JP2013243559A - Optical transmission node and path switching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical transmission node which can shorten a fault recovery time with regard to an advance reserved wavelength restoration function.SOLUTION: An optical transmission system configured with a plurality of optical transmission nodes includes a standby optical path switchover management table in which are set route information indicating information on the optical transmission nodes which allow a plurality of standby optical paths to be set for a currently used optical path and through which the plurality of standby optical paths run, information indicating whether the paths can be switched, and switchover priority in which order the standby optical paths are switched over when a fault occurs in the currently used optical path. The normality of the plurality of standby optical paths is confirmed, and the switchover priority in which order the standby optical paths are switched over is determined on the basis of the confirmation result.

Description

  The present invention relates to an optical transmission node constituting an optical transmission system having a working optical path and a backup optical path.

  In recent years, as a failure recovery method to realize high reliability and fault tolerance improvement of core / metro networks using WDM (Wavelength Division Multiplexing) transmission, different applications require different reliability and communication interruption times. A plurality of failure recovery methods have been studied (for example, see Non-Patent Document 1 below).

  Specifically, optical add / drop multiplexing (ROADM) and optical cross connect (OXC) that perform path switching processing without converting optical signals into electrical signals are multi-way By doing so, the topology shape of the network becomes a multi-ring / mesh from a simple topology such as a single ring, and it is possible to construct a highly reliable network that can take a large number of redundant paths. In addition, by applying a wavelength select switch (WSS) to these transmission devices, it is possible to set an optical path at an arbitrary wavelength in an arbitrary path without on-site work, and at the time of an optical path failure. A wavelength restoration function for establishing and switching a new normal optical path can be provided. There are two possible wavelength restoration functions: “wavelength restoration function without prior reservation” and “prior reservation wavelength restoration function”.

  The “wavelength restoration function without advance reservation” calculates a detour path after specifying a fault location in the optical path when a fault occurs in the working optical path, and switches to the detour path by signaling or the like. Compared with the 1 + 1 protection in which a protection optical path is set in advance for the working optical path and the working optical path is switched to the protection optical path when a failure occurs, the wavelength restoration function without prior reservation uses the bandwidth utilization efficiency. However, there is a problem that the failure recovery time becomes longer due to the route calculation considering wavelength continuity and transmission path characteristics.

  "Preliminary reserved wavelength restoration function" registers the protection path attributes (used wavelength, detour route, etc.) and switching order in advance for the working optical path in the transmission equipment at the working optical path start point, and causes a failure. In this method, a backup optical path is established through a detour route registered at times, and the working optical path is switched. Since up to X protection path attributes can be registered for the working optical path, it is possible to recover the maximum (X−1) serious failure. In addition, the pre-reserved wavelength restoration function performs signaling after detecting a failure in the working optical path, and sets up the protection optical path, so that the protection resources can be shared by multiple working optical paths, and valuable wavelength resources are effectively used. It can be used. In addition, when a spare resource is shared by a disjoint working optical path, a single failure can be guaranteed with high reliability.

The Institute of Electronics, Information and Communication Engineers GMPLS recovery and Extra LSP service using spare bandwidth (PN2003 25-34, p.41-46)

  However, in the above-mentioned conventional “pre-reserved wavelength restoration function”, since the main signal is not passed through the pre-registered spare optical path, the normality of the path of the spare optical path registered at the time of switching cannot be confirmed. When a path failure occurs, a procedure such as signaling is used, and the optical switch setting of the transmission apparatus on the backup optical path and the setting of the client accommodating unit at the optical path end point are performed to determine whether the quality can be used for the first time. In addition, when the wavelengths used in the working optical path and the backup optical path are different, it is necessary to change the wavelength. For this reason, there is a problem that the failure recovery time may increase significantly.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an optical transmission node capable of shortening the failure recovery time for the advance reservation wavelength restoration function.

  In order to solve the above-described problems and achieve the object, the present invention provides the optical transmission capable of setting a plurality of backup optical paths for the working optical path in an optical transmission system including a plurality of optical transmission nodes. Switching priority for switching between the plurality of backup optical paths, the path information indicating information of the optical transmission node that is passed through, the information indicating whether switching is possible, and the failure of the working optical path A backup optical path switching management table in which the priority is set, and confirms the normality of the plurality of backup optical paths, and determines the switching priority of the backup optical paths based on the confirmation result. Features.

