CN101255951B - Method for improving oil gas pipe leakage and performance of instruction testing distributed optical fibre sensor - Google Patents
Method for improving oil gas pipe leakage and performance of instruction testing distributed optical fibre sensor Download PDFInfo
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- CN101255951B CN101255951B CN2008100492621A CN200810049262A CN101255951B CN 101255951 B CN101255951 B CN 101255951B CN 2008100492621 A CN2008100492621 A CN 2008100492621A CN 200810049262 A CN200810049262 A CN 200810049262A CN 101255951 B CN101255951 B CN 101255951B
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Abstract
The invention relates to a method for improving performance of a distributed optical fibre sensor for detecting oil gas conduit leakage and inbreak by using Golay code. Detection signals in the sensing optical fibre are continuous optical pulse sequences modulated by Golay code and complement code thereof. The optical pulse sequences are sampling signals of sensing optical fiber transportation consumption. By reducing pulse width of optical pulse sequences, not only sampling frequency of sensing fiber transportation consumption is increased to analyze characters of new transportation consumption in the sensing optical fibre caused by conduit leakage and third party inbreak case in a larger frequency spectrum range, but also spatial resolution of synthesized backscattering optical signals is increased by analyzing to increase positioning accuracy of the new consumption. In another aspect, by adding optical pulse amount in sequences, not only sampling amount of transportation consumption is increased to facilitate characters analysis for new transportation consumption signals in the sensing optical fibre, but also intensity of synthesized backscattering optical signals and signal-to-noise ratio are increased, and the distance of conduit is increased.
Description
Technical field
The invention belongs to input and analysis technical field, relate to a kind of online test method, particularly a kind of method of utilizing the Golay sign indicating number to improve the distributed fiberoptic sensor performance of oil and gas pipeline leakage and the detection of third party's intrusion event.
Background technique
Line transportation is a kind of economy means of transportation easily, in the conveying of oil and natural gas, has unique advantage, and outstanding behaviours is safe, convenient and efficient etc.Long oil and gas pipeline has become the aortic important component part of China's energy, and strategic position is very important.The characteristics of long oil and gas pipeline are point more than long lines, and are mostly buried pipe.Because Environmental Conditions is abominable, along with active time increases, factors such as the sedimentation of burn into landform, weight, mechanical execution and artificial destruction all possibly make pipeline damage occur, even leak.Leak and not only can cause huge property loss and serious environmental pollution, in addition can initiation fire, blast, the safety that threatens people's life and property.To pipe leakage and third party's intrusion events such as weight, landform sedimentation, mechanical execution and artificial destruction that possibly cause pipeline external force damage judge rapidly and accurately the location, in time find to leak and forecast is leaked hidden danger and just seemed very important.
At present, the method for pipeline leakage testing is a lot, divides direct leak detecting and indirect leak detecting.Directly leak detecting is to utilize prober directly to detect the outer leakage of pipeline to judge leakage, comprises leak detection cables method, conductive high polymer leak detecting, sensing optic cable method, infra-red method and GPR method etc.Leak detecting is to estimate to leak through the Operational Limits (like pressure, flow, temperature etc.) of monitoring pipeline indirectly, comprises the machine method of creeping in mass balance method, negative pressure wave method, pressure gradient method, the pipe, statistics leak detecting, stress wave, acoustic method and real-time model method etc.Wherein the sensing optic cable method is a kind of detecting method based on distributed fiberoptic sensor, has become the focus of oil-gas pipeline safety detection technique research.
Distributed fiberoptic sensor be follow the development of Fibre Optical Communication Technology and develop rapidly a kind of be that carrier, optical fiber are medium with light; The novel sensor of perception and transmission outer signals, it has the ability of obtaining simultaneously in the sensor fibre zone in time with the measured distributed intelligence of spatial variations.Lay a sensing optic cable along oil and gas pipes; Pipe leakage and possibly cause that third party's intrusion event of pipeline external force damage produces active force near the sensing optic cable of laying the pipeline, transverse force wherein and longitudinal force can make the sensor fibre generation transmission loss in the sensing optic cable through little curved or grating effect; In addition, the clad material that sensing optic cable can adopt natural rubber etc. to have the swelling characteristic, oil transport pipeline take place to leak or during seepage (water clock); The clad material of sensing optic cable is met oil volume and is expanded; The masterpiece that produces that expands is used for sensor fibre, and sensor fibre is bent, and loss occurs.Use OTDR can the external event that cause loss be positioned.A kind of system architecture of the distributed fiberoptic sensor based on OTDR oil and gas pipeline leakage and intrusion detection is as shown in Figure 1.
