JP3044869B2 - Fault point search device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault point searching apparatus for an optical repeater transmission system, and more particularly to a fault point searching apparatus capable of evaluating a broken section of an optical fiber cable and a faulty optical repeater.

[0002]

2. Description of the Related Art Conventionally, in an optical repeater transmission system, various types of fault point searching methods have been adopted in order to detect and specify a position such as a failure of an optical repeater or a disconnection of an optical fiber cable. Such a fault point search system has a configuration in which, for example, a wire cable is drawn in parallel with an optical fiber cable, and a monitoring control device is connected one-to-one to each optical repeater, and each monitoring control device is connected by a wire cable. ing. The fault point search method uses a fault point based on fault information transmitted from a monitoring control device connected to the optical repeaters at both ends of the faulty cable or a monitor control device connected to the faulty optical repeater. Has been identified.

[0003]

The above-described conventional method for searching for a fault in an optical repeater transmission system has disadvantages in that it is uneconomical due to a large device and circuit scale, and that it consumes a large amount of power.

An object of the present invention is to provide a fault point searching circuit which solves the above-mentioned disadvantages, reduces the circuit scale, and reduces power consumption.

[0005]

In order to achieve the above object, a fault point searching device according to the present invention comprises a first optical switch connected to one of an upstream fiber cable and a downstream fiber cable or an internal path, and the other. A second optical switch connected to an upstream fiber cable and a downstream fiber cable or an internal path, and an upstream optical transmission / reception board that amplifies the upstream optical signal and outputs an optical path switching signal when detecting an optical reception interruption of the upstream optical signal And a downstream optical transmitting and receiving board that amplifies the downstream optical signal and outputs an optical path switching signal when detecting interruption of optical reception of the downstream optical signal;
The optical signal from the first optical switch is input to the upstream optical transmission / reception board, and the optical signal from the upstream optical transmission / reception board is guided to the second optical switch, or the optical signal from the first optical switch is transmitted to the upstream optical transmission / reception board. A third optical switch that bypasses the transmission / reception board and leads to the second optical switch, and an optical signal from the second optical switch is input to the downstream optical transmission / reception board, and an optical signal from the downstream optical transmission / reception board is transmitted to the first optical switch. A fourth optical switch which guides the optical signal from the second optical switch or guides the optical signal from the second optical switch to the first optical switch by bypassing the downstream optical transmission / reception board; And a remote alarm circuit that superimposes on a light signal.

According to the present invention, when the optical repeater does not receive an optical signal, the optical path of the optical signal is switched by each optical switch, and the optical signal is transmitted back to the optical terminal repeater that sent the optical signal. At this time, since information indicating that the optical switch has been switched from the remote alarm circuit is superimposed on the returning optical signal, it is possible to evaluate the broken section of the optical fiber cable and the failed optical repeater.

[0007]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a fault point searching apparatus according to the present invention.

The optical repeater 1 shown in FIG. 1 incorporates a failure point searching device and a control device and a power supply device (not shown). The fault point searching device includes the first optical switch 11,
It comprises a second optical switch 12, a third optical switch 13, a fourth optical switch 14, an upstream optical transmission / reception panel 15, a downstream optical transmission / reception panel 16, and a remote alarm circuit 17.

Here, the optical switch 11 is a switch SW
_1X and SW _1Y to connect / disconnect the optical cables L _mu and L _md and to connect / disconnect the input / output terminals of the optical switch 11.
Perform cutoff. In this optical switch 11, the switch SW _1X
The optical cable L _mu is connected to the terminal a of the switch SW _1Y , the optical cable L _md is connected to the terminal a of the switch SW _1Y , and the terminal b of the switch SW _1Y is connected to the terminal b of the switch SW _1X .
In the optical switch 11, the common terminal of the switch SW _1X is connected to the common terminal of the switch SW _3X of the optical switch 13, and the common terminal of the switch SW _1Y is connected to the optical switch 1
4 is connected to the common terminal of the switch SW _4Y .

