JPH0697950A - Optical ring system - Google Patents

Abstract

PURPOSE:To obtain the system being superior in reliability and flexibility by a concise system by providing a wavelength multiple bidirectional transmission function using two different wavelength, and a wavelength selecting function at the time of fault, in each node. CONSTITUTION:In an optical fiber 11, two kinds of optical signals of service signal wavelength lambdas and protection wavelength lambdap are multiplexed in wavelength and transmitted. When each node 1-4 transmits information, a wavelength transmitting part 12 transmits all the same information in mutual reverse direction by both of lambdas and lambdap. In the case that a fault is generated between the nodes 3-4, with regard to lambdas, the downstream node 3 switches wavelength selected by a wavelength selecting part 13 to lambdap. In this case, the node 2 selects lambdas as for the information transmitted by the node 3, and selects lambdap as for the information transmitted by the node 1. In such a way, a communication is continued, and the system being superior in reliability and flexibility can be constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring system using an optical fiber. More specifically, it relates to a fault handling method for an optical ring system.

[0002]

2. Description of the Related Art An example of a configuration conventionally proposed as a failure processing method in an optical ring system will be described with reference to FIG. Each node is connected in a ring shape by a transmission line formed of an optical fiber. In detail, the transmission path is composed of a service fiber 101 and a protection fiber 102.

Each node receives an optical signal transmitted by an optical fiber of a transmission line and sends the optical signal to the optical fiber. In order to realize this function, each node has an optical branching unit 103 and a fiber selecting unit 104. The optical branching unit 103 sends the same information to two optical fibers when sending information at each node. Service fiber 101 and protection fiber 1
02, the information transmission directions are opposite to each other.
Here, the information transmission direction of the service fiber 101 is clockwise, and the information transmission direction of the protection fiber 102 is counterclockwise.

The fiber selector 104 selects one of the two optical fibers when receiving information at each node. Normally, the fiber selection units of all the nodes select the service fiber 101.

[0005] Here, the failure processing when a failure occurs in the transmission path and the signal transmission is interrupted will be described. In this case, regarding the service fiber, the node downstream from the point where the failure has occurred cannot receive the information. This node can continue transmission and reception by newly selecting the protection fiber 102 by the fiber selection unit. For example, when a failure occurs between the node 3 and the node 4, the node 3 is located downstream from the failure point and therefore cannot receive the information sent by the node 1. Therefore, the node 3 selects the protection fiber 102 by the fiber selection unit. As a result, the node 3 can receive the information transmitted by the node 1 via the protection fiber 102.

Another example of the conventionally proposed failure processing method will be described with reference to FIG. Also in this configuration, four nodes are connected by a ring-shaped transmission path. This is different from the above-described example in that the service fiber 121 and the protection fiber 122 are each composed of a pair of optical fibers because bidirectional communication is performed between the nodes. In this example, information is normally transmitted using only the service fiber 121.

The operation when a failure occurs will now be described. For example, when a failure occurs in the transmission line between the node 1 and the node 4 and it becomes impossible to transmit information,
By performing loopback to the protection fiber in the node 1 and the node 4 adjacent to the failure point, transmission / reception can be continued.

[0008]

However, all of the above-mentioned examples require protection fibers for fault handling. This means that when the communication capacity increases and an optical fiber is added as a transmission line, a protection fiber must be added to ensure system reliability. As described above, the conventional techniques have problems that the system is complicated, the cost is disadvantageous, and the system is not flexible in terms of expandability. An object of the present invention is to provide a ring system having a simple system configuration, excellent reliability and flexibility.

[0009]

According to a first aspect of the invention, there is provided a wavelength multiplexing two-way transmission function using two different wavelengths for each node,
It is provided with a wavelength selection function at the time of failure. Second,
In the third invention, each node is provided with a wavelength multiplexing loopback function at the time of failure occurrence and a wavelength selection function.

