JP2001274751A - Failure recovery method and system for optical path in wavelength division multiplexing network - Google Patents

Abstract

(57) [Problem] To provide an optical path failure recovery method and system that enables appropriate signal switching processing for signals from both a client having no self-healing function and a self-healing client. . In an optical network, a network node includes a switching module, and the switching module transmits a signal from a client before multiplexing the signal with another signal for restoration of a failure of an optical path. By switching the optical path of the selected individual signal from the working fiber 104 to the protection fiber 106 at the wavelength level, the client 1 having no self-healing function can be used.
Only the signal from 10a-b is switched, and the signal from the client 134 having the self-healing function is subjected to its own protection switching process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the field of optical networks, and more particularly, to a method and system for restoring an optical path in a wavelength division multiplexing network.

[0002]

2. Description of the Related Art With the explosion of Internet traffic, Dense Wavelength Division Multiplexing (DWDM) is known.
There is an increasing demand for large capacity, low cost, and highly reliable data transmission in h division multiplexing networks. If a failure occurs in the optical path of the DWDM network, a large amount of data may be lost.
The failure recovery method and system are
Used to switch data traffic to an alternate channel. However, conventional methods and systems for failure recovery have not been effective for DWDM networks.

[0003] Time division multiplexing (TDM)
exing) According to one prior art on the signal failure recovery scheme at the nodes of the network, the signal is SONET.
(Synchronous Optical NETwork) / SDH (Synchrono
us Digital Hierarchy), digital cross connect, bi-directional line switched ring (BLSR), uni-directional path switched path (UPSR)
ng) etc. In the SONET / SDH system, switching is performed in the time domain. The time division multiplex switch has a plurality of ports corresponding to time slots. The input / output port can be connected by selecting each corresponding time slot. This network is
It is suitable for telephone network that handles a small amount of traffic. However, IP data traffic that is promoting the increase in the capacity of current networks is composed of large-capacity point-to-point traffic from IP routers and ATM (Asynchronous Transfer Mode) switches. Already, IP routers and ATMs (Asynchron
ousTransfer Mode) The transmission speed of the signal output from the exchange becomes equal to the path speed of the SONET / SDH multiplex transmission equipment. For IP data traffic, the multiplexing function and switching function of SONET / SDH become unnecessary. I have. Therefore, realization of failure recovery in the optical domain is required in a wavelength division multiplexing network. There are two methods for switching failure recovery in a wavelength division multiplexing network: switching with wavelength-multiplexed optical signals and switching with wavelength units.

According to one prior art relating to a signal failure recovery method in a DWDM network node, there is a failure recovery function of an optical cross-connect system. According to an optical cross-connect system designed for a mesh network, a plurality of selectable alternative paths are provided, and efficient use of a fault recovery resource is possible. But,
The mesh network optical cross-connect system is complicated to manage and takes time to recover. For example, US 5,457,55
6, an optical cross-connect system having a network rescue function is disclosed. This system manages three switching layers. The first is an optical space switch that switches with wavelength-multiplexed optical signals, the second is an optical space switch that switches in wavelength units, and the third is a time division multiplex switch. Since each layer has its own recovery function, this system requires a network center that manages switches in each layer in order to prevent recovery switching collisions in each layer. When a signal abnormality is detected on the network, it is communicated to the network center. In order to prevent switching collision, it is necessary to determine in which layer the network center performs switching and issue a request to execute switching. Another optical cross-connect system that performs high-speed recovery using a ring topology has been proposed. For example, in US 5,457,556, optical switching and SONET time division multiplexing switches are combined. However, this example is not suitable for large-capacity traffic due to the time division multiplex switch. Also, an optical ring network that performs switching by using a wavelength multiplexed optical signal has been proposed. In general, various clients are connected to a wavelength division multiplexing device,
SONET / SDH with automatic recovery function in such a system
When devices are connected together, a switching collision occurs.
Therefore, management becomes very complicated. US 5,870,21
2 discloses an optical cross-connect system that switches in wavelength units. However, this is link-based switching, and all nodes passing through the optical path need a switching function, which is not economical.

[0005]

In a DWDM network node, an IP router, an ATM switch, or an existing SONET is used.
Various clients are connected, such as a / SDH multiplex transmission device. Data traffic from IP routers and ATM switches does not require the multiplexing function and switching function of SONET / SDH. Therefore, it is necessary to realize restoration of a failure in the optical domain in a wavelength division multiplexing network. In addition, some connected clients have a self-healing function while others do not. When switching is performed in the optical domain, switching collision with another system poses a problem. In addition, if a switching function is required for all nodes through which an optical path passes, a large-scale switch is required, and efficiency and economy become problems.

The present invention has been made in consideration of the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for restoring an optical path in an optical network, which can eliminate or reduce the above problems and disadvantages. And a system.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a method and system for restoring an optical path in an optical network is provided which substantially eliminates or reduces disadvantages and problems associated with prior art systems and methods. Is provided.

According to one embodiment of the present invention, a network element for restoring an optical path in a wavelength division multiplexing network is disclosed. The network receives a signal, multiplexes the received signal with a first signal group, and forms a working path (working path).
h) a first multiplexer for generating a first combined signal for transmission to h). A second multiplexer receives the signal, multiplexes the signal with a second group of signals, and generates a second multiplexed signal to be transmitted to a protection path. Path-based swi
tch) receives a signal from the client, sends the signal to the first multiplexer, where it is multiplexed and transmitted to the working path, and when a failure occurs in the working path, the signal is transmitted. Is switched to the second multiplexer independently of the first signal group, where the signal is multiplexed and transmitted to the protection path.

