JP3788263B2 - Communication network, communication network node device, and failure recovery method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication network, a communication network node device, and a failure recovery method.
[0002]
[Prior art]
In the following, separation means that a signal that has been transferred in a network node is decomposed and output 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 with a transmission signal and transmitted to another node. Passing means that some or all of the transmitted signal is not separated or inserted into other communication devices within the node, and the wavelength or time slot is not changed as it is, or is connected spatially. This means that transmission is performed or the wavelength or time slot is changed and transmitted to another node. In the following description, an optical path is defined from an electrical signal converted into an optical signal at a certain node and sent to another node until it is converted into an electrical signal again.
[0003]
In order to meet the demand for an increase in communication capacity, optical communication networks have taken measures to increase the capacity in one optical transmission line by performing wavelength multiplexing. In order to operate such a network efficiently, an optical ADM (Add / drop multiplexers) node that switches and demultiplexes and inserts an optical signal in a communication network node is configured with a ring topology. An optical ADM ring system connected in such a manner is being studied. As the optical ADM ring system, a four-fiber bidirectional ring and a two-fiber unidirectional ring are considered.
[0004]
The 4-fiber ring is a system having four rings made of fibers, and the 2-fiber ring is a system having two rings made of fibers.
[0005]
The four-fiber ring has been conventionally used as a bidirectional ring. A bidirectional ring means a ring that communicates with each other using a clockwise signal and a counterclockwise signal on the same route when communication between certain nodes is considered. Four rings are used as a working ring for transmitting a clockwise working signal light, a counterclockwise working ring, a counterclockwise spare ring for a clockwise working ring, and a spare ring for a counterclockwise working ring. . When a failure occurs in all the fibers between a certain node, as shown in FIG. 10, by changing the connection to the backup fiber that transmits in the opposite direction at the node before the failure point (loopback switch), It is possible to perform fault recovery (see, for example, the document AF Elrefaie, “Multiwavelength survivable ring network architectures” in Proc. ICC '93, pp. 1245-1251, 1993.). In FIG. 10, reference numerals 1005 to 1008 denote communication nodes. Reference numeral 1021 denotes a working optical path that passes through the working ring 1001, and is terminated at the node 1007 from the node 1006 through the node 1005 and the node 1008. Now, when a break failure occurs in the fiber between the node 1005 and the node 1008, the wavelength multiplexed signal is switched to the spare ring 1002 while being multiplexed so that the node 1005 and the node 1008 which are the nodes closest to the failure point are folded back (loop) Back switching), the detour 1022 is configured to perform failure recovery. Eventually, at the time of failure recovery, the optical signal passes through the paths of the node 1006, the node 1005, the node 1006, the node 1007, the node 1008, and the node 1007, so that the optical transmission is performed over a longer distance than one ring. At this time, in the case of a failure in the bidirectional ring, the wavelength-division multiplexed signal light is switched in a batch for each fiber.
[0006]
The two-fiber ring has traditionally been used as a unidirectional ring. A unidirectional ring means, for example, that communication between nodes is usually performed by a clockwise signal. In unidirectional rings, the 1 + 1 protection method is used as a failure recovery method (for example, H. Toba et al., “An optical FDM-based self-healing ring network arrayed waveguide grating filters and EDFA's with level equalizers,” IEEE J. on Select. Areas Commun. Vol. 14, no.5, pp. 800-813). FIG. 11 is a diagram for explaining failure recovery using the 1 + 1 protection method. Reference numerals 1101 and 1103 denote working rings, and 1102 and 1104 denote spare rings. As shown in FIG. 11, in the 1 + 1 protection method, the transmission side node (source node) preliminarily transmits the backup optical path 1122 clockwise on the backup ring 1102 and the optical transmission on the working ring 1101 counterclockwise. It is sent to both the working optical path 1121 to be used. In the receiving node, it is possible to receive a clockwise signal and a counterclockwise signal by switching the switch. Therefore, when a failure occurs, the receiving node is switched so as to receive the signal that has not failed. It is possible to perform failure recovery. Since a clockwise signal and a counterclockwise signal always flow in communication between certain nodes, it can be said that the currently used signal always flows in both the clockwise and counterclockwise directions without needing to distinguish between the currently used signal and the standby signal. .
[0007]
By using a two-fiber unidirectional ring, it is possible to apply the 1 + 1 protection method, and therefore it is possible to perform failure recovery at a very high speed. When the 1 + 1 protection method is used with a two-fiber unidirectional ring, loopback is not performed from the viewpoint of optical transmission, so that the optical transmission distance does not become larger than one round of the ring.
[0008]
In addition, in SONET (for example, TH Wu, “Fiber Network Service Survivability,” see Artech house, 1992), a two-fiber unidirectional ring can be used to recover from failure by looping back the failure section (loopback). (Eg, TH Wu, “Fiber Network Service Survivability,” Artech house, 1992). Since the loopback is performed in the same manner as described for the 4-fiber ring, the total transmission distance may be longer than one round of the ring.
[0009]
On the other hand, by using a four-fiber bi-directional ring, it is possible to perform failure recovery at a certain high speed (in the case of SONET, about 50 msec).
[0010]
By using the configuration as described above, it is possible to configure a communication network that performs failure recovery at high speed.
[0011]
[Problems to be solved by the invention]
However, by using a two-fiber unidirectional ring (1 + 1 protection method), a backup path is prepared for the working path by making a reverse path corresponding to 1: 1 on the ring, and the optical signal is always transmitted. Therefore, the efficiency of use decreases and the cost increases.
[0012]
On the other hand, when using a system that performs loopback when recovering from a failure such as a four-fiber bidirectional ring, if a path close to the ring circumference is used as the current path, optical transmission of nearly two rounds by loopback is performed. Must be done. Even when a path of about half a ring is used as a working path, it is necessary to perform optical transmission for nearly one and a half cycles.
[0013]
The problem to be solved by the present invention is to construct a ring system having a fault recovery function that has good path accommodation efficiency and is capable of setting a long ring total length, thereby reducing the cost of the communication network. It is to be.
[0014]
[Means for Solving the Problems]
A first invention is a communication network node device, wherein a plurality or a single multiple signal input terminal for inputting a multiple signal and a plurality of or a signal for inserting a signal are inserted.
