receiving unit 112, and a control unit 113. The monitoring light transmitting unit 111 outputs (transmits) monitoring light of a predetermined wavelength to one of the optical fibers of the fiber pair 114. The monitoring light transmitting unit 111 comprises an ASE (Amplified Spontaneous Emission) light source 511 and a WSS (Wavelength Selective Switch) 512. The ASE light source 511 generates broadband spontaneous emission light. ASE is generated, for example, by injecting excitation light into an optical fiber for optical amplification. The WSS 512 is an optical device whose transmission bandwidth and attenuation can be controlled externally. The WSS 512 may be controlled by the control unit 113. By inputting the output of the ASE light source 511 to the WSS 512 and setting the transmission bandwidth of the WSS as the wavelength of the monitoring light 701, the monitoring light transmitting unit 111 can generate monitoring light of a predetermined wavelength. Alternatively, the monitoring light may be generated by a tunable light source. The monitoring light transmitter 111 may also transmit control signals to control the optical switches 301 and 302.

[0025] The monitoring light receiver 112 receives the looped monitoring light from the other optical fiber of the fiber pair 114. The monitoring light receiver 112 measures the spectrum of the received monitoring light and outputs wavelength information indicating the wavelength of the received light to the control unit 113. The monitoring light receiver 112 may be equipped with a general optical spectrum analyzer or spectrometer. The control unit 113 controls the monitoring light transmitter 111 and the monitoring light receiver 112. A maintenance worker makes the necessary settings on the control unit 113 for the operation of the monitoring device 101. Alternatively, a management device that manages the entire optical submarine system 1 may make settings on the control unit 113 remotely.

[0026] Figure 3 shows an example configuration of the optical repeater 201 according to the first embodiment. Optical repeaters 201 and 202 are equipped with a repeater circuit 280 and a loopback circuit 250. The repeater circuit 280 has general functions for relaying optical signals (for example, a monitoring function for the optical repeater and an amplification function for optical signals). The general functions of the repeater circuit 280 are known, so their explanation will be omitted. Furthermore, the configurations of the repeater circuit 280 and loopback circuit 250 equipped in optical repeaters 201 and 202 are common except for the transmission wavelength of the optical bandpass filter 253, which will be described later. Therefore, Figure 3 and the following will describe the optical repeater 201.

[0027] Fiber pairs 21 and 31 are connected to the optical repeater 201. Fiber pair 21 includes optical fibers 21A and 21B. Fiber pair 31 includes optical fibers 31A and 31B. Light propagating through optical fiber 21A is input to the loopback circuit 250. Light propagating through optical fiber 31B is processed in the repeater circuit 280 before being input to the loopback circuit 250. Figure 3 also shows an example of the spectrum of light propagating through fiber pairs 21 and 31. The horizontal axis of the spectrum is wavelength, and the vertical axis is intensity. However, the spectrum in Figure 3 is a schematic example showing the relationship between the wavelengths of the signal light and the monitoring light.

[0028] Optical fiber 21A transmits downstream light 721, which includes monitoring light 701 and signal light. Monitoring light 701 is transmitted from monitoring device 101. Signal light 702 is transmitted from optical transceiver 401. The wavelength of monitoring light 701 does not overlap with the wavelength of signal light 702. Optical fiber 31B transmits signal light 802 transmitted from optical transceiver 402. The wavelength of signal light 802 does not overlap with the wavelength of monitoring light 701.

[0029] The loopback circuit 250 includes optical couplers 251 and 252, and an optical bandpass filter (BPF) 253. Optical couplers 251 and 252 are optical directional couplers. Optical coupler 251 splits the downlink light 721 input from optical fiber 21A into two. One of the split light 212 is output to the optical bandpass filter 253. The other light split by optical coupler 251 is input to the relay circuit 280. The relay circuit 280 performs general relay processing on the downlink light 721 input from optical coupler 251 and outputs the processed light to optical fiber 31A.

[0030] The optical bandpass filter 253 is an optical filter that transmits only a portion of the wavelengths of the downstream light 721 input from the optical coupler 251 and outputs the transmitted light to the optical coupler 252. Specifically, the optical bandpass filter 253 transmits only the monitoring light of a predetermined wavelength within the wavelength band used for the monitoring light 701, and blocks light of other wavelengths.

[0031] Figure 4 is a table showing examples of transmission wavelengths of the optical bandpass filter 253. The transmission wavelength of the optical bandpass filter 253 differs for each optical repeater arranged in parallel. In this embodiment, the transmission wavelength of the optical bandpass filter 253 in optical repeater 201 is λ1, and the transmission wavelength of the optical bandpass filter 253 in optical repeater 202 is λ2. λ1 and λ2 are included in the wavelength band used for the monitoring light 701. Also, λ1 and λ2 are different. The optical coupler 252 couples the monitoring light 701 that has passed through the optical bandpass filter 253 with the signal light 802 transmitted through the optical fiber 31B. The coupled light is output to the optical fiber 21B as upstream light 821. That is, the transmission wavelength of the optical bandpass filter 253 indicates the wavelength of the monitoring light that is looped back in the loopback circuit 250.

[0032] Alternatively, a WSS may be used as the optical bandpass filter 253. By making the transmission wavelength of the WSS in the optical bandpass filter 253 controllable by a control signal from a land-based device, the wavelength of the monitoring light looped back can be changed during operation of the optical submarine system 1. Alternatively, optical couplers 251 and 252 may each be replaced with optical multiplexers / demultiplexers that combine and demultiplex only the wavelength of the monitoring light. In this case, the optical bandpass filter 253 can be omitted.