According to another embodiment of the present invention, a network component for restoring an optical path in a wavelength division multiplexing network is disclosed. The network includes a first multiplexer that receives a signal, multiplexes the received signal with a first signal group, and generates a first multiplexed signal for transmission to a working optical path. The second multiplexer is
Receiving the signal, multiplexing the signal with a second signal group, and generating a second multiplexed signal to be transmitted on the standby optical path. The third multiplexer receives the signal, multiplexes the signal with a third signal group, and generates a third multiplexed signal to be transmitted on the standby optical path. The path-based switch receives the signal from the client, sends the signal to the first multiplexer, where it is multiplexed and transmitted to the working optical path, and when a failure occurs in the working optical path. , The signal is switched to the second multiplexer independently of the first signal group, where it is multiplexed and transmitted to the standby optical path,
If a failure occurs in the working system optical path and the protection system optical path of the second multiplexer, the signal is switched to the third multiplexer independently of the first signal group, where the signal is combined. It is processed and transmitted to the standby optical path.

According to another embodiment of the present invention, a wavelength division multiplexing network is disclosed. The network includes a client for transmitting a first signal to a first node of the wavelength division multiplexing network for retransmission to a second node of the wavelength division multiplexing network. The self-healing client transmits a second signal to a first node of the wavelength division multiplexing network for retransmission to a second node of the wavelength division multiplexing network, and transmits the second signal independently of the first signal. Protection switching processing (prot
Section switching). The first node comprises a path-based switch for a first signal, the path-based switch performing a protection switching process for the first signal independently of the second signal.

According to another embodiment of the present invention, a method for restoring an optical path in a wavelength division multiplexing network is disclosed. A first signal for transmission to the working path is received from the client. A second signal for transmission to the working path is received from the self-healing client. It is determined that a failure has occurred in the working path. The first signal is switched to the backup path independently of the second signal. Self-healing clients
The protection switching process for the second signal can be performed independently. The first signal is multiplexed with a group of signals to generate a multiplexed signal, and the multiplexed signal is transmitted to a protection path.

According to another embodiment of the present invention, a method for restoring an optical path in a wavelength division multiplexing network is disclosed. A signal is received from the client. Using a path-based switch, this signal is appropriately coupled to one of the first multiplexer for transmitting to the working path and the second multiplexer for transmitting to the protection path. Switching is performed according to the state of the active path. When the signal is received by the first multiplexer, the signal is multiplexed with the first signal group to generate a first multiplexed signal to be transmitted to the working path. When the signal is received by the second multiplexer, the signal is multiplexed with the second signal group, and a second multiplexed signal to be transmitted to the protection path is generated.

[0013]

FIG. 1 is a block diagram of an optical network 100 according to an embodiment of the present invention. As shown in FIG. 1, the optical network 100 includes a plurality of network components connected to each other by an optical transmission medium, and includes network nodes 101 and 103.
Clients 110a-b and 134 send signals through network nodes 101,103. The network node 101 is connected to, for example, an optical cross connect (OX).
C) path-based switching module (switching modu)
le) 102, the switching module 102
The switching process is executed by switching the optical path of the selected individual signal from the working fiber 104 to the protection fiber 106 at the wavelength level. The switching module 102 switches the signal from the client before the signal is multiplexed with another signal, thereby appropriately performing a switching process.
The optical path is a wavelength path from the source network node closest to the client that is the source of the signal to the destination network node closest to the destination client. Is also good. In the embodiment shown in FIG. 1, only the signals from clients 110a-b are switched. As will be described in more detail below, the client 134 has its own self-healing function. Network node 103
Is the same as that of the network node 101. The network node 103 includes a switching module 120, and the switching module 120 switches a selected individual signal from the working fiber 104 to the protection fiber 106 at a wavelength level for restoration of an optical path failure.

In this embodiment, the client 110a-
b performs signal communication with the OXC 102. OXC102,
It is realized by software, hardware, or any appropriate combination of these. OXC
Switch 112a of 102 receives a signal from client 110a, and switch 112b of OXC 102 receives a signal from client 110b. OXC102
Determines whether signal communication via the working fiber 104 is possible. When the working fiber 104 can be used for signal communication, the OXC 102 operates as a wavelength division multiplexing device (WDM).
The signal is communicated to 114. WDM 114 converts this signal
The signal is multiplexed with another input signal such as a signal from the client 134. The WDM 114 communicates the multiplexed signal to the WDM 116 via the working fiber 104. WDM1
16 separates input signals and communicates signals from clients 110a-b to OXC 120 with switches 122a-b. More specifically, switch 122a receives a signal from client 110a and switches
b receives a signal from client 110b. OX
C120 communicates these signals to clients 124a-b. More specifically, client 124a receives a signal from client 110a, and client 124b receives a signal from client 110b.

When the working fiber 104 cannot be used for signal communication, the OXC 102 communicates with the clients 110a-b.
Is switched to the WDM 130. WDM130
Multiplexes the input signal with the signal from client 134. The WDM 130 is connected to the WD via the standby fiber 106.
The multiplexed signal is communicated to M132. WDM 132 separates the signal and communicates the signal to OXC 120. OXC
120 communicates signals from clients 110a-b to clients 124a-b, respectively.