Multiple or single demultiplexing output terminals for outputting a demultiplexed signal obtained by demultiplexing a single insertion input terminal and a multiplexed signal input to the multiple signal input terminal, a signal input to the insertion input terminal, and the demultiplexing signal Multiple or single insertion / separation multiplexing means having multiple signal output terminals for multiplexing and outputting, multiple or single external input terminals connected to other nodes, and multiple or single external outputs connected to other nodes A plurality of or single switch means having a plurality of output terminals, a plurality or single merging means, a plurality or single signal input terminals, and a plurality or single signal output terminals, and the external input terminal The multiplex signal input terminal of the insertion / separation multiplexing means is connected, the multiplex signal output terminal of the insertion / separation multiplex means is connected to the external output terminal, the signal input terminal is connected to the switch means, and the switch means Connected to said insertion input end of the insertion demultiplexing means, said insertion separation output end of the division multiplexing means is connected to said confluence means, the merging means is characterized by being connected to said signal output terminal.
[0015]
A second invention is a communication network node device, wherein a plurality or a single multiple signal input terminal for inputting a multiple signal and a plurality of or a signal for inserting a signal are inserted.
Multiple or single demultiplexing output terminals for outputting a demultiplexed signal obtained by demultiplexing a single insertion input terminal and a multiplexed signal input to the multiple signal input terminal, a signal input to the insertion input terminal, and the demultiplexing signal Multiple or single insertion / separation multiplexing means having multiple signal output terminals for multiplexing and outputting, multiple or single external input terminals connected to other nodes, and multiple or single external outputs connected to other nodes Control information to and from other nodes, multiple or single switch means having multiple output terminals, multiple or single merge means, multiple or single signal input terminals, multiple or single signal output terminals, and other nodes And a plurality of control means for performing switching control of the optical switch means based on the control information, and the external input terminal is connected to a multiplexed signal input terminal of the insertion / separation multiplexing means, A multiplexing signal output terminal of a multiplexing means is connected to the external output terminal, the signal input terminal is connected to the switch means, the switching means is connected to an insertion input terminal of the insertion / separation multiplexing means, and the insertion / separation multiplexing means The separation output terminal is connected to the merging means, and the merging means is connected to the signal output terminal.
[0016]
A third invention is a communication network node device, wherein a plurality or a single multiple signal input terminal for inputting a multiple signal and a plurality of or a signal for inserting a signal are inserted.
Multiple or single demultiplexing output terminals for outputting a demultiplexed signal obtained by demultiplexing a single insertion input terminal and a multiplexed signal input to the multiple signal input terminal, a signal input to the insertion input terminal, and the demultiplexing signal Multiple or single insertion / separation multiplexing means having multiple signal output terminals for multiplexing and outputting, multiple or single external input terminals connected to other nodes, and multiple or single external outputs connected to other nodes A plurality of or single switch means having a plurality of output terminals, a plurality or single merging means, a plurality or single signal input terminals, a plurality or single signal output terminals, and a signal input to the merging means A plurality of or a single signal monitoring means for monitoring the optical switch means, and a plurality or a single control means for controlling the switching of the optical switch means by exchanging control information with other nodes. Connected to the multiplex signal input terminal, the multiplex signal output terminal of the insertion / separation multiplex means is connected to the external output terminal, the signal input terminal is connected to the switch means, and the switch means is connected to the insertion / separation multiplex means. Is connected to the insertion input terminal, the separation output terminal of the insertion / separation multiplexing means is connected to the joining means, the joining means is connected to the signal output terminal, and the control means is connected to the joining means of the signal monitoring means. The switch unit is controlled based on a monitoring result of an input signal and a result of transmission / reception of control information with the other node.
[0017]
A fourth invention is the communication network node apparatus according to claim 1, 2 or 3, wherein the insertion / separation multiplexing means is an optical signal insertion / separation multiplexing means.
[0018]
A fifth invention is the communication network node apparatus according to claim 1, 2 or 3, wherein the insertion / demultiplexing means is means for performing wavelength insertion / demultiplexing.
[0019]
The operation of the present invention will be described below.
[0020]
In the system described in the present invention, when a failure occurs, a shared spare resource is used, and the failure path is set and switched in the reverse direction for each optical path to perform failure recovery. There is no need to perform switching, and it is not necessary to perform optical transmission for one or more rounds. In the present invention, the path switch method is used. However, since spare resources are shared, the path accommodation efficiency is increased. This is because when the conventional 1 + 1 protection method is used, the protection path must be operated at all times, so one path in one ring has a maximum of two paths (up and down directions between certain nodes). In contrast, the system described in the present invention can accommodate only the maximum number of adjacent nodes at one wavelength in one working ring (the number of nodes) because the spare resource is shared among all the working resources. Only because it is possible to accommodate a pass. Since the loopback is not performed and the path accommodation efficiency is high, the cost of the communication network is reduced.
[0021]
In particular, in the case of a wavelength division multiplexing system, since it is difficult to monitor by a unit in which wavelengths are originally bundled, it is necessary to perform management in units of wavelengths. Since it can be introduced, the cost is reduced. In particular, systems with a small number of paths, such as wavelength multiplexing systems (the number of paths that can be wavelength-multiplexed does not increase the number of paths because there are physical restrictions) and systems that handle high-speed signals with many low-speed signals multiplexed. When the present invention is applied, the number of paths to be managed is small, the management cost is reduced, and the effect is further increased.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0023]
A first embodiment will be described with reference to FIG. FIG. 1 is a block configuration diagram of an optical wavelength division multiplexing communication network according to the first embodiment of this invention. Reference numerals 105 to 108 denote optical communication network nodes. These nodes form a four fiber ring by connecting the fibers to form a ring topology. Reference numerals 101 and 103 denote working rings, and 102 and 104 denote spare rings. Each node has a clockwise working signal processor (121 in the node 108) for processing a clockwise working ring signal and a counterclockwise working signal processor (node 108) for processing a counterclockwise working signal. Has 122). The clockwise working processing unit handles the signal of the working ring 101 and the signal of the counterclockwise standby ring 102 (at the time of failure). The counterclockwise working signal processing unit handles the counterclockwise working ring 103 signal and the clockwise spare ring 104 signal (during failure). Each node separates and inserts a wavelength-multiplexed signal. For example, from the node 105, the optical signals 109 to 112 are wavelength-multiplexed and output. 109 and 110 are optical signals wavelength-demultiplexed from the working ring 101, and 111 and 112 are optical signals wavelength-demultiplexed from the working ring 103. Optical signals 113 to 116 are inserted. 113 and 114 are optical signals to be inserted into the working ring 101, and 115 and 116 are optical signals to be inserted into the working ring 103. During the ring, two wavelengths λ1 and λ2 in the 1.5 μm band are used as the main signal light for transmitting data. Therefore, for example, it is possible to assign λ1 to 113 and 115 and λ2 to 114 and 116, respectively. In addition to the main signal light, 1.3 μm band control signal light (wavelength: λs) is also wavelength-multiplexed with the main signal light and transmitted in order to exchange control signals between adjacent nodes. Only the node 105 is shown for the separation signal and the insertion signal, but the other nodes 106 to 108 have the same functional configuration.
