JPH0414816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital relay transmission system. In particular, the present invention relates to a method for preventing failures from spreading to relay transmission lines.

[Conventional technology]

Conventionally, in the digital relay transmission method that uses multiple relays for transmission, if there is a relay section where signal transmission is impossible due to a failure in the regenerative repeater or a break in the transmission cable, etc., subsequent regenerative repeaters will No signal is input. As a result, the output circuit of each repeater is in a non-modulated state, which changes the power consumption.If this continues for a long time, the output circuit that is in a non-modulated state may become a new fault, causing the problem to spread. It's summery. This is a particularly important problem in optical communication type digital regenerative repeaters.

In contrast, the regenerative repeater has a built-in clock signal oscillator that has the same lock frequency as the transmission path, and when the input signal of the regenerative repeater disappears, it can be switched to transmit the output signal of the oscillator. It has been considered to keep the subsequent relay transmission line normal and prevent the spread of failures, but all regenerative repeaters require a stable oscillator, which consumes a lot of power, is expensive, and is not reliable. It was also insufficient in terms of both aspects.

[Problem that the invention seeks to solve]

The present invention aims to provide a relay method that avoids continuous non-modulation of digital repeaters after the point of failure when a failure occurs in a digital transmission path, and prevents the failure from spreading. purpose.

Furthermore, a second aspect of the present invention aims to provide a relay system in which a device for this purpose is utilized for locating a faulty section, thereby facilitating the locating of a faulty repeater.

[Means for solving problems]

A first aspect of the present invention includes a pair of transmission lines whose transmission directions are opposite to each other, and regenerative repeaters inserted in pairs in each of the pair of transmission lines, and the regenerative repeaters include , a digital relay transmission system including a clock signal extraction circuit that regenerates a clock signal from an input signal arriving at the transmission path, and an identification and regeneration circuit that identifies and regenerates the input signal; an input signal detection circuit for detecting the presence or absence of an input signal arriving from the clock signal extraction circuit; a clock signal output terminal to which the output clock signal of the clock signal extraction circuit is connected; and a clock signal input terminal for inputting an externally applied clock signal; The input signal arriving from the transmission path and the signal at the clock signal input terminal are input, and the input signal is controlled by the detection output of the input signal detection circuit, and when the detection output detects the presence of the input signal, the input signal is When the detection output detects the absence of the input signal, the first switching circuit selects the signal of the clock signal input terminal and supplies it to the input of the identification and regeneration circuit, and the clock signal extraction circuit extracts the signal. The output clock signal and the signal at the clock signal input terminal are input, and are controlled by the detection output of the input signal detection circuit, and when the detection output detects the presence of the input signal, the clock signal is extracted by the clock signal extraction circuit. a second switching circuit that selects the clock signal from the clock signal input terminal, and selects the signal of the clock signal input terminal when the detection output detects the absence of the clock signal, and applies the signal to the clock input of the identification and regeneration circuit; The clock signal input terminal and clock signal output terminal are characterized in that signals from a clock signal output terminal and a clock signal input terminal of a pair of regenerative repeaters are connected, respectively.

In a second aspect of the present invention, this device is also used for locating the location of a fault, and the clock signal input terminal and clock signal output terminal are connected to a clock signal output terminal and a clock signal output terminal of a regenerative repeater, respectively. The signal at the input terminal is connected, and an encoding circuit for generating an identification code uniquely assigned to the regenerative repeater is connected between the clock signal input terminal and the input of the first switching circuit. Features.

[Effect]

With the above configuration, when a failure occurs in one direction of a digital signal transmitted bidirectionally, the clock signal extracted from the digital signal transmitted in multiple directions can be used as a new signal source. However, it becomes possible to maintain the relay function of the digital transmission line after the faulty section in a normal state. In addition, a digital code unique to each regenerator is assigned to this clock signal, and the clock signal encoded with this digital code is input to the identification and regeneration circuit, and the code is discriminated at the receiving end. It becomes possible to instantly locate a regenerative repeater whose signal has disappeared.