The optical network 100 has a client 13 which has a self-healing or protection / restoration function.
4 and 136. The client 134 determines whether the working fiber 104 can be used for signal communication. When signal communication through the working fiber 104 is possible, the client 134 communicates a signal to the WDM 114. The signal from client 134 is OXC10
2, the switching conflict with the protection or restoration function of the OXC 102 can be prevented from occurring. Furthermore, by not using the protection and restoration function of the OXC 102 for the client 134,
The function is preserved. WDM 114 multiplexes the signal from client 134 with the signals from clients 110a-b. Next, the multiplexed signal is passed through the working fiber 104 to the WD for separating the input signal.
Communicated to M116. WDM116 is Client 1
The signal from 34 is communicated to client 136. If the working fiber 104 cannot be used for signal communication,
Client 134 communicates signals to WDM 130, where signals from client 134 are transmitted to client 11
Multiplexed with the signals from 0a-b. The multiplexed signal is communicated via the standby fiber 106 to the WDM 132 that separates the input signal. WDM 132 communicates signals from client 134 to client 136.

Signals can also be communicated in the opposite direction.
The signals are transmitted from the clients 124a-b to the OXC 120 which determines whether signal communication is possible in the working fiber 104. When signal communication through the working fiber 104 is possible, the signals from the clients 124a-b are transmitted to the OXC 120, the WDM 116, and the working fiber 10a.
4, communicated to clients 110a-b through WDM 114 and OXC 102. Working fiber 10
4 is not possible, the signals from clients 124a-b will be OXC120, WDM1
32, standby fiber 106, WDM 130 and OX
It is communicated to clients 110a-b through C102. Similarly, client 136 to client 1
Signal communication is performed to 34. If the client 136 determines that signal communication through the working fiber 104 is possible, the signal from the client 136 is transmitted to the WDM 11
6. Communication is made to the client 134 through the working fiber 104 and the WDM 114. If it is determined that signal communication through the working fiber 104 cannot be performed, a signal from the client 136 is communicated to the client 134 through the WDM 132, the protection fiber 106, and the WDM 132.

FIG. 2 is a block diagram of an intermediate network node 200 used in the optical network 100 of FIG. 1 according to one embodiment of the present invention. Network node 2
00 is provided with the OXC 102 that performs optical path failure recovery as described with reference to FIG. The network node 200 further includes WDMs 114, 130, 214, 23 connected to each other by an optical communication medium as shown in FIG.
0, active system fibers 104 and 204 and standby system fibers 106 and 206. The OXC 102 receives signals from the clients 110a-b, and determines whether signal communication is possible with each of the working fibers 104 and 204. If signal communication through the working fibers 104, 204 is possible, signals from the clients 110a-b are communicated through the working fibers 104, 204. When the working fiber 104 or 204 cannot be used for signal communication, the OXC 102 switches individual signals at the wavelength level and performs signal communication through the protection fiber 106 or 206, respectively. The OXC 102 performs switching processing of individual signals by switching before a signal from a client is multiplexed with another signal.

Each of the clients 110a-b has a performance monitor (PM) 202.
a-b. Performance monitoring monitors 202a-b provide fault detection and isolation information such as signal loss and signal degradation. The OXC 102 includes a controller 210, an optical switch 212, and a performance monitoring monitor 214.
The controller 210 controls the operation of the OXC 102 and issues a control instruction to the optical switch 212. Optical switch 21
When the working fiber 104 cannot be used, the communication path is changed from the working fiber 104 to the protection fiber 10.
6 and if the working fiber 204 cannot be used, the communication path is switched from the working fiber 204 to the protection fiber 206. The performance monitoring monitor 214 provides the same information as the performance monitoring monitors 202a-b, and information on whether the working fibers 104 and 204 are available. Performance monitoring monitors 214, 202a-b communicate signal information to controller 210 and other network components. Clients 110a-b communicate with OXC 102 using any suitable interface, such as, for example, a hardware interface or a network device manager (element manager) 203. The network device manager 203 monitors the signal information of the input signal and communicates the signal information to the OXC 102 and other network components.

In one embodiment of the present invention, a line signal regenerator (LRE) 240, 242 (line regenerator)
Are connected to the OXC 102 and the WDMs 230 and 130 by standby fibers 206 and 106. LRE2
40, 242 respectively to improve the signal quality,
The signal transmitted through the standby fibers 206 and 106 is reproduced. The LREs 240 and 242 perform performance monitoring and monitoring of the standby fibers 206 and 106, respectively, and prevent the optical amplifiers of the standby fibers from shutting down. LRE 240 and 242 are two-way WDM
The system can be used to perform wavelength conversion processing, and can also be used as an access means to a signal overhead section for providing a communication channel using spare bytes in the overhead section. Also, LRE
Transponder (transponde) instead of 240, 242
r) may be used.

As shown in FIG. 2, the WDM 114 includes a performance monitoring monitor 220a, a WDM 222a, and an optical amplifier 224a connected by a bus or other appropriate medium.
And an optical monitoring channel (OSC) 226a. Performance monitoring monitor 220a receives signals from OXC 102 and provides signal information similar to that provided by performance monitoring monitors 202a-b. Performance monitoring monitor 220a
Communicates signaling information to the OXC 102 and other network nodes. WDM 222a is a performance monitoring monitor 220
a) and multiplexes the signal. OA224
a receives the multiplexed signal from WDM 222a and amplifies the signal. The OSC 226a manages a management channel, and receives signal information from the performance monitoring monitors 202a-b via the controller 210. OSC 226a communicates this and other information in the overhead portion of the signal communicated over working fiber 104. The WDM 114 performs signal communication through the working fiber 104. WDM114
Through can also be transmitted in the reverse direction. WD
M130, 214, and 230 have the same configuration.
The WDMs 130, 214, and 230 are performance monitoring monitors 220b-d, WDMs 222b-d, and OA 224b, respectively.
-D and OSC 226b-d, and each component is a performance monitoring monitor 220a and a WDM 222, respectively.
a, OA 224a and OSC 226a.