[0033] In this way, the uplink light 821 transmitted through the optical fiber 21B has monitoring light 701 at a wavelength that the optical bandpass filter 253 transmits through. That is, the uplink light 821 contains monitoring light 701 and signal light 802 processed by the relay circuit 280. If there is no light at a wavelength that the optical bandpass filter 253 transmits through, the uplink light 821 contains only signal light 802. The loopback circuit 250 is installed in each of the multiple paths, the first path and the second path, and loops back only monitoring light of different wavelengths from each other.

[0034] The uplink light 821 propagating through the optical fiber 21B is input to the optical multiplexer / demultiplexer 411 via the optical switch 301 in Figure 1. The optical multiplexer / demultiplexer 411 splits the uplink light 821 into monitoring light 701 and signal light 802. The signal light 802 is received by the optical transceiver 401. The monitoring light 701 is received by the monitoring light receiving unit 112 of the monitoring device 101.

[0035] The control unit 113 stores the data of the transmission wavelength of the optical bandpass filter 253, as shown in Figure 4. When the monitoring light receiver 112 receives the monitoring light 701, it notifies the control unit 113 of its wavelength. Since the transmission wavelength of the optical bandpass filter 253 differs for each optical repeater, the control unit 113 can identify the optical repeater to which the monitoring light 701 was looped back by comparing the transmission wavelength data in Figure 4 with the wavelength of the monitoring light 701 notified by the monitoring light receiver 112.

[0036] For example, if the monitoring light receiving unit 112 receives a monitoring light of wavelength λ1 after the monitoring light transmitting unit 111 has transmitted a monitoring light 701 of wavelength λ1, it indicates that the monitoring light 701 has been looped back by the optical repeater 201. Therefore, in this case, the control unit 113 can determine that the optical switch 301 has selected the first path.

[0037] Furthermore, if the monitoring light is not received by the monitoring light receiving unit 112 after the monitoring light transmitting unit 111 has transmitted the monitoring light 701 with wavelength λ1, it is possible that the monitoring light 701 was looped back at a repeater other than the optical repeater 201. Alternatively, there may be an obstruction in the path through which the monitoring light 701 is transmitted. In this case, the monitoring device 101 may transmit the monitoring light with wavelength λ2. If the monitoring light is received by the monitoring light receiving unit 112 after the monitoring light transmitting unit 111 has transmitted the monitoring light 701 with wavelength λ2, it indicates that the monitoring light 701 was looped back at the optical repeater 202. Therefore, in this case, the control unit 113 can determine that the optical switch 301 has selected the second path. Thus, the optical submarine system 1 of this embodiment has the effect of being able to identify the active path in an optical transmission system with redundant paths. An optical submarine system 1 that has such an effect can be called a path identification system.

[0038] The loopback circuit 250 may be incorporated inside the optical repeater 201, or it may be added externally to a typical optical repeater equipped with a repeater circuit 280. By making the loopback circuit 250 structured to be addable to a typical optical repeater, the loopback function described above can be added to an existing typical optical repeater.

[0039] Furthermore, the loopback circuit 250 can be placed on at least one of the fiber pair 21 side and fiber pair 31 side of the relay circuit 280. In Figure 1, the loopback circuit 250 may be placed between the optical repeater 201 and the optical switch 301, and between the optical repeater 201 and the optical switch 302.

[0040] (Modified version of the first embodiment) Figure 5 is a block diagram showing an example configuration of a monitoring device 101A applicable to the optical submarine system 1 of the first embodiment. The monitoring device 101A is used in place of the monitoring device 101 in Figure 1.

[0041] The monitoring device 101A includes a monitoring light transmitting unit 111A in place of the monitoring light transmitting unit 111 of the monitoring device 101. The monitoring light transmitting unit 111A includes an ASE light source 511 and an optical bandpass filter (BPF) 513. The ASE light source 511 generates broadband spontaneous emission light. The optical bandpass filter 513 transmits only ASE light in the wavelength band used as monitoring light 701 (monitoring light band). The WSS512 shown in Figure 2 may be used as the optical bandpass filter 513.

[0042] In this embodiment, the optical bandpass filter 513 is configured with a continuous band including wavelengths λ1 and λ2 as its transmission band. This transmission band does not overlap with the wavelength bands of the signal lights 702 and 802. With this configuration, the monitoring device 101A transmits ASE light including wavelengths λ1 and λ2 as the monitoring light 701. The optical bandpass filters 253 provided in the optical repeaters 201 and 202 transmit only light of wavelength λ1 or λ2, respectively. Therefore, the monitoring light receiving unit 112 receives the monitoring light 701 with wavelength λ1 when the optical switch 301 has selected the first path, and receives the monitoring light with wavelength λ2 when the optical switch 301 has selected the second path. In other words, by using the monitoring device 101A, the control unit 113 can identify the active path by transmitting ASE light with the wavelength band of the monitoring light just once.

[0043] (Minimum configuration of the first embodiment) Figure 6 is a block diagram showing an example of the minimum configuration of the optical submarine system 1 according to the first embodiment. The effect of being able to identify the active path in an optical transmission system with redundant paths can also be obtained by the optical submarine system 1A shown in Figure 6.