  According to the present invention, there is an effect that the failure recovery time can be shortened for the advance reserved wavelength restoration function.

FIG. 1 is a diagram showing an arrangement of optical transmission nodes, a working optical path, and a backup optical path. FIG. 2 is a diagram illustrating a configuration example of an optical transmission node. FIG. 3 is a diagram illustrating a configuration example of an optical transmission system. FIG. 4 is a flowchart showing a procedure for setting path information of a plurality of backup optical paths for the working optical path and the working optical path. FIG. 5 is a diagram illustrating a working optical path and a backup optical path in the optical transmission system. FIG. 6 is a diagram showing a backup optical path switching management table. FIG. 7 is a diagram illustrating a normality confirmation operation of the backup optical path using the OSC light in the optical transmission node. FIG. 8 is a diagram showing the format of the control message. FIG. 9 is a flowchart showing the update processing of the protection optical path switching management table in the optical transmission node at the working optical path end point. FIG. 10 is a flowchart showing a failure recovery procedure when a switching trigger is detected at the optical transmission node at the working optical path endpoint. FIG. 11 is a diagram illustrating a state in which the switching priority order of the backup optical path is changed. FIG. 12 is a diagram illustrating a state in which the switching priority order of the backup optical path is changed.

  Embodiments of an optical transmission node according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
First, a problem in the conventional “pre-reserved wavelength restoration function” will be briefly described. FIG. 1 is a diagram showing an arrangement of optical transmission nodes, a working optical path, and a backup optical path. With respect to the working optical path having the optical transmission nodes 105 and 108 as the end point nodes, the optical transmission node 105 which is the starting point node of the working optical path registers two backup optical paths 1 and 2. The backup optical path 1 is routed through the optical transmission node 101, the optical transmission node 102, the optical transmission node 103, and the optical transmission node 104, and the backup optical path 2 is the optical transmission node 109, the optical transmission node 110, the optical transmission node 111, The optical transmission node 112 is a route. Here, it is assumed that the switching order when the working optical path fails is backup optical path 1 and backup optical path 2. When failure # 1 and failure # 2 occur simultaneously in this state, the following operation is performed.
(1) The optical transmission node 105 detects failure # 1 in the working optical path.
(2) The optical transmission node 105 performs signaling on the route of the backup optical path 1 in accordance with the switching order, and performs switch setting of the optical transmission node on the route.
(3) After the above setting, the normality of the switched optical path is confirmed.
(4) As a result of the normality confirmation, the main signal is non-routine due to failure # 2, and therefore the optical transmission node 105 performs signaling on the route of the backup optical path 2 in accordance with the registered switching order.
As described above, since the main signal is not passed through the pre-registered backup optical path, the failure recovery time greatly increases when the failures overlap.

  Next, an optical transmission node that can shorten the failure recovery time in this embodiment will be described. FIG. 2 is a diagram illustrating a configuration example of the optical transmission node according to the present embodiment. A specific functional configuration is shown. The optical transmission node 201 includes a node monitoring control unit 202, a plurality of client accommodation units 203-1 to 203-n, a plurality of 3R (Resharping, Retiming, Reamplifyung) units 204-1 to 204-n, and a MUX / DEMUX. Unit 205, OXC unit 206, a plurality of AMP units 207-1 to 207-n, and a plurality of OSC (Optical Supervisory Channel) units 208-1 to 208-n.

  The node monitoring control unit 202 includes a CPU 211 that controls operations in the optical transmission node 201, client accommodating units 203-1 to 203-n, 3R units 204-1 to 204-n, a MUX / DEMUX unit 205, an OXC unit 206, Switching state for managing the switching state of the device configuration management unit 212 that manages the configurations of the AMP units 207-1 to 207-n and the OSC units 208-1 to 208-n and the MUX / DEMUX unit 205 that is an optical switch A management unit 213, a fault management unit 214 that monitors alarm information and transmission path performance information detected by each of the client accommodation units 203-1 to 203-n and 3R units 204-1 to 204-n, and path information and alarms Attribute information and route information of the working optical path such as status, detour route registered for the working optical path, GMPLS (General a network management apparatus 215 connected to a network management apparatus 220 via a DCN (Data Communication Network) 221 and a path management unit 215 that manages the state of a signaling protocol such as a ized Multi-Protocol Label Switching (APS) protocol or an APS (Automatic Protection Switching) protocol. / F unit 216.