FIG. 3 is a block diagram of the OXC 102 having a card shelf configuration according to an embodiment of the present invention. In the present embodiment, the optical network 100
Is divided into a plurality of sublayers corresponding to wavelength planes 250a-b. Wavelength plane 250
ab allows the insertion of a switching unit for controlling the switching of the signal having the selected wavelength. OXC102,
The OXC 102 includes an I / O controller 252 for connecting the OXC 102 to another module of the network node. I /
O252 is connected to a master shelf controller 254. The master shelf controller 254 manages alarm and status information of input / output signals. Master shelf controller 25
4 is connected to wavelength planes 250a-c through wavelength unit controllers 251a-c. Each wavelength unit controller 251a-c switches a signal of a specific wavelength. If more wavelength planes are needed, the slave shelf controller 256 that manages alarms and status information for input and output signals may be extended. The slave shelf controller 256 is the wavelength unit controller 2
58a-c. Wavelength unit controller 2
58a-c switch signals of specific wavelengths. The slave shelf controllers 260 and 262 are connected to similar wavelength unit controllers and used for switching on another wavelength plane.

FIG. 4 shows an embodiment of the present invention.
1 is a block diagram of a node comprising transponders 302, 304, 306 that can be used in the optical network 100 of FIG. Transponder 302 is Client 1
10a-b and OXC102. Transponder 304 includes OXC 102 and WDM 214,
230. Similarly, transponder 30
6 is connected to the OXC 102 and the WDMs 114 and 130. Transponders convert optical signals into electrical signals that are more costly but can improve optical network performance. Transponders 302, 30
4, 306, for signals transmitted through itself,
It has functions for monitoring, fault detection and fault isolation. Also, the transponders 302, 304, 306
It has a function of accessing the overhead part of the signal and performing communication by reading or writing. Therefore, the transponders 302, 304, 306
Used to provide information about bit error rate, signal loss, alarm notification and automatic protection switching.

FIG. 5 shows an embodiment of the present invention.
3 is a block diagram of a switch (SW) 402 that can be used by a network node similar to the network node 200 of FIG. As shown in FIG. 5, the OXC 102 includes working fibers 104 and 204 and protection fibers 106 and 20.
6, a switch 402 connected to the WDMs 114, 130, 214, 230 and the clients 110a-b by an optical transmission medium. Each component has the configuration and operation as described above. Performance monitoring monitors, transponders or other suitable network components may be located between clients 110a-b and switch 402.

The switch 402 switches without converting an optical signal into an electric signal. The switch 402 includes a standby switch (restoration switch) 404 and working switches (working switches) 406a-b. Each of the clients 110a-b has its own active switch, but shares the standby switch 404. If the working fiber 104 can be used for signal communication, the switch 402 uses the working switch 406b to cause communication between the client 110b and the working fiber 104. When the working fiber 104 cannot be used for signal communication, the switch 402 uses the protection switch 404 to cause communication between the client 110b and the protection fiber 106. Similarly, when the working fiber 204 can be used for signal communication, the switch 402 uses the working switch 406a to cause communication between the client 110a and the working fiber 204. If the working fiber 204 cannot be used for signal communication, the switch 402
Using the client 110a and the standby fiber 20
6 is performed. By providing the standby system switch 404 and the active system switches 406a-b separately,
Active switch 406a with failure even during service provision
-B maintenance becomes possible.

FIG. 6 illustrates an electrical switch 502 that can be used in place of the optical switch 402 in one embodiment of the present invention.
It is a block diagram of. Electrical switching (electrical s
witching), a low-cost and highly reliable switching process can be realized. In addition, since the electrical switching process converts an optical signal into an electrical signal, the performance of the signal can be easily monitored in an electrical state. further,
When a transponder that converts a signal into an electric signal is used, the electric switching process becomes easier. In the present embodiment, the OXC 102 includes an electric switch 502, a controller 210,
Optical-electrical (EO) modules 506a-b, 508a-
b, 510a-b, 512a-b, 514a-b, 51
6a-b and an optical performance monitoring monitor 504. The OXC 102 includes working fibers 104, 204,
Standby fiber 106, 206, WDM 114, 13
0, 214, 230 and clients 110a-b
And an appropriate transmission medium. Each component operates with the above-described configuration. The electric switch 502 includes an electric circuit 520 connected to the electric switch 522.

The optical performance monitor 504 monitors signals received from the clients 110a-b, the working fibers 104 and 204, and the protection fibers 106 and 206. The electro-optical (EO) modules 506a-b convert optical signals from the client 110a to electrical signals,
The electric signal from the electric circuit 520 is converted into an optical signal. Similarly, EOs 508a-b convert an optical signal from client 110b to an electrical signal and an electrical signal from electrical circuit 520 to an optical signal. The EOs 510a-b convert an optical signal from the standby fiber 206 into an electric signal, and convert an electric signal from the electric circuit 520 into an optical signal. EO51
2a-b, EO 514a-b, and EO 516a-b operate in the same manner, and convert the optical signals from the fibers 204, 106, and 204 into electrical signals, respectively.
The electrical signal from 0 is converted to an optical signal.

The electric circuit 520 includes EOs 510a-b, 5
Receive electrical signals from 12a-b, 514a-b, 516a-b. The electrical circuit 520 monitors the performance of the input electrical signal and reads or writes information using an overhead channel of the input signal. Electrical switch 522 receives an electrical signal from electrical circuit 520. The controller 210 determines whether a signal can be transmitted via the working fibers 104 and 204. Working fiber 1
If signal communication is possible via 04, 204, electrical switch 522 sends the signal to fibers 104, 204. When signal communication cannot be performed via the working fiber 104 or 204, the electric switch 522 performs communication using the corresponding protection fiber 106 or 206.