[0024]
FIG. 2 shows a clockwise working signal processing unit 200 (121 in FIG. 1), which is a block constituting the node. Reference numerals 201 and 205 denote external input terminals, and 204 and 208 denote external output terminals, which are each connected to another node using an optical fiber. The optical fiber of the working ring 101 is connected from the node 105 to the external input end 201 and is connected from the external output end 208 to the node 107. The optical fiber of the spare ring 102 is connected from the node 107 to the external input end 205 and from the external output end 204 to the node 105. Reference numerals 221 and 223 denote control signal separators for separating optical signals input from the external input terminal, and transmitting 1.5 μm band wavelength-multiplexed main signal light to the optical ADM units 209 and 210, respectively. The control signal light (λs) is input to the monitoring control devices 215 and 216. As the control signal separators 221 and 223, it is possible to use a WDM coupler that separates a wavelength of 1.3 μm band and a wavelength of 1.5 μm band. 202 and 203 are demultiplexing output terminals for outputting the wavelength-multiplexed optical signal (λ1 or λ2), and 206 and 207 are demultiplexing input terminals for inputting one-wave optical signal (λ1 or λ2). Other network devices such as SONET terminators and ATM switches (see, for example, TH Wu, “Fiber Network Service Survivability,” Artech house, 1992) are connected. Reference numerals 209 and 210 denote optical ADM units. The optical ADM unit 209 wavelength-multiplexes and demultiplexes the wavelength multiplexed light input from the external input terminal 201 and outputs the multiplexed light to the directions 218 and 220 or outputs the multiplexed light to the external output terminal 208. The optical ADM unit 210 wavelength-multiplexes and demultiplexes the wavelength multiplexed light input from the external input terminal 205 and outputs it to the directions 217 and 219 or outputs it to the external output terminal 204. Reference numerals 217 to 220 denote optical branching units, which tap a part (for example, 10% of the optical power) of the optical signal output after wavelength demultiplexing from the optical ADM unit and connect to the monitoring controllers 215 and 216. The remaining most optical signals (for example, 90% of the optical power) are output to the optical switch 213 and the optical switch 214.
[0025]
211 to 214 are 2 × 1 optical switches, and mechanical optical switches can be used. The optical switches 213 and 214 are connected to the optical demultiplexed outputs from the optical ADM units 209 and 210 using an optical fiber, and the optical signals input to the external input terminal 201 are wavelength demultiplexed or external inputs. One of the optical signals input to the end 205 after wavelength division multiplexing is selected and output to the separated output ends 202 and 203, respectively. Similarly, an optical signal having one wavelength is input to each of the optical switches 212 and 211. By switching the optical switches 212 and 211, the optical ADM units 209 and 210 perform wavelength multiplexing to the external output terminals 208 and 204, respectively. It is possible to select which one of the data is output.
[0026]
Reference numerals 215 and 216 denote monitoring controllers that monitor the tapped optical signal and send a switching control signal to the optical switches 211 to 214. The monitoring controllers 215 and 216 monitor the bit error rate of the input optical signal by installing an optical receiver at the input terminal of the monitoring control unit to monitor the transmission quality of the optical signal (SONET frame as an optical signal). Can be used to monitor the bit error rate; for example, TH Wu, “Fiber Network Service Survivability,” Artech house, 1992). In the node 108, the clockwise working signal processing unit usually monitors the error rate of the optical signal transmitted through the working ring 101 from the external input terminal 201 to determine whether the optical signal is normally transmitted. to manage. The monitoring control unit is connected to the optical switches 211 to 214, and can switch the optical switches 211 to 214 according to information of the monitoring control unit.
[0027]
Control signal multiplexers 222 and 224 are connected to the preceding stage of the external output terminals 204 and 208, respectively, and control signal light (1.3 μm band) sent from the monitoring controllers 215 and 216 to the other nodes and the main Wavelength multiplexing of signal light (1.5 μm band) is performed. As the control signal multiplexer, a WDM coupler can be used in the same manner as the control signal separators 221 and 223. By superimposing and separating the control signal light on the main signal light using the control signal separators 221 and 223 and the control signal multiplexers 222 and 224, it is possible to exchange control signals with other nodes. is there.
[0028]
Since the control signal light from the other node is also input to the monitoring control unit, both switching based on the control information from the other node and switching based on the monitoring result of the optical signal of the own node are possible.
[0029]
The counterclockwise working signal processing unit can use the same configuration as 200 in FIG. Similarly, it is possible to connect to the clockwise working signal processing unit, the counterclockwise working signal processing unit, the working ring 103, and the spare ring 104. Nodes other than the node 108 can also form nodes and be connected to the optical fiber of the ring.
[0030]
FIG. 3 shows a block of the optical ADM units 209 and 210 used in FIG. Reference numeral 300 represents an optical ADM unit. Reference numeral 301 denotes a multiplexed signal input terminal for inputting wavelength-multiplexed signal light, and reference numeral 306 denotes a multiplexed signal output terminal for outputting wavelength-multiplexed optical signals. Reference numerals 302 and 303 denote demultiplexed signal output terminals for wavelength-demultiplexing and outputting the optical signal input to the multiple signal input terminal 301. Reference numerals 304 and 305 denote insertion signal input terminals for inputting one-wave optical signals. Reference numeral 314 denotes a wavelength demultiplexer, 307 denotes a wavelength multi-wavelength multiplexer, and AWG (Arrayed-waveguide grating: for example, K. Okamoto et al., “Fabrication of unequal channel spacing arrayed-waveguide demultiplexer modules,” Electron. Lett., 1995 , vol.31, no.17, pp.1464-1465.). 310 and 311 are optical gate switches, and a mechanical optical switch or a gate switch using a semiconductor optical amplifier can be used. Reference numerals 312 and 313 denote optical splitters that split the input light power into two, output one to the separate output terminals 302 and 303, and output the other to the optical gates 310 and 311, respectively. Reference numerals 308 and 309 denote optical couplers that output a combination of the signal light from the insertion signal input terminal 304 and the insertion signal 305 and the output from the optical gates 310 and 311, respectively. Reference numeral 307 outputs wavelength multiplexed light obtained by combining the outputs from the optical couplers 308 and 309. By setting the optical gate 310 and the optical gate 311 to the on state or the off state, the signal input to the wavelength poly-multiplexer 307 is made from the output of the optical branching device, or from the input signal input end. It is possible to select whether to do. In the configuration of FIG. 3, since the light is branched by the optical branching units 312 and 313, an optical signal is always output to the branch signal output terminal.
