CN102997063A - Natural gas pipeline leakage monitoring method based on optical fiber sensing - Google Patents

Abstract

The invention provides a natural gas pipeline leakage monitoring method based on optical fiber sensing. Optical interference type leakage sensors are arranged on a pipeline body at certain intervals to continuously monitor a vibration wave signal in real time, which is transmitted along the pipeline body; the collected vibration wave signal is subjected to analysis and process, including type identification and vibration source positioning; the type identification is used for extracting and analyzing a vibration wave characteristic to judge whether the vibration wave characteristic belongs to a leakage type; meanwhile, time delaying of transmitting vibration waves to adjacent optical fiber sensors is combined with a transmission speed of the vibration waves on the pipeline body to realize the positioning of a vibration wave source; and each sensor adopts an optical fiber interferometer structure, and an optical fiber Michelson interferometer or an optical fiber Mach-Zehnder Interferometer is used as a leakage vibration wave detection sensor. The natural gas pipeline leakage monitoring method based on the optical fiber sensing has high sensitivity and high positioning accuracy.

Description

A kind of natural gas line leakage method based on Fibre Optical Sensor

Technical field

The present invention is a kind of natural gas line leakage method based on Fibre Optical Sensor.Relate to the measurement of mechanical vibration, measurement and the pipe-line system technical field of impact.

Background technique

At present, the pipeline overall length of building up in the world reaches 2,500,000 kilometers, and having surpassed the railway total kilometrage becomes the main means of transportation of world energy sources, and the oil product of developed country and oil-producing area, the Middle East transports all realizes channelization.China's pipeline has also obtained very fast development in recent years, overall length is also above 70,000 kilometers, begun to take shape across thing, stretch from the north to the south, cover the whole nation, be communicated with the overseas large general layout of energy pipe network, pipeline transport becomes the major way of the allotment conveying of the strategic energy such as oil gas.

Pipeline is subjected to the reasons such as natural disaster, third party's breakage in installation owing to cross-regional wide, has caused more pipe leakage accident to occur.External pipe safety situation also allows of no optimist very much, and the natural gas line big bang occurs in U.S. San Bruno city on September 9th, 2010, and blast causes long 51 meters, wide 9 a meters hollow place on the road surface.The pipeline of about 8 meters of one segment length, 76 centimetres of diameters is exploded the Heaven, flies out about 30 meters far away, and causes large-range fire disaster, causes 4 people dead, and 3 people are missing, and at least 52 people are injured, 4 hectares of burnt areas, and tens of houses are burnt.People's safety, environmental consciousness significantly promote in recent years, are also more and more paid attention to as the pipeline transportation safety problem of high risk industries.

Only have the sound wave monitoring method comparatively effective for natural gas line leakage in the ripe technology at present, but in order to improve the real-time of leakage monitoring and the accuracy of leak source location, the layout density that must add at pipeline large sensor, increase simultaneously corresponding power supply, communications equipment, cause system cost and installation and maintenance costly.

Along with the development of sensory technique has been carried out the research of SCADA leakage monitoring system such as companies such as U.S. CSI, ATMOSI, European TER abroad, Sensornet company has also developed the leakage monitoring system based on distributed optical fiber temperature sensor, and portioned product has also been applied for patent protection at home; The units such as domestic University Of Tianjin, Tsing-Hua University, China Renmin People's Liberation Army Office Support Engineering Academy also further investigate the leakage monitoring method of pipeline.

Patent CN200410020046.6 discloses a kind of distribution type fiber-optic method for monitoring leak from oil gas pipe and monitoring device based on principle of interference.This monitoring system requires to lay side by side an optical cable at Near Pipelines along pipeline, utilizes the optical fiber in the optical cable to form a Fiber optic micro-vibration sensor.Patent CN200620119429, CN200610113044.0 are the pipeline leakage monitor based on the Sagnac fibre optic interferometer, and patent CN200610072879.6 is a kind of pipeline leakage monitor based on distributed optical fiber acoustic sensing technology and method.

" sensor and micro-system " the 7th phase of the 26th volume " based on the gas pipeline leakage detection method of distributed fiberoptic sensor " discloses a kind of gas pipeline leak detecting device and method based on distributed fiberoptic sensor.

CN1837674A discloses a kind of pipeline leakage testing device and method based on distributed optical fiber acoustic sensing technology.

US2006/0225507A1 discloses a kind of pipeline leakage testing device and method based on distributed fiberoptic sensor.

Above-mentioned technology all belongs to the distributed optical fiber sensing monitoring method.But such technical monitoring is subject to the impact of the interference incident that pipeline occurs when leaking, have very high system's false alarm rate, and antijamming capability is relatively poor.

Summary of the invention

The objective of the invention is to invent the natural gas line leakage method based on Fibre Optical Sensor that a kind of sensitivity and degree of accuracy are high, false alarm rate is low, be not subject to such environmental effects.

In view of above-mentioned a few class Leak testtion, the sensitivity that monitoring technology exists is low, false alarm rate is high, be subject to the problems such as such environmental effects, the present invention provides the quasi-distributed leakage vibration monitoring of a kind of high sensitivity based on Fibre Optical Sensor method, adopt high sensor so that can little leakage occur when pipeline, the leakages such as seepage were in time monitored during the primary stage, and in conjunction with the time domain of incident of leakage, frequency domain character effectively reduces and disturbs the system's false alarm rate that causes, this technological scheme has overcome poor accuracy in the monitoring technology before this and the deficiency of mounting process complexity, so that the related maintenance personnel can in time take counter-measure, avoid causing larger security incident.

Can produce the sound wave of each frequency range behind the pipe leakage, just gradually by Absorption of Medium, and wavelength is shorter in the not far position of distance sound source for the short ultrasound of wavelength ratio, attenuation by absorption also faster, only have the distant of low-frequency sound wave and infrasonic wave propagation, can propagate a few km to tens kms.Adopt at present and the system of infrasonic sensor is being installed because the available signal frequency range is narrower than the long pipeline two ends, to the accurate positioning effect of leakage signal not enough.

The present invention proposes a kind of highly sensitive quasi-distributed optical fiber sensing leakage vibration monitoring method that has, it is that a high sensitivity optical fiber interference type leak sensor is installed on pipeline body at a certain distance, the leakage vibration wave signal that continuous real-time monitoring is propagated along pipeline body, the vibration wave signal that gathers is carried out analysing and processing, comprise type identification and leak the vibration source location, wherein whether type identification is for to belong to leak type by the extraction and analysis of vibration wave feature being differentiated it, the time lag that simultaneously propagates into adjacent several optical fiber transducers according to vibration wave realizes the determining of vibration wave source position in conjunction with the velocity of propagation of vibration wave on pipeline body, and realizing above-mentioned provides the position information of leakage point simultaneously to after the vibration wave signal analysis and processing incident of leakage being reported to the police.The present invention has suitably increased the quantity of optical fiber transducer on employing high sensitivity optical fiber sensor improves the basis of incident of leakage monitoring sensitivity, expanded the frequency range that to pick up monitor signal, and estimated that in conjunction with the time delay that a plurality of optical fiber transducers carry out localization method has guaranteed the accuracy of system location.

