JP3351365B2 - Communication network, communication node, and failure recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a communication network, a communication network node device, and a failure recovery system.

[0002]

2. Description of the Related Art In the following, the term "separation" means to output a signal obtained by decomposing a signal transferred from a network node to another communication device in the 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 the wavelengths and time slots are not replaced as they are, or are spatially connected. This means that the data is transmitted to another node by changing the wavelength or changing the time slot. Hereinafter, 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 transmitted to another node until the signal is converted again into an electric signal.

[0003] In order to meet the demand for large capacity communication,
In optical communication networks, wavelength multiplexing allows
Means have been taken to increase the capacity in the optical transmission line of the book. In order to operate such a network efficiently, an optical ADM (Add / Drop Multiplexer) that switches at a wavelength unit of an optical signal in a communication network node and separates and adds an optical signal.
An optical ADM ring system in which nodes are connected so as to form a ring topology has been studied. As an optical ADM ring system, a four-fiber bidirectional ring and a two-fiber unidirectional ring are considered.

[0004] A four-fiber ring is a system having four rings constituted by fibers, and a two-fiber ring is a system having two rings constituted by fibers.

A four-fiber ring has conventionally been used as a bidirectional ring. A bi-directional ring means a ring that communicates with each other using clockwise and counterclockwise signals on the same route when communication between certain nodes is considered. The four rings are a working ring transmitting clockwise working signal light, a counterclockwise working ring, a counterclockwise spare ring for a clockwise working ring, and a clockwise spare ring for a counterclockwise working ring. Used as a ring. When a failure occurs in all the fibers between certain nodes, as shown in FIG. 10, the connection is switched to a spare fiber that transmits in the opposite direction at the node before the failure point (a loopback switch). Disaster recovery can be performed (eg, AF Elrefaie, "Multiwavelength sur
vivable ring network architectures "in Proc.
ICC '93, pp. 1245-1251, 1993.). FIG.
, 1005 to 1008 represent communication nodes. 1
021 is a working optical path passing through the working ring 1001;
The node 1006 passes through the nodes 1005 and 1008 and is terminated at the node 1007. Now, node 1005
When a breakage fault occurs in the fiber between the node 1008 and the node 1008, the nodes 1005 and 1008, which are the nodes closest to the fault point, switch to the spare ring 1002 with the wavelength multiplexed signal multiplexed so as to be turned back (loopback switching). The detour 1022 is configured to perform failure recovery.
After all, at the time of recovery from the failure, the optical signal is transmitted to the nodes 1006, 1005, 1006, 1007, and 1
008 and the node 1007, so that optical transmission over a longer distance than one round of the ring is performed. At this time,
In the bidirectional ring, when a failure occurs, wavelength multiplexed signal light is switched collectively for each fiber.

[0006] Two fiber rings have traditionally been used as unidirectional rings. The unidirectional ring means, for example, that communication between nodes is normally performed by all clockwise signals. For unidirectional rings, 1+
Use a single protection scheme (eg, H. Toba et.
al., "An optical FDM-based self-healing rin
g network employing 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. 1
Reference numerals 101 and 1103 represent working rings, and reference numerals 1102 and 1104 represent spare rings. As shown in FIG. 11, in the 1 + 1 protection scheme, the transmitting node (source node) previously transmits a protection optical path 1122 clockwise clockwise on the protection ring 1102, and a counterclockwise light transmission on the working ring 1101. To the working optical path 1121 to be transmitted. The receiving node can receive the clockwise signal and the counterclockwise signal by switching the switch, so that when a failure occurs, the reception node is switched to receive the signal without the failure. By doing so, it is possible to perform failure recovery. Since clockwise and counterclockwise signals are always flowing in communication between certain nodes,
In particular, it can be said that the working signal always flows in both clockwise and counterclockwise directions without distinction from the working signal and the spare signal.

By using a two-fiber unidirectional ring, it is possible to apply the 1 + 1 protection method, so that it is possible to perform failure recovery at a very high speed. When the 1 + 1 protection scheme 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 longer than one round of the ring.

[0008] In addition, SONET (for example, TH Wu,
"Fiber Network Service Survivability," Artech
house, 1992), a two-fiber unidirectional ring may be used to perform failure recovery by looping back the failure section (loopback) (eg, TH Wu, "Fib").
er Network Service Survivability, "Artech hou
se, 1992). As explained for the 4-fiber ring,
Since loopback is performed, the total transmission distance may be longer than one round of the ring.

On the other hand, by using a four-fiber bidirectional ring, failure recovery is performed at a relatively high speed (SONET).
In the case of the above, it is possible in about 50 msec).

By using the above-described configuration, it is possible to configure a communication network that performs high-speed failure recovery.

[0011]

However, by using a two-fiber unidirectional ring (1 + 1 protection method), a backup path is prepared for the working path in such a way that a path opposite to the path on the ring corresponds to 1: 1. Therefore, it is necessary to always transmit the optical signal, and the use efficiency is reduced and the cost is increased.

On the other hand, when a system that performs loopback is used for recovery from a fault such as a four-fiber bidirectional ring, if a path close to one round of the ring is used as the working path, it is close to two rounds by loopback. Optical transmission must be performed. Even when a path of about half a ring is used as a working path, optical transmission for about one and a half rounds must be performed.

An object of the present invention is to construct a ring system having a path recovery efficiency and a failure recovery function capable of setting a long overall ring length. It is to reduce the cost.

[0014]

A first aspect of the present invention is a communication network, comprising a plurality of communication node means for inserting and separating a signal, and a plurality of transmission paths, wherein the plurality of communication node means are provided. At least a first ring, a second ring, a third ring, and a fourth ring are configured so as to configure the same network topology by the connection of the plurality of transmission paths, and the first ring includes a working ring. Transmitting the signal clockwise or counterclockwise, and the spare resources for the working signal of the first ring are shared by the second ring transmitting the signal in the opposite direction to the first ring; In the ring, the working signal is transmitted in the opposite direction to the first ring, and the spare resource for the working signal in the third ring is transmitted by the fourth ring, which transmits the signal in the opposite direction to the third ring. In a shared communication network, a signal is inserted at an i-th communication node means of the plurality of communication node means, and a signal is inserted at a j-th communication node means via the first ring. Regarding the terminating first communication, when the j-th communication node means detects a failure in the first communication, the j-th communication node means bypasses the communication path of the first communication via the second ring. A request message is sent to the i-th communication node means, and when the i-th communication node means receives the request message, the communication path of the first communication is transferred from the first ring to the second ring via the first ring. By performing the recovery, the first communication is recovered from failure by inserting the signal into the mth communication node means of the plurality of communication node means, and the nth communication signal is inserted through the third ring. Communication Means for terminating a signal by means, when the n-th communication node means detects a failure in the second communication, bypasses the communication path of the second communication via the fourth ring. Sends a request message to the m-th communication node means, and when the m-th communication node means receives the request message, passes the communication path of the second communication through the third ring. Switching to the fourth ring is performed to recover from the failure of the second communication.

[0015] A second invention is a communication network, comprising 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 connected to the plurality of transmission paths. At least a first ring such that the connections form the same network topology;
And a second ring, wherein the first ring transmits signals clockwise or counterclockwise, and the second ring transmits signals counterclockwise to the first ring. Wherein the first ring has, in a transmission band, a protection resource band shared between working signals transmitted by the second ring, and the second ring has the first ring in a transmission band. It has a spare resource band shared among the working signal groups transmitted by the ring, and inserts a signal at the i-th communication node means of the plurality of communication node means and passes the signal through the first ring Concerning the first communication terminating the signal at the j-th communication node means, when the j-th communication node means detects a failure in the first communication, the communication path of the first communication is changed to the second communication path. Communication configured using ring backup resource bandwidth Sends a request message to the i-th communication node means so as to bypass the request, and when the i-th communication node means receives the request message, changes the communication path of the first communication to the second ring. The first communication is recovered from the failure by switching to a communication path constituted by a spare resource band, and a signal is inserted by an m-th communication node of the plurality of communication nodes, and a signal is inserted into the second ring. The second communication terminating the signal at the nth communication node means via the second communication node means when the nth communication node means detects a failure in the second communication.
A request message is sent to the m-th communication node means so as to bypass the communication path of the communication of (a) to the communication path constituted by the reserve resource band of the first ring, and the m-th communication node means Upon receiving the request message, the communication path of the second communication is switched to a communication path constituted by a spare resource band of the first ring, thereby performing a recovery from the failure of the second communication.

