JPH09261132A - Redundant switching method for data transmission system - Google Patents

Abstract

(57) [Abstract] (Correction) [PROBLEMS] Redundancy monitoring and its switching control are performed using a front end reception failure signal (FERF). SOLUTION: A pair of transmission line switching devices 20 each including a switch unit SW for switching a working signal and a standby transmission signal, a distribution unit H for distributing a reception signal from a transmission line to a working signal and a backup signal, and a switch switching control unit SWC. , 40 are provided facing each other in the middle of the transmission line, and the terminal station device 10 uses the FERF
Redundancy switching on the local station side is performed by signal detection. In this case, if the opposite station detects an abnormal reception while it is in the working / standby state, it is considered as a failure / ', and redundancy switching is performed only on the own station side. Also, if the opposite station detects a reception abnormality in both the working / standby state, it is considered to be a failure / failure and the terminal device is given an F
Send ERF. If the reception abnormality is resolved before the elapse of a predetermined time after the FERF is transmitted, the opposite station is considered to be in trouble and does not perform its own redundancy switching. If the reception abnormality is not resolved even after the lapse of a predetermined time, the opposite station is considered to be in trouble and issues an alarm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redundancy switching system for a data transmission system, and more specifically, a pair of terminal station devices having a redundant structure of a working system and a standby system facing each other for transmission and reception of a main signal for data transmission. The present invention relates to a redundant switching system of a data transmission system that performs the above. Today, this type of data transmission system adopts a dual redundant configuration (line protection) of the transmission line in accordance with the ITU-T standard.
However, in a data transmission system having, for example, a submarine cable, it is extremely difficult to adopt a dual redundant configuration of cables due to cost problems. Therefore, it is desired to provide a redundant switching system suitable for such a data transmission system.

[0002]

2. Description of the Related Art FIG. 5 is a diagram for explaining a redundancy switching system of a conventional data transmission system. In the A station, 10 is a terminal device (data transmission device), 11 is a demultiplexing unit for the main signal, 12 is a transmitting unit (TX-W) of the working system, 13 is the receiving unit (RX-W), and 14 is Backup system transmitter (TX-P),
Reference numeral 15 is the receiving unit (RX-P), and 16 is a line monitoring control unit.

In the B station, 30 is a terminal device (data transmission device), 31 is a main signal demultiplexing unit, 32 is a working receiving unit (RX-W), and 33 is a transmitting unit (TX-).
W), 34 are receivers (RX-P) of the standby system, 35 are transmitters (TX-P) of the same, and 36 is a line monitoring controller.
In general, the same main signal is exchanged between the working system and the protection system, and the terminal devices 10 and 30 usually perform signal processing with the working main signal as the working side and the protection system main signal as the protection side. However, if a failure occurs in the active system, signal processing is performed with the main signal of the active system as the standby side and the main signal of the standby system as the active side.

Conventionally, as shown in the figure, the transmission section and the transmission line are duplicated, and the terminal stations 10 and 30 perform smooth redundant switching control by exchanging line switching information on the protection side line. Hereinafter, a specific description will be given. For example, if a failure occurs on the working transmission line, the receiving unit 3 at station B receives
2 detects the abnormal reception ALM-W and notifies the monitoring controller 36 of the abnormal reception.

Upon receiving the notification of the reception abnormality ALM-W, the supervisory control unit 36 switches the receiving route of the B station to the receiving unit 34 side, and switches the transmitting route of the B station to the transmitting unit 35 side. The reception failure detection signal FERF-W is inserted into the K1 and K2 bytes in the main signal and returned to the A station. A
In the station, the supervisory control unit 16 controls the K in the received main signal.
1, K2 bytes are constantly monitored, and when the reception failure detection signal FERF-W is detected, the receiving route of the A station is switched to the receiving unit 15 side, and the transmitting route of the A station is switched to the transmitting unit 14 side. , The switching completion signal is inserted in the K1 / K2 bytes in the main signal and transmitted to the B station.

In this way, the synchronization switching control from the active system to the standby system is performed. The same applies to the synchronization switching control from the standby system to the active system. Since the A station and the B station are configured symmetrically, if the above-mentioned failure occurs in the uplink, even if the failure 'occurs in the reverse downlink, the same processing is performed.

