CN101464166B - Optical fiber distributed perturbation sensor and method for implementing perturbation positioning - Google Patents
Optical fiber distributed perturbation sensor and method for implementing perturbation positioning Download PDFInfo
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- CN101464166B CN101464166B CN200910076263XA CN200910076263A CN101464166B CN 101464166 B CN101464166 B CN 101464166B CN 200910076263X A CN200910076263X A CN 200910076263XA CN 200910076263 A CN200910076263 A CN 200910076263A CN 101464166 B CN101464166 B CN 101464166B
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- interferometer
- optical fiber
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Abstract
The invention discloses an optical fiber distributed disturbance sensor, and a method, by which the disturbance sensor can achieve disturbance positioning. The method is characterized in that light path output signals from an interferometer are divided into three equal paths of light, pass through analyzers with polarization angle differences of 0 DEG, 60 DEG and minus 60 DEG respectively, enter a photo detector and are converted to electrical signals therein, are subjected to the square summing calculation after being conditioned by filtered signals and amplified signals, get rid of the DC amount by filtration, and are taken as the final interference output signals for related computation so that disturbance positioning can be carried out. The method can ensure the final interference signals always remain in a certain amplitude range and available, and the possibility of the signals being zero is zero. The invention solves the problem in the prior dual interferometer type distributed disturbance sensor that the sensor doesn't work when the amplitude of the light path output signals of the interferometer changes to zero because of the random variation of the polarization state of light wave.
Description
Technical field
The present invention relates to a kind of Fibre Optical Sensor, relate in particular to a kind of optical fiber distributed perturbation sensor and realize the method for disturbance location.
Background technology
Fibre Optical Sensor has widely in industry, civilian and military field and uses because its anti-electromagnetic interference (EMI), volume is little, in light weight, susceptibility is high, be easy to networking, particularly can realize good characteristic such as distributed measurement.Wherein, optical fiber distributed perturbation sensor is significant in perimeter alarm, oil pipeline monitoring and other structure monitoring field.
At present, according to the difference of principle of work, optical fibre distribution type sensor has polytypes such as interferometer type, grating type optical fiber, optical time domain reflectometer type, intensity modulation type and scatter-type.Wherein, the interferometer type distributed sensor has to be realized that principle is simple, highly sensitive, device cost is low, is suitable for long-distance sensing and good characteristic such as uses, and has become the main technical schemes of optical fiber distributed perturbation sensor.
In the prior art, the interferometer type optical fiber distributed perturbation sensor adopts the dual interferometer structure more, for example the conspicuous Zehnder interferometer structure of span, Sagnac-Mach Zehnder interferometer structure etc.
As shown in Figure 1, be based on the light path principle figure of the optical fiber distributed perturbation sensor of the conspicuous Zehnder interferometer of span.The light wave that light source sends is via coupling mechanism 1 beam split, and a part is injected pickup arm L through coupling mechanism 2
aWith reference arm L
b, 3 places interfere at coupling mechanism, through optical fiber L
dTransmission is received by photodetector 1, has constituted first interferometer.Another road light wave of coupling mechanism 1 output is through optical fiber L
cTransmission is injected pickup arm L from coupling mechanism 3
aWith reference arm L
b, 2 places interfere at coupling mechanism, are received by photodetector 2, have constituted second interferometer.Optical fiber in the above light path is single-mode fiber.Wherein, φ (t) is the phase modulation (PM) that disturbance causes; When disturbance is applied to pickup arm, more than two Mach Zehnder interferometers receive identical phase modulation (PM) φ (t), but since in two interferometers the fiber lengths of disturbance location range finder different; This disturbance modulation signal arrives the asynchronism(-nization) of two detectors, is respectively t
1And t
2, through confirming mistiming t
1-t
2, can obtain the disturbance location, realize the location.
Referring to Fig. 1, suppose that disturbance occurs in the x position of pickup arm again, then to arrive the light path that photodetector 1 passes by be n (L to the disturbing signal of first interferometer (being coupling mechanism 3)
a-x+L
d), the light path that the disturbing signal arrival photodetector 2 of second interferometer (being coupling mechanism 2) is passed by is nx, the mistiming that the disturbing signal of two interferometers reaches detector is:
Δt＝n(L
a-2x+L
d)/c (1)
Wherein, n is the effective refractive index of fiber core, and c is a light speed in a vacuum.In order to realize location to the disturbance location, only need to measure Δ t, can calculate disturbance location x through following formula:
x＝(L
a+L
d-cΔt/n)/2 (2)
In follow-up localization process, because the phase modulated signal of two interferometers is relevant fully in theory, only there is time delay, through calculating cross correlation function, determine the corresponding time delay of cross correlation function maximal value, can obtain the mistiming.