[0010]

According to the first aspect of the invention, each node wavelength-multiplexes the same information by using the service wavelength and the protection wavelength, respectively, and transmits them in mutually opposite directions. Each node selects and receives a service wavelength from the signals that are wavelength-multiplexed and transmitted. When a failure occurs, the node that cannot receive the service wavelength receives the information to be transmitted, using the selected wavelength as the protection wavelength. In the second and third inventions, each node normally transmits / receives information at the service wavelength.
When a failure occurs, the pair of nodes adjacent to the failure point convert the received service wavelength to the protection wavelength and loop back to the other node. The other node receives this protection wavelength and reconverts it to the service wavelength.

[0011]

FIG. 1 is a diagram for explaining a first embodiment of the present invention. Note that FIG. 1 shows a system having four nodes, but this does not limit the number of nodes. In this embodiment, the transmission line is composed of one optical fiber 11.

In this optical fiber 11, two kinds of optical signals having a service signal wavelength λs and a protection wavelength λp are wavelength-multiplexed and transmitted. In the figure, the service signal wavelength λs is a solid line, and the protection wavelength λs is
p is indicated by a dotted line. Each optical signal is an optical fiber 1
1 are transmitted in the opposite directions to each other. Here, the direction in which the service wavelength λs is transmitted is clockwise, and the direction in which the protection wavelength λp is transmitted is counterclockwise. However, this does not limit the direction of information transmission.

Each node has a wavelength transmitter 12 and a wavelength selector 13. The wavelength transmitter 12 is used when each node transmits information to the optical fiber 11. The wavelength receiver 13 is used when each node receives information from the optical fiber 11. When each node attempts to transmit information, the wavelength transmitter 12 outputs both the service wavelength λs and the protection wavelength λp. That is, the wavelength transmitter 12 wavelength-multiplexes and transmits each wavelength to the optical fiber 11. At this time, each wavelength transmits exactly the same information. Each wavelength is transmitted in the optical fiber 11 in the direction described above. In a normal state, the wavelength selection unit 13 of each node selects the service wavelength λs from the signal transmitted by optical wavelength multiplexing and receives the service wavelength λs. Thereby, communication between the nodes is performed.

Next, the operation when a failure occurs will be described with reference to FIG. For example, when a failure occurs between the node 3 and the node 4, the node 3 downstream of the failure point with respect to the service wavelength λs cannot receive the information. In this case, the node 3 switches the wavelength to be selected from the service wavelength λs to the protection wavelength λp by the wavelength selection unit 13. As described above, the information transmitted by the protection wavelength λp is the same as the information transmitted by the service wavelength λs, and only the transmission direction is opposite. That is, with respect to the protection wavelength λp, the node 3 is located upstream of the obstacle point. Therefore, the node 3 can receive the protection wavelength λp, which allows the communication to continue. In FIG. 2, it will be understood that the information transmitted by the node 1 reaches the node 3 by the protection wavelength λp and the information transmitted by the node 3 reaches the node 1 by the service wavelength λs.

Now, the operation of the node 2 will be described. Figure 2
In the state shown in (2), the node 2 is located downstream of the failure point with respect to the information transmitted by the node 1 with respect to the service wavelength λs. On the other hand, the information transmitted by the node 3 is located upstream of the failure point. That is, the node 2 can receive the information transmitted by the node 3 using the service wavelength λs as usual. On the other hand, the information transmitted by the node 1 cannot be received by the service wavelength λs. In this case node 2
For the information transmitted by the node 3, the service wavelength λs is selected as usual. For the information transmitted by the node 1, the protection wavelength λp is selected. The same operation as that of the node 2 is also performed at the node 4.

Thus, each node has a service wavelength λ.
Regarding s, depending on whether or not the information transmitted by another node can be received, if it can be received, the service wavelength λs
When the signal cannot be received, the protection wavelength λp is selected. As described above, in the first embodiment, normally, the service wavelength λs and the protection wavelength λp are bidirectionally wavelength-division multiplexed and transmitted. Here, each node appropriately selects the service wavelength λs or the protection wavelength λp, so that the communication can be continued even if a failure occurs in the transmission path.