[0007]

As described above, in the conventional data transmission system, even if a failure occurs in the working transmission line by duplicating the transmission line, the redundant transmission line is used to make the data transmission system redundant. Switching control was performed smoothly. However, in a system in which transmission lines (cables) cannot be duplicated, such as a submarine transmission system, the conventional redundant switching method cannot be applied as it is.

In the above conventional method, for example, the transmitting unit 1
The failure 2 and the failure on the transmission path are also visible on the side of the receiving unit 32, and there is a problem that it is difficult to isolate the failure occurrence point. An object of the present invention is to provide a data transmission system capable of efficiently performing redundant monitoring and switching control of the system by simple communication control using a front end reception failure signal (FERF) even in a data transmission system in which a part of a transmission line cannot be duplicated. It is to provide a redundant switching system for a transmission system.

[0009]

The above-mentioned problem is solved, for example, by referring to FIG.
The problem is solved by the configuration of (A). That is, in the redundancy switching method of the data transmission system of the present invention (1), a pair of terminal station devices 10 and 30 each having a redundant configuration of the active system W and the standby system P for the transmission and reception of the main signal face each other for data transmission. In the redundant switching method of the data transmission system that performs the
And a switch unit 21 (41) that switches the transmission signal of the standby system P and outputs it to a single transmission line, and distributes the reception signal from another single transmission line to the reception signals of the active system W and the standby system P. And a switch switching control section 23 (43) for controlling switching of the switch section 21 (41) based on a switch control signal from the terminal device 10 (30). The switching devices 20 and 40 are provided so as to face each other in the middle of the transmission path, and the terminal station device 10 (30) monitors each received signal of the working system W and the standby system P, and at the same time, the leading reception failure signal FERF from the opposite station. When it detects that the switch control signal is output, the switching control between the working system W and the standby system P of its own station is performed.

In FIG. 1A, for example, when a fault occurs in the transmission path of the active system W, the influence of the fault reaches the terminal device 30 side via the switch section 21, the transmission path and the distribution section 42. Upon detecting the abnormal reception ALM, the terminal device 30 transmits the leading reception failure signal FERF to the opposite station 10 in the same manner as in the conventional case. The front end reception failure signal FERF is transmitted through the switch unit 41, the transmission line, and the distribution unit 22 to the terminal device 1.
Received at 0.

The terminal station device 10 monitors the respective received signals of the working system W and the standby system P, and when it detects the leading reception failure signal FERF from the opposite station 30, the working system W of its own station.
And switching control of the standby system P is performed, and a switch control signal is output. As a result, the switch unit 21 is also switched from the active system W to the standby system P, and a normal main signal is transmitted to the terminal device 30 thereafter. In this way, the active and standby synchronization switching control is smoothly performed. It should be noted that the above is the opposite when a failure occurs in the working (standby system P) transmission path.

Therefore, even in a data transmission system in which a part of the transmission line cannot be duplicated, efficient redundant monitoring of the system and its switching control can be performed by the simple communication control using the leading edge reception failure signal FERF as in the conventional case. . The above problem is solved by, for example, the structure of FIG. That is, in the redundancy switching method of the data transmission system of the present invention (2), a plurality of terminal equipments 10 ₁ , 10 10 each having a redundant configuration of the active system W and the standby system P for transmitting and receiving the main signal are provided.
_In the redundant switching system of the data transmission system in which ₂ , 30 ₁ and 30 ₂ face each other for data transmission, each terminal device 10
A pair of multiplexing units 24, 26 for respectively multiplexing the transmission signals of the active system W and the standby system P of ₁ , 10 ₂ (30 ₁ , 30 ₂ ), respectively.
(44, 46), a switch unit 21 (41) that switches each transmission signal after multiplexing and sends out to a single transmission line, and a reception signal from another single transmission line as an active system W and a standby system. The distribution unit 22 (42) that distributes the received signals of P and the received signals after the distribution are separated into the terminal devices 10 ₁ , 10 ₂ (3
0 ₁ , 30 ₂ ) and a pair of separation units 25, 27 (45, 47) for outputting to the reception lines of the active system W and the standby system P, and the terminal station devices 10 ₁ , 10 ₂ (30 ₁ , 30 _2). ), The switch switching control unit 2 for controlling the switching of the switch unit 21 (41) based on the logical sum output of the switch control signals 1 and 2 from
3 (43) and a pair of transmission path switching devices 20, 40
Are provided in the middle of the transmission path so as to face each other, and each terminal station device 10 ₁ , 1
0 ₂ (30 ₁ , 30 ₂ ) monitors the respective received signals of the active system W and the standby system P, and when the front end reception failure signal FERF from the opposite station is detected, the active system W of the own station and the standby system W are protected. The switching control of the system P is performed and the switch control signals 1 and 2 are output.