As shown in Figure 2, be based on the schematic diagram of the location algorithm of the conspicuous distributed perturbation sensor of Zehnder interferometer type of span.
There is following shortcoming in above-mentioned prior art at least based on the conspicuous Zehnder interferometer type optical fiber distributed perturbation sensor of span:
Because the needs that long-distance sensing reduces cost, sensor all adopts single-mode fiber.Induce birefringence because intrinsic intrinsic birefringence of single-mode fiber itself and extraneous enchancement factor cause; Random variation can take place in the polarization state of the light wave that transmits in the single-mode fiber; Thereby make when interfering, in pickup arm and reference arm, transmit the amplitude generation random variation of the light vector that is in identical direction of vibration (electric field intensity) component of light wave respectively, thereby the amplitude of interferometer output signal is changed; Especially when two arm optical polarization quadratures; Can not interfere, the amplitude of interferometer output signal is 0, makes sensor complete failure.
Because the instability of interferometer output signal amplitude possibly make sensor the failure conditions of non-output signal in the regular hour scope, occur, has influenced the reliability of sensor in actual monitoring is used.
Summary of the invention
The purpose of this invention is to provide and a kind ofly can keep the optical fiber distributed perturbation sensor that interferometer output signal has stable available amplitude and realize the method for disturbance location.
The objective of the invention is to realize through following technical scheme:
Optical fiber distributed perturbation sensor of the present invention; Comprise first interferometer, second interferometer; The output terminal of said first interferometer and second interferometer is connected with optical splitter respectively, and the multi-channel output of said optical splitter is connected with analyzer respectively, is connected with photodetector after the said analyzer.
Above-mentioned optical fiber distributed perturbation sensor of the present invention is realized the method for disturbance location, comprises step:
At first, with the output signal demultiplexing light wave of each interferometer;
Then, the multichannel light wave according to the output signal of two interferometers carries out the disturbance location.
Technical scheme by the invention described above provides can be found out; The method of optical fiber distributed perturbation sensor of the present invention and realization disturbance location thereof is because the output signal of first interferometer and second interferometer at first passes through optical splitter and analyzer demultiplexing light wave; Then, the multichannel light wave of the output signal of two interferometers is handled, carried out the disturbance location.Can keep the output signal of interferometer to have stable available amplitude.
Description of drawings
Fig. 1 is based on the light path principle figure of the conspicuous distributed perturbation sensor of Zehnder interferometer type of span in the prior art;
Fig. 2 is based on the schematic diagram of the location algorithm of the conspicuous distributed perturbation sensor of Zehnder interferometer type of span in the prior art;
Fig. 3 is the light path principle figure of optical fiber distributed perturbation sensor of the present invention;
Fig. 4 is the schematic diagram that optical fiber distributed perturbation sensor of the present invention is realized the method for disturbance location.
Embodiment
Optical fiber distributed perturbation sensor of the present invention; Its preferable embodiment is; Comprise first interferometer, second interferometer; The output terminal of first interferometer and second interferometer is connected with optical splitter respectively, and the multi-channel output of optical splitter is connected with analyzer respectively, is connected with photodetector after the analyzer.
The output terminal of optical splitter can have three the tunnel, and accordingly, each optical splitter is connected with 3 analyzers, and the polarization angle of 3 analyzers differs and is respectively: 0 ± 10 degree, 60 ± 10 degree ,-60 ± 10 degree, or 0 ± 10 degree, 60 ± 10 is spent, 120 ± 10 degree.As required, also multichannel can be arranged, for n road situation, the polarization angle of each analyzer differs to 180/n degree successively respectively.
First interferometer and second interferometer are Mach Zehnder interferometer.
Can be connected with after a plurality of photodetectors after each optical splitter and square add and the unit, square add and to be connected with calculating cross correlation function unit through high-pass filtering (filtering DC quantity) with the output terminal of unit.Square add with the unit and can comprise: be connected with squaring cell respectively after the photodetector, a plurality of squaring cells are connected with addition unit respectively.
Can be connected with the amplification filtering unit between photodetector and the squaring cell; Square add and unit and calculating cross correlation function unit between be connected with filter unit.