[0044] The optical submarine system 1A includes a monitoring device 101 (monitoring means) and a route group 750. The monitoring device 101 is responsible for transmitting and receiving monitoring light to and from the route group 750. The route group 750 has a configuration that allows one active route to be selected from the routes of a plurality of optical transmission paths arranged in parallel.

[0045] The path group 750 includes two loopback circuits 250 and optical switches 301 and 302. The two loopback circuits 250 are connected to the optical switches 301 and 302 by optical transmission lines. Optical switch 301 acts as a first optical switching means, connecting one end of the multiple paths to the monitoring device 101. Optical switch 302 acts as a second optical switching means, selecting one of the other ends of the multiple paths. That is, optical switches 301 and 302 select the active path from the multiple paths. The loopback circuits 250 are installed in each of the multiple paths and act as loopback means, looping back only monitoring light of different wavelengths from each other.

[0046] As illustrated in Figure 2, the monitoring device 101 comprises a monitoring light transmitting unit 111, a monitoring light receiving unit 112, and a control unit 113. The monitoring light transmitting unit 111 is a monitoring light transmitting means that outputs monitoring light to the optical switch 301. The monitoring light receiving unit 112 is a monitoring light receiving means that receives monitoring light from the optical switch 302 and outputs wavelength information indicating the wavelength of the received monitoring light. The control unit 113 identifies the loopback circuit 250 to which the received monitoring light is looped back, and identifies the path on which the identified loopback circuit 250 is located as the active path. Such a control unit 113 can be called a control means. Here, the control unit 113 identifies the loopback circuit 250 to which the received monitoring light is looped back, based on the wavelength information and loopback information that records the wavelengths of the monitoring light looped back by the multiple loopback circuits 250.

[0047] The optical submarine system 1A and monitoring device 101, having such a configuration, also have the effect of being able to identify the currently used path in an optical transmission system with redundant paths.

[0048] (Second embodiment) Figure 7 is a block diagram showing an example configuration of the optical submarine system 2 of the second embodiment. Compared to the optical submarine system 1 of Figure 1, the optical submarine system 2 includes optical repeaters 201A and 202A, as well as a monitoring device 102 and an optical multiplexer / demultiplexer 412. The monitoring device 102 and the optical multiplexer / demultiplexer 412 provide the same functions as the monitoring device 101 and the optical multiplexer / demultiplexer 411, respectively, on the optical switch 302 side. That is, the monitoring device 102 outputs monitoring light to the optical repeaters 201A and 202A and receives the monitoring light looped back in them. Based on the wavelength of the looped-back monitoring light, the monitoring device 102 identifies the optical repeater to which the monitoring light was looped back. The optical multiplexer / demultiplexer 412 combines and separates the monitoring light transmitted and received by the monitoring device 102 and the signal light transmitted and received by the optical transceiver 402.

[0049] Monitoring device 101 and monitoring device 102 are connected by a data line 801. The data line 801 may also be a line that enables communication between monitoring device 101 and monitoring device 102 via a first or second route. The data line 801 transmits and receives data indicating the route identification result between monitoring devices 101 and 102.

[0050] Figure 8 is a block diagram showing an example configuration of the optical repeater 201A. The optical repeater 201A includes loopback circuits 250 and 250A, and a repeater circuit 280. As described in the first embodiment, the loopback circuit 250 loops back the monitoring light input from the fiber pair 21. In contrast, the loopback circuit 250A loops back the monitoring light input from the fiber pair 31 to the fiber pair 31 using a configuration and procedure similar to that of the loopback circuit 250. Specifically, the optical coupler 251A branches the light input from the optical fiber 31B to the optical repeater 201A. The optical bandpass filter 253A transmits only light of a predetermined wavelength. The optical coupler 252A combines the signal light transmitted from the optical fiber 21A to the optical fiber 31A with the light input from the optical bandpass filter 253A and outputs it to the optical fiber 31A.

[0051] An optical repeater 201A with this configuration can loop back monitoring light transmitted from monitoring device 101 located on the optical switch 301 side to monitoring device 101. Furthermore, the optical repeater 201A can loop back monitoring light transmitted from monitoring device 102 located on the optical switch 302 side to monitoring device 102.

[0052] Optical repeater 202A has the same configuration as optical repeater 201A. However, the transmission wavelength of the optical bandpass filter 253 of optical repeater 202A is different from the transmission wavelength of the optical bandpass filter 253 of optical repeater 201A. Also, the transmission wavelength of the optical bandpass filter 253A of optical repeater 202A is different from the transmission wavelength of the optical bandpass filter 253A of optical repeater 201A.

[0053] Monitoring devices 101 and 102 each identify the path selected by optical switch 301 or 302 based on the wavelength of the looped monitoring light. Therefore, the optical submarine system 2 of this embodiment has the effect of being able to identify the selected path for both optical switches 301 and 302. Monitoring devices 101 and 102 may each transmit monitoring light at different time periods. Monitoring devices 101 and 102 transmit their respective monitoring light at time periods that do not overlap. This suppresses, for example, the misidentification of the active line due to monitoring light transmitted by monitoring device 101 being received by monitoring device 102. The transmission wavelengths of the optical bandpass filters 253 and 253A provided in the optical submarine system 2 may all be different. In this case, even if monitoring devices 101 and 102 transmit monitoring light simultaneously, monitoring devices 101 and 102 can identify the optical repeater to which the received monitoring light was looped back.