In FIG. 1B, the switch section 21 (4
In the previous stage of 1), a pair of multiplexing units 24, 26 (44, 46)
However, a pair of separating units 2 is provided downstream of the distributing unit 22 (42).
5, 27 (45, 47) are provided respectively, and these simply multiplex the current and standby main signals by, for example, time division.
To separate. Therefore, a plurality of terminal devices 10 ₁ , 10 ₂ (3
0 ₁ , 30 ₂ ) can be efficiently accommodated in a high-speed transmission line such as an optical fiber.

By the way, in such a data transmission system, it is necessary to switch the working system and the protection system for the entire system at the same time regardless of which line occurs after the multiplexing. According to the present invention (2), each terminal station device 10 ₁ , 10 ₂
(30 ₁ , 30 ₂ ) monitors the respective received signals of the active system W and the standby system P, and when the front end reception failure signal FERF from the opposite station is detected, the active system W and the standby system P of each own station are detected. Switching control of the switch control signal 1,
2 is output. On the other hand, the switch switching control unit 23 (43)
Performs switching control of the switch unit 21 (41) based on the logical sum output of the switch control signals 1 and 2 from the terminal devices 10 ₁ and 10 ₂ (30 ₁ and 30 ₂ ). Therefore, even if a failure occurs in any of the lines after multiplexing, the working and protection of the entire system can be switched simultaneously.

Preferably, in the present invention (3), in the above-mentioned present invention (1) or (2), the terminal station device 30 (1
0) monitors the respective reception states of the active system W and the standby system P, and when receiving abnormal ALM is detected in one of them, performs switching control between the active system W and the standby system P of its own station. , Output a switch control signal. In FIG. 1A, for example, when a failure occurs in the transmission path of the active system W, the terminal station device 30 detects the abnormal reception ALM only for the received signal of the active system W. In such cases,
There is no need to transmit the front end reception failure signal FERF to the terminal device 10, and it is efficient if the terminal device 30 can process this independently.

Therefore, the terminal device 30 monitors the respective reception states of the active system W and the standby system P and, for example, the active system W.
When the reception abnormality ALM is detected only in the reception state of, the switching control of the working system W and the protection system P of the local station is performed and the switch control signal is output to the switch switching control unit 43 on the local station side. The same applies to FIG. 1 (B).

Therefore, it is possible to efficiently isolate the location of the failure and perform quick maintenance. In addition, redundant switching control can be efficiently performed only by switching on the side of the terminal device 30. Further, preferably, in the present invention (4), in the above-mentioned present invention (1) or (2), the terminal station device 30 (10) is a working system W.
Also, the reception states of the backup system P and the standby system P are monitored, and when the abnormal reception ALM is detected for both of them, the front end reception failure signal FERF is sent to the opposite station.

In FIG. 1 (A), for example, when a failure or a failure occurs in the transmission path of the active system W, the terminal station device 30 detects the abnormal reception ALM for each of the received signals of the active system W and the standby system P. Will be done. Therefore, in this case, the terminal station device 30 monitors the reception states of the working system W and the standby system P, and when the reception abnormality ALM is detected for both of them, the tip station reception failure signal FERF is sent to the opposite station 10.
Is sent.

That is, a failure that cannot be handled on the side of the terminal device 30 is efficiently detected, and switching control is urged to the opposite station 10 only when the failure cannot be handled. FIG. 1 (B)
The same applies to. Therefore, the location of the failure can be efficiently separated and the maintenance can be performed quickly. Further, the frequency of occurrence of redundant switching control in each terminal device is reduced, and the processing load thereof is greatly reduced.

