JPH0473648B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission system, and particularly to a transmission system for meeting information signals in a small capacity optical digital transmission system.

[Prior art]

Generally, in a digital transmission system, it is essential to provide a transmission path for meeting information signals in addition to a transmission path for main data. This meeting information signal is information used for a meeting from the failure point to the terminal station or from the terminal station to the opposite station's terminal station when a failure occurs in a transmission line or repeater of a digital transmission system, and when the failure is repaired. Generally, the transmission path for transmitting this meeting information uses a separate intervening wire within the cable that serves as the transmission path for the main data signal, but in recent years, optical fiber communications have been using metal wires for the purpose of lightning protection, for example. It is common to eliminate the use of intervening lines, and instead use the main data signal transmission path made of optical fiber as the transmission path for meeting information signals. This sharing is accomplished, for example, by adding code violation rules or spare bits to the main data signal, and by separating or combining them from the main data signal at the terminal station.

[Problem that the invention seeks to solve]

As described above, in the conventional transmission system, when a transmission line such as an optical fiber or an intermediate repeater fails, the main data signal is not being transmitted, so the meeting information signal cannot be transmitted either. Therefore, in the conventional transmission method, it is known to provide a line switching device at both end stations and one each for sending and receiving a backup transmission line, but one end station device or intermediate relay device is also required at each end station. It was also very economical, and had drawbacks such as being difficult to put into practical use, especially in small-capacity digital transmission systems that pursue economic efficiency, or subscriber line transport systems that are applied to depopulated areas. .

[Means for solving problems]

In the transmission method according to the present invention, a switching circuit is provided at the input/output point of a transmission line on the transmitting side and a transmission line on the receiving side of a terminal device or an intermediate relay device, and the switching circuits at the input/output points are connected by a switching line. By doing so, it is possible to enable transmission and reception through a common transmission path in the event of a failure in one of the transmission paths.

[Effect]

In this invention, by adding an inexpensive switching circuit to the input/output point of the terminal station, it is possible to transmit only the meeting information even if one of the transmission lines becomes a failure.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the transmission system according to the present invention. In the figure, 1 is a terminal device installed at the end station of the system (hereinafter referred to as A station), 1a is a switching circuit, 1b is an optical-to-electrical conversion circuit, and 1c separates the main data signal and meeting information signal. 1a is the main data input terminal at the A station, 1e is the switching circuit, 1f is the electric-optical conversion circuit, 1g is the coupling circuit, 1h is the main data output terminal at the A station, 1i is the input terminal, 1j
is an output terminal, 1k is a switching line, 2 is a terminal relay device or intermediate relay device installed at an intermediate station of the system (hereinafter referred to as B station), 2a is a switching circuit,
2b is an optical-electrical conversion circuit, 2c is a branch circuit that separates the main data signal and meeting information signal, 2d is a coupling circuit, 2e is an electrical-optical conversion circuit, 2f and 2g are switching circuits, and 2h is an optical-electrical conversion circuit. circuit,
2a is a branch circuit that separates the main data signal and the meeting information signal, 2j is a coupling circuit, 2k is an electric-optical conversion circuit, 2l is a switching circuit, 2m and 2n
is a switching line, 2p is the first input terminal, 2q is the first output terminal, 2r is the second input terminal, 2s is the second output terminal, 2t and 2u are internal transmission lines, and 3 is the end installed at the system intermediate station. A station relay device or an intermediate relay device (hereinafter referred to as C station), 3a is a switching circuit, 3b is an optical-electrical conversion circuit, 3c is a branch circuit that separates the main data signal and the meeting information signal, 3
d is a coupling circuit, 3e is an electric-to-optical conversion circuit, 3f and 3g are switching circuits, 3h is an optical-to-electrical conversion circuit, 3i is a branch circuit that separates the main data signal and the meeting information signal, 3j is a connection circuit, 3k is an electric-optical conversion circuit, 3l is a switching circuit, 3m and 3n are switching lines, 3p is a first input terminal, 3q
is the first output terminal, 3r is the second input terminal, 3s is the second output terminal, 3t and 3u are internal transmission lines, and 4 and 5 are the optical fiber cables connected between A station 1 and B station 2. Transmission lines 6 and 7 are B station 2
and C station 3, 8 and 9 are optical fiber cable transmission lines whose one ends are connected to C station 3, and 10 is an intermediate point of transmission line 7. Indicates the location where the occurrence occurred.

