CN100422629C - Pipeline leakage monitor based on sagnac optical fiber interferometer - Google Patents

Abstract

The present invention relates to a pipeline leakage monitoring device based on Sagnac fiber-optic interferometer. Said device mainly has signal transmitting and processing system, distributed fiber-optic sensing system and signal analysis system. In the distributed fiber-optic sensing system first sensing optic fibre, first Faraday rotating mirror and second sensing optic fibre and second Faraday rotating mirror are formed into two interferometers. Besides, said invention also provides the concrete working principle of said pipeline leakage monitoring device based on Sagnac fibre-optic interferometer and its operation method.

Description

Pipeline leakage monitor based on the Sagnac fibre optic interferometer

Technical field

The present invention is a kind of pipeline leakage monitor based on the Sagnac fibre optic interferometer, belongs to the line leakage field.

Background technique

Pipeline is one of five existing big means of transportation, have cost at aspects such as transporting liquid, gas, slurries low, save the energy, safe and supply with stable advantage, in industries such as oil, chemical industry, rock gas and town water supply, irreplaceable effect is arranged.Along with the continuous development of pipeline industry, for the safe operation of service conduit, pipeline operational monitoring technology is also in continuous development.

Existing long-distance pipe leak detection technology mainly contains negative pressure wave method, modelling etc., has shortcomings such as sensitivity is low, low-response, Location accuracy difference, is difficult to satisfy the requirement of accurate detection pipe leakage in actual applications.In recent years, development along with optical fiber sensing technology, the long-distance distributed optical fiber sensory technique also begins to be applied to pipeline leakage testing, because highly sensitive, the dynamic range of optical fiber transducer is big, response is fast, transmission distance is long, can satisfy long distance, little leakage pipe detection requirement.Chinese invention patent application 200410020046.6 adopts the interference type distributed optical fiber vibrative sensor to carry out pipeline leakage testing, this sensor is to be made of one three core single mode fiber cable and the corresponding optical element laid side by side along pipeline near the pipeline, when pipeline takes place to leak, the leakage noise that produces makes the photophase that transmits in the optical fiber modulated, the output that causes interference light changes, and then judges that leak free generation is arranged.Because this sensory technique is only used a single mode fiber cable, when pipe diameter is bigger, particularly leakage hole deviates from optical cable direction (the pipeline bus that is the pipeline bus at leakage hole place and optical cable place along the circumferential direction differs 180 degree), the time, be difficult to detect leak and take place, therefore leak the alarm rate height.

Summary of the invention

The objective of the invention is to overcome the above defective, a kind of bilinear type pipeline leakage monitor based on the distributing optical fiber sensing technology has been proposed, the advantage of this device is to form two Sagnac interferometers by a covering device, can be simultaneously the sensor fibre cloth of two interferometers be put on the different buses of pipeline, realization is along the circumferential leakage monitoring of pipeline, and this Device Testing is highly sensitive, rate of failing to report is low, optical power loss is little, can realize little Leak testtion of pipe long-distance and location.

In order to achieve the above object, the following technological scheme of the present invention's employing.This device mainly includes signal emission and processing system 1, distributed optical fiber sensing system 2, Signal Analysis System 3, and the signal emission includes broadband continuous light source A1, the first Coupler A3, the 5th Coupler B2, the second Coupler C2, the first photoelectric converter C9, the second photoelectric converter B9, the first A/D converter C10, second A/D converter B10 composition again with processing system 1; Distributed optical fiber sensing system 2 includes the 3rd Coupler C4, the 4th Coupler C6, the 6th Coupler B4, the 7th Coupler B6, the 8th Coupler A4, the 9th Coupler A7, phase-modulator A5, delay winding A6, the first faraday rotation mirror C8, the second faraday rotation mirror B8; Signal Analysis System 3 includes computer A 8; Wherein, the signal emission is connected with the input end of the first Coupler A3 by the first Single Mode Fiber A2 with the broadband continuous light source A1 of processing system 1, and two output terminals of the first Coupler A3 are connected with the output terminal of the second Coupler C2, the output terminal of the 5th Coupler B2 by the second Single Mode Fiber C1, the 3rd Single Mode Fiber B1 respectively; The input end of the second Coupler C2 is connected with the input end of the 3rd Coupler C4 by the first guiding fiber C3, and another output terminal of the second Coupler C2 is connected with computer A 8 by the first photoelectric converter C9, the first A/D converter C10 successively; The input end of the 5th Coupler B2 is connected with the input end of the 6th Coupler B4 by the second guiding fiber B3, and another output terminal is connected with computer A 8 by the second photoelectric converter B9, the second A/D converter B10 successively; The output terminal of the 3rd Coupler C4 is connected with the output port G of the 4th Coupler C6 by the 4th Single Mode Fiber C5, and another output terminal is connected with the output port E of the 8th Coupler A4; The input end of the 4th Coupler C6 is connected with the first sensor fibre C7, and the end of the first sensor fibre C7 connects the first faraday rotation mirror C8; The output terminal of the 6th Coupler B4 is connected with the output port N of the 7th Coupler B6 by the 5th Single Mode Fiber B5, another output terminal is connected with the output port F of the 8th Coupler A4, the input end of the 7th Coupler B6 is connected with the second sensor fibre B7, and the end of the second sensor fibre B7 connects the second faraday rotation mirror B8; The input end of the 8th Coupler A4 is connected with the input end of the 9th Coupler A7 by phase-modulator A5, delay winding A6 successively, and two output terminals of the 9th Coupler A7 are connected with the output port H of the 4th Coupler C6, the output port M of the 7th Coupler B6 respectively.