The optical switch 12 includes switches SW _2X , SW
_2Y , connecting / disconnecting optical cables L _nu , L _nd ,
In addition, connection / cutoff between the input / output terminals of the optical switch 12 is performed. In this optical switch 12, the terminal c of the switch SW _2X
The optical cable L _nu The optical cable L _nd to the terminal c of the switch SW _2Y is, the terminal d of the switch SW _2X terminal d of the switch SW _2Y are connected respectively. In the optical switch 12 connects the common terminal of the switch SW _2X to the common terminal of the switch SW _4X optical switch 14.

The optical switch 13 includes switches SW _3X , SW
_It has _3Y , and performs connection / blocking between input / output of the optical transmission / reception board 15 and connection / blocking between input / output terminals of the optical switch 13. In this optical switch 13, the input terminal of the optical transceiver 15 is connected to the terminal e of the switch SW _3X , and the switch SW _3Y
The output terminal of the optical transceiver 15 is connected to the terminal e of the switch S.
The terminal f of the switch SW _3Y is connected to the terminal f of W _3X . In the optical switch 13, the common terminal of the switch SW _3Y is of the optical switch 12 switches SW
Connected to _2X common terminal.

The optical switch 14 includes switches SW _4X , SW
_4Y , which connects / disconnects between the input and output of the optical transceiver 16 and connects / disconnects between the input / output terminals of the optical switch 14. In the optical switch 14, the terminal g of the switch SW _4X is connected to the input terminal of the optical transceiver 16 by the switch SW _2Y.
Is the output terminal of the optical transmission / reception panel 16 and the switch S
The terminal h of the switch SW _4Y is connected to the terminal h of W _4X .

The optical transmitting / receiving board 15 includes an optical receiving circuit (O / E).
51, an optical transmission circuit (E / O) 52, and a switch control circuit (SW CONT) 53. Optical receiving circuit 51
Converts the input optical signal into an electric signal and inputs the electric signal to the optical transmission circuit 52. Further, the optical receiving circuit 51 sends a signal regarding a failure or the like to the switch control circuit 53 and the remote alarm circuit 1.
Give 7 The optical transmitting circuit 52 amplifies the electric signal from the optical receiving circuit 51, converts the electric signal into an optical signal, outputs the optical signal, and performs a predetermined operation based on the signal from the remote alarm circuit 17. The switch control circuit 53 controls the switching of the optical switches 11 and 14 based on the signals from the optical receiving circuit 51 and the remote alarm circuit 17.

The optical transmitting / receiving board 16 includes an optical receiving circuit (O / E).
61, an optical transmission circuit (E / O) 62, and a switch control circuit (SW CONT) 63. Optical receiving circuit 61
Converts the input optical signal into an electric signal and inputs the electric signal to the optical transmission circuit 62. Further, the optical receiving circuit 61 sends a signal relating to a failure or the like to the switch control circuit 63 and the remote alarm circuit 1.
Give 7 The optical transmitting circuit 52 amplifies the electric signal from the optical receiving circuit 51, converts the electric signal into an optical signal, outputs the optical signal, and performs a predetermined operation based on the signal from the remote alarm circuit 17. The switch control circuit 53 controls the switching of the optical switch 12 and the optical switch 12 based on signals from the optical receiving circuit 61 and the remote alarm circuit 17.

The operation of the fault point searching device thus configured will be described.

In the fault point searching device, it is assumed that the optical switches 11, 12, 13, and 14 are normally connected as shown in the figure. In addition, each of the optical switches 11, 12, 1
3 and 14 indicate that when any abnormality occurs, the optical switch 11, the optical switch 14, the optical switch 12, and the optical switch 13 or all the switches 11, 12, 13, and 14 are in a connection state indicated by a dotted line. I do.