[0054] Furthermore, the identification results may be shared between monitoring devices 101 and 102 using the data line 801. By sharing the identification results, monitoring devices 101 and 102 can determine whether the paths they each identified match. If the path identified by monitoring device 101 matches the path identified by monitoring device 102, monitoring device 101 or 102 can determine that both optical switch 301 and optical switch 302 have been switched to configure the same path. If the paths identified by monitoring device 101 and monitoring device 102 do not match, monitoring device 101 or 102 can determine that optical switch 301 or optical switch 302 may have been mistakenly switched to select a different path. In other words, the optical submarine system 2 of this embodiment can detect abnormalities that occur when optical switch 301 or 302 operates differently than expected.

[0055] (Third embodiment) Figure 9 is a block diagram showing an example configuration of the optical submarine system 3 according to the third embodiment. The optical submarine system 3 differs from the optical submarine system 2 in that n paths are arranged in parallel. n is an integer of 2 or more. Figure 7 of the second embodiment corresponds to the case where n=2. Also, in Figure 9, the optical transceivers 401, 402 and optical multiplexers / demultiplexers 411, 412 from Figure 7 are omitted.

[0056] The optical submarine system 3 has a first to nth path between optical switches 311 and 312. The optical switches 311 and 312 are connected by one of the first to nth paths. Optical repeaters 201A, 202A, ... 20nA represent n optical repeaters arranged in parallel. Each of these optical repeaters has a configuration similar to optical repeater 201A described in Figure 8.

[0057] Figure 10 is a table showing examples of transmission wavelengths for optical bandpass filters 253 and 253A in this embodiment. The transmission wavelength of optical bandpass filter 253 differs for each optical repeater. The transmission wavelengths of the optical bandpass filter 253 in optical repeaters 201A-20nA are λ11-λ1n, and λ11-λ1n are different from each other. Also, the transmission wavelengths of optical bandpass filters 253A are λ21-λ2n, and λ21-λ2n are different from each other. Therefore, for example, if the wavelength of the monitoring light received by monitoring device 101 is λ13 and the wavelength of the monitoring light received by monitoring device 102 is λ23, then optical switches 311 and 312 can both be determined to have selected the third path. Furthermore, if different paths are identified by optical switch 301 and optical switch 302, monitoring device 101 or 102 may determine that there is a malfunction in at least one of optical switches 301 and 302. Furthermore, λ11-λ1n and λ21-λ2n may all be different.

[0058] Thus, the optical submarine system 3 of this embodiment can identify the path selected by the optical switch even when three or more paths are arranged in parallel. This is because the wavelength of the looped-back monitoring light is different for each of the parallel-arranged optical repeaters. As a result, the monitoring devices 101 and 102 can identify the optical repeater to which the monitoring light was looped back, based on the wavelength of the looped-back monitoring light.

[0059] (Fourth embodiment) Figure 11 shows an example configuration of the optical submarine system 4 according to the fourth embodiment of the present invention. The optical submarine system 4 differs from the optical submarine system 2 in Figure 7 in that it includes two path groups 751 and 752. In Figure 11, the path group including the first and second paths is referred to as path group 751, and the path group including the third and fourth paths is referred to as path group 752. Also, in Figure 11, the optical transceivers 401, 402, optical multiplexers 411, 412, and data line 801 are omitted from the description. Furthermore, optical fiber pairs connecting elements such as optical repeaters and optical switches are represented using thick straight lines with arrows at both ends.

[0060] Route group 751 was described in the first embodiment. Route group 752 is arranged between the optical switch 302 and the monitoring device 102. Route group 752 includes optical switches 303 and 304, and optical repeaters 201B and 202B.

[0061] Optical switches 303 and 304, and optical repeaters 201B and 202B, respectively, have the same functions as optical switches 301 and 302, and optical repeaters 201A and 202A, as described above. That is, optical switches 301 and 302 operate to select either the first or second path, and optical switches 303 and 304 operate to select either the third or fourth path. In this way, optical switches 301 and 302 select one path from the path group 751 as the active system. Optical switches 303 and 304 also select one path from the path group 752 as the active system.

[0062] Figure 12 is a table showing examples of transmission wavelengths for optical bandpass filters 253 and 253A in each optical repeater in this embodiment. Optical bandpass filter 253 is provided in the loopback circuit 250 to loop back the monitoring light transmitted by the monitoring device 101. Optical bandpass filter 253 is provided in the loopback circuit 250A to loop back the monitoring light transmitted by the monitoring device 102.

[0063] The optical bandpass filters 253 in optical repeaters 201A, 202A, 201B, and 202B have transmission wavelengths of λ11, λ12, λ13, and λ14, respectively, with λ11-λ14 being distinct from each other. The optical bandpass filter 253A has transmission wavelengths of λ21-λ2n, with λ21-λ2n being distinct from each other. Route group 751 loops back monitoring light with wavelengths λ11, λ12, λ21, and λ22. Route group 752 loops back monitoring light with wavelengths λ13, λ14, λ23, and λ24. By setting the transmission wavelengths of optical bandpass filters 253 and 253A as shown in Figure 12, even when multiple route groups are connected in series, the optical repeater that looped back the monitoring light can be identified in each route group.

