JPH0486131A - Relay transmission system for optical signal - Google Patents

Abstract

PURPOSE:To attain effective relay transmission by allowing an optical repeater to supplement a dummy signal and to send the result when an optical signal is in non- signal state on a transmission line in the relay transmission system of the optical signal. CONSTITUTION:An optical repeater 11 is provided with an optical signal detection signal detection circuit 4, a dummy signal generating circuit 3 and a signal changeover device 5 in addition to an optical receiver 1, a 3R circuit 2 and an optical transmitter 6. The signal changeover device 5 has a function of selectively switching an input to the optical transmitter 6 to an output of the 3R circuit 2 and the dummy signal generating circuit 3 and controlled by the optical signal detection circuit 4. The optical signal detection circuit 4 detects the presence of the optical signal inputted to the optical receiver 1 and outputs a control signal to the signal changeover device 5 so that the signal changeover device 5 is thrown to the position of the 3R circuit 2 when the optical signal is inputted and the signal changeover device 5 is thrown to the position of the dummy signal generating circuit 3 when the optical signal is not inputted. Thus, effective countermeasure such as complete extinct state of the output is attained and a system fault due to interruption of the optical signal is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application The present invention relates to an optical signal relay transmission system. More specifically, the present invention relates to a novel optical transmission system using an optical repeater for compensating for attenuation of optical signals on an optical transmission path in long-distance optical signal transmission.

BACKGROUND OF THE INVENTION A signal transmission system using light as a carrier wave basically consists of a pair of terminal stations, an optical cable that connects these terminal stations, and an optical repeater that is inserted into the optical cable as necessary. That is, when the transmission distance of an optical signal becomes long and the amount of signal attenuation in the optical cable becomes large, the attenuation of the optical signal is compensated for by using an optical repeater.

In a system that transmits digital signals, an optical repeater converts an input optical signal into an electrical signal, and then performs identification and regeneration (Regenerating) and waveform shaping (R).
eshaping) and synchronous playback (Ret im i
The signal is amplified by a so-called 3R circuit that performs ng), is converted into an optical signal again, and is sent out. Furthermore, in systems that handle analog signals, the signal level of an input signal that has been converted into an electrical signal is amplified, and then converted back into an optical signal and sent out.

Note that information regarding the presence or absence of a significant optical signal on an optical transmission line is generally transmitted using a separate line. That is, if the received signal to the optical receiver is lost due to a break in the optical line or line, information about the interruption of signal input is transmitted through the side line.

Problems to be Solved by the Invention In optical transmission systems, optical signal transmission may be interrupted due to unforeseen reasons such as disconnection of an optical fiber cable. Also, in the transmission signal, like packet communication, 1
There may be periods of no signal before and after the significant signal of the group.

In an optical transmission line equipped with an optical repeater as described above, if the transmission of a significant optical signal is interrupted for some reason, the 3R circuit whose input is interrupted outputs an oscillation signal peculiar to a synchronization regeneration circuit. Repeater: Well, an optical signal converted from this oscillation signal is sent out. Furthermore, if the extinction ratio of the optical transmitter of the terminal station or the preceding repeater is degraded, a continuous signal with a low level is input to the optical repeater. In this case as well, the optical repeater amplifies this weak continuous signal, converts it into an optical signal, and sends it out.

When such a failure occurs, the optical signal sent from the optical repeater to the transmission line is nothing but meaningless noise2, but the terminal station that receives this optical signal is able to distinguish it from a regular optical signal. In the end, large noise may be generated in the reproduced signal or a thick edge may result in malfunction.

Therefore, it is an object of the present invention to provide a new relay transmission system for optical signals that can solve the problems of the prior art described above and can effectively cope with the interruption of optical signals.

Means for solving the problem, that is, according to the present invention, includes an optical receiver that converts an input optical signal into an electrical signal, equivalent amplification, timing extraction, and timing extraction of the electrical signal output from the optical receiver. Perform identification playback 3
an optical repeater including an R circuit, an optical transmitter that converts the signal output from the 3R circuit into an optical signal and sends it out, and a transmission side end coupled by the optical fiber cable into which the optical repeater is inserted. In an optical signal relay transmission system constituted by a station and a receiving terminal station, the optical repeater includes an optical signal detection circuit that detects the presence or absence of an input optical signal, and can be clearly distinguished from the transmitted optical signal. A pseudo signal generation circuit that generates a predetermined pseudo signal, and a signal switch that switches the input to the optical transmitter to the pseudo signal generation circuit under the control of the optical signal detection circuit when the input optical signal is in a no-signal state. an optical signal relay, characterized in that the optical signal is configured such that when an input signal to the repeater becomes a no-signal state, an optical signal converted from the pseudo signal is sent to an optical transmission line. A transmission method is provided.