First, an optical signal transmitted from the optical fiber cable L _mu, which is an upstream transmission line, passes through the optical switch 11 and the optical switch 13 in the optical repeater 1 and is electrically transmitted to the optical receiving circuit 51 of the optical transmitting and receiving board 15. The signal is converted and discriminated and reproduced. After that, the optical signal is converted again into an optical signal by the optical transmission circuit 52 of the optical transmission / reception board 15, and is transmitted to the optical fiber cable _Lnu via the optical switch 13 and the optical switch 12. Similarly, the optical fiber cable L which is a downlink transmission line
_The optical signal transmitted from the _nd is converted to an electric signal by the optical receiving circuit 61 of the optical transmitting and receiving panel 16 through the optical switch 12 and the optical switch 14, and is discriminated and reproduced. afterwards,
The optical signal is converted into an optical signal by an optical transmission circuit 62 of the optical transmission / reception board 16,
The light is sent to the optical fiber cable _Lmd via the optical switch 14 and the optical switch 11.

Next, the optical fiber cable L_muBreaks
Considering that the optical receiving circuit 51 of the optical transmitting and receiving
Is an optical fiber cable L_muDisconnection of optical reception due to disconnection of
And sends an optical reception interruption detection signal to the switch control circuit 53.
Put out. The switch control circuit 53 receives the optical reception detection signal.
If received, sends an optical path switching signal to the optical switch 11
You. The optical switch 11 has received the optical path switching signal
Then, the optical path of the optical signal is switched from the terminal a to the terminal b. This
Here, the optical fiber cable L of the downstream transmission path_ndTransmitted from
The transmitted optical signal is transmitted to the optical switch 12 and the optical switch.
14 via the optical receiving circuit 61 of the optical transceiver 16
After being converted to a signal and discriminated and reproduced, the optical transmission circuit 62
The optical signal is again converted to an optical signal and supplied to the optical switch 14.
The optical signal transmitted through the optical switch 14 is an optical switch.
The optical path of the switch 11 is switched from the terminal a to the terminal b.
Therefore, the optical fiber cable L of the downstream transmission line_ndTransmitted from
The transmitted optical signal is transmitted and received via the optical switch 12.
The signal is input to the optical receiving circuit 51 of the transmission board 15. Optical receiving circuit 5
In 1, after being converted into an electric signal and discriminated and reproduced,
To the optical transmission circuit 52. The optical transmission circuit 52
Signal to an optical signal, and the optical signal is
Optical fiber cable L via the optical switch 12_nu
Send to The optical receiving circuit 51 is provided with an optical fiber cable.
Table L_ndReceiving the optical signal transmitted from the
The signal is sent to the switch control circuit 53 to release the optical reception interruption detection signal.
However, it is transmitted from the switch control circuit 53 to the optical switch 11.
The issued optical path switching signal is not released, and the optical switch
In the state where the optical path 11 is switched from the terminal a to the terminal b.
Hold. To release the optical path switching signal, use an optical fiber cable.
Bull L _muWhen the disconnection is restored, an optical terminal (not shown)
Reset signal superimposed on the optical signal sent from the relay device
This is performed by detecting

Even when the optical fiber cable _Lnd is disconnected, the optical signal transmitted from the optical fiber cable _Lmu on the upstream transmission line is transmitted to the optical switch 1 in the same manner as described above.
Since the optical path of No. 2 is switched from the terminal c to the terminal d, the optical switch 11, the optical switch 13, the optical transceiver 15, the optical switch 13, the optical switch 12, the optical switch 14, the optical transceiver 16, the optical switch 14, the optical switch 11 _Is transmitted to the optical fiber cable _Lmd through the path.

Further, the optical receiving circuit 61 of the optical transmitting / receiving board 16
Alternatively, it is assumed that the optical transmission circuit 62 fails and no optical signal is transmitted to the downstream optical fiber cable _Lmd, and no optical signal is transmitted from the upstream optical fiber cable _Lmu .