  The client accommodating units 203-1 to 203-n are connected to client devices such as IP routers and L2 switches. The client accommodating units 203-1 to 203-n accommodate clients such as Ethernet such as 10GbE (10 Gigabit Ethernet (registered trademark)) and GbE (Gigabit Ethernet) and SONET / SDH (Synchronous Optical Network / Synchronous Digital Hierarchy) signals. It has a wavelength conversion function of mapping to an OTU (Optical Transport Unit) frame defined by ITU-T, converting it to a wavelength signal by electrical / optical conversion, and outputting it to a transmission line fiber (optical fiber link). On the contrary, the client accommodating units 203-1 to 203-n perform reverse conversion on the wavelength signal input from the transmission line fiber as described above. In addition, when it is not necessary to individually distinguish the client accommodation units 203-1 to 203-n, the client accommodation units 203 may be collectively referred to as a client accommodation unit 203.

  The 3R units 204-1 to 204-n temporarily convert an optical signal received from the transmission line fiber into an electrical signal (OTU frame), perform wavelength shaping and the like, convert the optical signal to an optical signal, and output the optical signal to the transmission line fiber. . Each of the client accommodating units 203-1 to 203-n and 3R units 204-1 to 204-n includes an error correction circuit for guaranteeing quality degradation of a transmission signal accompanying an increase in transmission distance, and performs error correction code processing. At the same time, OTN such as detection of cause alarms that cause major failures such as LOS (Loss Of Signal) and LOF (Loss Of Frame), OTU overhead, ODU (Optical Data Unit) overhead, TCM (Tandem Connection Monitoring) overhead, etc. Terminates various overheads specified, transmission quality monitoring using BIP-8 (Bit Interleaved Parity), fiber connectivity confirmation using TTI (Trail Trace Identifier), and various maintenance such as AIS (Alarm Indication Signal) signal Insert and detect signals. When there is no need to individually distinguish the 3R units 204-1 to 204-n, the 3R units 204-1 to 204-n may be referred to as the 3R unit 204 as a whole.

  The MUX / DEMUX unit 205 wavelength-multiplexes the wavelength signals received from the client accommodating units 203-1 to 203-n and the 3R units 204-1 to 204-n, and transmits them to the OXC unit 206 as WDM signals. The DEMUX unit 205 wavelength-separates the wavelength multiplexed signal received from the OXC unit 206, and transmits it as an OCh signal to the client accommodating units 203-1 to 203-n and the 3R units 204-1 to 204-n.

  The OXC unit 206 drops an arbitrary OCh signal from the wavelength multiplexed signals received from the AMP units 207-1 to 207-n corresponding to an arbitrary route (routes 250-1 to 250-n), and MUX / DEMUX. To the unit 205. Further, the OXC unit 206 adds the OCh signal received from the MUX / DEMUX unit 205 to the wavelength multiplexed signal of an arbitrary route and transmits it to the AMP units 207-1 to 207-n, and at the same time, the AMP of the arbitrary route. Through the wavelength multiplexed signals received from the units 207-1 to 207-n, transmit them to the AMP units 207-1 to 207-n on different routes.

  The AMP units 207-1 to 207-n amplify the wavelength multiplexed signals received from the OXC unit 206 and send them to the routes 250-1 to 250-n. In addition, the AMP units 207-1 to 207-n collectively amplify the wavelength multiplexed signals received from the respective routes 250-1 to 250-n and send them to the OXC unit 206. In addition, when it is not necessary to individually distinguish the AMP units 207-1 to 207-n, the AMP units 207-n may be collectively referred to as the AMP unit 207.

  The OSC units 208-1 to 208-n terminate the OSC which is a monitoring control channel for transferring alarm transfer information below the OCh layer, a control message from the network management device 220, a monitoring control message used for GMPLS signaling, and the like. To do. The OSC units 208-1 to 208-n are provided for each route, and transmit and receive the monitoring control message between adjacent optical transmission nodes. Note that when there is no need to individually distinguish the OSC units 208-1 to 208-n, the OSC units 208-1 may be referred to as the OSC unit 208 as a whole.

  Next, operations such as switching from the working optical path to the backup optical path, and monitoring of the backup optical path in the optical transmission system configured by the optical transmission node according to the present embodiment will be described. FIG. 3 is a diagram illustrating a configuration example of the optical transmission system according to the present embodiment. FIG. 4 is a flowchart showing a procedure for setting path information of a plurality of backup optical paths for the working optical path and the working optical path.

