JPH0964917A - Optical network node equipment and communication method for optical network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize protection of communication on the occurrence of a fault of an equipment or a transmission line by switching quickly a path on the occurrence of the fault in the optical network. SOLUTION: An optical network node 1 is configured by optical switch sections in duplicate, the optical network node 1 being a transmission source branches a transmission signal reaching the optical network into two path in the stage of an electric signal, each signal is converted into an optical signal and input respectively to optical switches 10-0, 10-1. The transmission optical signal is sent to two systems of transmission lines via the optical switches and reaches the destination optical network node. Reception signals from the two systems of the optical paths are outputted to separate branched interfaces 14-0, 14-1 by the optical switches in duplicate in the destination node, converted into electric signals, one of them is selected by a selection section 27 and outputted to the outside of the network. On the occurrence of a fault, a selection section selects the other reception signal to realize the system changeover. Thus, the path is switched quickly in the optical network to improve the reliability in the optical network.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a node device and a communication method in an optical network, and more specifically, it is composed of optical parts such as an optical switch and an optical amplifier, and exchanges transmission signals in an optical signal state. The present invention relates to an optical network node device to perform, and a communication method in a network composed of these optical network node devices, particularly to a communication path protection and switching method.

[0002]

2. Description of the Related Art At present, research and development of an optical communication network (optical network) in which an optical switch is applied to a node in the network so as to transfer and process signals at an optical level is being made. As one of the recovery methods when a failure occurs in such an optical network, in IEICE Transactions, BI Vol. J77-BI, No. 5, pp. 285-293,
"Optical digital cross-connect system using matrix optical switch and optical amplifier" is introduced.

FIG. 2 schematically shows a failure recovery method according to the above-mentioned document, in which a node 1 (1
-1 to 1-4: hereinafter referred to as "optical network node") are configured with optical components such as an optical switch. Here, in the case of transmitting an optical signal from the optical network node 1-1 to the optical network node 1-4, there are two systems of optical paths, the optical path 4-0 indicated by the solid arrow and the optical path 4-1 indicated by the broken arrow. The signal path is set. Of these two optical paths, the signal is normally transmitted through one path that is the "working path", and the signal is not transmitted through the other path that is the "standby path". When a failure occurs in the working path, the setting of the optical switch in the optical network node is changed, and a signal is transmitted using the protection path to recover from the failure. Here, the working path is "optical network node 1-1"-
"Optical network node 1-2"-"Optical network node 1-4" is set, and the backup route is "optical network node 1-1"-"optical network node 1-3"-"optical network node 1-4". Is set to. In this specification, a management unit of a communication path from when a transmission signal is input to the optical network to when it is output to the outside is defined as an "optical path". In this example, the optical network node 1-1 to the optical network is used. Node 1-
That is, the optical path 4-0 is set to the optical path No. 4.

According to the conventional failure recovery method using an optical switch, for example, when a failure occurs in the optical path 4-0, this failure is detected by the optical network node 1-4, and the optical network node 1- 4 notifies the control station 2 that a failure has been detected and the identifier of the optical path in which the failure has occurred. The control station 2 holds backup path information of each optical path set in the optical network. The control station 2 is the optical network node 1
-4, the optical network node 1--1
1. Instruct the optical network node 1-3 and the optical network node 1-4 to switch the route of the optical path 4-0 from the working route to the protection route. In response to the above instruction, the optical network node 1-1
Controls the optical switch 10 so as to switch the route of the optical path 4-0 from the working route to the backup route shown by the broken line, and the optical network node 1-3 receives the optical signal arriving from the optical network node 1-1. The optical switch 10 is controlled to output to the optical network node 1-4, and the optical network node 1-4 switches the optical switch 10 to receive the signal from the protection path of the optical path 4-0. This operation completes the switching. Here, in order to distinguish from the optical path 4-0 of the working path, the optical path that passes through the backup path is called the optical path 4-1.

FIG. 3 shows the configuration of the optical network node 1.
The optical network node 1 includes a plurality of reception interface units 11 (1
1-1 to 11-N), the optical switch 10, the plurality of transmission interface units 13 (13-1 to 13-N), the insertion interface unit 12, and the branch interface unit 14
And the control unit 15. The optical switch 10 is (N +
1) It has an input and (N + 1) output, and has a line setting function for connecting an optical signal arriving at each input highway to an arbitrary output highway. The optical signal arriving at each input port of the optical switch 10 by the line setting function is transmitted by the transmission interface unit 13 or the branch interface unit 14.
Be assigned to.

As shown in FIG. 4A, the reception interface section 11 includes an optical amplifier 16 which amplifies a received optical signal as an optical signal. The optical amplifier 16 is for compensating for the loss of the received optical signal in the transmission line, and as a means for amplifying the optical signal as it is, for example, a semiconductor amplifier or an optical fiber amplifier is known. .

As shown in FIG. 4B, the transmission interface section 13 receives the optical signal output from the optical switch 10, amplifies it, and outputs it to the transmission line 3.
It has. The optical amplifier 16 is provided to compensate the loss in the optical switch 10 and also the loss in the output transmission line.

As shown in FIG. 4C, the insertion interface section 12 has an overhead insertion circuit 17 for writing control information in an overhead portion of an electric signal to be inputted to the optical network, and an output of the overhead insertion circuit. E / O that converts an electrical signal into an optical signal and outputs it to the optical switch 10.
And a conversion circuit 18.

As shown in FIG. 4D, the branch interface section 14 includes an O / E conversion circuit 19 for converting an optical signal received from the optical switch 10 into an electric signal,
A frame synchronization circuit 22 for frame-synchronizing the output electric signal of the O / E conversion circuit; an overhead processing circuit 20 for analyzing a control signal included in an overhead portion of the electric signal output from the frame synchronization circuit; The monitor control circuit 21 is connected to each of the circuits 19 to 22 and monitors the normality of electric signals. The monitor control circuit 21 has a communication function with the control unit 15 of the optical switch.

The control unit 15 has a function of notifying the network control station 2 of the state of the optical network node 1 and, in response to a command from the control station 2, for example, setting of the optical switch 10 or the like of the optical network node. It has a function of controlling each unit.

An electrical signal input to the optical network from the outside is converted into an optical signal in the inserting interface unit 12 of the optical network node 1, and then passes through the optical switch 10 and the transmitting interface unit 13 and is output to the transmission line 3. And arrives at the destination optical network node via the optical network node on the optical path. The optical signal arriving at the destination optical network node is received by the reception interface unit 1
1. Branch interface unit 1 passing through optical switch 10
4 and is converted into an electric signal in the branch interface unit 14 and then output to the outside of the optical network.
A terminal device or a node (a node that performs electrical processing or the like) belonging to another network is connected to the outside of the optical network node, that is, to the end of the insertion interface unit and the branch interface unit.