The optical receiving circuit 51 of the optical transmitting and receiving board 15 detects the interruption of the light reception from the optical fiber cable _Lmu, and sends out the signal for detecting the interruption of the light to the switch control circuit 53. The switch control circuit 53 sends an optical path switching signal to the optical switch 11 upon receiving the optical reception interruption detection signal. Upon receiving the optical path switching signal, the optical switch 11 switches the optical path of the optical signal from the terminal a to the terminal b. Here, the optical signal transmitted from the optical fiber cable _Lnd of the downstream transmission line is input to the optical receiving circuit 61 of the optical transmitting and receiving board 16 via the optical switch 12 and the optical switch 14, but the optical receiving circuit 61 Alternatively, since the optical transmission circuit 62 has failed,
The optical signal transmitted from the optical fiber cable _{Lnd on} the downstream transmission path is not output from the optical transmission circuit 62. Therefore, the optical receiving circuit 51 detects an optical reception interruption due to a failure of the optical receiving circuit 61 or the optical transmitting circuit 62,
The transmission of the optical reception interruption detection signal to the switch control circuit 63 is continued. The switch control circuit 63 sends the optical path switching signal to the optical switch 14 even after sending the optical path switching signal to the optical switch 11 if the optical receiving circuit 51 continues to send the optical reception disconnection detection signal. . When receiving the optical path switching signal, the optical switch 14 switches the optical path of the optical signal from the terminal g to the terminal h. As a result, the optical signal transmitted from the optical fiber cable _{Lnd on} the downstream transmission path passes through the optical switch 14 and passes through the optical switch 11,
The light is converted into an electric signal by the light receiving circuit 51 via the optical switch 13 and is discriminated and reproduced. Thereafter, the optical signal is converted again into an optical signal by the optical transmission circuit 52, and is transmitted to the optical fiber cable _Lnu via the optical switch 13 and the optical switch 12. The optical receiving circuit 51 is an optical fiber cable L
_When the optical signal transmitted from the switch _nd is received, the optical reception disconnection detection signal sent to the switch control circuit 53 is released. The signal is not released, and terminals a to b and terminals g to h, respectively.
Hold the state of switching to.

The optical receiving circuit 51 or the optical transmitting circuit
52 fails and the upstream optical fiber cable L_nuTo
No optical signal is transmitted and the downstream optical fiber cable
Bull L_ndIf no optical signal is transmitted from the
Similarly, the optical fiber cable L of the upstream transmission line_muFrom
The transmitted optical signal has an optical switch 11 and an optical path connected to a terminal e.
Through the interior of the optical switch 13 switched to terminal f.
The optical switch 12 switched from the terminal c to the terminal d;
Via the optical switch 14, an optical signal is converted by the optical receiving circuit 61.
Converted and identified and played. Then, the optical transmission circuit 62
The optical signal is converted again into an optical signal, and the optical switch 14 and the optical switch
Optical fiber cable L via cable 11 _mdSent to
You.

The remote alarm circuit 17 detects a control signal such as a reset signal superimposed on an optical signal transmitted from the optical terminal repeater, and detects switching state information of an optical switch and an alarm generated in the optical repeater 1. This is a circuit for superimposing information on an optical signal and sending it to an optical terminal repeater.

This fault point searching device operates as described above.

Now, the use state of the optical repeater 1 incorporating the above-described fault point searching device will be described.

FIG. 2 is a block diagram showing an optical repeater transmission system to which the present invention is applied, and is for explaining a state in which it operates normally.

As shown in FIG. 2, an optical repeater ₁₁ is connected to the optical terminal repeater 3a via an optical fiber cable L _1u and an optical fiber cable L _1d . The optical repeater 1 _1, optical repeater 1 ₂ via the optical fiber cables L _2u and optical fiber cables L _2d is connected. The optical repeater 1 ₂ optical repeater 1 ₃ are connected via an optical fiber cable L _3u and optical fiber cables L _3d. The optical repeater 1 _3, fiber optic cable L _4u and optical fiber cables L _4d
The optical terminal repeater 3b is connected via the terminal.