〔Example〕

FIG. 1 shows a basic embodiment of a relay transmission type regenerative repeater according to the present invention. The output of the equalizing amplifier 2 of the regenerative repeater 1 is input to an input signal detection circuit 3, a switching circuit 4 and a clock signal extraction circuit 5. The output terminal of this clock signal extraction circuit 5 is designated by reference numeral 6 in the drawing. Another output of the clock signal extraction circuit 5 is input to a switching circuit 7. Clock signal input terminal 8 is input connected to switching circuits 4 and 7, respectively. The output of the input signal detection circuit 3 is coupled to the switching circuits 4 and 7 described above.
The outputs of the switching circuits 4 and 7 are connected to the identification reproducing circuit 9.
This regenerative repeater 1 outputs to the regenerative repeater 1 via
It is the output of

Next, the operation of the regenerative repeater circuit of the above embodiment will be described. The input signal of the regenerative repeater 1 is amplified and waveform-equalized by the equalizing amplifier 2, and then sent to the signal detection circuit 3, the switching circuit 4, and the clock signal extraction circuit 5. The output signal of the clock signal extraction circuit 5 is sent to the clock signal output terminal 6 of the regenerative repeater 1 and to the switching circuit 7. The clock signal inputted to the clock signal input terminal 8 is a clock signal obtained from the terminal 6 of the repeater in the opposite direction of the same line, and is inputted to the switching circuits 4 and 7, respectively.

The input signal of the identification regeneration circuit 9 is controlled by the input signal detection circuit 3, and when the signal is normally applied to the regeneration repeater 1, the output signal of the equalization amplifier 2,
It is controlled so that the output signal of the clock signal extraction circuit 5 is input, and operates as a normal digital signal regeneration repeater.

When the input signal of the regenerative repeater 1 disappears, the input signal detection circuit 3 detects the disappearance of the input signal and controls the switching circuits 4 and 7 to switch to the clock signal applied from the clock signal input terminal 8.
At this time, the identification and reproduction circuit 9 identifies and reproduces the clock signal from the switching circuit 4, and sends it out as a digital signal of all "1"s.

In this way, the regenerative repeater whose input signal has disappeared sends out digital signals of all "1", and subsequent regenerative repeaters transmit this signal.

FIG. 2 is a diagram showing the interconnection of a pair of regenerative repeaters in an apparatus according to an embodiment of the present invention. In the regenerative repeater 10, the signal is transmitted from left to right in the figure, and the regenerative repeater 1
1, signals are transmitted from right to left in the figure. Each clock signal output terminal 6 is mutually connected to the clock signal input terminal 8 of the other.

FIG. 3 is a block diagram of a regenerative repeater according to a second embodiment of the present invention. In this device, an encoder 12 is inserted between a clock signal input terminal 8 to which a clock signal is input from the outside and the input of the switching circuit 4. This encoder 12 is set with a code uniquely assigned to this regenerative repeater, and is configured to encode this code into the clock signal inputted from the terminal 8 and provide it to the switching circuit 4.

In this configuration, when the switching circuit 4 selects the signal at the terminal 8, that is, when transmitting the clock signal of the transmission path in the opposite direction, a signal encoded with a unique code is transmitted, and the signal is transmitted from the transmission path. By receiving this signal, it is possible to immediately locate which regenerative repeater is detecting the absence of an input signal.

When the input signal is restored, the input signal detection circuit 3 detects the presence of the input signal and restores the switching circuit 4 to a normal state. Therefore, even if all subsequent regenerative repeaters relay clock signals from the opposite direction immediately after a failure occurs in the transmission path, once a clock signal starts arriving from the previous stage, the regenerative repeater will regenerate to the previous stage. to recover.

〔Effect of the invention〕

As explained above, according to the present invention, even if a failure occurs in the transmission path, the regenerative repeater will not be left unmodulated for a long time, and the failure will spread to the subsequent regenerative repeater. This can be prevented.

Further, according to the second invention, there is an effect that the device for this purpose can be used for locating the location of the obstacle.