According to an embodiment of the present invention, in the optical signal relay transmission system, a plurality of optical repeaters are inserted into the optical fiber cable, and the optical repeater converts the pseudo signal. It further includes a pseudo signal detection circuit that detects input of an optical signal and controls the signal switching circuit, and when a pseudo signal is input to the repeater, the pseudo signal generated by its own pseudo signal generation circuit is transmitted. An optical signal relay transmission system is provided, characterized in that the converted optical signal is configured to be sent out to an optical transmission line.

The main feature of the optical signal relay transmission system according to the present invention is that the optical repeater has a function of supplementing and transmitting a pseudo signal when there is no optical signal on the transmission path. There is.

In other words, in the conventional relay transmission system, when the input optical signal to the optical repeater becomes a no-signal state or a extinction state, the optical repeater transmits noise to the next stage or terminal station. was there.

On the other hand, in the relay transmission system according to the present invention,
When an input optical signal to a repeater becomes a non-signal state, each optical repeater converts a predetermined pseudo signal generated within itself into an optical signal and sends it out. This pseudo signal is selected in advance so that it can be easily distinguished from the normally transmitted optical signal, and by detecting the pseudo signal, the subsequent optical repeater or receiving end station can enter a no-signal state. It is possible to detect and reliably execute corresponding processing.

Further, according to the method of the present invention, effective relay transmission can be performed even for a transmission method in which a extinction state inevitably occurs, such as a packet signal.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention in any way.

Embodiment FIG. 1 is a diagram showing the basic configuration of an optical repeater used in realizing the optical signal relay transmission system according to the present invention.

The figure shows a pair of optical repeaters 11 and 12 inserted into an optical transmission path formed by an optical fiber cable 10.
It shows.

The optical repeater 11, like a conventional optical repeater, has an optical receiver 1.
．． In addition to the 3R circuit 2 and the optical transmitter 6, it also includes an optical signal detection circuit 4, a pseudo signal generation circuit 3, and a signal switch 5. Here, the pseudo signal generation circuit 3 is configured to be able to generate a predetermined pseudo signal that can be clearly distinguished from a normal transmission signal.

The signal switch 5 has a function of selectively switching the input to the optical transmitter 6 between the output of the 3R circuit 2 and the output of the pseudo signal generation circuit 3, and is controlled by the optical signal detection circuit 4. ing. The optical signal detection circuit 4 detects the presence or absence of an optical signal input to the optical receiver 1, and when an optical signal is input, the optical signal detection circuit 4 detects the presence or absence of an optical signal input to the optical receiver 1. The signal switch 5 is configured so that when the signal is in a no-signal state, the signal switch 5 is input to the pseudo signal generation circuit 3 side.
Outputs a control signal to.

Furthermore, in addition to the configuration of the optical repeater 11, the optical repeater 12 has the following features:
A pseudo signal detection circuit 7 is provided. Pseudo signal detection circuit 7
controls the signal switch 5 together with the optical signal detection circuit 4. That is, the presence or absence of a pseudo signal input to the optical receiver l is detected, and if a pseudo signal is detected, the signal switch 5 switches the pseudo signal to the 3R circuit 2 side. A signal switch 5 is connected so that the signal is input to the signal generation circuit 3 side.
Outputs a control signal to. As a result, when the optical signal detection circuit 4 detects that the input optical signal is in a no-signal state and when the pseudo signal detection circuit 7 detects a pseudo signal, the signal switch 5 switches the pseudo signal generation circuit 3 It is thrown into the side. Note that the optical repeater 12 can be used as is as the optical repeater 11 if you do not mind that the pseudo signal detection circuit 7 is wasted.

The optical transmission line including the optical repeaters 11 and 12 configured as described above functions as follows.

That is, normally, the signal switch 5 of the optical repeater 11.12 is
(b) Both are connected so that the output of the 3R circuit 2 is input to the optical transmitter 6, and operates in exactly the same way as an optical repeater on a boat.

Here, if for some reason the optical signal becomes a no-signal state on the optical transmission path before the optical repeater 11, the optical signal detection circuit 4 of the optical repeater 11 detects the no-signal state from the optical receiver 1. is detected, and the signal switch 5 is turned on to the pseudo signal generation circuit 3 side. Therefore, the pseudo signal is converted into an optical signal and sent out from the optical repeater 11.

When the optical repeater 12 receives the pseudo optical signal, the pseudo signal detection circuit 7 detects this and switches the signal switch 5 to the pseudo signal generation circuit 3 side. Therefore, the optical repeater 12 also sends out an optical signal obtained by converting the pseudo signal.

Thereafter, the subsequent optical repeater repeats the same operation as the optical repeater 12, and ultimately a pseudo signal is transmitted to the receiving terminal station. By detecting the pseudo signal, the receiving terminal station can take effective measures against the no-signal state, such as suspending subsequent signal processing.