[0012]

According to the above-mentioned conventional failure recovery system in the optical network, since two optical signal paths are prepared in the optical network, it is possible to endure a single transmission path failure. Although there is power, it takes time until a new route is set by the control station 2 when a failure occurs, and communication between optical network nodes is stopped until the optical path is restored, so network operation There is a problem that the rate decreases. In order to eliminate the need to newly set a route when a failure occurs, for example, it is sufficient to always set two optical paths and select one of the optical signals. However, this method In order to realize the above, it is necessary to output an optical signal to two paths in the optical switch 10 of the transmission source node of the optical path, and an optical signal branch output means is required. In this case, the following new problems occur. (1) When the input optical signal is split into two output paths and output, the power of the output optical signal is half that of the input optical signal. Therefore, a new optical amplifier is provided to increase the output optical signal power. Need to compensate. Therefore, the device cost increases by the amount of the optical amplifier. (2) When the power of the output optical signal is compensated by the optical amplifier, noise is added to the amplified optical signal, and there is a problem that the transmission distance of the optical signal becomes shorter as the noise increases.
Therefore, the number of optical network nodes required for the same transmission distance increases, and the transmission cost increases. In addition to the above-mentioned problems, the conventional method has a problem that recovery cannot be performed when a failure (switch failure) occurs in the optical switch 10 in the source optical network node.

An object of the present invention is to provide a node device capable of coping with both a switch failure and a transmission path failure in an optical network, and a communication method suitable for an optical network capable of promptly recovering the communication state against these failures. To do. Another object of the present invention is to reduce the transmission distance of an optical signal,
It is an object of the present invention to provide a node device and a communication method capable of coping with a switch failure and a transmission path failure of an optical network at a relatively low cost.

[0014]

In order to achieve the above object, a node device of the present invention comprises a plurality of input ports and output ports, respectively, and an optical signal input from any one of the input ports is input. A plurality of optical switch means for outputting to an output port of each of the optical switch means, and at least one set of optical switch means, each of which is connected to one of the input ports of the optical switch means, converts an electrical input signal into an optical signal and supplies the optical signal to the input port. The insertion interface, at least one pair of branch interfaces each connected to one of the output ports of each of the optical switch means and converting an optical output signal from the output port into an electrical signal and outputting the electrical signal, and each of the optical switches. Connected between the input port of the means and the optical transmission line, or between the output port of the optical switch means and the optical transmission line,
A plurality of receiving interfaces and transmitting interfaces for amplifying the input optical signals and outputting them to the above-mentioned input port or optical transmission line, and an electrical transmitting signal input from the inserting signal line to a plurality of inserting interfaces forming a set. From a transmission signal distribution means for distributing and a reception path selection means for receiving an electric signal output from a set of a plurality of branch interfaces and selectively outputting any one of them to a branch signal line. It is characterized by

In the modified example of the node device, each of the optical switch means performs an exchange operation for an optical signal having a unique wavelength, and each insertion interface provides an electrical input signal unique to each of the optical switch means. The signal is converted into an optical signal having a wavelength and supplied to the input port, and each reception interface outputs a wavelength unique to each optical switch distributed from the demultiplexer provided for each optical transmission line for reception. The input optical signal is amplified and output to the input port of the switch means, and by the multiplexer provided for each optical transmission line for transmission, the difference output from the corresponding transmission interfaces of the plurality of switch means is provided. The optical signals of the wavelengths are combined and sent to the optical transmission line.

Another feature of the present invention is that the node device comprises
Fault detection means for monitoring the signal received from the reception interface and detecting the occurrence of a fault, and control for instructing the reception path selection means to switch the selective input according to the fault detection result by the fault detection means And means. The fault detecting means is provided, for example, for each branch interface, and the control means switches the path to the control station of the optical network or another optical network node device according to the fault detection result by the fault detecting means. To send the control signal for.

According to another modification of the node device of the present invention, instead of the transmission signal distribution means, the electrical transmission signal input from the insertion signal line is included in one set of a plurality of insertion interfaces. The transmission path selection means for selectively supplying any of the above is applied. In this case, the control means, depending on the failure detection result by the failure detection means,
The reception path selection means is instructed to switch the output signal, and a control signal for path switching is sent to the control station of the optical network or another optical network node device, and at the same time, the control station or another optical network node. When a control signal for path switching is received from the device, the transmission path switching means is instructed to switch the insertion interface to which the transmission signal is supplied, according to the control signal.

According to the communication method of the present invention, in an optical network including a plurality of node devices, two node devices, which are end points of an optical path, insert a plurality of electrical transmission signals input from respective insertion signal lines. After being distributed to the interface and converted into optical signals, the optical signals are sent from the optical switching means of the own node device to the optical transmission lines, so that the transmission signal can be transmitted in parallel to the partner node device via multiple paths. While transmitting, one of the transmission signals from the other node device received from different optical transmission paths is selectively taken in by the reception path selection means and output to the branch signal line, and the failure detection means selects one of the selected signals. When an abnormality of the received signal is detected, the received signal to be output to the branch signal line is switched to another signal from another optical transmission line by the receiving path selection means.

In this case, one node device that has detected an abnormality in the received signal notifies the other node device or the control station of a control signal indicating an abnormality in the reception path, and the other node device transmits the control signal to the control signal. In response to this, the receiving path selecting means is operated to switch the output to the branch signal line to the receiving signal from another optical transmission line, thereby enabling bidirectional path switching. In addition, in an optical network in which each node device includes a transmission path switching unit, the node device that detects an abnormality in a received signal communicates with the other node device that is a communication partner or a control station connected to each node device. Bidirectional path switching is possible by notifying a path abnormality and switching the transmission path by the other node device in response to the notification from the node device that detected the abnormality or the control station. Become.

[0020]

According to the node device of the present invention, each node device is provided with a plurality of optical switches, distributes an electric signal input to the optical network to a plurality of insertion interfaces, converts the electric signal into a plurality of optical signals, and The optical switches are output in parallel to different transmission lines. For network level control, a route is set so that these optical signals pass through different optical network nodes (optical switches). Each node device guides an optical signal received from a node device of a communication partner via a different transmission path to a branch interface via a separate optical switch, converts the signal into an electrical signal, and selectively branches one of them. Output to the signal line. in this case,
Since each of the optical signals passes through different optical switches in both the start point and the end point of the node device, it is possible to provide a protection method capable of coping with both transmission line failure and device (optical switch) failure. Further, since the transmission signal is branched at the electric signal level, the optical signal is not required to be branched and the configuration of the node device is simplified.