As shown in Figure 1; The light pulse that laser pulse generator [101] produces is injected into sensor fibre [2] and propagation forward sensor fibre [2] through isolator [102] and Coupler [103] from an end (being called input end); Export and be coupled to optical power detector [401] at the other end (being called output terminal) of sensor fibre [2] and convert electrical signal to; Then after amplification/wave filter [402], mould/number conversion and DSP digital signal processor [403] cell processing; The result gives computer data analytical system [5], is called Output optical power testing module [4].Simultaneously, light pulse is along sensor fibre [2] forward in the propagation process, because of Rayleigh scattering and Fresnel reflectino constantly produce back-scattering light.Back-scattering light is along sensor fibre [2] backpropagation and turn back to input end; Arrive optical power detector [301] through Coupler [103]; Convert electrical signal to; After amplification/wave filter [302], mould/number conversion and DSP digital signal processor [303] cell processing, the result also gives computer data analytical system [5], is called back-scattering light testing module [3] again.Computer [5] is analyzed the output data of optical fiber Output optical power testing module [4] and is merged; Acquisition is along the variation of sensor fibre [2] path upward pressure and oscillating signal; Judge whether have pipe leakage or intrusion event to take place according to its spectrum signature, and utilize back-scattering light testing module [3] to position.Therefore, Output optical power testing module [4] can obtain sensor fibre [2] and go up the spectrum signature that loss changes, failure judgement type; Back-scattering light testing module [3] is used for sensor fibre [2] and goes up the static and dynamic loss measurement of each point, realizes fault localization.
In the distributed fiberoptic sensor system; The light pulse that laser pulse generator [101] produces has two effects: the one, constantly produce back-scattering light in the process that light pulse is propagated forward in sensor fibre [2]; Through measurement, obtain the space distribution that sensor fibre [2] is gone up newly-increased loss at input end to back-scattering light; The 2nd, in the process that light pulse is propagated forward in sensor fibre [2]; The external disturbance that pipe leakage and third party's intrusion event produce makes the light pulse of transmission in the sensor fibre [2] loss occur; The luminous power of output changes, so photoderm can be used as the sampling pulse of sensor fibre [2] transmission loss.
Advantage based on the distributed fiberoptic sensor of OTDR oil and gas pipeline leakage and intrusion detection; The one, light-pulse generator [101] and back-scattering light signal detection module [3] are all at the same end of sensor fibre [2]; Can realize the one-end fault location; When incidents such as blast, excavation cause the sensing optic cable fracture, still can event of failure be positioned; The 2nd, because the back-scattering light that light pulse produces at the last diverse location of sensor fibre [2] turns back to the asynchronism(-nization) of input end, can not disturb each other, therefore can locate simultaneously a plurality of fault points.Shortcoming be the backscattering optical signal that produces when in sensor fibre [2], propagating of light pulse very a little less than; More much lower than optical pulse energy; Directly influenced the signal to noise ratio of back-scattering light, limited the detection distance, and also there is certain restriction in the minimum interval that has between the photoderm of sampling function.
In order to improve the signal to noise ratio of back-scattering light, need to improve the energy of light pulse.A kind of method is to improve the power of laser pulse generator [101], and another kind of method is the time width that increases light pulse.In case the light pulse peak power has reached maximum value, and the sensitivity of receiver also is best, is merely able to use the method that increases light impulse length to improve the signal to noise ratio of back-scattering light so.But, increase the spatial resolution decline that pulse width can cause the backscattering optical signal.Therefore between backscattering OSNR and loss spatial resolution, have contradiction, light pulse is narrow more, and the spatial resolution of loss location is high more, but the signal to noise ratio of backscattering optical signal is poor more.
The another kind of method that improves the backscattering OSNR is to launch a plurality of pulses at interval according to certain hour, gathers the backscattering optical signal of each pulse respectively, then averaged.Here there is a restriction; Promptly have only the back-scattering light of previous light pulse all to turn back to after the input end; Could send next pulse; Otherwise previous pulse than the back-scattering light of distant positions and a back pulse in the back-scattering light mutual superposition of closer locations, cause interference each other.The minimum interval T that is input between the middle light pulse of sensor fibre [2] can pass through formula (1) acquisition:
Wherein Z is the length of optical fiber [2]; C is an optical signal velocity of propagation in a vacuum; n
1It is fiber core refractive index; Constant 2 expression light pulse propagations turn back to the time of input end (promptly back and forth) again to sensor fibre [2] output terminal and at the back-scattering light that output terminal produces.Therefore, sensor fibre [2] is long more, and the time lag T between the pulse is big more, and the frequency that pulse repeats is more little.