Above-mentioned optical splitter comprises following at least a device: 1 * 3 single-mode optical-fibre coupler spare, part reflective semitransparent film space optics etc., or other light-splitting device;
Above-mentioned analyzer can comprise following at least a device: wave plate type analyzing device, prism devices etc., or other device.
Optical fiber distributed perturbation sensor of the present invention is realized the method for disturbance location, and its preferable embodiment is to comprise step:
At first, with the output signal demultiplexing light wave of each interferometer; Then, the multichannel light wave according to the output signal of two interferometers carries out the disturbance location.
Specifically can with the multichannel light wave of interferometer through square add and after, carry out cross correlation function again and calculate, realize the disturbance location.
The multichannel polarized light can be at first through after the amplification filtering, carry out again square adding with; Then, after flow component is propped up in process filtering elimination again, carry out cross correlation function again and calculate;
The signal that process filtering elimination is propped up after the flow component is: in
formula, A is a signal amplitude;
is phase modulated signal; β is poor for the random phase that the polarization state random variation produces.
The present invention is on the basis of the conspicuous Zehnder interferometer type optical fiber distributed perturbation sensor of existing span, and the interferometer output back in light channel structure has increased analyzer, and is making corresponding change aspect input and the processing.
Through specific embodiment the present invention is carried out detailed elaboration below:
As shown in Figure 3, be the light path principle figure of specific embodiment of the present invention, the light wave that light source sends is via coupling mechanism 1 beam split, and a part is injected pickup arm L through coupling mechanism 2
aWith reference arm L
b, 3 places interfere at coupling mechanism, through optical fiber L
dTransmission has constituted first interferometer;
Another road light wave of coupling mechanism 1 output is through optical fiber L
cTransmission is injected pickup arm L from coupling mechanism 3
aWith reference arm L
b, 2 places interfere at coupling mechanism, and output, have constituted second interferometer.
Optical fiber in the above light path is single-mode fiber.First interferometer and second interferometer are Mach Zehnder interferometer.
Wherein, φ (t) is the phase modulation (PM) that disturbance causes, when disturbance is applied to pickup arm, more than two Mach Zehnder interferometers receive identical phase modulation (PM) φ (t).In the prior art, the light path output signal of the light path of first interferometer output signal and second interferometer is directly received by photodetector, because the phase modulated signal that disturbance causes in two interferometers arrives the asynchronism(-nization) of two photodetectors, is respectively t
1And t
2, through confirming mistiming t
1-t
2, can obtain the disturbance location, realize the location.
In the above-mentioned specific embodiment, in order to solve the disabled problem of optical path signal amplitude of interferometer output, the light path output signal of two interferometers; Directly do not get into photodetector; But through three tunnel of amplitudes such as optical splitter is divided into respectively, and get into analyzer respectively, wherein; The polarization angle of three tunnel analyzer differs and is respectively 0 degree, 60 degree and-60 degree.Through three road later light signals of analyzer, get into photodetector respectively, be converted into electric signal.
As shown in Figure 4, be input and the handling principle figure in the above embodiments.The electric signal of photodetector output is for eliminating noise and disturb through after the conditionings such as filtering and amplification, difference square, addition then.The electric signal of exporting after the addition is through high-pass filtering elimination DC component, through the signal I of filtering
1, I
2Respectively as the output signal of first and second Mach Zehnder interferometer, because the processing of two paths of signals is identical, do not destroy the correlativity between the phase modulated signal that two disturbances in the interferometer cause, carry out cross-correlation calculation, can realize the location.
Through the signal I after the above processing
1, I
2Can not receive the influence of polarization state random variation, its amplitude can keep within the specific limits, does not occur being reduced to 0 possibility, and to export signal constantly be 0 thereby eliminate certain, the problem of sensor failure.
Usually; The light source that is adopted is single longitudinal mode narrow-band light source (the about 100kHz of live width); Its output light-wave can be thought full-polarization (actual light source send light wave degree of polarization near 100%), is without loss of generality, and can the light wave that light source sends be regarded as the arbitrary ellipse polarized light; At first analyze the light wave in first interferometer, the light wave in second interferometer has same mathematical expression.The electric field intensity that is located at the light wave of forward transmitted in interferometer two arms is E
sAnd E
r, its position angle and ellipticity angle are θ
s, θ
rAnd ε
sAnd ε
rIts Jones vector is:
When interfering, interfere light intensity:
I＝|E
sx+E
rx|
2+|E
sy+E
ry|
2 (7)
Wherein, interference term is:
Wherein, a=cos (θ
s-θ
r) cos (ε
s-ε
r), b=sin (θ
s-θ
r) sin (ε
s+ ε
r).