On the other hand, according to the modification of the present invention, each node device selectively transmits the electric level transmission signal to be transmitted to the optical network to any one of the plurality of optical switches by the transmission path selecting means. By supplying the optical path to the optical path, one optical path is set between the two node devices at the start point and the end point, and when a failure is detected in the optical path, the transmission path selection means switches the optical switch. By doing so, an optical path of another route is set. The newly set optical path passes through an optical switch that is different from the optical switch through which the optical signal passed before the occurrence of the failure in both the start point and end point node devices, and is different from the previous transmission path. Via a transmission line. Therefore, also in this case, it is possible to protect against both transmission line failure and optical switch failure.

[0022]

FIG. 6 shows the configuration of an optical network according to the first embodiment of the present invention. Here, a portion including four optical network nodes 1 (1-1 to 1-4) forming an optical network and a control station 2 connected to these optical network nodes 1 is shown. The control station 2 manages and controls optical network nodes such as setting paths in the optical network and collecting failure information. Each optical network node 1
Is an optical transmission line 3 for transmitting an optical signal, which is provided between the optical network node and another optical network node, an input highway 8 for transmitting an electric level signal entering the optical network from the outside of the optical network, and an optical network. Is connected to an output highway 9 for transmitting a signal of an electric level output from the outside. The electrical signal input from the input highway to the optical network is converted to an optical signal at the optical network node at the entrance of the optical network, and then output to the desired optical transmission line, and the desired optical signal is output to the relay optical network node located on the optical path. Of the optical network, the optical network node at the exit of the optical network reconverts it into an electric signal, and outputs it to the highway outside the optical network.

The configuration of the optical network node 1 is shown in FIG. The feature of the present invention is to duplicate the optical switch unit shown in FIG.
The input signal from the outside of the optical network should be distributed to the two optical switches at the electric signal level and output to the outside of the optical network.
The point is that after converting the output signals from the two optical switches into electric signals, one of them is selected. The optical network node 1 includes a duplicated optical switch 10 (10-0, 1
0-1) and a plurality of reception interface units 11 (11-1-0-1) provided in each of the optical switches.
1-N-0, 11-1-1 to 11-N-1) and the transmission interface unit 13 (13-1-0 to 13-N-0,
13-1-1 to 13-N-1) and the insertion interface unit 12 (1) provided in pairs for each optical switch.
2-0, 12-1) and the branch interface unit 14
(14-0, 14-1), a selection unit 27 for selectively taking out one of the electrical signals output from the two branch interface units, and the insertion interface, the branch interface and the selection unit. And a control unit 15 for The reception interface unit 1
1, the configuration of the optical switch 10, the transmission interface unit 13, the insertion interface unit 12, and the branch interface unit 14 may be the same as the conventional configuration shown in FIG.

As shown in FIG. 5, the selection unit 27 includes a selector 25 for selecting one of the two systems of electrical signals output from the two branch interface units 14-0 and 14-1; It comprises a selector control circuit 26 for giving a selection signal to the selector 25, and the selector control circuit is
It operates in response to a control signal from the control unit 15. The control unit 15 has a function of notifying the control station 2 of the state of the optical network node 1, and according to a command from the control station 2, the optical switch 10
Control each element of the optical network node, such as setting of.

In the embodiment shown in FIG. 6, the optical network node 1-
1 and the node 1-4, two-way communication optical paths 4-0-i, 4- are provided for protection operation.
1-i (i = 0 to 1) is set. Optical path 4-0
-0 and 4-1-0 are used for transmission of a signal from the optical network node 1-1 to the optical network node 1-4, and the optical path 4-0-
1 and 4-1-1 are optical network nodes 1-4 to optical network nodes 1-
It is used to transmit a signal going to 1. The same optical signal is transmitted to the duplicated optical paths 4-0 and 4-1.
The transmission signal on −0-0 passes through the order of “optical network node 1-1”-“optical network node 1-2”-“optical network node 1-4”, and then on the optical path 4-1-0. The transmission signal is “optical network node 1
-1 "-" optical network node 1-3 "-" optical network node 1-4 "
Pass in order. Similarly, the transmission signal on the optical path 4-0-1 is "optical network node 1-4"-"optical network node 1-2"-.
The optical path 4-1-1 is passed through in the order of "optical network node 1-1".
The above transmission signal passes through "optical network node 1-4"-"optical network node 1-3"-"optical network node 1-1" in this order.

Optical network nodes 1-1 located at both ends of the optical path
And 1-4 implement the protection operation by selecting the reception signal from the normal optical path among the duplicated optical paths 4-0 and 4-1. For example, an electric signal input from the input highway 8 to the optical network node 1-1 is branched into two routes at the branch point 6 shown in FIG. 1, and the insertion interface units 12-0 and 1-2 of the duplexed optical switch unit are provided.
In 2-1 each is converted into an optical signal. Branch point 6 above
May be composed of, for example, a 1-input 2-output electric switch. The branched optical signal is transmitted to the two optical switches 10-
0, 10-1, transmission lines 3-1-0, 3
-2-0 any of the transmission interface units 13 corresponding to
-1-0 to 13-N-0, 13-1-1 to 13-N-1
And is output to the transmission line. Transmission line 3-1-0,
The optical signals output to 3-2-0 are respectively sent to the optical path 4-
Optical network nodes 1-2, 1-3 along 0-0, 4-1-0
To reach the destination optical network node 1-4. In the destination optical network node 1-4, the optical signal is transmitted through the transmission path 3-3-0,
3-4-0 and corresponding reception interface unit 11-1-
0-11-N-0 or 11-1-1 to 11-N-1 is input to the optical switch 10-0 or 10-1,
The branch interface units 14-0 and 14-1 arrive.
The respective optical signals are sent to the branch interface units 14-0, 14
At -1, the electric signal is converted into an electric signal, and the electric signal selected by the selection unit 27 is output to the highway 9. In addition, outside the optical network node, that is, at the ends of the insertion interface unit and the branch interface unit, a terminal device or a node belonging to another network (such as a node that performs electrical processing) is connected via the highways 8 and 9. It