When light pulse is propagated in sensor fibre [2], the disturbance modulation that loss is produced by external event.The light pulse that repeats with time T of in sensor fibre [2], propagating also is the sampling pulse of sensor fibre [2] transmission loss.Sensor fibre [2] is long more, and interpulse time lag T is big more, and the frequency of sampling pulse is more little.According to sampling thheorem, sample frequency is 2 times that sensor fibre [2] is gone up the loss peak frequency at least.Therefore; External event causes the peak frequency of the transmission loss in the sensor fibre [2] to define the minimum sample frequency of transmission loss and the maximum time interval T of sampling pulse, thereby has limited the detection distance based on the distributed fiberoptic sensor of OTDR oil and gas pipeline leakage and intrusion detection.
Summary of the invention
To the deficiency that above-mentioned existing technology exists, the objective of the invention is to propose the method that a kind of Golay of utilization sign indicating number overcomes above-mentioned restriction and improves the distributed fiberoptic sensor performance of oil and gas pipeline leakage and intrusion detection.
To achieve these goals, the technological scheme of the present invention's employing is:
At the input end of sensor fibre, what laser pulse generator was exported is that amplitude is by the light pulse sequence of Golay sign indicating number with the modulation of their radix-minus-one complements.The disturbance modulation that is produced by pipe leakage and intrusion event in the process that light pulse sequence is propagated forward along sensor fibre.At the output terminal of sensor fibre, the Output optical power testing module is gathered the light pulse sequence of sensor fibre output, and send computer to handle; Computer carries out amplitude transformation to the pulse sequence signal of Output optical power testing module output, eliminates the modulation of Golay sign indicating number and their radix-minus-one complements, makes the amplitude of the pulse sequence signal of exporting after the conversion only relevant with the disturbance that pipe leakage and intrusion event produce.On the other hand, the back-scattering light that light pulse sequence produces in the propagation process forward along sensor fibre after back-scattering light testing module collecting treatment, send computer to handle along the sensor fibre backpropagation to input end.Computer utilizes the light pulse sequence of Golay sign indicating number and the modulation of their radix-minus-one complements along the backscattering optical signal that produces in the sensor fibre propagation process, synthetic new backscattering optical signal.Compare with the backscattering optical signal of monopulse; The signal of synthetic backscattering optical signal is strong; And both spatial resolution are identical; Thereby the distributed fiberoptic sensor that makes pipe leakage and intrusion detection can improve the signal to noise ratio of backscattering optical signal through the length that increases light pulse sequence, thereby increase the monitoring length of pipeline under the constant condition of incident Location accuracy.
A kind of method of utilizing the Golay sign indicating number to improve the distributed fiberoptic sensor performance of oil and gas pipeline leakage and intrusion detection specifically may further comprise the steps:
1) near oil and gas pipes, with optical cable of the parallel laying of oil and gas pipes, utilize sensor fibre as sensor, oil and gas pipeline leakage and third party's intrusion event are monitored in real time;
2), a back-scattering light testing module and optical fiber Output optical power testing module are set respectively at the two ends of sensor fibre;
Computer is used Golay sign indicating number and their radix-minus-one complement modulated laser pulse oscillator respectively, and what make laser pulse generator output is that amplitude is by the continuous light pulse sequence of Golay sign indicating number with the modulation of their radix-minus-one complements;
The light pulse sequence of laser pulse generator output is through isolator and Coupler is coupled into sensor fibre and propagation forward in sensor fibre; At the output terminal of sensor fibre, the Output optical power testing module is gathered the light pulse sequence of sensor fibre output, and send Computer Processing; Computer carries out amplitude transformation to the pulse sequence signal of Output optical power testing module output, eliminates the modulation of Golay sign indicating number and their radix-minus-one complements; Computer is accomplished the measurement of sensor fibre overall diameter total losses dynamic change and the judgement of fault type through the analysis to the optical fiber Output optical power signal after the conversion;
At the input end of sensor fibre, the backscattering optical signal that the light pulse sequence that the back-scattering light testing module is gathered the modulation of Golay sign indicating number and their radix-minus-one complements respectively produces in the propagation process forward along sensor fibre, and send Computer Processing; Computer utilizes above-mentioned backscattering optical signal to synthesize new backscattering optical signal; Synthetic backscattering optical signal aspect spatial resolution with sequence in backscattering optical signal identical of single light pulse; Aspect signal intensity; Strong than individual pulse, and be directly proportional with the number of light pulse in the sequence; Computer is accomplished the static state of each point on the sensor fibre and the measurement and the location of dynamic loss through the analysis to the new backscattering optical signal that synthesizes;
3) computer is through analysis and fusion to lossy data on the sensor fibre, and the pressure around the acquisition oil and gas pipes and the characteristic of oscillating signal are judged and the location oil and gas pipes is revealed and the generation of third party's intrusion event.
