RU2745361C1 - Method of searching for an optical cable laying route - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: invention relates to measurement equipment and can be used to search for routing of optical cable. Above the prospective location of the optical cable at a fixed distance from each other, two anti-phase directional acoustic-vibration effects are placed. They are moved longitudinally across the cable route, without changing the distance between them so that the axis connecting them is approximately perpendicular to the cable laying route. Phase-sensitive pulsed optical reflectometer is used to measure the backscattering characteristic of the optical fiber. Determining the cable laying route along the location of the axis center between two sources of directional acoustic-vibration action operating in antiphase and corresponding to a local minimum located between two local maxima.EFFECT: reduced error in determination of optical cable laying route, eliminated necessity to perform measurements without acoustic-vibration action.1 cl, 2 dwg

Description

The invention relates to measuring equipment and can be used to search for a route for laying an optical cable.

Known methods [1-3] for determining the distance to the place of the acoustic and, in particular, the vibration impact on the optical cable using a phase-sensitive pulse optical reflectometer, in which the coherence length of the optical radiation source is greater than the pulse duration, consisting in the fact that from one end of the cable is measured the backscatter characteristic of the optical fiber, the reflection of the impact on the optical cable is identified on the backscatter characteristic of the optical fiber, and the distance to the impact site is determined from the backscatter characteristic of the optical fiber. These methods are not intended for finding the route of laying an optical cable.

There is a known method [4] for determining the location of pipelines, which consists in the fact that a pulse wave generator is connected to the pipeline, a device is installed above the proposed location of the pipeline, containing a calculator of the difference in acoustic signals and two sensitive elements made in the form of microphones and located along the horizontal plane at a distance from each other, to determine the axis of the pipeline buried in the ground, the device is moved in the direction of increasing signals in both microphones, determining the location of the pipeline by the difference in signal levels in both microphones, which will decrease and reach a minimum when the axis of the pipeline is in the middle between the microphones. This method is not intended to search for a route for laying an optical cable.

There is a method [5] for detecting the route of a dielectric optical cable from the ground surface, based on the excitation of a test signal propagating along the sought cable, and determining the cable route using a fixed signal, a modulated optical signal propagating along one of the optical fibers of an optical cable is used as a test signal , create a time-varying local bending of this optical fiber by mechanical action by a source of low-frequency mechanical vibrations, carried out by its longitudinal-transverse movement relative to the intended cable route, and by the maximum value of the received low-frequency signal, the cable route is judged. The main problems of the implementation of this method are associated with the fact that to obtain a satisfactory signal at reception, a sufficiently high power of the source of low-frequency mechanical vibrations is required, which in turn determines its mass and size characteristics, limits the resolution of the method and the length of the route section on which the method can be implemented. An increase in the weight and size characteristics of the source of low-frequency mechanical vibrations leads to an increase in the cost of moving it along the route. Certain inconveniences are created by the need to connect to the cable from both sides of the site.

The closest to the claimed one is a method of searching for a route for laying an optical fiber of a cable [6], which consists in the fact that a source of directional acoustic-vibration impact is moved above the cable longitudinally-transversely relative to the intended cable route, while a separate communication channel controls the movements of a source of directional acoustic vibration exposure and the level of acousto-vibration exposure, using a phase-sensitive pulsed optical reflectometer, in which the coherence length of the optical radiation source is longer than the probe pulse duration, measure the backscattering characteristic of the optical fiber in the absence of vibration exposure, then produce an acousto-vibration effect on the cable from the earth's surface , moving the source of directional vibration over the intended path, using a phase-sensitive pulse optical reflectometer, in which the coherence length of the optical source is radiation longer than the duration of the probe pulse, measure the characteristic of the backscattering of the optical fiber under vibration and determine the cable route by the location of the source of directional vibration action, in which the difference between the characteristics of backscattering, measured using a phase-sensitive pulse optical reflectometer before the start and during vibration action in place vibration impact is maximum. The disadvantages of this method include the relatively smooth nature of the change in the induced phase shift in the optical fiber in the region of its maximum when the source of the directional acoustic-vibration effect moves directly above the cable, which makes it difficult to localize the point corresponding to the maximum level of the signal difference and leads to additional errors in determining the route of laying the optical cable ...

The essence of the proposed invention is to expand the scope.