FIG. 7 shows setting of the optical path 4 in the optical network node 1-1. The electric signal input from the highway 8 is branched into two routes at the branch point 6 before being converted into the optical signal at the optical network node 1-1, and the optical signals are branched at the insertion interface units 12-0 and 12-1. After being converted into the optical switches, the signals are input to the optical switches 10-0 and 10-1, respectively. Light path 4
The transmission signal to −0-0 is connected to the output port toward the optical network node 1-2 by the line setting function of the optical switch 10-0, and passes through the transmission interface unit 13-1-0 to the transmission line 3 It is output to 1-1. Similarly, optical path 4-
The transmission signal to 1-0 is connected to the output port toward the optical network node 1-3, and the transmission interface unit 13-N-1
Is output to the transmission line 3-2-0. On the contrary, the optical signals of the optical paths 4-0-1 and 4-1-1 transmitted toward the optical network node 1-1 from the optical network node 1-4 as a starting point are respectively transmitted to the optical network node 1 -2, 1-3 to arrive at the optical network node 1-1. The reception signal from the optical path 4-0-1 is input to the branch interface unit 14-0 via the reception interface unit 11-1-0 and the optical switch 10-0, and after being converted into an electric signal here. , Arrives at the selection unit 27. Similarly, the reception signal from the optical path 4-1-1 also receives the reception interface unit 11-N-1 and the optical switch 1.
The signal is input to the branch interface unit 14-1 via 0-1, converted into an electric signal, and then arrives at the selection unit 27. The selection unit 27 selects one of these two electric signals and outputs it to the reception highway 9.

FIG. 8 shows the setting of the optical path 4-0 in the optical network node 1-2. Optical network node 1-1 to optical path 4-
The signal transmitted to 0-0 is the reception interface unit 11
It is output to the transmission path 3-3-0 toward the optical network node 1-4 via the -1-0, the optical switch 10-0, and the transmission interface unit 13-1-0. On the other hand, the signal transmitted from the optical network node 1-4 to the optical path 4-0-1 passes through the reception interface unit 11-N-0, the optical switch 10-0, and the transmission interface unit 13-N-0, Optical network node 1-1
It is output to the transmission path 3-1-1 heading for. Optical network node 1
-3, the same operation as the signal relay in the optical network node 1-2 described above is performed on the received signals on the optical paths 4-1-0 and 4-1-1.

FIG. 9 shows the setting of the optical path 4 in the optical network nodes 1-4. Similar to the operation in the optical network node 1-1, the input signal from the highway 8 is branched into two routes in the branch 6 before being converted into an optical signal in the optical network node 1-4, and the insertion interface unit 12-
After being converted into optical signals at 0 and 12-1, they are input to the optical switches 10-0 and 10-1, respectively. Here, by the line setting function of the optical switch 10, the transmission signal to the optical path 4-0-1 is transmitted from the output port toward the optical network node 1-2 through the transmission interface unit 13-1-0 to the transmission line 3 −
It is output to 3-1. Further, the transmission signal to the optical path 4-1-1 passes through the transmission interface unit 13-N-1 from the output port toward the optical network node 1-3, and then the transmission line 3-4.
-1 is output.

Optical path 4-starting from optical network node 1-1
The signals transmitted to 0-0 and 4-1-0 are transmitted to the optical network node 1 via the optical network node 1-2 and the optical network node 1-3, respectively.
-4 arrives. The received signal from the optical path 4-0-0 is
From the reception interface unit 11-1-0 to the optical switch 10
It is input to the branch interface unit 14-0 via −0, converted into an electric signal, and then arrives at the selection unit 27.
The reception signal from the optical path 4-1-0 is also input from the reception interface unit 11-N-1 to the branch interface unit 14-1 via the optical switch 10-1, converted into an electric signal, and then selected by the selection unit. Arriving at 27. The selection unit 27 selects one of the reception signals (electrical signals) from these two optical paths 4-0-0 and 4-1-0 and outputs it to the highway 9.

FIG. 10 shows the paths of the optical paths when attention is paid to each optical switch in this embodiment. As shown in FIG. 10, the optical path 4-0 and the optical path 4-1 pass through completely different transmission paths and optical switches, so that a failure occurs in the optical switch or the transmission path through which one optical path passes. Even in the above, it is clear that communication can be continued by the other optical path.

Next, the path switching procedure in this embodiment will be described. Here, the switching operation in the case of the one-way switching method will be described. Of the duplicated optical paths,
The system passing through the "optical network node 1-1"-"optical network node 1-2"-"optical network node 1-4" is the 0 system, and the "optical network node 1"
-1 "-" optical network node 1-3 "-" optical network node 1-4 "
Assuming that the one passing through is 1 system, in the one-way switching system,
Optical network nodes 1-1 and 1 that are the start point or end point of the path
-4 independently operates one of the duplicated optical paths. That is, the optical network nodes 1-1 and 1-4
Does not always select the optical path 4 of the same system.

First, as an initial setting, the optical network node 1-
The selection units 27 of 1 and 1-4 respectively set the optical path 4 of the 0 system.
-0 (4-0-0, 4-0-1) is selected, the transmission line 3-3-0 (see FIG. 6) on the optical path 4-0-1 is disconnected. Assume that a failure has occurred. In this case, when the transmission line 3-3-0 is disconnected, the supervisory control circuit 21 in the branch interface unit 14-0 of the optical network node 1-4 detects a transmission line abnormality, and the control unit 1 detects this.
Notify 5 The failure of the transmission path is detected by, for example, the optical path 4
An error detection code is added to the overhead portion of the above transmission signal, and the supervisory control circuit 21 in the branch interface unit 14 of each optical network node is provided with an error detection code operation function.
You may make it detect the deterioration of the signal error rate on a transmission line.

When the controller 15 of the optical network node 1-4 is notified by the supervisory control circuit 21 of a signal abnormality on the optical path 4-0-0, the selector control circuit 26 of the selector 27 selects the current selection. Command to switch the inside optical path to the backup optical path. When the selection unit 27 switches the input in response to the command, the received signal from the optical path 4-0-1 of the standby system is output to the highway 9 and the failure can be quickly recovered.

In the above embodiment, different transmission lines are connected to the respective inputs and outputs of the two optical switches 10-0 and 10-1 of the optical network node 1, but the wavelength of the optical signal handled by the optical switch 10-0 is By setting the wavelengths of the optical signals handled by the optical switch 10-1 to different values (λ1 and λ2), wavelength-multiplexing the signals output to the same optical network node among the output signals from each optical switch. The number of transmission lines may be reduced. When the optical signals are wavelength-multiplexed in this way, the receiving side node separates the optical signals received from the same transmission path by wavelength and inputs them to each optical switch.

