JP2004254339A - Communication network and communication network node device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compose a ring system in which using efficiency of ET path is high during trouble or maintenance time, composition of an alternative route with a little delay difference is possible, high speed trouble recovery is possible even for an ultra long distance ring according to the trouble condition, and reliability at trouble time is high. <P>SOLUTION: In a condition that an ET (Extra Traffic, Stand-by Access) path of wave length λ1 is composed between a node 109 to a node 107 on a stand-by ring 104, if a disconnection trouble occurs in an optical fiber of an active ring 101 between a node 106 and the node 109, a supervisory control device in the node 107 detects the trouble in the optical path 601, carries out messaging to relating nodes, and separates the ET path from the node 109 to the node 107 in order to carry out separation of a short path (stand-by path 602) on the standby ring 104. If the node 107 confirms separation of the ET path, it requests sending of a main signal light to the node 106 via the stand-by ring 104. The node 106 changes over an optical switch to send the light also to the stand-by ring 104 in accordance with the request. In this method, stand-by resources which are used in trouble or maintenance time, can be used effectively used, and a system in which the delay difference of active path and the stand-by path during maintenance time can be composed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a communication network using optical communication or the like, and relates to a network configuration, a node device, a failure recovery method, and a maintenance method.

  In order to respond to the demand for large-capacity communication, an optical communication network employs means for increasing the capacity in one optical transmission line by performing wavelength multiplexing. In order to operate such a network efficiently, a communication network node switches an optical ADM (Add / Drop Multiplexers) node that separates and inserts an optical signal by switching the wavelength of the optical signal in a ring topology. Optical ADM ring systems that are configured and connected are being considered.

  As an optical ADM ring system, a four-fiber bidirectional path / switching ring (hereinafter abbreviated as Bi-Path system) has been studied (for example, see Non-Patent Document 1).

  In the following description, separation means outputting a signal obtained by decomposing a signal transferred in a network node to another communication device in the own node. Insertion means that, in a network node, a signal from another communication device in the own node is multiplexed into a transmission signal and transmitted to another node. Passing means that some or all of the transmitted signals are not separated or inserted into other communication devices in the own node, and wavelengths or time slots are not replaced as they are, or are spatially connected. This means that transmission is performed to another node by changing the wavelength or changing the time slot. Also, here, an optical path is defined as a period from a time when an electric signal is converted into an optical signal at a certain node and sent to another node until the electric signal is converted again into an electric signal. Hereinafter, one wavelength corresponds to the optical path.

  FIG. 21 is a block diagram showing the above conventional method. In FIG. 21, reference numerals 2101 and 2103 denote working optical rings for transmitting optical signals in opposite directions, reference numeral 2102 denotes a spare optical ring for transmitting optical signals in the opposite direction to 2101, and reference numeral 2104 denotes an optical signal in the opposite direction to 2103. Is a spare light ring.

  Wavelength multiplexed optical signals are transmitted in the optical fiber of each ring, and each wavelength constitutes an optical path. In the Bi-Path system, by switching a 1 × 2 optical switch provided in each node, it is possible to select whether to transmit light to the working ring or to the backup ring in the opposite direction to the optical transmission. As for the separated output, a configuration is used in which it is possible to select whether to separate and output the optical signal of the working ring or to separate the optical signal of the spare ring which is the reverse transmission. In FIG. 21, 1 × 2 switches 2110 and 2109 have the function.

  Next, the failure recovery operation in FIG. 21 will be briefly described. When the working optical path 2131 is configured using the wavelength λ1 between the node 2106 and the node 2107 and a failure of the fiber of the working optical ring 2101 occurs between the node 2106 and the node 2107, the working optical path is 2131 is detected, and a switching request is sent to the node 2106 that is the starting point of the optical path. Upon receiving this switching request, the node 2106 switches the optical switch 2110, configures a backup optical path 2132 that is reverse to the working optical path 2131, and performs a recovery by performing a detour.

  In the configuration of the Bi-Path system and the failure recovery method, exchange of control messages for failure recovery is performed mainly on the node 2107 on the ring as in the case of SONET line protection (for example, see Non-Patent Document 2). And the node 2106 may be exchanged several times, so that a high-speed failure recovery of, for example, about 50 msec can be performed. Also, if a loop-back switching method such as SONET line protection is used with light, it is necessary to consider the case where the ring is made around two rounds. Had to design the ring.

  However, in the Bi-Path system, since loopback switching is not performed, there is an advantage that the ring size can be set to a distance that allows optical transmission (see Non-Patent Document 1). As described above, the Bi-Path method has an advantage that it is possible to recover from a failure at a high speed, and that the size of the ring can be set to one time (not の) of the optical transmission distance.

  On the other hand, at present, communication capacity is increasing, and it is necessary to increase the number of available paths as much as possible. Therefore, it has been considered to accommodate low-priority communication in an optical path configured on a spare ring to increase the amount of communication that can be accommodated. Hereinafter, the working path configured on the backup ring in this manner is referred to as an ET path (ET: Extra traffic; also referred to as standby access).

  When the ET path is used, when no failure occurs, the bandwidth available in the entire system increases, and the use efficiency of the ring system increases. However, since the ET path is a communication with a low priority, if a failure occurs in the working optical path on the working ring, the failure recovery has priority, which hinders the failure recovery of the working optical path in the working ring. The ET path is cut off.

Shiragaki, Hemi: "Proposal of Bi-directional Path-switched Wavelength Division Multiplexing Self-Healing Ring" IEICE 1998 General Conference B-10-147, 1998. T-H Wu, “Fiber Network Service Survivability,” Artech house, 1992. K. Okamoto et al, “Fabrication of unequal channel spacing arrayed-waveguide demultiplexer modules,” Electron. Lett, 1995, vol. 31, no. 17, pp. 1464-1465 A. Himeno and M. Kobayashi, "4x4 Optical-Gate matrix switch," IEEE J. LightwaveTechnol., Vol. LT-3, no.2, April 1985.

  When a path between two nodes is considered on the Bi-Path ring, a clockwise path and a counterclockwise path can be considered. However, since a path with a smaller number of hops is usually used as a working path, ET is used. The path is configured on a spare ring with a large number of hops.

  However, when recovering from a failure, a detour path having a large number of hops is formed. Therefore, if an ET path using a wavelength of λm exists on this detour path, it is necessary to disconnect the ET path. In order to construct a backup path (λm) having a large number of hops, the number of ET paths that must be separated increases, and many users using the ET path suffer failures. That is, the use efficiency of the ET pass is poor.

  Also, during maintenance of the ring system (for example, replacement of an optical switch, etc.), a long detour path must be configured in the backup ring, and the total number of hops of the ET path that must be separated increases. Use efficiency becomes worse.

  Further, when the conventional technique is used, it is necessary to switch between a path having a large number of hops and a path having a small number of hops during maintenance. Therefore, when transmitting a signal, the delay difference is large, so that the instantaneous interruption time becomes long. In order to perform instantaneous interruption switching, it is necessary to use a memory to absorb the delay difference in order to equalize the delays of the two paths. However, since the delay difference is large, the required memory capacity is increased.

  Further, in the prior art, since the path is always switched to a path having a large number of hops, especially in an ultra-long distance ring, the number of nodes involved in the switching increases, and the failure recovery time increases.

  In addition, since the switching destination candidate is only a backup path having a large number of hops (a backup path transmitted in a direction opposite to the working path), the reliability at the time of failure is low.

  The object of the present invention is that the use efficiency of the ET path is high even at the time of failure or maintenance, a bypass route with a small delay difference can be configured, and even a super long-distance ring can perform high-speed failure recovery depending on the failure situation, An object of the present invention is to construct a highly reliable ring system in the event of a failure.

  A communication network according to the present invention comprises a plurality of communication node means for inserting and separating signals and a plurality of transmission paths, and the plurality of communication node means form the same network topology by connecting the plurality of transmission paths. Configuring at least a first ring, a second ring, a third ring, and a fourth ring to configure, wherein the first ring transmits a working signal either clockwise or counterclockwise; The second ring transmitting signals in the opposite direction to the first ring and the fourth ring transmitting signals in the same direction as the first ring as protection resources for working signals of the first ring. A spare resource is used in common among a plurality of working signals, and the working signal is transmitted in the third ring in a direction opposite to that of the first ring to serve as a spare resource for the working signal of the third ring. The fourth ring for transmitting a signal in the opposite direction to the third ring and the second ring spare resource for transmitting a signal in the same direction as the third ring are shared by a plurality of working signals. A first communication that inserts a signal at an i-th communication node of the plurality of communication nodes and terminates a signal at a j-th communication node via the first ring; A detour configured for the second ring or the fourth ring is used as a detour configured for path failure recovery or maintenance, and an m-th communication node of the plurality of communication nodes is used. The fourth ring is used as a bypass for fault recovery and maintenance of a second communication path for terminating a signal at an nth communication node means via the third ring through the third ring. Or the second ring A communication network using a detour, which, when the j-th communication node detects a failure in the first communication path, issues a request to switch the path of the first communication path to the i-th communication node. And when the i-th communication node receives this request, sends the signal of the first communication path to the spare resource, and after this transmission, the j-th communication node Means for performing a fault recovery by switching the first communication path to the spare resource, and when the n-th communication node means detects a fault in the second communication path, a route of the second communication path. Is transmitted to the m-th communication node means, and upon receiving the request, the m-th communication node means transmits a signal of the second communication path to the spare resource. And after the transmission, the n-th communication node means performs failure recovery by switching the second communication path to the spare resource.

Further, the communication network of the present invention comprises a plurality of communication node means for inserting and separating signals and a plurality of transmission paths, and the plurality of communication node means are connected to the same network by connecting the plurality of transmission paths. At least a first ring and a second ring are configured to form a topology, wherein the first ring transmits a working signal in either a clockwise or counterclockwise direction, and the second ring transmits a working signal in one direction. Transmitting a signal in a direction opposite to the first ring, wherein the first ring is a working signal group transmitted by the second ring and a working signal transmitted by the first ring within its transmission band. The second ring has a reserved resource band shared between the groups and transmitted in the opposite direction to the working signal, and the second ring has a working signal group transmitted by the first ring in the transmission band and the second signal ring. 2 By having a spare resource band shared among the working signal groups transmitted in the ring and transmitted in the opposite direction to the working signal, the i-th communication node means among the plurality of communication node means has As a detour configured for fault recovery and maintenance of a first communication path for inserting a signal and terminating the signal at a j-th communication node means via the first ring, A signal is inserted at the m-th communication node means of the plurality of communication node means using a communication path constituted by a protection resource band or a protection resource band of the first ring, and passes through the second ring. Then, as a bypass configured for fault recovery or maintenance of a second communication path terminating a signal at the n-th communication node means, a spare resource band of the first ring or a spare resource band of the second ring is used. Depending on resource bandwidth A communication network using a communication path formed, wherein the j-th communication node means detects a failure in the first communication path, and issues a request to switch a path of the first communication path. The request is sent to the i-th communication node means, and when the i-th communication node means receives the request, the signal of the first communication path is sent to the spare resource band. When the nth communication node detects a failure in the second communication path, the second communication node switches the first communication path to the spare resource band to perform failure recovery. To the m-th communication node means, and when the m-th communication node means receives the request, the signal of the second communication path is switched. The transmission is performed to the reserved resource band, and after the transmission, the n-th communication node unit switches the second communication path to the reserved resource band to perform failure recovery.
The communication network node device according to the present invention includes a plurality of or a single multiplexed signal input end for inputting a multiplexed signal, a plurality of or a single inserted input end for inserting a signal, and a multiplexed signal input to the multiplexed signal input end. A plurality of insertion / demultiplexing units each having a plurality or a single separation / output terminal for outputting a demultiplexed demultiplexed signal and a multiplexed signal output terminal for multiplexing and outputting the signal input to the insertion input terminal and the demultiplexed signal. Multiplexing means, plural or single external input terminals connected to other nodes, plural or single external output terminals connected to other nodes, plural or single switch means having plural output terminals, plural or single Singular joining means, plural or single signal input terminals, plural or single signal output terminals, plural or single signal monitoring means for monitoring signals input to the joining means, exchange of control information with other nodes The external input terminal is connected to a multiplexed signal input terminal of the insertion / separation / multiplexing means, and the multiplexed signal output end of the insertion / separation / multiplexing means is controlled by the control unit. An insertion input terminal of a plurality of the insertion / demultiplexing means connected to an external output terminal, the signal input terminal connected to the switch means, and the external output terminal connected to the multiplex signal output terminal connected to the same node; And an insertion input terminal of the insertion / demultiplexing unit connected to a node different from the same node is connected to an output terminal of the switch unit, and the external input terminal connected to the multiplex signal input terminal is connected to the same node. The separation / output terminals of the plurality of insertion / separation / multiplexing means and the separation / output terminals of the insertion / separation / multiplexing means connected to a node different from the same node are connected to the junction. Is connected to the signal output terminal, and the control means transmits and receives a monitoring result of a signal input to the merge means of the signal monitoring means and control information with the other node. When the switch is controlled based on the result and a failure is detected, a request to switch the path of the path is sent to the transmitting end node of the failed path, and the transmitting end node transmits a signal. Is transmitted to the standby resource band, and then the path is switched to the standby resource band to perform failure recovery.

