JP2012160938A - Path switching control system and path switching control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a path switching control system capable of achieving cost reduction and downsizing.SOLUTION: The path switching control system includes at least: a redundant path composed of an active path and a standby path; a transmission device for regenerative repeating provided at the redundant path; an optical reception level monitor provided at each of the redundant paths; and a warning reception monitor provided in common to the redundant path.

Description

  The present invention relates to a path switching control system and a path switching control method for an optical transmission system that transmits optical signals.

  2. Description of the Related Art In recent years, the development of multiplexing light of different wavelengths and simultaneously transmitting a plurality of signals using a single optical fiber is rapidly progressing as a central technology for optical communication.

  Redundant designs are used in critical systems where the loss of life or property or a significant impact on corporate activity when a system loses its original function due to a failure.

  Redundancy means that a spare device is placed and operated as a backup from normal so that the entire system functions can be maintained even after a failure occurs in the event of a failure in a part of the system. Say.

  Therefore, in the optical transmission system in the system as described above, when a failure occurs in one path (working path), a plurality of (for example, two) lights between nodes are switched so as to be switched to the other path (backup path). Connected with fiber cable.

  Patent Document 1 discloses a control circuit that selects from two signal lines based on a physical optical signal level lowering state and an AIS (alarm indication signal) signal when a failure occurs in one path. Is described. More specifically, the two signal lines are switched by detecting the state of each path from the physical optical signal level lowering state and the AIS signal.

JP-A-5-268196

  When switching to a backup path, the optical reception level in the switching destination path needs to be high. For this reason, in Patent Document 1, in order to grasp the state of the switching destination path, it is necessary to provide an AIS signal monitor for each of the working path and the backup path, which causes a problem in terms of cost and size.

  A path switching control system according to the present invention includes a redundant path composed of at least a working path and a backup path, a regenerative repeater transmission apparatus provided in the redundant path, and an optical reception level monitor provided in each of the redundant paths. And an alarm reception monitor provided in common with the redundant path.

  The path switching control system in the present invention can realize cost reduction and size reduction.

It is a block diagram which shows the path switching control system at the time of failure occurrence. It is a block diagram which shows the path switching control system at the time of failure recovery. It is a flowchart which shows the procedure of the path switching control method at the time of failure occurrence. It is a flowchart which shows the procedure of the path switching control method at the time of failure recovery. It is a block diagram which shows the path | pass switching control system which transmits / receives from both directions.

  Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. However, the preferred embodiments described below are technically preferable for carrying out the present invention, but the scope of the invention is not limited to the following.

  [First Embodiment] Next, this embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a path switching control system 1 in the present embodiment.

  [Description of Configuration] As shown in FIG. 1, the path switching control system 1 according to the present embodiment includes an active path 2, a backup path 3, and regenerative repeater optical transmission devices 4a, 4b, 4c, 4a ', 4b'. 4c ′ and wavelength transmission / reception end optical transmission devices 5 and 5 ′. The wavelength transmission / reception end optical transmission device generally indicates a line redundant transponder. In this embodiment, two paths of the working path 2 and the backup path 3 can be operated by one line redundant transponder. .

  In the path switching control system 1, the working path 2 and the backup path 3 constitute a redundant path, and are optically connected between the wavelength receiving end optical transmission apparatuses 5 and 5 '. The redundant path is a configuration having an automatic path switching function that can switch to the other path (backup path 3) when a failure occurs in one path (working path 2).

  At least one regenerative repeater optical transmission device 4 is connected to each of the working path 2 and the backup path 3. In this embodiment, as shown in FIG. 1, three regenerative repeater optical transmission devices 4a, 4b, 4c, 4a ′, 4b ′, and 4c ′ are provided in the working path 2 and the backup path 3 from upstream to downstream, respectively. Provided.

  As shown by x in FIG. 1, when a failure occurs in a predetermined location (in this case, between 4a and 4b) of the working path 2, the downstream regenerative repeater optical transmission device 4b adjacent to the failure occurrence location Detect signal failure. Here, the failure between the regenerative repeater optical transmission devices 4a and 4b is not only a failure that makes it impossible to physically receive light due to removal of the optical transmission path connecting the two, as well as regenerative repeater optical transmission. It includes a failure in which a signal frame included in light transmitted due to a signal transmission function failure of the device 4a is abnormal.