  In FIG. 3, the optical transmission nodes 301 to 309 have the same configuration as the optical transmission node 201 in FIG. The optical transmission nodes 301 to 309 are connected to each other via 12 optical fiber links 310 to 321 to constitute an optical transmission system. Although not shown in FIG. 3 in order to avoid complexity, optical transmission nodes connected by optical fiber links are connected by OSC light to transmit and receive monitoring control information in-band. Further, here, the optical transmission system is configured by nine optical transmission nodes 301 to 309 and twelve optical fiber links 310 to 321, but this is an example, and an arbitrary number of optical transmission nodes and optical fibers may be used as necessary. It can be configured with links.

  Here, the registration procedure of the working optical path between the desired optical transmission nodes and a plurality of detour paths (backup optical paths) for the working optical path will be described with reference to FIG.

  The network administrator inputs the attribute information of the working optical path to the network management apparatus 220 and sets the optical transmission node through which the working optical path passes. The active optical path attribute information input by the network administrator includes the optical path identifier, the node ID of the optical transmission node that is the start / end point of the optical path, the wavelength information to be used, and the relay light that is the path information of the optical path. There are a node ID of a transmission node, an identifier of each optical fiber link that passes through, and the like. Note that the route information of the working optical path can be automatically calculated by the network management device 220 based on the conditions input by the network administrator and the free wavelength status of the optical transmission system.

  The network management apparatus 220 transmits the optical path setting information to the optical transmission nodes 304, 305, and 306 on the optical path through the DCN 221 based on the input working optical path information. Based on the received optical path setting information, the optical transmission nodes 304, 305, and 306 perform settings of the client accommodation unit 203, the MUX / DEMUX unit 205, the OXC unit 206, and the AMP unit 207 in its own node. In addition, although the case where the setting information is notified from the network management apparatus 220 to each optical transmission node via the optical path has been described as the optical path setting, the present invention is not limited to this. For example, the network management device 220 can output optical path attribute information to the optical transmission node 304 at the optical path start point, and set each optical transmission node using a signaling protocol such as the GMPLS protocol. .

  In FIG. 3, the working optical path 324 uses the optical transmission nodes 304 and 306 as optical path endpoints, accommodates client signals of the client apparatuses 322 and 323 connected thereto, and uses the optical transmission node 305 as a relay node. Pass.

  A procedure for enabling the advance reservation wavelength restoration function will be described based on the flowchart of FIG. First, the network administrator designates a working optical path to be protected by the advance reservation wavelength restoration function to the network management apparatus 220 (step S401), and the number of backup optical paths for protecting the designated working optical path. Is input (step S402). The pre-reserved wavelength restoration function can register up to X backup optical paths for the working optical path to multiple failures. For example, if A backup optical paths are registered, the maximum ( A-1) Recovery from a serious failure is possible.

  Next, the network administrator determines the attribute information of the backup optical path to be registered, that is, the wavelength and route information used in the backup optical path, and the switching priority. Here, the network administrator designates whether or not the network management device 220 automatically calculates the attribute information of the backup optical path (step S403). When automatic calculation is designated (step S403: Yes), the network management device 220 manages the connection relationship of the optical transmission nodes and the wavelength information used by each fiber link in the network, and based on these information Then, the spare optical path attribute information is automatically calculated and set (step S404).

  On the other hand, when automatic calculation is not designated (step S403: No), the network administrator manually sets and sets attribute information of each backup optical path (step S405).

  In the optical transmission node 304 which is the starting point of the working optical path, the switching state management unit 213 of the node monitoring control unit 202 holds the attribute information of the backup optical path input in step S404 or step S405 (step S406). .

  FIG. 5 is a diagram illustrating a working optical path and a backup optical path in the optical transmission system. For the working optical path 324, a backup optical path 324-1 with the optical transmission nodes 301, 302 and 303 as relay nodes and a backup optical path 324-2 with the optical transmission nodes 307, 308 and 309 as relay nodes are registered. It is a whole block diagram which shows schematically the optical transmission system at the time of doing.