  According to the failure recovery method of the present invention, a spare resource for configuring a bypass communication path is shared by a plurality of working signals, and a first communication network node device existing in a ring network having a communication path for control messages. A failure recovery method for communication from an input end to an output end of a second communication network node device present in the ring network, wherein the second communication network node device detects the communication failure, By using the communication path for the control message, the first communication network node device bypasses a path of a path connecting the first communication network node device and the second communication network node device. A request to switch to the path, and when the first communication network node device receives the request, the first communication network node device changes the signal of the path. The second communication network / node device switches the path to a detour using the spare resource to perform communication failure recovery after sending the packet to the bypass using the spare resource. When performing, if there is a low-priority communication path that hinders the configuration of the detour, disconnect the communication path before sending a signal to the detour, the detour is in the opposite direction to the path before the switch It is characterized by being around or in the same direction.

  In each node of the communication network according to the present invention, for example, an optical switch is connected so that the optical path on the clockwise working ring can be switched to either the clockwise backup ring or the counterclockwise backup ring.

  When a failure occurs in a transmission path or the like, the node that has detected the failure sends a failure recovery request to the transmission node, and the transmission node that has received the failure recovery request transmits a detour path configured on the clockwise backup ring to the left. If a fault can be recovered by a detour with a smaller number of hops among the detour paths configured on the surrounding spare ring (for example, when a fault occurs in only one fiber of the working ring), the fault recovery is performed accordingly. I do. If it is not possible to recover from a failure with a bypass path having a small number of hops (when a break failure occurs in a plurality of ring fibers at the same point), a method of recovering the failure using a bypass path having a large number of hops is used. Is used.

  These cases can be realized, for example, by first trying to recover from a failure with a small number of hops, and if the failure does not recover after a certain period of time, recovering the failure with a large number of hops It is. When performing maintenance, it is possible to switch to a detour with a small number of hops.

  According to the present invention, at the time of a failure, when the detour to the short path on the ring is possible, the failure recovery by the detour to the short path can be performed, and when the detour to the short path is impossible, the・ Since the failure recovery by detour to the path is performed, if the failure recovery by the short path is possible, the number of disconnecting the ET path is small, and the operation efficiency of the ET path at the time of the failure recovery is increased. . In addition, since it is possible to cope with maintenance such as replacement of parts by switching the short path, the number of ET paths to be disconnected is reduced, and the use efficiency of ET paths during maintenance is increased.

  Also, since the short path passes through the same path as the working path, detouring to the short path reduces the delay difference, reduces the instantaneous interruption time when switching, and minimizes the delay difference. The memory capacity required for switching is small.

  In addition, since the detour to the long path is not always performed at the time of recovery from a failure, if the recovery from the failure is possible by the detour to the short path, the number of nodes involved in switching is reduced, so the recovery time is reduced. Is done. This is particularly effective in very long haul rings.

  In addition, since there are two detour candidates at the time of failure, a short path and a long path, reliability is improved.

  FIG. 1 is a block diagram of a wavelength division multiplexing optical communication network according to a first embodiment of the present invention. In FIG. 1, reference numerals 105 to 109 denote optical communication network nodes. These nodes form four fiber rings by connecting the fibers to form a ring topology.

  101 and 103 represent working rings, and 102 and 104 represent spare rings. As shown by arrows in the drawing, the working rings 101 and 103 transmit optical signals in opposite directions, the working ring 101 and the protection ring 102 transmit optical signals in opposite directions, and the working ring 103 and the protection ring 104 The optical signal is transmitted in the reverse direction.

  From the node 107, the demultiplexed signals 111 and 112 are wavelength-division multiplexed and output. The demultiplexed signal 111 is an optical signal demultiplexed from the working ring 101 by wavelength division multiplexing, and the demultiplexed signal 112 is an optical signal demultiplexed from the working ring 103 by wavelength division demultiplexing (when no failure occurs). Further, insertion signals 121 and 122 are inserted into the node 107 as optical signals. The insertion signal 121 is an optical signal to be inserted into the working ring 101, and the insertion signal 122 is an optical signal to be inserted into the working ring 103 (when no failure occurs).

  Assuming that two waves λ1 and λ2 in the 1.5 μm band are used as main signal lights for transmitting data in the ring, for example, the insertion signals 121 and 122 are inserted into the working rings 101 and 103 which are opposite to each other. Therefore, it is possible to allocate an optical signal having a wavelength of λ1. In addition to the main signal light, a 1.3 μm band control signal light (wavelength: λs) is wavelength-multiplexed with the main signal light for transmission of control signals between adjacent nodes and transmitted. Even if the 1.3 μm band is not used as the control signal light, if it is not used for the main signal light and can be separated from the main signal light, another wavelength (for example, 1.51 μm (currently, However, since it is out of the band of the optical amplifier used for the main signal light, it cannot be used as the main signal light and can be used as the control signal light. In the above description, only the node 107 has been described, but other nodes also have similar functions.

  FIG. 2 is a block diagram showing the configuration of nodes 105 to 109 used in the wavelength division multiplexing optical communication network of the present invention shown in FIG. In FIG. 2, a node 200 has external signal light input terminals 202, 204, 214, and 216 and external signal light output terminals 201, 203, 213, and 215, and is connected to another node using an optical fiber. .

  In the following, the connection relationship with another node will be described by applying the node 200 to the position of the node 107 in FIG. 1 for convenience of description.

  The optical fiber of the working ring 101 is connected from the node 109 to the external input terminal 204, and is connected from the external output terminal 213 to the node 108. The optical fiber of the spare ring 102 is connected from the node 108 to the external input terminal 214, and is connected from the external output terminal 203 to the node 109. The optical fiber of the working ring 103 is connected from the node 108 to the external input terminal 216 and from the external output terminal 201 to the node 109. The optical fiber of the spare ring 104 is connected from the node 109 to the external input terminal 202, and is connected from the external output terminal 215 to the node 108.

  Reference numerals 230 and 231 denote optical switch units for switching for failure recovery and maintenance. Reference numerals 217 to 220 denote optical ADM units, which perform wavelength division multiplexing on the input wavelength-division multiplexed signal light in the 1.5 μm band to output an optical signal toward the branch output terminal, or wavelength division multiplexing input from the external input terminal. A part of the wavelength of the signal light is passed as it is, multiplexed with the optical signal from the insertion end, and output to the output end 201.

  Reference numerals 242, 244, 246, and 248 demultiplex optical signals input from external input terminals by control signal demultiplexers, and transmit wavelength-multiplexed main signal lights in the 1.5 μm band to the optical ADM units 217 to 220, respectively. The control signal light (λs) of 1.3 μm is input to the monitoring control device 221. As the control signal separator, it is possible to use a WDM coupler that separates the wavelength in the 1.3 μm band and the wavelength in the 1.5 μm band.

  Reference numerals 205 and 208 denote demultiplexing output terminals for outputting wavelength-multiplexed demultiplexed optical signals (λ1), and 209 and 212 denote demultiplexing input terminals for inputting one-wave optical signal (λ1). Other network devices such as an ATM switch (for example, see Non-Patent Document 2) are connected. Here, for the sake of simplicity, an example in which only one wave (λ1) is separated and input is shown, but the number of separated outputs and separated inputs may not be one. When there are a plurality of separated and inserted optical switches, a plurality of optical switch units may be arranged in parallel and connected to the optical ADM unit.

  Reference numerals 222 to 225 denote optical splitters, which tap (e.g., for 10% optical power) a part of the optical signal that has been wavelength-division-multiplexed and output from the optical ADM unit, and connected to the monitoring controller 221; Most of the optical signals (for example, 90% optical power) are output to the optical switch units 230 and 231.

  A monitoring controller 221 monitors the optical signals tapped at 222 to 225 and sends a switching control signal to the optical ADM units 217 to 220 and the optical switch units 230 and 231. The monitoring controller 221 includes an interface between an optical signal and an electric signal, a memory, a CPU, and the like. In FIG. 2, electric signals related to control in the node are indicated by broken lines.

  By installing an optical receiver at the input end of the monitoring controller 221, the bit error rate of the input optical signal is monitored to monitor the transmission quality of the optical signal (for example, using a SONET frame as the optical signal, It is possible to monitor the bit error rate by monitoring the B1 byte (see Non-Patent Document 2). Further, the monitoring controller 221 is connected to the optical switch units 230 and 231, and the optical ADM units 217 to 220, and controls switching between them based on information of the monitoring control unit.

  Control signal multiplexers 241, 243, 245, and 247 are respectively connected to the front stages of the external output terminals 201, 203, 213, and 215, and control signal light (1) transmitted from the monitoring controller 221 to another node is transmitted. .3 .mu.m band) and the main signal light (1.5 .mu.m band). As the control signal multiplexer, a WDM coupler can be used similarly to the control signal separator.

  By superimposing and separating the control signal light on the main signal light using the control signal separator and the control signal multiplexer, it is possible to exchange control signals with other nodes. Since the control signal light from the other node is input to the monitoring controller 221 and the optical signal monitoring result of the own node is also obtained, the switching based on the control information from the other node and the monitoring of the optical signal of the own node are performed. Both switching based on the result is possible.

  The control signal light can carry a destination node, an optical path name, and control contents as information. For example, when assigning information to the position and value of a framed bit such as SONET section overhead, the first 8 bits of the framed bit string are assigned to the destination node name, and the next 8 bits are assigned to the failure recovery control message. Can be assigned to By using a frame configuration in which a total of 16 bit strings are connected by the number of wavelengths by time division multiplexing, optical path switching request messages corresponding to the number of wavelengths can be transmitted collectively. This message includes an ET path disconnection command and a disconnection confirmation message.

