JPH04127626A - Optical repeater and loopback system - Google Patents

Abstract

PURPOSE:To implement an optical loopback without being synthesized with an optical signal from an opposed line side in the optical repeater of the optical direct amplifier system by switching the mode of the optical repeater to the loopback mode or the output interruption mode and implementing the switching control with a monitoring system signal from a terminal station side. CONSTITUTION:When a loopback instruction is sent from a terminal station via an incoming line L1, the instruction passes through an optical synthesizer 1 and a signal from an optical amplifier 2 is decoded by a control circuit 11 to detect the loopback instruction from the terminal station. That is, the control circuit 11 keeps an optical loop switch 10 to be closed as it is as usual and opens other optical loop switch 9 to be switched to the loopback position, thereby forming the loopback path of optical synthesizer 1 optical amplifier 2 optical branching device 3 optical loop switch 9 optical synthesizer 5 optical amplifier 6 optical branching device 7 optical line switch 8. Thus, the optical relay signal is not converted into an electric signal but amplified directly as the optical signal and the signal is not mixed with the optical signal of the opposed line side.

Description

[Detailed Description of the Invention] [Summary] Regarding an optical repeater and its loopback method, from the viewpoint of miniaturization and low power consumption, an optical repeater signal is directly amplified without converting it into an electrical signal, and is connected to a paired line. The control circuit detects a loopback command from one terminal station from the optical output of the optical amplifier and closes the optical loop switch of that terminal station as usual. Then, the other optical loop switch is opened to form a loopback path, and when the control circuit detects an output cutoff command from the demultiplexed light of the optical demultiplexer, the optical line switch towards the end station is closed. , or the optical amplifier is configured to control the output to be cut off.

[Industrial application field]

The present invention relates to an optical repeater and its loopback system.

In a transmission system between terminal stations via a repeater, it is always important to transmit service signals and monitor the entire system.One of the monitoring methods is to monitor the repeater from the terminal station in order to evaluate failure points. There is a method of looping back through the optical repeater, and it is desirable to be able to apply this loopback method to optical repeaters as well.

[Conventional technology]

Conventionally, as shown in FIG. 6, an optical repeater converts an optical signal into an electrical signal in an optical-to-electrical converter 41. 52 performs various signal processing such as equalization amplification, identification reproduction, monitoring and control, and then returns to the electric-optical converter 43.
．． Optical repeaters of the optical indirect processing type, which convert the signal into an optical signal at 53 and send it out to a transmission line, have come into widespread use.

When looping back an optical repeater using such an optical indirect processing method from, for example, a terminal station on the left side (not shown), for example, an optical demultiplexer 44 . Using the optical multiplexer 50, the optical output from the optical-electrical converter 41 → signal processing circuit 42 → electrical-optical converter 43 is routed to the optical-electrical converter 51 on the paired line side, and the signal processing circuit 51 → electrical- The light is returned from the optical converter 53 to the terminal station.

[Problem to be solved by the invention]

Such a conventional optical repeater converts between an optical signal and an electrical signal, which has the problem of increasing the size of the repeater and increasing power consumption.

Furthermore, when optical loopback is performed using a conventional optical repeater as shown in FIG. When backing up, there is a problem in that a normal loopback signal from the target repeater cannot be monitored unless the optical signal on the paired line is stopped.

Therefore, from the viewpoint of miniaturization and lower power consumption, it is an object of the present invention to directly amplify an optical relay signal without converting it into an electrical signal, and to prevent it from being mixed with the optical signal on the opposite line side. .

(Means for Solving the Problems) In order to achieve the above object, an optical repeater according to the present invention includes:
As shown in principle in FIG. 1, optical multiplexers 1 and 5, optical amplifiers 2.6, optical demultiplexers 3.7, and An optical line switch 4.8 is provided, and an optical loop switch 9.10 is provided between the optical demultiplexers 3 and 7 and the optical multiplexer 5.1 of the paired line. When a loopback command is detected from the terminal station, the optical loop switch on the terminal station side is closed as usual, and the optical loop switch on the opposite terminal station side is opened to form an optical loopback path from the terminal station side. Additionally, a control circuit 11 is provided which closes the optical line switch on the line side to the terminal station only when an output cutoff command from the terminal station is detected.

