JP3781523B2 - Optical subscriber line transmission apparatus and standby optical transmission line monitoring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a passive double star (PDS) type optical subscriber line transmission apparatus that transmits and receives an optical signal between one center apparatus and a plurality of branch apparatuses. In particular, the present invention relates to monitoring of a standby optical transmission line when an optical subscriber line interface of a center apparatus is made redundant.
[0002]
[Prior art]
Conventionally, as an optical subscriber line transmission apparatus, one center apparatus and a plurality of branch apparatuses are connected by an optical fiber and an optical star coupler, and the center apparatus and the branch apparatus are both connected by one optical fiber. A PDS type that performs time-axis compressed multiplex transmission (TCM) is known. In addition, the optical transmission line between the optical subscriber line interface and the optical star coupler in the center apparatus is made redundant.
[0003]
In a PDS type optical subscriber line transmission apparatus having a redundant configuration, as a method of switching the optical subscriber line interface in the center unit, an abnormality is detected in the forced switching by the operator and the operation of the active system. There is automatic switching that automatically performs system switching in the event of a failure. In order to perform these system switching, it is a prerequisite that the standby system is normal.
[0004]
As a technique for monitoring the operating state of the active system and the standby system in the PDS type optical subscriber line transmission apparatus and other optical transmission apparatuses, JP-A-3-98331, 4-294660, and 5-37471 are disclosed. There are those described in each publication (hereinafter referred to as “Conventional Publication 1”, “Conventional Publication 2”, and “Conventional Publication 3” respectively). In the technique described in the prior art publication 1, in order to perform output monitoring at the optical level and switching between active and standby, the optical transmission signal transmitted from the optical transmission unit to the transmission line is branched to receive the optical reception signal from the transmission line. The signal is switched and input to the optical receiver, and the electrical input signal input to the optical transmitter is compared with the electrical output signal from the optical receiver. In the technique described in the prior art publication 2, a burst from the burst signal generation unit to the optical burst signal transmission unit is performed in order to check the operation of the standby optical burst signal transmission unit while avoiding a collision with the active optical burst signal. The signal supply is switched to the pause period of the burst signal. In the technique described in the prior art publication 3, since the operation of the standby optical transmitter is monitored, the standby system is always in an operating state, and the output is blocked by an optical shutter in the standby mode.
[0005]
[Problems to be solved by the invention]
In the optical transmission apparatus, that the standby system is normal requires not only that the standby transmission / reception apparatus is normal, but also that the standby optical transmission path is normal. In the case of a PDS type optical subscriber line transmission apparatus, the standby optical subscriber line interface is not mounted or failed, and the optical system between the standby optical subscriber line interface and the optical star coupler is used. It is necessary that the transmission path is normal.
[0006]
However, in the case of a PDS type optical subscriber line transmission apparatus, a transmission path (layer) cannot be established with the opposite branch apparatus in the standby system. The reason is that the center device and each branch device perform two-way communication with one optical fiber, so that the standby optical subscriber interface in the center device does not disturb the communication on the active side. This is because the light output must be stopped. For this reason, normal transmission line monitoring cannot be performed for the standby system, and conventionally, switching is possible only when the standby optical subscriber line interface is not mounted or failed.
[0007]
An object of the present invention is to solve such problems and to provide a PDS type optical subscriber line transmission apparatus capable of monitoring a standby transmission line and a standby optical transmission line monitoring method thereof.
[0008]
[Means for Solving the Problems]
A first aspect of the present invention is an optical subscriber line transmission apparatus, which distributes an optical signal from one center apparatus, a plurality of branch apparatuses, and a center apparatus to the branch apparatuses, and distributes an optical signal from each branch apparatus. Optical multiplexing / demultiplexing means for multiplexing and transmitting to the center apparatus, and at least two optical transmission paths are provided at least on the center apparatus side between the center apparatus and the optical multiplexing / demultiplexing means. , And at least two optical subscriber line interfaces respectively connected to these optical transmission lines, and control means for switching the at least two optical subscriber line interfaces between active and standby, In addition to the transmission unit and the reception unit of the optical subscriber line interface of the system, the reception unit of the standby optical subscriber interface is operated, and the active system and the standby system are respectively operated. In the optical subscriber line transmission apparatus including a means for receiving a delay measurement frame transmitted from each branch apparatus to correct a frame transmission position from each branch apparatus to the center apparatus and performing a delay measurement, the control means includes: And means for determining the normality of the optical transmission line of the backup system based on the delay measurement result of the backup system by the delay measurement means.
