JP2751944B2 - Signal transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission system,
In particular, there is one protection line for N working lines and N to 1
The present invention relates to a signal transmission method for performing switching between signals.

[0002]

2. Description of the Related Art Conventionally, in this type of signal transmission system, when an abnormality occurs in the working line due to deterioration of the working line or line failure, etc.,
The same data string as the working line is transmitted on the protection line to rescue the protection line.If there is no data string to be transmitted on the protection line, the protection line receiving side does not generate an alarm such as reception error. The output data string of the signal generation circuit provided at the protection line sending end is sent out.

In a conventional signal transmission system, as shown in FIG. 2, a frame synchronization circuit 1-1 to 1-N, a signal processing circuit 3-1 to 3-N, and a signal selection circuit 4-1 to 4-N , A fixed clock signal generation circuit 9, a signal generation circuit 7, and a protection line selection circuit 8.

Next, the operation will be described. The frame synchronization circuits 1-1 to 1-N are provided with input data strings 10-1 to 10-N
Frame synchronization is established for frame pulse 2
0-1 to 20-N and data strings 30-1 to 30-N are output. The signal processing circuits 3-1 to 3-N perform signal processing on the data sequence based on the frame pulse, and output the data sequence to the working line and the signal selection circuits 4-1 to 4-N. In the n-th (2 ≦ n ≦ N: natural number) working part signal selection circuit 4-n, the data sequence from the signal processing circuit 3-n and the lower working part signal selection circuit 4- (n + 1) are used. A data string to be transmitted on the protection line is selected from the inputted data strings, and the signal selection circuit 4- (n-
Output to 1). Similarly, the signal selection circuit 4-1 of the first working unit transmits the data string input via the signal processing circuit 3-1 and the signal selection circuit 4-2 of the second working unit via the protection line. A data string to be selected is output to the protection line selection circuit 8. The fixed clock generation circuit 9 is a circuit for generating a clock signal having a frequency unique to the circuit, and outputs the clock signal to the signal generation circuit 7. The signal generation circuit 7 is a circuit that generates a data sequence synchronized with the clock signal input from the fixed clock signal generation circuit 9, and outputs the data sequence to the protection line selection circuit 8. The protection line selection circuit 8
If there is a data string to be transmitted on the protection line due to a failure of the working line, the data string input through the signal selection circuit 4-1 is selected and output to the protection line. Also,
If there is no data to be transmitted on the protection line, a data string output from the signal generation circuit 7 is selected so that an alarm such as reception error does not occur on the protection line receiving side (not shown), Sent to

[0005]

In the above-mentioned conventional signal transmission system, there is a difference between the frequency of the data stream on the working line and the frequency of the data stream output from the signal generation circuit of the protection line sending end. And when the data string transmitted on the protection line is switched from the output data string of the signal generation circuit to the data string of the working line input through the signal selection circuit, or when the working data input through the signal selection circuit is switched. When the data sequence of the circuit is switched to the output data sequence of the signal generation circuit, the response speed follows in the process of absorbing the frequency difference between the two data sequences by the frequency fluctuation absorption circuit (VCO, etc.) on the protection line receiving side. In some cases, an alarm such as a reception error occurred.

[0006] An object of the present invention is to prevent the frequency fluctuation absorbing circuit (VCO or the like) on the receiving side of the protection line from responding sufficiently so that an alarm such as abnormal reception of the protection line does not occur, and transmission on the protection line. It is an object of the present invention to provide a signal transmission method capable of preventing a data string to be transmitted from being asynchronous.

[0007]

According to the signal transmission method of the present invention, a clock signal extracting circuit for extracting a clock synchronized with a transmission line from an input data sequence, and a frame synchronization by establishing frame synchronization of the input data sequence. A frame synchronization circuit that outputs a pulse, and performs signal processing on the data train according to the frame pulse output from the frame synchronization circuit;
A signal processing circuit that outputs the frame synchronization state and the input state of the data string as a control signal from the processing result, and outputs the data string to a working line and a signal selection circuit described below;
N current units including a signal selection circuit for selecting a data sequence from the signal processing circuit or a data sequence input via a signal selection circuit of a lower working unit and outputting the selected data sequence to a signal selection circuit of a higher working unit A clock signal selecting circuit for selecting any one of the N clock signals extracted from each of the working lines based on a control signal output from the signal processing circuit; A clock signal generating circuit for generating a clock signal synchronized with the generated clock signal, a signal generating circuit for generating a data string synchronized with an output clock signal of the clock signal generating circuit, and a signal selecting circuit of the first working unit. And a spare unit including a spare line selecting circuit for selecting the data sequence from the signal generator circuit or the data sequence from the signal generating circuit and sending the selected data sequence to the spare line.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, clock signal extraction circuits 2-1 to 2-
N is a circuit for extracting a clock signal synchronized with the input data sequence 10-1 to 10-N, and outputs clock signals 40-1 to 40-N extracted from each working line. The frame synchronization circuits 1-1 to 1-N are provided with input data strings 10-1 to 10-1.
Frame synchronization is established with respect to 0-N, and frame pulses 20-1 to 20-N and data strings 30-1 to 30-N are output. The signal processing circuits 3-1 to 3-N form a data train 30-1 to 30-N in accordance with the frame pulses 20-1 to 20-N.
30-N, the signal processing is performed, and the frame synchronization state and the input disconnection state of the input data string and the AIS (ALARM IN
DIGITAL SIGNAL) and outputs control signals 50-1 to 50-N, and outputs a data string to a working line and a signal selection circuit 4-1 to be described later.
.. To 4-N.