[0031]
Next, the failure recovery operation when the node configuration of FIG. 2 and the network of FIG. 1 are used will be described with reference to FIGS.
[0032]
FIG. 4 shows a main signal, a control signal after the occurrence of a failure, and operation steps at each node in the network of FIG. In the following, an optical path is defined as a period from when an electrical signal is converted into an optical signal at a certain node and transmitted to another node until it is converted into an electrical signal again. One wavelength corresponds to the optical path. Reference numeral 401 denotes a working optical path for transferring the working main signal light, which is terminated at the node 108 from the node 106 (source node: transmission node) via the node 105, and uses the wavelength of λ1. Normally, the spare ring is not used, and an optical path is set and used only when a failure occurs. In the spare ring, the optical signals arriving from other nodes are set in advance in all nodes. This can be realized by setting the optical gates 310 and 311 in FIG. 3 to the On state in the spare ring. Now, a failure recovery operation when a break failure occurs in all the optical fibers between the node 106 and the node 105 will be described. Since the optical fiber breakage failure, the optical path 401 does not reach the end node 108. First, the supervisory controller 215 in the clockwise working signal processing unit of the node 108 detects the deterioration of the bit error rate, and the optical path A failure 401 is recognized (step 1).
[0033]
When the supervisory controller detects a failure in the working optical path, the node 108 switches the optical switch 213 to select and output the optical signal from the spare ring 102 (external input terminal 205) (step 2), and switches to the source node 106. The supervisory controller is set in advance so that the request message is transmitted in the direction in which no failure has occurred using the control signal light (λS) (step 3). In the control signal light, it is possible to put a destination node, an optical path name, and control contents as information. For example, it can be realized by assigning information to the position and value of a framed bit like a SONET section overhead. For example, the first 8 bits of the framed bit string are assigned to the destination node name, the next 8 bits are assigned to the identifier of the optical path, and the next 1 bit is assigned whether or not to request switching. If a frame configuration in which the total number of 17-bit bit strings is connected by the number of wavelengths is used, optical path switching request messages for the number of wavelengths can be sent in a batch. In this case, it is possible to send a message amount that can cope with a single failure in which an optical fiber between nodes is broken.
[0034]
When the control system set as described above is used, when the node 108 recognizes a failure in (Step 1), the node 108 selects the signal from the protection ring 102 (the same wavelength as the working optical path: λ1). The optical switch 213 is switched (step 2), and the working optical path identifier and a switching request message (λS) are sent to the source node (step 3).
[0035]
The node 107 receives the control signal light, but since it is not a message addressed to the own node, it is transferred to the node 106 as it is (step 4). When the control signal light arrives at the node 106, it is a message addressed to the own node. Therefore, the working optical path 401 that has been sent to the working ring 101 by switching the optical switch corresponding to the optical switch 212 in FIG. The optical signal (λ1) is sent to the spare ring 102 (step 5). The node 107 is not set to receive the light having the wavelength λ1 of the protection ring 102, and is in a state in which the optical signal is passed through to another node as it is, and the node 108 is set to the wavelength λ1 of the protection ring 102. Since the wavelength is set to be received (step 2), the optical switch 213 of the node 108 selectively outputs the optical signal having the wavelength λ1 from the backup ring 102 (formation of the backup optical path 402), and the active optical path 401 The fault is recovered by using the backup optical path 402.
[0036]
In this embodiment, after step 2 (switching of optical switch 213), step 3 (sending a switch request message to the source node) is executed, but the order of (step 2) and (step 3) is Even if it is reversed, the present invention can be carried out without hindrance. When the time required for message transmission dominates the failure recovery speed, the entire failure time is shortened because the message is transmitted first.
[0037]
FIG. 5 shows a sequence chart of the inter-node communication and the operation at the node. The vertical axis is the time axis, indicating that the time is later as it goes down.
[0038]
FIG. 6 shows an example of a flowchart of control that each node should have in order to realize this sequence. Reference numeral 601 denotes a branch, which is classified according to whether or not a failure of the termination signal of the own node is detected. The act of recognizing the failure of the own node termination signal is defined as (Step 1). Reference numeral 602 denotes a procedure, which confirms that no failure has occurred in the own node and recognizes that the failure recovery has been completed (step 6). Reference numeral 605 denotes a procedure, which creates an arrangement for receiving an optical signal from the spare ring by switching the optical switch (step 2). Reference numeral 606 denotes a procedure, which transmits a control message toward the source node of the optical path where the failure has occurred (step 3). Reference numeral 603 denotes a branch, which determines whether a control signal sent from another node is addressed to the own node. Reference numeral 607 denotes a procedure. When a control message addressed to another node arrives, it is directly transferred to the other node (step 4). Reference numeral 604 denotes a branch, which determines whether the arrived control signal is a switch request addressed to the own node. Reference numeral 608 denotes a procedure, which refers to the optical path identifier designated by the arrived control signal, and switches the corresponding optical path to be sent to the spare ring.
[0039]
If such a flowchart is applied to each node, failure recovery as shown in FIG. 4 becomes possible.
[0040]
In the above, the failure recovery method for the working optical path having the wavelength 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 is passed through the failure part. It is possible to perform failure recovery for all optical paths (including those having different source nodes and terminal nodes). This will be described below. When a single failure of a fiber or node occurs, a failure occurs in the optical paths for the number of multiplexed wavelengths. Since the spare ring is shared by the working signal of the working ring, the spare ring is not used when no failure has occurred. Therefore, if the same wavelength as that of the working optical path is assigned to the standby ring that transmits a signal in the direction opposite to the transmission direction of the working ring, wavelength collision (the same wavelength is assigned to the optical path in one optical fiber can be separated). It is possible to assign a spare optical path without any loss. Therefore, the failure of all optical paths passing therethrough can be recovered for any single failure. Further, even when multiple failures occur, it can be dealt with if the route opposite to the working optical path is safe.
[0041]
In the above, the method of performing failure recovery for the working optical path of the working ring 101 using the spare ring 102 that is a shared spare resource and the node configuration thereof have been described. However, the working ring 103 (the signal opposite to that of the working ring 101) is described. The same node configuration and failure recovery method can be applied to the transmission) and spare ring 104. After the failure recovery operation, the failure point of the optical fiber is confirmed, and when the repair of the working ring 101 is completed by fusion splicing of the optical fiber, the spare resource is shared, It returns to the original state so that it can be transmitted using the working optical path 401 without using the optical path 402.