FIG. 11 shows an embodiment of the optical network node 1 adopting the wavelength division multiplexing method. In FIG. 11, the duplexer 28
-I (i = 1 to N) outputs the signal of wavelength λ1 among the optical signals received from the transmission line to the reception interface 11-i-0 on the optical switch 10-0 side and outputs the signal of wavelength λ2 as optical signals. Reception interface 11-i on the switch 10-1 side
Output to -1. Also, the multiplexer 29-i (i = 1 to N)
Is the transmission interface 13 on the optical switch 10-0 side.
The wavelength λ1 optical signal output from -i-0 and the wavelength λ2 optical signal output from the transmission interface 13-i-1 on the optical switch 10-1 side are wavelength-multiplexed. The insertion interface units 12-0 and 12-1 have E / O conversion circuits having different output light wavelengths (λ1 and λ2), and similarly, the branch interface units 14-0 and 14-1 also have processing signal wavelengths. Different (λ1 and λ2) O / E conversion circuits.

In the above embodiment, the configuration and the operation when the optical paths are duplicated have been described. However, each optical network node is provided with M optical switches, and at the start node, input electric signals are input to M optical switches. The signal is branched to the optical switch, and the signal converted into light is transmitted to the end point node via M (M is a natural number of 3 or more) transmission lines, and the end point node selects one of them. Good.

Next, an example in which the optical network nodes 1-1 and 1-4, which are the start point and the end point of the optical path, perform bidirectional switching in the network configuration of FIG. 6 provided with the duplexed bidirectional communication path Will be described. Of the duplicated optical paths, "optical network node 1-1"-"optical network node 1-"
2 ”-“ optical network node 1-4 ”through 0 system,
Assuming that a system passing through "optical network node 1-1"-"optical network node 1-3"-"optical network node 1-4" is one system, in bidirectional switching, the optical network nodes 1-1, 1 When one of -4 selects the 0-system (or 1-system), the other controls the same 0-system (or 1-system).

The configuration of each optical network node 1 is the same as that of the first embodiment, and the optical network nodes 1-1 and 1-4 have the following initial conditions.
In a state where the optical path 4-0 (4-0-0, 4-0-1) which is the 0-system is selected, the transmission path 3-3-0 forming a part of the optical path 4-0-0 is selected. Assume that a failure has occurred (see FIG. 10). The above-mentioned failure is detected by the supervisory control circuit 21 in the branch interface unit 14-0 of the optical network node 1-4 on the receiving side, and the optical network node is instructed by the control unit 15 notified from the supervisory control circuit 21. Selector 2 of 1-4
7 replaces the 0-system optical path 4-0-0 with the 1-system optical path 4
Operates to select the received signal from -1-0. At this time, the control unit 15 notifies the control station 2 of a failure notification message including the number of the optical path in which the failure has occurred and its own optical network node number through the control line 5-4 shown in FIG. To do. When the control station 2 receives the failure notification message, it starts the optical path node 1-1 of the optical path 4-0-0 in which the failure has occurred and the optical path 4-based on the management information held in advance. Optical path 4 used for 0-0 reverse transmission
The numbers 0-4-1 and 4-1-1 are indexed, and 4-1-1 is used instead of the optical path 4-0-1 for the start point optical network node 1-1.
Instruct the user to select As a result, the start point optical network node selects the optical path 4-1-1, and the up and down bidirectional paths are switched from 0 system to 1 system. In bidirectional switching, the receiving interface and the transmitting interface are configured on the same base. This is effective when, for example, a failure occurs only in the transmission interface in the established node device. In this case, not only the transmission interface but also the reception interface must be switched to the spare for the base switching, and bidirectional switching is effective in which the optical network nodes select the signals of the same optical path at both ends of the optical path. Becomes

In the above operation example, the switching command is given to the start point optical network node via the control station 2. However, the end optical network node 1-4 which has detected the failure is to the start point optical network node 1-1, The switching control message may be directly transmitted. As the switching control message, for example, ITU-T Recommendation G. The case of using a transmission frame called STM-1 defined in 707, 708, and 709 will be described below.

FIG. 12 shows the frame structure of STM-1. As shown in FIG. 12, the STM-1 frame is composed of 9 rows × 270 bytes, and is 155.52 sequentially from the first row.
It is transmitted at a transmission rate of Mb / s. In the overhead portion provided in the first 9 bytes of each row of the STM-1 frame, bytes K1 and K2 for transmitting a switching control message are defined in addition to the bytes A1 and A2 for frame synchronization. In the present invention, bidirectional switching can be realized by using these K1 and K2 bytes. Normally, the two bytes of K1 and K2 are set to a pattern of "00000000 00010000", and when a certain optical network node detects a failure, the K1 is transmitted to the opposite end node on the optical path. , K2, a frame in which a special pattern such as “11000001 00010000” is set is transmitted, and the opposite node side switches the path when a pattern change is detected in the K1 and K2 bytes of the received frame.

For example, in the network of FIG. 10, the optical path 4
When a failure occurs in -0-0, this failure is detected by the supervisory control circuit 21 of the branch interface unit 14-0 of the optical network node 1-4, and the control unit 15 is notified of the failure detection. In the optical network node 1-4, the selection unit 27 executes path switching according to a command from the control unit 15. At this time, the control unit 15 instructs the overhead insertion circuit 17 of the insertion interface unit 12 to change the pattern of K1 and K2 bytes, and the overhead insertion circuit 17 changes the K1 and K2 bytes.
The pattern 2 is changed to the special pattern for switching instruction.

The frame including the special pattern for switching is transmitted to the start point optical network node 1-1 via the optical path 4-1-1, and the branch interface unit 1 of the optical network node 1-1.
The overhead processing circuit 20 of 4-1 detects the change in the pattern of the K1 and K2 bytes and notifies the control unit 15 of the change. The control unit 15 includes the selector control circuit 26 of the switching unit 27.
On the other hand, an instruction is issued to select the received signal from the optical path 4-1-1 instead of the optical path 4-0-1. Selector control circuit 2
6 operates the selector 25 in response to the above command to replace the input signal from the highway 7-0 with the highway 7-1.
Select the signal of.

FIG. 13 shows a second embodiment of the optical network node 1. The optical network node 1 shown in FIG. 13 uses electric switches 30 and 31 instead of the selection unit 27 used in the first embodiment, and has a reception interface unit 11 and two optical switches 10-0 and 10-. 1 and the transmission interface unit 13
, Insertion interface unit 12, branch interface unit 14, and electric switches 30 and 3 for processing electric signals.
1 and a control unit 15 that receives a command from the control station 2 and controls the optical network node. The control unit 15 has a function of notifying the control station 2 of the state of the optical network node 1.