  FIG. 6 is a diagram showing a backup optical path switching management table. 10 is a backup optical path switching management table related to the working optical path 324 held by the switching state management unit 213 of the node monitoring control unit 202 of the optical transmission node 304 that is the starting point of the working optical path 322; In the protection optical path switching management table, the path information of the protection optical path registered for a certain working optical path is recorded, and it is determined whether or not switching is possible when a working optical path failure occurs, and a plurality of protection optical paths. Is used to determine which backup optical path to switch to.

  In the protection optical path switching management table, a path identifier for identifying a working optical path to be protected generated for each working optical path, and route information of the working optical path, that is, each relay light through which the working optical path passes The number of hops indicating the number of transmission nodes, the pair of identifiers and link identifiers of each relay optical transmission node through which the working optical path passes, the free wavelength information on the route, the wavelength information used in the working optical path, the switching factor, The monitoring state indicating whether or not the failure monitoring is started and the information indicating that the path with the path identifier indicates the working optical path or the backup optical path are recorded.

  Further, in the protection optical path switching management table, as the attribute information of a plurality of protection optical paths registered for the working optical path, the path identifier and the route of each registered protection optical path are registered as in the case of the working optical path. Information, vacant wavelength information, used wavelength information, fault monitoring status, information indicating that the path with the path identifier indicates a working optical path or a backup optical path, and registration recorded in the backup optical path entry A switchability entry indicating whether or not the detour path of the reserved backup optical path has failed and can be switched, and a priority order entry indicating the switching priority of the registered backup optical path. It is recorded. As an example, the case where two spare optical paths are set has been described. However, the present invention is not limited to this, and three or more can be set.

  Returning to the flowchart of FIG. 4, after inputting the attribute information of the protection optical path for the working optical path in step S404 or step S405, the network administrator starts monitoring the failure status of each registered protection optical path. The optical transmission node 304 is notified (step S407). As a result, in the optical transmission node 304, the monitoring status entry of the backup optical path in the backup optical path switching management table shown in FIG. 6 becomes “YES”, and the failure monitoring on the path of the backup optical path is started. Further, the network manager notifies the optical transmission node 304 at the optical path start point of the start of the failure monitoring of the working optical path (step S408). Thereby, in the optical transmission node 304, the monitoring status entry of the working optical path in the protection optical path switching management table shown in FIG. 6 becomes “YES”, and the failure monitoring on the working optical path is started.

  Next, normality confirmation of the spare optical path using OSC light will be described. FIG. 7 is a diagram illustrating a normality confirmation operation of the backup optical path using the OSC light in the optical transmission node. Here, as an example, a description will be given using three optical transmission nodes, but it is assumed that all have the same configuration as the optical transmission node 201 shown in FIG. In FIG. 7, a working optical path is established between the optical transmission node 701 and the optical transmission node 703, and a route passing through the optical transmission node 702 is registered as a backup optical path. The main signal is not set between the node 702 and the optical transmission node 703.

  FIG. 8 is a diagram showing the format of the control message. The control message includes a path identifier field that describes the identifier of the protection optical path to be monitored, a path abnormality field that is updated when there is an abnormality in the optical transmission node on the protection path, and path information that indicates the path information of the protection optical path. And a vacant wavelength information field describing vacant wavelength information of each transmission line fiber of the backup optical path.

  The optical transmission node 701 and the optical transmission node 703 at the standby optical path endpoints are separately communicating with the main signal on the working optical path, and control messages of the format shown in FIG. Are transmitted at regular intervals, and information in the protection optical path switching management table is updated. The optical transmission node 702 on the backup optical path route refers to the route information in the control message and transfers the control message to the next hop. The optical transmission node 701 and the optical transmission node 703 at the backup optical path end point check whether or not the control message is received within a certain period, and check the continuity of the optical fiber link on the path of the backup optical path.

  The optical transmission node 702 on the backup optical path route that has received the control message assigns the wavelength resource used in the optical fiber link on the backup optical path route to the control message and transfers it. As a result, the optical transmission node 701 and the optical transmission node 703 at the backup optical path end point can acquire vacant wavelength information on the backup optical path.

  The optical transmission node 702 on the backup optical path route confirms the normality of the OXC unit 206 that is controlled when setting the backup optical path and the node monitoring control unit for abnormality, and assigns and transfers the path abnormality field in the control message. To do.

  FIG. 9 is a flowchart showing the update processing of the protection optical path switching management table in the optical transmission node at the working optical path end point. The optical transmission node at the working optical path endpoint refers to the backup optical path switching management table and checks whether or not a control message has been received within a certain period for the backup optical path whose monitoring status entry is YES ( Step S901).