FIG. 7 is a block diagram of a network node of an optical ring 600 that can be used in one embodiment of the present invention. The optical ring 600 includes network nodes 200 and 604, which are connected by an optical transmission medium as shown in FIG.
606, 608 and clients 610a-b, 6
12a-b, 614, 616, 628, 110b. A span (span switching) or a ring switching process (ring switching) is performed. For example, if signal communication through the working fiber 620 is not possible,
The span switching process is performed so that signal communication through the standby fiber 622 is enabled. For example, when signal communication cannot be performed through the working fiber 620 and the protection fiber 622, the fibers 104, 624,
The ring switching process is performed so that the signal communication using 630 is performed. Specifically, the signal is switched away from the obstruction and transmitted around the opposite direction of the ring. Each of the network nodes 200, 604, and 606 includes an optical switching unit, and may further include an electrical switching unit. Nodes 200, 604, 606,
608 includes switches corresponding to each of the signals that need protection rather than self-healing. Network node 200 receives signals from clients 610a-b. The client 610a is a client with a high priority, and when signal communication is possible via the working fiber 620, a signal from the client 610a is communicated to the client 612a via the working fiber 620. The client 610b is a low priority client, and a signal from the client 610b is communicated to the client 612b via the standby fiber 622. When the signal communication via the working fiber 620 is not possible, the network node 200 suppresses the signal from the client 610b having a low priority (squelch
e), the signal from the client 610a is switched to the standby fiber 622, and signal communication with the client 612a is performed. The network node 200 suppresses the low-priority signal by inserting the alarm notification into the signal channel of the low-priority signal. Similarly, client 612a is a high priority client and client 612b is a low priority client.
The signals from clients 612a-b are each communicated in a manner similar to the signals from clients 610a-b.

Each of the network nodes 604 and 606 has a client 6 having its own protection and recovery function.
14,616. Since the switch of the node switches the signal arbitrarily before the signal is multiplexed, the switch can prevent the switching from the signal from the self-healing client. According to this configuration, the failure detection and recovery in the ring configuration can be realized without inconsistency with the existing protection switching mechanism. The client 614 determines whether signal communication via the working fiber 614 is possible. Working fiber 62
If 4 is available, the client 614 performs signal communication with the client 616 via the working fiber 624. When the working fiber 624 cannot be used, the client 614 performs signal communication with the client 616 via the protection fiber 626. The client 616 performs signal communication in the same manner as the client 614.

Network node 606 provides a switching function for client 628 that does not have its own protection and recovery functions. The network node 606 receives the signal from the client 628, and
It is determined whether or not signal communication via 0 and 104 is possible. If signal communication is possible via the working fibers 630 and 104, the network node 606 transmits a signal to the network node 608 via the working fiber 630. The network node 608 has no protection switching mechanism. Thereafter, the signal is communicated to the client 110b via the working fiber 104. If the signal cannot be transmitted via any of the working fibers 630 and 104, the network component 606 transmits the signal from the client 628 via the protection fiber 632 and the client via the protection fiber 106. 11
0b to the network component 608 that performs signal communication.

FIG. 8 is a block diagram of a network node of a two-ring system that can be used in one embodiment of the present invention. System 700 includes ring 702 and ring 7
04. As shown in FIG. 8, the ring 702 includes nodes 706, 708, 710, and 712.
These nodes are connected to the working fibers 714, 718, 72
2, 726 and standby fibers 716, 720, 724,
788. As shown in FIG. 8, the ring 704 includes nodes 730, 732, 734, and 736. These nodes are used as working fibers 738, 738.
42, 746, 750 and standby fibers 740, 74
4, 748, 752. As shown in FIG. 8, the multiplexing device 791 may transmit the multiplexed signal to the fiber. Further, as shown in FIG. 8, line signal regenerators 782, 784 and 786 may be connected to the nodes.
Ring 702 and ring 704 are connected to ring connection node 76.
At 0, they are connected by an optical path 780 connected by clients 770 and 775. The optical path 780 has two sub optical paths A 790 and B 795. The line signal regenerators 782, 784, and 786 may be used to separate the performance and operation management of the sub optical path A790 and the sub optical path B795. Working fiber 7
If the failure 22 occurs, the ring 702 rescues the sub optical path A 790 by switching the span. When the working fiber 722 and the protection fiber 724 are faulty, the ring 702 rescues the sub optical path A 790 by switching the ring. When the working fiber 746 or the working fiber 746 and the protection fiber 748 are faulty, the ring 704 performs span switching or ring switching, respectively. In the event of a node 760 failure, the system 700 requires another optical path between the nodes. In the case of a failure of the node 760, that is, the working fibers 722 and 746 and the protection fibers 724 and 748
If is a failure, the system 700 selects another optical path through the node 765.

FIG. 9 is a block diagram showing a performance monitoring monitor of the optical path 820 which can be used in one embodiment of the present invention. Optical path 820 is connected to network element 822-
846. Network component 822-8
Reference numeral 46 is used for evaluation of signal performance, and is used for communication of notification information on the status of the signal when the signal does not satisfy a predetermined limiting condition, that is, when there is a problem with the signal. Signal issues can be identified, for example, as bit errors, alarm indications, signal loss, frame loss, and the like. Evaluation monitor information
It can be defined by using the OXC optical monitoring channel (OSC). OSC can identify, for example, an alarm display signal (OMS-AIS) in an optical multiplexing unit, signal status information (OCH-STA) in an optical channel, input status information (OCH-INP) in an optical channel, and the like. In addition, the transponder (TDR) and the client can perform signal loss (LOS), frame loss (LOF),
It is possible to perform performance monitoring and monitoring processing such as signal deterioration (SD) and alarm display signal (AIS).

