SU1677676A1 - Device for locating faults in optic cable - Google Patents

Abstract

The invention relates to a measurement technique and can be used to determine the distance to a damaged optical cable. The aim of the invention is to increase the reliability of measuring the distance to the damage site and the location of the non-uniformity of the optical cable. A device containing a probe pulse generator 1, an optical transmitter 2, an optical splitter 3, an optical receiver 4, a delay line 5, and a measurement unit 6 are inserted a comparator, a switch 8, an inverter 9, a reference voltage unit 10, and It does not distinguish between two types of optical cable defects (damage and non-uniformity), regardless of the distance of the defect. 2 Il.

Description

The invention relates to measuring equipment and can be used to determine the distance to the place of damage of the optical cable.

The purpose of the invention is to increase the reliability of the results of measuring the distance to the place of damage or heterogeneity of the optical cable.

In FIG. 1 shows a structural diagram of a device; in FIG. 2 is a timing diagram explaining the operation of the device,

The device comprises a probe pulse generator (SCI) 1, an optical transmitter 2, an optical splitter 3, an optical receiver 4, a delay line 5, a measurement unit 6, a comparator 7, a switch 8, an inverter S, a voltage reference unit 10.

Block 6. measurement contains serially connected trigger 11 and meter 12.

In addition, the structural diagram shows a controlled optical cable 13, which is not included in the device.

GZI 1, optical transmitter 2, optical splitter 3 and optical receiver 4 are connected in series, the second output of the optical splitter 3 is connected to the output of the device and to the controlled optical cable 13, the second output of the GZI 1 through the delay line 5 is connected to the first input of the measurement unit 6 and the input unit 10 of the reference voltage, which is connected in series with the inverter 9 and the switch 8, the first and second inputs of the comparator 7 are connected respectively to the outputs of the switch 8 and the optical receiver 4, the output of the comparator 7 soy Inonii the second input of the measurement unit 6.

The reference voltage block 10 generates the reference voltage according to the law of attenuation of the pulses of the optical cable. The block 10 of the reference voltage can be performed, for example, in the form of a pulse generator, the launch of which is carried out using the signals GZI 1, arriving at block 1Ό through the delay line 5. The most accurate repetition of the law of attenuation of pulses of an optical cable is the charge of the capacitance. By changing the time constant of the charge of the capacitance in the pulse generator, it is possible to obtain a different slope of the voltage across the capacitance, thereby obtaining an exact reproduction of the law of attenuation of pulses for various optical cables. For these purposes, a switch is provided in the voltage reference block 10.

The switch 8 is designed to ensure the operation of the comparator 7 in two modes;

1) with a change in the reference voltage according to the law of attenuation of pulses in the cable;

2) with a constant reference voltage.

The first mode of operation of the comparator 7 allows you to determine the distance to the place of damage to the optical cable, the second mode allows you to determine the distance to the place of heterogeneity in the optical cable 14 or, in the absence of heterogeneities, to the place of damage to the cable.

The meter 12 can be performed using a dial gauge, the scale of which is calibrated in units of length, or on digital elements.

A device for determining the distance to the place of damage to the optical cable operates as follows.

GZI 1 generates signals arriving at the optical transmitter 2. From the output of the optical transmitter 2, the signal through the optical splitter 3 is fed to the input of the controlled optical cable 13.

When the signal passes through the optical splitter 3 from the optical transmitter 2 in the direction of the monitored optical cable 13, part of its energy will branch out towards the optical receiver 4 and be received by it. The signal received by the optical receiver 4 through the comparator 7 (for both operating modes of the comparator 7) is fed to the first input of the trigger 11 and sets it to state 0. The delay line 5 is selected so that the signal from the GZI 1 is fed to the second input of the trigger 11 in time after installation it to state 0 and sets it to state 1 to start the measurement. In addition, the same signal produces a start block 10 of the reference voltage. From the output of the reference voltage unit 10, the reference voltage signal inverted by the inverter 9 through the switch 8 will go to the second input of the comparator 7, setting the threshold.

Thus, the signals reflected from the inhomogeneities of the cable through the comparator 7, operating in the mode of alternating reference voltage, will not pass. Since the signal from the cable break will be several times larger than from inhomogeneities, it will pass through the comparator 7. From the output of the comparator 7, the signal will go to the first input of the trigger 11 of the measurement unit 6 and set the trigger 11 to the state ”0.

From the time interval between the probe pulse and the reflected signal, the distance to the place of damage is determined using meter 12.

In the case of transferring the comparator 7, using switch 8, to the constant reference voltage mode, the signal reflected from the first heterogeneity will be received. in condition O.

On Fig, 2 shows a timing diagram of the operation of the device, where:

a) probing pulses and reflected pulses from the place of heterogeneity and cable break 13; b) the signal at the output of the trigger 11 during operation of the comparator 7 with a variable reference voltage;

C) - inverted reference voltage at the first input of the comparator 7;

g) - the signal at the output of the trigger 11 during 20 operation of the comparator 7 with a constant reference voltage.

Due to the proposed structure of the device, the pulses reflected from various places of damage and heterogeneity of the cable 25 are compared with various values of the time-varying reference voltage (threshold voltage), i.e. regardless of the distance of the defect, the signal reflected from the inhomogeneity will not be mistaken for the signal reflected from damage to the cable.

At a constant reference voltage, both the signal reflected from damage at the end of the cable and the signal reflected from heterogeneity at the beginning of the cable could exceed the level of the reference voltage and both would be taken as a sign of damage to the cable.

Thus, in this device, the uncertainty of registration of defects, i.e. the reliability of determining the distance both to the place of damage and to the place of cable heterogeneity is increased.

Claims (1)

Claim A device for determining the distance to the place of damage of the optical cable, comprising a delay line, a measurement unit, a probe pulse generator, an optical transmitter, an optical splitter and an optical receiver connected in series, the second output of the optical splitter connected to the output of the device, the second output of the probe pulse generator connected through the delay line with the first input of the measurement unit, characterized in that. that, in order to increase the reliability of the measurement results, series-connected reference voltage block, inverter, switch and comparator are introduced into it. the second passage of which is connected to the output of the optical receiver, and the output is connected to the second input of the measurement unit, the output of the delay line is connected to the input of the reference voltage unit, the second input of the switch is connected to a common bus.