In this embodiment, a bidirectional optical path is set between two optical network nodes, which are the start point and the end point, and when a failure occurs in this optical path, a new optical path is added between the nodes. Is different from the first embodiment. For example, FIG.
In the present embodiment, the optical network shown in FIG.
Optical path 4-0 (4-0-0, 4-0 between 1 and 1-4)
-1) is set. Optical path 4-1 (4-1
-0, 4-1-1) is a spare path that has not been set as long as the optical path 4-1 is normal, and at the time when a failure occurs in the optical path 4-0, the new optical path 4-1 Is set.

The setting operation of the optical path 4-0 in the optical network node will be described with reference to FIG. The transmission signal from the highway 8 is input to the electric switch 30 in the state of an electric signal. The electrical switch 30 sends the input signal from the highway to the optical network node 1-2 to switch the switch 10 to the optical network node 1-2.
Output to the insertion interface unit 12-0 of -0. The transmission signal converted into the optical signal by the insertion interface unit 12-0 is output to the output port toward the optical network node 1-2 by the optical switch 10-0, and the transmission interface unit 1
It is output to the transmission line 3 via 3-1-0. on the other hand,
The signal on the optical path 4-0-1 transmitted from the optical network node 1-4 is received by the reception interface unit 11-1-0 connected to the optical network node 1-2, and is transmitted to the optical switch 10-0. It is input to the branch interface unit 14-0 via the route.
The received signal is converted into an electric signal in the branch interface unit 14-0, and then, via the electric switch 31,
Output to highway 9.

In the optical network node 1-2, the signal on the optical path 4-0-0 is transmitted from the receiving interface section 11-1-0 to the optical switch 10- by the same operation as described in FIG.
0, the transmission interface unit 13-1-0, and the optical path 4 are output to the transmission line 3 toward the optical network node 1-4.
The signal on -0-1 is the reception interface unit 11-N-
0 to the optical switch 10-0, the transmission interface unit 13
It is output to the transmission line 3 heading for the optical network node 1-1 via -N-0. The operation of the optical network node 1-4 is similar to that of the optical network node 1-1, and the optical path 4-0-0 in FIG.
To 4-0-1 and the optical path 4-0-1 to 4-0-0.
It becomes equivalent to the one replaced with.

In this embodiment, for example, when the transmission line 3-3-0 in FIG. 6 is disconnected, the optical path 4-0-0
Optical network node 1-
Supervisory control circuit 21 of the branch interface unit 14-0 of No. 4
Detects and notifies the control unit 15. The control unit 15 notifies the control station 2 of the optical path number in which the failure has occurred and its own optical network node number. Upon receiving the above notification, the control station 2 sends the optical path 4-0 to the optical network nodes 1-1, 1-3, and 1-4 via the optical network node 1-3 and the protection path 4-1.
And the setting of the optical path 4-1 to the optical network node 1-3.

Upon receiving the path change command from the control station 2, the control unit 15 of the optical network node 1-1 outputs the transmission signal from the highway 8 to the insertion interface unit 12-1 to the electric switch 30. Command. As a result, the transmission signal is converted into an optical signal by the insertion interface unit 12-1, and then the transmission interface unit 13 is controlled by the optical switch 10-1 whose setting is controlled by the control unit 15.
-N-1 and then to 3-2-0 on the transmission path toward the optical network node 1-3. The optical signal received by the reception interface unit 11-N-1 connected to the optical network node 1-3 is output to the branch interface unit 14-1 by the optical switch 10-1, and the branch interface unit 14- After being converted into an electric signal by 1, the electric signal is input to the electric switch 31. The control unit 15 uses the electric switch 3
1 is instructed to output the output of the branch interface unit 14-1 to the highway 9. As a result, the received signal from the optical path 4-1-1 is output to the highway 9 instead of the signal from the optical path 4-0-1.

Upon receiving the path setting command from the control station 2, the control unit 15 of the optical network node 1-3 receives the optical switch 10-.
1, the received optical signal of the reception interface unit 11-1-1 connected to the optical network node 1-1 is sent to the optical network node 1-
4 to the transmission interface unit 13-1-1 connected to the optical network node 1-4, and the optical signal received by the reception interface unit 11-N-1 connected to the optical network node 1-4 from the optical network node 1
The setting is changed so that it is output to the transmission interface unit 13-N-1 connected to -1. As a result, the optical path 4-1 from the optical network node 1-4 to the optical network node 1-1.
1 and an optical path 4-1-0 from the optical network node 1-1 to the optical network node 1-4 is formed.

Upon receiving the path change command from the control station 2, the control unit 15 of the optical network node 1-4 receives the electric switch 30.
To the insertion interface unit 12-0, the optical switch 10-is instructed to output the transmission signal on the optical path 4 which has been output to the insertion interface unit 12-0.
1, the reception signal of the reception interface unit 11-N-1 connected to the optical network node 1-3 is branched to the interface unit 1
The setting is changed so that it is output to 4-1 and the electric switch 31 is instructed to output the output of the branch interface unit 14-1 to the branch line 9.

As a result, the transmission signal to the optical path 4 is
After being converted into an optical signal by the insertion interface unit 12-1, the optical switch 10-1 and the transmission interface unit 13-
Transmission line 3-4-1 (optical path 4-1) via N-1.
1), the received signal from the optical network node 1-3 is
Reception interface unit 11-N-1, switch 10-1
After being converted to an electric signal by the branch interface unit 14-1 via
Is output to

FIG. 14 shows the structure of an optical network node when the wavelength division multiplexing similar to that of FIG. 11 is applied to the node configuration of FIG.

[0054]

As is apparent from the above description, according to the present invention, it is possible to quickly switch paths when an abnormality occurs, and improve the reliability of the optical network.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical network node according to the present invention.

FIG. 2 is a diagram showing a configuration of a conventional optical network.

FIG. 3 is a diagram showing a configuration of a conventional optical network node.

FIG. 4 is a diagram showing a detailed configuration of main elements of an optical network node.

FIG. 5 is a diagram showing a configuration of a selection unit 27.

FIG. 6 is a configuration diagram of an optical network for explaining a first embodiment of path switching according to the present invention.

FIG. 7 is a diagram for explaining path setting in the optical network node 1-1 of FIG.

8 is a diagram for explaining path setting in the optical network node 1-2 of FIG.

9 is a diagram for explaining path setting in the optical network nodes 1-4 of FIG.

FIG. 10 is a diagram showing the optical network in FIG. 6 focusing on an optical switch.

FIG. 11 is a diagram showing an example of a configuration of an optical network node using wavelength division multiplexing.