In the present invention, sensor is the key that realizes line leakage, and when pipeline occurs to leak, leaking the vibration wave that excites will propagate to the leakage point both sides along pipeline.A sensor is installed on pipeline body at a certain distance, is used for monitoring the leakage vibration wave on the pipeline.Sensor adopts the fibre optic interferometer structure, can be optical fiber Michelson interferometer or fiber Mach-Zehnder interferometer, for the induction sensitivity that increases leaking vibration can be by increasing the mode of sensor fibre length, the light intensity signal of its output can be write as after photoelectric conversion:

V ₀∝1+Vcos(φ _s+φ _n+φ ₀)+V _n (1)

Wherein, V ₀Be the voltage signal of output, V is the visibility of interferometer, V _nThe circuit additional noise, φ _sServe as reasons and leak the phase difference signal that vibration wave causes, be the leakage vibration wave signal that to survey, φ ₀Being the initial phase of interferometer, is a constant, φ _nBeing the low frequency wonder of phase difference, is a Uncertainty, changes with temperature and external environment impact.Can realize leaking the vibration wave signal psi by the demultiplexing technology that is complementary with the modulation of source mode _sObtain, and to this signal psi _sThe time lag that arrives corresponding sensor estimates, realized that along the speed v of pipe transmmision to the vibration wave source be determining of leakage point position in conjunction with vibration wave.

In order to save input, in based on the natural gas line leakage method of Fibre Optical Sensor, adopt optical fiber transducer multiplex/demultiplex method.The method of the comprehensive frequency division multiplexing of the method and space division multiplexing, employing produces leak detection light to the method that tunable laser carries out the optical frequency modulation, use Michelson interferometer as leak sensor, the laying structure of sensor is that a leak sensor is installed on the natural gas tube pipeline outer wall at a certain distance, a plurality of sensors consist of a sensor group, and the optical signal of each sensor group uses an optical fiber to pass system host back.Each sensor in the sensor group is made into the poor different Michelson interferometer of light arm or Mach-Zehnder interferometer, the sense light signal frequency that each leak sensor is produced is all not identical, utilizes thus the frequency division multiplexing principle optical multiplexed signal of a plurality of sensor different frequencies of every group can be used in the receiving terminal of passing system in the optical fiber back; And employing space division multiplexing mode difference connecting system main frame between a plurality of sensor groups.The optical signal of each the sensor group that receives uses independent photoelectric conversion passage to realize that optical signal is to the conversion of electrical signal, transducing signal after the conversion uses the frequency division mode to realize the demultiplexing of each sensor in the sensor group, and adopt the phase carrier technology to demodulate the original acoustic signals of pipe leakage, pass through again identification and the positioning analysis of leakage signal, but final Obtaining Accurate pipe leakage dot information.The phase carrier demodulation method that leaks acoustic signals is the interference signal that will receive, and carries out first bandpass filtering, one tunnel output and cos (ω ₀T) carry out lower pass-filter and differential after multiplying each other and process another road and sin (ω ₀T) carrying out lower pass-filter and differential after multiplying each other processes; Behind the output of the differential on last road and rear one tunnel the lower pass-filter output multiplication, subtract each other with rear one tunnel the differential output result with last lower pass-filter output multiplication again, process through integration, high-pass filtering successively afterwards, finally export original leakage vibration wave signal.

In fact, in the Michelson interferometer optical fiber with the corresponding refractive index n of two polarization modes _xAnd n _yUnequal, simultaneously because the variation of little curved, the distortion of optical fiber, ambient temperature makes n _xAnd n _yChange at random causes optical fiber output polarization state change at random, is reflected in interference signal visibility V change at random between 0～1, and this phenomenon is the polarization inducement signal fade-out of interferometer.This phenomenon will cause the reduction of Michelson interferometer sensor detection sensitivity and signal to noise ratio and unstable.In order to overcome the polarization decay of sensor group, in based on the natural gas line leakage method of Fibre Optical Sensor, adopt the anti-polarization decay method of gas pipeline leakage detecting sensor group.The anti-polarization decay method of this gas pipeline leakage detecting sensor group is that the sensor of a Michelson interferometer structure is installed on pipeline body at a certain distance, by the sensor of several Michelson interferometer structures by beam splitter and bundle-mixer and be connected in launching fiber and passback optical fiber between; Two arms of Michelson interferometer are not isometric, each Michelson interferometer uses two faraday rotation mirrors as reflector, angle of swing is 45 degree, and the polarization state that makes catoptrical polarization state variation just in time offset incident light changes, thereby makes the visibility of interferometer remain 1.

In addition, in the formula (1), because low-frequency disturbance φ _nChange at random, and amplitude is large, is subjected to φ _nVariable effect, the signal to noise ratio of system's output is changing, and as sin φ _n=0 o'clock, the complete blanking of signal, this namely is called the phase fading phenomenon of interferometer.

In order to eliminate the phase fading phenomenon of sensor, adopt the phase carrier technology to detect the leakage acoustic signals.Specific as follows:

When making Michelson interferometer, make interferometer two arms not isometric, two arm length difference are Δ L;

With sawtooth wave or fall sawtooth signal as modulation signal, frequency is for leaking the twice of sound wave frequency bandwidth, be applied to the adjustable laser of optical frequency, the laser that laser output optical frequency changes synchronously according to modulation signal, be input to Michelson interferometer, because two arms are not isometric, laser by two arms will produce delay inequality, thereby the two bundle laser that participate in interfering are except the sawtooth wave falling edge, other optical frequencies constantly are poor to be a constant, therefore, the interference signal of interferometer output is the cosine signal of an approximate single-frequency, angular frequency ₀Two arm length difference Δ L are directly proportional with interferometer, and Δ L is larger, and the interference signal frequency is higher;

Use band-pass filter that interference signal is carried out filtering, the filter center frequency is the interference signal CF center frequency, and bandwidth is identical with the saw wave modulator signal frequency.Can obtain the carrier signal of this interferometer after the filtering, but according to the phase fading problem of aforesaid phase carrier demodulation method demodulation erasure signal, obtain original leakage acoustic signals.

In order to overcome the phase fading of sensor group, in based on the natural gas line leakage method of Fibre Optical Sensor, adopt a kind of anti-phase fading method for the gas pipeline leakage fiber optic detection system.The anti-phase fading method of this gas pipeline leakage fiber optic detection system is: the sensor of a Michelson interferometer or mach-zehnder interferometer configuration is installed on pipeline body at a certain distance, by several sensors by beam splitter and bundle-mixer and be connected in launching fiber and the passback optical fiber between; Based on sawtooth wave or fall the laser of saw wave modulator as light source, and the long Michelson interferometer of unequal arm or Mach-Zehnder interferometer are as sensor, in sensor signal, produce the cosine signal carrier wave of approximate single-frequency, sensor group signal carrier is the linear superposition of each sensor carrier signal, by dividing method each sensor carrier signal is separated, use with each sensor carrier signal and with cosine and sinusoidal signal frequently carrier signal is carried out demodulation, obtain the original leakage acoustic signals of each sensor.