  If the control message is not received within a certain period (step S901: No), the optical transmission node at the working optical path end point assumes that a failure has occurred in the fiber on the path of the protection optical path, and the corresponding protection optical path. Is set to “No”, and is excluded from switching targets (step S902). When the control message is received within a certain period (step S901: Yes), the optical transmission node at the working optical path end point refers to the path abnormality field in the reception control message, and the optical transmission node on the path of the backup optical path The state is checked (step S903).

  When the path abnormality field in the reception control message is “1” (step S903: Yes), the optical transmission node at the working optical path end point has various resources of the optical transmission node on the path of the backup optical path, for example, OXC. The unit 206 and the node monitoring control unit 202 are considered to be in an abnormal state, and the switchable / non-switchable entry of the corresponding protection optical path is set to “No” and excluded from the switching target (step S902).

  If the path abnormality field in the reception control message is “0” (step S903: No), the optical transmission node at the working optical path end point assumes that the path of the backup optical path is normal, and then performs reception control. With reference to the empty wavelength field of the message, the empty wavelength information of the optical fiber link on each path in the backup optical path monitoring table is updated (step S904).

  Next, if the optical transmission node at the working optical path endpoint is not equipped with the 3R unit 204 in the relay optical transmission node, it is necessary to consider the continuity of the wavelength. It is confirmed whether there are continuous free wavelengths (step S905). When there is no continuous free wavelength (step S905: No), the optical transmission node at the working optical path end point is regarded as non-switchable, and the switchable / non-switchable entry of the corresponding protection optical path is set to “No” and excluded from the switching target. (Step S902).

  If there are continuous free wavelengths on the path of the backup optical path (step S905: Yes), the optical transmission node at the working optical path endpoint determines whether or not the wavelength described in the used wavelength of the backup optical path is a free wavelength. Is confirmed (step S906). If the wavelength described in the used wavelength of the corresponding protection optical path is not an unused wavelength (step S906: No), the optical transmission node at the working optical path end point selects the wavelength to be used from the consecutive unused wavelengths, and uses the wavelength entry. Is updated (step S907).

  Then, the optical transmission node at the working optical path end point updates the used wavelength entry (step S907), and if the wavelength described in the used wavelength of the corresponding spare optical path is an empty wavelength (step S906: Yes), and the corresponding spare After the optical path switching enable / disable entry is set to “No” and excluded from switching targets (step S902), the switching priority of the backup optical path is determined (step S908).

  As a method for determining the switching order, parameters that affect the switching time, for example, the number of hops of the backup optical path and each hop, whether the OTS / OMS section has started up normally, are wavelengths of two or more waves, or currently used It is determined based on whether the wavelength is the same as that of the optical path and wavelength change control is not required at the time of switching. A procedure for registering a method for determining the switching order is provided, and the network administrator makes settings for all the optical transmission nodes in the network, and the optical transmission nodes determine the switching order according to the setting contents.

  Next, the failure recovery procedure when a failure occurs in the working optical path will be described. FIG. 10 is a flowchart showing a failure recovery procedure when a switching trigger is detected at the optical transmission node at the working optical path endpoint.

  For detection of the switching trigger, when OTN (Optical Transport Network) is applied to the optical transmission system, the optical transmission node detects a failure such as LOS / LOF detected by the client accommodation unit 203, and optical transmission at the optical path end point. Since the node terminates the ODU overhead between the client accommodating units 203 that terminate the working optical path, alarm detection in the end-to-end unit of the optical path and the BIP-8 field defined in the ODU overhead are used. The transmission signal quality deterioration can be detected by calculating the number of bit errors, and the optical path is switched in the end-to-end unit using these detections as a trigger. In addition, when a failure is detected at the repeater optical transmission node on the working optical path, a ripple alarm such as AIS (Alarm Indication Signal) or FDI (Forward Defect Indication) for notifying the failure to the optical path end point node is transferred. The optical path is switched in the end-to-end unit using these detections as a trigger.

  The optical transmission node at the working optical path end point that has detected the switching trigger calculates the protection time randomly from the determined maximum protection time, performs wait for the calculated protection time, and updates the protection optical path switching management table. (Step S1001). This is because the path of the backup optical path may be shared by a plurality of working optical paths, and this reduces the possibility of signaling failure when multiple failures occur.