Preferably, in the present invention (5), the terminal station device 30 (10) in the above invention (4).
Measures a predetermined time after sending the front-end reception obstacle signal FERF, and receives a reception abnormality ALM before the predetermined time elapses.
When the detection of is canceled, the switching control between the active system and the standby system of the local station and the output of the switch control signal are not performed. FIG.
In (A), the terminal station device 10 completes the active / standby switching control within a predetermined time after receiving the leading edge reception failure signal FERF from the terminal device 30. Therefore, for example, the active system W
When a failure occurs in the transmission line of No. 2, the detection of the abnormal reception ALM in the terminal device 30 is resolved within a predetermined time.

In such a case, the current / current operation on the side of the terminal device 30 is performed.
Since it is not necessary to switch the backup, the switching control between the working system and the standby system of the own station, and the switch control signal is not output to the switch switching control unit 43. The same applies to FIG. 1 (B). Therefore, the location of the failure can be efficiently separated and the maintenance can be performed quickly. Further, the frequency of occurrence of redundant switching control in each terminal device is reduced, and the processing load thereof is greatly reduced.

Further, preferably, in the present invention (6), the terminal station device 30 (10) in the above invention (4).
Measures the predetermined time period after sending the front-end reception obstacle signal FERF, and at the same time receives the abnormal reception AL before the predetermined time period elapses.
If the detection of M is not canceled, the system issues a transmission line fault alarm. In FIG. 1A, for example, when a failure occurs in the transmission path of the active system W, the detection of the reception abnormality ALM in the terminal device 30 is not resolved even after a predetermined time has elapsed. In such a case, since there is no prospect of recovery as it is, a warning of a transmission line failure is issued to the system.

The same applies to FIG. 1 (B). Therefore, the location of the failure can be efficiently separated and the maintenance can be performed quickly. Further preferably, in the present invention (7),
In the above invention (2), the switch switching control unit 23
In (43), the switching control of the switch section 21 (41) is performed, and the switching control of the switch section 21 (41) is not performed for a predetermined time thereafter.

In FIG. 1B, for example, when a failure occurs between the multiplexing unit 24 and the switch unit 21,
If the redundant switching control is performed on the side of the terminal devices 10 ₁ and 10 ₂ according to the present invention (2), each reception abnormality ALM on the side of the terminal devices 30 ₁ and 30 ₂ is directly resolved. However, since the main signal including an error is separated by the separation units 45 and 47, the terminal devices 30 ₁ and 30 ₂ receive them with a fixed time difference. Therefore, the front end reception failure signal F of the terminal device 30 ₁
The system once redundantly switched by the ERF 1 is the terminal device 3
There is a possibility that redundant switching may be performed again with the leading edge reception failure signal FERF2 of 0 ₂ . The possibility increases in a transmission system that accommodates a large number of terminal devices 10 and 30.

According to the present invention (7), the flap of redundant switching can be effectively avoided by providing the switch switching control section 23 (43) with a predetermined dead period.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the same reference numerals indicate the same or corresponding parts throughout the drawings. FIG. 2 is a diagram showing the configuration of the data transmission system according to the first embodiment. In FIG. 2, 10 is a terminal station device (data transmission device) on the A station side, 11 is a demultiplexing unit for demultiplexing a main signal, Reference numeral 12 denotes a working transmission unit (TX-W), 13 denotes the same reception unit (RX-W), 14 denotes a protection transmission unit (TX-P),
Reference numeral 15 is the receiving unit (RX-P), 16 is a line monitoring control unit, 20 is a transmission line switching device on the side of station A, 21 is a transmission line switching switch unit (SW), and 22 is a transmission line signal distribution unit. (H), 23 is a switch switching control unit (SWC), 30 is a terminal station device (data transmission device) on the B station side, 31 is a demultiplexing unit for demultiplexing the main signal, and 32 is a receiving unit of the active system ( R
X-W), 33 is the same transmitter (TX-W), 34 is the standby receiver (RX-P), 35 is the same transmitter (TX-P),
36 is a line supervisory control unit, 40 is a transmission line switching device on the B station side, 41 is a transmission line changeover switch unit (SW), 42 is a transmission line signal distribution unit (H), and 43 is a switch changeover control unit ( SWC).