Some other characteristics of the present invention are:
Described laser pulse generator or laser diode, or laser triode, the width of the light pulse of its output, energy are controlled.
What described laser pulse generator was exported is continuous light pulse sequence, and the width of pulse is identical in the sequence, and amplitude is by Golay sign indicating number and their radix-minus-one complement modulation.
The length of described Golay sign indicating number and their radix-minus-one complements all is power powers of 2.
Between the light pulse sequence of described Golay sign indicating number and their radix-minus-one complements modulation is to be input at a certain time interval in the sensor fibre, the difference of the time when its minimum interval equals that first light pulse is input to sensor fibre in time and the sequence when the back-scattering light that the sensor fibre output terminal produces turns back to the sensor fibre input end of last light pulse in the sequence.
The length of the described light pulse sequence of in sensor fibre, propagating is identical with the length of Golay sign indicating number and their radix-minus-one complements, also is 2 power power.
Described Golay sign indicating number and their radix-minus-one complement are pseudo-random signals, therefore at the output terminal of sensor fibre, do not use wave filter, but eliminate the modulation of Golay sign indicating number or their radix-minus-one complements through the method for conversion.
Sensor fibre in the described sensing optic cable or SMF Single Mode Fiber, or multi-mould optical fibre, its transmission loss is responsive to deformation, pressure and oscillating signal.
Described back-scattering light testing module comprises optical power detector, amplification and low-pass filter, mould/number conversion and DSP digital signal processor unit.
Described Output optical power testing module comprises optical power detector, amplification and low-pass filter, mould/number conversion and DSP digital signal processor unit.
Described back-scattering light testing module and Output optical power testing module can be integrated in the system, also can make separation, links to each other through data communication network.
Described back-scattering light testing module and Output optical power testing module both can be worked simultaneously, also can work alone.The back-scattering light testing module is mainly accomplished the static state of each point on the sensor fibre and the measurement and the locating function of dynamic loss; The Output optical power testing module is mainly accomplished the measurement of total losses dynamic change on the sensor fibre and the decision-making function of fault type.
Described back-scattering light testing module can be an OTDR, the network interface and the computer communication that utilize communication interface (like GPIB, RS-232) that OTDR provides or OTDR to provide; Also can be that the OTDR card is directly installed in the computer.The working state of OTDR receives computer control.
The method of the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage of the present invention and intrusion detection has following advantage:
1) in the method for the present invention, the detected signal of sensor fibre is that these light pulse sequences are sampled signals of sensor fibre transmission loss with the continuous light pulse sequence of Golay sign indicating number with the modulation of their radix-minus-one complements.Because the cycle (width) of light pulse has no restriction in the sequence, can get arbitrarily small value in theory, therefore can reduce the width of light pulse in the sequence.On the one hand; Through reducing the width of light pulse in the sequence; Can increase the sample frequency of sensor fibre loss, thereby make computer can leak the characteristic of the loss that on sensor fibre, produces with third party's intrusion event that possibly cause pipe damage at bigger spectral range analysis conduit; On the other hand; The synthetic backscattering optical signal of computer aspect spatial resolution with sequence in backscattering optical signal identical of single light pulse; Therefore through reducing the width of pulse in the light pulse sequence; Also can improve the spatial resolution of synthetic backscattering optical signal simultaneously, thereby improve the Location accuracy of newly-increased loss on the sensor fibre.
2) in the method for the present invention, the detected signal of sensor fibre is with the continuous light pulse sequence of Golay sign indicating number with the modulation of their radix-minus-one complements.On the one hand,, can increase the sampling number of sensor fibre loss, increase the characteristic of transmission loss signal in the sensor fibre that helps analysis conduit leakage and third party's intrusion event to cause newly through increasing the number of pulse in the sequence; On the other hand; Because the signal intensity of synthetic backscattering optical signal is directly proportional with the number of light pulse in the sequence; Through increasing the number of pulse in the sequence, can improve the signal to noise ratio of synthetic backscattering optical signal, thereby increase the distance that distributed fiberoptic sensor detects pipeline.