When sensor fibre receives perturbation when moving, the output signal of two interferometers is:
Wherein, A is a direct current biasing, and B is the amplitude of interference term,
With
Be respectively the moving phase modulation (PM) that causes of perturbation, t
1And t
2Be the time, t
1-t
2Be the mistiming, through confirming t
1-t
2Can obtain the disturbance location.
For the situation that increases analyzer, be the analyzer of θ through angle after the light wave beam split of interferometer output with the x axle, the interference signal in the interferometer output intensity of this moment is:
Wherein
a＝cos(ε
s-ε
r)cos(θ
s-θ
r)+cos(ε
s+ε
r)cos(θ
s+θ
r-2θ) (13)
b＝sin(ε
s+ε
r)sin(θ
s-θ
r)+sin(ε
s-ε
r)sin(θ
s+θ
r-2θ) (14)
For add behind the three-way output signal square with, obtain:
After filtering dc terms:
Wherein, A is a signal amplitude;
is phase modulated signal, and β is poor for the random phase that the polarization state random variation produces.(annotate: β can influence bearing accuracy, if in order to improve bearing accuracy, can also take other ways to eliminate β simultaneously.What but the present invention will solve is the problem that holding signal can be used amplitude, does not solve the problem that improves bearing accuracy, so do not eliminate β in the present invention.)
For two interferometers, through light-splitting device, through behind three road analyzers squares, the output signal that adds with the elimination dc terms be respectively:
With above I
1, I
2Cross-correlation calculation is carried out in final output as interferometer, realizes the location.
Among the present invention, five equilibrium behind the light path output signal process light-splitting device of interferometer being become three road light, is 0 degree through difference angle respectively; 60 the degree with-60 the degree (or 0 the degree, 60 the degree, 120 the degree) analyzer; Get into photodetector and be converted into electric signal, behind signal conditions such as filtering and amplification, carry out quadratic sum and add and calculate; Carry out cross-correlation calculation as the final output signal of interfering after the elimination DC quantity, carry out the disturbance location.Through above step; Final interference signal is remained in certain amplitude range; Keep its availability; Elimination is 0 possibility, solves the existing distributed perturbation sensor of dual interferometer type because the signal amplitude that the random variation of optical polarization causes is changed to the problem of 0 o'clock sensor failure;
When the electric signal magnitude that solves the final output of the existing distributed perturbation sensor interferometer of dual interferometer type is the problem of 0 o'clock sensor failure; Kept two interferometer output signal uniformity of treatments, thereby do not lost the not bearing accuracy of shadow sensor of its correlativity;
Because signal Processing scheme of the present invention is to handle to the light path output of interferometer, does not therefore receive the influence of sensor fibre length, is suitable for the situation that sensor fibre is any length.
In fact, when interferometric sensor adopts single-mode fiber, all there is the problem of interfering output signal random variation, and possibly in the certain hour scope, the amplitude of its interference output signal is 0, make sensor failure.
Existing interferometer type optical fiber distributed perturbation sensor; Because the distance of sensor fibre is grown (tens to tens kilometers), the sensing light path adopts the relatively low single-mode fiber of cost usually, therefore; The polarization state generation random variation of the light wave that the intrinsic birefringence meeting that the extraneous factor of random variation causes induces birefringence and optical fiber itself to exist causes transmitting in the single-mode fiber; Can cause the polarization state of light wave of pickup arm and signal arm distinct thus, have only between light vector (electric field intensity) component of identical polarization state (direction of vibration) just can interfere, thus the amplitude generation random variation of interference signal; Even the polarization state of working as the light wave of two arms is in quadrature condition; The situation that generation can not be interfered, the amplitude of interfering the output signal is 0 situation, has had a strong impact on the achieved reliability of optical fiber distributed perturbation sensor.
Optical fiber distributed perturbation sensor of the present invention can keep interferometer output signal to have stable available amplitude.
The above; Be merely the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technician who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.