The transmission line is composed of a metallic line or an optical fiber and is laid on the land or the sea bottom. The transmission path switching device 20 may be provided in the A station or may be provided in a place apart from the A station. Transmission line switching device 4
The same applies to 0. The signal distribution unit 42 duplicates the main signal received from the transmission path and distributes the same main signal to the working system and the standby system. Therefore, if some failure occurs before the signal distribution unit 42, the influence extends to the working system and the backup system of the B station. On the other hand, if a failure occurs behind the signal distribution unit 42, the effect only affects the working system or the backup system of the B station. The same applies to the signal distributor 22.

The receiving section 32 is in an abnormal state (disconnection, etc.) of the received signal.
Is detected and a reception abnormality detection signal ALM-W = 1 is output. Further, the receiving unit 32 receives the leading edge reception failure signal F in the received signal.
The ERF is detected and a signal FERF = 1 indicating that the signal is detected is output. The same applies to the receiving units 34, 13, and 15. The monitoring control units 16 and 36 are composed of, for example, a CPU (not shown) and a memory storing a processing program thereof, and each of them executes the redundancy switching control of FIG. The monitoring control units 16 and 36 may be configured by hardware.

FIG. 3 is a diagram for explaining the operation of the redundant switching system according to the first embodiment, and shows respective processing flows in the supervisory control units 16 and 36. In the station B, the occurrence of the reception abnormality ALM = 1 is monitored in step S11.
When ALM = 1 is detected, (AL
It is determined whether or not MW = 1) * (ALM-P = 1).
That is, it is determined whether or not the reception abnormality ALM = 1 is detected in both the active system and the standby system.

When the abnormal reception ALM is detected in both the working and protection, it is considered to be a failure before the signal distributor 42 of FIG. The flow advances to step S13 to insert the leading edge reception failure signal FERF into the X1 / X2 bytes of the main signal and transmit it to the A station. Since this transmission is not a fault on the B station side, it is preferable that it be the working side (working system or standby system).
Do with. This FERF signal is transmitted through the transmission line,
Reach station A.

In station A, the monitor controller 16 monitors the FERF signal in the main signal in step S1. Then, when the FERF signal is detected, the working mode and the backup mode of the own station are switched at a predetermined timing (for example, a break in the transmission frame) in step S2. At the same time, a switch control signal is sent to the transmission path switching device 20, and the connection of the changeover switch unit 21 is switched to the standby side (active system or standby system).

Returning to the processing of the station B, the supervisory controller 36 sends the FERF signal in step S13, and then executes step S1.
In step 4, a timer for a predetermined time is started, and step S1
At 5 it is again determined whether or not the reception abnormality ALM = 1. That is, it waits until the reception abnormality ALM = 1 is resolved. Reception error ALM
If = 1, it is determined in step S16 whether or not the timer has timed out. If not, the process returns to step S15.

In FIG. 2, for example, when a failure or '(or the transmitting unit 12/14, etc.) occurs, the reception abnormality ALM = 1 at the B station is determined for a predetermined time by switching the working station and the standby station at the A station. It should be resolved within. Returning to FIG. 3, in this case, before the timer times out in step S16, the reception error AL is detected in step S15.
The state of M = 1 is resolved. After that, the data transmission is continued in this state.

In FIG. 2, if a failure occurs on the transmission line, for example, the status of the reception abnormality ALM = 1 at the station B cannot be eliminated despite the switching between the working and standby at the station A. Returning to FIG. 3, in this case, the timer times out in step S16, which causes the monitoring controller 36 to generate alarm information.
Notify the monitoring center.

If the determination in step S12 is not satisfied, it is considered that the failure is behind the signal distributor 42 in FIG. In this case, the flow proceeds to step S17, and the working and protection in station B are switched to a predetermined timing (for example, a break in the transmission or reception frame). At the same time, a switch control signal is sent to the transmission path switching device 40 to connect the changeover switch unit 41 to the spare side (active system or standby system).
Switch to

In FIG. 2, for example, the obstacle or
(Or the receiving unit 32/34, etc.), the above B
The state of the reception abnormality ALM = 1 at the B station is directly resolved by the switching between the working and the standby at the station. After that, the data transmission is continued in this state. Since the station A side and the station B side are symmetrically configured, if the above-mentioned failure occurs in the uplink, the same method is used even when the failure occurs in the downlink.