FIG. 12 is a diagram showing the structure of an STM-1 frame.

FIG. 13 is a diagram showing a second embodiment of path setting in the optical network node 1-1 according to the present invention.

FIG. 14 is a configuration diagram showing another embodiment of an optical network node using wavelength division multiplexing.

[Explanation of symbols]

1 ... Optical network node, 2 ... Control station, 3 ... Transmission line, 4 ... Optical path, 5 ... Control line, 6 ... Branch point, 7 ... Highway, 8 ... Insertion line highway, 9 ... Branch line highway, 10
... optical switch, 11 ... reception interface section, 12 ... insertion interface section, 13 ... transmission interface section, 1
4 ... Branch interface unit, 15 ... Control unit, 16 ... Optical amplifier, 17 ... Overhead insertion circuit, 18 ... E / O conversion circuit, 19 ... O / E conversion circuit, 20 ... Overhead processing circuit, 21 ... Monitoring control circuit, 22 ... Frame synchronization circuit,
23 ... Splitter, 24 ... Optical selector, 25 ... Selector, 26 ... Selector control circuit, 27 ... Selector, 28 ... Demultiplexer, 29 ... Combiner, 30, 31 ... Electrical switch.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04L 29/14 H04L 13/00 311 H04Q 3/52

Claims (16)