[0042]
By using the first embodiment, failure recovery is performed without performing loopback switching, so that the transmission distance of the optical signal can be reduced. Therefore, when the distance that can be transmitted with light is determined, it is possible to configure a ring having a larger overall length than a system that performs loopback. Further, unlike the 1 + 1 protection, the spare resources are not exclusively used and the spare resources are shared, so that the number of active optical paths to be operated can be increased. In the 1 + 1 system, when the shortest route is set as the upstream communication, the route around the same direction is always used in the downstream direction, so that the accommodation of the optical path becomes inefficient. For example, in the 1 + 1 system, only two optical paths can be configured per ring with one wavelength (in FIG. 11, the optical path 1122 and the optical path from the node 1107 to the node 1106). By using this configuration, for example, as shown in FIG. 7, a maximum of four optical paths can be configured with one wavelength. In FIG. 7, reference numerals 701 to 704 denote working optical paths having a wavelength λ1, 101 denotes a working ring, and 102 denotes a spare ring. The spare resource for the working optical paths 701 to 704 is the spare ring 102, which is shared among the working optical signals. For example, the protection optical path for the working optical path 701 uses the wavelength λ 1 on the protection ring 102 along the path of node 106 → node 105 → node 108 → node 107. The protection optical path for the working optical path 702 can use the wavelength λ1 on the protection ring 102 in the path of node 107 → node 106 → node 105 → node 108. In the section from the node 106 → the node 105 → the node 107, the same wavelength λ1 is used and shared as the backup optical path. Since these spare optical paths are independent events (for a single failure), it is possible to share a spare resource of λ1 in the spare ring 102 between the working optical paths 701 and 702. is there. Similarly, in the case of FIG. 7, the wavelength λ <b> 1 that is a spare resource of the spare ring 102 is shared between the working optical paths 701 to 704 after all. The same applies to optical paths of other wavelengths. In addition, since the spare resources are shared, the optical path can be set independently for the clockwise working ring and the counterclockwise working ring for communication between certain nodes. Set to to improve efficiency.
[0043]
In addition, since the messaging for failure recovery is at most one round of the ring, it is possible to perform failure recovery at the same speed as the operation speed of SONET 4-fiber bi-directional ring. .
[0044]
In the 1 + 1 protection method, since an optical signal is always transmitted to the backup path, backup resources are used even when no failure occurs. On the other hand, when this configuration and method are used, spare resources can be used when a failure has not occurred, and an optical path with a low priority can be passed there (standby access). When a failure occurs because the priority is low, it may be used as a backup optical path for other high-priority optical paths, but when there is no failure, a low-priority optical path can be configured. There are advantages.
[0045]
Also, in the SONET system, the quality of the signal of the path (for example, error rate) can be achieved by monitoring in units of lines (signal units in which paths between adjacent nodes are multiplexed) that monitor the signals that bundle the paths. Was possible. However, in a wavelength division multiplexing system, it is necessary to always manage the wavelength between nodes, and it is difficult to operate a management system only by managing only a bundle of optical paths. Therefore, since the management and monitoring system can be used when the failure recovery is performed in units of optical paths in the configuration and method of the present invention, it is more effective.
[0046]
Also, in the current SONET system, 50 Mb / s is handled as a path unit, but switching is performed in units of path groups in which these are bundled (for example, 2.5 Gb / s in which signals of 50 Mb / s are bundled). If handled, the number of paths to be managed is reduced, and the effect of applying this method is further increased. Even in the case of light, the number of wavelength divisions is limited to some extent due to physical restrictions, so that the number of paths does not become very large and is more effective.
[0047]
In addition, by using the first embodiment, even if a failure occurs, only the terminal node and the source node of the optical path need to switch to recover the failure of the optical path. This node only has to transfer the switching request message issued from the terminal node to the source node, so that the control is simple and the failure recovery speed is increased.
[0048]
Next, a second embodiment will be described. In the first embodiment, the configuration and method of the four-fiber ring have been described. In the second embodiment, the case of the two-fiber ring will be described. In the two-fiber ring, there are a clockwise ring and a counterclockwise ring. Assuming that four waves of λ1 to λ4 are wavelength-multiplexed, in both rings, λ1 and λ2 are assigned to wavelengths of the working optical path, and λ3 and λ4 are assigned to wavelengths of the standby optical path. 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 λ1 and λ2 in the counterclockwise ring It is possible to allocate spare resources corresponding to the working optical path configured by using the λ3 and λ4 of the clockwise ring. Accordingly, the two-fiber ring can be considered similarly to the four-fiber ring. The resources of λ1 and λ2 of the clockwise ring correspond to the working ring 101 in FIG. 1, λ3 and λ4 of the counterclockwise ring correspond to the spare ring 102 of FIG. 1, and the counterclockwise rings λ1 and λ2 correspond to the working ring of FIG. If the λ3 and λ4 of the clockwise ring are made to correspond to the spare ring of FIG. 1, the operation similar to that of the four-fiber ring described in the first embodiment is possible. . Since the node configuration uses λ1 and λ2 for the working optical path and λ3 and λ4 for the backup optical path, for example, the output end of the optical switch 212 and the optical ADM are compared to the four-fiber node configuration of FIG. A wavelength converter that converts the input optical signal to λ1 is inserted between the optical unit 212 and the wavelength converter that converts the input optical signal to λ3 between the output end of the optical switch 212 and the optical ADM unit 210. A wavelength converter for converting the input optical signal to λ2 is inserted between the output end of the optical switch 211 and the optical ADM unit 209, and between the output end of the optical switch 211 and the optical ADM unit 210. In addition, it is necessary to insert a wavelength converter for converting the input optical signal into λ4. As a wavelength converter, a method is used in which an optical signal is once converted into an electrical signal using a photodiode, and then the laser signal having a desired wavelength is modulated and converted to another wavelength using the electrical signal. Is possible.
[0049]
By using the second embodiment, there is an effect similar to the effect in the first embodiment. The difference from the first embodiment is that the number of fibers to be used (the number of rings) is half, so that it is particularly effective when the optical fiber installation cost occupies most of the cost or when only two fiber rings can be constructed. Will increase.
[0050]
In the second embodiment, a wavelength converter with a fixed wavelength output is inserted into the node configuration of FIG. 2, but it is obvious that the present invention can be applied even when a wavelength converter with a variable wavelength output is applied. In that case, since the method of assigning the backup optical path can be flexibly changed, it is more effective than using a fixed wavelength converter when dealing with multiple failures.