The optical signal transmitted from the optical terminal repeater 3a is transmitted to the optical fiber cable _L1u . The optical signal attenuated by the optical fiber cable L _1u is transmitted to the optical repeater _11.
In the optical switch 11 ₁ via the optical switch 13 ₁ is identified reproduced by the optical transceiver board 15 _1, and again optical signal is amplified. The optical signal amplified by the optical repeater 1 ₁ optical switch 13 ₁ is fed through the optical switch 12 ₁ to the optical fiber cable L _2u. Hereinafter, likewise, the optical signal, the optical repeater 1 _2, is relayed by the optical repeater 1 _3, via the optical fiber cable L _4u is received by the optical terminal repeater 3b.

Also transmitted from the optical terminal repeater 3b.
The optical signal is an optical fiber cable L _4dVia optical repeater
Place 1_ThreeSupplied to Optical repeater 1_ThreeAt the optical signal
Is the optical switch 12_Three, Optical switch 14_ThreeVia light transmission
Receiver 16_ThreeReceived at. Optical transceiver 16_ThreeIs the Koshin
Discriminates and reproduces the signal, amplifies it, and converts it back into an optical signal.
14_ThreeGive to. This optical signal is transmitted to the optical switch 14_Three,light
Switch 11_ThreeFiber optic cable L_3dSent to
Get stuck. Hereinafter, similarly, the optical signal is
1_Two, Optical repeater 1₁Relayed by an optical fiber cable
Bull L_1dIs received by the optical terminal repeater 3a via the.

Next, the operation when the optical fiber cable L _3u is disconnected will be described.

FIG. 3 is an explanatory diagram for explaining the operation when the optical fiber cable L _3u is disconnected.

[0033] Here, if the optical fiber cable L _3u is broken, the light receiving circuit 51 of the optical repeater 1 ₃ detects the light reception discontinuity, and sends the optical path switching signal to the optical switch 11 _3. Accordingly, an optical signal transmitted through the optical fiber cable L _4d, the optical repeater 1 ₃ optical transceiver board 16
₃ is again the optical signal after being identified reproduced, supplied to the optical transceiver board 15 ₃ of the uplink through the optical switch 11 within _3. Converted optical signal in the optical transceiver board 15 _3, the optical switch 12 ₃ via the optical fiber cable L _4u is received by the optical terminal repeater 3b.

On the other hand, the optical switch 11 ₃ of the optical repeater 1 ₃
Has been switched, no optical signal is transmitted to the optical fiber cable _L3d . Thereby, the optical repeater 1
Optical transceiver board 16 _{2 2} downlink detects the light reception discontinuity,
And it sends the optical path switching signal to the optical switch 12 _2. Then, the optical switch 12 ₂ of the optical repeater 1 ₂ is switched from the terminal c to the terminal d. From this, the optical fiber cable L
The optical signal transmitted over the _2u is identified reproduced by the optical repeater 1 ₂ optical transceiver board 15 _2. Optical signal converted again by the optical transceiver board 15 ₂ is supplied to the inside of the optical switch 12 ₂ as optical transceiver board 16 ₂ inside. Optical transceiver 16 ₂
Then, the received optical signal is discriminated and reproduced, amplified, and then converted again into an optical signal. Optical signal from the optical transmitting and receiving plate 16 _2, optical fiber cables L _2d, the optical relay device 1 _1, via the optical fiber cable L _1d is received by the optical terminal repeater 3a.