  After the protection time elapses, the optical transmission node at the working optical path end point refers to the switchable / non-switchable entry of each backup optical path in the backup optical path switching management table, and determines whether or not switching is possible (step S1002). If there is no switchable backup optical path (step S1002: No), the optical transmission node at the working optical path endpoint ends the failure recovery procedure without performing the switching process. When there are a plurality of switchable backup optical paths (step S1002: Yes), the optical transmission node at the working optical path endpoint acquires attribute information of the backup optical path having the highest switching priority (step S1003), and performs the signaling procedure. This is executed and switched to the spare optical path (step S1004).

  If the standby path signaling fails due to an empty resource status such as a wavelength (step S1005: No), the optical transmission node at the working optical path end point indicates a switchable / non-switchable entry of the backup optical path in the backup optical path switching management table. “No” is set, and the process returns to step S1001. When the signaling is successful (step S1005: Yes), the optical transmission node at the working optical path endpoint monitors the normality of the path after switching (detection of a switching trigger) (step S1006). If not normal (step S1006: No), the optical transmission node at the working optical path endpoint returns to step S1001 without ending the failure recovery procedure. If it is normal (step S1006: Yes), the optical transmission node at the working optical path endpoint ends the failure recovery procedure.

  The effect in this Embodiment is demonstrated using FIG. 11 and FIG. FIG. 11 and FIG. 12 are diagrams showing how the protection optical path switching priority is changed. In FIG. 11, in an optical transmission system composed of twelve optical transmission nodes, an optical transmission node that is the starting point node of the active optical path with respect to the active optical path having the optical transmission node 105a and the optical transmission node 108a as endpoints. 105a registers two spare optical paths 1a and 2a. The backup optical path 1a is routed through the optical transmission node 101a, the optical transmission node 102a, the optical transmission node 103a, and the optical transmission node 104a. The backup optical path 2a is the optical transmission node 109a, the optical transmission node 110a, the optical transmission node 111a, The optical transmission node 112a is a route. Here, the switching order when the working optical path fails is the backup optical path 1a and the backup optical path 2a, and the optical transmission nodes 105a and 108a change the normality of each path to the OSC light by the procedure shown in FIG. It is in a state that has been confirmed using.

  In this state, when a fiber breakage failure of the optical fiber link occurs on the backup optical path 1a (between the optical transmission node 102a and the optical transmission node 103a), the optical transmission nodes 105a and 108a at the working optical path end points are According to the procedure shown in FIG. 9, the switching order of the backup optical path is changed in the order of backup optical path 2a and backup optical path 1a. As a result, in the optical transmission system, unnecessary signaling does not occur when the working optical path fails, and high-speed failure recovery is possible.

  In FIG. 12, in an optical transmission system composed of twelve optical transmission nodes, an optical transmission node that is the starting point node of the active optical path with respect to the active optical path having the optical transmission node 105b and the optical transmission node 108b as endpoints. Reference numeral 105b registers two spare optical paths 1b and 2b. The backup optical path 1b is routed through the optical transmission node 101b, the optical transmission node 102b, the optical transmission node 103b, and the optical transmission node 104b. The backup optical path 2b is the optical transmission node 109b, the optical transmission node 110b, the optical transmission node 111b, The optical transmission node 112b is a route. Here, the switching order when the working optical path fails is the backup optical path 1b and the backup optical path 2b, and the optical transmission nodes 105b and 108b change the normality of each path to the OSC light by the procedure shown in FIG. It is in a state that has been confirmed using. In FIG. 12, it is assumed that the wavelength used in the backup optical path 1b and the backup optical path 2b at the time of switching is the same as the wavelength λa of the working optical path.

  In this state, when the working optical path having the wavelength λa with the optical transmission node 101b and the optical transmission node 104b as the end points is set, the optical transmission nodes 105b and 108b at the working optical path end points are set in standby by the procedure shown in FIG. The wavelength used in the optical path 1b is changed to a wavelength λb different from the wavelength λa. Also, the switching order is changed from the working optical path to the standby optical path 2b and the standby optical path 1b that do not require wavelength change. Thereby, in the optical transmission system, when the working optical path fails, it is possible to switch to the backup optical path 2b that does not require the wavelength change, so that the failure can be recovered at high speed.