  Then, the regenerative repeater optical transmission device 4b issues an optical input signal failure alarm and transmits an AIS signal, which is transmission failure alert information, to the downstream regenerative repeater optical transmission device 4c. The regenerative repeater optical transmission device 4c that has received the AIS signal transfers the AIS signal to the downstream wavelength path transmission / reception end optical transmission device 5. At this time, the regenerative repeater optical transmission device 4c does not process the AIS signal, and transfers the received AIS signal to the wavelength path transmission / reception end optical transmission device 5 as it is.

  More specifically, when the optical transmission device 4 for regenerative repeater detects an optical input signal failure due to the occurrence of a failure on the upstream side, the regeneration that connects the created AIS signal or the received AIS signal to the downstream side. The data is transmitted to the relay optical transmission device 4 or the wavelength path transmission / reception end optical transmission device 5.

  The wavelength path transmission / reception end optical transmission device 5 includes an O / E converter 6 and an optical switch 7. The O / E converter 6 has an alarm reception monitor 8 and further has a function of converting an optical signal into an electric signal. The optical switch 7 is provided with optical reception level monitors 9 and 9 ′ and has a function of switching between the working path 2 and the backup path 3. When the working path 2 and the protection path 3 are connected to the wavelength path transmission / reception end optical transmission device 5, they are connected to the alarm reception monitor 8 of the O / E converter 6 via the optical reception level monitors 9 and 9 ′ of the optical switch 7. ing.

  Optical reception level monitors 9 and 9 'are provided for the working bus 2 and the backup path 3, respectively, and always monitor the optical reception levels of both. On the other hand, the alarm reception monitor 8 is commonly connected to both the working path 2 and the protection path 3, and monitors the AIS signal transmitted from both. That is, when the alarm reception monitor 8 receives the AIS signal, it cannot determine which of the active path 2 and the backup path 3 is transmitted.

  The wavelength path transmission / reception end optical transmission device 5 ′ receives the AIS signal transferred from the regenerative repeater optical transmission device 4 by the alarm reception monitor 8 included in the O / E converter 6.

  When the O / E converter 6 recognizes the AIS signal in the alarm reception monitor 8, the optical switch 7 switches from the currently operating path (active path 2) to the other path (backup path 3). However, when switching the path, if the switching destination path (backup path 3) in the optical reception level monitor 9 does not reach the optical input level (normal value) during normal operation, that is, if the optical level is low. Do not switch.

  More specifically, when the wavelength path transmission / reception end optical transmission device 5 ′ is transferred from the regenerative repeater optical transmission device 4 and receives the AIS signal by the alarm reception monitor 8, the optical input level of the backup path 3 in the optical reception level monitor 9 is detected. Perform analysis. If the optical level value of the protection path 3 detected by the optical reception level monitor 9 ′ is not problematic in line operation, the optical switch 7 automatically switches the path from the working path 2 to the protection path 3. However, if the optical input level of the backup path 3 does not reach the optical input level during normal operation, it is determined that a failure has occurred in the backup path 3 and the path is not switched.

  The regenerative repeater optical transmission device 4 that has detected the AIS signal transfers the AIS signal to the wavelength path transmission / reception end optical transmission device 5 ′ for a certain period of time. The regenerative repeater optical transmission device 4 continues to transfer the AIS signal for a certain period of time, and then performs an optical output shutdown to stop the optical signal output from the optical signal output unit of the regenerative repeater optical transmission device 4.

  The fixed time is a time for the wavelength transmitting / receiving end optical transmission device 5 ′ to complete the switching from the working path 2 to the protection path 3. That is, after receiving the AIS signal, the optical reception level monitor 9 recognizes that the optical input level of the backup path 3 is the optical level during normal operation, and the optical switch 7 switches from the working path 2 to the backup path 3. Is the time. Therefore, for example, if the wavelength path transmission / reception end optical transmission device 5 ′ has high performance and can perform the above path switching instantaneously, it is possible to shorten a certain time during which the AIS signal is transmitted.