Claims (9)
1. optical fiber distributed perturbation sensor; Comprise first interferometer, second interferometer; It is characterized in that; The output terminal of said first interferometer and second interferometer is connected with optical splitter respectively, and the multi-channel output of said optical splitter is connected with analyzer respectively, is connected with photodetector after the said analyzer;
Be connected with after a plurality of photodetectors after the said optical splitter and square add and the unit, said square adds with the output terminal of unit and is connected with calculating cross correlation function unit.
2. optical fiber distributed perturbation sensor according to claim 1 is characterized in that the output terminal of said optical splitter has three the tunnel, and corresponding, each optical splitter is connected with 3 analyzers.
3. optical fiber distributed perturbation sensor according to claim 2 is characterized in that, the polarization angle of said 3 analyzers is respectively: 0 ± 10 degree, 60 ± 10 degree ,-60 ± 10 degree; Or 0 ± 10 the degree, 60 ± 10 the degree, 120 ± 10 the degree.
4. optical fiber distributed perturbation sensor according to claim 1 is characterized in that, described first interferometer and second interferometer are respectively Mach Zehnder interferometer.
5. optical fiber distributed perturbation sensor according to claim 1 is characterized in that, said square adds with the unit and comprise: be connected with squaring cell respectively after the said photodetector, a plurality of squaring cells are connected with addition unit respectively;
Be connected with the amplification filtering unit between said photodetector and the said squaring cell; Said square add and unit and said calculating cross correlation function unit between be connected with filter unit.
6. optical fiber distributed perturbation sensor according to claim 1 is characterized in that, said optical splitter comprises following at least a device: 1 * 3 single-mode optical-fibre coupler, part reflective semitransparent film space optics;
Said analyzer comprises following at least a device: wave plate type analyzing device, prism devices.
7. each described optical fiber distributed perturbation sensor of claim 1 to 6 is realized the method for disturbance location, it is characterized in that, comprises step:
At first, with the output signal demultiplexing light wave of each interferometer;
Then, the multichannel light wave according to the output signal of two interferometers carries out the disturbance location.
8. optical fiber distributed perturbation sensor according to claim 7 is realized the method for disturbance location; It is characterized in that, said interferometer is converted into electric signal through the multichannel light wave of optical splitter and the output of multichannel analyzer through photodetector, after the electric signal of photodetector output is nursed one's health through amplification filtering; Carry out square adding and calculating; After filtering DC quantity, carry out cross correlation function again and calculate, realize the disturbance location.
9. optical fiber distributed perturbation sensor according to claim 8 is realized the method for disturbance location; It is characterized in that; Signal after the said filtering elimination DC quantity is:
in the formula, A is a signal amplitude;
is phase modulated signal; β is poor for the random phase that the polarization state random variation causes.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101963516B (en) * | 2010-09-20 | 2012-06-27 | 南京大学 | Polarization-sensitive distributed perturbation sensing and measuring method and system |
| CN102997945B (en) * | 2011-09-16 | 2015-09-16 | 北京航空航天大学 | The multipoint disturbance positioning method of optical fiber distributed perturbation sensor |
| CN102401667B (en) * | 2011-09-29 | 2016-03-30 | 北京航空航天大学 | There is optical fiber distributed perturbation method for sensing and the system of disturbance character recognition function |
| CN103292889B (en) * | 2013-05-23 | 2014-12-10 | 无锡聚为传感科技有限公司 | Distributed optical fiber vibrating sensor vibration source locating method |
| CN108133582B (en) * | 2017-12-29 | 2019-11-26 | 上海复栋智能科技有限公司 | A kind of important accident alarming method for positioning analyzing for distributed sensing system |
| CN109596203A (en) * | 2018-11-09 | 2019-04-09 | 武汉伊莱维特电力科技有限公司 | System is monitored based on cable passage hidden trouble in a distributed manner |
| CN111486938A (en) * | 2020-04-03 | 2020-08-04 | 中国地质大学（武汉） | Interference type optical fiber vibration sensing detection system and method based on self-adaptive filtering |
| CN112284690B (en) * | 2020-10-28 | 2022-11-01 | 山东省科学院激光研究所 | Testing device for accurately measuring distribution of distributed radial refractive indexes of optical fibers |
| CN114719889B (en) * | 2021-01-05 | 2024-03-26 | 中国石油天然气股份有限公司 | Optical fiber distributed disturbance sensor and disturbance signal positioning method |
| CN114018392B (en) * | 2021-11-04 | 2024-03-01 | 全球能源互联网研究院有限公司 | Polarization fading inhibition method and device |
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