The optical repeater 1_ThreeRemote alarm circuit 17
_ThreeIs the optical switch 11_ThreeThat the optical path of the
Information indicating the optical signal P_dSuperimposed on Similarly, optical repeaters
Place 1 _TwoRemote alarm circuit 17_TwoIs the optical switch 12_TwoLight of
The information indicating that the path is being switched is represented by an optical signal P._uHeavy
Tatami. The optical signal on which this alarm information is superimposed
It is detected by the relay devices 3a and 3b. In the optical terminal repeater 3a
Is the optical repeater 1_TwoOptical switch 12_TwoSwitch the optical path with
Can be monitored and the optical terminal repeater 3b
Is the optical repeater 1_ThreeOptical switch 11_ThreeIs switched
Can be monitored. Therefore, the optical repeater 1_TwoWhen
Optical repeater 1_ThreeOptical fiber cable L between_Threesection
It can be evaluated that a disconnection has occurred.

Next, the operation of the case where the light receiving board 15 ₂ uplink optical repeater 1 ₂ fails.

[0037] FIG. 4 is an explanatory view of the operation of the case where the light receiving board 15 ₂ uplink optical repeater 1 ₂ fails.

[0038] In FIG 4, when the optical repeater 1 ₂ uplink optical transceiver board 15 ₂ has failed, since the optical signal is not sent to the upstream fiber optic cable L _3u, upstream of the optical repeater 1 ₃ detecting light reception discontinuity in the optical transceiver board 15 _3. Accordingly, the optical transceiver board 15 ₃ sends the optical path switching signal to the optical switch 11 _3. Then, the optical signal transmitted through the optical fiber cable L _4d, the optical repeater 1 ₃ of the optical transceiver board 16 _3, passes through the inside of the optical switch 11 ₃ is provided in the optical transceiver board 15 _3. Optical signal from the optical transceiver board 15 ₃ is received through the optical fiber cable L _4u in optical terminal repeater 3b.

On the other hand, the optical repeater 1_ThreeOptical switch 11_Three
Has been switched, the optical fiber cable L_3dTo
No optical signal is transmitted. Thereby, the optical repeater 1
_TwoThe optical transmission / reception board 16 in the downstream direction of the
Switch 12_TwoTo the optical path switching signal. Then
Upstream optical fiber cable L_2uTransmitted from
Optical signal is transmitted to the optical repeater 1_TwoOptical transceiver 1 in the upstream direction
5_TwoOptical switch whose optical path has been switched after
Chi 12_TwoVia the optical transmission / reception board 16 in the downstream direction_TwoSent to
Will be issued. However, the optical transceiver 15_TwoIs out of order
Therefore, the optical transceiver 16_TwoNo optical signal is sent to the
Receiver 16_TwoContinues the light reception interruption. Optical transceiver 16_Two
Is the optical switch 12_TwoAfter sending the optical path switching signal to
If the optical reception interruption detection is continued,
Switch signal to optical switch 13_TwoTo send to. Accordingly
And the optical fiber cable L of the upstream transmission line_2uIs transmitted
The incoming optical signal is transmitted to the optical switch 11_TwoThe light path switches
Optical switch 13_TwoInside the optical switch 12_TwoInside the
Optical transceiver 16 via_TwoIs identified and reproduced. Optical transmission and reception
Panel 16_TwoThe optical signal converted again by the optical switch 1
4_Two, Optical switch 11_TwoVia fiber optic cable
Le L_2dSent to This optical signal is transmitted to the optical repeater 1 ₁,
Optical fiber cable L_1dVia the optical terminal repeater 3
a.

[0040] It should be noted that, in the optical relay device 1 _3, the optical switch 1
Information indicating a state where the optical path of 1 ₃ is switched superimposed on the optical signal P _d by remote alarm circuit 17 _3. Similarly, the optical repeater 1 ₂ superimposes the information representing the state in which the optical path of the optical switch 12 ₂ is switched by a remote alarm circuit 17 ₂ to the optical signal P _u. The information superimposed on this optical signal is
It is detected by the optical terminal relay device 3. In optical terminal repeater 3a, can monitor the light switch 12 ₂ and the optical switch 13 ₂ of the optical repeater 1 ₂ is switched. Also,
In optical terminal repeater 3b, can monitor the light switch 11 ₃ of the optical repeater 1 ₃ is switched. Therefore, it assessment that failure has occurred in the optical repeater 1 ₂ optical transceiver board 15 _2.