According to a third aspect of the present invention, there is provided a communication network node device, wherein a plurality of or a single multiplexed signal input terminal for inputting a multiplexed signal, a plurality of or a single inserted input terminal for inserting a signal, and the multiplexed signal input terminal. A plurality or a single demultiplexed output terminal for outputting a demultiplexed signal obtained by demultiplexing the input multiplexed signal, and 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 insertion / separation / multiplexing means, a plurality or a single external input terminal connected to another node, a plurality or a single external output terminal connected to another node, and a plurality or a single device having a plurality of output terminals Switch means, a plurality of or a single merging means, a plurality or a single signal input terminal, and a plurality or a single signal output terminal, wherein the external input terminal is connected to a multiplex signal input terminal of the insertion separation multiplexer. The multiplexed signal output terminal of the insertion / demultiplexing unit is connected to the external output terminal, the signal input terminal is connected to the switching unit, and the switching unit is connected to the insertion input terminal of the insertion / demultiplexing unit. The separation output end of the insertion / demultiplexing unit is connected to the junction unit, and the junction unit is connected to the signal output terminal.

According to a fourth aspect of the present invention, there is provided a communication network node apparatus, wherein a plurality of or a single multiplexed signal input terminal for inputting a multiplexed signal, a plurality of or a single inserted input terminal for inserting a signal, and the multiplexed signal input terminal. A plurality of or a single demultiplexed output terminal that outputs a demultiplexed signal obtained by demultiplexing the input multiplexed signal, and a multiplexed signal output terminal that multiplexes and outputs the signal input to the insertion input terminal and the demultiplexed signal. A plurality or a single insertion / separation / multiplexing means, a plurality or a single external input terminal connected to another node, a plurality or a single external output terminal connected to another node, and a plurality or a single device having a plurality of output terminals , A plurality of or a single merging means, a plurality of or a single signal input terminal, a plurality or a single signal output terminal, and exchange of control information with other nodes, and based on the control information, the optical switch. A plurality or a single control means for controlling switching of the means, wherein the external input terminal is connected to a multiplex signal input terminal of the insertion / demultiplexing means, and a multiplex signal output terminal of the insertion / demultiplexing means is connected to the external output terminal. The signal input end is connected to the switch means, the switch means is connected to the insertion input end of the insertion / separation / multiplexing means, the separation output end of the insertion / separation / multiplexing means is connected to the merging means, The merging means is connected to the signal output terminal.

According to a fifth aspect of the present invention, there is provided a communication network node device, wherein 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 the multiplexed signal input end. A plurality of or a single demultiplexed output terminal that outputs a demultiplexed signal obtained by demultiplexing the input multiplexed signal, and a multiplexed signal output terminal that multiplexes and outputs the signal input to the insertion input terminal and the demultiplexed signal. A plurality or a single insertion / separation / multiplexing means, a plurality or a single external input terminal connected to another node, a plurality or a single external output terminal connected to another node, and a plurality or a single device having a plurality of output terminals Switch means, a plurality or a single merging means, a plurality or a single signal input end, a plurality or a single signal output end, and a plurality or a single signal monitoring means for monitoring a signal input to the merging means A plurality of or a single control means for exchanging control information with another node and controlling switching of the optical switch means, wherein the external input terminal is connected to a multiplex signal input terminal of the insertion / demultiplexing means, A multiplexed signal output terminal of the multiplexing 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 an insertion input end of the insertion / separation / multiplexing means; Is connected to the merging means, the merging means is connected to the signal output end, and the control means monitors a signal input to the merging means of the signal monitoring means and a signal from the other node. The switching means is controlled based on a result of the transfer of the control information.

According to a sixth aspect of the present invention, there is provided a failure recovery method, wherein an input terminal of a first communication network node device in which spare resources constituting a detour communication path exist in a ring network shared by a plurality of working signals. From the communication network to the output end of the second communication network node device existing in the ring network, when the second communication network node device detects the communication failure, Sending a request message to the first communication network node device, and when the first communication network node device receives the failure recovery request message, switching means of the first communication network node device The communication is recovered by switching to a detour path in the reverse direction to the communication using To.

A seventh invention is the communication network according to claim 1 or 2, wherein the communication node means is an optical communication node means, the transmission path is an optical transmission path, and the communication is an optical communication path. It is characterized by communication.

According to an eighth aspect of the present invention, in the communication network / node apparatus according to the third, fourth or fifth aspect, the insertion / demultiplexing means is an optical signal insertion / demultiplexing means. I do.

According to a ninth aspect of the present invention, there is provided the communication network / node apparatus according to claim 3, 4, or 5, wherein the insertion / demultiplexing means is means for performing wavelength insertion / demultiplexing. And

According to a tenth aspect of the present invention, there is provided the failure recovery system according to the sixth aspect, wherein the first communication network node device and the second communication network node device are the third or fourth or the fourth communication network node device. Item 5 is a communication network node device according to item 5.

An eleventh invention is the failure recovery system according to claim 6, wherein the first communication network node device and the second communication network node device are each configured as described in claim 8 or 9. It is a communication network node device.

According to a twelfth aspect, in the communication network according to the seventh aspect, the optical communication is wavelength-division multiplexed optical communication.

A thirteenth aspect of the present invention is the communication network node device according to claim 9, wherein said plurality or singular signal input terminals and said plurality or singular signal output terminals terminate signals not necessarily having the same signal speed. Input terminal and output terminal.

A fourteenth invention is a communication device, comprising:
A first input terminal to which a working signal from the first route is input, a first output terminal to which a working signal from the first route is output,
A second input terminal to which a spare signal from the first route is input, a second output terminal to which a spare signal from the first route is output, and a working signal from the second route. A third input terminal for inputting, a third output terminal for outputting a working signal from the second route, and a fourth input terminal for receiving a spare signal from the second route.
, A fourth output terminal from which a preliminary signal from the second path is output, a switch means, first and second insertion signal input terminals, and first and second branch signal outputs. And the switch means comprises a connection between the first and fourth input terminals and the first branch signal output terminal, and a connection between the second and third input terminals and the second branch terminal. A connection with a signal output terminal, a connection between the first insertion signal input terminal and the first and fourth output terminals, and a connection with the second insertion signal input terminal and the second and third outputs. The connection with the end is possible.

A fifteenth aspect of the present invention is the communication apparatus according to the fourteenth aspect, wherein a means for monitoring an input signal is connected to the first to fourth input terminals.

A sixteenth aspect of the present invention is the communication apparatus according to the fifteenth aspect, wherein means for transmitting / receiving monitoring control information to / from another node, means for transmitting / receiving monitoring control information to / from the other node, and monitoring the input signal. And means for controlling the switch means based on information obtained from the means.

The operation of the present invention will be described below.

In the system described in the present invention, when a failure occurs, recovery is performed by using a shared spare resource and setting and switching a detour around the path in which the failure has occurred in the reverse direction in units of optical paths. In addition, there is no need to perform loopback switching, and it is not necessary to perform optical transmission for one or more rounds. or,
In the present invention, the path switching method is used, but the spare resources are shared, so that the path accommodation efficiency is increased. This is because, when the conventional 1 + 1 protection method is used, the backup path must always be operated, so that one wavelength in one round of the ring and a maximum of two paths (up and down directions between certain nodes). However, in the system described in the present invention, since the spare resources are shared among all the working resources, the number of nodes between the maximum adjacent nodes in one wavelength in one working ring (the number of nodes) ) Can accommodate the path. Since the loopback is not performed and the path accommodation efficiency is simultaneously improved, the cost of the communication network is reduced.