A second embodiment of the present invention will be described with reference to FIG. The ring system shown in FIG. 3 is a system that performs bidirectional communication using a pair of optical fibers as a transmission path.
In each optical fiber, information is transmitted in opposite directions. Here, for the following description, the transmission path is configured by the first loop 301 in which the optical signal transmission direction is clockwise and the second loop 302 in which the optical signal transmission direction is counterclockwise. Be present. Each node has an optical switch unit for switching an optical signal on the transmission line. Further, as in the first embodiment, it has a branching / adding unit that wavelength-multiplexes and transmits information to an optical fiber that is a transmission line, and that selectively receives information of a desired wavelength from an optical signal on the transmission line. Under normal conditions, only the service wavelength λs is used for transmitting information. Here again, the service wavelength λs is shown by a solid line.

Next, the operation when a failure occurs will be described with reference to FIG. Here, node 1 and node 4
Described below is a case where a failure has occurred between and. In this case, the node 1 and the node 4 adjacent to the fault point perform wavelength multiplexing loopback to continue communication.

Therefore, each node has a service wavelength λs.
And a wavelength conversion function for protection wavelength λp. First, in the node 1, normally, the first loop 3
The information sent from the node 1 to the node 4 at 01 is converted from the service wavelength λs to the protection wavelength λp in the optical switch portion of the node 1.
After that, the protection wavelength λp is looped back to the second loop 302 and is sent to the node 2. The protection wavelength λp passes through the nodes 2 and 3 as it is and reaches the node 4. Then, it is converted back to the service wavelength λs at the node 4,
It loops back to the first loop 301. This allows the first loop 301 between the node 1 and the node 4.
The path has been secured without being disconnected.

Similarly, in the node 4, normally, the second node
The information transmitted from the node 4 to the node 1 in the loop 302 is converted from the service wavelength λs to the protection wavelength λp in the optical switch portion of the node 4. After that, the protection wavelength λp is looped back to the first loop 301 and is sent to the node 3. This protection wavelength λp arrives at node 1 where it is reconverted to the service wavelength λs. Then, it is looped back to the second loop 302.
Now, between node 4 and node 1, the second loop 30
The path has been secured without disconnecting 2. As described above, the protection wavelength λp is used to secure the path between the node 1 and the node 4 under the operation at the time of failure. As a result of the path being secured at the protection wavelength λp, the clockwise information transmission in the first loop 301 and the counterclockwise information transmission in the second loop 302 are continued even when a failure occurs.

As described above, in the second embodiment, in a ring system for performing two-way communication on a transmission line composed of a pair of optical fibers, information transmission is normally performed using the service wavelength λs. When a failure occurs, the node adjacent to the failure point performs wavelength conversion from the service wavelength λs to the protection wavelength λp, and loops back to the other optical fiber. As a result, even when a failure occurs, a path is secured between the two nodes adjacent to the failure point.

FIG. 5 illustrates a third embodiment of the present invention. The ring system shown in FIG. 5 differs from the ring system of the second embodiment in that a single optical fiber is used to form a transmission line and unidirectional communication is performed.

In this system, for example, when a failure occurs between the node 1 and the node 4 and the transmission becomes impossible, the optical switch units of the nodes 1 and 4 which are adjacent points to the failure are used for service. The wavelength conversion from the wavelength λs to the protection wavelength λp is performed. That is, in the node 1, after the wavelength conversion, the protection wavelength λp
Loopback toward node 4. On the other hand, the node 4 secures a path by looping back the protection wavelength λp toward the node 1.

As described above, in this embodiment, in a ring system which performs one-way communication by a transmission line composed of a single optical fiber, wavelength conversion is performed when a failure occurs, and a single optical fiber is formed. By performing loopback, it is possible to secure a path between adjacent points with a failure.