[Claims] 1. A plurality of optical switch means each having a plurality of input ports and output ports for outputting an optical signal input from any one of the input ports to any one of the output ports, and each of the optical switch means. At least one pair of insertion interfaces connected to any of the input ports and converting an electrical input signal into an optical signal to supply to the input port; and connected to any of the output ports of each of the optical switch means, Between at least one pair of branch interfaces for converting an optical output signal from the output port into an electrical signal and outputting the electrical signal, between the input port of each of the optical switch means and the optical transmission line,
Or, a plurality of receiving interfaces and transmitting interfaces connected between the output port of each of the optical switch means and the optical transmission line and amplifying an input optical signal to output to the input port or the optical transmission line, respectively, and an insertion signal line. Transmission signal distribution means for distributing the electrical transmission signal input from the plurality of insertion interfaces to one set, and electrical signals output from one set of the plurality of branch interfaces An optical network node device comprising a receiving path selecting means for selectively outputting any one of them to a branch signal line. 2. A plurality of optical switch means, each having a plurality of input ports and output ports, for outputting an optical signal input from any one of the input ports to any one of the output ports; At least one pair of insertion interfaces connected to any of the input ports and converting an electrical input signal into an optical signal having a wavelength unique to each of the optical switch means and supplying the optical signal to the input port; At least one branch interface connected to one of the output ports of the switch means for converting an optical output signal from the output port into an electric signal and outputting the electric signal; and an input port of each of the optical switch means, A plurality of receiving interfaces for amplifying an input optical signal having a wavelength unique to each optical switch and outputting the amplified optical signal to the input port. And a reception signal from each optical transmission line, which is provided for each optical transmission line for reception, is branched into a plurality of optical signals having a wavelength unique to each optical switch, and the optical signals are divided into a plurality of optical switches. A plurality of demultiplexers for distributing to the corresponding reception interfaces of the means, and a plurality of transmission interfaces connected to the output ports of the optical switch means and amplifying and outputting the optical signals output from the output ports, respectively. A plurality of multiplexers provided for each optical transmission line for transmission, which combine optical signals of different wavelengths output from corresponding transmission interfaces of the plurality of switch means and send out to the optical transmission line, Transmission signal distribution means for distributing an electric transmission signal inputted from the insertion signal line to a plurality of insertion interfaces forming one set, and one set of a plurality of branch interfaces An optical network node device comprising: a receiving path selecting means for receiving an electrical signal output from the optical signal and selectively outputting any one of them to a branch signal line. 3. A failure detection means for monitoring a signal received from the reception interface and detecting occurrence of a failure, and switching of selection input to the reception path selection means according to a failure detection result by the failure detection means. And a control means for instructing the command.
The optical network node device described in 1. 4. The optical network node device according to claim 3, wherein the fault detecting means is provided for each of the branch interfaces. 5. The control means sends a control signal for path switching to a control station of an optical network or another optical network node device according to a failure detection result by the failure detection means. The optical network node device according to claim 3 or 4, which is characterized in that. 6. A plurality of optical switch means each having a plurality of input ports and output ports for outputting an optical signal input from any one of the input ports to any one of the output ports, and each of the optical switch means. At least one pair of insertion interfaces connected to any of the input ports and converting an electrical input signal into an optical signal to supply to the input port; and connected to any of the output ports of each of the optical switch means, At least one pair of branch interfaces for converting an optical output signal from the output port into an electrical signal and outputting the electrical signal, and are connected between an input port or an output port of each of the optical switch means and an optical transmission line. A plurality of transmission interfaces and reception interfaces that amplify the input signal and output it to the input port or optical transmission line Transmission path selection means for selectively supplying an electrical transmission signal input from the insertion signal line to any one of a plurality of insertion interfaces forming a set, and output from one set of a plurality of branch interfaces An optical network node device comprising: a reception path selection unit for receiving the received electrical signal and selectively outputting any one of them to a branch signal line. 7. A plurality of optical switch means each having a plurality of input ports and output ports for outputting an optical signal input from any one of the input ports to any one of the output ports, and each of the optical switch means. At least one pair of insertion interfaces connected to any of the input ports and converting an electrical input signal into an optical signal having a wavelength unique to each of the optical switch means and supplying the optical signal to the input port; At least one branch interface connected to one of the output ports of the switch means for converting an optical output signal from the output port into an electric signal and outputting the electric signal; and an input port of each of the optical switch means, A plurality of receiving interfaces for amplifying an input optical signal having a wavelength unique to each optical switch and outputting the amplified optical signal to the input port. And a reception signal from each optical transmission line, which is provided for each optical transmission line for reception, is branched into a plurality of optical signals having a wavelength unique to each optical switch, and the optical signals are divided into a plurality of optical switches. A plurality of demultiplexers for distributing to the corresponding reception interfaces of the means, and a plurality of transmission interfaces connected to the output ports of the optical switch means and amplifying and outputting the optical signals output from the output ports, respectively. A plurality of multiplexers which are provided for each optical transmission line for transmission and which combine optical signals of different wavelengths output from the transmission interfaces corresponding to each other of the plurality of switch means and send them to the optical transmission line. A transmission path selection means for selectively supplying an electric transmission signal input from the insertion signal line to any one of a plurality of insertion interfaces forming a set; An optical network node device comprising: reception path selection means for receiving an electrical signal output from a number of branch interfaces and selectively outputting any one of them to a branch signal line. 8. A fault detection unit for monitoring a reception signal from a reception interface of each of the optical switch units and detecting a fault occurrence, and the reception path selection unit according to the fault detection result by the fault detection unit. For switching the output signal, sending a control signal for path switching to the control station of the optical network or other optical network node equipment, and for switching the path from the control station or other optical network node equipment. When receiving the control signal of
7. The control means for instructing the transmission path switching means to switch the insertion interface to which the transmission signal is supplied according to the control signal.
Alternatively, the optical network node device according to claim 7. 9. The optical network node device according to claim 8, wherein the fault detecting means is provided for each of the branch interfaces. 10. At least two optical switch means each comprising a plurality of node devices, each node device outputting an optical signal input from each of the plurality of input ports to any one of the plurality of output ports; At least one pair of insertion interfaces connected to any of the input ports of the optical switch means, converting an electrical input signal into an optical signal and supplying to the input port, and any of the output ports of the optical switch means. At least one pair of branch interfaces connected to the optical output means and converting the optical output signal from the output port into an electrical signal and outputting the electrical signal, between the input port and the optical transmission line of each of the optical switch means, or the output port. A plurality of receiving interfaces that are connected between the optical transmission line and amplify each input optical signal and output to the input port or optical transmission line. And a transmission interface, transmission signal distribution means for distributing an electric transmission signal input from the insertion signal line to a plurality of insertion interfaces forming one set, and output from one set of a plurality of branch interfaces. Reception path selection means for receiving an electrical signal and selectively outputting any one of them to a branch signal line, and fault detection for monitoring the signal received by the reception interface and detecting the occurrence of a fault A method of communicating between node devices in an optical network, comprising: a plurality of optical switching means of the own node device, wherein two node devices serving as end points of an optical path receive transmission signals input from respective insertion signal lines. From the optical transmission line to the other node device, the transmission signal is transmitted in parallel via a plurality of paths and a plurality of different optical transmission lines are transmitted. When one of the transmission signals from the partner node device received from the path is selected by the selecting means and output to the branch signal line, and when the failure detecting means detects an abnormality in the reception signal being selected, the branching is performed. A communication method in an optical network, characterized in that a received signal to be output to a signal line is switched to one from another optical transmission line by the selecting means. 11. A communication method in an optical network according to claim 10, wherein the optical network has a control station connected to a plurality of node devices, and one of the node devices that has detected an abnormality in a received signal, Notifying the control station of the abnormality of the reception path, the control station receiving the abnormality notification transmits a control signal for instructing the other node device to switch the path, and the other node device controls the above 11. The communication method in an optical network according to claim 10, wherein the selecting means is operated in response to a signal to switch the output to the branch signal line to a reception signal from another optical transmission line. 12. One of the node devices that has detected an abnormality in the received signal and the other node device that is instructed to switch by the control station pass through the same node device by their respective selection devices. The communication method in the optical network according to claim 11, wherein the reception signal from the optical transmission line is switched to. 13. A plurality of node devices each comprising at least two optical switch means for outputting an optical signal input from each of the plurality of input ports to any one of the plurality of output ports, and each of the above-mentioned respective switch devices. At least one pair of insertion interfaces connected to any of the input ports of the optical switch means, converting an electrical input signal into an optical signal and supplying to the input port, and any of the output ports of the optical switch means. At least one pair of branch interfaces connected to the optical output means and converting the optical output signal from the output port into an electrical signal and outputting the electrical signal, between the input port and the optical transmission line of each of the optical switch means, or the output port. A plurality of receiving interfaces that are connected between the optical transmission line and amplify each input optical signal and output to the input port or optical transmission line. Chair and transmission interface, transmission path selection means for selectively supplying an electrical transmission signal input from the insertion signal line to any one of a plurality of insertion interfaces forming a set, and a set of transmission path selection means. Reception path selection means for receiving an electrical signal output from a plurality of branch interfaces and selectively outputting any one of them to a branch signal line, and monitoring a signal received by the reception interface to check for a failure A communication method between node devices in an optical network, comprising fault detection means for detecting occurrence, wherein two node devices, which are end points of an optical path, are selected by respective transmission path selection means and reception path selection means. A signal is transmitted and received via a communication path composed of a pair of optical transmission paths passing through any one of the optical switching means that is set, and the two node devices are connected. On the other hand, when the failure detection means detects an abnormality in the reception signal being selected, the transmission path selection means and the reception path selection means make a new pair of optical transmission lines passing through another optical switch means. A communication method in an optical network, characterized in that a signal is transmitted and received by switching to a different communication path. 14. A node device that has detected an abnormality in the received signal notifies the other node device as a communication partner or a control station connected to each node device of the abnormality in the communication path, and the other node device is 14. The communication method in the optical network according to claim 13, wherein the switching to the new communication path is performed in response to a notification from the node device or the control station that has detected the abnormality. 15. A node device on the transmission side distributes a transmission signal to an optical network to a plurality of electric / optical conversion means at the stage of electric signals,
The optical signals converted by the respective electrical / optical conversion means are sent to a plurality of transmission paths via different optical switches, and the receiving side node device receives a plurality of optical signals received from the plurality of transmission paths as separate optical signals. One of the plurality of reception signals converted into an electric signal is selectively taken out through a switch through a plurality of optical / electrical conversion means, and when an abnormality is detected in the reception signal, any other optical signal is detected. / A communication method in an optical network, wherein an electric signal output from an electric conversion device is taken out as a reception signal. 16. A transmitting side node device selects one of a plurality of electrical / optical converting means for transmitting a signal to be transmitted to an optical network at an electric signal stage.
And transmits the optical signal converted by the electrical / optical conversion means to the first transmission line via one of the plurality of optical switches, and the receiving side node device transmits the first transmission signal. The optical signal passing through the optical path is guided to the optical / electrical converting means via one of the plurality of optical switches, the electric signal converted by the optical / electrical converting means is taken out as a received signal, and the receiving side node device is provided. In case of detecting an abnormality of the received signal in, the transmission side node device or the control station is notified of the transmission path abnormality, and the transmission side node device notified of the transmission path abnormality transmits the transmission signal to the optical network to another The receiving side node device is branched to any one of the electric / optical converting means, and the optical signal converted by the electric / optical converting means is sent out to the second transmission line via any of the other optical switches. However, if the optical signal that has passed through the second transmission line is A communication method in an optical network, which is characterized in that it is led to another optical / electrical converting means via a switch and the electric signal converted by the optical / electrical converting means is taken out as a reception signal.