  As described above, according to the present embodiment, in the optical transmission system including a plurality of optical transmission nodes, the optical transmission node that is the starting point of the active optical path is a plurality of optical paths set for the active optical path. For the protection optical path, the order of the protection optical path to be preferentially switched when a failure occurs in the active optical path is set, and in-band control messages using OSC light are transmitted and received during communication on the active optical path. Thus, the normality of each backup optical path is confirmed, and the switching priority of each backup optical path is determined and changed based on the confirmation result. As a result, the switching priority of the backup optical path in which no failure has occurred can be raised, and the switching priority of the backup optical path having the same wavelength as that of the working optical path can be raised. Failure recovery time when a failure occurs can be shortened.

  As described above, the optical transmission node according to the present invention is useful when an optical transmission system is configured using a plurality of optical transmission nodes, and in particular, a plurality of spare opticals with respect to the working optical path in the optical transmission system. Suitable when the path can be set.

101-112, 101a-112a, 101b-112b, 201, 301-309, 701-703 Optical transmission node 202 Node monitoring control unit 203-1 to 203-n Client accommodation unit 204-1 to 204-n 3R unit 205 MUX / DEMUX unit 206 OXC unit 207-1 to 207-n AMP unit 208-1 to 208-n OSC unit 211 CPU
212 Device configuration management unit 213 Switching state management unit 214 Failure management unit 215 Path management unit 216 Network I / F unit 220 Network management device 221 DCN
310-321 optical fiber link

Claims (10)

In the optical transmission system composed of a plurality of optical transmission nodes, the optical transmission node capable of setting a plurality of backup optical paths for the working optical path,
For the plurality of backup optical paths, route information indicating information of optical transmission nodes through which the information is routed, information indicating whether switching is possible, and switching priority to be switched preferentially when a failure occurs in the working optical path are set. Standby optical path switching management table,
Confirming the normality of the plurality of backup optical paths, and determining the switching priority of the backup optical paths based on the confirmation result;
An optical transmission node characterized by that. The normality of the backup optical path is confirmed by transmitting and receiving an in-band control message using OSC light during communication by the main signal in the working optical path.
The optical transmission node according to claim 1. As a result of confirming the normality, for the backup optical path in which a path abnormality is detected, set in the backup optical path switching management table to be non-switchable.
The optical transmission node according to claim 1, wherein the optical transmission node is an optical transmission node. As a result of confirming the normality, a backup optical path that does not have a continuous free wavelength band in the path is set to be non-switchable in the backup optical path switching management table.
The optical transmission node according to claim 1, wherein the optical transmission node is an optical transmission node. In the backup optical path switching management table, when the wavelength used in each backup optical path is set,
As a result of confirming the normality, for the backup optical path in which the same wavelength as the working optical path is used in another optical path, the wavelength to be used is selected from the continuous free wavelengths, and the backup optical path switching management table is used. Change the wavelength information,
The optical transmission node according to claim 4. In an optical transmission system composed of a plurality of optical transmission nodes, a path switching method in the optical transmission node capable of setting a plurality of backup optical paths for a working optical path,
The optical transmission node switches, with respect to the plurality of backup optical paths, route information indicating information of optical transmission nodes through which the optical transmission node passes, information indicating whether switching is possible, and switching to be preferentially performed when a failure occurs in the working optical path When a backup optical path switching management table in which priority is set is provided,
A normality confirmation step for confirming normality of the plurality of backup optical paths during communication using the working optical path;
A switching priority determination step for determining a switching priority of the backup optical path based on a confirmation result in the normality confirmation step;
A path switching method comprising: In the normality confirmation step, the normality of the backup optical path is confirmed by transmitting and receiving an in-band control message using OSC light during communication by the main signal in the working optical path.
The route switching method according to claim 6. In the switching priority determination step, as a result of confirming the normality, the backup optical path in which a path abnormality is detected is set to be non-switchable in the backup optical path switching management table.
The route switching method according to claim 6 or 7, wherein In the switching priority determination step, as a result of confirming the normality, a backup optical path having no continuous free wavelength band in the path is set to be non-switchable in the backup optical path switching management table.
The route switching method according to claim 6 or 7, wherein In the backup optical path switching management table, when the wavelength used in each backup optical path is set,
In the switching priority determination step, as a result of confirming the normality, for the backup optical path in which the same wavelength as the working optical path is used in another optical path, a wavelength to be used is selected from continuous free wavelengths, Change the information on the wavelength used in the protection optical path switching management table.
The route switching method according to claim 9.

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