CN102997050A - System for resisting phase fading of natural gas pipe leakage optical fiber detecting system - Google Patents
System for resisting phase fading of natural gas pipe leakage optical fiber detecting system Download PDFInfo
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Abstract
The invention discloses a system for resisting phase fading of a natural gas pipe leakage optical fiber detecting system and relates to the technical field of mechanical vibration measurement, impact measurement and a pipe system. The system comprises a light source, an optical path system and a circuit; an optical fiber sensor is arranged on a pipe body every certain interval; adjacent optical fiber sensors form an optical fiber sensor group; each optical fiber sensor group is connected with the light source through a transmitting optical fiber; each optical fiber sensor group is connected with a photoelectric detector through a returning optical fiber; the output of the photoelectric detector is connected with a signal acquiring and processing module which comprises a leakage signal identifying circuit and an event positioning circuit; and the output of the signal acquiring and processing module is connected with a microcomputer through an external interface. The problems of unstable sensitivity and unstable signal to noise ratio caused by phase fading can be effectively solved, and a leakage signal is reliably detected.
Description
Technical field
The present invention is a kind of anti-phase fading system of gas pipeline leakage fiber optic detection system.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 approximately 8 meters of one segment lengths, 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, it is to have installing optical fibres sensor on the pipeline body of certain intervals, 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 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 is determined the position at vibration wave source place in conjunction with the velocity of propagation of vibration wave on pipeline body, the light intensity signal of sensor output is realized position definite of leakage point after photoelectric conversion.
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 and a kind ofly can effectively eliminate sensitivity and signal to noise ratio wild effect that phase fading causes, realize the anti-phase fading system to the gas pipeline leakage fiber optic detection system of the reliable detection of leakage signal.
The purpose of this invention is to provide the quasi-distributed leakage vibration monitor system of a kind of high sensitivity based on Fibre Optical Sensor, so that can the leakages such as little leakage, seepage occur during the primary stage at pipeline, can in time be monitored and be produced warning, so that the related maintenance personnel takes counter-measure, avoid causing larger security incident.
Thereby the natural gas line leakage system with the sensitivity of high leakage vibrating sensing has realized the raising of interferometer to the induction sensitivity of oscillating signal by the length and the space length that increase interferometer two pickup arms, at the intelligent identification technology that has adopted leakage signal aspect the inhibition that Environmental Random Vibration is disturbed, random accidental vibration and sudden, persistency leakage signal have effectively been distinguished, and in conjunction with the leakage signal time delay that adjacent a plurality of sensors obtain simultaneously, the location of having realized more accurately leakage point.
Optical fiber in the common communications optical cable of utilization and oil and gas pipes laying in one ditch is as emission and passback optical fiber, pipeline is revealed optical fiber transducer to be connected between emission and the passback optical fiber by Optical multiplexing technology is parallel with one another, form light circuit, pipeline is revealed optical fiber transducer and is installed on the pipeline, and formation can be monitored the optical fiber sensing system that pipeline is revealed sound wave.Utilize light source that each pipeline is revealed optical fiber transducer scanning, reveal photoelectric conversion signal demodulation, the extraction of distribution situation to gathering of optical fiber transducer according to pipeline, the vibration information of realizing each pipeline leakage optical fiber transducer obtains, the detection analysis conduit is revealed the optical fiber transducer signal and has been judged whether that pipeline leakage event occurs, and reveals optical fiber transducer according to adjacent pipeline and detects the time delay of arrival realization of signal to the location of leak point.
The anti-phase fading method of 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 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.
Adopt optical fiber Michelson interferometer or Mach-Zehnder interferometer as leaking the sonic detection 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
sBe the phase difference signal that is caused by underwater sound ripple, be the leakage acoustic signals 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.
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, adopt the phase carrier technology to detect the leakage acoustic signals.Specific as follows:
When making Michelson interferometer or Mach-Zehnder 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 at least the twice of leaking the sound wave frequency bandwidth, be applied to the adjustable laser of optical frequency, the laser that laser output optical frequency changes synchronously according to the saw wave modulator 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 the phase fading problem of demodulation erasure signal as follows obtains original leakage acoustic signals.
