CN105466548B - Phase sensitive optical time domain reflection optical fiber sensing system localization method - Google Patents

Phase sensitive optical time domain reflection optical fiber sensing system localization method Download PDF

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CN105466548B
CN105466548B CN201510941674.6A CN201510941674A CN105466548B CN 105466548 B CN105466548 B CN 105466548B CN 201510941674 A CN201510941674 A CN 201510941674A CN 105466548 B CN105466548 B CN 105466548B
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CN105466548A (en
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庞拂飞
贺梦婷
梅煊玮
张小贝
王廷云
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University of Shanghai for Science and Technology
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01HMEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G01H9/004Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors

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Abstract

The present invention relates to a kind of phase sensitive optical time domain reflection optical fiber sensing system localization methods, the following steps are included: the position X1 and Z1 and X2 and Z2 that acquire the corresponding beat frequency digital signal of multiple light pulse, obtain back-scattering light phasing matrix Ф, determine extraneous vibration disturbance location Y, choosing before and after extraneous vibrational perturbation position Y no phase perturbation respectively, to X1 and Z1 and X2 and Z2, respective column phase carries out phase unwrapping around phase change is extended to-∞ ~+∞ range in back-scattering light phasing matrix Ф;If the phase of position changes over time identical before and after phase perturbation position, judgement phase perturbation is wrong report;Otherwise, judgement phase perturbation is true extraneous vibration event.The present invention effectively solves the problems, such as to overcome the problems, such as that decline causes rate of false alarm high since polarization decay, interference fading introduce wrong abnormal phase in the application of Ф-OTDR system, realize the accurate positionin of true external disturbance event.It is simple and easy to do based on conventional Ф-OTDR distributed fiber-optic sensor system.

Description

Phase sensitive optical time domain reflection optical fiber sensing system localization method
Technical field
The present invention relates to a kind of phase optical fiber sensing system localization method more particularly to a kind of phase sensitive optical time domain reflection light Fiber sensor system localization method belongs to optical fiber sensing technology application field.
Background technique
Phase sensitive optical time domain reflection (Phase-sensitive Optical Time Domain Reflectometry, Be abbreviated as Ф-OTDR or Phase-sensitive OTDR) distributed fiber-optic sensor system be used for extraneous vibrational perturbation event It is monitored, the accurate positioning to extraneous vibrational perturbation event location may be implemented, there is the measurement of the distribution of line shape formula, long-range survey Amount, the advantages that highly sensitive, anti-electromagnetic interference capability is strong, good insulating, essential safety, small lightweight, are widely used It is general.In petrochemical industry, oil transportation, the tamper-proof excavation event monitoring of feed channel is may be implemented in Ф-OTDR, can be also used for oil gas Ultrasonic Well Logging in exploitation;In field of track traffic, rail vibration status monitoring is may be implemented in Ф-OTDR;It is commanded in power train The safety monitoring of cable tunnel, the monitoring of high-tension cable anti-theft etc. may be implemented in domain, Ф-OTDR;In safety-security area, Ф-OTDR It can be used as distributed optical fiber fence, alarm be monitored to various intrusion events.
In the application of actual measurement extraneous vibration, Ф-OTDR emits light pulse into sensor fibre, by optical fiber backwards to scattered The positioning that light reaches the time progress external disturbance event location of detecting terminal is penetrated, meanwhile, need the multiple light pulses of repeat its transmission To obtain the change information of disturbance location phase.However, Ф-OTDR technique the problems such as there are polarization decays, interference fading, can draw The phase change for entering mistake, to carry out the high problem of rate of false alarm to system surveying tape.It is high in order to solve the rate of false alarm that decline introduces Problem, Shanghai ray machine institute, Chinese Academy of Sciences Zhengqing Pan etc. proposes based on two kinds of Ф-of phase shift dipulse and multiburst OTDR system location technology (Zhenqing Pan, Kezhen Liang, Jun Zhou, Qing Ye, Haiwen Cai, Ronghui Qu, Interference-fading-free phase-demodulated OTDR system, Proc. of SPIE, 2012, 8421, 842129;Zhou Jun, Pan Zhengqing, Ye Qing, Cai Haiwen, Zhao Hao, Qu Ronghui, Fang Zujie are based on multifrequency The comprehensive Phase Demodulation Method of Optic Chinese laser for identifying interference fading glitch in φ-OTDR system of rate, 2013,40 (9): 0905003), both methods, which is all based on different excitation light pulses, can obtain the principle of different fading characteristics, to phase Variation carries out comprehensive judgement, and with the rate of false alarm that reduction decline introduces, this two technologies require special double/multiple-pulse and generate firmly Part system.(Wu extends protection big, Wu Huijuan, Rao Yunjiang, Wu Yu, Zhao Tian, is based on a variety of small echos in river Rao Yun of Chengdu University of Electronic Science and Technology etc. The low rate of false alarm distributed optical fiber fence system for monitoring intrusion of the comprehensive judgement of decomposition method, photonics journal, 2011,40 (11);Base In the distributed optical fiber fence intrusion detection of Ф-OTDR and localization method, Chinese invention patent, inventor: Wu Huijuan, Wu are extended protection Big, Li Shanshan, Rao Yunjiang apply for notification number: 102280001 A of CN) it proposes using the comprehensive judgement skill of a variety of wavelet-decomposing methods Art can reduce the rate of false alarm of fence invasion by the difference of not same order small echo result, this technology needs at complicated signal Adjustment method.
Summary of the invention
The purpose of the present invention is to provide a kind of phase sensitive optical time domain reflection optical fiber sensing system localization methods.
In order to solve the above technical problems, the invention adopts the following technical scheme:
A kind of phase sensitive optical time domain reflection optical fiber sensing system localization method,
The phase sensitive optical time domain reflection optical fiber sensing system, including 1,1 ' 2 fiber coupler 2 of narrow linewidth laser, Acousto-optic modulator 3, erbium-doped fiber amplifier 4, optical fiber circulator 5,6,2 ' 2 fiber coupler 7 of sensor fibre balance optical detector 8, data collecting card 9, computer 10;
Narrow linewidth laser 1 is divided into two-way by 1 ' 2 fiber coupler 2, wherein optical signal passes through acousto-optic modulator 3 all the way It is modulated to the light pulse of shift frequency, is input to using after the progress optical power amplification of erbium-doped fiber amplifier 4 by optical fiber circulator 5 It is transmitted in sensor fibre 6, the back-scattering light that excitation is transmitted in light pulse in sensor fibre 6 is carried out along sensor fibre 6 backwards to biography Defeated arrival optical fiber circulator 5;The back-scattering light point that the another way optical signal and optical fiber circulator 5 of 1 ' 2 fiber coupler 2 return It is not injected into 2 ' 2 fiber couplers 7 by two ports and transmits and be concerned with, two output ports of 2 ' 2 fiber couplers 7 and flat The optical detector 8 that weighs connects, and carries out photoelectric conversion and obtains back-scattering light beat frequency electric signal, collects number through data collecting card 9 Word beat signal exports to computer 10 the amplitude and phase information for calculating beat signal;
The following steps are included:
Step 1: the data collecting card 9 acquires 1 time or more the corresponding beat frequency digital signal of light pulse, it is anti-based on optical time domain Principle is penetrated, beat frequency digital signal two-dimensional matrix R=[R is constructed I, j ]MxN, wherein R I, j Indicate the capture card (9) collectedi Secondary light pulse is corresponding in sensor fibrejBack-scattering light beat frequency digital signal value on position;
Step 2: using digital quadrature demodulation signal processing method, carried on the back by the beat frequency digital signal two-dimensional matrix R To scattering light phase matrix Ф;
Step 3: two column Ф of k column will be separated by back-scattering light phasing matrix Фm,jAnd Фn,jSubtract each other, wherein k desirable 1 ~ 500, obtain the phase difference two-dimensional matrix S that beat signal is separated by k sampled point, wherein Sm,jm,jn,j, with sensor fibre Position is abscissa parameter, draws each row curve of matrix S, finds out phase perturbation position;
Step 4: choosing position an X1 and Z1 without phase perturbation respectively before and after the phase perturbation position And X2 and Z2, to X1 and Z1 and X2 and Z2 in the back-scattering light phasing matrix Ф respective column phase ФX1And ФZ1And ФX2 And ФZ2Phase unwrapping is carried out around phase change is extended to-∞ ~+∞ range;
Step 5: drawing Ф respectivelyXAnd ФZTwo column phase versus time curves, if before phase perturbation position The phase of position changes over time identical later, adjudicates the phase perturbation as wrong report;Otherwise, it is true for adjudicating the phase perturbation Extraneous vibration event.
The beneficial effects of the present invention are:
(1) present invention efficiently solves in Ф-OTDR optical fiber sensing system since polarization decay, interference fading introduce mistake The problem of abnormal phase, to overcome the problem for leading to wrong report in Ф-OTDR optical fiber sensing system due to signal fadeout.
(2) the present invention is based on conventional Ф-OTDR optical fiber sensing systems, without additional transmitting dipulse or multiple-pulse Hardware system and sophisticated signal processing method, meanwhile, polarization decay problem is avoided without polarization beam splitting optical detector technology.
Detailed description of the invention
Fig. 1 is phase sensitive optical time domain reflection optical fiber sensing system structure schematic diagram in the present invention;
Fig. 2 is flow chart of the invention;
Fig. 3 is the vibration location information figure obtained in the present invention by phase quadrature demodulation;
Fig. 4 is the front and back phase perturbation position P1 phase change curve graph in the present invention;
Fig. 5 is the front and back phase perturbation position P2 phase change curve graph in the present invention;
Wherein:
Narrow linewidth laser, 2 fiber coupler of 2- 1 ', 3- acousto-optic modulator, 4- erbium-doped fiber amplifier, 5- optical fiber Circulator, 6- sensor fibre, 2 fiber coupler of 7-2 ', 8- balance optical detector, 9- data collecting card, 10- computer, 11- piezoelectric ceramics.
Specific embodiment
To be more clear the technical problem to be solved in the present invention, technical solution and advantage, below in conjunction with attached drawing and tool Body embodiment is described in detail.
Embodiment 1:
Referring to Fig. 1, phase sensitive optical time domain reflection optical fiber sensing system, including 1,1 ' 2 fiber coupling of narrow linewidth laser Device 2, acousto-optic modulator 3, erbium-doped fiber amplifier 4, optical fiber circulator 5,6,2 ' 2 fiber coupler 7 of sensor fibre, balance light are visited Survey device 8, data collecting card 9, computer 10.
System components device description is as follows:
Narrow linewidth laser 1, for generating long coherence length laser;
1 ' 2 fiber coupler 2, for laser to be divided into two-way, all the way for sensing optical path, another way is used for reference light Road, sensing optical path optical power are much larger than reference path, and coupling splitting ratio can choose as 90:10;
Acousto-optic modulator 3, for being pulse laser by Laser Modulation, meanwhile, allow laser pulse to obtain the shifting of fixed frequency Frequently;
Erbium-doped fiber amplifier 4, for amplifying laser pulse, to be lifted at the back-scattering light excited in sensor fibre By force;
Optical fiber circulator 5 is a three fiber port circulators;
Sensor fibre 6 is standard traffic single-mode quartz optical fibers;
2 ' 2 fiber couplers 7, the multiplex for sensor fibre back-scattering light and local reference light are interfered, coupling light splitting Than for 50:50;
Optical detector 8 is balanced, for detecting light coherent signal, realizes photoelectric conversion, output is with the shifting of acousto-optic modulator 3 Frequent rate is the electric signal of beat frequency;
Data collecting card 9 exports the acquisition of electric signal for balancing optical detector 8, and beat signal is converted to numerical value and is clapped Frequency signal;
Computer 10, for handling data collecting card transducing signal collected.
Narrow linewidth laser 1 is divided into two-way by 1 ' 2 fiber coupler 2, wherein optical signal passes through acousto-optic modulator 3 all the way It is modulated to the light pulse of shift frequency, carries out optical power amplification by erbium-doped fiber amplifier 4 later, passes through optical fiber circulator 5 later It is input in sensor fibre 6 and transmits, light pulse is transmitted in sensor fibre 6 will excite back-scattering light, carry out along sensor fibre 6 Optical fiber circulator 5 is reached backwards to transmission.What the another way optical signal and optical fiber circulator 5 of 1 ' 2 fiber coupler 2 returned dissipates backwards It penetrates light and is injected separately into two ports to 2 ' 2 fiber couplers 7, two ways of optical signals is transmitted in 2 ' 2 fiber couplers 7 and phase Dry, two output ports of 2 ' 2 fiber couplers 7 are connect with balance optical detector 8, are carried out photoelectric conversion and are obtained back-scattering light Beat frequency electric signal, obtained electric signal collect digital beat signal through data collecting card 9, right by computer 10 later The beat signal carries out phase quadrature demodulation, obtains the amplitude and phase information of beat signal, i.e., the amplitude of back-scattering light and Phase change information.In order to simulate extraneous vibration event, a piezoelectric ceramics 11 is set on sensor fibre 6, in the present embodiment In, position of the piezoelectric ceramics 11 apart from optical fiber circulator 5 is 125m, and the vibration frequency of piezoelectric ceramics is 300 Hz.In the system In practical application, the extraneous vibration event that piezoelectric ceramics 11 is simulated can occur in any position of whole sensor fibre, vibration The highest frequency of dynamic event is less than the half of light pulse repetition rate produced by acousto-optic modulator 3.
Referring to fig. 2, a kind of phase sensitive optical time domain reflection optical fiber sensing system localization method, comprising the following steps:
Step 1: the data collecting card 9 acquires 1 time or more the corresponding beat frequency digital signal of light pulse, it is anti-based on optical time domain Principle is penetrated, beat frequency digital signal two-dimensional matrix R=[R is constructed I, j ]MxN, wherein R I, j Indicate the capture card 9 collectediIt is secondary Light pulse is corresponding in sensor fibrejBack-scattering light beat frequency digital signal value on position;In the present embodiment, data are adopted Truck 9 acquires the corresponding beat frequency digital signal of 200 light pulses, corresponds to each light pulse, includes 2360 back-scattering lights Signal value;
Step 2: using digital quadrature demodulation signal processing method, carried on the back by the beat frequency digital signal two-dimensional matrix R To scattering light phase matrix Ф;
Step 3: two column Ф of k column will be separated by back-scattering light phasing matrix Фm,jAnd Фn,jSubtract each other, wherein k desirable 1 ~ 500, in the present embodiment, k takes 10, obtains the phase difference two-dimensional matrix S that beat signal is separated by k sampled point, wherein Sm,j= Фm,jn,j, using sensor fibre position as abscissa parameter, draw each row curve of matrix S, find out phase perturbation position P1 and P2, referring to Fig. 3, these positions be both likely to be the phase perturbation of extraneous vibration event introducing, it is also possible to be since signal declines The wrong report phase perturbation for falling and introducing;
Step 4: choosing the position without phase perturbation respectively before and after phase perturbation each position P1, P2 X1 and Z1 and X2 and Z2, referring to Fig. 3, to X1 and Z1 and X2 and Z2 in the back-scattering light phasing matrix Ф respective column phase ФX1And ФZ1And ФX2And ФZ2Phase unwrapping is carried out around phase change is extended to-∞ ~+∞ range;
Step 5: drawing Ф respectivelyXAnd ФZTwo column phase versus time curves, if before phase perturbation position The phase of position changes over time identical later, adjudicates the phase perturbation as wrong report;Otherwise, it is true for adjudicating the phase perturbation Extraneous vibration event.
In order to further screen the phase perturbation introduced by extraneous indeed vibrations event and the phase introduced by signal fadeout Disturbance occurs to avoid wrong report, to emit time light pulse repetition period as abscissa parameter, draws Ф respectivelyX1And ФZ1Column Phase versus time curve, referring to fig. 4;Meanwhile Ф is drawn respectivelyX2And ФZ2Column phase versus time curve, ginseng See Fig. 5;Fig. 4 shows the phase Ф of position before and after the P1 of phase perturbation positionX1And ФZ1Change over time it is identical, then should Phase perturbation judgement is wrong report, is caused by signal fadeout;Fig. 5 shows the phase of position before and after the P2 of phase perturbation position Position ФX2And ФZ2Difference is changed over time, then it is the pressure by being applied that adjudicating the phase perturbation, which is true extraneous vibration event, Electroceramics 11 causes.
Phase sensitive optical time domain reflection optical fiber sensing system localization method principle based on phase demodulating information:
When certain section of sensor fibre 6 is disturbed by extraneous vibration, due to elasto-optical effect, the light pulse that Ф-OTDR is issued is passed It is defeated to the vibration section when will introduce light phase variation, since Pulse in Single Mode transmission speed is about 2 ' 108M/s is compared Under, optical pulse propagation passed through in the extraneous vibration section time, the light phase variable quantity approximation constant that extraneous vibration introduces, and for For difference repeats light pulse, introduced light phase will change with extraneous vibration rule.When a light pulse is completely logical When crossing extraneous vibration section, light pulse has been introduced into a light phase variation, the back-scattering light that this optical pulse is excited Light phase variation, therefore, extraneous vibration will will be re-introduced into along optical fiber reverse transfer again by the extraneous vibration section The phase mass that the back-scattering light of position is introduced into after section should be twice of extraneous vibration section introducing light phase total amount, i.e., 2, however, when light pulse is by wrong report phase perturbation position (i.e. signal fadeout section, no extraneous vibration disturbance event), it will not There is additive phase variation, there will not be when the back-scattering light excited by the light pulse after this section is again by this section additional Phase change, therefore, the backscattering light phase before and after the phase perturbation section change over time rule it is identical, can sentence Certainly the phase perturbation is wrong report point, thus, it is possible to whether be the foundation reported by mistake as judgement phase perturbation, it is outer so as to realize The accurate positionin of boundary's vibrational perturbation event.
The present invention is based on conventional Ф-OTDR hardware systems, solve Ф-OTDR optical fiber sensing system due to signal fadeout And lead to the problem of wrong report, and without complicated signal processing algorithm.

Claims (1)

1. a kind of phase sensitive optical time domain reflection optical fiber sensing system localization method,
The phase sensitive optical time domain reflection optical fiber sensing system, including narrow linewidth laser (1), 1 ' 2 fiber coupler (2), Acousto-optic modulator (3), erbium-doped fiber amplifier (4), optical fiber circulator (5), sensor fibre (6), 2 ' 2 fiber couplers (7) are put down It weighs optical detector (8), data collecting card (9), computer (10);
Wherein narrow linewidth laser (1), for generating long coherence length laser;
Narrow linewidth laser (1) is divided into two-way by 1 ' 2 fiber coupler (2), wherein optical signal passes through acousto-optic modulator all the way (3) it is modulated to the light pulse of shift frequency, passes through optical fiber circulator after carrying out optical power amplification using erbium-doped fiber amplifier (4) (5) it is input to transmission in sensor fibre (6), the back-scattering light of light pulse transmission excitation in sensor fibre (6) is along sense light Fine (6) carry out reaching optical fiber circulator (5) backwards to transmission;The another way optical signal and optical fiber circulator of 1 ' 2 fiber coupler (2) (5) back-scattering light returned is injected by two ports respectively and transmits and be concerned in 2 ' 2 fiber couplers (7), 2 ' 2 optical fiber couplings Two output ports of clutch (7) are connect with balance optical detector (8), are carried out photoelectric conversion and are obtained back-scattering light beat frequency telecommunications Number, digital beat signal, which is collected, through data collecting card (9) exports to the amplitude and phase of computer (10) calculating beat signal Position information;
Characterized by the following steps:
Step 1: the data collecting card (9) acquires 1 time or more the corresponding beat frequency digital signal of light pulse is based on optical time domain reflection Principle constructs beat frequency digital signal two-dimensional matrix R=[RI, j]MxN, wherein RI, jIndicate the capture card (9) collected i-th The corresponding back-scattering light beat frequency digital signal value on sensor fibre jth position of secondary light pulse;
Step 2: using digital quadrature demodulation signal processing method, obtained by the beat frequency digital signal two-dimensional matrix R backwards to scattered Penetrate light phase matrix Ф;
Step 3: two column Ф of k column will be separated by back-scattering light phasing matrix Фm,jAnd Фn,jSubtract each other, wherein k desirable 1~ 500, obtain the phase difference two-dimensional matrix S that beat signal is separated by k sampled point, wherein Sm,jm,jn,j, with sensor fibre Position is abscissa parameter, draws each row curve of matrix S, finds out phase perturbation position;
Step 4: choosing a position X1 and Z1 and X2 without phase perturbation respectively before and after the phase perturbation position And Z2, to X1 and Z1 and X2 and Z2 in the back-scattering light phasing matrix Ф respective column phase ФX1And ФZ1And ФX2With ФZ2Phase unwrapping is carried out around phase change is extended to-∞~+∞ range;
Step 5: drawing Ф respectivelyXAnd ФZTwo column phase versus time curves, if phase perturbation position before and it The phase of position changes over time identical afterwards, adjudicates the phase perturbation as wrong report;Otherwise, it is true extraneous for adjudicating the phase perturbation Vibration event.
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