[0009]
In the working optical subscriber line interface, the delay between the center device and the branch device is transferred by transferring a delay measurement frame for the purpose of correcting the sending position of the upstream frame sent from the opposite branch device to the center device. Measurements are made from time to time. Since this delay measurement information is required when the standby system is switched to the active system, it is also necessary to acquire the delay measurement information in the standby system. For this,
(1) Copy from the active system
(2) There are two methods in which only the receiving unit of the optical subscriber line interface is in an operating state and the delay measurement frame notified from the branch device to the active system is also monitored in the standby system. In the present invention, focusing on the case of (2), the delay measurement result is used to determine the normality of the standby optical transmission line. At this time, if there is at least one branch device registered to communicate with the center device and the delay measurement result is obtained from at least one branch device, it is determined that the standby optical transmission line is normal. It is good to do. In other words, if no delay measurement result is obtained for any branch device, it is determined that there is an abnormality in the standby optical transmission line. In addition, when there is at least one branch device registered to communicate with the center device and a delay measurement result is obtained from at least one registered branch device, the standby optical transmission line is normal. You may judge that.
[0010]
A second aspect of the present invention relates to a standby optical transmission line monitoring method, in which a plurality of branch devices are connected between a center apparatus in which an optical subscriber line interface is redundantly configured as an active system and a standby system. Bidirectional communication is performed using the optical transmission line of the system in common, and the center device uses the delay measurement frame sent from each branch device to correct the frame sending position from each branch device to the center device, and the active system and Both the standby system receives the delay and measures the delay, and the backup system delay measurement results indicate that the backup system does not switch between the active system and the standby system when the backup optical transmission line is abnormal. The normality of the optical transmission line is determined.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an embodiment of the present invention, and shows a configuration example of a PDS optical subscriber line transmission apparatus. This PDS optical subscriber line transmission apparatus distributes an optical signal from one center apparatus 11, a plurality of branch apparatuses 12, and the center apparatus 11 to the branch apparatus 12, and combines the optical signals from each branch apparatus 12. And an optical star coupler 13 for multiplexing and transmitting to the center device 11. Two optical transmission lines are provided between the center apparatus 11 and the optical star coupler 13, and the center apparatus 11 includes two optical subscriber line interfaces 14 respectively connected to the two optical transmission lines, A control unit 15 that switches the two optical subscriber line interfaces 14 between active and standby is provided.
[0012]
FIG. 2 shows the flow of control by the control unit 15. At the start of communication, the control unit 15 sets one of the two optical subscriber line interfaces 14 as a working system and the other as a standby system, and performs communication using the working system. Further, during communication, the delay measurement frame from the branch device is received at any time, the delay measurement with the branch device is performed, and the transmission control of the upstream frame transmission position is performed. The delay measurement is also performed on the standby system so that the standby system can immediately cope with switching between the active system and the standby system. When an abnormality occurs in the active system, the normality is determined from the delay measurement result of the standby system, and if it is normal, the system is switched. If there is an abnormality in the standby system, both the active system and the standby system have an abnormality. In this case, if the system is switched from the working system to the protection system when the protection optical transmission line is abnormal, the transmission line path with the branch device cannot be established in the protection system, and a transmission line alarm cannot be detected, resulting in a silent alarm. May end up. Therefore, in this case, as is generally done with known optical transmission devices that can monitor the standby optical transmission line, the transmission line alarm is maintained in the active system so that it can be reliably detected, resulting in a silent alarm. To prevent.
[0013]
FIG. 3 shows the flow of active and standby setting control. Since bidirectional communication is performed, the active optical subscriber line interface 14 is operated by both the transmitter and the receiver. On the other hand, for the standby optical subscriber line interface 14, the transmission unit is stopped and only the reception unit is operated so as not to disturb the communication on the active side. As a result, at least a part of the optical signal from each branch device can be received and the standby optical transmission line can be monitored.
[0014]
FIG. 4 shows a control flow for normality determination of the standby system. The normality of the backup system is determined by operating normally when the backup optical subscriber line interface 14 is mounted, and the transmission path between the standby optical subscriber line interface 14 and the optical star coupler 13 is normal. On condition that
[0015]
FIG. 5 is a diagram for explaining an example of standby system normality determination. “0” indicates that the standby optical subscriber line interface is mounted, “1” indicates that it is not mounted, “0” indicates that it is operating normally, and “1” indicates that there is an abnormality. When the transmission line monitoring result is normal, “0”, and when the transmission line monitoring result is abnormal, “1”, the OR logic of these values is taken to obtain “0” when the standby system is normal. When there is an abnormality, a determination result of “1” is obtained.