[0051]
In the second embodiment, a method of converting an optical signal into an electric signal and then converting it back to an optical signal is used as a wavelength converter. However, a wavelength converter with light as it is (for example, a mutual gain of a semiconductor optical amplifier) It is obvious that the present invention can also be implemented using a wavelength converter using a modulation effect or a mutual phase modulation effect.
[0052]
Next, a third embodiment will be described as an application method of the present invention. Similar to the second embodiment, the third embodiment is a case of a two-fiber ring, and the first ring and the second ring transmit optical signals in the opposite directions. The wavelengths λ1 and λ2 are used as wavelengths for transmitting the working signal of the first ring, and as the reserve resources, the wavelength λ1 of the second ring and the wavelength of the first ring with respect to the working optical path of the wavelength λ1 of the first ring Λ2 of the second ring is used for the working optical path with wavelength λ2. Λ3 and λ4 are used as wavelengths for transmitting the working signal of the second ring, and λ3 of the first ring and the wavelength of the second ring are used as spare resources for the working optical path of the wavelength λ3 of the second ring. λ4 of the first ring is used for the working optical path of λ4. As described above, when the same wavelength is assigned to the rings that are transmitted in the opposite directions as the working and backup wavelengths for the two-fiber ring, it is not necessary to use the wavelength converter used in the second embodiment. In the second embodiment, the wavelength converter is necessary because the wavelength λ1 is used for the working optical path and the wavelength λ3 is used for the backup optical path in a certain source node. However, the third embodiment is different from the third embodiment. This is because when used, the wavelength used for the working optical path is the same as the wavelength used for the backup optical path, and therefore wavelength conversion is not necessary.
[0053]
When the third embodiment is used, there is an effect similar to the effect described in the second embodiment except that the wavelength converter becomes unnecessary.
[0054]
In the embodiment of the present invention, the case of a fiber failure has been described, but it is obvious that the failure can be recovered by the same method even in the case of other failures such as a node failure.
[0055]
In the embodiment of the present invention, the method of monitoring the bit error rate is used as the monitoring of the optical path, but it is also possible to monitor using the method of monitoring the optical power. This can be realized by installing a photodiode at the input end and monitoring the photocurrent. In addition, it is possible to apply monitoring of the S / N (signal to noise ratio) of light. The S / N of light can be obtained by obtaining the ratio of ASE (spontaneously emitted light noise) and signal light.
[0056]
In the embodiment of the present invention, the sequence as shown in FIG. 5 is used. However, for example, the present invention can be implemented without any trouble even if the order of step 2 and step 3 is switched.
[0057]
In the embodiment of the present invention, the flowchart as shown in FIG. 6 is used as the control of each node. However, it is obvious that the same flowchart need not be used. For example, if the order of the group of the branch 603 and its associated procedure 607 and the group of the branch 604 and its associated procedure 608 are reversed (after the branch procedure 602, the branch 604 is changed first. It is clear that the present invention can be practiced without hindrance.
[0058]
In the embodiment of the present invention, the ring using the optical path in the wavelength multiplexing system has been described. However, it is obvious that the present invention can also be applied to a system in which paths such as SONET and SDH are time multiplexed. is there. However, since the transmission distance of the optical signal can be reduced by not performing the loop-back switch, the ring length can be increased. Therefore, the present invention is applied to an optical network in which an optical signal passes through a node as it is. (2) The effectiveness of the method is increased (in the SONET ring, an optical signal is converted into an electric signal for each node to regenerate the signal). Further, since the optical path is a single optical path, whether it is a 2.5 Gb / s optical signal or a 10 Gb / s optical signal, a 2.5 Gb / s optical path and a 10 Gb / s optical signal are used. 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 flexibility is high.
[0059]
In the embodiment of the present invention, a method 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. It is obvious that is applicable.
[0060]
In the embodiment of the present invention, the configuration shown in FIG. 3 is used as the configuration of the optical ADM unit, but the configuration shown in FIG. 8 and the configuration shown in FIG. 9 can be used.
[0061]
FIG. 8 shows another embodiment of the configuration shown in FIG. 3, in which a 2 × 2 optical switch is inserted between the configuration wavelength demultiplexer 314 and the wavelength poly-multiplexer 307, and the input signal is input. And switching to the separation signal output terminal. In the configuration of FIG. 3, an 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. Only when it is in the cross state, it is output to the separation signal output terminal.
[0062]
FIG. 9 shows another embodiment of the configuration shown in FIG. 3, in which a part of the output of the wavelength demultiplexer is directly connected to the wavelength poly-multiplexer and the other part is a separated signal. It is directly connected to the output end. Although these operations cannot be switched between separation and insertion operations, the failure recovery operation of the present invention can be performed by applying them to the optical ADM unit shown in FIG.
[0063]
Even when other configurations or combinations of these are used, a multiplexed signal is input, a part of the demultiplexed signal is output, a part is input to the multiplexer, and an insertion signal is input to the multiplexer. It is obvious that the present invention can be applied to any configuration that can be input.
[0064]
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, but the main signal system and the control signal system can be separated. If it is a thing, it is obvious that it is not limited to using these wavelengths.
[0065]
In the embodiment of the present invention, a frame configuration is used as a method for transferring a control signal to another node, the destination node name is in the first 8 bits, the optical path identifier is in the next 8 bits, and the switching request is in the next 1 bit. Even if it is not the same as this, any bit allocation method may be used as long as a path failure recovery request is transmitted to the source node. Further, there is no need to assign information to bits, and message-oriented communication can be used. Packet communication, frame relay, and communication using ATM can also be used.
[0066]
In the embodiment of the present invention, an optical signal having a wavelength different from that of the main signal is used as the control signal transfer means. However, it is not necessary to use a wavelength different from that of the main signal, and any medium that can transfer control information is used. It is obvious that it can be applied. For example, the present invention can be applied even if control information is exchanged between nodes using a radio signal or a system that superimposes and transmits a subcarrier on an optical signal, or control signals are exchanged using a telephone line. it is obvious.
[0067]
In the embodiment of the present invention, the event of failure detection of the own node termination signal is used as a trigger for starting the failure recovery operation. However, even if the failure recovery operation is started by failure notification from another node or another network device. Obviously, the present invention can be implemented without any problem. For example, a method may be used in which a failure recovery operation is performed by detecting an abnormality in an optical path having a wavelength of λ1 and notifying the termination node of the optical path having a wavelength of λ1 at a node preceding the node that terminates the optical path (wavelength: λ1) The present invention can be carried out without hindrance.