  As shown in the node configuration in FIG. 2, these messages always terminate between nodes, so that information can be transferred for each node. Since the message relating to the working ring 101 and the message relating to the protection ring 104 are transmitted in the same direction, they are further multiplexed for a further hour and minute so that both the information transferred on the working ring 101 and the information transferred on the protection ring 104 can be respectively transmitted. Can be transferred on the ring. Similarly, both a message transmitted on the working ring 103 and a message transmitted on the protection ring 102 can be transmitted on each ring.

  Although the control signal light is electrically terminated between adjacent nodes, the control message includes the destination node and can identify the communication partner node. It is possible to configure a communication path.

  Next, each block in the node 200 will be described. FIG. 3 is a block diagram of the optical switch unit (230 or 231) used in FIG. 3, the optical switch unit 300 includes input / output terminals 301, 304 to 308, 1 × 2 optical couplers 314, 315, and 1 × 3 optical switches 309, 312. For example, when the input / output terminals 301 and 304 to 308 are used as the optical switch unit 230, 301 and 304 are used as output terminals, 305 to 308 are used as input terminals, and when they are used as the optical switch unit 231, 301 and 304 are used as input / output terminals. Input terminals 305 to 308 are used as output terminals.

  When the optical switch unit 300 is used as the optical switch unit 231 in FIG. 2, the insertion end 209 is connected to the input / output end 301, the insertion end 212 is connected to the input / output end 304, and the input / output end 308 is connected to the optical ADM unit 220. The input / output terminal 307 is connected to the optical ADM unit 219, the input / output terminal 306 is connected to the optical ADM unit 218, and the input / output terminal 305 is connected to the optical ADM unit 217.

  By employing the above connection relationship, a 2 × 4 switch function having the following switching function is realized using the optical switch unit 231. That is, the optical signal input to the insertion end 209 can be transmitted not only to the working ring 101 and the spare ring 102 but also to the spare ring 104. Similarly, the optical signal input to the insertion end 212 can be transmitted to the spare ring 102 in addition to the working ring 103 and the spare ring 104.

  When the optical switch unit 300 is used as the optical switch unit 230 in FIG. 2, the optical splitter 222 is at the input / output end 308, the optical splitter 223 is at the input / output end 307, and the optical splitter 224 is at the input / output end 306. , And an optical splitter 225 are connected to the input / output terminal 305, respectively, to realize a 4 × 2 switching function having the following switching function. That is, optical signals from any of the working ring 101, the spare ring 102, and the spare ring 104 can be output to the separation output terminal 205. Similarly, any of the working ring 103, the spare ring 104, and the spare ring 102 can be output. Can be output to the separation output end 208 as well.

  FIG. 4 is a block diagram showing a configuration example of the 1 × 3 optical switches 309 and 312 in FIG. In FIG. 4, the 1 × 3 optical switch 400 includes input / output terminals 401 to 404, optical gate type optical switches 405 to 407, and an optical coupler 408. As the gate type optical switches 405 to 407, a mechanical optical switch can be used. Further, as the optical coupler 408, a fiber fusion type optical coupler can be used.

  FIG. 5 is a block diagram showing a configuration example of the optical ADM units 217 to 220 used in FIG. In the optical ADM section 500 shown in FIG. 5, reference numeral 501 denotes a multiplexed signal input terminal for inputting a wavelength-multiplexed signal light, and reference numeral 506 denotes a multiplexed signal output terminal for outputting a wavelength-multiplexed optical signal. Reference numerals 502 and 503 denote demultiplexed signal output terminals for demultiplexing and outputting the optical signal input to the multiplexed signal input terminal 501. Reference numerals 504 and 505 denote insertion signal input terminals, which input optical signals of corresponding wavelengths to the optical ADM unit.

  Reference numeral 514 denotes a wavelength multiplexing / demultiplexing device, and reference numeral 507 denotes a wavelength multiplexing / demultiplexing device. It is not always necessary to use an AWG as a wavelength multiplexer or a wavelength demultiplexer as long as it has a function of multiplexing wavelengths or performing wavelength demultiplexing. For example, a diffraction grating or a combination of a fiber Bragg grating (a filter having a periodic structure in a fiber) has a function of multiplexing wavelengths and demultiplexing wavelengths. Applicable.

  Reference numerals 510 and 511 denote optical gate switches, and a mechanical optical switch or a gate switch using a semiconductor optical amplifier can be used. Reference numerals 512 and 513 denote optical splitters that split the power of the input light into two, output one to the separation output terminals 502 and 503, and output the other to the optical gates 510 and 511, respectively. Reference numerals 508 and 509 denote optical couplers, which output a combination of the signal lights from the insertion signal input terminals 504 and 505 and the outputs from the optical gates 510 and 511, respectively.

  The wavelength division multiplexer 507 outputs a wavelength division multiplexed light obtained by multiplexing the outputs from the optical couplers 508 and 509. The optical couplers 508 and 509 output signals from the outputs of the optical splitters 512 and 513 by turning the optical gates 510 and 511 on and off, respectively. , Or from the insertion signal input terminals 504 and 505 (the ON / OFF state can be switched on the insertion signal input terminal side by the operation of the optical switch unit 231). . In the configuration of FIG. 5, since the optical signal is branched by the optical branching devices 512 and 513, an optical signal is always output to the branch signal output terminal.

  When the optical ADM unit 500 is used as the optical ADM unit 220 in FIG. 2, the control signal separator 244 is connected to the multiplexed signal input terminal 501, the multiplexed signal output terminal 506 is connected to the control signal multiplexer 245, and The switch unit 231 is connected to the insertion signal terminal 504, and the separation signal output terminal 503 is connected to the optical splitter 225. Other optical ADM units perform the same connection.

  By using the node configuration of FIG. 2 described above for each node of FIG. 1, when each node inserts an optical signal from the insertion end 209, each of the working ring 101, the spare ring 102, and the spare ring 104 It is also possible to transmit an optical signal. Similarly, when an optical signal is inserted into the insertion end 212, an optical signal can be transmitted to any of the working ring 103, the spare ring 104, and the spare ring 102.

  Further, the branch output terminal 205 can output any one of the optical signals of the working ring 101, the spare ring 102, and the spare ring 104. Similarly, the branch output terminal 208 can output an optical signal from any one of the working ring 103, the spare ring 104, and the spare ring 102. Therefore, by switching the optical switch units 230 and 231 and the optical ADM units 217 to 220 of each node, the failure of the working optical path on a certain working ring can be performed on the clockwise spare ring and on the counterclockwise spare ring. In either case, a detour optical path can be formed.

  Next, a failure recovery operation when the network of FIG. 1 is configured using the node configuration of FIG. 2 will be described with reference to FIGS.

  As a method of allocating a path on the ring, there are a method of allocating a clockwise path and a method of allocating a counterclockwise path. Either of these light paths has a smaller or equal number of hops. Hereinafter, the one with a smaller number of hops is called a short path, and the one with a larger number of hops is called a long path. When the number of hops is equal, the one transmitting in the same direction as the working optical path is called a short path, and the path transmitting in the opposite direction to the working optical path is called a long path.

  When recovering from the failure of the ring composed of the nodes having the configuration shown in FIG. 2, a short path is formed because the insertion signal and the separation signal can be connected to either the clockwise or counterclockwise spare ring. It is possible to select whether to use a method of performing a fault recovery by performing a fault recovery or to use a method of performing a fault recovery by configuring a long path.

  Specifically, in FIG. 6, the failure of the working optical path 601 in the path from the node 106 to the node 109 to the node 107 on the working ring 101 is detected by using the protection ring 104 (counterclockwise transmission). A method of forming a detour path (standby optical path 602: short path) of the path from the node 109 to the node 107 to perform failure recovery, and a method of using the standby ring 102 (clockwise transmission) for the node 106 → the node 105 → the node There is a method of configuring a bypass path (backup optical path 603: long path) of the path from the node 108 to the node 107.

  When the ET path is configured on the spare ring, the number of disconnection of the ET path can be reduced by configuring the short path and performing the fault recovery if possible. For example, if all the optical paths having one hop number on the spare ring have a wavelength of λ1 and all paths having one hop number are used as ET paths, the spare optical path 602 (short path) is configured. In the case of performing a fault recovery by performing a fault recovery, it is necessary to separate two ET paths. However, when performing a fault recovery by configuring the backup optical path 603 (long path), it is necessary to separate the three ET paths. is there.

  Therefore, in the ring network having the node configuration shown in FIG. 2, considering the ET path use efficiency at the time of failure, the priority of the failure recovery is determined by the recovery to the short path and the recovery to the long path. When the failure is recovered by the detour, the influence on the ET path (the number of ET path disconnections) at the time of failure recovery can be reduced.

  Hereinafter, a failure recovery method that reduces the influence on the ET path using the ring network having the node configuration of FIG. 2 will be described.

  FIG. 6 illustrates a control signal and an operation step in each node when a detour to a short path is performed after a failure occurs in the network of FIG.

  Reference numeral 601 denotes a working optical path (wavelength: λ1) for transferring a working main signal light, and is transmitted from a node 106 (source node (transmission node): hereinafter abbreviated as S node) via a node 109 to a node 107 (destination node). (Reception node): hereinafter, abbreviated as D node). Normally, the spare ring is not used, and an optical path is set in the spare ring and used only when a failure occurs. The setting of the optical path in the working ring and the spare ring is realized by switching the switching state of the optical switch units 230 and 231 and switching the switching state (On state / Off state) of the optical gates 510 and 511 in FIG. .

  Now, it is assumed that an ET path of wavelength λ1 is configured from the node 109 to the node 107 on the spare ring 104. In such a state, a specific description will be given of a failure recovery operation when a break failure occurs only in the optical fiber of the working ring 101 between the node 106 and the node 109.

  In this case, since the optical fiber is broken, the optical path 601 does not reach the terminal node 107. First, the monitoring controller 221 in the node 107 confirms that the optical signal split from the optical splitter 225 does not come. The optical path 601 is detected and recognized as a failure (step 1).

  When the monitoring controller 221 detects a failure in the working optical path 601, it attempts to recover from the failure. At this time, as described above, first, it tries to recover from the short path by detouring. In order to disconnect the above short path (backup path 602), messaging is performed to the concerned node.

  Since the ET path having the wavelength of λ1 is used between the node 109 and the node 107 as the ET path related to the configuration of the backup optical path 602, first, the node 107 should not receive the ET path. Then, an instruction to stop transmission of the ET path is transferred to the node 109 by using a 1.3 μm band control signal light (step 2). Specifically, after receiving the control signal light, the ET path can be separated by switching the gate switches in the optical switch units 230 and 231 in the nodes 109 and 107.

  When the node 107 serving as the D node confirms the disconnection of the ET path, a request for transmitting the main signal light to the backup ring 104 is transferred to the node 106 serving as the S node (step 3). The request message first arrives at the node 109. When the node 109 recognizes that the request destination of the arrived message is the node 106 and is not addressed to the own node, the node 109 does not process any information and proceeds to the next. Forward to the node as it is.

  When the node 106 receives a request to switch to the own node while transmitting signal light only to the working ring 101 in order to configure the working path 601, the node 106 also transmits an optical signal to the backup ring 104 in accordance with the request. The optical switch is switched so as to transmit (step 4). Specifically, an optical signal is input to the input / output terminal 301 in FIG. 3, the input / output terminal 308 is connected to the working optical ring 101, and the spare ring 104 is connected to the input / output terminal 306. When the optical switch 309 is configured as shown in FIG. 4 and no failure occurs, only the gate type optical switch 407 is in the On state, but the gate type switch 405 is also in the On state. Switch so that

  When the operation of Step 4 is completed, the node 106 transfers the fact to the D node (node 107) using the 1.3 μm band control signal light (Step 5). If the optical ADM unit at the node 109 in the middle is not in a switch state for forming the backup optical path 602, switching is performed to achieve such a state. Specifically, on / off switching of the optical gate of the optical ADM unit 500 at the node in the middle is performed.