[0064] As shown in the lower part of Figure 11, the monitoring light with wavelength λ11 transmitted by monitoring device 101 is looped back by optical repeater 201A, and the monitoring light with wavelength λ12 is looped back by optical repeater 202A. In addition, the monitoring light with wavelength λ13 transmitted by monitoring device 101 is looped back by optical repeater 201B, and the monitoring light with wavelength λ14 is looped back by optical repeater 202B. For example, if the wavelengths of the monitoring light received by monitoring device 101 are λ11 and λ14, monitoring device 101 can determine that the first path has been selected by optical switches 301 and 302, and the fourth path has been selected by optical switch 303. In this case, if the wavelengths of the monitoring light received by monitoring device 102 are λ21 and λ24, monitoring device 102 can determine that the fourth path has been selected by optical switches 303 and 304, and the first path has been selected by optical switch 302. Therefore, it can be determined that the optical switches 301-304 are operating to select the first and fourth paths.

[0065] On the other hand, if the wavelengths of the monitoring light received by monitoring devices 101 and 102 indicate that different parallel-connected paths have been selected, it is possible that one of the optical switches is not switching correctly. For example, if monitoring device 101 transmits monitoring light and receives monitoring light with wavelength λ13, monitoring device 101 will determine that optical switch 303 has selected the third path. However, if monitoring device 102 transmits monitoring light and receives monitoring light with wavelength λ24, monitoring device 102 will determine that optical switch 304 has selected the fourth path. In such a case, it is possible that at least one of optical switches 303 and 304 is not functioning correctly.

[0066] Thus, the optical submarine system 4 can identify the selected path in each path group, even when path groups 751 and 752 are connected in series. This is because, even between different path groups, the wavelength of the monitoring light looped back in the same direction differs for each optical repeater. As a result, monitoring devices 101 and 102 can identify the path group and optical repeater to which the monitoring light was looped back by measuring the wavelength of the looped-back monitoring light.

[0067] (Modification of the fourth embodiment) Figure 13 illustrates a modified example of the fourth embodiment, the optical submarine system 4A. The configuration of each part of the optical submarine system 4A is the same as that of the optical submarine system 4 in Figure 11. However, the transmission wavelengths of the optical bandpass filters 253 and 253A are different from those of the optical submarine system 4.

[0068] Figure 14 is a table showing examples of transmission wavelengths for the optical bandpass filters 253 and 253A in each optical repeater in this modified example. The transmission wavelength of the optical bandpass filter 253 in optical repeaters 201A and 201B is λ11, and the transmission wavelength of the optical bandpass filter 253A in optical repeaters 201A and 201B is λ21. Similarly, the transmission wavelength of the optical bandpass filter 253 in optical repeaters 202A and 202B is λ12, and the transmission wavelength of the optical bandpass filter 253A in optical repeaters 202A and 202B is λ22. In other words, in this embodiment, both path groups 751 and 752 loop back one of the monitoring lights with wavelengths λ11, λ12, λ21, and λ22.

[0069] As will be described later, in this modified example, the round-trip time of the monitoring light is used to identify the group of paths through which the monitoring light was looped back. The standard round-trip time TR1 in Figure 14 is the standard round-trip time from the transmission time of the monitoring light to the reception time of that monitoring light in the monitoring device 101. The standard round-trip time TR2 is the standard time from the transmission time of the monitoring light to the reception time of that monitoring light in the monitoring device 102. TR1 and TR2 may be determined based on the design distance between the monitoring devices 101 and 102 and each optical repeater, and the propagation speed of the monitoring light. TR1 and TR2 do not need to be exact values. TR1 and TR2 only need to be accurate enough to determine which of TR1 and TR2 the measured round-trip time T0 of the monitoring light is closer to.

[0070] In this modified example, the wavelengths of the monitoring light looped back from path group 751 and the monitoring light looped back from path group 752, as received by monitoring device 101, are both λ11 or λ12. Similarly, the wavelengths of the monitoring light looped back from path group 751 and the monitoring light looped back from path group 752, as received by monitoring device 102, are both λ21 or λ22. Therefore, for example, if the monitoring light is looped back by optical repeaters 201A and 201B, monitoring device 101 will only receive the monitoring light with wavelength λ11. Consequently, monitoring devices 101 and 102 need to know which path group's optical repeater the received monitoring light was looped back at.

[0071] Therefore, in this modified example, monitoring devices 101 and 102 transmit pulsed light as monitoring light. The pulsed light may be a single pulse or an intermittent pulse. The control unit 113 of monitoring devices 101 and 102 measures the round-trip time T0 of the transmitted monitoring light and determines, based on the round-trip time T0, whether the monitoring light was looped back in path group 751 or 752.

[0072] For example, the monitoring light transmitting unit 111 illustrated in Figure 2 transmits monitoring light as pulsed light at a certain time T1 and notifies the control unit 113 of the time T1. The monitoring light receiving unit 112 notifies the control unit 113 of the time T2 at which the monitoring light was received. The control unit 113 calculates the round-trip time T0 of the monitoring light as T2-T1. The control unit 113 compares the received round-trip time T0 of the monitoring light with the standard round-trip times TR1 and TR2 corresponding to the wavelength of the monitoring light and determines whether T0 is closer to TR1 or TR2.