Next, the operation of the transmission system with the above configuration will be explained with reference to FIGS. 2 and 3. first,
To explain the case where there is no failure in the transmission line and the main data signal and the meeting information signal are transmitted smoothly, the main data signal including the meeting information signal is transmitted from the lower station C 3 to B via the transmission line 6. It is input to the switching circuit 2a of station 2. This switching circuit 2a is not switched as shown in FIG. 2 because there is no fault in the transmission path. Therefore, the main data signal including the meeting information signal is input to the optical-to-electrical conversion circuit 2b via this switching circuit 2a, and the optical signal is converted into an electrical signal. This converted electrical signal is input to a branch circuit 2c, and is separated into a main data signal and a meeting information signal by this branch circuit 2c. This meeting information signal is output from the second output terminal 2s. On the other hand, the meeting information signal of the B station is inputted from the first input terminal 2p, combined with the main data signal by the combining circuit 2d, and inputted to the electro-optical conversion circuit 2e. Therefore, after being converted into light by this electrical-optical conversion circuit 2e, it is input to the switching circuit 2f. At this time, the switching circuit 2f is not switched as shown in FIG. 2 because there is no fault in the transmission path. Therefore, the main data signal containing the meeting information signal converted into light is transferred to the switching circuit 2f.
The signal is sent out to the transmission line 4 via. Similarly, A where the main data signal including the meeting information signal is from the upper station.
The signal is input from the station 1 to the switching circuit 2g of the B station 2 via the transmission line 5. This switching circuit 2g is not switched because there is no fault in the transmission path. Therefore, the main data signal including the meeting information signal is sent to the optical-to-electrical conversion circuit 2 via this switching circuit 2g.
h, and the optical signal is converted into an electrical signal. This converted electrical signal is input to the branch circuit 2i,
This branch circuit 2i separates the main data signal and the meeting information signal. This meeting information signal is output from the first output terminal 2q. On the other hand, the meeting information signal of the B station is inputted from the second input terminal 2r, combined with the main data signal by the combining circuit 2j, and inputted to the electro-optical conversion circuit 2k. Therefore, after being converted into light by this electrical-to-optical conversion circuit 2k, it is input to the switching circuit 2l. At this time, the switching circuit 2l is not switched as shown in FIG. 2 because there is no fault in the transmission path. Therefore, the main data signal containing the meeting information signal converted into light is sent to the transmission line 7 via this switching circuit 2f.