  When the trigger for performing path switching is an AIS signal as in the above configuration, the time required for path switching is determined depending on the capability of the wavelength transmitting / receiving end optical transmission apparatus 5 ′. Therefore, the regenerative repeater optical transmission device 4b can reduce the speed of the optical output control using VOA (Variable Optical Attenuator) control or the like, and keep the optical level fluctuation speed within the allowable range of the output control of the optical amplifier. Can do. That is, the regenerative repeater optical transmission device 4b has no operational problem even if the optical output is shut down slowly.

  As shown in FIG. 2, when the transmission path failure of the working path 2 is recovered, the regenerative repeater optical transmission device 4b recognizes the cancellation of the optical input signal failure alarm and sends an AIS signal to the downstream regenerative repeater optical transmission device 4c. Transfer the release information.

  When the regenerative repeater optical transmission device 4 c detects the cancellation information of the transferred AIS signal, it transfers the cancellation information of the AIS signal to the wavelength path transmission / reception end optical transmission device 5. When the regenerative repeater optical transmission device 4c receives the release information of the AIS signal, it cancels the optical output shutdown and restarts the optical signal output during normal operation.

  When receiving the AIS signal release information from the regenerative repeater optical transmission device 4 c, the wavelength path transmission / reception end optical transmission device 5 ′ receives the information via the alarm reception monitor 8 included in the O / E converter 6. Then, the optical reception level monitor 9 included in the optical switch 7 in the wavelength path transmission / reception end optical transmission device 5 ′ recognizes that the optical reception level monitor value of the working path 2 is a normal value.

  When the wavelength path transmission / reception end optical transmission device 5 ′ recognizes the cancellation information of the AIS signal and the normality of the optical reception level monitor 9 of the working path 2, it automatically senses the restoration of the normal state of the transmission path in which the failure has occurred, The path is automatically restored from the protection path 3 to the working path 2 to return to the operation state before the transmission path failure.

  [Explanation of Operation] Next, with reference to FIG. 3, the regenerative repeater optical transmission device 4 and the wavelength path transmission / reception terminal when automatic path switching from the working path 2 to the protection path 3 is performed in a state where a transmission path failure has occurred. The operation of the optical transmission device 5 will be described.

  First, in S1, when a transmission path failure occurs in the working path 2, the downstream regenerative repeater optical transmission device 4 adjacent to the location of the failure detects an optical input signal failure. Next, the process proceeds to S2.

  Next, in S2, the regenerative repeater optical transmission apparatus 4 transfers an AIS signal, which is transmission failure alarm information, to the downstream wavelength path transmission / reception end optical transmission apparatus 5 for a certain period of time. Next, the process proceeds to S3.

  Next, in S 3, the wavelength path transmission / reception end optical transmission device 5 detects the AIS signal transferred from the upstream regenerative repeater optical transmission device 4 by the alarm reception monitor 8. Next, the process proceeds to S4.

  Next, in S4, when the wavelength path transmission / reception end optical transmission device 5 detects the AIS signal by the alarm reception monitor 8, the optical reception level monitor 9 recognizes whether the backup path 3 is at the optical input level during normal operation. The optical reception level monitor 9 always monitors the optical reception levels of the working path 2 and the protection path 3.

  On the other hand, if the backup path 3 has not reached the optical input level during normal operation, the process proceeds to S7 as NO. In S7, switching from the working path 2 to the protection path 3 is not performed.

  In S5, the optical switch 7 automatically performs path switching from the working path 2 to the protection path 3. Next, the process proceeds to S6.

  Next, in S6, the reproduction repeater optical transmission apparatus 4 ends the transmission of the AIS signal. Next, the process proceeds to S7.

  In step S7, the regenerative repeater optical transmission device 4 starts optical output shutdown. At this time, since switching of the path from the working path 2 to the protection path 3 has already been completed, the optical output shutdown speed does not affect the KeepAlive characteristic of the optical amplifier mounted in the regenerative repeater optical transmission apparatus 4. Can be done at a speed of

  Next, referring to FIG. 4, the regenerative repeater optical transmission device 4 and the wavelength path transmission / reception end optical transmission device 5 ′ when performing automatic path recovery from the protection path 3 to the working path 2 in the state when the transmission path failure is recovered. Will be described.

  First, in S11, when the transmission path failure of the working path 2 is restored, the downstream regenerative repeater optical transmission apparatus 4 adjacent to the restored location recognizes. Next, the process proceeds to S12.