In particular, in the case of a wavelength division multiplexing system, it is difficult to monitor in units of wavelengths originally bundled, and it is necessary to perform management in units of wavelengths. The cost can be reduced because it can be introduced as it is. In particular, a system having a small number of paths such as a wavelength multiplexing system (the number of paths does not increase because there is a physical restriction on the number of wavelength multiplexes available) or a system handling a high speed signal in which many low speed signals are multiplexed. When the present invention is applied to the present invention, the number of paths to be managed can be reduced, the management cost is reduced, and the effect is further increased.

[0033]

Next, embodiments of the present invention will be described with reference to the drawings.

The first embodiment will be described with reference to FIG. FIG. 1 is a block diagram of an optical wavelength division multiplexing communication network according to a first embodiment of the present invention. 105-1
08 is an optical communication network node. These nodes form a four fiber ring by connecting the fibers so as to form a ring topology. 101 and 103 represent working rings, and 102 and 104 represent spare rings. Each node includes a clockwise working signal processing unit (121 in node 108) for processing a clockwise working ring signal, and a counterclockwise working signal processing unit (node 108 for processing a counterclockwise working signal). Has 122). The clockwise working section is the working ring 101
And the signal (at the time of failure) of the counterclockwise spare ring 102 are handled. The counterclockwise working signal processing unit handles the signal of the counterclockwise working ring 103 and the signal of the clockwise backup ring 104 (when a failure occurs). Each node separates and inserts the wavelength-multiplexed demultiplexed signal. For example, from the node 105, the optical signals 109 to 112 are wavelength division multiplexed and output. Reference numerals 109 and 110 denote optical signals wavelength-division-multiplexed and demultiplexed from the working ring 101, and reference numerals 111 and 112 denote optical signals wavelength-multiplexed and demultiplexed from the working ring 103. 1
Optical signals 13 to 116 are inserted. Reference numerals 113 and 114 denote optical signals to be inserted into the working ring 101.
Is an optical signal 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 wavelength of the main signal light for transmitting data. Thus, for example, 113,
It is possible to assign a wavelength of λ1 to 115 and a wavelength of λ2 to 114 and 116. In addition to the main signal light, a 1.3 μm band control signal light (wavelength: λs) is also wavelength-multiplexed with the main signal light and transmitted for exchanging control signals between adjacent nodes. Although only the node 105 is shown for the separation signal and the insertion signal, the other nodes 106 to 108 have the same functional configuration.

FIG. 2 shows a clockwise working signal processing unit 200 (12 in FIG.
1) is shown. Reference numerals 201 and 205 denote external input terminals.
Reference numerals 4208 denote external output terminals, each of which is 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 terminal 201, and is connected from the external output terminal 208 to the node 107. The optical fiber of the spare ring 102 is connected from the node 107 to the external input terminal 205, and is connected from the external output terminal 204 to the node 105. 221,
A control signal separator 223 separates the optical signal input from the external input terminal, and sends out the 1.5 μm wavelength-multiplexed main signal light to the optical ADM units 209 and 210, respectively.
μm control signal light (λs)
Input to 6. As the control signal separators 221 and 223, it is possible to use a WDM coupler that separates a 1.3 μm band wavelength and a 1.5 μm band wavelength. 202,
203 denotes an optical signal (λ1 or λ2) demultiplexed by wavelength division.
, And 206 and 207 are separate input terminals for inputting one-wave optical signal (λ1 or λ2), and are respectively a SONET terminator and an ATM switch (for example, TH Wu, “Fiber Network”). ServiceSurviv
209, 210 are optical ADM units. The optical ADM unit 209 performs wavelength multiplexing on wavelength multiplexed light input from the external input terminal 201. 218,220 separated
, Or multiplexed and output to the external output terminal 208. The optical ADM unit 210 multiplexes and demultiplexes the wavelength multiplexed light input from the external input terminal 205 to 217 and 21.
9 or multiplexed and output to the external output terminal 204. Reference numerals 217 to 220 denote optical splitters.
A part of the optical signal output by wavelength division multiplexing and demultiplexing from the M unit is tapped (for example, for 10% of optical power), connected to the monitoring controllers 215 and 216, and most of the remaining optical signals (for example, 90%). % Of the optical power) is output to the optical switch 213 and the optical switch 214.

Reference numerals 211 to 214 denote 2 × 1 optical switches, and mechanical optical switches can be used. Optical switches 213 and 214 are connected to wavelength multiplexed and demultiplexed outputs from optical ADM units 209 and 210 by using an optical fiber. One of the wavelength division multiplexed optical signals input to the terminal 205 is selected and output to the demultiplexing output terminals 202 and 203, respectively. Similarly, optical signals of one wavelength are input to the optical switches 212 and 211, respectively. Can be selected to output to either of the above.

Reference numerals 215 and 216 denote monitoring controllers, which monitor the tapped optical signals and control the optical switches 211 to 214.
To send a switching control signal. Monitoring controller 215, 2
In step 16, an optical receiver is installed at the input end of the monitoring control unit to monitor the bit error rate of the input optical signal and monitor the transmission quality of the optical signal (using a SONET frame as the optical signal and using B1 It is possible to monitor the bit error rate by monitoring the bytes; for example, TH Wu,
"Fiber Network Service Survivability," Artec
h house, 1992). In the node 108, the clockwise working signal processing unit normally monitors the error rate of the optical signal transmitted from the external input terminal 201 to the working ring 101, and determines whether the optical signal is transmitted normally. to manage. The monitoring control unit is connected to the optical switches 211 to 214, and based on information from the monitoring control unit, the optical switches 211 to 214.
It is possible to switch.

Control signal multiplexers 222 and 224 are connected in front of the external output terminals 204 and 208, respectively.
The control signal light (1.3 μm band) and the main signal light (1.5 μm) transmitted from the supervisory controllers 215 and 216 to other nodes
Band) is wavelength-multiplexed. As the control signal multiplexer, a WDM coupler can be used similarly to the control signal separators 221 and 223. Control signal separators 221, 22
3. By superimposing and separating the control signal light on the main signal light using the control signal multiplexers 222 and 224, it is possible to exchange control signals with other nodes.

Since the control signal light from the other node is also input to the monitoring controller, both the switching based on the control information from the other node and the switching based on the monitoring result of the optical signal of the own node are possible. .

The counterclockwise working signal processing unit can also use the same configuration as 200 in FIG. Similarly, a clockwise working signal processing section, a counterclockwise working signal processing section, and a working ring 10
3. It is possible to connect to the spare ring 104. Nodes other than the node 108 can also be configured similarly and connected to the optical fiber of the ring.

FIG. 3 shows an optical ADM unit 2 used in FIG.
09, 210. Reference numeral 300 denotes an optical ADM unit. Reference numeral 301 denotes a multiplexed signal input terminal for inputting a wavelength-multiplexed signal light, and reference numeral 306 denotes a multiplexed signal output terminal for outputting a wavelength-multiplexed optical signal. Reference numerals 302 and 303 denote demultiplexed signal output terminals for demultiplexing and outputting the optical signal input to the multiplexed signal input terminal 301. 304 and 305 are insertion signal input terminals for inputting one-wave optical signal. 314 is a wavelength multiplexing / demultiplexing device, 307 is a wavelength multiplexing wave device, and AWG
(Arrayed-waveguide grating
g: For example, K. Okamoto et al., "Fabrication of
unequal channel spacing arrayed-waveguidedemul
tiplexer modules, "Electron. Lett., 1995, vo
l.31, no.17, pp.1464-1465.) can be used. Reference numerals 310 and 311 denote optical gate switches, and a mechanical optical switch or a gate switch using a semiconductor optical amplifier can be used. 312,313
Is an optical splitter that splits the power of the input light into two, outputs one to separate output terminals 302 and 303, and outputs the other to optical gates 310 and 311 respectively. 3
Reference numerals 08 and 309 denote optical couplers.
4. Signal light from insertion signal 305 and optical gates 310 and 3
11 are combined and output. 3
Reference numeral 07 outputs wavelength-multiplexed light obtained by multiplexing the outputs from the optical couplers 308 and 309. Optical gate 310, optical gate 3
By turning 11 on or off, it is possible to select whether the signal to be input to the wavelength division multiplexer 307 is from the output of the optical splitter or from the insertion signal input terminal. It is possible. In the configuration of FIG. 3,
Since the light is split by the optical splitters 312 and 313, an optical signal is always output to the split signal output terminal.

Next, a description will be given of the failure recovery operation when the node configuration of FIG. 2 and the network of FIG. 1 are used with reference to FIG. 4 and FIG.

FIG. 4 shows a main signal, a control signal after a fault has occurred, and operation steps at each node in the network of FIG. Hereinafter, an optical path is defined as a period from when an electric signal is converted into an optical signal at a certain node and transmitted to another node, until the electric signal is converted again into an electric signal. 1 for optical path
Wavelengths correspond. 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: transmitting node) via the node 105 and uses the wavelength of λ1. Normally, the spare ring is not used, and an optical path is set in the spare ring and used only when a failure occurs. In the spare ring, all nodes are set in advance so that all optical signals arriving from other nodes are allowed to pass through as they are. this is,
This can be realized by setting the optical gates 310 and 311 in FIG. 3 to the On state in the spare ring. Now node 1
A description will be given of a failure recovery operation when a break failure occurs in all the optical fibers between the optical fiber 06 and the node 105. Since the optical fiber is broken, the optical path 401 is connected to the terminal node 108.
The monitoring controller 215 in the clockwise working signal processing unit of the node 108 first detects the deterioration of the bit error rate and recognizes the failure of the optical path 401 (step 1).

When the supervisory controller detects a fault 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 the source node 106 The monitoring controller is set in advance so as to send a switching request message to the destination using the control signal light (λS) in the direction in which no failure has occurred (step 3). The control signal light includes
The information can include a destination node, an optical path name, and control contents. For example, it can be realized by allocating information to the position and value of a framed bit like the section overhead of SONET. 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 to whether or not to request the switching. If a frame configuration in which a total of 17-bit bit strings are connected by the number of wavelengths is used, optical path switching request messages for the number of wavelengths can be transmitted collectively. In this case, it is possible to send a message amount that can cope with a single failure that an optical fiber between certain nodes is broken.

Using the control system set as described above, when the node 108 recognizes a failure in (step 1), the node 108 selects a signal from the backup ring 102 (the same wavelength as the working optical path: λ1). Then, the optical switch 213 is switched (step 2), and sends an identifier of the working optical path and a switch request message (λS) to the source node (step 3).

The node 107 receives the control signal light, but transfers it to the node 106 as it is because it is not a message addressed to the own node (step 4). When the control signal light arrives at the node 106, it is a message addressed to the own node.
The optical switch corresponding to 2 is switched and the working ring 101 is switched.
The optical signal (.lambda.1) of the working optical path 401 transmitted to the backup ring 102 is transmitted to the backup ring 102 (step 5). Node 10
7 is not set to receive the light having the wavelength of λ1 of the spare ring 102, and is in a state where the optical signal is allowed to pass to another node in advance as it is, and the node 108 has the wavelength of λ1 of the spare ring 102. (Step 2), the optical switch 21 of the node 108
3 selects and outputs the optical signal of wavelength λ1 from the protection ring 102 (formation of the protection optical path 402), and the failure of the working optical path 401 is recovered by using the protection optical path 402.

In this embodiment, after step 2 (switching of the optical switch 213), step 3 (sending a switch request message to the source node) is executed. The present invention can be practiced without any trouble even if the order is reversed. If the time required for message transmission governs the failure recovery speed, the message is transmitted first, so that the overall failure time is reduced.

FIG. 5 shows a sequence chart of the inter-node communication and the operation at the node. The vertical axis is the time axis,
The lower the time, the later the time.

FIG. 6 shows an example of a flowchart of control to be provided in the monitoring controller of each node in order to realize this sequence. Reference numeral 601 denotes a branch, which is classified according to whether or not a failure in the terminal signal of the own node is detected. The act of recognizing the failure of the own node termination signal is defined as (step 1). A procedure 602 confirms that no failure has occurred in the own node and recognizes that the failure recovery has been completed (step 6). 605 is a procedure,
By switching the optical switch, an arrangement for receiving an optical signal from the spare ring is made (step 2). 606 is a procedure for transmitting a control message to the source node of the failed optical path (step 3). 603
Is a branch, and it is determined 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, the control message is directly transferred to the other node (step 4). A branch 604 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 identifier of the optical path specified by the arrived control signal and switches the corresponding optical path to be transmitted to the spare ring.

If such a flowchart is applied to each node, a failure recovery as shown in FIG. 4 can be performed.

In this embodiment, the optical switch 213 of the receiving node of the optical path is switched in step 2, but the present invention can be implemented even if a method in which the receiving node is not switched in step 2 is used. Is self-evident. For example, the present invention can be implemented by the following method. Step 2 sends a request to the sending node. Node 107
Is not a control message addressed to itself, so it is transferred to the node 106 as it is. Thereafter, when the transmitting node receives the request, the transmitting node transmits an optical signal to both the working ring side and the protection ring side. The transmitting node notifies the receiving node that the optical signal has been transmitted to both the working ring and the protection ring. When the receiving node of the optical path receives information indicating that the optical signal is transmitted to both the working ring and the protection ring, the receiving node of the optical path sets the optical switch 213 to receive the optical signal from the protection ring. Switching and detour paths are configured, and failure recovery is completed.

In the above, the method of recovering a failure of the working optical path having the wavelength of λ1 has been described. It is possible to perform failure recovery of all the optical paths passing through (including those having different source nodes and terminal nodes). This will be described below. When a single fault occurs in a fiber or a node, a fault occurs in the number of wavelength-multiplexed optical paths. 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 that transmits a signal in the direction opposite to the transmission direction of the working ring, wavelength collision (the same wavelength can be assigned to the optical path in one optical fiber and separated). It is possible to allocate a spare optical path without the loss of the optical path. Therefore, for any single failure, the failure of all the optical paths passing therethrough can be recovered. In addition, even when multiple failures occur, it is possible to cope with the situation where a route opposite to the working optical path is safe.

The method of recovering the failure of the working optical path of the working ring 101 using the spare ring 102 as a shared spare resource and the node configuration thereof have been described above. The working ring 103 (the reverse of the working ring 101) has been described. The same node configuration and fault recovery method can be applied to the backup ring 104 and signal transmission in the same direction. 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 resources are shared so that in preparation for the next failure, The original path is restored so as to be transmitted using the working optical path 401 without using the optical path 402.

By using the first embodiment, the failure recovery is performed without performing the loopback switching, so that the transmission distance of the optical signal can be reduced. Therefore, when the distance over which light can be transmitted as it is is determined, it is possible to configure a ring having a longer overall length than a system that performs loopback. Also, unlike the 1 + 1 protection, the spare resources are not used exclusively and the spare resources are shared, so that the number of working optical paths to be operated can be increased. In the 1 + 1 scheme, when the shortest route is set as the communication in the up direction, the down direction always uses the route around the same direction, so that the accommodation of the optical path becomes inefficient. For example, in the 1 + 1 method, 1
One wavelength can form only two optical paths per ring (in FIG. 11, the optical path 112
2 and the optical path from node 1107 to node 1106).
By using this configuration, for example, as shown in FIG. 7, up to four optical paths can be configured with one wavelength. In FIG. 7, reference numerals 701 to 704 denote working optical paths having a wavelength of λ1,
101 indicates a working ring and 102 indicates a spare ring. 70
The protection resource for the working optical paths 1 to 704 is the protection ring 102 and is shared between the respective working optical signals. For example, a backup optical path for the working optical path 701 uses the wavelength λ1 on the backup ring 102 in a path of node 106 → node 105 → node 108 → node 107. The backup optical path for the working optical path 702 is on the backup ring 102 from the node 107 to the node 106 to the node 105.
→ The wavelength λ1 can be used in the route of the node 108. In the section from the node 106 to the node 105 to the node 107, the same wavelength λ1 is used and shared as a backup optical path. Since these spare optical paths are independent events (for a single failure), the spare ring 102
This is because the spare resource of λ1 in the middle can be shared between the working optical paths 701 and 702. Similarly, in the case of FIG. 7, the working optical paths 701 to 7
04, the wavelength λ1 which is a spare resource of the spare ring 102.
Will be sharing. The same applies to optical paths of other wavelengths. Further, since the spare resources are shared, the optical path can be set independently for the clockwise working ring and the counterclockwise working ring in communication between certain nodes. Setting to makes efficiency higher.

However, when the control signal is transferred at another wavelength as in this embodiment, all of the working optical paths 701 to 704 need not exist. For example, the working optical paths 701 and 7
Even if only 03 is present, the control signal is transferred at another wavelength at another wavelength, so that it is possible to perform inter-node signaling, and the present invention can be implemented.

Further, messaging for failure recovery is as follows.
At best, you only need to go around the ring once, so SONET
It is possible to perform the fault recovery at the same speed as the operation speed of the fault recovery of the four-fiber bidirectional ring.

In the 1 + 1 protection method, since an optical signal is always transmitted to the protection path, the protection resource is used even when no failure occurs. On the other hand, when the present configuration and method are used, when no failure occurs, a spare resource can be used, and a low-priority optical path can flow there (standby access). When a failure occurs because the priority is low, it may be used as a backup optical path for another high-priority optical path, but it is possible to configure a low priority optical path when no failure occurs There are advantages.

Further, in the SONET system, if a signal that bundles paths is monitored in units of a monitoring line (a unit of a signal in which a path between adjacent nodes is multiplexed), the quality of a path signal (for example, an error rate) can be reduced. It was possible to do. However, in a wavelength division multiplexing system, it is originally necessary to manage wavelengths between nodes, and it is difficult to operate a management system only by managing a bundle of optical paths.
Therefore, the configuration and method of the present invention can be applied to a management and monitoring system in the case of performing a fault recovery for each optical path, which is more effective.

In the current SONET system, 50M
Although b / s is handled as a path unit, a path managed by handling switching in a path group unit (for example, a 2.5 Gb / s unit in which a signal of 50 Mb / s is bundled) is bundled. And the effect of the application of this method increases. Even in the case of light, since the number of multiplexed wavelengths is limited to some extent due to physical restrictions, the number of paths does not increase very much, which is more effective.

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 perform switching to recover from the failure of the optical path. A node in the middle of the path only needs to transfer the switch request message sent from the terminal node to the source node, so that control is simple and the fault recovery speed is high.

Further, according to the present invention, since the terminal node of the optical path detects a failure, it is possible to detect a failure for each wavelength. In the case of the conventional four-fiber ring using batch switching of wavelength division multiplexing, monitoring is performed collectively by wavelength division multiplexing without monitoring at the terminal node of the optical path. However, the present invention has solved this problem.

Further, since protection is performed for each wavelength (optical path), a protection function is provided for each wavelength, and it is possible to set a protection function. By setting the desired wavelength without the protection function, it is possible to use the protection function of the upper layer (for example, the protection defined by SONET). This is the case with the conventional 4 method of performing wavelength multiplex batch switching.
This is not possible with fiber rings.

Next, a second embodiment will be described. In the first embodiment, the configuration and the method of the four-fiber ring have been described. In the second embodiment, the case of the two-fiber ring will be described. A two-fiber ring has a clockwise ring and a counterclockwise ring. λ1
It is assumed that four wavelengths .lambda. To .lambda.4 are wavelength multiplexed, and .lambda.1 and .lambda.2 are allocated to the wavelength of the working optical path and .lambda.3 and .lambda.4 are allocated to the wavelengths of the backup optical path in both rings. Λ1, in the clockwise ring
The spare resources corresponding to the working optical path configured using λ2 can be allocated to λ3 and λ4 of the counterclockwise ring, and the working optical path configured using λ1 and λ2 in the counterclockwise ring can be allocated. Can be allocated to λ3 and λ4 of the clockwise ring. Therefore, 2
A fiber ring can be considered in the same manner as a four-fiber ring. The resources of λ1 and λ2 of the clockwise ring are made to correspond to the working ring 101 of FIG.
3, .lambda.4 correspond to the spare ring 102 of FIG. 1, the counterclockwise rings .lambda.1, .lambda.2 correspond to the working ring 103 of FIG. Specifically, 4 described in the first embodiment.
It can be seen that the same operation as the fiber ring is possible. Since the node configuration uses λ1 and λ2 for the working optical path and λ3 and λ4 for the standby optical path, for example, compared to the four-fiber node configuration of FIG.
12 is inserted between the output end of the optical switch 212 and the optical ADM unit 209, and a wavelength converter for converting an input optical signal into λ1 is inserted between the output end of the optical switch 212 and the optical ADM unit 210. Is inserted between the output terminal of the optical switch 211 and the optical ADM unit 209, and a wavelength converter that converts the input optical signal into λ2 is inserted between the output terminal of the optical switch 211 and the output terminal of the optical switch 211. It is necessary to insert a wavelength converter for converting the input optical signal into λ4 between the optical ADM unit 210 and the optical ADM unit 210. As a wavelength converter, use a method in which an optical signal is once converted to an electrical signal using a photodiode, and then the laser signal of a desired wavelength is modulated and converted to another wavelength using the electrical signal. Is possible.

In this case, the wavelength converter may be a device that converts an optical signal into an electrical signal once and then converts the optical signal into an optical signal having a desired wavelength by an optical transmitter that outputs a desired wavelength again. It is self-evident that this can be done.
Further, it is obvious that the present invention can be implemented even if an electric switch is used as the switching means without using the optical switch.

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, so that it is particularly effective 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. Is increased.

In the second embodiment, a wavelength converter having a fixed wavelength output is inserted in the node configuration shown in FIG. 2. However, it is obvious that the present invention can be applied to a wavelength converter having a variable wavelength output. It is. 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, a method of converting an optical signal into an electric signal and then converting it again into an optical signal is used as a wavelength converter. It is obvious that the present invention can be implemented by using a cross gain modulation effect or a wavelength converter using the cross phase modulation effect.

Next, a third embodiment of the present invention will be described. The third embodiment is a case of a two-fiber ring as in the second embodiment.
And the second ring transmit optical signals in opposite directions. The wavelength for transmitting the working signal of the first ring is λ
1, λ2, and as a spare resource, the wavelength λ of the second ring to the working optical path of the wavelength λ1 of the first ring.
1. Second working optical path of wavelength λ2 of first ring
Is used. Λ3, λ4 are used as the wavelengths for transmitting the working signal of the second ring, and the first resource is used as a spare resource for the working optical path of the second ring at the wavelength λ3.
Λ3 of the first ring and λ4 of the first ring are used for the working optical path of 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 second wavelength is assigned to the second fiber ring.
It is no longer necessary to use the wavelength converter used in the embodiment. In the second embodiment, in a certain source node, the wavelength λ1 is used for the working optical path and the wavelength λ3 is used for the backup optical path.
However, the wavelength converter is necessary because the wavelength used for the working optical path and the wavelength used for the backup optical path are the same if the third embodiment is used. is there.

When the third embodiment is used, the same effects as those described in the second embodiment are obtained, except that the wavelength converter is not required.

In the embodiment of the present invention, the case of a fiber failure has been described. However, it is obvious that the same method can be used to recover from a failure such as a node failure.

In the embodiment of the present invention, the method of monitoring the bit error rate is used for monitoring the optical path. However, the monitoring may be performed by using the method of monitoring the optical power. This can be realized by installing a photodiode at the input end and monitoring its photocurrent. Other, light S
It is possible to apply monitoring / N (signal-to-noise ratio). It is possible to obtain the S / N of the light by obtaining the ratio between ASE (spontaneous emission light noise) and the signal light.