[0068]
In the configuration of the present invention, when no failure has occurred, the spare ring is set to pass all optical signals. However, the present invention can also be performed by performing this setting when a switch request message arrives from the end node. It is obvious that it is applicable. However, when this method is used, the failure recovery time may be delayed because the optical gate is switched after the switch request message arrives.
[0069]
In the embodiment of the present invention, the case where the traffic between nodes is symmetric in the uplink and downlink directions has been described. However, when the traffic between nodes is asymmetric in the uplink and downlink (for example, communication in the downlink) It is self-evident that the present invention can be applied to a system having only the above-mentioned system.
[0070]
In the embodiment of the present invention, the method of using one failure recovery method in one ring system has been described. However, the present invention can also be realized by combining the configuration and method of the present invention with other methods such as the conventional 1 + 1 protection method. For example, for each wavelength, λ1 and λ2 can be used for failure recovery by the 1 + 1 method, and λ3 and λ4 can be used for failure recovery by the present invention. Further, it is not always necessary to make a detour in the direction opposite to the transmission direction of the working optical path. For example, if a failure occurs only in the working ring between nodes and the spare ring is safe, a detour is assigned to the shortest path on the spare ring. In that case, the switch request message is sent in both the clockwise and counterclockwise directions.
[0071]
In the embodiment of the present invention, mechanical optical switches are used as the optical switches 211 to 214. However, as long as the optical switch satisfies the performance such as crosstalk and loss, the optical switch using the electro-optical effect or the thermo-optics is used. The present invention can also be implemented by an optical switch using the effect or an optical gate switch using a semiconductor optical amplifier.
[0072]
In the embodiment of the present invention, an optical switch in which a signal is not distributed to another path when a path in the switch is made conductive is used as the optical switches 211 to 214. For example, a semiconductor gate switch is provided on the branch side of the optical coupler. It is obvious that the present invention can be applied even if a distribution selection type switch (a switch capable of multicasting) having a connected configuration is used if the multicast function is blocked by a gate.
[0073]
In the embodiment of the present invention, 2 × 1 optical switches are used as the optical switches 211 to 214, but the present invention can also be applied to switches having sizes and configurations different from those of the 2 × 1 switches. For example, it is possible to connect a spare network device to the input end of an optical switch to which the separation input end 207 is not connected by applying a 2 × 2 switch as the optical switch 212. In addition, a distribution selection type 2 × 2 switch is used as the optical switch 213, and one of the output ends of the optical switch is connected to the separation output end 202, and the other is connected to the optical signal monitoring device to monitor the optical signal. However, it is clear that the present invention can be implemented without any problem.
[0074]
The distribution selection type optical switch used as the 1 × 2 optical switch 211, 212 for switching the transmission side can be realized by a configuration in which an optical gate switch (a switch for switching whether light is allowed to pass or not) is connected to the coupler branch. It is. In addition, it is also possible to use a configuration in which an optical gate switch is connected to one output end of the optical gate switch and no optical gate switch is connected to the other output end. An optical switch output end to which the optical gate switch is connected may be connected to the spare ring, and an optical switch output end to which the optical gate switch is not connected may be connected to the working ring. Normally, since it is necessary to prevent signal light from flowing through the spare ring, it is necessary to connect an optical gate switch and turn it on / off. However, even if an optical signal flows through the working ring, the optical switch 213 at the termination node is not used. This is because it is possible to select either the working ring or the spare ring.
[0075]
Further, in the case of a system having n spare rings having shared spare resources for the working signal, it is necessary to use an (n + 1) × 1 optical switch in order to be able to switch to all the spare rings to the working ring. . It is obvious that the present invention can be applied even if a general m × n switch in which a plurality of such switches are integrated is used.
[0076]
In the embodiment of the present invention, the optical switches 211 to 214 are used as switches on the transmission side and the reception side. However, the optical switches are directly connected to the separation output terminal and the separation input terminal without switching, and the optical signal is electrically connected. It is obvious that the present invention can be implemented also by performing protection with an electrical switch after conversion to a signal.
[0077]
In addition, as an electrical switch, an electrical switch that switches spatially, an electrical switch that switches a time-division multiplexed signal that has been time-division multiplexed, or an ATM that switches a connection established by a cell like an ATM switch. Even with a switch, the present invention can be implemented without any problem.
[0078]
In the embodiment of the present invention, an optical coupler having a branching ratio of 10:90 is used for monitoring an optical signal. However, if the optical level design is not a problem, the optical power branching ratio and the coupling ratio are particularly limited. It is obvious that it is not.
[0079]
In the embodiment of the present invention, the case of a ring of 4 nodes and 2 wavelengths has been described. However, it is obvious that the present invention can be applied to a system other than the number of nodes and the number of wavelength multiplexing.
[0080]
In the embodiment of the present invention, a configuration in which all optical signals can be inserted and separated is used. However, it is obvious that the present invention can be applied to a configuration in which all wavelengths cannot be inserted and separated.
[0081]
The embodiment of the present invention is based on a wavelength multiplexed system, but it is obvious that the present invention can be implemented even when the number of wavelength multiplexing is 1.
[0082]
In the embodiment of the present invention, the case where the wavelength multiplexing technique is applied as the optical multiplexing technique has been studied. However, the present invention can be implemented by applying other multiplexing techniques such as polarization multiplexing, time multiplexing, and spatial multiplexing. It is clear. In order to apply the present invention to a spatial multiplexing system, an object in which a plurality of optical fibers are bundled is treated as an optical fiber group, nodes are connected to a ring topology by the optical fiber group, and one ring constituted by the optical fiber group is connected to one ring. The present invention can be applied by treating it as a ring. For example, if there are four rings in the fiber group, it is possible to perform failure recovery as in the first embodiment. If there are two rings in the fiber group, the second embodiment, This is because it can be handled in the same manner as in the third embodiment.
[0083]
As an embodiment of the present invention, the case of two fibers is shown, but the case of four fibers is shown, but it is not limited thereto. For example, if a spare ring that is a shared spare resource is increased clockwise and counterclockwise by one from a 4-fiber system, and the switch used for failure recovery is a 3 × 1 switch, the present invention can be applied to a 6-fiber ring. it can. In addition, as described in the second and third embodiments, if a part of the bandwidth resource is used as the active resource and the rest as the spare resource, there is no need for the two-fiber ring. The present invention can also be applied to a three-fiber ring and a four-fiber ring.