  When the node 107 receives the content of step 5, the node 107 switches to receive the optical signal from the spare ring 104 (step 6). Specifically, assuming that the optical switch unit 230 in FIG. 2 has the configuration in FIG. 3, a state in which an optical signal from the working ring 101 is being received (only the gate type optical switch 407 in FIG. 4 is in an On state). The state can be realized by switching to a state in which the optical signal from the backup ring 104 is received (only the gate type optical switch 405 is in the On state in FIG. 4). In step 6, the D node 107 recognizes the recovery of the failed optical path.

  After the end of step 6, the fact is transferred to the S node 106 using the control signal light (step 7). When the operation performed in step 6 is confirmed by the S node 106, the S node recognizes that the failure recovery has been completed (step 8).

  In the above operation example, the case where a failure occurs only in the working optical ring 101 is shown. In this case, since the failure recovery is performed by switching to the short path configured on the spare ring, the ET path to be disconnected is Need to be small.

  Next, an operation when a breakage fault occurs in both the fibers of the working ring 101 and the spare ring 104 will be described with reference to FIG.

  In this case, the same operation as in FIG. 6 is performed until step 5. However, since a fiber failure has occurred in the spare ring 104, the content to be transferred in step 3 is not transferred to the D node 107. Therefore, the operation described with reference to FIG. 6 cannot be performed in the node 107, and the completion of the failure recovery in Step 8 in FIG. 6 cannot be confirmed. Each node holds in advance the time required until step 8 in FIG. 6, and if the failure recovery check in step 8 in FIG. 6 cannot be performed within that time, the detour to the short path is performed. It is determined that the failure recovery due to the error cannot be performed, and the failure recovery operation by detour to the long path is started.

  In order to perform failure recovery by detouring to the long path, first, the ET path using λ1 used on the spare ring 102 constituting the long path is disconnected (step B6). Thereafter, an optical signal is transmitted to the spare ring 102 (step B7). Specifically, the node 106 has the same configuration as the node 200 in FIG. 2, and thus will be described with reference to FIGS. 2, 3, and 4. Before the failure, only the gate type optical switch 407 was in the On state. When an attempt was made to make a detour to the short path (step 4), the gate type optical switches 407 and 405 were turned on. In step B7, the gate type optical switches 407 and 406 are set to the On state because the detour to the long path is attempted.

  When the operation in step B7 is completed, the fact is transferred to the D node using the control signal light (step B8). Since switching by detour in the short path direction could not be performed, transfer of control information by the control signal light is also performed along the long path direction. When the optical ADM unit of the node in the middle of the messaging is not configured to configure the backup optical path 603, switching is performed to configure the backup optical path 603. Specifically, by switching the optical gate 510 in FIG. 5, the optical gate through which λ1 passes in the preliminary optical ring 102 is turned on.

  The D node 107 that has received the message in step B8 switches to receive the optical signal from the backup ring 102, and forms a detour path using a long path (step B9). Specifically, when FIG. 2, FIG. 3, and FIG. 4 are replaced with the node 107, it can be realized by switching only the gate type optical switch 406 in FIG. Finally, the S node (node 106) is notified that the failure recovery has been completed (step B10), the S node recognizes that the failure recovery has been completed, and the failure recovery operation ends (step B11).

  FIG. 8 shows a sequence chart of the inter-node communication and the operation at the node in the case of the failure recovery by the detour to the short path (FIG. 6). The vertical axis is the time axis, and the lower the time, the later the time. FIG. 9 shows a sequence chart of the inter-node communication and the operation in the node in the case of the failure recovery by the detour to the long path (FIG. 7).

  According to the above description, in the ring network having the node configuration of FIG. 2, if the detour to the short path is possible according to the type of the fault, the fault recovery by the detour to the short path is performed, and In the case where the detour to the path is impossible, the operation to perform the detour to the long path is described. Therefore, it is possible to reduce the number of ET paths disconnected at the time of recovery from a failure, and to configure a ring network with high ET path use efficiency.

  Also, during maintenance, detours to the long path do not have to be performed, and maintenance can be performed by detouring to the short path. There is also an effect that the use efficiency of the device increases. Since high speed is not required at the time of maintenance, it can be performed without using signaling for protection.

  In addition, since the short path passes through the same path as the working path, the detour to the short path reduces the delay difference and the instantaneous interruption time during switching. Since the delay difference is small, the memory capacity required for instantaneous interruption switching can be reduced.

  In addition, since the detour to the long path is not always performed at the time of recovery from a failure, if the recovery from the failure is possible by the detour to the short path, the number of nodes involved in switching is reduced, so the recovery time is reduced. Is done. This is particularly effective in very long haul rings.

  In addition, since there are two detour candidates at the time of failure, a short path and a long path, reliability is improved. In particular, laying the fibers of the ring transmitting signals in the same direction in different fiber conduits improves reliability. For example, when laying a fiber on a highway, if fibers that transmit signals in the same direction are dispersed on both sides of the highway, there is a high possibility that even if one fiber breaks, the other does not break. The possibility of switching to the short path is increased.

  In the above description, the case where a failure has occurred in the working rings 101 and 103 at the same point has been described. However, even when a failure has occurred in the optical fibers of all the rings at the same point, the failure recovery can be performed in the same manner. It is possible. However, depending on the location of the failure, the direction in which the control message is transmitted differs along the short path or along the long path.

  As long as control messages can be transmitted, control information may be transmitted in either direction.However, when control messages are transmitted in both directions, if control messages can be transmitted along a short path, the control is performed. Since the message arrives at the destination node first, the short path becomes valid. However, if control messages cannot be transmitted in the short path direction due to a failure, the control message cannot be transmitted along the long path. Communication is effective.

  In the present embodiment, the method of recovering from the failure of the optical signal of λ1 has been described. However, if the configuration and method of the present invention are used, an arbitrary single failure in a wavelength multiplexed system passes through the failure part. It is possible to perform failure recovery of all optical paths (including those having different source nodes and terminal nodes). Hereinafter, this will be described.

  When a single fault occurs in a fiber or a node, a fault occurs in optical paths corresponding to the number of wavelength multiplexes. Since the protection ring is shared by the working signals of the working ring, the protection ring is not used when no failure occurs. Therefore, if the same wavelength as that of the working optical path is assigned to the spare ring, the spare optical path can be assigned without wavelength collision (the same wavelength is assigned to the optical path in one optical fiber and cannot be separated). is there.

  Therefore, for any single failure, the failure of all the optical paths passing therethrough can be recovered. Further, even when multiple failures occur, it is possible to cope if either the short path or the long path can be configured.

  The method of recovering the failure of the working optical path of the working ring 101 using the spare ring 102 or the spare ring 104 as a shared spare resource and the node configuration thereof have been described above. The working ring 103 (working ring) The same node configuration and fault recovery method can be applied to the spare ring 104 and the spare ring 102 for the signal transmission in the direction opposite to the signal transmission 101. After the failure recovery operation, the failure point of the optical fiber is checked, and when the repair of the working ring 101 is completed by fusion splicing of the optical fiber, the spare resources are shared, so that the working failure is prepared in preparation for the next failure. If the optical path 601 is restored to be transmitted using the working ring 101, the spare resources can be used effectively.

  Next, a second embodiment will be described. In the first embodiment, the configuration and the method of the four-fiber ring have been described, but in the second embodiment, the case of the two-fiber ring will be described. The two-fiber ring has a clockwise ring and a counterclockwise ring. Assuming that four wavelengths λ1 to λ4 are wavelength-multiplexed, λ1 and λ2 are allocated to the wavelength of the working optical path, and λ3 and λ4 are allocated to the wavelength of the backup optical path in both rings. It is possible to allocate spare resources corresponding to the working optical path configured using λ1 and λ2 in the clockwise ring to λ3 and λ4 of the counterclockwise ring, and to assign λ1 and λ2 in the counterclockwise ring. It is possible to allocate the spare resources corresponding to the working optical path configured using λ3 and λ4 of the clockwise ring.

  Therefore, a two-fiber ring can be considered in the same way as a four-fiber ring. The resources of λ1, λ2 of the clockwise ring correspond to the working ring 101 of FIG. 1, the λ3, λ4 of the counterclockwise ring correspond to the spare ring 102 of FIG. 1, and the counterclockwise rings λ1, λ2 correspond to the working ring of FIG. When the clockwise ring λ3 and λ4 are made to correspond to the spare ring of FIG. 1, it is understood that the same operation as the four-fiber ring described in the first embodiment can be logically performed. .

  In the node configuration, λ1 and λ2 are used for the working optical path and λ3 and λ4 are used for the backup optical path. Therefore, the output end 201, the input end 202, and the input end are different from the four-fiber node configuration of FIG. 216, the output terminal 215 and the optical ADM units 217 and 218 are not used, and all the output terminals of the optical switch unit 231 are connected to the optical ADM units 219 and 220. A wavelength converter is provided between the optical switch unit 231 and the optical ADM units 219 and 220 and between the optical switch unit 230 and the optical ADM units 219 and 220.

  When the path of the working system λ1 is input to the standby system, the wavelength is converted through a wavelength converter of λ1 → λ3, and the wavelengths of the working system and the standby system are matched. As a wavelength converter, use a method in which an optical signal is once converted to an electric signal using a photodiode, and then the laser signal of a desired wavelength is modulated using the electric signal and converted to another wavelength. Is possible.

  The use of the second embodiment has the same effects as those of the first embodiment. The difference from the first embodiment is that the number of fibers used (the number of rings) is half. Therefore, when the optical fiber laying cost accounts for a large part of the cost, or when only two fiber rings can be constituted by all means, the effect is particularly effective. The point is that it gets bigger.

  In the second embodiment, a wavelength converter having a fixed wavelength output is inserted into the node configuration in FIG. 2, but it is obvious that the present invention can be applied to a wavelength converter having a variable wavelength output. In this case, the method of allocating the backup optical path can be flexibly changed, so that it is more effective to cope with multiple failures than to use a fixed wavelength converter.

  In the second embodiment, as the wavelength converter, a method of converting an optical signal into an electric signal and then converting it again into an optical signal is used. However, a wavelength converter which remains light (for example, a mutual gain of a semiconductor optical amplifier) is used. It is obvious that the present invention can be implemented even by using a modulation effect or a wavelength converter using the effect of mutual phase modulation.

  Next, a third embodiment will be described as an application method of the present invention. The third embodiment is a case of a two-fiber ring as in the second embodiment, and the first ring and the second ring transmit optical signals in opposite directions. Λ1 and λ2 are used as wavelengths for transmitting the working signal of the first ring. As the spare resources, the wavelength λ1 of the second ring is used for the working optical path of the wavelength λ1 of the first ring, and the wavelength λ2 of the second ring is used for the working optical path of the wavelength λ2 of the first ring. Λ3 and λ4 are used as wavelengths for transmitting the working signal of the second ring. As spare resources, λ3 of the first ring is used for the working optical path of the wavelength λ3 of the second ring, and λ4 of the first ring is used for the working optical path of the wavelength λ4 of the second ring.

  When the same wavelength is assigned to the two fiber rings as the working wavelength and the protection wavelength as the working wavelength and the protection wavelength, the wavelength converter used in the second embodiment does not need to be used. In the second embodiment, it is necessary to switch and transmit the working optical path λ1 and the protection optical path λ3 at a certain source node. However, according to the third embodiment, the wavelength used for the working optical path is required. This is because there is no need for wavelength conversion since the wavelength used for the backup optical path is the same.