  Next, in S12, the regenerative repeater optical transmission device 4 transfers the AIS cancellation information to the downstream wavelength path transmission / reception end optical transmission device 5 ′, starts the cancellation of the optical output shutdown, and the optical output level during normal operation. Return to. Next, the process proceeds to S13.

  In step S13, the wavelength path transmission / reception end optical transmission device 5 ′ recognizes the AIS cancellation information transferred from the upstream regenerative repeater optical transmission device 4. Next, the process proceeds to S14.

  Next, in S14, the optical reception level monitor 9 of the wavelength path transmission / reception end optical transmission device 5 'determines whether the optical input level of the working path 2 is in the normal operation state by releasing the optical output shutdown of the regenerative repeater optical transmission device 4b. recognize. If the optical input level of the working path 2 is the normal value, the process proceeds to S15 as YES.

  On the other hand, if the working path 2 has not reached the optical input level during normal operation, the process proceeds to S16 as NO. In S16, switching from the protection path 3 to the working path 2 is not performed.

  Next, in S15, the wavelength path transmitting / receiving end optical transmission device 5 ′ recognizes the failure recovery of the working path 2 where the failure has occurred, and automatically performs the path restoration that is the switching from the protection path 3 to the working path 2. Execute.

  [Explanation of Effects] Next, the effects of this embodiment will be described.

The path switching control system 1 according to the present embodiment monitors failure information generated by the working path 2 and the protection path 3 with a common alarm reception monitor 8. That is, the alarm reception monitor 8 is not provided in each of the working path 2 and the backup path 3. Therefore, when receiving the AIS signal, the alarm reception monitor 8 cannot determine whether a failure has occurred in the working path 2 or the backup path 3.

  In the present embodiment, the optical reception level monitors 9 and 9 'are provided for the working path 2 and the protection path 3, respectively, and always monitors whether the optical reception level is a normal value. Then, when the AIS signal is received from one of the paths, if the optical reception level is a normal value, the path is switched. That is, the path is switched so that the optical reception level is closer to the normal value.

  With the above configuration, when a failure occurs in one of the working path 2 and the protection path 3 and an AIS signal is transmitted, the alarm reception monitor 8 can receive an optical signal even if it cannot determine from which the AIS signal is transmitted. By selecting a path whose level is close to the normal value, a path switching system with high quality can be configured at low cost.

  That is, it is not necessary to provide the alarm reception monitor 8 for each of the working path 2 and the protection path 3, and it is sufficient to provide the alarm reception monitor 8 in common for the working path 2 and the protection path 3. Therefore, since the path switching control system 1 can be configured with one alarm reception monitor 8 for two paths, further cost reduction and downsizing can be realized.

  If a path switching is performed by recognizing only the AIS signal when a transmission path failure occurs, there are the following problems. Since there is one AIS monitor point, the transmission path state of the protection path 3 cannot be monitored, and the transmission path condition of the protection path 3 cannot be grasped. Therefore, when the protection path 3 also has a failure, there is a risk that the line will not be restored even if automatic path switching is performed. Further, even after the protection path 3 is switched, the recovery status of the working path 2 in which the failure has occurred cannot be monitored, so that automatic recovery cannot be performed.

  On the other hand, when only the optical reception level monitor 9 is recognized and path switching is performed, there are the following problems depending on the optical output shutdown speed of the regenerative repeater optical transmission device 4.

  When the optical output shutdown is early, the optical level fluctuation due to the optical output shutdown is rapid, so that the keep alive characteristic of the optical amplifier mounted on the optical transmission device 4 for regenerative repeating cannot be satisfied. Therefore, there is a possibility that the regenerative repeater optical transmission device 4 may cause an error to other surviving wavelengths that are multiplexed together with the wavelength that is detected and shut down.

  To explain in detail using a specific example, consider a case where, for example, the working path 2 transmits an optical signal obtained by multiplexing 40 channels of optical signals having different wavelengths (hereinafter referred to as “ch”). Here, when some kind of failure occurs in the working path 2 and the optical output for 39 ch is shut down, the multiplexed optical output level suddenly changes from 40 ch to 1 ch.