Form two Sagnac interferometers by the first sensor fibre C7, the first faraday rotation mirror C8 and the second sensor fibre B7, the second faraday rotation mirror B8 in the distributed optical fiber sensing system 2, and shared same delay winding of these two interferometers and phase-modulator.

Working principle of the present invention: the light that is sent by broadband continuous light source A1 is in the propagation process of this device, specifically referring to Fig. 1, the light that is sent by broadband continuous light source A1 enters the first Coupler A3 through the first Single Mode Fiber A2, the light of first Coupler A3 output is divided into two-way (forming two interferometers) by power at 1: 1, wherein first via light enters the second Coupler C2 through the second Single Mode Fiber C1, enter the 3rd Coupler C4 through the first guiding fiber C3 again, the light of the 3rd Coupler C4 output is divided into two bundles by power at 1: 1, wherein a branch of light enters the first sensor fibre C7 through the 4th Single Mode Fiber C5 and the 4th Coupler C6 transmission, the light that transmits among the first sensor fibre C7 arrives the first faraday rotation mirror C8, after first faraday rotation mirror C8 reflection, again along the first sensor fibre C7 backpropagation to the, four Coupler C6, the output of the 4th Coupler C6 is divided into two bundles by power at 1: 1, the light that wherein only is transferred to the 9th Coupler A7 meets interference condition (other light is not considered), delayed then loop A 6, phase-modulator A5 propagates into the 8th Coupler A4, the light of same the 8th Coupler A4 output is divided into two bundles by power at 1: 1, a branch of the 4th Coupler C4 that enters, another bundle enters the 6th Coupler B4 (this Shu Guang does not meet interference condition, does not consider).The light that enters the 3rd Coupler C4 from the first guiding fiber C3 is divided into two bundles in addition, another Shu Jingdi eight Coupler A4 wherein, phase-modulator A5, delay winding A6 enters the 9th Coupler A7, the light of the 9th Coupler A7 output is divided into two bundles by power at 1: 1, a branch of light enters the 7th Coupler B6 and (does not meet interference condition, do not consider), another Shu Guangjing the 4th Coupler C6, the first sensor fibre C7 enters the first faraday rotation mirror C8, after first faraday rotation mirror C8 reflection, enter the 4th Coupler C6 along the first sensor fibre C7 again, the light of the 4th Coupler C6 output is divided into two bundles by power at 1: 1, the light that wherein enters the 9th Coupler A7 does not meet interference condition, therefore do not consider, and another Shu Guang enters the 4th Single Mode Fiber C5 and converge interference with the above-mentioned light of getting back to the 3rd Coupler C4 after the first faraday rotation mirror C8 reflection at the 3rd Coupler C4, interference light enters the second Coupler C2 through the first guiding fiber C3, the light of second Coupler C2 output is converted to electrical signal with optical signal behind the first photoelectric converter C9, this electrical signal is through the last entering signal analytical system of first A/D converter C10 A8.In computer A 8, carry out demodulation at last, and do the FFT conversion,, can realize leakage alarm and location by the analytic signal frequency spectrum to gathering signal.

The second road light enters the 5th Coupler B2 through the 3rd Single Mode Fiber B1, enter the 6th Coupler B4 through the second guiding fiber B3, the light of the 6th Coupler B4 output is divided into two bundles by power at 1: 1, wherein a branch of light enters the second sensor fibre B7 through the 5th Single Mode Fiber B5 and the 7th Coupler B6 transmission, the light that transmits among the second sensor fibre B7 arrives the second faraday rotation mirror B8, after second faraday rotation mirror B8 reflection again along the second sensor fibre B7 backpropagation to the, seven Coupler B6, the light of the 7th Coupler B6 output is divided into two bundles by power at 1: 1, the light that wherein only is transferred to the 9th Coupler A7 meets interference condition (other light is not considered), delayed then loop A 6, phase-modulator A5 propagates into the 8th Coupler A4, the light of same the 8th Coupler A4 output is divided into two bundles by power at 1: 1, a branch of the 6th Coupler B4 that enters, another bundle enters the 4th Coupler C4 (this Shu Guang does not meet interference condition, does not consider).The light that enters the 6th Coupler B4 from the second guiding fiber B3 is divided into two bundles in addition, another Shu Jingdi eight Coupler A4 wherein, phase-modulator A5, delay winding A6 enters the 9th Coupler A7, the light of the 9th Coupler A7 output is divided into two bundles by power at 1: 1, a branch of light enters the 4th Coupler C6 and (does not meet interference condition, do not consider), another Shu Guangjing the 7th Coupler B6, the second sensor fibre B7 enters the second faraday rotation mirror B8, after second faraday rotation mirror B8 reflection, enter the 7th Coupler B6 along the second sensor fibre B7 again, the light of the 7th Coupler B6 output is divided into two bundles by power at 1: 1, the light that wherein enters the 9th Coupler A7 does not meet interference condition, therefore do not consider, and another Shu Guang enters the 5th Single Mode Fiber B5 and converge interference with the above-mentioned light of getting back to the 6th Coupler B4 after the second faraday rotation mirror B8 reflection at the 6th Coupler B4, interference light enters the 5th Coupler B2 through the second guiding fiber B3, the light of the 5th Coupler B2 output is converted to electrical signal with optical signal behind the second photoelectric converter B9, this electrical signal is through the last entering signal analytical system of second A/D converter B10 A8.In computer A 8, carry out demodulation equally, and do the FFT conversion,, can realize leakage alarm and location by the analytic signal frequency spectrum to gathering signal.

The line leakage principle of this system is: when there is the generation of leakage in the pipeline somewhere, leak fluid produces friction with the leakage hole wall, on tube wall, inspire stress wave (promptly leaking acoustic emission signal), this stress wave activity is modulated to the sensor fibre of interferometer and to the photophase that transmits in the sensor fibre, owing to there is delay winding, make the asynchronism(-nization) of the two beam interferometer light process leakage point D in the interferometer, it is also different to the phase modulation of two-beam to leak acoustic emission signal, produce phase difference between two-beam, therefore two-beam interferes (does not have and leaks when taking place, two-beam phase place unanimity does not produce interference).By the variation of real-time detection interference light signal, can realize line leakage.

Leaking acoustic emission signal can be expressed as the phase difference that two beam interferometer light phase modulation in the interferometer produce

${\mathrm{\φ}}_s\left(t\right)=4\mathrm{\Δ\φ}\cos {\mathrm{\ω}}_{s}t\·\sin {\mathrm{\ω}}_s\left(\frac{{\mathrm{\τ}}_d}{2}\right)\·\cos \left({\mathrm{\ω}}_s{\mathrm{\τ}}_s\right)---\left(1\right)$

This phase difference has comprised temporal information and has leaked the frequency information of acoustic emission signal, wherein ω _sFor leaking the angular frequency of acoustic emission signal, τ _dBe light process delay winding time, τ _sFor light propagates into the faraday rotation mirror needed time from the leak position

From formula (1), obtain time τ _sJust can obtain the distance of leakage point in optical fiber according to the speed that light is propagated apart from faraday rotation mirror.In the formula (1), $4\mathrm{\Δ\φ}\sin {\mathrm{\ω}}_s\left(\frac{{\mathrm{\τ}}_d}{2}\right)\cos \left({\mathrm{\ω}}_s{\mathrm{\τ}}_s\right)$ Proportional with the signal frequency-domain amplitude, in the wide frequency range that leaks acoustic emission signal, always there is a frequency to make $4\mathrm{\Δ\φ}\sin {\mathrm{\ω}}_s\left(\frac{{\mathrm{\τ}}_d}{2}\right)\cos \left({\mathrm{\ω}}_s{\mathrm{\τ}}_s\right)=0,$ And

Irrelevant with the leak position, therefore determine delay winding length, guarantee in the wide frequency range of leakage signal

Be not equal to zero, cos (ω is so just arranged _sτ _s)=0 (promptly ${\mathrm{\ω}}_s{\mathrm{\τ}}_s=\frac{\mathrm{\π}(1+n)}{2},$ N is an even number), therefore can occur amplitude in frequency domain is zero point, frequency that this point is corresponding is called zero frequency.Basis after finding zero frequency on the spectrogram ${\mathrm{\ω}}_s{\mathrm{\τ}}_s=\frac{\mathrm{\π}(1+n)}{2}$ (n is an even number) calculated bright dipping and propagated into faraday rotation mirror needed time τ from leakage point _sTry to achieve τ _sAfter, according to formula s=v τ _s(v is the velocity of propagation of light in optical fiber) calculate the leak position to reflector apart from s.

The advantage of this system is: native system has adopted bilinear type distributed optical fiber acoustic sensing technology that pipeline is monitored in real time, whole transducing part by two independently optical fiber constitute (forming two interferometers), cloth is put on the pipeline at a distance of 180 two bus positions spending respectively, when having solved the use simple optical fiber when caliber when big or leakage hole deviates from the optical fiber direction, be difficult to detect the problem of leakage signal, therefore do not exist and fail to report alert phenomenon.Simultaneously because therefore the low-loss of optical fiber and to the hypersensitivity of acoustic signal can realize the little Leak testtion of long-distance pipe.Change the beam split quantity of Coupler in this system in addition, the system that can become many pipelines to monitor simultaneously this structural development.

Description of drawings

Fig. 1 system construction drawing of the present invention

Fig. 2 leakage signal time domain waveform

Fig. 3 zero frequency figure

Among Fig. 1: A1, the broadband continuous light source, A2, first Single Mode Fiber, A3, first Coupler, A4, the 8th Coupler, A5, phase-modulator, A6, delay winding, A7, the 9th Coupler, A8, computer, B1, the 3rd Single Mode Fiber, B2, the 5th Coupler, B3, second guiding fiber, B4, the 6th Coupler, B5, the 5th Single Mode Fiber, B6, the 7th Coupler, B7, second sensor fibre, B8, second faraday rotation mirror, B9, second photoelectric converter, B10, second A/D converter, C1, second Single Mode Fiber, C2, second Coupler, C3, first guiding fiber, C4, the 3rd Coupler, C5, the 4th Single Mode Fiber, C6, the 4th Coupler, C7, first sensor fibre, C8, first faraday rotation mirror, C9, first photoelectric converter, C10, first A/D converter, P, pipeline, 1, signal emission and processing system, 2, distributed optical fiber sensing system, 3, Signal Analysis System.

Embodiment

The concrete structure of present embodiment, referring to Fig. 1, present embodiment mainly includes signal emission and processing system 1, distributed optical fiber sensing system 2, Signal Analysis System 3, and the signal emission includes broadband continuous light source A1, the first Coupler A3, the 5th Coupler B2, the second Coupler C2, the first photoelectric converter C9, the second photoelectric converter B9, the first A/D converter C10, second A/D converter B10 composition again with processing system 1; Distributed optical fiber sensing system 2 includes the 3rd Coupler C4, the 4th Coupler C6, the 6th Coupler B4, the 7th Coupler B6, the 8th Coupler A4, the 9th Coupler A7, phase-modulator A5, delay winding A6, the first faraday rotation mirror C8, the second faraday rotation mirror B8; Signal Analysis System 3 includes computer A 8; Wherein, the signal emission is connected with the input end of the first Coupler A3 by the first Single Mode Fiber A2 with the broadband continuous light source A1 of processing system 1, and two output terminals of the first Coupler A3 are connected with the output terminal of the second Coupler C2, the output terminal of the 5th Coupler B2 by the second Single Mode Fiber C1, the 3rd Single Mode Fiber B1 respectively; The input end of the second Coupler C2 is connected with the input end of the 3rd Coupler C4 by the first guiding fiber C3, and another output terminal is connected with computer A 8 by the first photoelectric converter C9, the first A/D converter C10 successively; The input end of the 5th Coupler B2 is connected with the input end of the 6th Coupler B4 by the second guiding fiber B3, and another output terminal is connected with computer A 8 by the second photoelectric converter B9, the second A/D converter B10 successively; The output terminal of the 3rd Coupler C4 is connected with the output port G of the 4th Coupler C6 by the 4th Single Mode Fiber C5, and another output terminal is connected with the output port E of the 8th Coupler A4; The input end of the 4th Coupler C6 is connected with the first sensor fibre C7, and the end of the first sensor fibre C7 connects the first faraday rotation mirror C8; The output terminal of the 6th Coupler B4 is connected with the output port N of the 7th Coupler B6 by the 5th Single Mode Fiber B5, another output terminal is connected with the output port F of the 8th Coupler A4, the input end of the 7th Coupler B6 is connected with the second sensor fibre B7, and the end of the second sensor fibre B7 connects the second faraday rotation mirror B8; The input end of the 8th Coupler A4 is connected with the input end of the 9th Coupler A7 by phase-modulator A5, delay winding A6 successively, and two output terminals of the 9th Coupler A7 are connected with the output port H of the 4th Coupler C6, the output terminal M of the 7th Coupler B6 respectively.Coupler in the present embodiment is 1 * 2 Coupler.

As shown in Figure 1, outer diameter tube 174mm in the present embodiment, the pipe leakage aperture is 3mm, inner pipe water pressure is 0.35MPa, Leak hole is 4km apart from faraday rotation mirror apart from S, and sensor fibre is healthy and free from worry Single Mode Fiber (SMF-28), and delay winding is 4km, light source power 20mw, each Coupler splitting ratio is 1: 1.The leakage point and the second sensor fibre B7 are on the same bus of pipeline when testing in the present embodiment, so have only the second sensor fibre B7 can sense leakage signal, the first sensor fibre C7 deviates from the leakage point position, and induction is less than the leakage point signal.

The time domain waveform that Fig. 2 obtains for the leakage signal light modulated phase place that obtains after handling through Signal Analysis System, the leakage signal spectrogram of Fig. 3 for demonstrating after handling through Signal Analysis System, one tangible trough is arranged among the figure, and cursor shows that minimum point frequency herein is 12.451kHz, according to formula ${\mathrm{\ω}}_s{\mathrm{\τ}}_s=\frac{\mathrm{\π}(1+n)}{2}$ (getting n=1) can determine that it is 2.008 * 10 that light wave propagates into the used time of faraday rotation mirror from leakage point ^-5The speed that s, light propagate in optical fiber is 2 * 10 ⁸M/s, both distances that just can obtain passing to from leakage point faraday rotation mirror that multiplies each other are 4.016km.Absolute error is 16m, and relative error is 0.4%.

Claims (1)

1. pipeline leakage monitor based on the Sagnac fibre optic interferometer, it is characterized in that: this device mainly includes signal emission and processing system (1), distributed optical fiber sensing system (2), Signal Analysis System (3), and the signal emission includes broadband continuous light source (A1), first Coupler (A3), the 5th Coupler (B2), second Coupler (C2), first photoelectric converter (C9), second photoelectric converter (B9), first A/D converter (C10), second A/D converter (B10) composition again with processing system (1); Distributed optical fiber sensing system (2) includes the 3rd Coupler (C4), the 4th Coupler (C6), the 6th Coupler (B4), the 7th Coupler (B6), the 8th Coupler (A4), the 9th Coupler (A7), phase-modulator (A5), delay winding (A6), first faraday rotation mirror (C8), second faraday rotation mirror (B8); Signal Analysis System (3) includes computer (A8); Wherein, the signal emission is connected by the input end of first Single Mode Fiber (A2) with first Coupler (A3) with the broadband continuous light source (A1) of processing system (1), and two output terminals of first Coupler (A3) are connected with an output terminal of second Coupler (C2), an output terminal of the 5th Coupler (B2) by second Single Mode Fiber (C1), the 3rd Single Mode Fiber (B1) respectively; The input end of second Coupler (C2) is connected with the input end of the 3rd Coupler (C4) by first guiding fiber (C3), and another output terminal of second Coupler (C2) is connected with computer (A8) by first photoelectric converter (C9), first A/D converter (C10) successively; The input end of the 5th Coupler (B2) is connected with the input end of the 6th Coupler (B4) by second guiding fiber (B3), and another output terminal of the 5th Coupler (B2) is connected with computer (A8) by second photoelectric converter (B9), second A/D converter (B10) successively; An output terminal of the 3rd Coupler (C4) is connected with the output port G of the 4th Coupler (C6) by the 4th Single Mode Fiber (C5), another output terminal is connected with the output port E of the 8th Coupler (A4), the input end of the 4th Coupler (C6) is connected with first sensor fibre (C7), and the end of first sensor fibre (C7) connects first faraday rotation mirror (C8); An output terminal of the 6th Coupler (B4) is connected with the output port N of the 7th Coupler (B6) by the 5th Single Mode Fiber (B5), another output terminal is connected with the output port F of the 8th Coupler (A4), the input end of the 7th Coupler (B6) is connected with second sensor fibre (B7), and the end of second sensor fibre (B7) connects second faraday rotation mirror (B8); The input end of the 8th Coupler (A4) is connected with the input end of the 9th Coupler (A7) by phase-modulator (A5), delay winding (A6) successively, and two output terminals of the 9th Coupler (A7) are connected with the output port H of the 4th Coupler (C6), the output port M of the 7th Coupler (B6) respectively.

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