In addition, due to reasons such as disconnection of the optical fiber cable,
When an optical signal is interrupted between the optical repeater 11 and the optical repeater 12, the optical signal detection circuit 4 of the optical repeater 12 detects the no-signal state and sends a pseudo signal to the subsequent optical transmission line. Send out.

As an example, when transmitting a digital optical signal with a transmission rate of 125 Mbit/sec, a predetermined signal with a transmission rate of 3 Mbit/sec can be used as the pseudo signal. In this case, 125 to 1 bit/se
When the optical signal c is interrupted, the optical signal detection circuit is activated and the signal sent to the next stage becomes a 3 Mbit/sec pseudo signal. In the next stage, the pseudo signal detection circuit is 3Mb/s
When the ec signal is detected, the next stage Δ sends out a new pseudo signal. Note that the pseudo signals output from each optical repeater may be different from each other. Further, as the pseudo signal, a signal in an extinction state, that is, a signal having a transmission rate of OMbit/sec may be used.

FIG. 2 is a diagram showing a configuration example of an optical transmission system configured using the optical repeater shown in FIG. 1 and its operation.

As shown in the figure, in this optical transmission system, n optical repeaters 1 are connected to an optical transmission line constituted by an optical fiber cable connecting a transmitting side terminal station 21 and a receiving side terminal station 22.
1.12...The optical repeaters 11 and 12 have the same configuration as the optical repeaters 11 and 12 shown in FIG. Repeater 1
The optical repeaters after 2 basically have the same configuration as the optical repeater 12. However, at least only the optical repeater 10 is configured to output the extinction state as a pseudo signal.

The optical relay transmission system configured as described above operates as follows.

First, as shown in waveform (a) in FIG. 2, from the transmitting side, a 125 Mb
A group of it/see optical signals are sent out. Optical repeater 1
1 detects the no-signal state before and after this optical signal, converts the pseudo signal of, for example, 3 Mbit/sec into an optical signal, and outputs an optical signal having a waveform Q)). Hereinafter, the optical repeaters after the optical repeater 12 detect pseudo signals and send out pseudo signals such as waveform (C) generated by their own pseudo signal detection circuits to the next stage. The optical repeater 1n detects the pseudo signal sent from the preceding optical repeater, and converts the waveform (
d) Regenerate the OMbit/sec optical signal, ie, the extinction state. Therefore, the same optical signal as the optical signal output from the transmitting terminal station is transmitted to the receiving terminal station 22.As described in detail of the invention, in the relay transmission system according to the present invention, the optical repeater has a function of sending out a pseudo signal when the input optical signal becomes a no-signal state. Therefore, by detecting this pseudo signal at the next stage repeater or terminal station, it is possible to take effective measures such as completely quenching the output, thereby preventing system failures caused by optical signal interruption. becomes possible.

In addition, even in packet signal transmission where the signal to be transmitted includes a completely extinction state, a pseudo signal is transmitted during extinction, so the receiving end station or the last repeater converts the pseudo signal into a completely extinction state. By doing so, it is possible to maintain normal system operation. That is, relay transmission of packet signals can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of an optical repeater used in the relay transmission system according to the present invention, and FIG. 2 is a diagram illustrating a specific example of the relay transmission system according to the present invention. It is. 11.12...Signal switcher, 13...Pseudo signal detection circuit, 15.16.17...Optical repeater,

Claims (2)

[Claims] (1) An optical receiver that converts an input optical signal into an electrical signal, a 3R circuit that performs identification and regeneration, waveform shaping, and synchronous regeneration of the electrical signal output from the optical receiver, and a 3R circuit that converts the signal output from the 3R circuit. An optical system consisting of an optical repeater equipped with an optical transmitter that converts into an optical signal and sends it out, and a transmitting end station and a receiving end station connected by the optical fiber cable into which the optical repeater is inserted. In the signal relay transmission system, the optical repeater includes an optical signal detection circuit that detects the presence or absence of an input optical signal, and a pseudo signal generation circuit that generates a predetermined pseudo signal that can be clearly distinguished from the transmitted optical signal. and a signal switcher that switches the input to the optical transmitter to a pseudo signal generation circuit under the control of the optical signal detection circuit when the input optical signal is in a no-signal state, and the input signal to the repeater is in a no-signal state. 1. An optical signal relay transmission system, characterized in that, when a state occurs, an optical signal obtained by converting the pseudo signal is sent to an optical transmission path. (2) In the optical signal relay transmission system according to claim 1, a plurality of optical repeaters are inserted into the optical fiber cable, and the optical repeater transmits the optical signal converted from the pseudo signal. The device further includes a pseudo signal detection circuit that detects an input and controls the signal switching circuit, and when a pseudo signal is input to the repeater, a light signal that is converted from the pseudo signal generated by the repeater's own pseudo signal generation circuit is provided. An optical signal relay transmission system characterized in that the signal is configured to be sent out to an optical transmission line.