[0073] For example, if monitoring device 101 receives monitoring light with wavelength λ11, the monitoring light will have been looped back to at least one of optical repeaters 201 and 201B. If the round-trip time T0 of the received pulsed light is closer to T11a than to T11b, the control unit 113 of monitoring device 101 can determine that the monitoring light was looped back at optical repeater 201A. If T0 is closer to T11b than to T11a, it can determine that the monitoring light was looped back at optical repeater 201B. Furthermore, if both monitoring light with T0 closer to T11a and monitoring light with T0 closer to T11b are received, the control unit 113 may determine that the monitoring light was looped back at optical repeaters 201A and 201B. The same procedure can be used to identify the optical repeater to which the monitoring light was looped back when monitoring device 102 transmits pulsed light with wavelengths λ21 and λ22 as monitoring light.

[0074] In this case, to transmit one pulse of monitoring light and detect the two monitoring lights that have been looped back in each of the two path groups, it is preferable to shorten the pulse length of the monitoring light so that the reception times of the two monitoring light pulses received by the monitoring device 101 do not overlap. Such a pulse length can be easily set by a general calculation using the difference in the standard round-trip times of two typical path groups.

[0075] As explained above, the optical submarine system 4A, like the optical submarine system 4, can identify the selected path in each path group even when path group 751 and path group 752 are connected in series. Furthermore, the optical submarine system 4A can identify the path group to which the monitoring light has been looped back by measuring the round-trip time of the monitoring light. For this reason, in the optical submarine system 4A, the wavelength of the monitoring light looped back in path group 751 and the wavelength of the monitoring light looped back in path group 752 may overlap. Consequently, the optical submarine system 4A has the effect of reducing the number of wavelengths of the monitoring light compared to the optical submarine system 4, and thereby expanding the bandwidth of the signal light that transmits user data.

[0076] In the embodiments described above, a submarine optical system was used as an example. However, it is clear that the configurations of each embodiment can also be applied to land-based optical transmission systems. Furthermore, any of the effects described above can be obtained by appropriately combining the configurations of each embodiment. For example, the configuration of the submarine optical system 3 with n paths, illustrated in Figure 9, can also be applied to the submarine optical systems 4 and 4A illustrated in Figures 11 and 13.

[0077] Furthermore, in each of the embodiments described above, the relay circuit 280 is not essential, and the effects of each embodiment can be obtained even if each optical repeater is equipped only with a loopback circuit.

[0078] The embodiments of the present invention may also be described as follows, but are not limited thereto.

[0079] [Note 1] A set of paths from which one active path can be selected from multiple optical transmission paths arranged in parallel, A monitoring means for transmitting and receiving monitoring light between the aforementioned group of paths, Equipped with, The aforementioned group of routes is Loopback means, which are arranged in each of the aforementioned multiple paths and loop back only monitoring light of different wavelengths from each other, A first optical switching means that connects one of the ends of the plurality of paths to the monitoring means, A second optical switching means for selecting one of the other ends of the plurality of paths, Equipped with, The monitoring means is A monitoring light transmitting means that outputs the monitoring light to the first optical switching means, A monitoring light receiving means that receives the monitoring light from the first light switching means and outputs wavelength information indicating the wavelength of the received monitoring light, The system includes control means that, based on the wavelength information and loopback information recording the wavelength of the monitoring light looped back by the plurality of loopback means, identifies the loopback means to which the received monitoring light was looped back, and identifies the path on which the identified loopback means is located as the active path. Route identification system.

[0080] [Note 2] Each of the aforementioned plurality of loopback means is: A first optical transmission path connected to the first optical switching means and a second optical transmission path connected to the second optical switching means are connected, Each of the aforementioned loopback means is A first optical coupler that branches the light input from the first optical transmission path, One of the light input from the branched first optical transmission path is input, and an optical filter that transmits only the monitoring light of a predetermined wavelength is provided, A second optical coupler that combines the light input from the optical filter and the light input from the second optical transmission path, and outputs the combined light to the first optical transmission path, Equipped with, Route identification system as described in Appendix 1.

[0081] [Note 3] The system comprises a first group of paths and a second group of paths, each being a different group of paths. The second optical switching means provided in the first path group and the first optical switching means provided in the second path group are connected, The wavelengths of the monitoring light looped back by the loopback means included in the first path group and the second path group are all different. Route identification system as described in Appendix 1 or 2.

[0082] [Note 4] The control means identifies a path where the loopback means for looping back the monitoring light of a wavelength corresponding to the wavelength information is located as the active path, as described in any one of the appendices 1 to 3.

[0083] [Note 5] The system comprises a first group of paths and a second group of paths, each being a different group of paths. The second optical switching means provided in the first path group and the first optical switching means provided in the second path group are connected, The monitoring means is The aforementioned monitoring light is transmitted as pulsed light, The round-trip time of the pulsed light is measured, The standard round-trip time of the monitoring light between each of the loopback means included in the first and second path groups and the monitoring means is recorded in the loopback information. The group of paths through which the received monitoring light is looped back is identified based on the standard round-trip time and the measured round-trip time. Route identification system as described in Appendix 1 or 2.

[0084] [Note 6] The control means is The group of routes on which the loopback means having the standard round-trip time corresponding to the measured round-trip time is arranged is identified as the group of routes to be used as the current route. The route identification system described in Appendix 5, which identifies as the active route a route among the identified group of routes in which the loopback means that loops back the monitoring light of a wavelength corresponding to the wavelength information is located.

[0085] [Note 7] The loopback means is a route identification system as described in any one of the appendices 1 to 6, provided inside an optical repeater located in each of the plurality of paths.

[0086] [Note 8] The routing system described in either item 1 or 6, wherein the loopback means is connected to the outside of the optical repeaters located in each of the plurality of paths.