In addition, in the optical repeater according to the present invention, as shown in principle in FIG. 6, and an optical demultiplexer 37 are provided, and optical loop switches 9, 10 are provided between the optical demultiplexer Fi3.7 and the optical multiplexer 51 of the paired line.
is installed, and when each optical amplifier 2.6 detects a loopback command from one terminal station, the optical loop switch on the terminal station side is closed as usual, and the optical loop switch on the opposite terminal station side is opened. A control circuit 11 is provided to form an optical loop path from the terminal station side, and to turn off the output from the optical amplifier toward the terminal station only when an output cutoff command from the terminal station is detected. I can do it.

In each of the above-mentioned inventions, a light noyantor can be used as each switch. Furthermore, by providing optical attenuators 12 and 13 for the demultiplexed light from each demultiplexer 37, it is possible to match the demultiplexed light to a normal light level.

In addition, in the loopback method according to the present invention using the optical repeater described above, a terminal station sends a loop hack command using a monitoring system signal of a frequency assigned to a predetermined optical repeater, and a terminal station to control Viewed from above, an output cutoff command is sent to the adjacent optical repeater upstream of the optical repeater to be looped back using a monitoring system signal of the assigned frequency.

In this case, a monitoring system signal of a determined frequency is constantly sent to each optical repeater from the terminal station, and by stopping the monitoring system signal, the loopback command or output cutoff command can be issued.

[For production]

In the optical repeater according to the first invention shown in FIG.
When a loopback command is sent from the terminal station via the uplink L1, it passes through the optical multiplexer 1, and the control circuit 11 decodes the signal from the optical amplifier 2. Detect back instruction.

As a result, the control circuit 11 leaves the optical loop switch 10 in the normal closed state, and opens the other optical loop switch 9 to start the loop.

Optical multiplexer 1 → optical amplifier 2 → optical demultiplexer 3
A loop link path can be formed: - optical loop switch 9 -> optical multiplexer 5 - optical amplifier 6 -> optical demultiplexer 7 -> optical line switch 8. Note that the optical line switch 8 remains open except when the output is cut off.

Similarly, in response to a loopback command from the terminal station on the right side of the figure via the downlink L2, the control circuit 11 executes the following commands: optical multiplexer 5 → optical amplifier 6 → optical demultiplexer 7 → optical loop switch 10.
A route of → optical multiplexer 1 → optical amplifier 2 → optical demultiplexer 3 → optical line switch 4 is formed.

However, if this is done alone, the optical output of this optical repeater will be combined with the optical output of the upstream optical repeater, so the terminal station will not be able to disconnect the output from the optical repeater upstream of the optical repeater that has formed the loopback. The command is output.

For example, if the optical repeater that receives this output cutoff command controls the optical repeater on its left to be in a loopback state,
The control circuit 11 closes the optical line switch 8 to prevent the optical output signal from being sent to the adjacent optical repeater on the left, thereby avoiding a superimposed state of optical signals.

In the optical repeater according to the second aspect of the present invention shown in FIG. The control circuit 11 decodes the optical signal demultiplexed by the control circuit 12, thereby detecting a loopback command from the terminal station.

As a result, the control circuit 11 leaves the optical loop switch 10 in the normal closed state, opens the other optical loop switch 9 to switch to the loopback side, and switches the optical multiplexer 1 to the optical Amplifier 2 → Optical demultiplexer 3 → Optical loop switch 9 →
A loopback path of optical multiplexer 5→optical amplifier 6→optical demultiplexer 7 can be formed.

Similarly, in response to a loopback command from the terminal station on the right side of the diagram via the downlink mL2, the control circuit 11 controls the optical multiplexer 5→optical amplifier 6→optical demultiplexer 7→optical loop switch 10.
A route is formed: → optical multiplexer 1 → optical amplifier 2 → optical demultiplexer 3.

Also in this second invention, in order to avoid combination with the optical output of the optical repeater on the upstream side, the terminal station issues an output cutoff command to the optical repeater upstream of the optical repeater forming the loopback. is output.

For example, if the optical repeater that receives this output cutoff command controls the optical repeater on its left to be in a loopback state,
The control circuit 11 controls the optical amplifier 6 to cut off its output so that it does not send the optical output signal to the optical repeater on the left, thereby avoiding a superimposed state of optical signals.