In this embodiment, since the optical signal is turned back by the optical switch of the optical repeater 1 which has detected the interruption of the optical reception, the optical signal (laser light) emitted from the broken portion of the optical fiber cable L is transmitted to the human body. There is no irradiation.

Furthermore, conventionally, when optical reception is interrupted, a clock based on an optical signal cannot be extracted. Therefore, each optical repeater 1 has a built-in frequency oscillator having a transmission speed equivalent to that of an optical transmission signal. However, in the present invention, since the optical signal is folded back by the optical repeater 1 in which the optical reception has been interrupted, an expensive frequency oscillator becomes unnecessary, and the number of expensive components can be reduced.
In addition, the cost and power consumption can be reduced.

[0043]

As described above, according to the present invention, when the optical repeater cannot receive the input optical signal, the optical path of the optical signal is switched by the optical switch of the optical repeater, and the switching information of the optical switch is transmitted. Since the monitoring can be performed by the optical terminal repeater, there is an effect that the optical fiber cable disconnection section and the failed optical repeater can be evaluated.

Further, according to the present invention, when the input optical signal is not received, the optical signal is turned back by the optical switch of the optical repeater, so that the optical signal composed of the laser light is emitted from the broken portion of the optical fiber cable. There is an effect that can be prevented.

Further, according to the present invention, since the optical signal is turned back when the reception of the optical signal is interrupted, an expensive and large number of frequency oscillators conventionally used become unnecessary, so that the cost can be reduced and the power consumption can be reduced. Power can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical repeater incorporating a failure point searching device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an optical repeater transmission system to which an embodiment of the present invention is applied.

FIG. 3 is an explanatory diagram illustrating an operation when an optical fiber cable is disconnected in an optical repeater transmission system to which an embodiment of the present invention is applied.

FIG. 4 is an explanatory diagram illustrating an operation when an optical repeater fails in an optical repeater transmission system to which an embodiment of the present invention is applied;

[Explanation of symbols]

 Reference Signs List 1 optical repeater 3a optical terminal repeater 3b optical terminal repeater 11 optical switch (first optical switch) 12 optical switch (second optical switch) 13 optical switch (third optical switch) 14 optical switch (fourth optical Switch) 15 optical transceiver (upward optical transceiver) 16 optical transceiver (downward optical transceiver) 17 remote alarm circuit 51 optical receiving circuit 52 optical transmitting circuit 53 switch control circuit 61 optical receiving circuit 62 optical transmitting circuit 63 switch Control circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 3/46 H04B 10/08 H04B 10/16 H04B 10/17 H04B 17/02

Claims (1)

(57) [Claims] 1. A first optical switch connected to one of an upstream fiber cable and a downstream fiber cable or an internal passage, and a second optical switch connected to another upstream fiber cable and a downstream fiber cable or an internal passage. When the upstream optical signal is amplified, and an upstream optical transmission / reception board that outputs an optical path switching signal upon detecting an optical reception interruption of the upstream optical signal, and when the downstream optical signal is amplified and the optical reception interruption of the downstream optical signal is detected, A downstream optical transmitting / receiving board that outputs an optical path switching signal; and an optical signal from the first optical switch is input to an upstream optical transmitting / receiving board, and an optical signal from the upstream optical transmitting / receiving board is guided to a second optical switch. Or a third optical switch for guiding the optical signal from the first optical switch to the second optical switch by bypassing the upstream optical transmission / reception board. And inputting the optical signal from the second optical switch to the downstream optical transceiver, and guiding the optical signal from the downstream optical transceiver to the first optical switch, or from the second optical switch. A fourth optical switch that guides the optical signal to the first optical switch by bypassing the downstream optical transceiver, and a remote alarm circuit that superimposes information on the optical signal when each optical switch is switched. A fault point searching device provided with: