JPH0317421B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to transmission line monitoring and control of digital communication equipment. In particular, the present invention relates to a digital communication device that transmits a supervisory control signal superimposed on a main signal.

[Conventional technology]

Traditionally, in relay transmission methods such as optical communication, wireless communication, and coaxial cable communication, supervisory control signals used for maintenance and testing of these communication devices are transmitted in addition to the main signal to be transmitted from the transmitting side to the receiving side. Various methods are known. For example, in coaxial cable communications, high-speed main signals are transmitted over the coaxial cable, and low-speed supervisory control signals are transmitted over the intervening pair of copper wires. Furthermore, in the optical communication system, the main signal is transmitted through an optical fiber, and the supervisory control signal is transmitted using a copper-interposed pair inserted into the same optical cable.

These methods require copper intervening pairs for the transmission of supervisory control signals, and are generally disadvantageous from an economic point of view. In addition, in the case of optical cables, if a copper intervening pair is provided, the fineness of the optical fiber itself cannot be utilized;
The cable becomes thick and heavy. In addition, copper-interposed pairs are susceptible to electromagnetic induction noise, resulting in problems such as poor transmission quality of supervisory control signals. Instead of the copper intervening pair, it has been considered to insert a separate optical fiber into the cable for supervisory control, but this is economically disadvantageous due to poor transmission efficiency.

On the other hand, in wireless communication systems, a so-called composite modulation or superimposition modulation system is known in which the carrier wave amplitude of a main signal is modulated by a supervisory control signal. FIG. 2 is a time chart showing such a conventional supervisory control signal transmission form. Information series a is I ₁ , I ₂ ,...I ₅
This information sequence is complex-modulated by the supervisory control signal b. In general, wireless communication systems transmit digital signals obtained by phase-modulating or frequency-modulating carrier waves, so the amplitude of the envelope is constant. If this is amplitude-modulated by the supervisory control signal b, a composite modulation waveform as shown in FIG. 1c is obtained. On the receiving side, the original supervisory control signal can be extracted by passing the envelope of the composite modulated waveform through a low-pass filter.

Although it is possible to transmit a supervisory control signal by such composite modulation of a carrier wave signal, it deteriorates the bit error rate characteristics of the main signal, and in order to avoid this, it is necessary to increase the output power.

For this reason, a method of converting the speed of a digital signal with a frame structure in a digital wireless communication system, modulating the unmodulated wave region between the frame signals with a supervisory control signal, and transmitting the supervisory control signal by superimposing it on the main signal. has been proposed (Japanese Patent Application Laid-Open No. 58-170240
(Patent Publication) [Problems to be Solved by the Invention] This method has the excellent advantage that the supervisory control signal can be superimposed on the main signal and transmitted over the same transmission path.

Incidentally, since the error rate of a transmission path is usually extremely low, 10 ^-11 or less, it is so low that errors in the main signal are almost undetectable. Therefore, it is difficult to easily detect the deterioration of the code error rate of the main signal by measuring the error rate of the main signal as the characteristics of the transmission path change over time.

It is desirable to detect the deterioration state of the device at an early stage before the error rate of the transmission path, which has such an extremely low code error rate of the main signal, deteriorates.

The present invention has been made in response to the above-mentioned requirements, and an object of the present invention is to provide a method that can detect equipment deterioration at an early stage by measuring the error rate of an auxiliary code based on the state of a transmission path.

[Means to solve the problem]

The present invention inserts a small number of auxiliary codes into the digital signal sequence of the main signal to be transmitted, and modulates the amplitude of the auxiliary codes by variably controlling the degree of modulation using a supervisory control signal. It is characterized by detecting the bit error rate.

That is, the present invention includes a transmitting device and a receiving device that receives an output signal of the transmitting device, and the transmitting device has a terminal to which a main signal is input, a terminal to which a supervisory control signal is input, and a terminal to which the supervisory control signal is input. a transmitting means for inserting a signal into the main signal to produce the output signal; the receiving device includes a receiving means for separating the main signal and the supervisory control signal from the output signal; In the digital communication device, the transmitting means inserts an auxiliary code into the digital code sequence of the main signal. means for generating a high-speed digital code sequence; and means for amplitude modulating the auxiliary code using the supervisory control signal;
The amplitude modulating means includes means for variably controlling the degree of modulation to increase the bit error rate of the auxiliary code, and the receiving means converts the auxiliary code from a high-speed digital code sequence into which the auxiliary code is inserted. , means for amplitude-detecting the auxiliary code extracted by this means to obtain the separated supervisory control signal, and code error monitoring means for detecting a code error in the separated supervisory control signal. It is characterized by

Preferably, the transmitting means includes means for inserting an error detection code into the main signal to be transmitted, and the receiving means preferably includes means for monitoring errors in the received main signal using the error detection code.

[Effect]

The transmitter converts the speed of the main signal train and inserts a small number of auxiliary codes into the main signal train. Amplitude modulation is performed only on this auxiliary code to transmit supervisory control information. The receiving device extracts this auxiliary code, detects its amplitude, and obtains supervisory control information. Therefore, the influence of the supervisory control information does not appear on the main signal.

In addition, since the auxiliary code is susceptible to transmission path deterioration and is amplitude modulated to increase the code error rate, the error rate of this auxiliary code is detected to detect transmission path deterioration at an early stage.

〔Example〕

FIG. 1 is a diagram illustrating the insertion of an auxiliary code and its amplitude modulation on the transmitting side and the extraction of the auxiliary code on the receiving side, which are performed in the present invention.

This figure shows an example applied to a digital communication device for optical communication.

The upper part of FIG. 1 shows a transmitter, and the lower part shows a receiver. The main signal to be transmitted is input from terminal 1. A supervisory control signal is input from terminal 2. The main signal is a multiplexed high speed digital signal. The supervisory control signal has a smaller amount of information than the main signal and is a considerably slower signal. This monitoring control signal is a signal for controlling the monitoring data of the transmission path and the terminal station necessary for transmitting the main signal.

The main signal inputted from the terminal 1 is speed-converted by the transmission code conversion circuit 3 and inputted to the light source drive circuit 4 .
The transmission code conversion circuit 3 adds auxiliary codes to the main signal at predetermined intervals, and outputs a signal whose speed is slightly higher than that of the main signal input to the terminal 1.
The output of this light source drive circuit 4 is output from adder circuits 5 and 6.
The light is supplied to the light source 8 via. The optical output of this light source 8 is supplied to a transmission output terminal 10. A part of this light output is detected by a photodetector 9 and given to an automatic output control circuit 7, where it is automatically controlled so that the average output power of the light source 8 is constant. The control output of this automatic output control circuit 7 is applied to an adder circuit 6.

The optical signal output from the transmission output terminal 10 reaches a reception input terminal 31 of a distant receiving device via an optical fiber transmission line 30. This optical signal is detected by a photodetector 32 and converted into an electrical signal, and the electrical signal is amplified by an amplifier 33. This output is input to a waveform equalizer 34. This amplifier 33 is provided with an automatic gain control circuit 35, and is controlled so that its output signal level is constant. Waveform equalizer 3
The output of No. 4 is identified by a discriminator 36. A timing signal necessary for this discriminator 36 is extracted by a timing signal extraction circuit 40. The output of the discriminator 36 is sent to the reception output terminal 38 via the reception code conversion circuit 37.
sent to. In this reception code conversion circuit 37,
The auxiliary code added by the circuit 3 of the transmitting device is deleted, and the signal corresponding to the signal input to the terminal 1 and the speed signal are outputted.

Here, in FIG. 1, the part surrounded by the dashed line is a configuration in which the transmitting device modulates the auxiliary code with the supervisory control signal and superimposes it on the main signal, and the receiving device extracts the supervisory control signal. That is, in the transmitter, the block synchronization circuit 12 detects the above-mentioned auxiliary code from the output signal of the transmission code conversion circuit 3, and the AND gate 13, the differential amplifier 16, and the gate circuit 18
This auxiliary code is subjected to amplitude modulation using the monitoring control signal at terminal 2. In the receiving device, the differential circuit 4
2, the output 41 of the discriminator 36 and the waveform equalizer 34
The difference between the signal and the output 39 is taken, the output is rectified by a full-wave rectifier circuit 44, and a monitoring control signal is outputted to a terminal 47 by a low-pass filter 46.

In the device configured in this way, the supervisory control signal can be transmitted without causing any deterioration to the main signal, as shown in the operating waveform time chart of FIG. FIG. 3a shows the input main signal of the transmitter, which is composed of a code sequence of 4 bit blocks indicated by _I1 to _I4 . In the transmission code conversion circuit 3,
An auxiliary code indicated by _I5 is inserted into each 4-bit block. This auxiliary code is conventionally used as a parity check code, a negotiation code between transmitting and receiving end stations, or a timing information code.

The block synchronization circuit 12 detects the auxiliary code insertion position, and its output has the waveform shown in FIG. 3c. The signal at terminal 2 is the supervisory control signal d to be transmitted.
When the code sequence b to be transmitted and the block synchronization pulse c are applied to the inputs of the AND gate 13, the output is from the terminal 14 to the resistor R to the terminal 1 when _I5 is a mark.
A current path of 5 is formed, and an amplitude of -Δ is taken out at the inverted differential amplifier output 17. one-sided sign
When I ₅ is a space, a reverse current path is formed from the terminal 15 to the resistor R and the terminal 14, and an amplitude of +Δ is taken out to the inverting differential amplifier output 17.
Only when the waveform of the supervisory control signal input terminal 2 is a mark and the block period pulse waveform is a mark, the gate circuit 18 is opened and its output is added to the output of the light source drive circuit 4 by the adder circuit 5.
The output is as shown in Figure 3e. In other words, when the auxiliary code is a mark due to the supervisory control signal, 1-△;
When the auxiliary code is a space, a code string subjected to amplitude modulation of Δ is obtained.

In the receiving device, when the amplitude modulation degree Δ is small, almost no error occurs in the output of the identification circuit 36, and a waveform as shown in FIG. 3f is obtained. Since the waveform input to the identification circuit (output of the waveform equalizer 34) is the waveform shown in FIG. When this waveform is rectified by the full-wave rectifier circuit 44, the waveform shown in FIG. become.

As explained above, this circuit can transmit the supervisory control signal without affecting the transmission characteristics of the main signal. Furthermore, even in the case of digital signals, it is possible to transmit supervisory control signals without performing special code conversion.

In addition, in the configuration shown in FIG. 1, the case where there is no repeater in the middle has been explained, but with the repeater in the middle,
By using the receiving circuit 51 and the transmitting circuit 50 shown by broken lines in FIG. 1, it is possible to transmit supervisory control signals between each repeater. That is, when a repeater is provided in the middle, a device consisting of a pair of two blocks 50 and 51 shown in broken lines in FIG. 1 is used, the output of terminal 48 is connected to the input of terminal 49, and
By connecting the output of 7 to the input of terminal 1,
You can create an intermediate repeater.

In addition, in the explanation of FIG. 1, the example of the circuit is shown in which the auxiliary code can randomly take the value of a mark or a space, but if the auxiliary code is limited to only one of the marks and spaces, the gate circuit 18 Since the input 17 only needs to generate a -Δ or +Δ waveform, the AND gate 13 and the inverting amplifier 16 are unnecessary.

In addition, in the explanation of Fig. 1, the full-wave rectifier circuit 4 is
4 was used, but if the rectification efficiency is ignored, the same effect can be achieved by constructing a half-wave rectifier circuit.

In addition, in the explanation of FIG. 1, the block synchronization circuit 12 on the transmitting side obtains block synchronization from the output of the transmission code conversion circuit 11, but at the terminal station,
If the block synchronization waveform generated by the transmission code conversion circuit is directly used, the block synchronization circuit 12 can be omitted.

Examples of the present invention will be described.

In general, almost no transmission errors occur on a transmission path, and the error rate is less than 10 ^-11 , and it takes a long time to measure the error rate. On the other hand, in amplitude modulation, it is known that as the S/N ratio worsens, the error rate decreases.

The present embodiment utilizes this principle, and transmits the auxiliary code with a small amplitude, and intentionally sets the error rate to be high, and monitors the error rate of the auxiliary code on the receiving side. The measurement of the error rate of the transmission path can be extremely shortened, and its deterioration can be detected at an early stage.

When the same logical value appears consecutively in the transmitted code,
The point where the sign changes cannot be detected, and the transmitting side may not be able to correctly detect signal synchronization. To solve this problem, the transmitting side performs code conversion on the signal according to a certain law to increase the number of signal change points, and the receiving side performs the inverse conversion of this law to reproduce the original signal.Transmission line code Conversion methods are known. An example of such a transmission line code is mB1C (m binary with 1 complement
insertion) code or DmB1M (differenten-tial)
There are m binary with 1 mark insertion) codes, and embodiments of the present invention for these codes are shown.

FIG. 4 is a block diagram of the apparatus according to the first embodiment of the present invention. FIG. 5 is a time chart of the transmitting device to explain its operation, and FIG. 6 is a time chart of the receiving device.

This example is for the case where m=4, and for the input symbols I ₁ , I ₂ , I ₃ , I ₄ shown in FIG. 5a,
The output of the transmission code conversion circuit 3 is converted into a block of five time slots as shown in the waveform of FIG. 5b, and the code _I5 following the input codes _I1 , _I2 , _I3 , and _I4 is:
The value I ₅ = ₄ is inserted as an auxiliary code in the case of mB1C code and DmB1M code.

In the transmitting device of FIG. 4, the block synchronization pulse shown in FIG.
When a supervisory control signal such as the waveform of FIG. 5d is applied to terminal 2, the waveform of the light source output 8 will be as shown in FIG. 5j. That is, the amplitude of the auxiliary code inserted by the transmission code conversion device 3 becomes a waveform modulated by the supervisory control signal to an amplitude of 1-Δ when it is a mark, and to an amplitude of Δ when it is a space.

In the receiving device, one of the outputs of the waveform equalizer 34 is guided to the discriminator 36, as well as to the delay element 54 and the difference circuit 55. Since the output waveform of the waveform equalizer 34 is as shown in FIG. 6j, the output of the delay element 54 for 1/2 time slot is as shown in FIG. 6k.
Therefore, the difference circuit 55
The waveform output 56 obtained by taking the difference between the two is as follows.
It will look like Figure 6l. By passing this waveform through the double-wave rectifier circuit 44, the waveform shown in FIG.
sent to.

On the other hand, the waveform identified by the discriminator 36 is as shown in FIG. 6n, and the code delayed by one time slot in the delay circuit 61 is as shown in FIG. 6o. Therefore, when there is no code error, the waveform passed through the exclusive OR gate 62 becomes as shown in FIG. 6P, and one mark code appears in five time slots. The block synchronization circuit 12 detects this mark code and generates a block synchronization pulse waveform as shown in FIG. 6q. By detecting a mismatch between this block synchronization pulse and the output of the exclusive OR gate 62 using the AND gate 66, a code error in the auxiliary code being transmitted can be detected. A code error pulse output is obtained on the signal line 70. Block synchronization circuit 1
The output of 2 is led to a gate circuit 64, which opens the gate only during the period when the block synchronization pulse is occurring.
The pulse shown in FIG. 6 r is extracted from the output of the double-wave rectifier circuit 44 (FIG. 6 m) and guided to a low-pass filter 46 .
The output waveform of the low-pass filter 46 is as shown in FIG. 6s. By passing this through the inverting amplifier 65, the supervisory control signal output 47 as shown in FIG. 6i is reproduced.

In the intermediate relay device, the output 63 of the block synchronization circuit 12 may be connected to the terminal 51 in the same manner as in the previous example using the circuit surrounded by the broken line in FIG.

The system using the mB1C code or DmB1C code enables the transmission of the supervisory control signal by modulating the auxiliary code inserted in the transmission code conversion circuit, and has the advantage of not affecting the main signal information. Also, in FIG. 4, on the receiving side, a delay element 54, a rectifier circuit 44, a tank circuit 59, a limiter amplifier 60
The circuit constituted by is a component of a timing generation circuit necessary for reproducing timing waves regardless of whether a supervisory control signal is transmitted or not. Further, a circuit composed of the delay circuit 61, exclusive OR gate 62, block synchronization circuit 12, and AND gate 66 is used as an error detection circuit for the mB1C code or DmB1C code transmission system. Therefore, only the gate circuit 64, the low-pass filter 46, and the inverting amplifier 65 are newly required on the receiving side for the transmission of the supervisory control signal, so the supervisory control is small, low-power, and economical. Signal transmission is possible.

Here, the operation of this embodiment will be explained.

Since the amplitude of the auxiliary code that is complex-modulated by the supervisory control signal is smaller, it is more susceptible to deterioration such as noise during transmission than the main signal information. Therefore, by measuring the bit error rate of the auxiliary code, the bit error rate can be measured in an extremely shorter time than measuring the bit error rate of the main signal information. Therefore, the deterioration state of the device can be detected early before the bit error rate of the main signal information deteriorates.

This will be explained further.

In FIG. 4, a terminal 53 of the transmitting device is an input terminal for a variable modulation degree signal, and this input causes a resistance R
control the value of . The value of the resistor R is changed by the voltage applied to the terminal 53, and the inverting differential amplifier 1
The magnitude of the output amplitude modulation degree Δ of 6 is converted. For example, as the output amplitude modulation degree Δ is changed from 5% to 10%, the auxiliary code amplitude decreases and the bit error rate of the auxiliary code deteriorates. In a normal line, code errors in main signal information transmission are set to be so small that they are almost undetectable, so by increasing the modulation degree Δ described above, it is possible to cause deterioration in the auxiliary code. By measuring the value of the modulation degree Δ that causes a specified code error at the auxiliary code error detection terminal 70, that is, by measuring the value of the control voltage at the modulation degree variable terminal, the operating margin of the line can be measured. This operation margin measurement can be performed during main signal information transmission, which is extremely advantageous in terms of maintenance and operation.

7 and 8 are partial block diagrams of a second embodiment of the present invention. FIG. 7 is a block diagram of the transmission code conversion circuit 3 of the transmitter, and FIG. 8 is a block diagram of the reception code conversion circuit 37 of the receiver. 7th
In the figure, 80 is a speed conversion circuit on the transmitting side, 81 is a frame pulse insertion circuit, 82 is a parity check frame insertion circuit, and 83 is an insertion circuit for an auxiliary code (C bit) in the mB1C code. Reference numeral 11 indicates the output of the transmission code conversion circuit, and reference numeral 92 indicates the block synchronization pulse output. In Fig. 7, 41 is the reception conversion circuit input, 85
86 is a frame synchronization circuit, 86 is an auxiliary code (C bit) error detection circuit, 87 is a parity check circuit, 88 is a speed conversion circuit on the receiving side, 38 is a main signal output on the receiving side, 90 is a C bit (auxiliary code) ) error output, 91 is a parity check error output.

In a device with such a configuration, the code error rate of the main signal is determined by the parity check for transmission and reception, and the code error rate of the composite modulated auxiliary code (C bit) is determined by the mB1C code rule check as described above.
Detect each. Therefore, the code error rate of the main signal can be used to initiate switching to the protection line, and the error rate of the auxiliary code can be used to monitor preventive maintenance.
The reliability of the communication system can be greatly improved.