In the embodiment of the present invention, a sequence as shown in FIG. 5 is used. However, for example, the present invention can be implemented without any problem even if the order of step 2 and step 3 is changed.

It is self-evident that the present invention can be implemented using any sequence as long as it can finally switch the route of the terminal node of the optical path.

In the embodiment of the present invention, a flowchart as shown in FIG. 6 is used for controlling each node. For example, branch 603 and its associated procedure 6
07 and the branch 604 and the accompanying procedure 608 are grouped in reverse order (after the branch procedure 602, the branch 60
It is obvious that the present invention can be implemented without any trouble.

In the embodiment of the present invention, a ring using an optical path in the wavelength division multiplexing system has been described.
It is obvious that the present invention is applicable to a system in which paths such as SONET and SDH are time-multiplexed. However, since the transmission distance of the optical signal can be reduced by not performing the loop-back switch, it is possible to increase the ring length. Is applied more effectively (in a SONET ring, an optical signal is converted into an electric signal for each node to reproduce the signal). Also, the optical path is 10 Gb / s regardless of whether it is a 2.5 Gb / s optical signal.
Irrespective of the optical signal, there is only one optical path.
Even in a system in which the Gb / s optical path and the 10 Gb / s optical path coexist, the same node configuration and failure recovery method as in the first embodiment can be used, and the flexibility is high. .

For example, in FIG. 7, the working optical path 701
Optical path of 2.5 Gb / s optical signal, working optical path 7
02 may be an optical path of a 10 Gb / s optical signal, the working optical path 703 may be an optical path of a 600 Mb / s optical signal, and the working optical path 704 may be an optical path of a 155 Mb / s optical signal. The present invention can be implemented. What is shared in the spare ring is the spare wavelength. Each backup wavelength can be used for an optical signal of any speed (speed in a transmittable range) because of the signal speed independence of light.
Therefore, as long as signaling (exchange of control information) between nodes is possible even if the signal speed of each working optical path is different, an optical path of an optical signal of any signal speed can be configured using the backup wavelength. Specifically, the working optical path 701 (2.5
Gb / s) as a detour, from node 106 to node 10
2.5G on the route 5 → node 108 → node 107
A detour optical path of b / s is configured. The working optical path 702 (1
0 Gb / s) as a detour, from node 107 to node 1
A bypass optical path of a route 06 → node 105 → node 108 is configured. In this case, the detour path between the working optical path 701 and the working optical path 702 is a detour optical path using the same wavelength λ1 in the section between the nodes 106, 105, and 108 in the backup ring. (The case where a failure occurs in the working optical path 701 and the case where a failure occurs in the working optical path 702). Even if λ1 is shared, the speed does not need to be the same because of the signal speed independence of light, so that the present invention can be applied even if λ1 is used at different speeds as described above.

In the embodiment of the present invention, the method using the optical path in the wavelength division multiplexing system has been described.
TM VP (Virtual Path) and VC (Vi
It is obvious that the present invention can be applied to a real channel as long as it is a ring network.

In the embodiment of the present invention, the configuration of FIG. 3 is used as the configuration of the optical ADM unit, but the configuration of FIG. 8 and the configuration of FIG. 9 can be used.

FIG. 8 shows another embodiment of the configuration shown in FIG. It is configured to switch to an insertion signal input terminal or a separation signal output terminal. In the configuration of FIG. 3, the optical signal is always output to the separation signal output terminal. It is output to the separation signal output terminal only when it is in the cross state.

FIG. 9 shows another embodiment of the configuration shown in FIG. 3, in which a part of the output of the wavelength division multiplexer is directly connected to the wavelength division multiplexer, and another part is output. Is directly connected to the separation signal output terminal. These cannot switch the operation of separation and insertion, but can perform the failure recovery operation of the present invention by applying to the optical ADM unit of FIG.

Even if another configuration or a combination of these configurations is used, a multiplexed signal is input, a part of the multiplexed signal is output, a part of the multiplexed signal is input to the multiplexer, and a part is input to the multiplexer. It is obvious that the present invention can be applied to any configuration that can input an insertion signal. FIG.
Regarding the addition and dropping of a signal of one wavelength, the communication device has a clockwise working processor configuration (1251) shown in FIG. 2 and a counterclockwise working processor (1250) having the same configuration but a different connection destination. (Corresponding to claim 14). 120
1 to 1204 indicate input terminals, and 1205 to 1208 indicate output terminals. Reference numerals 1213 to 1216 denote optical switches. The input terminal 1202 and the output terminal 1207 are connected to a clockwise working ring, and the input terminal 1203 and the output terminal 1206 are connected to a counterclockwise spare ring which is a spare ring of the clockwise working ring. The input terminal 1204 and the output terminal 1205 are connected to a counterclockwise working ring, and the input terminal 1201 and the output terminal 1208 are connected to each other.
It is connected to the clockwise spare ring which is the spare ring of the counterclockwise working ring. For example, the configuration of FIG.
By connecting four parts (for four fibers), it is possible to configure a ring for a certain wavelength. The connection at this time relates to the first optical ADM unit (for the counterclockwise working ring), in which the separated signal output terminal 902 is connected to the input terminal 1201, and the output terminal 1208 is connected to the insertion signal input terminal 903. Further, with respect to another second optical ADM unit (for a spare ring for the counterclockwise working ring), the separated signal output terminal 902 is connected to the input terminal 1204, and the output terminal 1205 is connected to the insertion signal input terminal 903. Regarding another third optical ADM unit (for a clockwise working ring), the separated signal output terminal 902 is connected to the input terminal 1
203, and the output terminal 1206 is connected to the insertion signal input terminal 90.
Connect to 3. Regarding another fourth optical ADM unit (for a spare ring for a clockwise working ring), a separated signal output terminal 90
2 is connected to the input terminal 1202, and the output terminal 1207 is connected to the insertion signal input terminal 903. Hereinafter, the term “path” refers to a communication path passing through the same path. If it is connected to two different routes and it is possible to accommodate the working signal and the protection signal in each of the routes, the working system and the protection system of the two routes are configured using the configuration of FIG. Figure 9 above
The present invention can be implemented by connecting as in the example of connecting with. In a wavelength multiplexed system,
It is necessary to connect the communication device to the optical ADM unit.
However, for a single-wavelength system, it is possible to construct a ring that can recover from a failure by using only this device without connecting to the optical ADM unit. Further, by adding a monitoring means to the configuration of FIG. 12, it is possible to always determine whether or not a failure has occurred in the received signal.

The configuration shown in FIG. 13 is different from the configuration shown in FIG. 12 in that input signal monitoring means, means for transmitting / receiving control information to / from another node,
This is a configuration in which means for performing switch control based on such information is added (corresponding to claim 16). By adding these, full automation of the failure recovery switching becomes possible.

In the embodiment of the present invention, 1.
Although an optical signal having a wavelength in the 5 μm band and an optical signal having a wavelength in the 1.3 μm band are used for the control signal system, the use of these wavelengths is limited as long as the main signal system and the control signal system can be separated. Obviously it is not.

In the embodiment of the present invention, a frame structure is used as a method of transferring a control signal to another node. The first 8 bits are the destination node name, the next 8 bits are the optical path identifier, and the next 1 bit , The presence / absence of a switching request is assigned. However, even if this is not the same, any bit assignment method may be used as long as the path recovery request is transmitted to the source node. Also, there is no need to assign information to bits,
It is also possible to use message-oriented communication. It is also possible to use packet communication, frame relay, and communication using ATM.

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.
It is obvious that there is no need to use a wavelength different from the main signal, and any medium that can transfer control information can be applied. For example, the present invention can be applied to a case where control information is exchanged between nodes using a system in which a radio signal or a subcarrier is superimposed on an optical signal and transmitted, or a control signal is exchanged using a telephone line. it is obvious. Also, it is obvious that the present invention can be implemented even if a control signal is embedded in part of the main signal and transferred, as long as the control signal can be exchanged with another node. is there.