FIG. 3 schematically shows the optical repeater R7 which received the loopback command from the terminal A and the optical repeater R'R+I which received the output cutoff command as described above. Terminal A
No optical signal is sent from the optical repeater R, which is located on the upstream side when viewed from , to the optical repeater R7 to the left, which is controlled to the loopback state, and no optical signal is superimposed on the terminal station A. The item will be sent without any shipping charges.

〔Example〕

FIG. 4 shows an embodiment of the optical repeater according to the present invention shown in FIG.
are a multiplexer (optical coupler) 21.61 that provides pump light to the optical signal from the optical multiplexer 1.5, an erbium-doped optical fiber (EDF) 22.62, and a light beam of this fiber 2262. A demultiplexer (beam splitter) 23.63 that demultiplexes the output, and a photodiode (as an optical-to-electrical converter (0/E) that converts the optical signal of the demultiplexer 23.63 into an electrical signal. AGC which multiplies AGC on the electrical signal of PD) 24.64 and photodiode 24.64.
A circuit 25.65 and a laser diode (
LD) 26°66.

The control circuit 11 also includes a bandpass filter 72.73 for extracting the monitoring signal S■ from the electrical output signal of the photodiode 2464, and receives the monitoring signal Sv from the bandpass filter 72.73. A monitoring circuit that amplitude modulates the optical output of the laser diode 26.
The monitoring circuits 71 and 74 are interconnected, and one of the monitoring circuits 71 includes an optical shutter 9.10 as an optical loop switch and an optical shutter 4 as an optical line switch. It is in charge of controlling 8.

In the normal operation of an optical repeater having such a configuration, for example on the uplink Ll side, optical input is pumped by the optical multiplexer 21 via the optical multiplexer 1, directly amplified, and sent to the optical demultiplexer 2.
3 and 3 and the optical shutter 4, which is normally open, to the transmission path L1. In this case, the bombing effect is
The optical signal demultiplexed by the demultiplexer 23 is sent to the photodiode 24
After the signal is converted into an electric signal, an AGC circuit 25 performs automatic gain control so that the electric output is constant, and is applied to a laser diode 26 as an electric-to-optical converter.

On the other hand, from the electrical output from the photodiode 24, only the monitoring system signal Sv is extracted by the bandpass filter 72 and sent to the monitoring circuit 71, and is optionally dropped to the monitoring circuit 74 on the side of the paired line L2. Additionally, a monitoring signal from the monitoring circuit 74 is inserted and sent to the laser diode 26.

At this time, the input to the laser diode 26 is the AGC
The output of the circuit 25 and the output of the monitoring circuit 71 are combined, but the output of the AGC circuit 25 exhibits a constant level, and the monitoring system signal S from the monitoring circuit 71 is output from the AGC circuit 2.
It is a form in which the constant output of 5 is amplitude modulated.

In such a state, when a loopback command is received from the terminal station, the monitoring circuits 71 and 74 detect this from the monitoring system signal S, and perform control in advance through communication between the monitoring circuits 71 and 74. A monitoring circuit 71, which is defined as a control circuit, opens the optical shutter 9, for example, and maintains the optical shutter 10 in the normal closed state to form a loopback path.

On the other hand, in the optical repeater that receives an output cutoff command from the terminal station, the monitoring circuits 71 and 74 similarly detect the output cutoff command and switch the optical shutter 4 or 8 from the normal open state to the closed state. By controlling the optical shutter 4 or 8, it is possible to block the optical signal from being sent to the optical repeater downstream of the optical shutter 4 or 8.

FIG. 5 shows an embodiment of the optical repeater according to the present invention shown in FIG. 2, and the difference between this embodiment and the embodiment shown in FIG. As can be seen from the difference in the diagram, the optical shutter 4.8 is removed and the AG of the optical amplifier 2.6 is
The optical shutters 27.67 are provided in the C loop, and these optical shutters 27.67 are opened and closed together with the optical shutter 910 by the monitoring circuit 71.74.

That is, an optical repeater that receives a loopback command only opens the optical shutter 9 or ]0 to form an optical loopback path, and an optical repeater that receives an output cutoff command opens the optical shutter 27 or 67. Relayer diode 26.66 by switching control from normal open state to closed state
Since the light emission output from In this case, no optical signal will be sent.

The monitoring system signal SV detected by the monitoring circuit 71.74 is optically transmitted at a different frequency for each optical repeater, and the loop is created by decoding the command code by the monitoring circuit 71.74. This allows it to be determined whether it is a back command or an output cut command. In this case, the monitoring system signal SV
Needless to say, it may be possible to keep the signal S constantly flowing from the terminal side, and to predetermine in advance that only when this monitoring system signal S is interrupted, it will indicate, for example, a loop-happening command or an output cut-off command. .

In addition, instead of closing the optical shutter 27.67 in FIG.
control the laser diode 26 for the pumping light source.
The output light of 66 may be turned off.

Further, in the above embodiment, the optical attenuators 12.13 are replaced by the optical shutters 9. Although it is connected after the IO to adjust the normal light level, the same adjustment can be made even if it is installed before the optical shutter 9.10.

[Effects of the Invention] As explained above, according to the present invention, an optical repeater can be switched to a loopback mode or an output cutoff mode, and this switching control is performed by a monitoring system signal from the terminal side. With this configuration, optical loopback can be performed within the optical direct amplification type optical repeater without being combined with the optical signal from the paired line side, and accurate monitoring of the optical repeater can be realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle configuration of an optical repeater according to the present invention. FIG. 2 is a block diagram of another principle configuration of an optical repeater according to the present invention. FIG. 3 is a block diagram of the principle configuration of an optical repeater according to the present invention. 4 is a block diagram showing an embodiment of the optical repeater according to the present invention shown in FIG. 1; FIG. 5 is a schematic diagram for explaining the loopback method of FIG. FIG. 6 is a block diagram showing an embodiment of the optical repeater according to the present invention. FIG. 6 is a block diagram showing a conventional example. In Fig. 1.2, 1.5... Optical multiplexer, 2.6... Optical amplifier, 3.7... Optical demultiplexer, 4.8... Optical line switch, 9. 10... Optical loop switch, 11... Control circuit, 12.13... Optical attenuator, Ll... Uplink, L2... Downlink. In the figures, the same reference numerals indicate the same or corresponding parts. Principle diagram of the optical repeater of the present invention (Part 2) Figure 3 Embodiment of the present invention (Part 1) Figure 4 Example of the present invention (Part 2)

Claims (6)

[Claims] (1) Optical multiplexers (1) (5) are connected in series along the direction of light in the uplink (L1) and downlink (L2), respectively.
, optical amplifiers (2) (6), optical demultiplexers (3) (7), and optical line switches (4) (8) are provided, and the optical demultiplexers (3) (
An optical loop switch (9) (10) is provided between the optical multiplexer (5) (1) of the paired line and each optical amplifier (2) (6).
When a loopback command is detected from one terminal station, the optical loop switch on the terminal station side is closed as usual, and the optical loop switch on the opposite terminal station side is opened to terminate the optical loop from the terminal station side. An optical repeater comprising a control circuit (11) that forms a back path and closes an optical line switch on the line side to the terminal station only when an output cutoff command from the terminal station is detected. (2) Optical multiplexers (1) (5) are connected in series along the direction of light in the uplink (L1) and downlink (L2), respectively.
, optical amplifiers (2) (6) and optical demultiplexers (3) (7) are provided, and the optical demultiplexers (3) (7) and a paired optical multiplexer (5) are provided.
Optical loop breakers (9) and (10) are installed between each optical amplifier (2) and (6), and when a loopback command from one terminal station is detected from each optical amplifier (2) and (6), the optical loop switch on the terminal station side is By closing the switch as usual and opening the optical loop switch on the opposite terminal side, an optical loopback path from the terminal station is formed, and only when an output cutoff command from the terminal station is detected. An optical repeater characterized in that it is provided with a control circuit (11) that turns off the output of the optical amplifier toward a station. (3) The optical repeater according to claim 1, wherein each switch is an optical shutter. (4) Optical attenuator (12
)(13).The optical repeater according to any one of claims 1 to 3, characterized in that the optical repeater is provided with (13). (5) In the optical repeater loopback method according to any one of claims 1 to 4, a terminal station sends a loopback command using a monitoring system signal of a frequency assigned to a predetermined optical repeater, and also controls the optical repeater. The system is characterized in that an output cutoff command is sent to an adjacent optical repeater upstream of the optical repeater to be looped back using a monitoring system signal of an assigned frequency when viewed from a terminal station. (6) In the optical repeater loopback system according to any one of claims 1 to 4, a monitoring system signal of a frequency assigned to each optical repeater is always sent from the terminal station, and the monitoring system signal is A method characterized in that by stopping the output, the loopback command or output cutoff command is issued.