In the embodiments shown in FIGS. 7 and 8, a parity check code is used to monitor the code error rate of the main signal, but the same result can be obtained using other code error rate detection methods. Can be implemented.

〔Effect of the invention〕

As described above, according to the present invention, the bit error rate can be measured in a short time by performing amplitude modulation with a variable modulation degree on the auxiliary code and detecting code errors in the auxiliary code on the receiving side. This has the effect of detecting the deterioration state of the device at an early stage and contributing to preventive maintenance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a transmission system using auxiliary codes used in the present invention. FIG. 2 is a waveform time chart explaining conventional composite modulation. FIG. 3 is a waveform time chart for explaining the operation of FIG. 1. FIG. 4 is a block diagram of the first embodiment of the present invention. 5 and 6 are waveform time charts for explaining the operation of the first embodiment of the present invention. 7 and 8 are partial block diagrams of a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Main signal input terminal, 2... Monitoring control signal input terminal, 3... Transmission code conversion circuit, 4... Light source drive circuit, 5, 6... Adding circuit, 7... Automatic output control circuit,
8... Light source, 9... Optical detector for monitoring light source output, 10
...Light source output, 12...Block synchronization circuit, 13...AND gate, 16...Inverting differential amplifier, 18...Gate circuit, 31...Optical signal input, 32...Optical detector, 3
3... Amplifier, 34... Waveform equalizer, 35... Automatic gain control circuit, 36... Discriminator, 37... Reception code conversion circuit, 38... Terminal from which the main signal is output, 40... Timing generation circuit, 42... Difference circuit, 44...Double-wave rectifier circuit, 46...Low-pass filter, 47...Terminal from which a supervisory control signal is output, 52...AND gate, 53...Modulation degree convertible terminal, 54...Delay element, 55...Difference circuit, 59...Tank Circuit, 60...limiter amplifier,
61...Delay circuit, 62...Exclusive OR gate, 6
3...Block synchronization pulse output, 64...Gate circuit, 65...Inverting amplifier, 66...And gate, 7
0... Code error output, 80... Transmission speed conversion circuit, 8
1... Frame pulse insertion circuit, 82... Parity check code insertion circuit, 83... Auxiliary code insertion circuit,
85... Frame synchronization circuit, 86... Auxiliary code error detection circuit, 87... Parity check circuit, 88... Reception speed conversion circuit, 90... Auxiliary code error output terminal,
91... Parity check error output terminal, 92... Synchronization signal output terminal.

Claims (1)

[Claims] 1. A transmitting device and a receiving device that receives an output signal of the transmitting device, the transmitting device having a terminal into which a main signal is input;
The receiver is equipped with a terminal into which a supervisory control signal is input, and a transmitting means for inserting the supervisory control signal into the main signal as the output signal, and the receiving device receives the main signal and the supervisory control signal from the output signal. a receiving means for separating; a terminal for outputting the main signal separated by the receiving means;
and a terminal for outputting the supervisory control signal separated by the receiving means, wherein the transmitting means inserts an auxiliary code into the digital code sequence of the main signal to generate a slightly higher-speed digital code sequence. and means for amplitude modulating the auxiliary code using the supervisory control signal, the amplitude modulating means comprising means for variably controlling the degree of modulation to increase the bit error rate of the auxiliary code, The receiving means includes means for extracting the auxiliary code from a high-speed digital code sequence into which the auxiliary code has been inserted, and means for amplitude-detecting the auxiliary code extracted by the means to obtain the separated supervisory control signal. A digital communication device comprising: , code error monitoring means for detecting code errors in the separated supervisory control signal. 2. The transmitting means includes means for inserting an error detection code into the main signal to be transmitted, and the receiving means includes means for monitoring errors in the received main signal using the error detection code. The digital communication device according to scope item (1).