  The use of the third embodiment has the same effects as those described in the second embodiment, except that the wavelength converter is not required.

  In the embodiment of the present invention, the configuration of FIG. 3 has been described as the optical switch units 230 and 231, but the optical switch unit may have various configurations other than the configuration of FIG.

  FIG. 10 shows another configuration example of the optical switch unit, which is prepared for failure of the 1 × 3 optical switches 309 and 312. 10, 1010 and 1011 are optical couplers, 1001 to 1008 are input / output terminals, 309 and 312 are 1 × 3 optical switches, and 310 and 311 are 1 × 2 optical switches. In this configuration, the optical signal is branched into two by the optical couplers 1010 and 1011 and connected to the 1 × 2 optical switches 310 and 311 to cope with the failure of the 1 × 3 optical switches 309 and 312.

  When the optical switch unit 1000 is used as the optical switch unit 231, the input / output terminal 1005 transmits a working optical signal forming a working optical path to the working ring 101, and the input / output terminal 1008 transmits the working optical signal in the opposite direction to 1005. A working optical signal forming a working optical path is inserted into the working ring 103, and a working optical signal input to 1008 is inserted into the input / output terminal 1007.

  If a failure occurs in the optical switch 309, the optical switch 310 is used instead. However, in the case of a double failure (the failure of the optical switch 309 and the failure of the long path), the optical switch 310 is not connected in the short path direction, so that it cannot handle short path switching.

  FIG. 11 shows another configuration example of the optical switch unit configured to cope with the case of the double failure. In FIG. 11, the 1 × 3 optical switches 309 and 312 are duplicated in preparation for a failure in the configuration of FIG. 3, and the optical switch 310 and the optical coupler 314, Since the optical switch 311 and the optical coupler 315 are connected, even if a failure occurs in the optical switches 309 and 311, the optical switches 310 and 311 can completely substitute for each other (that is, the optical switches 310 and 311). 311 has the same switching function as the optical switches 309 and 312). Accordingly, it is possible to cope with a failure of an optical switch in addition to a failure of a fiber on a ring.

  FIG. 12 shows another configuration example of the optical switch unit. In the optical switch shown in FIG. 10, the number of input / output terminals on the insertion or branch side is four instead of two. That is, in FIG. 10, the optical signal input to the input / output terminal 1001 is branched by the optical coupler 1010 to form a standby system. However, the configuration is applicable to a system having the function outside the optical switch unit. is there. The optical signal input to the input / output terminal 1202 is the same as the input / output terminal 1201 and is a standby optical signal of the input / output terminal 1201. Similarly, an optical signal input to the input / output terminal 1203 is the same as the input / output terminal 1204 and is a standby optical signal of the input / output terminal 1204.

  FIG. 13 shows another configuration example of the optical switch unit. In the optical switch shown in FIG. 11, the number of input / output terminals on the insertion or branch side is four instead of two. That is, in FIG. 11, the optical signal input to the input / output terminal 1101 is branched by the optical coupler 1010 to form a standby system. However, the configuration is applicable to a system having the function outside the optical switch unit. is there. The optical signal input to the input / output terminal 1302 is the same as the input / output terminal 1301 and is a standby optical signal of the input / output terminal 1301. Similarly, an optical signal input to the input / output terminal 1303 is the same as the input / output terminal 1304 and is a standby optical signal of the input / output terminal 1304.

  FIG. 14 shows still another configuration example of the optical switch unit. In FIG. 14, reference numerals 1401 to 1408 denote input / output terminals, 1411 to 1414 denote 1 × 4 optical couplers, and 1415 to 1418 denote 1 × 4 optical switches. According to this switch configuration, since a 4 × 4 non-blocking switch is configured, the degree of freedom of switching is increased as compared with the switch configurations of FIGS. Further, if the configuration is made using 2 × 4 optical switches, the degree of freedom of switching can be further increased.

  Also, various configurations other than the configuration of FIG. 4 are conceivable for the form of the 1 × 3 optical switch.

  FIG. 15 shows another configuration example of the 1 × 3 optical switch. In FIG. 15, the 1 × 3 optical switch 1500 includes input / output terminals 1501 to 1504 and 1 × 2 optical switches 1507 and 1508. In this configuration example, since the 1 × 3 switch function is realized by combining 1 × 2 switches, the cost can be reduced. In general, a 1 × 1 switch does not use one input / output terminal of a 1 × 2 switch (eg, a mechanical optical switch). Since the costs are almost the same, there is an effect that the cost of the 1 × 3 switch is reduced as compared with FIG.

  FIG. 16 shows another configuration example of the 1 × 3 optical switch. The 1 × 3 optical switch 1600 has a configuration in which the gate type optical switch 405 is omitted from the 1 × 3 optical switch in FIG. By using the 1 × 3 optical switch 1600 in combination with, for example, the 1 × 3 optical switch 400 in FIG. 4, the present invention can be applied.

  That is, the configuration shown in FIG. 16 is used for the 1 × 3 switch in the optical switch unit of the S node, and even if the S node continues to transmit the optical signal to the working ring at the time of recovery from the failure, the D node transmits the optical signal from the spare ring to which the detour goes. There is no problem if you select a signal. Conversely, even if the configuration of FIG. 16 is used for the 1 × 3 switch in the optical switch unit of the D node, the configuration of FIG. 4 is used for the S node, and the D node is always connected to the working ring, Thus, the optical signal can be prevented from being transmitted to the working ring, and thus the present invention can be applied to the present invention.

  Therefore, a method of using the configuration of FIG. 16 on the S node side, a method of using the configuration of FIG. 4 on the D node side, a method of using the configuration of FIG. 16 on the D node side, and a method of using the node of FIG. The present invention can also be implemented. The use of the configuration in FIG. 16 has an advantage that the number of gate switches used can be reduced as compared with the configuration in FIG.

  When the configuration of FIG. 16 is used for the S node, in order to prevent the working optical signal from arriving at the terminal node in the event of a failure, only the wavelength of the optical signal in which the failure has occurred at the intermediate node is cut off. A method can be used.

  FIG. 17 shows another configuration example of the 1 × 3 optical switch. In FIG. 17, 1700 denotes a 1 × 3 optical switch, 1701 to 1704 denote input / output terminals, 1711 denotes a gate type optical switch, 1712 denotes a 1 × 2 optical switch, and 408 denotes an optical coupler. Also in this configuration example, the number of switches can be reduced as compared with the optical switch of FIG. 4, and cost can be reduced.

  FIG. 18 shows still another configuration example of the 1 × 3 optical switch. In FIG. 18, 1800 denotes a 1 × 3 optical switch, 1801 to 1804 denote input / output terminals, 1812 denotes a 1 × 2 optical switch, and 408 denotes an optical coupler. This 1 × 3 optical switch 1800 corresponds to the 1 × 3 optical switch in FIG. 16, and the two gate switches in FIG. 16 are replaced with one 1 × 2 switch, so that the cost can be further reduced. Can be achieved.

  Further, as for the configuration of the optical ADM unit, for example, the configuration shown in FIG. 19 or 20 can be used in addition to the configuration shown in FIG.

  In the optical ADM unit 1900 in FIG. 19, 2 × 2 optical switches 1908 and 1909 are inserted between the wavelength multiplexing / demultiplexing device 514 and the wavelength multiplexing / demultiplexing device 507, and insertion signal input terminals 1902 and 1903 and a separated signal output terminal are provided. The mode is switched to 1904 and 1905. In the configuration of FIG. 5, the optical signal is always output to the separation signal output terminal. However, in this configuration, when the distribution selection type (multicast type) is not used as the 2 × 2 optical switch, the 2 × 2 optical switch is used. It is output to the separation signal output terminal only when it is in the cross state.

  In the optical ADM unit 2000 shown in FIG. 20, a part of the output of the wavelength division multiplexer 514 is directly connected to the wavelength division multiplexer 507, and the other part is directly connected to the separation signal output terminal 2002.

  For example, in the node of FIG. 2, if the configuration of FIG. 20 is used as the configuration of the optical ADM unit connected to the working ring and the configuration of FIG. 5 is used as the optical ADM unit connected to the backup ring, Although the configuration of the path is fixed, the configuration of FIG. 5 is used as the standby system, so that the configuration can be changed, and it is possible to perform a failure recovery and maintenance. According to this configuration, since the optical switch and the optical coupler required for the optical switch are not used in the active optical ADM unit, the cost is reduced accordingly.

  Also, not all connections in the optical ADM unit connected to the working ring are fixed connections, but only some of the connections in the optical ADM unit are fixed connections as shown in FIG. 20, and other connections are as shown in FIG. The configuration can be made variable using the optical switch 510, and in this case also, the effect of reducing the number of optical switches and the like for the fixed connection portion is exhibited.

  As shown in FIG. 22, a device (integrated optical switch unit) is configured by integrating the optical switch unit 230 and the optical switch unit 231 of FIG. 2 into one unit, and is connected to the optical ADM unit. The present invention can be realized without any trouble. In FIG. 22, 2201 and 2202 are external output terminals, 2203 and 2204 are external input terminals to which other network devices are connected. Reference numerals 2205 to 2208 denote output terminals connected to the multiplexer. Reference numerals 2209 to 2212 denote input terminals connected from the demultiplexer. Reference numerals 2217 to 2220 denote optical couplers, and reference numerals 2213 to 2216 denote 1 × 3 optical switches. 2212 and 2208 are connected to the clockwise working ring, 2211 and 2207 are connected to the clockwise spare ring, 2210 and 2206 are connected to the counterclockwise spare ring, and 2209 and 2205 are connected to the counterclockwise working ring. Thus, the failure recovery of the present invention can be performed.

  A configuration different from FIG. 22 will be described with reference to FIG. FIG. 22 shows that the signal input from the optical ADM unit in FIG. 2 cannot be output to another optical ADM unit without being output to the branch output end side, but FIG. 25 shows a configuration (signal Can be set so as to pass through as it is). In FIG. 25, reference numerals 2501 and 2502 denote external output terminals, and reference numerals 2503 and 2504 denote external input terminals to which other network devices are connected. Reference numerals 2505 to 2508 denote output terminals connected to the multiplexer. Reference numerals 2509 to 2512 denote input terminals connected from the demultiplexer. Reference numeral 2500 denotes a 6 × 6 optical switch, which uses a non-blocking optical switch. For example, as shown in FIG. 1 of Non-Patent Document 4, an n × n non-blocking switch connects n n-branch optical splitters to input / output terminals, and connects each input terminal and all output terminals via the optical splitter. This can be realized by using a configuration in which each output terminal is connected to all the input terminals, and a gate optical switch is arranged between the input side optical splitter and the output side optical splitter. 2512, 2508 are connected to the clockwise working ring, 2511, 2507 are connected to the clockwise spare ring, 2510, 2506 are connected to the counterclockwise spare ring, and 2509, 2505 are connected to the counterclockwise working ring. Thus, the failure recovery of the present invention can be performed. For example, by connecting the input terminal 2512 and the output terminal 2508 using the configuration of FIG. 25, it is possible to pass the signal input to the input terminal 2512 to the next node as it is.