Therefore the method for the invention can either increase the distance that distributed fiberoptic sensor detects pipeline through the intensity and raising signal to noise ratio that strengthens the backscattering optical signal; Again can be through increasing the sample frequency of sensor fibre loss; Leak the characteristic of the loss that on sensor fibre, produces with third party's intrusion event that possibly cause pipe damage at bigger spectral range analysis conduit, thereby improve overall performance based on the distributed fiberoptic sensor of OTDR oil and gas pipeline leakage and intrusion detection.
Description of drawings
Fig. 1 is the system architecture diagram of the distributed fiberoptic sensor of the embodiment of the invention.
Fig. 2 is one group of 64 Golay sign indicating number A of the embodiment of the invention and the waveform of B.
Fig. 3 be the embodiment of the invention 64 Golay sign indicating number A and B self correlation function and their self correlation functions and waveform.
Figure 4 is an embodiment of the present invention, 64-bit Golay code A and B, and their inverted
and
modulated laser pulse generator [101] output optical pulse train signal waveform.
Fig. 5 is the waveform before and after the optical pulse sequence signal amplitude transformation of sensor fibre [2] output of the embodiment of the invention.
Figure 6 is the embodiment of the present invention using the Golay code A and B, and their inverted
and
modulated optical pulse train signal synthesis backscattered light backscattered light signals a new process.
Embodiment
As shown in Figure 1, back-scattering light testing module and optical fiber Output optical power testing module that distributed fiberoptic sensor of the present invention comprises sensor fibre and lays respectively at the sensor fibre two ends.The Golay sign indicating number that utilizes that the present invention proposes improves the method for the distributed fiberoptic sensor performance of pipe leakage and intrusion event detection, may further comprise the steps:
1) computer 5 is used Golay sign indicating number and their radix-minus-one complement modulated laser pulse oscillator 101 respectively, and what make laser pulse generator 101 outputs is that amplitude is by the light pulse sequence of Golay sign indicating number with the modulation of their radix-minus-one complements.
2) light pulse sequence of laser pulse generator 101 outputs is coupled into sensor fibre 2; In the process that light pulse sequence is propagated forward along sensor fibre 2, the disturbance modulation that its amplitude is produced by pipe leakage and intrusion event; At the output terminal of sensor fibre 2, optical pulse sequence signal is gathered by optical fiber Output optical power testing module 4 and is sent computer 5 to handle; Computer 5 at first carries out amplitude transformation to optical pulse sequence signal, eliminates the modulation of Golay sign indicating number and their radix-minus-one complements, and the interference of the external event that the variation of output signal amplitude only receives with sensor fibre 2 after the conversion is relevant; Computer 5 is through frequency analysis then, the characteristic of newly-increased transmission loss signal variation when obtaining sensor fibre 2 and receiving pipe leakage and disturb with third party's intrusion event.
Because the sampled signal of transmission loss is continuous light pulse sequence in the sensor fibre 2; (width) has no restriction the cycle of light pulse in the sequence; Can get arbitrarily small value in theory; Therefore can increase the sample frequency of sensor fibre 2 losses through reducing the width of light pulse in the sequence, thereby make computer 5 can leak the characteristic of the loss that on sensor fibre 2, produces with third party's intrusion event that possibly cause pipe damage at bigger spectral range analysis conduit.
3) at sensor fibre 2 input ends, the backscattering optical signal that the light pulse sequence of gathering the modulation of Golay sign indicating number and their radix-minus-one complements respectively produces in the propagation process forward along sensor fibre 2, and synthetic new backscattering optical signal.
Light pulse sequence constantly produces back-scattering light in the propagation process forward along sensor fibre 2.The input end of back-scattering light along optical fiber 2 backpropagations to sensor fibre 2.Computer 5 is respectively with the amplitude of the light pulse signal of Golay sign indicating number and their radix-minus-one complement modulated laser pulse oscillator 101 output; The backscattering optical signal that the light pulse sequence that back-scattering light testing module 3 is gathered the modulation of Golay sign indicating number and their radix-minus-one complements respectively produces in the propagation process forward along sensor fibre 2, and send computer 5 to handle; Computer 5 utilizes above-mentioned backscattering optical signal to synthesize new backscattering optical signal; Synthetic backscattering optical signal aspect spatial resolution with sequence in backscattering optical signal identical of single light pulse, aspect signal intensity, than individual pulse by force, and be directly proportional with the number of light pulse in the sequence.