The demodulation principle of sensor carrier signal is seen Fig. 6, interference signal output tape splicing pass filter, bandpass filtering export one the tunnel with cos (ω
0T) connect the first lower pass-filter after multiplying each other, this lower pass-filter output connects the first differentiator, another road and sin (ω
0T) join, connect the second lower pass-filter after multiplying each other, 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 the anti-phase fading system of this gas pipeline leakage detecting sensor group is seen Fig. 1, and it comprises light source, light path system and circuit 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 recognition circuit and state event location circuit, and signals collecting and puocessing module output connect microcomputer by external interface.
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.
Described optical fiber transducer adopts optical fiber Michelson interferometer or Mach-Zehnder interferometer, and interferometer two arms are not isometric, and two arm length difference are Δ L;
Described signals collecting and puocessing module comprise that signal condition unit, signal gathering unit, processing unit, terminal show and external interface; Photodetector output is connected in series signal condition unit, signal gathering unit and processing unit successively;
Described light source adopts the adjustable laser of optical frequency, uses the modulation signal module to produce required sawtooth wave or the signal of falling the saw wave modulator, is applied to the continuous laser that exportable optical frequency changes according to modulation signal waveform rule on the laser;
Light source consists of (seeing Fig. 4) 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 the sawtooth wave/selection of falling sawtooth wave input;
Use the modulation signal module to produce required sawtooth wave or the signal of falling the saw wave modulator, by the output of the D/A in the modulation signal generation module, be applied to the continuous laser that exportable optical frequency changes according to sawtooth wave or the rule of falling the sawtooth wave on the laser;
Wherein the modulation of source circuit as shown in Figure 5, 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;
Described light path system is a Michelson interferometer or Mach-Zehnder interferometer to be installed at a certain distance as the pipe leakage sonic sensor on pipeline, simultaneously the laser that sends of laser by with pipeline laying in one ditch optical cable in an optical fibre transmission (being called launching fiber), when laser arrives near each sensor, be divided into two bundles by beam splitter, beam of laser is injected the sensor input end, another Shu Jiguang passes to next sensor by launching fiber, by that analogy; Every 2-10 adjacent sensor is divided into one group, and the interference signal of each sensor transfers back to the equipment receiving terminal by combiner device access passback optical fiber in the group; 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, and the supplying with optical fiber of curtailment is to prevent that signal cross-talk occurs between the sensor;
Each sensor group is used a passback optical fiber, and whole like this sensing light path needs a launching fiber, and the passback number of fibers is identical with sensor group quantity;
Because the arm length difference of the sensor in every group is different, launching fiber between the adjacent sensors, passback fiber lengths are all greater than 1/2 of laser coherent length, the frequency of each sensor output interference signal is different in can the assurance group, does not interfere between the group inner sensor;
Described signals collecting and puocessing module comprise that signal condition unit, signal gathering unit, processing unit, terminal show and external interface; The signal of photodetector output is connected in series signal condition unit, signal gathering unit and processing unit successively, and processing unit output has terminal to show and external interface; Wherein signal processing unit is mainly realized signal demodulation, the functions such as Identification of events and location.
Photoelectric conversion module is converted to electrical signal with the interference light signal of each sensor group, the corresponding photoelectric conversion passage independently of each sensor group;
The interference signal that signals collecting and puocessing module gather each sensor group is digital signal, because each interferometer signal carrier frequency is different in the group, and do not interfere between each interferometer, namely do not crosstalk between each interferometer signal, the carrier signal of each sensor is thoroughly separated in can will organizing by the method for bandpass filtering;
After bandpass filtering obtains the carrier signal of each sensor, by the phase generated carrier modulation and demodulation technology, demodulate original leakage acoustic signals;
Analyze the delay inequality of the leakage acoustic signals that adjacent two sensors detect, in conjunction with sound wave transmission speed in pipeline, the location that can realize leakage point;
The formation of described signals collecting and puocessing module is seen Fig. 8, and it comprises signal condition unit, signal gathering unit, processing unit, video terminal and external interface; Wherein the conditioning unit circuit as shown in Figure 9, 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 the demodulation principle block diagram of sensor carrier signal is seen Fig. 6, interference signal output tape splicing pass filter, bandpass filtering export one the tunnel with cos (ω
0T) joining 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) join, connect the second lower pass-filter after multiplying each other, 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 common communications optical fibre in optical cable of utilization and oil and gas pipes laying in one ditch is respectively as emission and passback optical fiber, the pipe leakage optical fiber transducer is connected between the transmitting-receiving transmission fiber by Optical multiplexing technology is parallel with one another, form light circuit, it is along the line that the pipe leakage optical fiber transducer evenly is laid in pipeline, and formation can be monitored the optical fiber sensing system of pipe leakage vibration.Utilize light source to each pipe leakage optical fiber transducer scanning, based on the faraday rotation mirror method, realize the anti-polarization decay of the interference signal of each sensor in sensor group and the group, improve and stablized visibility and the signal to noise ratio of sensor and sensor group interference signal, use photoelectric conversion module that the interference light signal of each sensor group is converted to electrical signal, the corresponding photoelectric conversion passage independently of each sensor group, the interference signal that is gathered each sensor group by signals collecting and puocessing module is digital signal, and the carrier signal of each sensor is thoroughly separated in can will organizing by the method for bandpass filtering, by the phase generated carrier modulation and demodulation technology, demodulate original leakage vibration wave signal; Analyze the delay inequality of the leakage vibration wave signal that adjacent several sensor detects, in conjunction with vibration wave transmission speed in pipeline, the location that can realize leakage point.Thereby use the multiplexing quantity that the multiplexing modulation-demodulation technique of multisensor has improved sensor group inner sensor greatly, reduced the usage quantity of optical fiber, detect in keeping system under the prerequisite of effect, reduced system complex degree and cost.
The present invention is 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, can effectively eliminate sensitivity and the unsettled problem of signal to noise ratio that phase fading causes, realize the reliable detection to leakage signal.
Description of drawings
Fig. 1 monitoring system of fiber optical sensing natural gas pipeline
The sensing light path connection diagram that Fig. 2 gas pipeline leakage detects
Fig. 3 Michelson interferometer structural representation
The modulation principle figure of Fig. 4 optical frequency adjustable type light source
Fig. 5 modulation of source circuit diagram
Fig. 6 leaks vibration wave demodulation principle block diagram
Fig. 7 light path adapter structure and transmission index path
Fig. 8 signals collecting and puocessing module structural drawing
Signal condition element circuit figure in Fig. 9 signals collecting and the puocessing module
Wherein 1,1-1 ..., 1-n-beam splitter 2,2-1 ..., 2-n-optical fiber transducer 3,3-1 ..., 3-n- combiner device 4,5,6,7,8,9-time delay optical fiber
Embodiment
Embodiment: the formation of this example as depicted in figs. 1 and 2, it comprises light source, light path system and circuit part; 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, 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 described signals collecting and puocessing module comprise that signal condition unit, signal gathering unit, processing unit, terminal show and external interface; The signal of photodetector output is connected in series signal condition unit, signal gathering unit and processing unit successively, and processing unit output has terminal to show and external interface.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.
Sensor adopts the interferometer of Michelson-structure, and it is that 45 faraday rotation mirrors of spending are as reflector that each interferometer uses two angle of swing.The present embodiment has been made 10 Michelson interferometer sensors, is divided into two groups, every group of 5 sensors, and arm length difference is respectively 5m, 7.5m, 10m, 12.5m, 15m;
With two sensors according to Fig. 2 and be connected in launching fiber and passback optical fiber between, two sensor groups share launching fibers, each independently uses one to return optical fiber;
Inject the laser that optical frequency changes with sawtooth wave from launching fiber, with photoelectric conversion module receiving sensor group interference signal, use band-pass filter to interference signal filtering from passback optical fiber, obtain the carrier signal of each sensor.By test as can be known, sensor group and filtered sensor carrier signal amplitude stabilization are constant, and the sensor signal after the demodulation is stable, and signal to noise ratio is high and keep stable.
Described light source is a kind of special light source system of modulation /demodulation, and laser and the dedicated modulation signal generating module adjustable by optical frequency consist of (seeing Fig. 4); Modulation signal generation module 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 (D/A) mode, the modulated-analog signal of output is connected on the laser, wherein select 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; Sawtooth wave or the requirement of falling the sawtooth signal amplitude of the output of modulation signal generation module are to the maximum ± 5V, and frequency is 200KHz to the maximum; 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 5, 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 L 3 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 formation of described signals collecting and puocessing module is seen Fig. 8, and it comprises signal condition unit, signal gathering unit, processing unit, video terminal and external interface; Wherein the conditioning unit circuit as shown in Figure 9, 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, and photoelectric diode U15 selects OPA380AID.