[0025]

As described above, according to the first invention,
The service wavelength and the protection wavelength are bi-directionally wavelength-multiplexed and transmitted, and when a failure occurs, the node that cannot receive the service wavelength selects and receives the protection wavelength. In the second invention, in a ring system in which a transmission line is composed of a pair of optical fibers, information is transmitted at a service wavelength during normal operation, and the service wavelength is changed to a protection wavelength when a failure occurs. It was converted and wavelength-multiplexed loopback was performed on the other optical fiber. Furthermore, in the third invention,
In a ring system in which a transmission line is composed of a single optical fiber, information is transmitted at a service wavelength during normal operation, and when a failure occurs, the service wavelength is converted to a protection wavelength, and this is converted into a wavelength. Added multiple loopback.

Therefore, a path can be secured even when a failure occurs without requiring a protection fiber.
In this case, the transmission capacity of the entire system and the reliability of the system are
It never changes. Further, even if the number of optical fibers is increased to cope with the increase in communication capacity or the wavelength multiplicity is increased, it is not necessary to add an optical fiber. In this way, it is possible to obtain a ring system having a simple system configuration, which is excellent in reliability and flexibility.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a failure processing operation in the first embodiment.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a failure processing operation in the second embodiment.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram showing an example of a conventional failure processing method.

FIG. 7 is a diagram showing another example of a conventional failure processing method.

[Explanation of symbols]

 11 Optical Fiber 12 Wavelength Transmitter 13 Wavelength Selector 301 First Loop 302 Second Loop

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 8220-5K H04B 9/00 K

Claims (5)

[Claims] 1. In an optical ring system in which a plurality of nodes are connected in a ring shape by an optical fiber transmission path, a first wavelength transmitted in a first direction at a normal time and a protection for performing a failure, An optical ring system, characterized in that information is transmitted by a second wavelength transmitted in a second direction opposite to the first direction. 2. An optical ring system in which a plurality of nodes are connected in a ring shape by an optical fiber transmission line, wherein the node is a wavelength transmitter for wavelength-multiplexing and transmitting a first wavelength and a second wavelength. A wavelength selecting unit for selectively receiving a desired wavelength from the transmitted optical signal, wherein the node is configured such that the node transmits the first wavelength and the second wavelength to the optical fiber transmission line. Wavelength-multiplexing in the reverse direction, normally receiving the first wavelength selectively, and receiving the second wavelength selectively when it is impossible to receive the first wavelength when a failure occurs. An optical ring system characterized by. 3. An optical ring system in which a plurality of nodes are connected in a ring shape by an optical fiber transmission line, wherein the node normally transmits and receives information at a first wavelength and is adjacent to a failure point when a failure occurs. Of the pair of nodes, the node that receives the first wavelength converts the first wavelength to the second wavelength and performs wavelength multiplexing loopback to the other node, and the other that receives the second wavelength. The optical ring system according to claim 1, wherein the second node reconverts the second wavelength into the first wavelength to secure a path under failure. 4. The optical ring system according to claim 3, wherein the plurality of nodes are connected in a ring shape by a single optical fiber transmission line. 5. The optical fiber transmission from a first loop for transmitting information in a first direction and a second loop for transmitting information in a second direction opposite to the first direction. The ring system according to claim 3, wherein a path is configured, and among the pair of nodes adjacent to the point of failure, the node that has received the first wavelength by the first loop outputs the first wavelength. Converting the second wavelength to a second wavelength, performing wavelength-multiplexed loopback on the second loop, and of the pair of nodes adjacent to the failure point, the first wavelength is generated by the second loop. The node that has received the first wavelength converts the first wavelength to a second wavelength, performs wavelength multiplexing loopback on the second wavelength to the first loop, and the pair of nodes further includes the first or the first wavelength. Received in loop 2 Reconverting the second wavelength into a first wavelength,
An optical ring system that secures a path under a fault.