Below be the embodiment that the inventor provides:
1) computer 5 utilizes formula (2) to generate one group of Golay sign indicating number A and B, and their radix-minus-one complement
and
A
(n+1)＝A
(n)|B
(n)
(2)
Wherein
Be B
(n)Radix-minus-one complement, if the sign indicating number B
(n)Be 1, then the sign indicating number
Be-1, if instead sign indicating number B
(n)Be-1, then the sign indicating number
Be 1; | be connector, therefore, the Golay sign indicating number A and the B of generation, and their radix-minus-one complement
With
Length L be 2 power power.The self correlation function r of Golay sign indicating number A and B
A(k) and r
B(k) with have a following characteristic:
r
A(k)+r
B(k)＝2Lδ
k (3)
Wherein
Suppose A
(0)=1 and B
(0)=1,64 the Golay sign indicating number A and the B that generate according to formula (2) so are respectively:
A＝{111-111-11?111-1-1-11-1?111-111-11?-1-1-1111-11}
+{111-111-11?111-1-1-11-1?-1-1-11-1-11-1?111-1-1-11-1}
B＝{111-111-11?111-1-1-11-1?111-111-11?-1-1-1111-11}
+{-1-1-11-1-11-1?-1-1-1111-11?111-111-11?-1-1-1111-11}
Fig. 2 is the waveform of above-mentioned 64 Golay sign indicating number A and B.
Fig. 3 be above-mentioned 64 Golay sign indicating number A and B self correlation function and their self correlation functions and waveform; Wherein Fig. 3 (a) is the waveform of Golay sign indicating number A self correlation function; Fig. 3 (b) is the waveform of Golay sign indicating number B self correlation function, Fig. 3 (c) be Golay sign indicating number A and B self correlation function and waveform.Can find out from Fig. 3 (c), the self correlation function of 64 Golay sign indicating number A and B be δ.
2) computer 5 utilizes formula (5) with bipolarity Golay sign indicating number A and B, and their radix-minus-one complement
With
Convert unipolar pulse sequence P to
A, P
B,
With
(5)
Wherein
is that length equals L, and each code element all is 1 pulse sequence.Pulse sequence P
A, P
B,
With
The value or 1 of each code element, or 0.5.
Fig. 4 is pulse sequence P from top to bottom successively
A, P
B,
With
Waveform.
3) computer 5 is used pulse sequence P
AModulated laser pulse oscillator 101; Symbol value is that the peak power of the light pulse of laser pulse generator 101 outputs in 1 o'clock is its maximum values that allow output, and symbol value is that the peak power of the light pulse of laser pulse generator 101 outputs in 0.5 o'clock is that it allows output peaked half the.
4) P
AThe light pulse sequence of modulation propagates into output terminal along sensor fibre 2, is gathered by optical fiber Output optical power testing module [4], and send computer 5 to handle.
5) optical pulse sequence signal of 5 pairs of optical fiber Output optical power of computer testing module, 4 collections carries out amplitude transformation by following rule: if a certain pulse is at P in the optical pulse sequence signal
AIn the value of corresponding code element be 0.5, then the amplitude of this pulse signal multiply by 2, otherwise constant.
The amplitude of optical pulse sequence signal is only relevant with the disturbance that pipe leakage and intrusion event produce after the conversion, thereby has eliminated modulation signal P
AInfluence.Because the length L of pulse sequence is 2 power power, therefore be more suitable for carrying out Digital Signal Processing.
For example, P
ABe coupled into sensor fibre 2 and propagate forward along optical fiber 2, suppose in propagation process, to receive the interference of external event, optical fiber 2 output signals are shown in Fig. 5 (a), and the output signal after the conversion is shown in Fig. 5 (b) so.As can be seen from Figure 5, modulation signal Golay sign indicating number A is eliminated, and its output is only relevant with the interference that external event produces.
6) on the other hand, along sensor fibre 2 forward in the propagation process, P
AThe optical pulse sequence signal of modulation constantly produces back-scattering light, and back-scattering light is along optical fiber 2 backpropagations and turn back to input end, by back-scattering light power detection module collection 3 and send computer 5 to handle.The response of supposing the backscattering optical signal of 2 pairs of single light pulses of sensor fibre is h
f, input is P so
ADuring the optical pulse sequence signal of modulation, corresponding backscattering optical signal is P
AAnd h
fConvolution, note is made P
A* h
f
7) use P respectively
B,
With
Replace P
A, repeating step 3) and-6), back-scattering light power detection module 3 is gathered corresponding backscattering optical signal, and send computer 5 to handle.