Next, the transmission line 7 that now connects B station 2 and C station 3
A case where a failure occurs at the intermediate point 10 will be explained. In this case, the main data signal including the meeting information signal sent from C station 3 is sent to B station 2 via transmission line 6, but since there is no failure in transmission line 6, normal communication is possible. . However, B station 2
The main data signal including the meeting information signal sent from the main data signal cannot be sent to the C station 3 because there is a failure at the intermediate point 10 of the transmission line 7, and communication becomes impossible. Therefore, when sending the main data signal including the meeting information signal from the B station 2 to the C station 3, if an external switching signal is input to the switching circuits 2a and 2l, the switching circuits 2a and 2l will operate as shown in FIG. Can be switched. Therefore, the meeting information signal is combined with the main data signal by the combination circuit 2j of the B station 2, and is input to the electrical-optical conversion circuit 2k. Therefore, the main data signal containing the meeting information signal converted into light by the electrical-to-optical conversion circuit 2k is transferred to the switching circuit 2l as shown in FIG.
Input to the C station 3 via the switching line 2n, the switching circuit 2a, and the transmission line 6. On the other hand, in the C station 3, when external switching signals are simultaneously input to the switching circuits 3f and 3g, the switching circuits 3f and 3g are switched as shown in FIG. Therefore, the main data signal including the meeting information signal inputted to the C station 3 is inputted to the optical-to-electrical conversion circuit 3h via the switching circuit 3f, the switching line 3m, and the switching circuit 3g, as shown in FIG. be able to. In this way, the second
The meeting information signal input from input terminal 2r is C.
It can be transmitted to station 3. Furthermore, when transmitting meeting information from C station 3 to B station 2, the switching circuits 2a and 2l are switched back by an external switching signal, so that the main data signal including the meeting signal from C station 3 is transmitted to C station 2. switching circuit 3f - switching circuit 2a of B station via transmission line 6
Enter. Therefore, this switching circuit 2a
is switched back, so the main data signal including this meeting signal is input to the optical-to-electrical conversion circuit 2b via this switching circuit 2a, and is converted into an electrical signal. Then, this converted electrical signal is input to the branch circuit 2c and branched. Therefore,
The meeting information signal is output from the second output terminal 2s.

Note that the switching circuits 2a and 3f need to alternately repeat transmission and reception, and are connected to the internal transmission lines 2n and 3m, and to the electrical-optical conversion circuit 3e and optical-electrical conversion circuit 2b. Of course, this will be repeated alternately. In addition, in general, the meeting line is 4W.
The transmitting and receiving transmission paths are kept separately.
Ideally, transmitting and receiving signals should be transmitted at the same time, but in the event of a failure in the transmission path, it goes without saying that doing the transmitting and receiving signals in a time-sharing manner does not pose a major problem in practice. be. This can be achieved by detecting loss of input signal or manually.

In addition, the bit rate of the meeting information signal is approximately 2
Simultaneous calls can also be made possible by adopting a so-called ping-pong system in which two-way transmission is performed in a time-division manner.

〔Effect of the invention〕

As explained in detail above, according to the transmission method according to the present invention, inexpensive switching circuits can be added to the input/output points of the terminal stations without adding expensive line switching devices and backup transmission lines to both terminal stations. This makes it possible to provide an economical system configuration that allows only meeting information to be transmitted even if one of the transmission paths becomes impaired. Furthermore, even if the main data cannot be transmitted due to a failure in the transmission path, only communication of meeting information is possible. Therefore, it is particularly effective for small-capacity communication systems or subscriber transport systems targeted at depopulated areas.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the transmission system according to the present invention, and FIGS. 2 and 3 are block diagrams for explaining the operation of FIG. 1. 1... Terminal device (A station), 1a, 1e... Switching circuit, 1b... Optical-electric conversion circuit, 1c...
Branch circuit, 1d...Main data input terminal, 1f...
Electrical-optical conversion circuit, 1g...coupling circuit, 1h...
Main data output terminal, 1i... Input terminal, 1j...
Output terminal, 1k...Switching line, 2...Terminal relay device or intermediate relay device, 2a, 2f, 2g,
2l...Switching circuit, 2b, 2h...Optical-electric conversion circuit, 2c, 2i...Branch circuit, 2d, 2j
...Coupling circuit, 2e, 2k...Electric-optical conversion circuit, 2m and 2n...Switching line, 2p...
First input terminal, 2q...First output terminal, 2r...
Second input terminal, 2s...Second output terminal, 2t and 2u...Internal transmission line, 4 to 9...Transmission line, 10
...midway point.

Claims (1)

[Claims] 1 Superimpose the meeting information signal on the main data signal,
In a transmission method that uses only two transmission paths, one for transmission and one for reception, to transmit the main data signal and the meeting information signal, input/output to the transmission path on the transmission side and the transmission path on the reception side of the terminal device or intermediate relay device. By providing a switching circuit at each input/output point and connecting the switching circuits at these input/output points with a switching line, transmission and reception can be made to communicate through a common transmission path in the event of a failure in one transmission path. Transmission method.