  However, when the optical output shuts down quickly, the optical amplifier of the regenerative repeater optical transmission device 4 provided downstream of the faulty point cannot cope with the speed, and the actual level of 40 ch is compared to the optical level signal of 1 ch. Make adjustments. As a result, the optical amplifier outputs excessive light, and an error occurs even for a 1ch optical signal not related to a failure. In other words, even if the optical signal can be switched to the backup path 3 for the 39 channels where the failure has occurred, the normal 1 ch optical signal remaining in the working path 2 is adversely affected.

  On the other hand, when the shutdown speed is slow, the level of the optical amplifier can be adjusted in accordance with the fluctuation of the light level. However, since the speed of falling to the light level threshold that is a path switching execution trigger is slow, path switching cannot be performed instantaneously, which affects network services in path switching.

  Therefore, the path switching system 1 in the present embodiment transmits an AIS signal when a failure occurs in the transmission line, and performs path switching while monitoring the quality of the backup path 3. Therefore, the optical output of the working path 2 can be dropped slowly, and signal quality in the network and automatic switching and automatic restoration functions can be realized.

  A detailed description will be given using a specific example as described above. The path switching control system 1 in this embodiment includes both an optical reception level monitor 9 and an AIS monitor for wavelength path reception end optical transmission. Therefore, even if a failure occurs in channels 1 to 39 of the 40-wave multiplexed signal in the working bus 2, if there is no problem with the optical input level of the backup path 3 using the AIS signal as a trigger, 39 channels of optical signals are reserved. Switch to pass 3.

  Here, the signal transmitted through the working path 2 fluctuates from 40 ch to 1 ch, but the optical amplifier of the regenerative repeater optical transmission device 4 can appropriately control the optical level for the optical signal for 1 ch. , Adjust the optical shutdown speed to gradually slow down.

  In other words, in the present embodiment, first, switching of the 39 ch optical signals in which a failure has occurred to the backup path 3 is performed by switching with the AIS signal. By switching to the protection path 3, the optical shutdown of the working path 2 can be slowly performed while maintaining the normal state of the optical signal for 39 channels. As a result, since the optical amplifier can appropriately control the optical level, the optical signal for 1ch in which no failure has occurred can operate normally with the working path 2 still being used.

  In the above embodiment, the case where an optical signal is transmitted from the wavelength path transmission / reception end optical transmission device 5 to the wavelength path transmission / reception end optical transmission device 5 ′ is described. However, the present invention is not limited to this, and as shown in FIG. 5, the path switching control system 1 of the present embodiment can be applied even when optical signals are transmitted from the bidirectional wavelength path transmission / reception end optical transmission apparatus 5. it can.

DESCRIPTION OF SYMBOLS 1 Path switching control system 2 Working path 3 Backup path 4a-4c Regenerative repeater optical transmission apparatus 4a'-4c 'Regenerative repeater optical transmission apparatus 5, 5' Wavelength path transmission / reception end optical transmission apparatus 6 O / E converter 7 Optical switch 8 Alarm reception monitor 9, 9 'Optical reception level monitor

Claims (9)

A redundant path consisting of at least a working path and a backup path;
A regenerative relay transmission device provided in the redundant path;
An optical reception level monitor provided in each of the redundant paths;
A path switching control system comprising: an alarm reception monitor provided in common with the redundant path.   The path switching control system according to claim 1, wherein the regenerative relay transmission device creates alarm information when a failure occurs in the working path. When the alarm reception monitor receives alarm information,
The path switching control system according to claim 2, further comprising an optical switch that switches the working path based on a value of the optical reception level monitor.   The path switching control system according to claim 3, wherein the optical switch switches to a path whose optical input level received by the optical reception level monitor is close to a predetermined normal value.   5. The path switching control system according to claim 4, wherein when the working path is switched, the regenerative repeater transmission apparatus connected to the working path stops outputting an optical signal.   6. The path switching control system according to claim 5, wherein the regenerative repeater transmission apparatus gradually stops output of an optical signal.   The path switching control system according to claim 6, wherein the regenerative repeater transmission device includes an optical amplifier, and adjusts the level of the optical amplifier according to a change in optical level. When the failure in the working path is recovered, the regenerative relay transmission device
3. The path switching control system according to claim 2, wherein a release of the alarm information is transmitted and output of an optical signal is started again. When a failure occurs on one path, it sends alarm information,
When the alarm information is received, the light input level in the one path and the other path is detected,
The optical input level is switched to a path close to a predetermined normal value,
A path switching control method characterized by stopping an optical output signal.

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