As described above, according to the first embodiment, even in the transmission system in which the redundant configuration (line protection) cannot be adopted in a part of the transmission line, the data transmission system using the FERF signal similar to the conventional one is used. The efficient redundant switching control can be performed. Therefore, there are few parts to add or change to the existing configuration. Furthermore, the location of the failure can be identified by simple logic processing, and maintenance can be performed quickly.

FIG. 4 is a diagram showing the configuration of a data transmission system according to the second embodiment, in which 10 ₁ to 10 _n is shown.
2 are terminal devices (data transmission devices) equivalent to the terminal device 10 of FIG. 2, 24 is a multiplexing unit (MUX-W) of the working system, and 26
Is a spare system multiplexing unit (MUX-P), 25 is a working system separating unit (DMUX-W), and 27 is a spare system separating unit (DMUX).
-P), 30 ₁ to 30 _n are terminal station devices (data transmission devices) equivalent to the terminal station device 30 of FIG. 2, 44 is a working multiplexing unit (MUX-W), and 46 is a standby multiplexing unit. (MUX-
P), 45 is a separation unit (DMUX-W) for the active system, and 47 is a separation unit (DMUX-P) for the standby system.

Each multiplexer simply time-division-multiplexes the main signal from each terminal device and outputs it to the changeover switch.
Further, each separation unit simply time-division-separates the main signal from each distribution unit and outputs these to each terminal station device. Therefore, a plurality of terminal devices 10 ₁ to 10 _n (30 _{1 to} 3) are configured with a simple configuration.
0 _n ) can be efficiently accommodated in a high-speed transmission line such as an optical fiber.

The switch switching control units 23 and 43 perform active / standby switching control of the corresponding switching switch units based on the logical sum output of the switch control signals 1 to n from each terminal device. Therefore, in such a data transmission system,
Even if a failure occurs in any of the lines after multiplexing, the working and protection of the entire system can be switched simultaneously. In this case, each of the switch switching control units 23 and 43 is provided with a dead period (timer control) of the switching control, and when the switching control of the switching switch unit is performed at a certain timing, the switch switching signal is given for a predetermined time thereafter. Regardless of the presence or absence of the above, switching control of the changeover switch unit is not performed.

Therefore, the delay difference due to the multiplexing / demultiplexing of the main signal
Therefore, each terminal device 30₁~ 30_nEach FER from the side
The F signal is sent with a time difference, which allows each terminal device to
10 ₁-10_nControl of the changeover switch section 21 on the side of
The inconvenience of going many times can be effectively avoided.
The predetermined time in this case depends on the configuration of the data transmission system.
It is appropriately set according to (the number of multiplexes, etc.).

The configuration and operation of the other parts may be the same as those described in the first embodiment. Therefore, similarly to the case of the first embodiment, the failure location is separated and the redundant switching control corresponding to the failure location is smoothly performed. By the way, in FIG. 4, when there is a failure in the working transmission line between the terminal device 10 ₁ and the multiplexing unit 24 before multiplexing, only the opposite terminal device 30 ₁ detects the abnormal reception ALM. Will be done.
On the other hand, the terminal device 30 ₁ receives the front end reception failure signal FE.
RF is transmitted, but this is multiplexed / demultiplexed and finally detected only by the opposite terminal device 10 ₁ . As a result, the terminal device 10 ₁ switches the active protection of its own station and outputs the switch control signal 1, but if it is left as it is, the other terminal device 1 1
Synchronization switching with 0 ₂ to 10 _n cannot be performed.

In such a case, for example, the logical sum output of the switch changeover control unit 23 is set to each terminal device 10 ₁ to 10 _1.
Return to _n . This enables synchronization switching among the terminal devices 10 ₁ to 10 _n . The same applies to the terminal devices 30 ₁ to 30 _n . Although the above embodiments have described the data transmission system in the case of including all the characteristic portions according to the present invention, the data transmission system may be configured by combining arbitrary characteristic portions.