More specifically, the optical path 820 includes a transmission line terminating device (LTE-TX) 822 and a switch 82
4, 844, transponders 826, 842, transmission amplifiers (TA) 828, 836, optical amplifiers (OA) 830,
838, receiving amplifiers (RA) 832 and 840, a line signal regenerator 834, and a receiving line terminator (LT)
E-RX) 846. The switch 824 defines input status information of the optical channel overhead unit. Transponders 826, 842 define signal loss, frame loss, signal degradation or alarm notification signals. Transmit amplifiers 828, 836 and receive amplifiers 832, 8
Reference numeral 40 defines both the signal status information in the optical channel overhead unit and the alarm notification signal in the optical multiplexing unit. The optical amplifiers 830 and 838 define an alarm notification signal in the optical multiplexing unit. The line signal regenerator 834 defines signal status information in the optical channel overhead. Switch 844 defines the signal status in the optical channel overhead. Line termination device 846
Is the signal loss signal, frame loss signal, signal degradation signal,
And activate the alarm notification signal.

FIG. 10 is a block diagram showing an embodiment of the present invention.
FIG. 11 is a diagram illustrating a frame configuration 800 that uses an ONET signal for OSC channel communication. The frame configuration 800 is used when requesting protection switching, and when communicating signal status information such as alarm notification, bit error rate, signal loss, and failure detection information. The frame structure 800 includes a payload section 802 and a signal overhead section 8.
04. The payload section 802 is used for transmitting a control communication channel. Dedicated bytes 806a-n, 808a-n, 810a-n for each wavelength are used for transmission of the control communication channel. Hikari ring (mu
ltiple optical rings) in the common payload section 802
Can be used. In this embodiment, ring 1 uses dedicated bytes 806a-n, and ring 2 uses dedicated bytes 808a-n.
-N, and ring N uses dedicated bytes 810a-n. The use of control bytes allows for simple, fast and low cost optical path failure recovery.

FIG. 11 is a flowchart showing a method of restoring an optical path that can be used in the optical ring 600 of FIG. 7 according to an embodiment of the present invention. In the method, first in step 902, the originating client 110
b sends a signal to the source node 200. Step 9
At 04, the source node 200 transmits a signal to the working path 104. At step 906, the active path 104
Causes a failure that affects the signal. Step 908
Then, the node 608 determines whether there is a failure in the signal, and sends an alarm, for example, by inserting a defect notification into the overhead part of the signal. Node 608 is an OX containing an evaluation monitor
C is provided. The evaluation monitor provides alarm information such as signal loss and signal degradation. The node 608 also has a WDM. The WDM includes an evaluation monitor that provides signal loss information and signal deterioration information, and an OSC that inserts alarm information into a signal overhead. The node 608 sends alarm information to the destination node 606 via the working fiber 630.

In step 910, the destination node 606
Receives the alarm information. The destination node 606 includes an evaluation monitor that receives the alarm information. Destination node 60
Reference numeral 6 denotes a working fiber 10 via a working path 630.
4 sends warning information indicating that it cannot be used and requests signal retransmission. This request is transmitted to the source node 200.
In step 912, the source node 200 receives the request. The source node 200 includes a WDM 114 that receives the request from the active path 104. WD
M114 communicates the request to OXC102.

At step 914, the source node 200
OXC switch switches the optical path from the working path 104 to the protection path 106. The controller 210 of the OXC 102 receives the request, and the optical switch 212 communicates a signal to the WDM 130, and the WDM 130 communicates the signal to the standby path 106. Only the signal transmitted from the client 110b was switched to the standby path 106. Other signals, such as, for example, signals from a client having a self-healing function, have not been switched by the OXC 102. In step 916, the source node 200 transmits a signal to the protection path 106. In step 920, the signal is output from the node 608 and the protection path 6
32 to node 606. Step 922
Now, the destination client 628 receives the signal.

[0039]

According to the present invention, there is provided a technically advantageous effect that the method and system for restoring an optical path in a wavelength division multiplexing network can be improved. In particular, the switching module switches individual signals at the wavelength level, so that only the selected signal can be switched. By using this selective signal switching, by not switching only the signal from the client that has its own protection and failure recovery function,
Switchin on the signal from the client
g conflict) can be prevented. Furthermore, the switching module only needs to be installed in the required places,
Protection and disaster recovery resources can be saved. Furthermore, by adding or moving the switching module,
The protection of added network components and the ability to recover from a failure can be ensured, so that the optical network can be easily upgraded. Therefore, by using the selective signal switching, the present invention can efficiently and effectively execute the restoration of the optical path in the wavelength division multiplexing network.

Further, according to the present invention, there is a technically advantageous effect that a system configuration for restoring an optical path in a wavelength division multiplexing network can be improved. In particular, the switching module switches individual signals at the wavelength level. In order to improve the performance of this system,
Line regenerating equipment
And transponders can also be used. According to the present invention, a method for implementing a system (implementa
There is a technical effect that the improvement scheme can be improved.
The network components communicate fault detection information with each other to detect line faults, for example, using special wiring or a network device manager. Further, a dedicated control byte may be used to transmit the failure detection information. Further, according to the present invention, there is a technical effect that the device configuration can be improved. The switching module can realize a highly reliable configuration by providing independent switching units for the original path and the alternative path. Further, a transponder or an electric switch may be incorporated in the system in order to improve the system performance.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an intermediate (integer) usable in the optical network of FIG.
FIG. 3 is a block diagram of a (rmediate) network node.