In the signal selection circuit 4-n of the n-th working part,
Of the data sequence from the signal processing circuit 3-n and the data sequence input through the lower working unit signal selection circuit 4- (n + 1), the data sequence to be transmitted on the protection line is selected, and the upper working unit is selected. To the signal selection circuit 4- (n-1).
Similarly, in the signal selection circuit 4-1 of the first working unit, the signal processing circuit 3-1 and the signal selection circuit 4 of the second working unit are used.
The data stream to be transmitted on the protection line is selected from the data sequence input via the line -2 and output to the protection line selection circuit 8.

Next, in the spare unit, a clock signal selection circuit 5 is a circuit for selecting an arbitrary one of the N clock signals extracted from each working line, and selects and outputs a clock signal synchronized with the working line. . At this time, if the input data string of the working line having the selected clock signal is out of frame synchronization or the input is disconnected or AIS is performed, the extracted clock signal becomes asynchronous with respect to the other working lines. Switching to a clock signal extracted from another working line is performed by a control signal from the signal processing circuit 3. The clock signal generation circuit 6 (for example, VCO) is a circuit that generates a clock signal synchronized with the output clock signal of the clock signal selection circuit 5, and outputs a clock signal synchronized with the working line. The signal generation circuit 7 outputs a data string synchronized with the clock signal of the clock signal generation circuit 5.
When there is a data string to be transmitted on the protection line due to a failure of the working line or the like, the protection line selection circuit 8 selects the data string input via the signal selection circuit 4-1 and outputs the data string to the protection line. . If there is no data to be transmitted on the protection line, a data string synchronized with the working line output from the signal generation circuit 7 is selected and transmitted to the protection line.

[0011]

According to the present invention, the data sequence selected by the protection line selection circuit is always a data sequence synchronized with the working line, and even when the data sequence transmitted on the protection line is switched, the data received by the protection line receiving side is changed. Since the frequency of the row does not change, the frequency fluctuation absorbing circuit (V
(Such as CO) sufficiently follows, and there is no occurrence of an alarm such as an abnormal reception of the protection line. Further, in the present invention, the clock signal selection circuit selects an arbitrary one from a plurality of clock signals, so that the clock signal selected due to input data abnormality of the working line having the selected clock signal is not used. Even when an asynchronous state is established with respect to the working line, the signal generation circuit can be operated with the clock signal extracted from another working line, thereby preventing the data stream transmitted on the protection line from becoming asynchronous. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a conventional signal transmission system.

[Explanation of symbols]

 1-1 to 1-N frame synchronization circuit 2-1 to 2-N clock signal extraction circuit 3-1 to 3-N signal processing circuit 4-1 to 4-N signal selection circuit 5 clock signal selection circuit 6 clock signal generation Circuit 7 Signal generation circuit 8 Protection line selection circuit 10-1 to 10-N Input data sequence 20-1 to 20-N Frame pulse 30-1 to 30-N Data sequence 40-1 to 40-N Extracted clock signal 50- 1 to 50-N control signal

Claims (1)

(57) [Claims] An N (N: natural number) synchronized working line has one protection line, and when a failure occurs in the working line, a data line is transmitted using the protection line. A clock signal extraction circuit for extracting a clock signal synchronized with a transmission line from an input data sequence in a signal transmission method for rescuing a working line, and a frame synchronization for establishing frame synchronization of an input data sequence and outputting a frame pulse. A signal processing unit that performs signal processing on a data stream according to a frame pulse output from the frame synchronization circuit, outputs a frame synchronization state and an input state of the data stream as a control signal from the processing result, and outputs the data stream to a working line and a signal described later A signal processing circuit to output to the selection circuit, and a data string from the signal processing circuit or a signal input through a signal selection circuit of a lower working unit. N working units including a signal selection circuit that selects a data string and outputs the selected data sequence to a signal selection circuit of a higher-order working unit; and N lines extracted by each working line based on a control signal output from the signal processing circuit. A clock signal selecting circuit for selecting any one of the clock signals from the clock signal, a clock signal generating circuit for generating a clock signal synchronized with the clock signal selected by the clock signal selecting circuit, and the clock signal generating circuit And a signal generator for generating a data stream synchronized with the output clock signal of the first and second sections, and a data stream input via the signal selector circuit of the first working unit or a data stream from the signal generator circuit are selected. A signal transmission method comprising a protection unit including a protection line selection circuit for transmitting.