This essence is achieved by the fact that according to the method of searching for the route of laying the optical cable, a directed acoustic-vibration effect is created on the cable, the source of the directional acoustic-vibration effect is moved longitudinally-transversely relative to the intended route of the cable laying and its movements and the level of acoustic-vibration are controlled through a separate communication channel. influence, and using a phase-sensitive pulsed optical reflectometer measure the characteristic of the backscattering of the optical fiber, while above the proposed location of the optical cable at a fixed distance from each other, place two sources of directional acoustic-vibration impact operating in antiphase, move them longitudinally-transversely relative to the proposed route of laying cables without changing the distance between them so that the axis connecting them would be approximately perpendicular to the cable routing, and determine the cable routing by location the center of the axis between two sources of directional acoustic-vibration action operating in antiphase, in which the dependence of the measured signal level on the displacement of the specified center of the axis between two sources of directed acoustic-vibration action operating in antiphase relative to the cable axis in the impact zone corresponds to a local minimum located between the two local maxima.

Figure 1 shows a block diagram of a device for implementing the proposed method.

The device includes an optical cable 2 with optical fiber 3 laid below the earth's surface, a phase-sensitive pulse optical reflectometer 4, a processing and control unit 5, a communication channel 6, a matching and display unit 7 and two sources of directional acoustic-vibration action 8 operating in antiphase.

Optical fiber 3 of the optical cable 2 laid below the earth's surface 1 is connected to the input of the phase-sensitive pulse optical reflectometer 4, the output of which is connected to the input of the processing and control unit 5, and the output of the processing and control unit 5 through the communication channel 6 is connected to the input of the matching and display unit 7 , the output of which is connected to the inputs of two sources of directional acoustic vibration action 8 operating in antiphase.

The device works as follows. Under the action of the signal from the processing and control unit 5, transmitted through the communication channel 6, two sources of directional acoustic-vibration action operating in antiphase are switched on 8. The matching unit of the matching and display unit 7 ensures the magnitude and equality of the levels of acoustic-vibration action from two operating in antiphase sources of directional acousto-vibration impact 8, controls their antiphase operation and displays the necessary information about the signals measured by the phase-sensitive pulse optical reflectometer 4. When two sources of directional acoustic-vibration action 8 operate in antiphase, the phase-sensitive pulse optical reflectometer 4 measures the characteristic of the backscattering of the optical fiber and transmits the results of the measurements of the characteristics to the processing and control unit 5. According to the results of processing the characteristics measured by the phase-sensitive pulse optical reflectometer 4, the processing unit and control 5 through the communication channel 6 and the matching and display unit 7 regulates the level of acousto-vibration impact and the movement of two sources of directional acoustic-vibration action 8 operating in antiphase. According to the results of the movements of two sources of directional acoustic-vibration action 8 operating in antiphase into the processing unit and control 5, the dependence of the levels of the signals measured by the phase-sensitive pulse optical reflectometer 4 on the displacement of the center of the axis between the two sources of directional acoustic vibration operating in antiphase is plotted 8 relative to the axis of the optical cable 2, along which the route of laying the optical cable 2 is determined as the location of the specified center of the axis between two sources of directional acoustic-vibration action 8 operating in antiphase, for which the dependence of the measured signal level on the displacement of the specified center of the axis between two operating in antiphase antiphase sources of directional acousto-vibration impact 8 relative to the axis of the cable 2 in the impact zone corresponds to a local minimum located between two local maxima of the investigated dependence as shown in Fig. 2.

In contrast to the known method, which is the prototype, in the proposed method, due to the use of two sources of directed acoustic-vibration action operating in antiphase, a more significant dependence of the measured signal levels on the displacement of the acoustic-vibration effect relative to the cable is provided, which can significantly reduce the errors in determining the route of the laying optical cable in comparison with the prototype. In addition, it eliminates the need for measurements in the absence of acousto-vibration exposure. All this allows you to expand the scope of the proposed method in comparison with the prototype.

LITERATURE

1. US 5194847

2.US 2013/0113629

3.US 2014/0183360

4. RU 120784

5. SU 1818600

6. RU 2656295.

Claims (1)

A method of searching for a route for laying an optical cable, which consists in creating a directed acoustic-vibration effect on a cable, a source of a directed acoustic-vibration effect is moved longitudinally-transversely relative to the proposed route of laying a cable and, through a separate communication channel, control its movements and the level of acoustic-vibration effect, and using a phase-sensitive pulsed optical reflectometer, the backscattering characteristic of the optical fiber is measured, characterized in that two sources of directional acoustic-vibration action operating in antiphase are placed above the proposed location of the optical cable at a fixed distance from each other, and they are moved longitudinally-transversely relative to the intended route of laying cable, without changing the distance between them, so that the axis connecting them would be approximately perpendicular to the cable route, and determine the cable route by location center of the axis between two sources of directional acoustic-vibration action operating in antiphase, in which the dependence of the measured signal level on the displacement of the indicated center of the axis between two sources of directed acoustic-vibration action operating in antiphase relative to the cable axis in the impact zone corresponds to a local minimum located between two local highs.

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