In the embodiment of the present invention, the event of detecting the failure of the local node termination signal is used as a trigger for starting the failure recovery operation. However, the failure recovery operation is started by a failure notification from another node or another network device. However, it is clear that the present invention can be implemented without any trouble. For example,
Even if a method is used in which a node at a stage preceding the node that terminates 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, a failure recovery operation is performed to perform the failure recovery operation. The invention can be implemented without hindrance.

In the configuration of the present invention, when no fault has occurred, the spare ring is set to allow all optical signals to pass. It is obvious that the present invention is applicable. However, if this method is used, the optical gate is switched after the switch request message arrives, so that the failure recovery time may be delayed.

In the embodiment of the present invention, a case has been described where the traffic between nodes is symmetrical in the up direction and the down direction. System with only one-way communication)
However, it is obvious that the present invention can be applied.

In the embodiment of the present invention, a system using one fault recovery system in one ring system has been described. However, the present invention can be realized by combining the configuration and method of the present invention with other systems such as the conventional 1 + 1 protection system. It is. 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. Further, it is not always necessary to detour in the direction opposite to the transmission direction of the working optical path. For example, when 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 this case, the switch request message is sent in both clockwise and counterclockwise directions.

In the embodiment of the present invention, the optical switch 21
Although a mechanical optical switch is used as 1-214, any optical switch that satisfies the performance such as crosstalk and loss can be used as an optical switch using the electro-optical effect, an optical switch using the thermo-optical effect, The present invention can be implemented by an optical gate switch using an amplifier.

In the embodiment of the present invention, the optical switch 21
An optical switch in which a signal is not distributed to another path when a certain path in the switch is made conductive as 1-214 is used. It is obvious that the present invention can be applied even if a multicast-capable switch) is used, provided that the multicast function is blocked by a gate.

In the embodiment of the present invention, the optical switch 21
A 2 × 1 optical switch was used as 1-214.
The present invention is applicable to a switch having a different size and configuration from one switch. For example, as the optical switch 212, 2
A spare network device can be connected to the input terminal of the optical switch to which the separation input terminal 207 is not connected by applying the × 2 switch. In addition, a distribution selection type 2 × 2 switch is used as the optical switch 213, one of the output terminals of the optical switch is connected to the separation output terminal 202, and the other is connected to the optical signal monitoring device to monitor the optical signal. Obviously, the present invention can be practiced without any problem.

1 × 2 optical switch 21 for switching the transmission side
The distribution-selection type optical switch used as 1 or 212 can be realized by a configuration in which an optical gate switch (a switch that switches between passing and not passing light) is connected to a branch portion of the coupler. In addition, it is also possible to use a configuration in which the optical gate switch is connected to one output terminal of the optical gate switch and the optical gate switch is not connected to the other output terminal. The output of the optical switch to which the optical gate switch is connected may be connected to the spare ring, and the output of the optical switch 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 on / off the signal.
3, 214, it is possible to select the optical signal of either the working ring or the spare ring.

In the case of a system having n spare rings having a shared spare resource for the working signal, in order to enable switching to all the working rings to the working ring, (n +
1) It is necessary to use a × 1 optical switch. It is obvious that the present invention can be applied to a general mxn switch in which a plurality of such switches are integrated.

In the embodiment of the present invention, the optical switches 211 to 214 are used as the switches on the transmission side and the reception side. It is obvious that the present invention can also be implemented by performing protection by an electric switch after converting a signal into an electric signal.

Further, as the electric switch, an electric switch for spatially switching, an electric switch for switching a time-division multiplexed signal obtained by time-division multiplex separation, and a connection established by a cell like an ATM switch. The present invention can be practiced without any problem even with an ATM switch that switches between.

In the embodiment of the present invention, the optical switches 211 to 214 are used as the switches on the transmitting side and the receiving side. It is obvious that the present invention is applicable. On / Off of optical transmitter and optical receiver
Indicates that the injection current of the laser used in the optical transmitter is On.
/ Off can be realized. In addition, since the optical transmitter and the optical receiver can turn on / off the output of the input light, it can be considered as a kind of gate switch. A distribution-selection type optical switch device can be configured by connecting a branching device or an optical multiplexer, and can be used as a part of a switch means for protection.

In the embodiment of the present invention, an optical coupler having a branching ratio of 10:90 is used for monitoring an optical signal. It is self-evident that nothing is done.

In the embodiment of the present invention, the case of a four-node, two-wavelength ring has been described. However, it is obvious that the present invention can be applied to a system having other numbers of nodes and wavelength multiplexing.

In the embodiment of the present invention, a configuration in which all optical signals can be inserted and separated is used. However, it is apparent that the present invention can be applied to a configuration in which not all wavelengths can be inserted and separated.

In the embodiments of the present invention, it is assumed that a wavelength multiplexed system is used. However, it is clear 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 discussed. Clearly, it is possible. 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 the ring topology by the optical fiber group, and a ring formed by the optical fiber group is connected to one. 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 in the same manner as in the first embodiment. If there are two rings in the fiber group, the second embodiment can be used. This is because it 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 a switch used for failure recovery is a 3 × 1 switch, the present invention can be applied to a six-fiber ring. it can. Further, as described in the second and third embodiments, if a part of the band resource can be used as the working resource and the remaining band resource can be used as the spare resource, it is not necessary to use the two-fiber ring. The present invention is applicable to a three-fiber ring and a four-fiber ring.

When a system for transmitting an optical signal bidirectionally in one fiber is used, there is only one ring physically, but it can be logically regarded as two rings around opposite directions. The configuration and method of the present invention can be applied. If 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.

In the embodiment of the present invention, the receiving node switches the ring to be received by using a switch. However, when a failure occurs, the optical signal of the failed one is not input to the receiving node (the source node switches to send a signal to the detour), so the receiving node: Only the optical signal from the non-failed ring is input to the signal termination node. Therefore, there is no need 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 for adding power or a switching type such as the optical switch described in the embodiment of the present invention. is there.

In the embodiment of the present invention, the AWG is used as the wavelength multiplexer and the wavelength demultiplexer. However, an AWG using a diffraction grating, a fiber Bragg grating (a fiber having a periodic structure in a fiber). It is self-evident that the present invention can be implemented without any problem if a device having a function of multiplexing wavelengths or performing wavelength multiplexing / demultiplexing is used, such as a combination of filters configured with filters.

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

In the embodiment of the present invention, an optical communication network in which an optical signal passes through a node on the way without being converted into an electric signal without being converted into an electric signal has been described. It is obvious that the present invention can be carried out without any trouble even if a device for converting the data into the data is inserted.
By installing such a device, the length of the ring can be increased.

In order to convert the wavelength of an optical signal or to reproduce an optical signal having a deteriorated waveform or increased noise, an apparatus for converting an optical signal into an electric signal and then converting the signal into an optical signal again has been proposed. It is obvious that the present invention can be implemented in any part of the present invention.

In the embodiment of the present invention, an optical path without wavelength conversion is used as an optical path. However, a wavelength converter is inserted into a ring network, and an optical path which is wavelength-converted on the way is used as an optical path. Even if handled, the present invention can be implemented without any trouble. As a wavelength converter, a method of once converting an optical signal to 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. By using the wavelength converter, it is possible to reuse the wavelength in the spare ring (reuse the same wavelength in the same ring) by allocating the spare optical path well, so that multiple failures such as double failure can be caused. Resistance is improved.

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

In the embodiment of the present invention, a description has been given of the recovery from a failure in the one-way communication of either the left-handed or right-handed working path. Even so, the present invention can be applied. This is because, in the present invention, each of the shared spare resources is independently assigned, so that a detour can be independently formed.