The present invention is particularly effective when applied to digital relay transmission lines for optical communications.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a regenerative repeater according to an embodiment of the relay transmission system of the present invention. FIG. 2 is a block diagram of a regenerative repeater forming a bidirectional transmission set in the relay transmission system of the present invention. FIG. 3 is a block diagram of a regenerative repeater according to an embodiment of the present invention including an encoder. 1, 10, 11, 13... Regenerative repeater, 2...
Equalization amplifier, 3... Input signal detection circuit, 4, 7...
...switching circuit, 5...clock signal extraction circuit,
6... Clock signal output terminal, 8... Clock signal input terminal, 9... Identification and reproduction circuit, 12... Encoder.

Claims (1)

[Claims] 1. A pair of transmission lines whose transmission directions are opposite to each other, and a regenerative repeater inserted in pairs in each of the pair of transmission lines, and the regenerative repeater includes: In a digital relay transmission system including a clock signal extraction circuit that regenerates a clock signal from an input signal arriving on the transmission path, and an identification and regeneration circuit that identifies and regenerates the input signal, the regenerative repeater includes a an input signal detection circuit that detects the presence or absence of an incoming input signal; a clock signal output terminal to which the output clock signal of the clock signal extraction circuit is connected; a clock signal input terminal to which an externally applied clock signal is input; The input signal coming from the transmission path and the signal at the clock signal input terminal are input, and the input signal is controlled by the detection output of the input signal detection circuit, and when the detection output detects the presence of the input signal, the input signal is selected. However, when this detection output detects the absence of the input signal, the first switching circuit selects the signal at the clock signal input terminal and supplies it to the input of the identification and regeneration circuit, and the clock signal is extracted by the clock signal extraction circuit. The input signal is a clock signal inputted from the clock signal and the signal from the clock signal input terminal, and is controlled by the detection output of the input signal detection circuit, and when the detection output detects the presence of the input signal, the clock signal extracted by the clock signal extraction circuit a second switching circuit that selects a clock signal, and when the detection output detects the absence of the clock signal, selects the signal of the clock signal input terminal and applies it to the clock input of the identification and regeneration circuit; A digital relay system characterized in that signals from a clock signal output terminal and a clock signal input terminal of a pair of regenerative repeaters are connected to the clock signal input terminal and the clock signal output terminal, respectively. 2 A pair of transmission lines whose transmission directions are opposite to each other, and a regenerative repeater inserted into each of the pair of transmission lines as a pair, and the regenerative repeater receives input coming to the transmission line. In a digital relay transmission system including a clock signal extraction circuit that regenerates a clock signal from a signal, and an identification and regeneration circuit that identifies and regenerates the input signal, the regenerator is configured to detect the presence or absence of an input signal arriving from the transmission path. an input signal detection circuit to detect; a clock signal output terminal to which the output clock signal of the clock signal extraction circuit is connected; a clock signal input terminal to which an externally applied clock signal is input; and an input signal arriving from the transmission path. and the signal of the clock signal input terminal are input, and the input signal is controlled by the detection output of the input signal detection circuit, and when this detection output detects the presence of the above input signal, the above input signal is selected, and this detection output is a first switching circuit which selects the signal of the clock signal input terminal when detecting the absence of an input signal and supplies it to the input of the identification and reproduction circuit; and a clock signal extracted by the clock signal extraction circuit and the clock signal. The signal at the input terminal is input, and when the detection output of the input signal detection circuit detects the presence of the input signal, the clock signal extracted by the clock signal extraction circuit is selected, and the clock signal extracted by the clock signal extraction circuit is selected. a second switching circuit which selects the signal of the clock signal input terminal when the detection output detects the absence of the clock signal and applies the signal to the clock input of the identification and regeneration circuit; Signals from a clock signal output terminal and a clock signal input terminal of a pair of regenerative repeaters are respectively connected to the output terminals, and a signal is connected to the regenerative repeater between the clock signal input terminal and the input of the first switching circuit. A digital relay transmission system characterized by being connected to an encoding circuit that generates a uniquely assigned identification code.