[0016]
FIG. 6 is a diagram for explaining an example of the normality determination of the standby optical transmission line based on the delay measurement result for each branch device. In this determination, if there is at least one branch device registered to communicate with the center device and no delay measurement result is obtained for any branch device, there is an abnormality in the standby optical transmission line. to decide. However, when all the branch devices are not yet registered, a transmission line abnormality is not caused even if a delay measurement result is not obtained from any branch device.
[0017]
For this determination, for each branch device, the case where the delay measurement result is obtained is represented by “1”, the case of NG (no good) is represented by “0”, and the registration state is “0” indicating that the registration status is not completed. It is assumed that the current state is represented by “1”. Then, in order to determine whether or not all the delay measurement results of all the branch devices are NG, the NOR logic of the delay measurement results of all the branch devices is taken. At this time, the NOR logic result is “1” when the transmission line is disconnected, and “0” when the transmission line is normal. In addition, in order to determine whether or not at least one branch device is registered, the OR logic of the registration states of all branch devices is taken. The OR logic result is “0” when all the branch devices have not been registered, and “1” when one or more devices have been registered. By taking an AND between the result of the NOR logic and the result of the OR logic, “0” is obtained when the transmission line is normal and “1” is obtained when the transmission line is abnormal as the monitoring result of the standby optical transmission line.
[0018]
FIG. 7 shows a truth table when there are three branch devices for determining the normality of the standby optical transmission line shown in FIG. When all three branch devices are not registered, the determination result is “0”, that is, normal. When the number of registered branch devices is one, the determination is made based only on the delay measurement result for the one branch device. When the number of registered branch devices is two, the determination is made based only on the delay measurement result for the two branch devices. When the delay measurement results of the two registered branch devices are all NG, the determination result is “1”, that is, abnormal. When the number of registered branch devices is one, the determination is made based only on the delay measurement result for the one branch device. When the number of registered branch devices is 3, the determination is made based on the delay measurement result for these 3 devices. When the delay measurement results of the three registered branch devices are all NG, the determination result is “1”, that is, abnormal.
[0019]
FIG. 8 is a diagram for explaining another example of the normality determination of the standby optical transmission line based on the delay measurement result for each branch device. In this example, in order to omit the unregistered branch device from the target of the normality determination of the optical transmission line, the NAND logic of the delay measurement result and the registered state is taken for each branch device. The delay measurement result is valid only when registration is completed, and masked to “1” when not registered, regardless of the delay measurement result. In addition, in order to determine whether or not all branch devices are incompletely registered, the OR logic of the registration state of each branch device is taken, and the case where the result is “0” is determined to be incompletely registered. Then, for all the branch devices that have completed registration, in order to make the transmission path abnormal when the delay measurement result is all NG, the AND logic of the NAND logic result for each branch device is taken, and the result is The case of “1” is regarded as a transmission line abnormality. However, since the transmission path is not abnormal when all the branch devices have not been registered, the OR logic result of the registration state of each branch device is included in the above AND logic conditions.
[0020]
【The invention's effect】
In a PDS-type optical subscriber line transmission device, if the system is switched from the active system to the standby system when the standby optical transmission line is abnormal, the standby system cannot detect the transmission path alarm without establishing a transmission path with the branch device. Because it can not, you may fall into a silent alarm. On the other hand, according to the present invention, the standby optical transmission line can be monitored even in the PDS type optical subscriber line transmission apparatus, and system switching can be suppressed when the standby optical transmission line is abnormal. As is generally done with known optical transmission devices that can monitor the transmission line alarm, it is possible to keep the transmission line alarm in an active system that can be reliably detected, and to prevent a silent alarm from occurring.
[0021]
In addition, if the system is switched from the active system to the standby system when the standby optical transmission line is abnormal, the transmission path cannot be established with the branch device in the standby system, and the communication service cannot be operated. Since the system switching is performed only when the system optical transmission line is normal, the operation of the communication service after the system switching can be surely guaranteed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a diagram showing a flow of control by a control unit.
FIG. 3 is a diagram showing a flow of setting control for active and standby.
FIG. 4 is a diagram showing a control flow of normality determination of a standby system.