Fig. 6 is that computer 5 utilizes P
A, P
B,
With
The process of the new backscattering optical signal of backscattering light compositing:
(1) computer 5 is with the P that gathers
AWith
The back-scattering light signal subtraction, and then carry out related operation with Golay sign indicating number A, note is made x
A
(2) computer [5] is with the P that gathers
BWith
The back-scattering light signal subtraction, and then carry out related operation with Golay sign indicating number B, note is made x
B
(3) results added that step (1) and (2) is obtained, computer 5 obtains synthetic backscattering optical signal:
Therefore, the intensity of synthetic backscattering optical signal be monopulse the backscattering optical signal L doubly, and their spatial resolution is identical.
In distributed fiberoptic sensor based on OTDR oil and gas pipeline leakage and intrusion detection; The present invention proposes light pulse sequence with the modulation of Golay sign indicating number and their radix-minus-one complements as detected signal, so what propagate in the sensor fibre 2 is that length L is the continuous light pulse sequence signal of 2 power power.The Golay sign indicating number is coupled into sensor fibre 2 with the light pulse sequence of their radix-minus-one complements modulation; In the process that light pulse sequence is propagated forward along sensor fibre 2, the disturbance modulation that its amplitude is produced by pipe leakage and intrusion event; At the output terminal of sensor fibre 2, optical pulse sequence signal is gathered by optical fiber Output optical power testing module 4 and is sent computer 5 to handle; Computer 5 at first carries out amplitude transformation to optical pulse sequence signal, eliminates the modulation of Golay sign indicating number and their radix-minus-one complements, and the interference of the external event that the variation of output signal amplitude only receives with sensor fibre 2 after the conversion is relevant; Computer 5 is through frequency analysis, the characteristic that transmission loss changes when obtaining sensor fibre 2 and receiving external event and disturb.
On the other hand, light pulse sequence constantly produces back-scattering light in the propagation process forward along sensor fibre 2.Back-scattering light is along optical fiber 2 backpropagations and turn back to the input end of sensor fibre 2.Computer 5 is respectively with the amplitude of the light pulse signal of Golay sign indicating number and their radix-minus-one complement modulated laser pulse oscillator 101 output; The backscattering optical signal that the light pulse sequence that back-scattering light testing module 3 receives the modulation of Golay sign indicating number and their radix-minus-one complements respectively produces in the propagation process forward along sensor fibre 2, and send computer 5 to handle; Computer 5 utilizes above-mentioned backscattering optical signal to synthesize new backscattering optical signal; Synthetic backscattering optical signal aspect spatial resolution with sequence in backscattering optical signal identical of single light pulse, aspect signal intensity, than individual pulse by force, and be directly proportional with the number of light pulse in the sequence.
Because detected signal is continuous light pulse sequence in the sensor fibre 2, it also is the sampled signal of sensor fibre 2 losses.Therefore, can improve the sample frequency of sensor fibre 2 losses through reducing the width of pulse in the light pulse sequence, thereby make system analyze the characteristic that external event causes sensor fibre 2 newly-increased losses at bigger spectral range; And the minimizing of light impulse length helps to improve the spatial resolution of synthesizing the backscattering optical signal.On the other hand, can increase the intensity of synthetic backscattering optical signal and improve signal to noise ratio, thereby increase the distance that distributed fiberoptic sensor detects pipeline through increasing the number of pulse in the light pulse sequence; And, through increasing the number of pulse in the sequence, can increase the sampling number of sensor fibre 2 transmission losses, help analysis to newly-increased loss characteristics on the sensor fibre 2.
Therefore the method for the invention can either increase the distance that distributed fiberoptic sensor detects pipeline through the intensity and raising signal to noise ratio that strengthens the backscattering optical signal; Again can be through increasing the sample frequency of sensor fibre 2 losses; Leak the characteristic of the loss that on sensor fibre 2, produces with third party's intrusion event at bigger spectral range analysis conduit, thereby improvement is based on the overall performance of the distributed fiberoptic sensor of OTDR oil and gas pipeline leakage and intrusion detection.