FIG. 3 is a block diagram of an optical path cross-connect having a card shelf configuration according to an embodiment of the present invention.

FIG. 4 is a block diagram of a node with a transponder that can be used in the optical network of FIG. 1;

FIG. 5 is a block diagram of a switch that can be used in a network node similar to the network node of FIG.

FIG. 6 is a block diagram of an electrical switch according to an embodiment of the present invention that can be used in place of an optical switch.

FIG. 7 is a block diagram of an optical ring network node that can be used in the optical network of FIG.

FIG. 8 is a block diagram of a network node of a two-ring system that can be used in one embodiment of the present invention.

FIG. 9 is an explanatory diagram of an optical path performance monitoring method that can be used in an embodiment of the present invention.

FIG. 10 is an explanatory diagram illustrating a frame configuration for communication in a SONET system that executes a protection switching process according to an embodiment of the present invention.

FIG. 11 is a flowchart illustrating a method for restoring an optical path in an optical ring according to an embodiment of the present invention.

[Explanation of symbols]

101: Network Node, 102: Optical Cross Connect, 103: Network Node, 104: Working Fiber, 106: Standby Fiber, 110a-b: Client, 112a-b: Switch, 114, 116: Wavelength Division Multiplexer , 120 ... optical cross connect, 122
ab ... switch, 124a-b ... client, 13
0, 132: wavelength division multiplexer, 134, 136: client.

Continued on the front page (72) Inventor Shoichi Hanatani 75081, Texas, United States, Richardson, Suite 400, Campbell Road 801 e. Hitachi Telecom (USA) Incorporated (72) Inventor Hirohisa Sano 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (40)

[Claims] An apparatus for restoring an optical path of a wavelength division multiplexing network, comprising: a first signal for receiving a signal, multiplexing the received signal with a first signal group, and transmitting the multiplexed signal to a working path; A first multiplexing unit for generating a multiplexed signal, receiving the signal, multiplexing the received signal with a second signal group, and generating a second multiplexed signal for transmission to the backup path A second multiplexing unit, connected to the client, receiving a signal from the client, multiplexing the signal and transmitting the multiplexed signal to the first multiplexing unit for transmitting the signal to the working path; A path base switch for switching to the second multiplexing unit for multiplexing the signal and transmitting the multiplexed signal to the backup path independently of the first signal group when a failure occurs in the system path (Path
-based switch). 2. The signal according to claim 1, wherein the signal is a first signal, the first multiplexing unit is connected to a self-healing client without passing through a path-based switch, and a second signal from the self-healing client is provided. And multiplexes the second signal with the first signal as a part of a first signal group and transmits the multiplexed signal to the working path. 2. The network configuration device according to claim 1, wherein the first signal is switched to the second multiplexing unit without switching the second signal in response to the occurrence of the failure. 3. The network configuration device according to claim 1, wherein said path-based switch is an optical cross-connect switch. 4. The path-based switch and a performance monitor connected to the path-based switch.
switching module (switching modul)
The method according to claim 1, further comprising: e) wherein the performance monitoring monitor monitors a signal from the client and generates alarm notification information when the signal does not satisfy a predetermined condition. The network configuration device according to claim 1. 5. The first multiplexing unit includes a performance monitoring monitor that monitors a signal from the path base switch and generates alarm notification information when the signal does not satisfy a predetermined condition. The network configuration device according to claim 1, wherein: 6. The signal according to claim 1, wherein the first multiplexing unit generates the first multiplexed signal by multiplexing an optical supervisory signal for communicating the state of the signal with the signal. 2. The network configuration device according to 1. 7. The path-based switch is connected to the first multiplexing unit, and the first multiplexing unit multiplexes a signal from the client for signal multiplexing and transmission to the working path. A working switch for communicating with the second multiplexing unit, and a signal from the client to the second multiplexing unit for signal multiplexing and transmission to the protection system path. The network configuration device according to claim 1, further comprising a standby switch for communication. 8. A switching module comprising the path-based switch and an electro-optical converter, wherein the switching module converts an optical signal to an electric signal,
The electric signal is switched to one of the first multiplexing unit and the second multiplexing unit, and the electric signal after the switching is converted into an optical signal for multiplexing and transmission processing. The network configuration device according to claim 1. 9. A line signal regenerator connected to the second multiplexer and the path base switch.
The network configuration device according to claim 1, further comprising: or), wherein the line signal regenerator reproduces a signal communicated from the path base switch to the second multiplexing unit. 10. A signal connected to the first multiplexing unit and communicated from the path base switch to the first multiplexing unit for signal multiplexing and transmission processing to the working path. From the path base switch to the second multiplexing unit for signal multiplexing and transmission processing to the backup path by connecting to the first transponder that monitors The network configuration device according to claim 1, further comprising a second transponder that monitors a signal to be communicated. 11. The network of claim 1, further comprising a transponder connected to said path-based switch and said client for monitoring signals communicated from said client to said path-based switch. Component device. 12. The network configuration device according to claim 1, further comprising a hardware interface for connecting the path-based switch and the client. 13. The network configuration device according to claim 1, further comprising a network device management manager (element manager) for connecting the path-based switch and the client. 14. The control signal channel (cont)
The network configuration device according to claim 1, further comprising a payload including a rol communication channel. 15. The network configuration device according to claim 1, wherein said working path and said protection path are provided on a ring. 16. The network configuration device according to claim 1, wherein said working path is provided on a first ring, and said protection path is provided on a second ring. 17. In a wavelength division multiplexing network, the first signal is sent to a first node of the wavelength division multiplexing network for retransmitting the first signal to a second node of the wavelength division multiplexing network. A transmitting client; and a second signal of the wavelength division multiplexing network.
Transmitting said second signal to said first node of said wavelength division multiplexing network for retransmission to said node;
A self-healing client that performs protection switching on the second signal independently of the first signal, wherein the first node includes a path for the first signal. A wavelength division multiplexing network comprising a base switch, wherein the path base switch executes protection switching processing for the first signal independently of the second signal. 18. The wavelength division multiplexing network according to claim 17, wherein said path-based switch comprises an optical cross-connect switch. 19. A switching module comprising the path-based switch and a performance monitoring monitor connected to the path-based switch, wherein the performance monitoring monitor monitors a signal from the client, wherein the signal is The wavelength division multiplexing network according to claim 17, wherein alarm notification information is generated when a predetermined condition is not satisfied. 20. The wavelength of claim 17, further comprising a transponder connected to said path-based switch and said client for monitoring a signal communicated from said client to said path-based switch. Division multiplex network. 21. The wavelength division multiplexing network according to claim 17, further comprising a hardware interface for connecting said path-based switch and said client. 22. The wavelength division multiplexing network according to claim 17, further comprising a network device manager for connecting said path-based switch and said client. 23. The WDM network of claim 17, wherein said signal comprises a payload including a control communication channel. 24. A method for restoring an optical path in a wavelength division multiplexing network, comprising: receiving a first signal to be transmitted to a working path from a client; and transmitting a second signal to the working path. Is received from the self-healing client, and it is determined whether a failure has occurred in the working path. When it is determined that the failure has occurred, the first path is independent of the second signal. Is switched to a backup path, and the self-healing client is allowed to independently perform protection switching processing on the second signal. The first signal is multiplexed with a group of signals to be multiplexed. And transmitting the multiplexed signal to the backup path. 25. The method according to claim 24, wherein the switching process to the backup path includes a switching process by a path base switch. 26. The method according to claim 24, wherein the switching process to the backup path is performed by an optical cross-connect switch. 27. The apparatus according to claim 27, further comprising: a process of monitoring said first signal; and a process of generating alarm notification information when said first signal does not satisfy a predetermined condition. 25. The method according to 24. 28. A process for switching to the backup path, a process for converting the first signal from an optical signal to an electrical signal, a process for switching the electrical signal to the backup path, and a process after the switching process. Converting the electrical signal to an optical signal for multiplexing and transmission processing. 29. The apparatus according to claim 24, further comprising a process of reproducing said first signal on said standby path.
The method described in. 30. The method of claim 24, wherein said first signal comprises a payload including a control communication channel. 31. A process for judging the occurrence of a fault in the working path includes: a process of judging the occurrence of a fault in the working path using a first node in the wavelength division multiplexing network; The method of claim 24, comprising communicating. 32. The switching processing to the protection path, wherein the first signal from the working path provided on the first ring is switched to the protection path provided on the second ring. The method of claim 24, comprising processing. 33. A method for restoring an optical path in a wavelength division multiplexing network, comprising the steps of: receiving a signal from a client; and performing multiplexing processing and transmission processing to the working path in accordance with the state of the working path. Using a path-based switch to arbitrarily switch the signal to one of a first multiplexing unit and a second multiplexing unit that performs a multiplexing process and a transmission process to a backup path; The signal is multiplexed with a first signal group in response to the signal received by the multiplexing unit, and a first multiplexed signal to be transmitted to the working path is generated. Multiplexing the signal with a second group of signals in response to receiving a signal to generate a second combined signal to be transmitted to the protection path. 34. The signal is a first signal, and a process of receiving a second signal from a self-healing client and a process of switching protection of the second signal to the self-healing client are performed independently. 34. The method of claim 33, further comprising the step of performing. 35. The method according to claim 33, wherein said switching process is performed by an optical cross-connect switch. 36. The method of claim 33, further comprising: monitoring the signal; and generating alarm notification information if the signal does not meet a predetermined condition. 37. The apparatus according to claim 33, further comprising a process of reproducing said first signal on said standby path.
The method described in. 38. The method according to claim 33, wherein said first signal comprises a payload including a control communication channel. 39. The switching process includes a process of switching the first signal from the working path provided on a first ring to the protection path provided on a second ring. 34. The method of claim 33, wherein the method comprises: 40. A network configuration device for restoring an optical path failure in a wavelength division multiplexing network, comprising: a signal receiving unit for multiplexing the received signal with a first signal group and transmitting the multiplexed signal to a working optical path; A first multiplexing unit that generates one multiplexed signal; a second multiplexing unit that receives the signal, multiplexes the signal with a second signal group, and transmits the multiplexed signal to a first standby optical path. A second multiplexing unit for generating a multiplexed signal; a third multiplexing unit for receiving the signal, multiplexing the signal with a third signal group, and transmitting the multiplexed signal to a second standby optical path A third multiplexing unit that generates a signal; and a path-based switch, wherein the path-based switch receives a signal from a client and multiplexes the signal into the first multiplex. And then multiplexes it and sends it to the working optical path. When a failure occurs in the working optical path, the signal is switched to the second multiplexing unit independently of the first signal group, where the signal is multiplexed and the first protection path is switched. When a failure occurs in the working optical path and the first protection optical path, the signal is switched to the third multiplexing unit independently of the first signal group. And a multiplexing process for transmitting the multiplexed signal to the second standby optical path.