FIG. 5 is a diagram for explaining an example of standby system normality determination;
6 is a diagram for explaining an example of normality determination of a standby optical transmission line based on a delay measurement result for each branch device; FIG.
FIG. 7 is a diagram showing a truth table for determining the normality of a backup optical transmission line when there are three branch devices.
FIG. 8 is a diagram for explaining another example of normality determination of a standby optical transmission line based on a delay measurement result for each branch device;
[Explanation of symbols]
11 Center device 12 Branch device 13 Optical star coupler 14 Optical subscriber line interface 15 Control unit

Claims (4)

One center device, a plurality of branch devices, and an optical signal from the one center device are distributed to the plurality of branch devices, and an optical signal from each of the plurality of branch devices is combined into one to Optical multiplexing / demultiplexing means for transmitting to one center device,
At least two optical transmission lines are provided between the center device and the optical multiplexing / demultiplexing means,
The center device includes at least two optical subscriber line interfaces respectively connected to the at least two optical transmission lines, and control means for switching the at least two optical subscriber line interfaces between active and standby,
The control means operates the receiving unit of the standby optical subscriber interface in addition to the transmitting unit and the receiving unit of the active optical subscriber line interface, and from each branch device for each of the active system and the standby system. means for performing a delay measurement by receiving the delay measurement frame each branch unit sends out to correct the frame transmission position to the center device, the spare system by the delay measurement result of the protection system by means for performing the delay measurement and means for performing normality determination of the optical transmission line
In optical subscriber line transmission equipment,
The means for determining the normality is a standby optical transmission when there is at least one branch device registered to communicate with the center device and no delay measurement result is obtained for any branch device. An optical subscriber line transmission apparatus comprising means for determining that a path is abnormal . One center device, a plurality of branch devices, and an optical signal from the one center device are distributed to the plurality of branch devices, and an optical signal from each of the plurality of branch devices is combined into one to Optical multiplexing / demultiplexing means for transmitting to one center device,
At least two optical transmission lines are provided between the center device and the optical multiplexing / demultiplexing means,
The center device includes at least two optical subscriber line interfaces respectively connected to the at least two optical transmission lines, and control means for switching the at least two optical subscriber line interfaces between active and standby,
The control means operates the receiving unit of the standby optical subscriber interface in addition to the transmitting unit and the receiving unit of the active optical subscriber line interface, and from each branch device for each of the active system and the standby system. Means for receiving the delay measurement frame sent from each branch device to correct the frame sending position to the center device and measuring the delay, and the result of the delay measurement of the standby system by the means for performing the delay measurement. Means for determining the normality of the optical transmission line
In optical subscriber line transmission equipment,
The means for determining the normality has at least one branch device registered to communicate with the center device, and when a delay measurement result is obtained from at least one registered branch device, Includes means for determining that the backup optical transmission line is normal
An optical subscriber line transmission apparatus . A plurality of branch devices perform two-way communication using the optical transmission line of the active system or the standby system in common between the center apparatus in which the optical subscriber line interface is configured redundantly in the active system and the standby system,
The center device performs delay measurement by receiving the delay measurement frame transmitted by each branch device in both the active system and the standby system in order to correct the frame transmission position from each branch device to the center device, and In order to prevent switching between the active system and the standby system when the standby optical transmission line is abnormal, the normality of the standby optical transmission line is determined based on the result of the delay measurement of the standby system.
In the standby optical transmission line monitoring method,
When the center device and registered branch device as to perform communication Ri least Hitotsua, and not be obtained delay measurement results for any branch unit, determines that there is an abnormality in the optical transmission line of the standby system
A standby optical transmission line monitoring method . A plurality of branch devices perform two-way communication using the optical transmission line of the active system or the standby system in common between the center apparatus in which the optical subscriber line interface is configured redundantly in the active system and the standby system,
The center device performs delay measurement by receiving the delay measurement frame transmitted by each branch device in both the active system and the standby system in order to correct the frame transmission position from each branch device to the center device, and In order to prevent switching between the active system and the standby system when the standby optical transmission line is abnormal, the normality of the standby optical transmission line is determined based on the result of the delay measurement of the standby system.
In the standby optical transmission line monitoring method,
When there is at least one branch device registered to communicate with the center device and a delay measurement result is obtained from at least one registered branch device, the standby optical transmission line is normal. Judge that there is
A standby optical transmission line monitoring method .

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