Claims (9)
1. a method that improves the distributed fiberoptic sensor performance of oil and gas pipeline leakage and intrusion detection is characterized in that, may further comprise the steps:
1) near oil and gas pipes, with optical cable of the parallel laying of oil and gas pipes, utilize sensor fibre [2] as sensor, oil and gas pipeline leakage and third party's intrusion event are monitored in real time;
2), a back-scattering light testing module [3] and optical fiber Output optical power testing module [4] are set respectively at the two ends of sensor fibre [2];
Computer [5] is used Golay sign indicating number and their radix-minus-one complement modulated laser pulse oscillator [101] respectively, and what make laser pulse generator [101] output is that amplitude is by the continuous light pulse sequence of Golay sign indicating number with the modulation of their radix-minus-one complements;
The light pulse sequence of laser pulse generator [101] output is through isolator [101] and Coupler [103] is coupled into sensor fibre [2] and propagation forward in sensor fibre [2]; Output terminal in sensor fibre [2], Output optical power testing module [4] is gathered the light pulse sequence of sensor fibre [2] output, and send computer [5] to handle; Computer [5] carries out amplitude transformation to the pulse sequence signal of Output optical power testing module [4] output, eliminates the modulation of Golay sign indicating number and their radix-minus-one complements; Computer [5] is accomplished the measurement of sensor fibre [2] overall diameter total losses dynamic change and the judgement of fault type through the analysis to the optical fiber after the conversion [2] Output optical power signal;
The backscattering optical signal that the light pulse sequence that input end in sensor fibre [2], back-scattering light testing module [3] are gathered the modulation of Golay sign indicating number and their radix-minus-one complements respectively produces in the propagation process forward along sensor fibre [2], and send computer [5] to handle; Computer [5] utilizes above-mentioned backscattering optical signal to synthesize new backscattering optical signal; Synthetic backscattering optical signal aspect spatial resolution with sequence in backscattering optical signal identical of single light pulse; Aspect signal intensity; Strong than individual pulse, and be directly proportional with the number of light pulse in the sequence; Computer [5] is accomplished sensor fibre [2] and is gone up the static state of each point and the measurement and the location of dynamic loss through the analysis to the new backscattering optical signal that synthesizes;
3) analysis and the fusion of computer [5] through sensor fibre [2] is gone up lossy data, the pressure around the acquisition oil and gas pipes and the characteristic of oscillating signal are judged and the location oil and gas pipes is revealed and the generation of third party's intrusion event.
2. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; Described laser pulse generator [101] is laser diode or laser triode, and the width of the light pulse of its output and energy are controlled.
3. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; Sensor fibre in the described sensing optic cable [2] is SMF Single Mode Fiber or multi-mould optical fibre, and its transmission loss is responsive to deformation, pressure and oscillating signal.
4. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; Described Output optical power testing module [4] comprises optical power detector [401], amplification and low-pass filter [402], mould/number conversion and DSP digital signal processor [403] unit, is used to gather the light train pulse signal of sensor fibre [2] output.
5. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; Described back-scattering light testing module [3] comprises optical power detector [301], amplification and low-pass filter [302], mould/number conversion and DSP digital signal processor [303] unit, is used to gather the backscattering optical signal of sensor fibre.
6. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; What described laser pulse generator [101] was exported is continuous light pulse sequence, and the width of pulse is identical in the sequence, and amplitude is by Golay sign indicating number and their radix-minus-one complement modulation; The length of pulse is identical with the length of Golay sign indicating number and their radix-minus-one complements in the sequence, all is power powers of 2.
7. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; The light pulse sequence of described Golay sign indicating number and their radix-minus-one complements modulation is to be input to respectively at a certain time interval in the sensor fibre [2], and its minimum interval equals last light pulse produces at sensor fibre [2] output terminal in the sequence back-scattering light and turns back in sensor fibre [2] input end and the sequence time difference that first light pulse is input to sensor fibre [2].
8. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; Described Golay sign indicating number and their radix-minus-one complement are pseudo-random signals; Output terminal in sensor fibre [2], the pulse sequence signal that computer [5] is gathered Output optical power testing module [4] carries out amplitude transformation, eliminates the modulation of Golay sign indicating number and their radix-minus-one complements; The amplitude of conversion afterpulse sequence signal is only relevant with the disturbance that pipe leakage and third party's intrusion event produce.
9. the method for the distributed fiberoptic sensor performance of raising oil and gas pipeline leakage as claimed in claim 1 and intrusion detection; It is characterized in that; Described back-scattering light testing module [3] and Output optical power testing module [4] are worked simultaneously or are worked alone, and back-scattering light testing module [3] is accomplished sensor fibre [2] and gone up the static state of each point and the measurement and the locating function of dynamic loss; Output optical power testing module [4] is accomplished sensor fibre [2] and is gone up the measurement of total losses dynamic change and the decision-making function of fault type.
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