[0084]
If a system that transmits an optical signal in both directions in a single fiber is used, there is physically only one ring, but it can be considered logically as two rings in the reverse direction. Configurations and methods are applicable. When this technique is used, the present invention can be physically applied using a smaller number of rings than the number of rings described in the embodiment of the present invention.
[0085]
In the embodiment of the present invention, the reception side node switches the ring to be received by using a switch. However, if a failure occurs, the optical signal of the failure is not input to the receiving node (switching to send a signal to the detour at the source node), so at the receiving node, Only the optical signal from the ring with no failure is input to the signal termination node. Therefore, it is not necessary to select which ring to receive using an optical switch, and the present invention can be implemented without any trouble by using an optical coupler. Therefore, as an example of the merging means in the claims of the present invention, it is possible to use a coupler type such as an optical coupler that adds power and a switching type such as the optical switch described in the embodiment of the present invention. is there.
[0086]
In the embodiment of the present invention, AWG is used as a wavelength multiplexer and a wavelength demultiplexer, but a filter using a diffraction grating or a fiber Bragg grating (a filter is formed by providing a periodic structure in the fiber). It is self-evident that the present invention can be practiced without any problem if a device having a function of multiplexing or demultiplexing wavelengths is used, such as a combination of the above.
[0087]
In the embodiment of the present invention, an optical amplifier is not used in an optical communication node or an optical transmission line, but it is obvious that the present invention can be implemented without any trouble even in a system using the optical amplifier.
[0088]
In the embodiments of the present invention, an optical communication network that passes light through an intermediate node without converting an optical signal into an electrical signal has been described. However, the optical signal is converted into an optical signal again after being converted into an electrical signal. It is obvious that the present invention can be carried out without any trouble even when the device is inserted. By inserting such a device, the ring can be extended.
[0089]
In the embodiment of the present invention, an optical path without wavelength conversion in the middle is used. However, even if a wavelength converter is inserted in the ring network and wavelength conversion is performed in the middle, it can be handled as an optical path. The present invention can be carried out without hindrance. Wavelength converters include a method of converting an optical signal into an electrical signal and then converting it back 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. By using the 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 multiple faults such as double faults can be achieved. Increases resistance.
[0090]
In the embodiment of the present invention, light was not transmitted when no failure occurred in the spare ring. However, in order to confirm whether or not a failure occurred in the transmission system using the spare ring, the occurrence of the failure occurred. The present invention can be applied even when a method of flowing an optical signal is used even when it is not. For example, when the backup ring is operated periodically to configure all backup paths and the backup optical path is periodically monitored, a fault is detected or a switch request message is received, the backup path for monitoring It is sufficient to use a method in which only the backup optical path for failure recovery is configured.
[0091]
In the embodiment of the present invention, the recovery from a failure in one-way communication, either the left-handed or the right-handed working path, has been described. The present invention can be applied. This is because in the present invention, each shared spare resource is independently assigned, and a detour can be formed independently.
[0092]
【The invention's effect】
If the present invention is applied, since the failure recovery is performed without performing the loopback switch, the total transmission distance of the optical signal can be reduced. Therefore, when the distance that can be transmitted with light is determined, it is possible to configure a ring having a larger overall length than a system that performs loopback. Further, unlike the 1 + 1 protection, the spare resources are not exclusively used and the spare resources are shared, so that the number of active optical paths to be operated can be increased. Therefore, it is possible to realize a ring system having a failure recovery function having characteristics of both path accommodation efficiency and a long ring total length, and a communication network can be constructed at low cost.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a block configuration diagram showing a clockwise working signal processing unit used in FIG. 1;
FIG. 3 is a block diagram showing an optical ADM unit used in FIG. 2;
FIG. 4 is a diagram illustrating a failure recovery operation used in the first embodiment.
FIG. 5 is a sequence chart illustrating a failure recovery operation used in the first embodiment.
FIG. 6 is a flowchart in one node for explaining a failure recovery operation used in the first embodiment.
FIG. 7 is a diagram for explaining the effect of the system used in the first embodiment.
FIG. 8 is a block diagram showing another embodiment of FIG. 3;
FIG. 9 is a block diagram showing another embodiment of FIG. 3;
FIG. 10 is a block diagram showing a conventional example.
FIG. 11 is a block diagram showing a conventional example.
[Explanation of symbols]
101, 103 Working ring
102, 104 Spare ring
200 Right-hand working signal processor
211-214 Optical switch
215, 216 Supervisory controller
217-220 optical splitter
310, 311 Optical gate
401 Working optical path
402 Preliminary light path
1021 Working optical path
1022 Backup light path
1121 Working optical path
1122 Backup optical path

Claims (4)

A plurality or a single multiplexed signal input terminal for inputting a multiplexed signal; a plurality or a single insertion input terminal for inserting a signal; and a plurality of signals for outputting a demultiplexed signal obtained by demultiplexing a multiplexed signal input to the multiplexed signal input terminal or A plurality of or single insertion / separation multiplexing means having a single separation output terminal and a multiple 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 ends;
A plurality or a single merging means for selectively outputting one of the plurality of input ends when a signal is input to the input end ;
Multiple or single signal inputs; and
Multiple or single signal output ends;
A signal monitoring means plural or singular monitors the signals input to the merging means,
It consists of a plurality of or single control means that exchange control information with other nodes and perform switching control of the switch means,
The external input terminal is connected to a multiple signal input terminal of the insertion and demultiplexing means;
A multiple signal output end of the insertion / separation multiplexing means is connected to the external output end,
The signal input terminal is connected to the switch means;
The switch means is connected to an insertion input end of the insertion demultiplexing means;
A separation output terminal of the insertion / separation multiplexing means is connected to the merge means;
The merging means is connected to the signal output end;
When the signal monitoring means detects a failure in the input signal to the local communication network node device, the control means sends a failure recovery request to the signal source node device, and the control means sends the failure recovery request. A communication network node device characterized by switching a switching means of the communication network node device.   2. The communication network node apparatus according to claim 1, wherein said inserting / demultiplexing means is an optical signal inserting / demultiplexing means.   2. The communication network node apparatus according to claim 1, wherein said inserting / demultiplexing means is means for performing wavelength inserting / demultiplexing. A communication network node device of a communication network in which the communication network node device is connected in a ring shape via a plurality of transmission paths,
When a failure occurs in communication from another communication network node device on the communication network to the own communication network node device, the failure is detected, and a failure recovery request message is transmitted when the failure is detected. node sends addressed device, the self communication have line switching of the input signal network node device receives a communication network node failure Ru is receiving an input signal from the other communication network nodes that are not detected A communication network node device comprising: a monitoring control means.

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