Although a plurality of preferred embodiments of the present invention have been described above, it goes without saying that various modifications of the configuration, control, and combinations thereof can be made without departing from the spirit of the present invention. There is no.

[0045]

As described above, according to the present invention, even in a data transmission system in which a part of the transmission line cannot be duplicated, simple communication control using the leading edge reception failure signal (FERF) enables efficient system operation. Redundant monitoring and its switching control can be performed, and it greatly contributes to the reliability improvement of the undersea transmission system.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing a configuration of a data transmission system according to the first embodiment.

FIG. 3 is a diagram for explaining the operation of the redundant switching system according to the first embodiment.

FIG. 4 is a diagram showing a configuration of a data transmission system according to a second embodiment.

FIG. 5 is a diagram illustrating a redundancy switching method of a conventional data transmission system.

[Explanation of symbols]

 10, 30 Terminal device 11, 31 Demultiplexer 12, 14, 33, 35 Transmitter 13, 15, 32, 34 Receiver 16, 36 Monitoring controller 20, 40 Transmission line switching device 21, 41 Changeover switch 22 , 42 Signal distribution unit 23, 43 Switch switching control unit 24, 26, 44, 46 Multiplexing unit 25, 27, 45, 47 Separation unit

Claims (7)

[Claims] 1. A redundant switching system of a data transmission system, wherein a pair of terminal devices each having a redundant structure of a working system and a standby system for transmitting and receiving a main signal face each other to perform data transmission. A switch unit that switches the transmission signal and outputs it to a single transmission line, a distribution unit that distributes the reception signal from another single transmission line to the reception signals of the active system and the standby system, and the switch from the terminal device. A pair of transmission line switching devices provided with a switch switching control unit for performing switching control of the switch unit based on a control signal are provided facing each other in the middle of the transmission line. When detecting a front end reception failure signal from the opposite station, the switching control between the active system and the standby system of the local station is performed, and the switch control signal is output. Joke Switching system. 2. In a redundant switching system of a data transmission system, wherein a plurality of terminal station devices each having a redundant structure of a working system and a standby system respectively for transmitting and receiving a main signal face each other for data transmission, a working mode of each terminal device is used. A pair of multiplexers that multiplex the transmission signals of the primary and standby systems respectively, a switch unit that switches each transmission signal after multiplexing and sends it to a single transmission line, and a reception from another single transmission line A distribution unit that distributes the signals to the reception signals of the working system and the protection system, and a pair of separation units that separates the respective received signals after distribution and outputs them to the reception lines of the working system and the protection system of each terminal device. And a pair of transmission line switching devices provided with a switch switching control unit that performs switching control of the switch unit based on a logical sum output of switch control signals from each terminal device, facing each other in the middle of the transmission line, The terminal device receives each of the active system and the standby system. In addition to monitoring the signal, if a front end reception failure signal from the opposite station is detected, switching control between the active system and the standby system of the own station is performed,
A redundant switching system for a data transmission system, which outputs the switch control signal. 3. The terminal device monitors the reception status of each of the working system and the protection system, and when receiving abnormality is detected in either one of them, controls the switching between the working system and the protection system of the own station. At the same time, a switch control signal is output, and the redundant switching system of the data transmission system according to claim 1 or 2. 4. The terminal device monitors the respective reception states of the active system and the standby system, and when the reception abnormality is detected for both of them, sends the front reception failure signal to the opposite station. A redundant switching system for the data transmission system according to claim 1. 5. The terminal device measures a predetermined time after transmitting the front-end reception failure signal, and when the detection of the reception abnormality is resolved before the predetermined time elapses, the terminal station device and the standby system 5. The redundant switching system for a data transmission system according to claim 4, wherein switching control of the system and output of a switch control signal are not performed. 6. The terminal device measures a predetermined time after transmitting the front end reception failure signal, and if the detection of the reception abnormality is not resolved by the time the predetermined time elapses, a warning of the transmission path failure is given to the system. The redundant switching method of the data transmission system according to claim 4, wherein the redundant switching method occurs. 7. The redundant switching system for a data transmission system according to claim 2, wherein the switch switching control unit controls the switching of the switch unit and does not control the switching of the switch unit for a predetermined time thereafter. .