[0113]

According to the present invention, 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 over which light can be transmitted as it is is determined, it is possible to configure a ring having a longer overall length than a system that performs loopback. Also, unlike the 1 + 1 protection, the spare resources are not used exclusively and the spare resources are shared, so that the number of working optical paths to be operated can be increased. Therefore, it is possible to realize a ring system having a failure recovery function having both features of path accommodation efficiency and a long overall ring length, and to construct a communication network at low cost.

Further, since the switching unit is for each wavelength, it is easy to cope with a failure for each wavelength. In addition, it is possible to set whether or not the protection function is provided for each wavelength.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block 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 illustrating a failure recovery operation used in the first embodiment.

FIG. 7 is a diagram for explaining an 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.

FIG. 12 is a block diagram illustrating a configuration of a communication device according to the present invention.

FIG. 13 is a block diagram showing another embodiment of FIG.

[Explanation of symbols]

 101, 103 working ring 102.104 spare ring 200 clockwise working signal processing unit 211-214 optical switch 215, 216 monitoring controller 217-220 optical splitter 310, 311 optical gate 401 working optical path 402 spare optical path 1021 working light Path 1022 Backup optical path 1121 Working optical path 1122 Backup optical path

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-8-307439 (JP, A) JP-A-10-112700 (JP, A) JP-A-10-164025 (JP, A) JP-A-10- JP-A-9-214538 (JP, A) JP-A-9-55759 (JP, A) JP-A-9-8835 (JP, A) JP-A-7-183906 (JP, A) JP-A-4-150647 (JP, A) JP-A-4-127634 (JP, A) JP-A-4-84536 (JP, A) JP-A-1-236842 (JP, A) (Int.Cl. ⁷ , DB name) H04L 12/42-12/437 H04B 10/00-10/30

Claims (7)

(57) [Claims] 1. A plurality of communication node means for inserting and separating signals and a plurality of transmission paths, wherein the plurality of communication node means form the same network topology by connecting the plurality of transmission paths. At least a first ring, a second ring, a third ring, and a fourth ring, wherein the first ring transmits a working signal clockwise or counterclockwise, and the first ring Of the working signal is shared by the second ring transmitting the signal in the opposite direction to the first ring, and the third ring transmits the working signal in the opposite direction to the first ring. , The spare resource for the working signal of the third ring is the fourth resource for transmitting the signal in the opposite direction to the third ring.
In the communication network shared by the ring, the signal is inserted by the i-th communication node means of the plurality of communication node means, and the signal is inserted by the j-th communication node means via the first ring. Concerning the first communication for terminating a signal, when the j-th communication node detects a failure in the first communication, the communication path of the first communication is changed to the second communication node.
A request message is sent to the i-th communication node means so as to make a detour via the ring of, and when the i-th communication node means receives the request message, the communication path of the first communication By switching from passing through the first ring to passing through the second ring, failure recovery of the first communication is performed, and a signal is inserted in an m-th communication node means of the plurality of communication node means. In connection with the second communication terminating the signal at the nth communication node means via the ring of the third communication, when the nth communication node means detects a failure of the second communication, the second communication node means detects the failure of the second communication. Sending a request message to the mth communication node means so as to bypass the communication path via the fourth ring;
When the m-th communication node receives the request message, it switches the communication path of the second communication from the third ring to the fourth ring, thereby recovering from the failure of the second communication. A communication network characterized by performing. 2. A communication system comprising: a plurality of communication node means for inserting and separating signals; and a plurality of transmission paths, wherein the plurality of communication node means form the same network topology by connecting the plurality of transmission paths. At least a first ring and a second ring are configured so that the first ring transmits a signal clockwise or counterclockwise, and the second ring transmits a signal in a direction opposite to the first ring. In a communication network for transmitting signals, the first ring has in its transmission band a spare resource band shared between working signals transmitted by the second ring, and the second ring has The transmission band has a spare resource band shared among the working signal group transmitted by the first ring, and a signal is inserted by an i-th communication node means of the plurality of communication node means. First ring With respect to the first communication terminating the signal at the j-th communication node means via the first communication node means, when the j-th communication node means detects a failure in the first communication, the communication path of the first communication is changed to the first communication path. A request message is sent to the i-th communication node means so as to bypass the communication path constituted by using the spare resource band of the second ring, and the i-th communication node means receives the request message. And by switching the communication path of the first communication to a communication path configured by the spare resource band of the second ring, performing a failure recovery of the first communication, and Regarding the second communication in which a signal is inserted in the m-th communication node means and the signal is terminated in the n-th communication node means via the second ring, the n-th communication node means uses the second communication Communication When detecting harm, the request message is sent to the m-th communication node means so as to bypass the communication path of the second communication to the communication path constituted by the spare resource band of the first ring, When the mth communication node receives the request message, it switches the communication path of the second communication to a communication path constituted by the spare resource band of the first ring, thereby recovering from the failure of the second communication. A communication network characterized by performing. 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. . 4. The communication network according to claim 3, wherein said optical communication is wavelength multiplexed optical communication. 5. A plurality of communication nodes are connected by a plurality of transmission paths.
Connected to form the same network topology.
At least a first ring, a second ring, and a third ring.
And a fourth ring, and the first ring
Transmits the working signal and pairs with the working signal of the first ring.
The spare resources to be transmitted signal in the opposite direction to the first ring.
The third ring shared by the transmitting second ring;
Ring transmits the working signal in the opposite direction to the first ring.
And the spare resources for the working signal of the third ring are:
The third ring transmitting a signal in a direction opposite to the third ring;
In the communication network shared by the ring of 4
A first communication node, which is transmitted via the first ring,
When the card terminates the inserted first signal,
Is detected, a second resource is sent to the first other node.
Requesting that the first signal be sent via signaling
Outgoing message through the third ring.
When the card terminates the inserted second signal,
Is detected, a fourth resource is sent to the second other node.
Requesting that the second signal be sent via signaling
A message to the third other node via the first ring.
When the third other node is transmitting the signal of No. 3,
Route change request message sent when a failure is detected
When receiving the third signal, the transmission path of the third signal is changed to the first link.
To the second ring via the third ring and to the fourth other node via the third ring.
When transmitting the signal of No. 4, the fourth other node is
Route change request message sent when a failure is detected
When the third signal is received, the transmission path of the fourth signal is changed to the third link.
The feature is to switch from via the ring to via the fourth ring
The communication node to do. 6. A plurality of communication nodes are connected by a plurality of transmission paths.
Connected to form the same network topology.
At least a first ring and a second ring
And, opposite to the previous SL first ring and said second ring
Transmit the signal around the first ring within the transmission band
Shared between the working signals transmitted on the second ring
And the second ring has a transmission bandwidth.
Between the working signals transmitted in the first ring
In communication networks with reserved reserve bandwidth
A communication node , the first other node being sent via the first ring;
When the card terminates the inserted first signal,
Is detected, a second resource is sent to the first other node.
Send the first signal via the reserved resource band of
A second request message transmitted through the second ring.
When the card terminates the inserted second signal,
Is detected, the first resource is sent to the second other node.
The second signal is sent via a spare resource band for
To the third other node via the first ring.
When the third other node is transmitting the signal of No. 3,
Route change request message sent when a failure is detected
When receiving the third signal, the transmission path of the third signal is changed to the first link.
Switch from via the ring to the backup resource band of the second ring
Of the fourth node via the second ring.
When transmitting the signal of No. 4, the fourth other node is
Route change request message sent when a failure is detected
When the second link is received, the transmission path of the fourth signal is changed to the second link.
From the network via the first ring backup resource band
A communication node, characterized in that: 7. A second communication system in which a spare resource constituting a bypass communication path is present in the ring network from an input end of a first communication network node device existing in the ring network shared by a plurality of working signals. When a failure occurs in the communication to the output end of the communication network node device, when the second communication network node device detects the communication failure, a failure recovery request message is sent to the first communication network node. When the first communication network node device receives the failure recovery request message, the switching device of the first communication network node device uses the switch means of the first communication network node device to bypass the communication in the reverse direction. Failure recovery method characterized in that the communication is recovered by switching to a path.
Law .