[0087] [Note 9] A monitoring light transmission means that outputs monitoring light to an optical transmission path, A monitoring light receiving means that receives the monitoring light and outputs wavelength information indicating the wavelength of the received monitoring light, A control means that has loopback information recording the wavelength of the monitoring light looped back by a plurality of loopback means on the optical transmission path, identifies the loopback means to which the received monitoring light was looped back based on the wavelength information and the loopback information, and identifies the path on which the identified loopback means is located as the active path, A monitoring device equipped with the following features.

[0088] [Note 10] A path identification method used in an optical transmission system comprising: a group of paths capable of selecting one active path from a plurality of parallel-arranged optical transmission paths; and monitoring means for sending and receiving monitoring light to and from the group of paths, One of the ends of the aforementioned plurality of paths is connected to the monitoring means by the first optical switching means, The other end of the aforementioned plurality of paths is selected by the second optical switching means, The monitoring light is output to the first optical switching means, Only the monitoring light of different wavelengths is looped back by the loopback means of each of the multiple paths. The monitoring light is received from the first optical switching means, and wavelength information indicating the wavelength of the received monitoring light is output. Based on the wavelength information and loopback information recording the wavelength of the monitoring light looped back by the plurality of loopback means, the loopback means to which the received monitoring light was looped back is identified. The path on which the identified loopback means is located is identified as the active path. Route identification method.

[0089] [Note 11] A method for identifying a route as described in Appendix 10, used in the optical transmission system comprising a first route group and a second route group, each being a different route group, The second optical switching means provided in the first path group is connected to the first optical switching means provided in the second path group, The wavelengths of the monitoring light looped back by the loopback means included in the first path group and the second path group are all different. Route identification method.

[0090] [Note 12] A path identification method according to Appendix 10 or 11, which identifies a path in which the loopback means for looping back the monitoring light of a wavelength corresponding to the wavelength information is arranged as the active path.

[0091] [Note 13] A method for identifying a route as described in Appendix 10, used in the optical transmission system comprising a first route group and a second route group, each being a different route group, The second optical switching means provided in the first path group is connected to the first optical switching means provided in the second path group, The standard round-trip time of the monitoring light between each of the loopback means included in the first and second path groups and the monitoring means is recorded in the loopback information. The aforementioned monitoring light is transmitted as pulsed light, The round-trip time of the pulsed light is measured, The group of paths through which the received monitoring light is looped back is identified based on the standard round-trip time and the measured round-trip time. Route identification method as described in Appendix 10.

[0092] [Note 14] The group of routes on which the loopback means having the standard round-trip time corresponding to the measured round-trip time is arranged is identified as the group of routes to be used as the active route. Among the loopback means arranged in the identified group of paths, the path in which the loopback means that loops back the monitoring light of a wavelength corresponding to the wavelength information is arranged is identified as the active path. Route identification method as described in Appendix 13.

[0093] [Note 15] The monitoring light is output to the optical transmission path. Upon receiving the aforementioned monitoring light, Wavelength information indicating the wavelength of the received monitoring light is output. Loopback information is obtained by recording the wavelength of the monitoring light looped back by a plurality of loopback means on the optical transmission path, and based on the wavelength information, the loopback means to which the received monitoring light was looped back is identified, and the path on which the identified loopback means is located is identified as the active path. A method for controlling a monitoring device.

[0094] [Note 16] Procedure for outputting monitoring light to the optical transmission path, The procedure for receiving the aforementioned monitoring light, A procedure for outputting wavelength information indicating the wavelength of the received monitoring light, A procedure for recording the wavelength of the monitoring light looped back by multiple loopback means on the optical transmission path as loopback information, A procedure for identifying the loopback means to which the received monitoring light was looped back, based on the loopback information and the wavelength information. A procedure for identifying the route on which the identified loopback means is located as the active route, A recording medium containing a program to be executed by the computer of a monitoring device.

[0095] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. Various modifications to the configuration and details of the present invention can be made that can be understood by those skilled in the art within the scope of the present invention.

[0096] For example, the functions of monitoring devices 101 and 102 may be programmed. Monitoring devices 101 and 102 may then implement some or all of their functions by having a computer execute the program. The computer may be, for example, a logic device, a central processing unit, or a digital signal processing unit. The computer may be located in the control unit 113. The program may also be recorded on a fixed, non-temporary recording medium that is readable by the computer. The recording medium may be, for example, a flexible disk, a fixed magnetic disk, or a non-volatile semiconductor memory. The program may be distributed to monitoring devices 101 and 102 via a network.

[0097] Furthermore, the configurations described in each embodiment are not necessarily mutually exclusive. The operation and effects of the present invention may be achieved by a configuration that combines all or part of the above-described embodiments. [Explanation of symbols]

[0098] 1, 1A, 2, 3, 4, 4A Optical Submarine System 11, 12, 21, 22, 31, 32, 114 fiber pairs 21A, 21B, 31A, 31B optical fibers 101, 101A, 102 Monitoring device 111, 111A Monitoring Optical Transmitter 112 Monitoring light receiving unit 113 Control Unit 201, 201A, 201B, 202, 202A, 202B Optical Repeater 212 light 250, 250A loopback circuit 251, 251A, 252, 252A Optical Couplers 253, 253A Optical Bandpass Filter (BPF) 280 relay circuits 301-304, 311, 312 Optical switches 401, 402 Optical Transceivers 411, 412 Optical multiplexer / demultiplexer 511 ASE light source 513 Optical bandpass filter 701 Surveillance light 702, 802 signal light 721 Downlight 821 Upward light Routes 750, 751, and 752 801 Data Line