This routine light source adopts semiconductor laser that optical frequency can modulate as light source, add the sawtooth signal that modulation signal is frequency 10kHz, amplitude ± 1.4V, be added on the laser; The sensing light path use the sensor of two groups of Michelson interferometer structures and be connected in launching fiber and passback optical fiber between, the interference signal frequency spectrum of sensor group output mainly is made of 40kHz, 60kHz, 80kHz, 100kHz, five spectral lines of 120kHz; The band-pass filter that uses frequency centered by above-mentioned five frequencies, bandwidth to be 10kHz carries out filtering to sensor group signal, obtains the carrier signal of each sensor, and corresponding main frequency is respectively 40kHz, 60kHz, 80kHz, 100kHz, 120kHz; Each carrier signal used respectively with frequently cosine and sinusoidal signal carries out demodulation, obtain each sensor corresponding original analog leak acoustic signals; PZT phase-modulator of an arm series connection at each sensor, the amplitude of applying is that 0.5V, frequency are that the cosine signal of 2kHz is as the simulated leakage acoustic signals, the signal that demodulates by said method is the cosine signal of 2kHz, by long-time monitoring, the signal amplitude of each sensor demodulation is stable, illustrate that anti-phase fading method of the present invention is effective, can realize the stable detection of leakage signal.
This example is through test of many times, proved that the anti-phase fading technology for sensor group and group inner sensor is effective among the present invention, greatly improve sensitivity and the stability of system's testing signal, thereby also improved the multiplexing quantity of sensor group inner sensor, reduced reuse cost.
Claims (6)
1. the anti-phase fading system of a gas pipeline leakage detecting sensor group is characterized in that it comprises light source, light path system and circuit 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 recognition circuit and state event location circuit, and signals collecting and puocessing module output connect microcomputer by external interface;
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.
2. the anti-phase fading system of a kind of gas pipeline leakage detecting sensor group according to claim 1 is characterized in that described light source is made of optical frequency adjustable laser and dedicated modulation signal generating module; Modulation signal generation module connects the laser modulation signal input part by D/A output; Modulation signal generation module output signal has frequency adjustment, amplitude adjusted and the sawtooth wave/selection of falling sawtooth wave input;
Use the modulation signal module to produce required sawtooth wave or the signal of falling the saw wave modulator, be applied on the laser by the output of the D/A in the modulation signal generation module, the continuous laser that the output optical frequency changes according to sawtooth wave or the rule of falling the sawtooth wave.
3. the anti-phase fading system of a kind of gas pipeline leakage detecting sensor group according to claim 2 is characterized in that the modulation of source main circuit of modulation signal generation module will be 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.
4. the anti-phase fading system of a kind of gas pipeline leakage detecting sensor group according to claim 1, it is characterized in that described light path system is the interferometer of a Michelson-or Mach-Zehnder structure to be installed at a certain distance as the pipe leakage sonic sensor on pipeline, use simultaneously with pipeline laying in one ditch optical cable in the laser that the optical fiber transmission laser that is called launching fiber sends, when laser arrives near each sensor, be divided into two bundles by beam splitter, beam of laser is injected the sensor input end, another Shu Jiguang passes to next sensor by launching fiber, by that analogy; A plurality of adjacent sensors are divided into one group on the pipeline, and the interference signal of each sensor transfers back to the equipment receiving terminal by combiner device access passback optical fiber in the group; 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;
Each sensor group is used a passback optical fiber, and the passback number of fibers is identical with sensor group quantity.
5. the anti-phase fading system of a kind of gas pipeline leakage detecting sensor group according to claim 1 is characterized in that described signals collecting and puocessing module comprise that signal condition unit, signal gathering unit, processing unit, terminal show and external interface; Photodetector output is connected in series signal condition unit, signal gathering unit and processing unit successively, and processing unit output has terminal to show and external interface.
6. the anti-phase fading system of a kind of gas pipeline leakage detecting sensor group according to claim 5 is characterized in that the main circuit of described signal condition unit will be 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.
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