Position for the accurate locating leaks in pipes of energy, in based on the natural gas line leakage method of Fibre Optical Sensor, adopt a kind of multisensor localization method based on quasi-distributed optical fiber sensory technique gas pipeline leakage event, when the pipe leakage event occurs, leak the excited vibrational ripple and propagates to two opposite directions along pipeline, system propagates into the delay inequality realization of adjacent several sensors to the location of leakage point according to leakage signal.When leak occuring, leak and excite pipeline to produce vibration wave, along pipe transmmision, wherein two adjacent sensors are spaced apart setting value L to vibration wave with speed V, and establishing the time that signal is transmitted to sensor n is t _n, the time that is transmitted to sensor n+1 is t _N+1, the time that signal is transmitted to sensor n-1 is t _N-1, the time that is transmitted to sensor n+2 is t _N+2, have following formula (2) to set up:

${\mathrm{<figure-callout\; id="1"\; label="X"\; filenames="HDA0000091200780000021.png,HDA0000091200780000022.png"\; state="\{\{state\}\}">X</figure-callout>}}_1=\frac{1}{2}[L-v\&times;(t_{n+1}-t_n)]$

${\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="HDA0000091200780000021.png,HDA0000091200780000022.png"\; state="\{\{state\}\}">X</figure-callout>}}_2=\frac{1}{2}[v\&times;(t_{n-1}-t_{n+1})]$ (2)

${\mathrm{<figure-callout\; id="3"\; label="X"\; filenames="HDA0000091200780000022.png,HDA0000091200780000031.png"\; state="\{\{state\}\}">X</figure-callout>}}_3=L-\frac{1}{2}[v\&times;(t_{n+2}-t_n)$

${\mathrm{<figure-callout\; id="4"\; label="X"\; filenames="HDA0000091200780000031.png"\; state="\{\{state\}\}">X</figure-callout>}}_4=\frac{1}{2}[L-v\&times;(t_{n+2}-t_{n-1})]$

Unknown parameter (t wherein _N+1-t _n), (t _N-1-t _N+1), (t _N+2-t _n) and (t _N+2-t _N-1) be respectively to leak the delay inequality that vibration wave arrives sensor n and n-1, sensor n+1 and n-1, sensor n and n+2, sensor n-1 and n+2, can carry out correlation analysis by the signal that the several sensors of correspondence are received obtains, so just formed four detections to same unknown quantity event occurrence positions X, measured value is respectively X ₁, X ₂, X ₃, X ₄, these four measured values are got assembly average, namely obtain final measured value X.It is poor that a plurality of sensors of combined continuous receive signal time, compares the time difference measurements mode that only adopts two sensors and have more accurately locating effect.This localization method can be monitored burst or given vent to leakage signal, has the advantages such as accurate positioning is good, stable performance.

Suppress for Environmental Random Vibration is disturbed, in based on the natural gas line leakage method of Fibre Optical Sensor, adopt a kind of intelligent identification Method of gas pipeline leakage event.Temporal signatures P with the normal operation of pipeline and leakage status signals _t, frequency domain character P _fNoise characteristic P with current pipe transmmision signal _nAnd comprehensively analyze in conjunction with waveform recognition, set up and leak confidence coefficient functional model: R=a ₁P _t+ a ₂P _f-a ₃P _n, the vibration wave signal that picks up is leaked assessment judge whether pipeline leaks, according to on-the-spot pipeline characteristics algorithms of different parameter a is set ₁, a ₂, a ₃Regulate the confidence coefficient model.At random accidental vibration and sudden, persistency leakage signal have effectively been distinguished in this identifying method, have improved the accuracy rate of system alarm.

In order to measure pipe leakage vibration wave velocity of propagation, in based on the natural gas line leakage method of Fibre Optical Sensor, adopt a kind of measuring vibration wave propagation velocity in case of natural gas pipeline leakage method: be to be based upon on the basis of natural gas line leakage method of Fibre Optical Sensor; Use the natural gas line leakage system, select some known sensor points to cause vibration by knocking the form simulation pipe leakages such as pipeline, quantity according to the pipe section that uses in engineering construction and the examination data, the leakage signal that propagates into two adjacent sensors is carried out that time delay is estimated and realized leaking the mensuration of vibration wave speed in conjunction with known duct length, accurately provide the distance of two adjacent sensor points of current test point distance, with this simulation test point position X substitution: X=L-[v * (t _N+2-t _n)]/2, counter solving: v=2 (L-X)/(t _N+2-t _n), realize measuring vibration wave along the speed of pipe transmmision according to the signal propagation time of known sensor span and mensuration.

A kind of determining method of natural gas line absolute growth also is provided simultaneously, the pipeline that at first excavates position to be measured buries soil, knock the vibration of pipeline simulation pipe leakage at this point, measure the position of analog site, X=[L-v * (t according to known simulated leakage vibration wave along the signal propagation time of the speed of pipe transmmision and mensuration _N+1-t _n)]/2, thereby realized the measurement of pipeline absolute distance.

Formation based on the natural gas line leakage system of Fibre Optical Sensor is seen Fig. 1, and it comprises light path system and circuit two-part; An optical fiber transducer is installed on pipeline body at a certain distance, adjacent a plurality of optical fiber transducers consist of an optical fiber transducer group, each optical fiber transducer group shares a launching fiber and is connected with light source, and each optical fiber transducer group uses a passback optical fiber to be connected with photodetector; Photodetector output connects signals collecting and the puocessing module that comprises leakage signal identification and state event location function, and signals collecting and puocessing module output connect microcomputer by external interface.Through the processing of signals collecting and puocessing module, the sensor group signal that mixes based on the frequency division multiplexing mode has been realized the demultiplexing of each sensor in the sensor group, obtains original leakage vibration wave signal.

In order to protect optical fiber transducer, optical fiber transducer guard shield 16 is installed outside optical fiber transducer; Optical fiber transducer guard shield 16 is a bottom indent and the radian cover consistent with pipeline external surface.

Send laser by light source, after the transmission light path realizes beam splitting, part light is transferred to the optical fiber transducer group that is installed on the tube wall, the optical fiber transducer group is picked up behind the leakage oscillating signal and noise of pipe transmmision, again be transmitted back to the photodetector of system through the transmission light path, carry out leakage signal demodulation and discriminance analysis by signals collecting and puocessing module, and leakage signal is carried out time delay estimate that realization is to the location of leakage point.

The light path system of this natural gas line leakage system (seeing Fig. 4) mainly is based on the frequency division multiplexing principle and designs, and is made of light source, light path ABAP Adapter, transmission cable and optical fiber transducer three parts; The light path ABAP Adapter is comprised of beam splitter and combiner device; Optical fiber transducer adopts Mach-Zehnder interferometer or Michelson interferometer; Each optical fiber transducer connects the light path ABAP Adapter by two optical fiber, and all light path ABAP Adapter are connected in series successively with transmission cable, by the nearest light path ABAP Adapter welding system main frame of distance receiving terminal.

The flow process of whole light path system is: the launching fiber of light source in transmission cable sends exploring laser light, after arriving first light path ABAP Adapter, be divided into two bundle laser by the beam splitter of this light path ABAP Adapter: a branch ofly enter first optical fiber transducer through launching fiber, light beam passes to next light path ABAP Adapter through time delay optical fiber in addition, be divided into two bundle laser by the beam splitter in the next light path ABAP Adapter again, a branch ofly enter second optical fiber transducer, another Shu Zaijing optical fibre transmission is to next light path ABAP Adapter, by that analogy, until laser arrives last optical fiber transducer; At last optical fiber transducer of sensor group, laser no longer by beam splitter, directly enters optical fiber transducer; And through the optical signal behind each optical fiber transducer, the combiner device by in the corresponding light path ABAP Adapter separately passes the optical signal of coming with the back and closes bundle, is back to the signal receiving end of monitoring system finally by the passback optical fiber transmission of corresponding sensor group.Wherein said light path ABAP Adapter has been gathered beam splitter and combiner device; Launching fiber and passback optical fiber use is two different fibre cores in the same transmission cable; Transmission cable is together in series all light path ABAP Adapter; The length of the launching fiber on the pipeline between adjacent two sensors and passback optical fiber all is greater than 1/2 of laser coherent length, to reach the purpose that prevents from occuring between the sensor signal cross-talk.

For above-mentioned natural gas pipeline leakage optical fiber monitoring system, the invention discloses the special light source system of a kind of suitable multiplexed optical wave usefulness and modulation /demodulation.This light-source system consists of (seeing Fig. 2) by optical frequency adjustable laser and dedicated modulation signal generating module; The signal that produces in the modulation signal generation module is exported by DA, connects the laser modulation signal input part; Modulation signal generation module output signal has frequency adjustment, amplitude adjusted and sawtooth wave/selection function of falling the sawtooth wave, can select such as sawtooth wave or the signal type of falling the saw wave modulator by programming, adjusts signalization amplitude and frequency; Modulation signal acts on the laser, the continuous laser that exportable optical frequency changes according to modulation signal waveform rule.

Described light source is a kind of special light source system that is fit to multiplexing and modulation /demodulation that comprises, the semiconductor laser that the laser in the light source adopts optical frequency to modulate, and modulation signal acts on the laser Injection Current, realizes the modulation of optical frequency; The laser coherent length need to be poor greater than all the sensors interferometer brachium, and less than the time delay optical fiber length sum on launching fiber between adjacent two interferometers and the passback optical fiber.The modulation signal that the modulation signal module outputs to laser is sawtooth signal or the sawtooth signal of falling, and frequency is not less than the twice of leakage acoustic signals frequency to be detected; When injecting sawtooth wave or the optical frequency of falling sawtooth wave modulated laser, the interference signal of each sensor output is single-frequency cosine signal or approximate single-frequency cosine signal, the interference light signal of sensor group output is the stack of the approximate single-frequency cosine signal of each sensor output in the sensor group, its frequency spectrum is comprised of a plurality of independently spectral lines, and spectral line quantity is identical with sensor group inner sensor quantity;

Modulation signal generation module in the light source adopts digital form to realize, namely calculate the modulation signal segment that obtains one-period by digital form according to wave mode, signal amplitude, frequency parameter, then export by digital-to-analog conversion (DA) mode, the modulated-analog signal of output is connected on the laser, can select such as sawtooth wave or the signal type of falling the saw wave modulator capable of regulating signalization amplitude, direct current biasing and frequency by parameter configuration; Laser after modulation output optical frequency is input in the sensing light path with the laser that the modulation signal synchronous waveform changes, and can realize multiplexing, the signal carrier that forms a plurality of sensors of sensor.

Wherein the modulation of source circuit as shown in Figure 3, it is mainly by operational amplifier U7, Distributed Feedback Laser U8, operational amplifier U9 and 2 triode Q4, Q5 groups; The 7 termination VDC of U7, connect again with the circuit of capacitor C 38 parallel connections after connecting with diode D8, capacitor C 41 behind the 6 terminating resistor R18, meet VDC behind the 6 terminating resistor R19, connect again simultaneously the ground that is connected in series to of diode D4, D5, D6, D7,4,7,8,9,10 end ground connection, 3 ends are ground connection after resistance R 17,2 ends and the end that meets U8; 1, the 14 end ground connection of U8,12 ends are through capacitor C 34 ground connection, 5,11 termination VDC, 4 termination PDne, 6 termination TEC+, 3 ends are through choke coil L3 and the collector electrode that meets triode Q4 after resistance R 20 is connected, and 3 ends are through choke coil L3 and the collector electrode that meets triode Q5 after resistance R 21 is connected simultaneously; Between 1,2 ends of U9 after shunt resistor R22 and the capacitor C 39 by 1 terminating resistor R25 to 6 ends, Pdne connecting resistance R30 again series resistors R27 connects 3 ends of U9, the ground connection of connecting after the resistance R 30 that meets simultaneously Pdne and potentiometer resistance R31, resistance R 32, the capacitor C 43 three's parallel connections, 5 ends meet VREF through resistance R 24, and 7 ends connect capacitor C 45 to ground through resistance R 28 and 8 ends altogether through resistance R 26; Pick out the base stage through diode D11, D12 to Q4 from the upper end of capacitor C 45, base stage connects capacitor C 44 to ground simultaneously, connects with resistance R 29 through diode D10 simultaneously and also arrives ground, and the base stage of Q4 connects the base stage of Q5, and the grounded-emitter connection of Q4, Q5.

The relative modulation principle of this light-source system, natural gas pipeline leakage optical fiber monitoring system has adopted the vibration wave demodulation principle block diagram of optical fiber transducer multiplex/demultiplex method to see Figure 13, interference signal output tape splicing pass filter, bandpass filtering export one the tunnel with cos ω ₀T joins and connects the first lower pass-filter after (multiplying each other), and this lower pass-filter output connects the first differentiator, another road and sin ω ₀T joins, and connects the second lower pass-filter after multiplying each other, and this lower pass-filter output connects the second differentiator; The output of the first differentiator and the output of the second lower pass-filter are joined, and join with the output of the second differentiator and the output of the first lower pass-filter after multiplying each other again, and join after multiplying each other again, and successively through integration, high-pass filtering, export acoustic signals after subtracting each other.

The formation of described signals collecting and puocessing module is seen Fig. 6, and it comprises that signal condition unit, signal gathering unit, processing unit, terminal show and external interface that processing unit comprises recognition circuit and positioning circuit; The signal of photodetector output is connected in series signal condition unit, signal gathering unit and processing unit successively, the signal of collecting unit collection is carried out demultiplexing to processing unit and demodulation obtains original vibration wave signal, then in recognition circuit and positioning circuit, carry out respectively leakage signal identification and the location of leakage point; Processing unit output has video terminal and external interface;

Wherein the conditioning unit circuit as shown in Figure 7, it mainly is comprised of operational amplifier U14, photoelectric diode U15; 1,5,8 ends of U15 are unsettled, 3,4 end ground connection, and 2 ends connect 6 ends after resistance R 39, capacitor C 60 the two parallel connection, and 6 ends connect 3 ends of U14,8 ends of 7 termination U14 through resistance R 43; The 4 end ground connection of U14,5 ends are unsettled, and 6,7 ends meet AD_VINI altogether, and 1 termination AD_OUT mouth, 2 ends be through resistance R 42 ground connection, the two parallel connection of connecting resistance R40 between 1,2 ends, capacitor C 59;

Recognition circuit in the processing unit as shown in figure 14, it mainly is comprised of DSP digital signal processor U1B and peripheral circuit, the NC1-NC15 pin of U1B is unsettled; AVDD, AGND are the analog power input, and AVDD connects the 1.3V power supply by magnetic bead FER1, and 3 capacitor C 22, C23, C24 in parallel carry out decoupling filtering between AVDD and AGND; DAI1, DAI3, DAI4 are connected with DR0PRI, RSCLK0, the RFS0 of positioning circuit DSP digital signal processor U10 respectively and are used for data transfer; DAI9-DAI20 is expansion interface; DPI9, DPI10 connect external interface circuit;

Positioning circuit in the processing unit as shown in figure 15, it mainly is comprised of DSP digital signal processor U10 and peripheral circuit and interface, the DR0PRI of U10, RSCLK0, RFS0 are connected with DAI1, DAI3, the DAI4 of recognition circuit DSP digital signal processor U1B respectively and are used for receive data, RX, TX, MOSI, MISO, SCK connect the video terminal interface, and TCK, TDO, TDI, TMS, TRST#, EMU# are debugging interface.

Described sensor adopts Michelson interferometer.Each optical fiber transducer is according to equidistantly being installed in pipe surface; Every 2-10 adjacent sensor forms a sensor group, each sensor adopts parallel way to be connected to transmission fiber (being launching fiber and passback optical fiber) in every group, the place that each sensor is connected with transmission fiber uses beam splitter and bundle-mixer to realize the beam splitting of light and close bundle (being the light path ABAP Adapter), and the transmission fiber length between adjacent two sensors is greater than 1/2 of laser coherent length; The corresponding photoelectric conversion passage that independently interference light signal of each sensor group is converted to electrical signal of each sensor group.

The I type structure of described optical fiber transducer is seen Figure 10, and I type structure is test tube road radial vibration signal, and each sensor comprises: elastic cylinder, fibre optic interferometer and tail fiber coiling box; Wherein, the interference arm of uniform sequential winding optical fiber interferometer on the elastic cylinder periphery, and with tackiness agent optical fiber and cylindrical body are bonded together, remaining fibre optic interferometer and related device thereof are with neat being coiled in the tail fiber coiling box after twining; The tail fiber coiling box is fixed on the elastic cylinder top by tackiness agent.Described elastic cylinder bottom indent, and radian is consistent with pipeline external surface.The radial vibration that produces during gas pipeline leakage allows elastic cylinder generation deformation, drives the fibre optic interferometer that the elastic cylinder periphery twines deformation also occurs, and changes thus the state of the light of transmission in the optical fiber, so that is arrived by the leakage monitoring Equipment Inspection.

The another kind of optical fiber transducer II type structure that is used for natural gas line leakage axial vibration signal is seen Figure 11, and this optical fiber transducer is comprised of rectangular spring sheet, fibre optic interferometer and tail fiber coiling box; Concrete structure is on the rectangular spring sheet, the fiber optic interferometric arm of fibre optic interferometer is evenly laid with the shape of sine wave, and with tackiness agent optical fiber is close on the rectangular spring sheet, remaining fibre optic interferometer and related device thereof are with neat being coiled in the tail fiber coiling box; The tail fiber coiling box is fixed on above the rectangular spring sheet by tackiness agent.Described rectangular spring sheet is a bottom indent and the radian steel sheet consistent with pipeline external surface; The axial vibration that produces during gas pipeline leakage allows rectangular spring sheet generation deformation, drives the fibre optic interferometer that the rectangular spring sheet coils above deformation also occurs, and changes thus the state of the light of transmission in the optical fiber, so that is detected by rear end equipment.

Wherein have the sponge layer in the shell of two kinds of sensors, mainly play isolating pipelines wall external interference signal and fixing protection sensor.

Theory diagram based on monitoring system of fiber optical sensing natural gas pipeline path multiplexing structure is seen Figure 12, optical fiber is penetrated in light source sending and receiving after the dedicated modulation signal generating module, launching fiber is connected in series a plurality of light path ABAP Adapter, each light path ABAP Adapter connects an optical fiber transducer by an optical fiber, a plurality of optical fiber transducers are an optical fiber transducer group, each is connected to photoelectric converter by a passback optical fiber again by an optical fiber and after connecing the optical fiber transducer of each optical fiber transducer group, and photoelectric converter output connects signals collecting and puocessing module.

The present invention is with the optical fiber transducer that need not the to power pick device as leakage signal, utilize the signal remote transmission that realizes optical fibre vibration sensor with optical fiber and the Optical multiplexing technology of ditch laying with pipeline, solved the difficult problem of electric transducer power supply and telecommunication, laying optical fiber vibration transducer comparatively thick and fast, multisensor are united and are carried out time delay and estimate to improve Location accuracy to leakage point; The sensitivity of optical fibre vibration sensor is the several times of traditional sonic transducer in addition, can significantly improve the degree of accuracy that the natural gas line minute leakage is detected;

And false alarm rate is low, be not subject to the impact of environmental factor.

Description of drawings

Fig. 1 monitoring system of fiber optical sensing natural gas pipeline theory diagram

The modulation principle figure of Fig. 2 optical frequency adjustable type light source

Fig. 3 modulation of source circuit diagram

Fig. 4 monitoring system of fiber optical sensing natural gas pipeline light path system

Fig. 5 light path adapter structure and transmission index path

Fig. 6 signals collecting and puocessing module structural drawing

Signal condition element circuit figure in Fig. 7 signals collecting and the puocessing module

Fig. 8 Michelson's interferometer type Fundamentals of Sensors figure

Fig. 9 Mach-Zehnder interferometer Fundamentals of Sensors figure

Figure 10 optical fiber transducer I type structural drawing

Figure 11 optical fiber transducer II type structural drawing

Figure 12 monitoring system of fiber optical sensing natural gas pipeline path multiplexing structural drawing

Figure 13 monitoring system of fiber optical sensing natural gas pipeline vibration wave demodulation principle block diagram

Signal processing unit recognition circuit figure in Figure 14 signals collecting and the puocessing module

Signal processing unit positioning circuit figure in Figure 15 signals collecting and the puocessing module

Wherein 1,1-1 ..., 1-n-beam splitter 2,2-1 ..., 2-n, 15-optical fiber transducer

3,3-1 ..., 3-n- combiner device 4,5,6,7,8,9-time delay optical fiber

10-tail fiber coiling box 11-transmission cable

12-elastic cylinder 13-sensor fibre

14-rectangular spring sheet 16-sensor shield

17-pipeline body 18-natural gas line external surface coating

The outer steel pipe walls of 19-natural gas line

Embodiment

In conjunction with the accompanying drawings and embodiments the present invention is further specified, but should not limit protection scope of the present invention with this.

Embodiment. the formation of this example is as shown in Figure 1, on pipeline body, every 1.5km an optical fiber transducer is installed, 10 sensors are installed altogether, front 5 sensors and rear 5 sensors consist of respectively a sensor group, an optical fiber in all optical fiber transducer group common transmitted optical cables is connected with system source, as launching fiber, simultaneously each optical fiber transducer group uses alone again optical fiber in the transmission cable to be connected with the system photodetector, as returning optical fiber; Photodetector output termination comprises signals collecting and the puocessing module of leakage signal identification and state event location function, and signals collecting and puocessing module output connect microcomputer by external interface.

This routine light path system (seeing Fig. 4) is based on the frequency division multiplexing principle and designs, and each optical fiber transducer connects the light path ABAP Adapter by two optical fiber, and all light path ABAP Adapter are connected in series successively with transmission cable, by the nearest light path ABAP Adapter welding system main frame of distance receiving terminal; Concrete optical routing light path ABAP Adapter, transmission cable and optical fiber transducer three parts consist of; The light path ABAP Adapter is comprised of beam splitter and combiner device; Optical fiber transducer adopts the interferometer of Michelson-structure.

Specifically linking as shown in Figure 5 between each optical member in the described light path system, the detection light process transmission fiber that light source sends enters the beam splitting apparatus 1-1 in the light path ABAP Adapter, it is 9: 1 that this beam splitting apparatus 1-1 adopts splitting ratio, wherein ratio is that 9 output light continues to propagate along time delay optical fiber 4, until light path ABAP Adapter 1-2, and being 1 output light, export ratio enters first sensor 2-1, sensor 2-1 adopts the Michelson's interferometer structure, arm is poor to be 5m, 3m long optic fiber on arm of this interferometer is wound on the elastomer of rubber material, elastomer is close to tube wall, adopts protective housing to fix; Beam splitting apparatus 12 among the light path ABAP Adapter 1-2 adopts 8: 1 splitting ratio, wherein ratio is that 8 output light continues to be transmitted to next light path ABAP Adapter along time delay optical fiber, and being 1 output light, export ratio enters second sensor 2-2, it is poor at 7.5m that this sensor adopts equally the Michelson's interferometer structure and controls interferometer arm, the optical fiber that 3m on the arm is long is wound on the elastomer of rubber material, and elastomer is close to tube wall and is fixed; By that analogy, all the other sensor brachium difference Wei 10m, 12.5m, 15m, beam splitting apparatus splitting ratio in the corresponding ABAP Adapter was respectively 7: 1,6: 1,5: 1,4: 1,3: 1,2: 1,1: 1, and during to last sensor, laser directly enters sensor after time delay optical fiber; The output of the sensor (2-1)-(2-4) in first sensor group respectively with front four ABAP Adapter in bundle-mixer return optical fiber and be connected with one, the splitting ratio of 4 bundle-mixers is respectively 4: 1,3: 1,2: 1,1: 1, each sensor is that 1 input end is connected with the bundle-mixer ratio all, sensor 25 outputs connect passback optical fiber, and then connect the bundle-mixer in the 4th ABAP Adapter; Similarly, the arm length difference of five sensors in second sensor group is respectively 5m, 7.5m, 10m, 12.5m, 15m, same bundle-mixer and another root passback optical fiber that passes through in the ABAP Adapter is connected, and the bundle-mixer splitting ratio is respectively 4: 1,3: 1,2: 1,1: 1; Two sensor groups use two passback optical fiber to be connected with two ALT-CH alternate channels of photoelectric conversion module respectively altogether;

Described light source is a kind of special light source system that is fit to multiplexing and modulation /demodulation that comprises, laser and the dedicated modulation signal generating module adjustable by optical frequency consist of (seeing Fig. 2); Modulation signal that light source adds is the sawtooth signal of frequency 10kHz, amplitude ± 1.4V, and the interference signal frequency spectrum of sensor group output mainly is made of 40kHz, 60kHz, 80kHz, 100kHz, five spectral lines of 120kHz; Use respectively CF center frequency to be 40kHz, 60kHz, 80kHz, 100kHz, 120kHz, the band-pass filter that bandwidth is 4.5kHz carries out filtering to interference signal, obtain the carrier signal of five sensors, corresponding main frequency is respectively 40kHz, 60kHz, 80kHz, 100kHz, 120kHz; Five carrier signals uses are carried out demodulation with cosine and sinusoidal signal frequently, obtain the leakage vibration wave signal of five sensors;

Wherein the modulation of source circuit as shown in Figure 3, it is mainly by operational amplifier U7, Distributed Feedback Laser U8, operational amplifier U9 and 2 triode Q4, Q5 groups; The 7 termination VDC of U7, connect again with the circuit of capacitor C 38 parallel connections after connecting with diode D8, capacitor C 41 behind the 6 terminating resistor R18, meet VDC behind the 6 terminating resistor R19, connect again simultaneously the ground that is connected in series to of diode D4, D5, D6, D7,4,7,8,9,10 end ground connection, 3 ends are ground connection after resistance R 17,2 ends and the end that meets U8; 1, the 14 end ground connection of U8,12 ends are through capacitor C 34 ground connection, 5,11 termination VDC, 4 termination PDne, 6 termination TEC+, 3 ends are through choke coil L3 and the collector electrode that meets triode Q4 after resistance R 20 is connected, and 3 ends are through choke coil L3 and the collector electrode that meets triode Q5 after resistance R 21 is connected simultaneously; Between 1,2 ends of U9 after shunt resistor R22 and the capacitor C 39 by 1 terminating resistor R25 to 6 ends, Pdne connecting resistance R30 again series resistors R27 connects 3 ends of U9, the ground connection of connecting after the resistance R 30 that meets simultaneously Pdne and potentiometer resistance R31, resistance R 32, the capacitor C 43 three's parallel connections, 5 ends meet VREF through resistance R 24, and 7 ends connect capacitor C 45 to ground through resistance R 28 and 8 ends altogether through resistance R 26; Pick out the base stage through diode D11, D12 to Q4 from the upper end of capacitor C 45, base stage connects capacitor C 44 to ground simultaneously, connects with resistance R 29 through diode D10 simultaneously and also arrives ground, and the base stage of Q4 connects the base stage of Q5, and the grounded-emitter connection of Q4, Q5;

Wherein: operational amplifier U7 selects AD623; Laser U8 selects the internal modulation semiconductor light sources; Operational amplifier U9 selects AD8572; Triode Q4, Q5 select NPN9014;

The formation of described signals collecting and puocessing module is seen Fig. 6, and it comprises that signal condition unit, signal gathering unit, processing unit, terminal show and external interface that processing unit comprises recognition circuit and positioning circuit; The signal of photodetector output is connected in series signal condition unit, signal gathering unit and processing unit successively, the signal of collecting unit collection is carried out demultiplexing to processing unit and demodulation obtains original vibration wave signal, then in recognition circuit and positioning circuit, carry out respectively leakage signal identification and the location of leakage point; Processing unit output has video terminal and external interface;

Wherein the conditioning unit circuit as shown in Figure 7, it mainly is comprised of operational amplifier U14, photoelectric diode U15; 1,5,8 ends of U15 are unsettled, 3,4 end ground connection, and 2 ends connect 6 ends after resistance R 39, capacitor C 60 the two parallel connection, and 6 ends connect 3 ends of U14,8 ends of 7 termination U14 through resistance R 43; The 4 end ground connection of U14,5 ends are unsettled, and 6,7 ends meet AD_VINI altogether, and 1 termination AD_OUT mouth, 2 ends be through resistance R 42 ground connection, the two parallel connection of connecting resistance R40 between 1,2 ends, capacitor C 59;

Wherein: operational amplifier U14 selects AD8572; Photoelectric diode U15 selects OPA380AID;

Recognition circuit in the processing unit as shown in figure 14, it mainly is comprised of DSP digital signal processor U1B and peripheral circuit, the NC1-NC15 pin of U1B is unsettled; AVDD, AGND are the analog power input, and AVDD connects the 1.3V power supply by magnetic bead FER1, and 3 capacitor C 22, C23, C24 in parallel carry out decoupling filtering between AVDD and AGND; DAI1, DAI3, DAI4 are connected with DR0PRI, RSCLK0, the RFS0 of positioning circuit DSP digital signal processor U10 respectively and are used for data transfer; DAI9-DAI20 is expansion interface; DPI9, DPI10 connect external interface circuit; Wherein, DSP digital signal processor U1B selects ADSP-21369;

Positioning circuit in the processing unit as shown in Figure 6, it mainly is comprised of DSP digital signal processor U10 and peripheral circuit and interface, the DR0PRI of U10, RSCLK0, RFS0 are connected with DAI1, DAI3, the DAI4 of recognition circuit DSP digital signal processor U1B respectively and are used for receive data, RX, TX, MOSI, MISO, SCK connect the video terminal interface, and TCK, TDO, TDI, TMS, TRST#, EMU# are debugging interface; Wherein DSP digital signal processor U10 selects BF561.

Described sensor construction I type such as Figure 10 are comprised of elastic cylinder 12 and sensor fibre 13; When pipeline is installed and used, elastic cylinder is attached on the natural gas line; Sensor construction II type such as Figure 11, be comprised of sensor fibre 13, fiber management tray 10 and spring sheet 14, production method forms according to the form coiling of Figure 11, sticks on the pipe surface that anticorrosive coat left by plane with adhesive glue during installation, mounting type is realized picking up the pipeline body vibration as shown in Figure 12;

When the pipeline between sensor n and the sensor n+1 occurs to leak, leaking the vibration wave that causes is picked up by sensor n-1, n, n+1 and n+2 respectively through the regular hour along pipe transmmision, receive time difference of leakage signal and the location that can realize more accurately leakage point in conjunction with vibration wave in ducted velocity of propagation according to adjacent a plurality of sensors.

Wherein: in order to overcome the polarization decay of sensor group, the anti-polarization decay method of this gas pipeline leakage detecting sensor group is that the sensor of a Michelson interferometer structure is installed on pipeline body at a certain distance, by the sensor of several Michelson interferometer structures by beam splitter and bundle-mixer and be connected in launching fiber and passback optical fiber between; Two arms of Michelson interferometer are not isometric, each Michelson interferometer uses two faraday rotation mirrors as reflector, angle of swing is 45 degree, and the polarization state that makes catoptrical polarization state variation just in time offset incident light changes, thereby makes the visibility of interferometer remain 1;

In order to overcome the phase fading of sensor group, the anti-phase fading method of this example is: the sensor of a Michelson interferometer structure is installed on pipeline body at a certain distance, by several sensors by beam splitter and bundle-mixer and be connected in launching fiber and the passback optical fiber between; Based on sawtooth wave or fall the laser of saw wave modulator as light source, and the long Michelson interferometer of unequal arm is as sensor; Use band-pass filter that sensor group signal is carried out filtering, the filter center frequency is each sensor carrier signal CF center frequency, and bandwidth is identical with the saw wave modulator signal frequency; Can obtain the carrier signal of this interferometer after the filtering, but the phase fading problem of demodulation erasure signal obtains original leakage acoustic signals;

Wherein suppress for Environmental Random Vibration is disturbed, the intelligent identification Method of the gas pipeline leakage event of employing is: with the temporal signatures P of the normal operation of pipeline and leakage status signals _t, frequency domain character P _fNoise characteristic P with current pipe transmmision signal _nAnd comprehensively analyze in conjunction with waveform recognition, set up and leak confidence coefficient functional model: R=a ₁P _t+ a ₂P _f-a ₃P _n, the vibration wave signal that picks up is leaked assessment judge whether pipeline leaks, according to on-the-spot pipeline characteristics algorithms of different parameter a is set ₁, a ₂, a ₃Regulate the confidence coefficient model.At random accidental vibration and sudden, persistency leakage signal have effectively been distinguished in this identifying method, have improved the accuracy rate of system alarm;

Wherein in order to measure pipe leakage vibration wave velocity of propagation, the measuring vibration wave propagation velocity in case of natural gas pipeline leakage method that adopts, after finishing the natural gas line leakage system, select some known sensor points to cause vibration by knocking the form simulation pipe leakages such as pipeline, accurately provide the distance of two adjacent sensor points of current test point distance according to the quantity of the pipe section that uses in engineering construction and the examination data, with this simulation test point position X substitution: X=L-[v * (t _N+2-t _n)]/2, counter solving: v=2 (L-X)/(t _N+2-t _n), realized measuring vibration wave along the speed of pipe transmmision according to the signal propagation time of known sensor span and mensuration.

This example is through test of many times, can realize the monitoring along any disturbance behavior of pipe transmmision by install to leak the vibration sensing interferometric sensor at tube wall, through realizing signal analysis and processing and intelligent recognition incident of leakage is reported to the police and provided the leakage point position, system sensitivity is high, by the intelligent recognition of leaking has been reduced system's false alarm rate that incident causes largely.

Claims (8)

1. natural gas line leakage method based on Fibre Optical Sensor, it is characterized in that it is that an optical fiber interference type leak sensor is installed at a certain distance on pipeline body, the vibration wave signal that continuous real-time monitoring is propagated along pipeline body, the vibration wave signal that gathers is carried out analysing and processing, comprise type identification and vibration source location, wherein type identification propagates into the time lag of adjacent several optical fiber transducers in conjunction with the location of the velocity of propagation realization of vibration wave on pipeline body to the vibration wave source according to vibration wave simultaneously for whether to belong to leak type by the extraction and analysis of vibration wave feature being differentiated it; Sensor adopts the fibre optic interferometer structure, for optical fiber Michelson interferometer or fiber Mach-Zehnder interferometer as leaking the vibration wave detecting sensor, the light intensity signal of its output can be write as after photoelectric conversion:

V ₀∝1+Vcos(φ _s+φ _n+φ ₀)+V _n (1)

Wherein, V ₀Be the voltage signal of output, V is the visibility of interferometer, V _nThe circuit additional noise, φ _sServe as reasons and leak the phase difference signal that vibration wave causes, be the leakage vibration wave signal that to survey, φ ₀Being the initial phase of interferometer, is a constant, φ _nBeing the low frequency wonder of phase difference, is a Uncertainty, changes with temperature and external environment impact;

Realize leaking the vibration wave signal psi by the demultiplexing technology with modulation of source mode phase 7 couplings _sObtain, and to this signal psi _sThe time lag that arrives corresponding sensor estimates, realized that along the speed v of pipe transmmision to the vibration wave source be determining of leakage point position in conjunction with vibration wave.

2. a kind of natural gas line leakage method based on Fibre Optical Sensor according to claim 1 is characterized in that its employing optical fiber transducer multiplex/demultiplex method; The method of the comprehensive frequency division multiplexing of the method and space division multiplexing, employing produces leak detection light to the method that tunable laser carries out the optical frequency modulation, use Michelson interferometer or Mach-Zehnder interferometer as leak sensor, the laying structure of sensor is that a sensor is installed on the natural gas tube pipeline outer wall at a certain distance, a plurality of sensors consist of a sensor group, and the optical signal of each sensor group uses an optical fiber to pass system host back; Each sensor arm is poor different in the sensor group, the frequency of carrier signal that each leak sensor is produced is all not identical, utilizes thus the frequency division multiplexing principle that the optical multiplexed signal of a plurality of sensor different frequencies of every group is used in the receiving terminal of passing system in the optical fiber back; And employing space division multiplexing mode difference connecting system main frame between a plurality of sensor groups; The optical signal of each the sensor group that receives uses independent photoelectric conversion passage to realize that optical signal is to the conversion of electrical signal, transducing signal after the conversion uses the frequency division mode to realize the demultiplexing of each sensor in the sensor group, and adopt the phase carrier technology to demodulate the original acoustic signals of pipe leakage, pass through again identification and the positioning analysis of leakage signal, but final Obtaining Accurate pipe leakage dot information; The phase carrier demodulation method of described leakage acoustic signals is the interference signal that will receive, and carries out first bandpass filtering, one tunnel output and cos (ω ₀T) carry out lower pass-filter and differential after multiplying each other and process another road and sin (ω ₀T) carrying out lower pass-filter and differential after multiplying each other processes; Behind the output of the differential on last road and rear one tunnel the lower pass-filter output multiplication, subtract each other with rear one tunnel the differential output result with last lower pass-filter output multiplication again, process through integration, high-pass filtering successively afterwards, finally export original leakage vibration wave signal.

3. a kind of natural gas line leakage method based on Fibre Optical Sensor according to claim 1, it is characterized in that adopting in the method anti-polarization decay method, the sensor of a Michelson interferometer structure is installed on pipeline body exactly at a certain distance, by the sensor of several Michelson interferometer structures by beam splitter and bundle-mixer and be connected in launching fiber and passback optical fiber between; Two arms of Michelson interferometer are not isometric, each Michelson interferometer uses two faraday rotation mirrors as reflector, angle of swing is 45 degree, and the polarization state that makes catoptrical polarization state variation just in time offset incident light changes, thereby makes the visibility of interferometer remain 1.

4. a kind of natural gas line leakage method based on Fibre Optical Sensor according to claim 1, it is characterized in that adopting in the method anti-phase fading method, that is: the sensor of a Michelson interferometer or mach-zehnder interferometer configuration is installed at a certain distance on pipeline body, by several sensors by beam splitter and bundle-mixer and be connected in launching fiber and passback optical fiber between; Based on sawtooth wave or fall the laser of saw wave modulator as light source, and the long Michelson interferometer of unequal arm or Mach-Zehnder interferometer are as sensor, in interferometer signal, produce the cosine signal carrier wave of approximate single-frequency, use with carrier signal and with cosine and sinusoidal signal frequently carrier signal is carried out demodulation, obtain original leakage acoustic signals;

The interference signal of sensor group is the linear superposition of each sensor carrier signal in the group, use the bandpass filtering method that the carrier signal of each sensor is separated from the interference signal of sensor group, then use cosine and the sinusoidal signal of corresponding frequencies that carrier signal is carried out demodulation, obtain original leakage vibration wave signal, eliminated signal fadeout and blanking problem that phase fading causes.

5. a kind of natural gas line leakage method based on Fibre Optical Sensor according to claim 1, the multisensor localization method that it is characterized in that its employing gas pipeline leakage event, when leaking generation, leakage excites pipeline to produce vibration wave, vibration wave with speed V along pipe transmmision, wherein two adjacent sensors are spaced apart setting value L, and establishing the time that signal is transmitted to sensor n is t _n, the time that is transmitted to sensor n+1 is t _N+1, the time that signal is transmitted to sensor n-1 is t _N-1, the time that is transmitted to sensor n+2 is t _N+2, have following formula (2) to set up:

$X_1=\frac{1}{2}[L-v\&times;(t_{n+1}-t_n)]$

$X_2=\frac{1}{2}[v\&times;(t_{n-1}-t_{n+1})]$

$X_3=L-\frac{1}{2}[v\&times;(t_{n+2}-t_n)]$

$X_4=\frac{1}{2}[L-v\&times;(t_{n+2}-t_{n-1})]---\left(2\right)$

Unknown parameter (t wherein _N+1-t _n), (t _N-1-t _N+1), (t _N+2-t _n) and (t _N+2-t _N-1) carry out relevant treatment by the signal that the several sensors of correspondence are received and obtain, so just having formed the repeatedly observation to the same unknown quantity of event occurrence positions X, it is poor that a plurality of sensors of combined continuous receive signal time, can locate.

6. a kind of natural gas line leakage method based on Fibre Optical Sensor according to claim 1 is characterized in that it adopts a kind of intelligent identification Method; Temporal signatures P with the normal operation of pipeline and leakage status signals _t, frequency domain character P _fNoise characteristic P with current pipe transmmision signal _nAnd comprehensively analyze in conjunction with waveform recognition, set up and leak confidence coefficient functional model: R=a ₁P _t+ a ₂P _f-a ₃P _n, the vibration wave signal that picks up is leaked assessment judge whether pipeline leaks, according to on-the-spot pipeline characteristics algorithms of different parameter a is set ₁, a ₂, a ₃Regulate the confidence coefficient model.

7. a kind of natural gas line leakage method based on Fibre Optical Sensor according to claim 1, the determining method that it is characterized in that vibration wave propagation velocity in case of natural gas pipeline leakage is: after finishing the natural gas line leakage system, select some known sensor points to cause vibration by knocking the form simulation pipe leakages such as pipeline, accurately provide the distance of two adjacent sensor points of current test point distance according to the quantity of the pipe section that uses in engineering construction and the examination data, with this simulation test point position X substitution: X=L-[v * (t _N+2-t _n)]/2, counter solving: v=2 (L-X)/(t _N+2-t _n), realize measuring vibration wave along the speed of pipe transmmision according to the signal propagation time of known sensor span and mensuration.

8. a kind of natural gas line leakage method based on Fibre Optical Sensor according to claim 1, the determining method that it is characterized in that the natural gas line absolute growth is: the pipeline that at first excavates position to be measured buries soil, knock the vibration of pipeline simulation pipe leakage at this point, measure the position of analog site, X=[L-v * (t according to known simulated leakage vibration wave along the signal propagation time of the speed of pipe transmmision and mensuration _N+1-t _n)]/2, thereby realized the measurement of pipeline absolute distance.

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