  Since the connection for transmitting the signal to the next node without dropping and inserting the signal is possible, the configuration of the working signal can be made flexible. In the configuration shown in FIG. 22, when passing a signal without dropping and adding, it is necessary to realize the optical ADM unit shown in FIG. 2 by making it pass. Therefore, the optical ADM unit and the cooperative operation shown in FIG. 22 are required. However, if the configuration shown in FIG. 25 is used, a signal passing state can be configured by itself, so that cooperative operation is not required and control is simplified. As another advantage of this configuration, since a non-blocking switch is used as the optical switch 2500, it is possible to perform switching setting so that an input signal is returned in the direction of the input signal as it is. For example, if the input terminal 2512 and the output terminal 2509 are connected to the same network node, the 6 × 6 switch unit 2500 is switched, and the input signal is directly input by connecting the input terminal 2512 and the output terminal 2509. It is possible to set to return to the signal direction. Since this is possible, it is possible to remotely confirm whether or not the signal transmitted by the user at the time of maintenance reaches the adjacent node.

  Further, as shown in FIG. 23, the present invention can be implemented even if the branch signal output terminal and the insertion signal input terminal are duplicated in the integrated optical switch unit. In FIG. 23, reference numerals 2301 to 2304 denote external output terminals and reference numerals 2305 to 2308 denote external input terminals to which other network devices are connected. In the configuration of FIG. 22, when two network devices are connected to the external input terminal and the external output terminal, there is no spare optical transmission line. In the configuration of FIG. 23, the number of external output terminals and external input terminals is twice that of the configuration of FIG. 22, and half of them can be used for spare. Reference numerals 2205 to 2208 denote output terminals connected to the multiplexer. Input terminals 2309 to 2312 are connected to the demultiplexer. Reference numerals 2325 to 2332 denote optical couplers, and reference numerals 2317 to 2324 denote 1 × 3 optical switches. Connecting 2316, 2312 to the clockwise working ring, connecting 2315, 2311 to the clockwise spare ring, connecting 2314, 2310 to the counterclockwise spare ring, and connecting 2313, 2309 to the counterclockwise working ring. Thus, the present invention can be implemented.

  A configuration different from that of FIG. 23 will be described with reference to FIG. FIG. 23 shows that the signal input from the optical ADM unit in FIG. 2 cannot be output to another optical ADM unit without being output to the branch output terminal side, but FIG. 26 shows a configuration (signal Can be set so as to pass through as it is). In FIG. 26, reference numerals 2601 to 2504 denote external output terminals, and reference numerals 2605 to 2608 denote external input terminals to which other network devices are connected. Output terminals 2609 to 2612 are connected to the multiplexer. 2613 to 2616 are input terminals connected from the demultiplexer. Reference numeral 2600 denotes an 8 × 8 optical switch, which uses a non-blocking optical switch. 2616, 2612 connected to the clockwise working ring, 2615, 2611 connected to the clockwise spare ring, 2614, 2610 connected to the counterclockwise spare ring, 2613, 2609 connected to the counterclockwise working ring Thus, the failure recovery of the present invention can be performed.

  Since the connection for transmitting the signal to the next node without dropping and inserting the signal is possible, the configuration of the working signal can be made flexible. In the configuration of FIG. 23, when passing a signal without dropping and adding, it is necessary to realize the optical ADM section of FIG. 2 by making it pass. Therefore, the optical ADM unit and the cooperative operation shown in FIG. 22 are required. However, if the configuration shown in FIG. 26 is used, a signal passing state can be configured by itself, so that cooperative operation is not required and control is simplified. Further, in the configuration of FIG. 26, since a non-blocking switch is used as 2600, it is possible to perform switching setting such that an input signal is returned in the direction of the input signal as it is. Since this is possible, it is possible to remotely confirm whether or not the signal transmitted by the user at the time of maintenance reaches the adjacent node.

  In addition, the function of providing low-priority signal input / output terminals at the branch output end and insertion end so that low-priority signals can be accommodated in the spare ring, and accommodating low-priority signals in the spare ring. The present invention can be implemented even by using an integrated optical switch to which is added. FIG. 24 shows a configuration example in which the ET path can be accommodated at an input / output terminal different from the working signal and the backup signal. In FIG. 24, 2401-2404, 2433, and 2434 are external output terminals, 2405-2408, and 2435, 2436 are external input terminals, to which other network devices are connected. In the configuration of FIG. 22, when two network devices are connected to the external input terminal and the external output terminal, there is no spare optical transmission line. In the configuration of FIG. 24, one clockwise or counterclockwise working signal can be connected to the working or protection input / output terminal of another network device. For example, the current signal is output to 2401, and the spare signal is output to 2402. Such working / spare pairs can also be formed in 2403 and 2404, 2405 and 2406, and 2407 and 2408. Further, reference numerals 2433 to 2436 can be used for input and output of low priority signals. Output terminals 2409 to 2412 are connected to the multiplexer. 2413 to 2416 are input terminals connected from the demultiplexer. Reference numerals 2425 to 2432 denote optical couplers, and reference numerals 2417 to 2424 denote 1 × 3 optical switches. 2416 and 2412 are connected to the clockwise working ring, 2415 and 2411 are connected to the clockwise spare ring, 2414 and 2410 are connected to the counterclockwise spare ring, and 2413 and 2409 are connected to the counterclockwise working ring. Thus, the failure recovery of the present invention can be performed.

  Another configuration will be described with reference to FIG. 24 cannot output a signal input from the optical ADM unit in FIG. 2 to another optical ADM unit without outputting the signal to the branch output terminal side, but FIG. 27 shows a configuration (signal Can be set so as to pass through as it is). In FIG. 27, reference numerals 2701 to 2706 denote external output terminals, and 2707 to 2712 denote external input terminals, to which other network devices are connected. In the configuration of FIG. 27, one clockwise or counterclockwise working signal can be connected to the working or protection input / output terminal of another network device. For example, the current signal is output to 2702, and the standby signal is output to 2703. Such working / spare pairs can also be assembled in 2704 and 2705, 2708 and 2709, and 2710 and 2711. Further, reference numerals 2701, 2706, 2707, and 2712 can be used for input and output of low priority signals. 2713 to 2716 are output terminals connected to the multiplexing device. Reference numerals 2717 to 2720 denote input terminals connected from the demultiplexer. Reference numeral 2700 denotes a 10 × 10 optical switch, which uses a non-blocking optical switch. 2720, 2716 connected to the clockwise working ring, 2719, 2715 connected to the clockwise spare ring, 2718, 2714 connected to the counterclockwise spare ring, and 2717, 2713 connected to the counterclockwise working ring. Thus, the failure recovery of the present invention can be performed.

  Since the connection for transmitting the signal to the next node without dropping and inserting the signal is possible, the configuration of the working signal can be made flexible. In the configuration of FIG. 24, when passing a signal without dropping and adding, it is necessary to realize the optical ADM unit of FIG. 2 by making it pass. Therefore, the coordination operation of FIG. 22 with the optical ADM unit was necessary. However, if the configuration of FIG. 27 is used, a signal passing state can be configured by itself, so that coordination operation is not required and control is simplified. Further, in the configuration of FIG. 27, since a non-blocking switch is used as 2700, it is possible to perform switching setting such that an input signal is returned in the direction of the input signal as it is. By being able to do this, it is possible to confirm whether or not the signal itself sent at the time of maintenance has reached the adjacent node.

  Also, the present invention can be implemented by adding a signal monitoring device to those input / output terminals. By always monitoring the signal on the input side and output side of the switch unit, switching at the time of failure can be speeded up. As for the monitoring of the signal, the bit error rate of the signal and whether or not the identifier given to the signal is a predetermined one (whether there is an erroneous connection) is monitored.

  Further, a means for transmitting and receiving control / monitoring information to / from another node is added, and control of the switch unit is performed based on information obtained from the signal monitoring means and information obtained by transmitting / receiving control / monitoring information to / from another node. The present invention can also be implemented by performing Thereby, the fault recovery is automated.

  In the description of the embodiment of the present invention, it has not been mentioned how the optical path is configured as a whole on the ring, but as long as the transfer of the control signal by another wavelength forms a loop, a certain wavelength may be used. The working optical path itself need not form a loop. For example, even when only one working optical path with the wavelength of λ1 exists in the ring, the control signal is transferred at another wavelength between adjacent nodes at another wavelength, and it is possible to perform inter-node signaling. Therefore, the present invention can be implemented.

  As an embodiment of the present invention, in FIGS. 6 and 7, a case where one or two optical fibers have a breakage failure has been described. However, a failure has occurred in more optical fibers at the same point. The present invention can be implemented even when it occurs.

  In the embodiment of the present invention, a fiber fault at the same point has been described. However, even when a fiber fault occurs at a different point, a short path or a long path detour can be formed, and a control message The present invention can be applied as long as it is possible to perform the exchange.

  In the embodiment of the present invention, the case of a fiber failure has been described. However, in the case of another failure such as a node failure, the same applies to a failure of only a certain wavelength (for example, a failure of an optical transmitter of a certain wavelength). It is possible to perform fault recovery in a way.

  In the embodiment of the present invention, the method of monitoring the bit error rate is used as the monitoring of the optical path. However, the monitoring may be performed by using the method of monitoring the optical power. The optical power monitoring means can be realized, for example, by installing a photodiode at the input end and monitoring the photocurrent. In addition, it is also possible to apply a method of monitoring the S / N (signal-to-noise ratio) of light. As a method of monitoring the S / N of light, for example, it can be realized by obtaining the S / N of light by obtaining the ratio of ASE (spontaneous emission noise) to signal light.

  In the embodiment of the present invention, a sequence chart as shown in FIGS. 8 and 9 is used as a failure recovery procedure, but it is not always necessary to use the same procedure. For example, the ET path is separated from both the S node and the D node of the ET path first, and then the bypass spare optical path is configured. However, even if only the S node of the ET path is separated, the wavelength of the ET path is not changed. Since the optical signal does not exist on the spare ring and wavelength collision does not occur, it is possible to form a detour path.

  In this case, since the D node of the ET path does not disconnect the ET path, an optical signal may suddenly stop coming or an optical signal of a different destination may be received and the D node may be confused. Is notified by a control signal light or the like, it is possible to make the D node of the ET path recognize the fact.

  In the embodiment of the present invention, if a short path switching completion message is not returned after a predetermined time elapses, the failure recovery method is changed from short path switching to long path switching. The same method need not be used. For example, if any node recognizes that failure recovery by short path switching is not possible, a method to prevent short path switching by messaging from that node may be used. It is possible.

  In the present embodiment, the detour to the short path is preferentially performed irrespective of the existence of the ET path. However, the present invention is also applicable to a method of performing a failure recovery operation with a priority based on whether or not the ET path exists. Can be implemented without hindrance. For example, if the ET path exists on the spare ring forming the short path and the ET path does not exist on the ring forming the long path, a method of recovering from a failure by detouring to the long path may be used. .

  In the embodiment of the present invention, the switching method is used in preference to the short path. However, the priority determination method of the switching destination can be implemented without using this method. For example, it is also possible to use a method of determining the priority in consideration of the total number of hops, the total transmission distance, the communication amount, and the like of the ET path that must be separated for recovery from a failure.

  In the embodiment of the present invention, a ring using an optical path in a wavelength division multiplexing system has been described. However, the present invention can be applied to a system in which paths such as SONET and SDH are time-multiplexed. However, in the present invention, since the transmission distance of the optical signal can be reduced by not performing the loopback switch, the ring length can be increased. In this case, the application of the present invention increases the effectiveness (in the SONET ring, the optical signal is converted into an electric signal for each node to reproduce the signal).

  Also, since the optical path is a single optical path, whether it is an optical signal of 2.5 Gb / s or an optical signal of 10 Gb / s, the optical path of 2.5 Gb / s and the optical path of 10 Gb / s Even in a system in which paths are mixed, the same node configuration and failure recovery method as in the first embodiment can be used, and the system has high flexibility.

  If signaling between nodes is possible even if the signal speed of each working optical path is different, what is shared in the spare ring is a spare wavelength serving as a spare resource. This is because it is possible to cope with such a signal speed (a transmittable range).

  In addition, no matter what signal format the optical path signal is mixed with, the present invention can be implemented because the optical switch is independent of the signal format as long as it is switched by an optical switch and signaling between nodes is possible. is there.

  In the embodiment of the present invention, a method of using an optical path in a wavelength division multiplexing system has been described. However, the present invention can be applied to ATM VP (Virtual Path) and VC (Virtual Channel) as long as it is a ring network. Can be applied.

  In the embodiment of the present invention, an optical signal having a wavelength of 1.5 μm band is used for the main signal system and an optical signal having a wavelength of 1.3 μm band is used for the control signal system. However, the main signal system and the control signal system can be separated. The present invention is not limited to the use of these wavelengths as long as the optical signal has an arbitrary wavelength.

  In the embodiment of the present invention, an example has been described in which a frame structure is used as a method of transferring a control signal to another node, and a destination node name is assigned to the first 8 bits and a control message is assigned to the next 8 bits. There is no limitation, and any bit allocation method may be used as long as the request for path failure recovery is transmitted to the source node. In addition, there is no need to assign information to bits, and message-oriented communication can be used. It is also possible to use packet communication, frame relay, or communication using ATM.

  In the embodiment of the present invention, an example in which an optical signal having a wavelength different from that of the main signal is used as the control signal transfer means has been described. However, the present invention is not limited to this, and any medium that can transfer control information is used. Means can be used. For example, control information may be exchanged between nodes using a system in which a radio signal or a subcarrier is superimposed on an optical signal and transmitted, or control signals may be exchanged using a telephone line.

  Also, the present invention can be implemented by using a method of exchanging control monitoring information with another node using a control monitoring area in the time-division multiplexed main signal light.

  In the embodiment of the present invention, the event of detecting the failure of the own node termination signal has been described as a trigger for starting the failure recovery operation, but the failure recovery operation is started by a failure notification from another node or another network device. You may. For example, a method may be used in which a node at a stage preceding the node terminating the optical path (wavelength: λ1) detects a failure of the optical path having the wavelength of λ1 and notifies the terminal node of the abnormality to cause a failure recovery operation. The present invention can be implemented without hindrance.

  As an embodiment of the present invention, when the traffic between nodes is symmetrical in the uplink and downlink directions, or when the traffic between nodes is asymmetric in the uplink and downlink directions (for example, only the downlink In any case, the present invention can be applied.

  In the embodiment of the present invention, a system using one fault recovery method in one ring system has been described. However, the present invention is not limited to this, and other configurations such as the configuration and method of the present invention and the conventional 1 + 1 protection system can be used. Can also be realized by combining For example, for each wavelength, λ1 and λ2 can be used for the failure recovery method by the 1 + 1 method, and λ3 and λ4 can be used for the failure recovery according to the present invention.

  In the embodiment of the present invention, a mechanical optical switch is used as the optical switches 405 to 406, 510, and 511. However, if the optical switch satisfies the performance such as crosstalk and loss, the optical switch using the electro-optical effect is used. Alternatively, an arbitrary optical switch such as an optical switch using a thermo-optic effect or an optical gate switch using a semiconductor optical amplifier can be employed.

  In the embodiment of the present invention, the optical switches 230 and 231, for example, have been described based on the configuration in FIG. 3, but the present invention can be configured using switches having different sizes and configurations. That is, in the case of a system having n spare rings having shared spare resources for the working signal, it is necessary to use (n + 1) × 1 optical switches in order to be able to switch to all the working rings and the spare ring. The present invention can be configured using a larger m × n switch that includes the function of such a switch.

  Further, the present invention can be realized without any trouble even in a configuration having a switch function having a function of returning a signal input for maintenance and inspection to a transmission node as it is.

  In the embodiment of the present invention, the optical switches 230 and 231 are used as the switches of the S node and the D node. However, the optical signals are directly connected to the separation output terminal and the separation input terminal without switching, and the optical signal is electrically connected. After conversion into a signal, protection may be performed by an electric switch. As the electric switch, an electric switch for spatially switching, an electric switch for switching a time-division multiplexed signal obtained by time-division multiplexing, and an ATM for switching a connection established by a cell like an ATM switch. The present invention can be practiced with a switch without any trouble.

  In the embodiment of the present invention, an example in which an optical coupler having a branching ratio of 10:90 is used for monitoring an optical signal has been described. However, the present invention is not limited to this. The optical power splitting ratio and the coupling ratio can be arbitrarily set.

  In the embodiment of the present invention, a case of a four-node, two-wavelength ring has been described. However, the present invention is not limited to this, and the present invention is also applied to a system in which the number of nodes and the number of wavelength multiplexes are other than this. What you can do is obvious.

  In the embodiment of the present invention, a configuration in which all optical signals can be inserted and separated is used as the optical ADM unit. However, the present invention can be applied to a configuration in which insertion and separation of all wavelengths is not possible. it is obvious.

  Although the embodiment of the present invention is based on a wavelength multiplexed system, it is apparent that the present invention can be implemented even when the number of wavelength multiplexing is one.

  In the embodiment of the present invention, the case where the wavelength multiplexing technique is applied as the optical multiplexing technique has been described. However, the present invention is also applied to a system to which other multiplexing techniques such as polarization multiplexing, time multiplexing, and spatial multiplexing are applied. Can be implemented. For example, to apply the present invention to a spatial multiplexing system, a bundle of a plurality of optical fibers is treated as an optical fiber group, nodes are connected to a ring topology by the optical fiber group, and a ring configured by the optical fiber group is connected. It can be realized by treating it as one ring. As an example, if there are four rings in the fiber group, it is possible to perform failure recovery in the same manner as in the first embodiment, and if there are two rings in the fiber group, the second embodiment is used. , Can be handled in the same manner as in the third embodiment.

  As an embodiment of the present invention, the case of two fibers and four fibers has been described, but the present invention is not limited to this. For example, if a spare ring serving as a shared spare resource is increased clockwise and counterclockwise one by one from a four-fiber system, and the optical switches 309 and 312 used for failure recovery are replaced by 1 × 4 switches, even a six-fiber ring can be used. The present invention is applicable. Also, as described in the second and third embodiments, if a part of the band resource can be used as the working resource and the rest can be used as the spare resource, there is no need to use a two-fiber ring. The present invention is applicable to a three-fiber ring and a four-fiber ring.

  In addition, if a system that transmits an optical signal bidirectionally in one fiber is used, there is only one ring physically, but it can be logically regarded as two oppositely rotating rings, The configuration and method of the present invention are applicable. When this technique is used, the present invention can be applied physically using a smaller number of rings than the number of rings described in the embodiment of the present invention.

  In the embodiment of the present invention, an example in which an AWG is used as a wavelength multiplexer and a wavelength demultiplexer has been described. However, a device using a diffraction grating, a fiber Bragg grating (a fiber having a periodic structure in a fiber). Any one having a function of multiplexing wavelengths or wavelength demultiplexing, such as a combination of filters, etc., can be used.

  In the embodiment of the present invention, the optical amplifier is not used in the optical communication node or the optical transmission line. However, it is obvious that the present invention can be implemented without trouble even in a system using the optical amplifier.

  In the embodiment of the present invention, the optical communication network is described in which the optical signal passes through a node on the way without being converted into an electric signal without converting the optical signal into an electric signal. The device may be inserted. By installing such a device, it is possible to lengthen the ring, to reproduce a signal as an interface with a separation signal and an insertion signal, and to monitor an optical signal. When a device that converts an electric signal to an optical signal and then converts the signal into an optical signal is configured in the optical path, the device can be operated as a gate switch by controlling whether the device emits light or not. It is possible. For example, an optical-electrical-optical converter that can configure both a state of outputting light and a state of not outputting light can operate as a gate switch, and can be used as the gate optical switches 405 to 407 in FIG.

  It is obvious that the present invention can be implemented irrespective of where the optical signal is converted into the electric signal and the electric signal is converted into the optical signal. For example, it may exist at the input terminal or the output terminal of the optical switch unit. In that case, it is obvious that the present invention can be implemented even if an electric switch that switches electric signals is used instead of the optical switch in the embodiment of the present invention.

  In the embodiment of the present invention, the case where the optical path without wavelength conversion is used in the middle has been described. However, a wavelength converter is inserted into the ring network, and the optical path with the wavelength converted in the middle is used as the optical path. It may be treated as. As a wavelength converter, a method of once converting an optical signal into an electric signal and then converting it again to an optical signal using a light source of a desired wavelength, a method using mutual gain modulation, mutual phase modulation, four-wave mixing, etc. But it can be applied.

  In the case of using a wavelength converter, it is possible to reuse the wavelength in the spare ring (using the same wavelength again in the same ring) by allocating the spare optical path well, so that double failures and the like can be prevented. Improves resistance to multiple failures.

  In the embodiment of the present invention, light is not transmitted when no failure occurs in the spare ring.However, in order to confirm whether a failure has occurred in the transmission system using the spare ring, a failure has occurred. The present invention can be applied to a system using a method of transmitting an optical signal even when there is no signal. For example, the backup ring is periodically operated so as to configure all the backup paths, the backup optical path is monitored periodically, and when a failure is detected or a switch request message is received, the backup path for monitoring is May be stopped and a method of configuring only a spare optical path for recovery from a failure may be used.

  In the embodiment of the present invention, a description has been given of the recovery from a failure in one-way communication in either the left-handed or right-handed working path. However, in the present invention, each shared spare resource is allocated independently, and Therefore, the present invention can be applied to a case where both clockwise communication and counterclockwise communication faults occur simultaneously.

  However, if a failure occurs in one direction (for example, communication from the A node to the B node), a method of switching both directions (both communication from the A node to the B node and communication from the B node to the A node) may be used. It is obvious that the present invention can be implemented.

  In the embodiment of the present invention, the configuration of a network consisting of one ring network and the method of recovering from a failure have been described. However, the present invention is applicable even if the entire network is a connection of a plurality of ring networks. It is possible. If a failure occurs in the m-th ring network when a plurality of optical paths configured in each ring are connected to form an optical path, the m-th ring is connected independently of the other rings. The failure recovery as described in the embodiment may be performed in the system closed inside. Note that the entire network does not necessarily have to be a network in which only a plurality of ring networks are connected. For example, even if the entire network includes a configuration in which the ring network is connected by an optical transmission line having a working system and a protection system, even if the entire network includes a failure, there is no problem in the ring network. Therefore, the present invention can be applied.