Claims

1. A set of paths from which one active path can be selected from multiple optical transmission paths arranged in parallel, The system includes monitoring means for transmitting and receiving monitoring light to and from the aforementioned group of paths, The aforementioned group of routes is Multiple loopback means are arranged in each of the paths of the aforementioned multiple optical transmission lines and loop back only monitoring light of different wavelengths from each other, A first optical switching means that connects one of the paths of the plurality of optical transmission lines to the monitoring means, The system includes a second optical switching means for selecting one of the other ends of the paths of the plurality of optical transmission lines, The monitoring means is A monitoring light transmitting means that outputs the monitoring light to the first optical switching means, A monitoring light receiving means that receives the monitoring light from the first light switching means and outputs wavelength information indicating the wavelength of the received monitoring light, A route identification system comprising: a control means that identifies the loopback means to which the received monitoring light was looped back, based on the wavelength information and loopback information which records the wavelength of the monitoring light that the plurality of loopback means loop back, and identifies the path to which the identified loopback means is located as the active path.

2. One end of each of the plurality of loopback means is connected to the other end of a first optical fiber pair that forms part of the plurality of optical transmission paths, one end of which is connected to the first optical switching means. The other end of each of the plurality of loopback means is connected to the other end of a second optical fiber pair that forms part of the plurality of optical transmission paths, one end of which is connected to the second optical switching means. Each of the aforementioned loopback means is It comprises an optical filter, a first optical coupler, and a second optical coupler. The first optical coupler splits the light input from the first optical fiber pair, outputs one of the split light to the optical filter, and outputs the other light to one of the optical fibers of the second optical fiber pair. The optical filter receives one of the light signals split at the first optical coupler, and the optical filter transmits only the monitoring light of a predetermined wavelength. The path identification system according to claim 1, wherein the second optical coupler couples the light input from the optical filter with the light input from the other optical fiber of the second optical fiber pair, and outputs the coupled light to the other optical fiber of the first optical fiber pair.

3. The system comprises a first group of paths and a second group of paths, each being a different group of paths. The second optical switching means provided in the first path group and the first optical switching means provided in the second path group are connected, The route identification system according to claim 1 or 2, wherein the wavelengths of the monitoring light that each of the plurality of loopback means included in the first route group and the second route group loops back are all different.

4. The path identification system according to any one of claims 1 to 3, wherein the control means identifies as the active path a path in which a loopback means that loops back the monitoring light of a wavelength corresponding to the wavelength information is arranged among the plurality of loopback means.

5. The system comprises a first group of paths and a second group of paths, each being a different group of paths. The second optical switching means provided in the first path group and the first optical switching means provided in the second path group are connected, The monitoring means is The aforementioned monitoring light is transmitted as pulsed light, The round-trip time of the pulsed light is measured, The standard round-trip time of the monitoring light between each of the plurality of loopback means included in the first path group and the second path group and the monitoring means is recorded in the loopback information. A path identification system according to claim 1 or 2, which identifies the group of paths through which the received monitoring light is looped back, based on the standard round trip time and the measured round trip time.

6. The control means is Among the plurality of loopback means, the group of routes in which the loopback means having the standard round-trip time corresponding to the measured round-trip time is arranged is identified as the group of routes to be used as the active route. The route identification system according to claim 5, wherein, among the plurality of loopback means arranged in the identified group of routes, the route in which the loopback means that loops back the monitoring light of a wavelength corresponding to the wavelength information is arranged is identified as the active route.

7. The route identification system according to any one of claims 1 to 6, wherein each of the plurality of loopback means is provided inside an optical repeater located in each of the paths of the plurality of optical transmission lines.

8. The routing system according to any one of claims 1 to 6, wherein each of the plurality of loopback means is connected to the outside of an optical repeater located in each of the paths of the plurality of optical transmission lines.

9. A monitoring light transmission means that outputs monitoring light to an optical transmission path, A monitoring light receiving means that receives the monitoring light and outputs wavelength information indicating the wavelength of the received monitoring light, A monitoring device comprising: loopback information which records the wavelength of the monitoring light looped back by a plurality of loopback means on the optical transmission path; and control means which, based on the wavelength information and the loopback information, identifies the loopback means to which the received monitoring light was looped back, and identifies the path on which the identified loopback means is located as the active path.

10. A path identification method used in an optical transmission system comprising: a group of paths capable of selecting one active path from a plurality of parallel-arranged optical transmission paths; and monitoring means for sending and receiving monitoring light to and from the group of paths, One end of the paths of the plurality of optical transmission lines is connected to the monitoring means by the first optical switching means, The second optical switching means selects one of the other ends of the paths of the plurality of optical transmission lines, The monitoring light is output to the first light switching means by the monitoring means. Only the monitoring light of different wavelengths is looped back by each loopback means along the path of the plurality of optical transmission lines. The aforementioned monitoring means, The monitoring light is received from the first optical switching means, and wavelength information indicating the wavelength of the received monitoring light is output. Based on the wavelength information and loopback information recording the wavelength of the monitoring light looped back by the plurality of loopback means, the loopback means to which the received monitoring light was looped back is identified. A route identification method for identifying the route on which the identified loopback means is located as the active route.

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