JP2737761B2 - Digital transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital transmission apparatus, and more particularly, to a digital transmission apparatus using optical transmission and wireless transmission.

[0002]

2. Description of the Related Art Conventionally, an apparatus shown in FIG. 2 is known as a digital transmission apparatus using an optical transmission system and a wireless transmission system. Referring to FIG. 2, the illustrated digital transmission apparatus includes a transmission end A and a reception end B, and also includes a wireless transmission unit (wireless transmission system) 11 and an optical transmission unit (optical transmission system) 12. The input signal (digital input signal) given to the transmitting end A is distributed to the wireless transmission system 11 and the optical transmission system 12 by the signal distribution circuit 13.

[0003] In the wireless transmission system 11, an input signal is transmitted as a wireless signal, that is, by radio waves, and given to a reception switching circuit 14. On the other hand, the optical transmission system 12 transmits an input signal as an optical signal and supplies the optical signal to the reception switching circuit 14. In a normal case, the reception switching circuit 14 supplies an optical signal to the receiving end B.

In the optical transmission system 12, when a failure occurs in the optical transmission system itself, a device failure signal is transmitted. When the control device (not shown) receives the device failure signal, it generates a switching signal and supplies the switching signal to the reception switching circuit 14. Thus, the reception switching circuit 14 supplies a radio signal to the receiving end B.

As described above, the conventional digital transmission apparatus has an active transmission system (optical transmission system) and a standby transmission system (wireless transmission system), and switches to the standby transmission system when a failure occurs in the active transmission system. To prevent signal interruption.

[0006]

However, in the conventional digital transmission device, only the failure of the active transmission system is detected and the transmission path is switched to the backup transmission system. When a failure occurs, for example, when the power supplied to the signal distribution circuit is cut off, the input signal is not supplied to both the working transmission system and the protection transmission system, and the line is disconnected. There is a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a digital transmission apparatus which does not become disconnected when a failure occurs in a signal distribution circuit.

[0008]

According to the present invention, there is provided an optical transmission unit having a transmitting end and a receiving end, used as a working line, for transmitting a digital signal from the transmitting end to the receiving end as an optical signal; A digital transmission device having a wireless transmission unit that is used as a protection line and transmits the digital signal as a wireless signal to the reception end, wherein a first switching circuit connected to the transmission end and an optical transmission unit A second switching circuit, and the digital signal connected to the first and second switching circuits and supplied through the first switching circuit to the optical transmission unit and the second switching circuit. The first switching circuit selectively connects the transmitting end to the signal distribution circuit and the second switching circuit, and the second switching circuit connects the optical transmission unit. Selective A reception switching circuit that is connected to the signal distribution circuit and the first switching circuit, and further selectively connects the optical transmission unit and the wireless transmission unit to the reception end; First control means for controlling the reception switching circuit to connect the wireless transmission unit and the reception end when an error occurs, and the first and second switching circuits when a failure occurs in the signal distribution circuit And a second control unit for directly connecting the transmitting end and the optical transmission unit by controlling the digital transmission device.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Referring to FIG. 1, here, the same components as those of the digital transmission apparatus shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. The illustrated digital transmission device includes first and second switching circuits 15 and 16. The first switching circuit 15 is connected to the transmission terminal A and connected to the signal distribution circuit 13 and the second switching circuit 16. Have been. The second switching circuit 16 is connected to the signal distribution circuit 13 and the optical transmission system 12.

In a normal case, the transmitting end A and the signal distribution circuit 13 are connected by a first switching circuit 15, and the signal distribution circuit 13 and the optical transmission system 1 are connected by a second switching circuit 16.
2 are connected. Therefore, the input signal from the transmitting end A is distributed to the wireless transmission system 11 and the optical transmission system 12 by the signal distribution circuit 13.

When a failure occurs in the optical transmission system 12,
The control device generates a switching signal in response to the device failure signal and supplies the switching signal to the reception switching circuit 14. The reception switching circuit 14 connects the wireless transmission system 11 and the receiving end B in response to the switching signal.

On the other hand, when a failure occurs in the signal distribution circuit 13 (for example, when a power failure occurs in the signal distribution circuit 13), the power failure is detected by the control device, and the control device operates the first and second switching circuits. A switching signal is sent to 15 and 16. Thus, the transmitting end A and the optical transmission system 12 are directly connected by the first and second switching circuits 15 and 16, and the input signal is transmitted from the transmitting end A to the first and second switching circuits 15 and 16. Optical transmission system 1 directly via
2 will be given.

[0014]

As described above, according to the present invention, when a failure or the like occurs in the signal distribution circuit, the transmission end to which a digital signal is applied is directly connected to the optical transmission unit. Even if the power supply becomes unavailable due to a power failure, the supply of digital signals will not be interrupted.
There is an effect that a line disconnection state can be avoided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a digital transmission device according to the present invention.

FIG. 2 is a block diagram illustrating an example of a conventional digital transmission device.

[Description of Signs] 11 Wireless transmission system 12 Optical transmission system 13 Signal distribution circuit 14 Reception switching circuit 15 First switching circuit 16 Second switching circuit

Claims (1)

(57) [Claims] An optical transmission unit comprising a transmitting end and a receiving end, used as a working line, for transmitting a digital signal from the transmitting end as an optical signal to the receiving end, and wirelessly transmitting the digital signal used as a protection line. A digital transmission device having a wireless transmission unit for transmitting a signal to the reception end; a first switching circuit connected to the transmission end;
A second switching circuit connected to the optical transmission unit;
And a signal distribution circuit connected to the second switching circuit and distributing the digital signal provided through the first switching circuit to the optical transmission unit and the second switching circuit. A first switching circuit selectively connects the transmitting end to the signal distribution circuit and the second switching circuit, and the second switching circuit selectively connects the optical transmission unit to the signal distribution circuit and the first switching circuit. Connected to the switching circuit of
A reception switching circuit for selectively connecting the optical transmission unit and the wireless transmission unit to the reception terminal; and controlling the reception switching circuit when a failure occurs in the optical transmission unit to control the wireless transmission unit and the reception terminal. And a first control unit for connecting the transmission end and the optical transmission unit by controlling the first and second switching circuits when a failure occurs in the signal distribution circuit. A digital transmission device comprising: a second control unit.