  In the embodiment of the present invention, a case where the optical transmission line has a ring topology has been described, but the present invention is not limited to this. For example, even in a mesh network in which a plurality of network nodes exist and are randomly connected, if the optical signals for each wavelength are connected so as to form a ring topology, the present invention can be implemented. is there. This will be described with reference to FIG. In FIG. 28, reference numerals 2801 to 2809 are network nodes. Each node includes a wavelength multiplexing device and a wavelength multiplexing / demultiplexing device, and is capable of inserting / branching an optical signal for each wavelength. 2811 to 2815 are optical links. Wavelength multiplex transmission is performed in each optical link. The network nodes are connected by a plurality of optical links (optical transmission paths between nodes). In each link, a clockwise working wavelength, a counterclockwise working wavelength, a clockwise spare wavelength, and a counterclockwise spare wavelength are selected, and when they are connected, virtually, as shown by the thick line in FIG. It is possible to configure a ring for each wavelength. Here, the wavelength used in each link is not necessarily required to be the same as long as each node has a wavelength conversion function. For example, to construct a virtual clockwise working ring, the wavelength of λ1 in the optical link 2811, the wavelength of λ2 in the optical link 2812, the wavelength of λ1 in the optical link 2813, the wavelength of λ2 in the optical link 2814, The optical link 2815 is configured by coupling wavelengths of λ3. The present invention can be implemented by constructing four such virtual rings and assigning them to the working clockwise, spare, working left, and spare rings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 2 is a block diagram of a node used in FIG. 1. FIG. 3 is a block diagram illustrating an optical switch unit used in FIG. 2. FIG. 4 is a block diagram showing a 1 × 3 optical switch used in FIG. 3. FIG. 3 is a block diagram illustrating an optical ADM unit used in FIG. 2. FIG. 7 is a diagram illustrating a failure recovery operation (a detour to a short path) used in the first embodiment. FIG. 7 is a diagram illustrating a failure recovery operation (a detour to a long path) used in the first embodiment. 5 is a sequence chart illustrating a failure recovery operation (a detour to a short path) used in the first embodiment. 5 is a sequence chart illustrating a failure recovery operation (a detour to a long path) used in the first embodiment. FIG. 4 is a block diagram showing another embodiment of FIG. 3. FIG. 4 is a block diagram showing another embodiment of FIG. 3. FIG. 4 is a block diagram showing another embodiment of FIG. 3. FIG. 4 is a block diagram showing another embodiment of FIG. 3. FIG. 4 is a block diagram showing another embodiment of FIG. 3. FIG. 10 is a block diagram showing another embodiment of FIG. 4. FIG. 10 is a block diagram showing another embodiment of FIG. 4. FIG. 10 is a block diagram showing another embodiment of FIG. 4. FIG. 10 is a block diagram showing another embodiment of FIG. 4. FIG. 13 is a block diagram showing another embodiment of FIG. 5. FIG. 13 is a block diagram showing another embodiment of FIG. 5. FIG. 9 is a block diagram showing a conventional example. FIG. 3 is a block diagram showing an embodiment in which a switch on a sending side and a switch on a receiving side are integrated. FIG. 23 is a block diagram showing another embodiment of FIG. 22. FIG. 23 is a block diagram showing another embodiment of FIG. 22. FIG. 23 is a block diagram showing another embodiment of FIG. 22. FIG. 24 is a block diagram showing another embodiment of FIG. 23. FIG. 25 is a block diagram showing another embodiment of FIG. 24. FIG. 11 is a network configuration diagram showing another embodiment of FIG. 1.

Explanation of reference numerals

101, 103 Working ring 102, 104 Spare ring 105-109 Node 201, 203, 215, 213 Output end 202, 204, 214, 216 Input end 205, 208 Branch output end 209, 212 Insertion end 217-220 Optical ADM section 221 Monitoring controllers 222 to 225 Optical splitters 230, 231 Optical switch units 241, 243, 245, 247 Control signal multiplexers 242, 244, 246, 248 Control signal demultiplexers 309 to 312 1 × 3 optical switches 313 to 316 Optical couplers 405 to 407 Gate type optical switch 408 Optical coupler 507 Wavelength multiplexers 508, 509 Optical couplers 510, 511 Optical gates 512, 513 Optical splitter 514 Wavelength multiplexing / demultiplexer 601 Active optical path 602 Spare optical path 603 Spare light Pass 1010, 1011 Optical coupler 14 11-1414 Optical couplers 1415-1418 1 × 4 optical switch 1507, 1508 1 × 2 optical switch 1711 Gate type optical switch 1712, 1812 1 × 2 optical switch 1908, 1909 2 × 2 optical switch 2109, 2110 1 × 2 optical switch 2131 Working optical path 2132 Backup optical path

Claims (13)

A plurality of communication node means for inserting and separating signals, and a plurality of transmission paths, wherein the plurality of communication node means are at least first connected to each other by the connection of the plurality of transmission paths to form the same network topology. , A second ring, a third ring, and a fourth ring, wherein the first ring transmits a working signal either clockwise or counterclockwise, and a working signal of the first ring. The spare resources of the second ring for transmitting signals in the opposite direction to the first ring and the spare resources of the fourth ring for transmitting signals in the same direction as the first ring are used as spare resources for a plurality of working signals. The third ring transmits the working signal in the opposite direction to the first ring and transmits the working signal in the reverse direction to the third ring as a backup resource for the working signal of the third ring. Signal by using and sharing the second ring reserve resource for transmitting a signal to the fourth ring and the third ring in the same direction for transmitting among the plurality of current signals to,
Failure recovery of a first communication path for inserting a signal at an i-th communication node means of the plurality of communication node means and terminating the signal at a j-th communication node means via the first ring And a detour configured for the maintenance, using a detour configured for the second ring or the fourth ring,
Failure recovery of a second communication path for inserting a signal at an mth communication node means of the plurality of communication node means and terminating the signal at an nth communication node means via the third ring And a communication network using a detour configured in the fourth ring or the second ring as a detour configured for maintenance.
When the j-th communication node detects a failure in the first communication path, it sends a request to switch the path of the first communication path to the i-th communication node, and Upon receiving this request, the jth communication node means sends the signal of the first communication path to the spare resource, and after this sending, the jth communication node means sets the first communication path to the standby resource. Perform disaster recovery by switching to resources,
When the n-th communication node detects a failure in the second communication path, it sends a request to switch the route of the second communication path to the m-th communication node, and The second communication node means, upon receiving the request, sends the signal of the second communication path to the spare resource, and after the sending, the nth communication node means sets the second communication path to the spare resource. A communication network characterized by performing a fault recovery by switching to resources. A plurality of communication node means for inserting and separating signals, and a plurality of transmission paths, wherein the plurality of communication node means are at least first connected to each other by the connection of the plurality of transmission paths to form the same network topology. And a second ring, wherein the first ring transmits the working signal in one of clockwise and counterclockwise directions, and the second ring transmits the working signal in the opposite direction to the first ring. The first ring is shared between a working signal group transmitted by the second ring and a working signal group transmitted by the first ring within its transmission band, and A second resource ring having a spare resource band transmitted in the opposite direction to the signal, wherein the second ring has a working signal group transmitted by the first ring and a working signal transmitted by the second ring within the transmission band; Between groups By having shared and reserve resource band to be transmitted to the working signal and the opposite direction,
Failure recovery of a first communication path for inserting a signal at an i-th communication node means of the plurality of communication node means and terminating the signal at a j-th communication node means via the first ring And a communication path configured by a spare resource band of the second ring or a spare resource band of the first ring as a bypass configured for maintenance.
Failure recovery of a second communication path for inserting a signal at an mth communication node means of the plurality of communication node means and terminating the signal at an nth communication node means via the second ring A communication network using a communication path constituted by a spare resource band of the first ring or a spare resource band of the second ring as a detour configured for maintenance.
When the j-th communication node detects a failure in the first communication path, it sends a request to switch the path of the first communication path to the i-th communication node, and Upon receiving this request, the jth communication node means sends the signal of the first communication path to the spare resource band, and after this sending, the jth communication node means sets the first communication path to the first communication path. Perform failure recovery by switching to the reserve resource band,
When the n-th communication node detects a failure in the second communication path, it sends a request to switch the route of the second communication path to the m-th communication node, and Upon receiving this request, the nth communication node means sends the signal of the second communication path to the spare resource band, and after this sending, the nth communication node means sets the second communication path to the second communication path. A communication network for recovering from a failure by switching to a spare resource band.   3. The communication network according to claim 1, wherein said communication node means is an optical communication node means, said transmission path is an optical transmission path, and said communication is optical communication.   The communication network according to claim 3, wherein the optical communication is a wavelength multiplexing optical communication.   The communication network according to claim 1, wherein the communication network is a part of an entire network. A plurality or single multiplexed signal input terminal for inputting a multiplexed signal, a plurality of or singular inserted input terminals for inserting a signal, and a demultiplexed signal obtained by demultiplexing the multiplexed signal input to the multiplexed signal input terminal. A plurality of or a single demultiplexing output terminal, and a plurality of insertion / demultiplexing means having a multiplexed signal output terminal for multiplexing and outputting the signal input to the insertion input terminal and the demultiplexed signal;
A plurality or a single external input terminal connected to another node;
A plurality or a single external output terminal connected to another node;
A plurality or a single switch means having a plurality of output terminals;
Plural or singular merging means;
A plurality or singular signal inputs;
A plurality or a single signal output end;
A plurality or a single signal monitoring means for monitoring a signal input to the joining means,
It comprises a plurality of or a single control means for exchanging control information with other nodes and performing switching control of the switch means,
The external input terminal is connected to a multiplex signal input terminal of the insertion / separation / multiplexing means;
A multiplexed signal output terminal of the insertion / demultiplexing means is connected to the external output terminal,
The signal input terminal is connected to the switch means,
Insertion input terminals of the plurality of insertion / demultiplexing units, wherein the external output terminal connected to the multiplexed signal output terminal is connected to the same node, and insertion of the insertion / demultiplexing unit connected to a node different from the same node An input terminal is connected to an output terminal of the switch means,
Separation output terminals of the plurality of insertion / demultiplexing units, wherein the external input terminal connected to the multiplexed signal input terminal is connected to the same node, and separation of the insertion / demultiplexing unit connected to a node different from the same node. An output terminal is connected to an input terminal of the merging means,
The merging means is connected to the signal output end,
The control means controls the switch means based on a result of monitoring of a signal input to the merging means of the signal monitoring means and a result of transmission and reception of control information with the other node,
Upon detecting the failure, the transmission-side terminal node of the path in which the failure has occurred transmits a request to switch the path of the path, and after the transmission-side terminal node transmits a signal to the protection resource band, the path is switched. A communication network node device for recovering from a failure by switching to the spare resource band.   7. The communication network node apparatus according to claim 6, wherein said insertion / demultiplexing means is an optical signal insertion / demultiplexing means.   7. The communication network node apparatus according to claim 6, wherein said insertion / demultiplexing means is means for performing insertion / demultiplexing by wavelength.   The internal connection of the insertion / separation multiplexing means connected to the working ring includes a fixed connection, and the insertion / separation means connected to the spare ring has switching means inside the switching means. 7. The communication network node device according to claim 6, wherein the connection is variable. A spare resource for forming a bypass communication path is shared by a plurality of working signals, and is connected to the ring network from an input end of a first communication network node device existing in the ring network having a communication path for control messages. An error recovery method for communication to an output end of an existing second communication network node device, comprising:
When the second communication network node device detects the communication failure, the first communication network node device is transmitted to the first communication network node device using the communication path for the control message. And a request to switch the path of a path connecting the second communication network node device and the second communication network node device to a detour, and when the first communication network node device receives this request, the signal of the path is converted to the spare signal. Sending to a detour using resources, and after this sending, the second communication network node device switches the path to a detour using the backup resource to perform communication failure recovery,
When performing the transmission, if there is a low-priority communication path that hinders the configuration of the detour, disconnect the communication path before sending a signal to the detour,
A fault recovery method, wherein the detour is around or in the same direction as the route before the switching.   11. The communication network node device according to claim 6, wherein the first communication network node device and the second communication network node device are the communication network node devices according to claim 6, claim 7, or claim 8. Disaster recovery method.   The failure recovery method according to claim 10, wherein the ring network is a part of the entire network.   The communication node means is an optical communication node means, the transmission path is an optical transmission path, the communication is wavelength-division multiplexed optical communication, and the first to fourth rings are connected by an optical signal in wavelength units. The communication network according to claim 1, wherein the communication network is a configured ring.

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