CN103575379B - Random site point optical fiber distributed type sonic sensor - Google Patents
Random site point optical fiber distributed type sonic sensor Download PDFInfo
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- CN103575379B CN103575379B CN201310536683.8A CN201310536683A CN103575379B CN 103575379 B CN103575379 B CN 103575379B CN 201310536683 A CN201310536683 A CN 201310536683A CN 103575379 B CN103575379 B CN 103575379B
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Abstract
A kind of random site point optical fiber distributed type sonic sensor, it comprises DFB fiber laser, acousto-optic modulator, the first image intensifer, circulator, detection optical fiber; The light signal returned by detection optical fiber exports through the C3 end of circulator and delivers to the 3rd optical filter through the second image intensifer, the 3rd optical filter output optical signal to the first photodetector; The forward entrance pulsed optical signals continuing to transmit through detection optical fiber enters the second optical filter through optoisolator, second optical filter output optical signal is to coupling mechanism and connect the first faraday rotation mirror, coupling mechanism connects the second faraday rotation mirror by phase-modulator, coupling mechanism output optical signal to the second photodetector, the electric signal that the first photodetector and the second photodetector export is to fiber-optic signal demodulating system.Adopt the scheme that the sonic position measurement device based on back of the body phase Rayleigh scattering is combined with each other by same detection optical fiber with the acoustic phase measurement mechanism based on Michelson Interferometer, without the need to time-division multiplex technology.
Description
Technical field
The present invention relates to a kind of Fibre Optical Sensor, particularly relate to a kind of random site point optical fiber distributed type sonic sensor.
Background technology
Acoustic measurement technology is developed at ocean oil and gas resource exploration, and the aspect such as microearthquake, the velocity of sound, flow of down-hole all has a wide range of applications.And traditional acoustic measurement method all exists, and device volume is large, measurement range is subject to the problems such as amplifying device restriction, and traditional acoustic measurement method can only carry out point measurement, be restricted in practice, therefore develop high performance sound wave measuring system imperative.
In prior art based on the acoustic wave sensing system research of optical fiber technology widely, for acoustic phase many employings fiber grating probe or the some sonic sensor of electric probe, this kind of sensor-based system can only the acoustic wave phase information of position near measuring sonde; For the optical fibre distribution type sensor of the many employings in sound wave position based on optical time domain reflection technology, this kind of sensor-based system can only determine the position of sound source on sensor fibre, is but difficult to learn to the information of sound source itself.To sum up generally all there is acoustic phase and to measure and sonic position measurement is difficult to the problem taken into account in existing measurement means.If will monitor the acoustic phase of random site sound source and position simultaneously, then must arrange two cover systems in measurement space, a set ofly to measure for acoustic phase, another set of for sonic position measurement, not only need laying position sensing optical fiber, also need the acoustic phase sensor of arranging in pairs or groups a large amount of in measurement range to cover whole measurement range, for demodulation acoustic phase in back-reflection light, system generally also needs to adopt complicated time-division multiplex technology, causes system cost to roll up.In prior art, when the aforementioned two kinds of measurement means of embody rule, two kinds of measurement mechanisms all need to set up respectively, be conjunction measuring sound wave position, not only need laying position sensing optical fiber, also need the acoustic phase sensor of arranging in pairs or groups a large amount of in measurement range to cover whole measurement range, the phase information of this sound wave could be obtained; For demodulation acoustic phase in back-reflection light, system generally also needs to adopt complicated time-division multiplex technology; In addition, the equipment such as corresponding light source-providing device, filter, mixer device is also all required to be two kinds of measurement mechanisms and individually arranges.
Summary of the invention
For problems of the prior art, the present invention proposes a kind of random site point optical fiber distributed type sonic sensor.
A kind of random site point optical fiber distributed type sonic sensor, it comprises distributed feedback (Distributed Feedback, DFB) fiber laser (hereinafter referred to as DFB fiber laser), receive the acousto-optic modulator that DFB fiber laser exports forward entrance light signal, receive the first image intensifer that acousto-optic modulator exports forward entrance pulsed optical signals, the forward entrance pulsed optical signals that first image intensifer exports is delivered to circulator C1 through the first optical filter and is held, and delivers to detection optical fiber from circulator C2 end;
The light signal returned by detection optical fiber exports through the C3 end of circulator and delivers to the 3rd optical filter through the second image intensifer, the 3rd optical filter output optical signal to the first photodetector;
The forward entrance pulsed optical signals continuing to transmit through detection optical fiber enters the second optical filter through optoisolator, second optical filter output optical signal is held to the P1 of 2 × 2 coupling mechanisms, the P3 end of 2 × 2 coupling mechanisms is by Fiber connection first faraday rotation mirror, the P4 end of 2 × 2 coupling mechanisms connects the second faraday rotation mirror by phase-modulator, the P2 of 2 × 2 coupling mechanisms holds output optical signal to the second photodetector, and the electric signal that the first photodetector and the second photodetector export is to fiber-optic signal demodulating system.
The concrete feature of this programme also has, and holds the fiber lengths of the first faraday rotation mirror and hold the poor s of the fiber lengths of the second faraday rotation mirror to be the integral multiple of System spatial resolution from 2 × 2 coupling mechanism P4 from 2 × 2 coupling mechanism P3.
First image intensifer refers to the first pulsed erbium doped fiber amplifier, and the second image intensifer refers to the second pulsed erbium doped fiber amplifier.
The principle of work of aforementioned structure is:
1) sound wave positional information is measured: adopt the DFB fiber laser of narrow linewidth, low noise as light source, then become forward entrance pulse through acousto-optic modulator, then after the first image intensifer and the first optical filter, incide circulator C1 hold.Circulator C2 holds and connects detection optical fiber, the backward Rayleigh scattering signal of detection optical fiber is held by circulator C3, the first photodetector is directly entered after the second image intensifer and the 3rd optical filter, after carry out the relevant treatment such as differential superposition by fiber-optic signal demodulating system after, vibration position signal can be obtained.When pulse is τ, the cycle is that the pulse laser of T enters detection optical fiber, can draw between laser pulse width τ and System spatial resolution Δ L according to distributed fiber optic sensing principle: Δ L=c τ/2n, c are light speed 3 × 10 in a vacuum
8m/s, n are that optical fibre refractivity is about 1.5.Device involved in aforementioned " measurement of sound wave positional information " processing procedure, namely forms the first distributed fiber-optic sensor device of the present invention;
2) acoustic wave phase information is measured: from the forward entrance pulsed light of detection optical fiber outgoing, through optoisolator, after second optical filter, enter by 2 × 2 coupling mechanisms, phase-modulator, first faraday rotation mirror, the arm length difference of the second faraday rotation mirror composition is the Michelson interferometer (s is the integral multiple of Δ L) of s, realize the interference of different time place forward entrance pulse signal, the light entering P3 port does not add phase-modulation and time delay is reflected (as shown in Figure 2) by the first faraday rotation mirror, the light additional phase modulation and the time delay that enter P4 port are reflected (as shown in Figure 3) by the second faraday rotation mirror, two-beam interferes as shown in Figure 4 at 2 × 2 coupling mechanism places, bring out from P2 the interference signal penetrated and have recorded acoustic phase signal unit length, export the second photodetector to, just demodulation the acoustic phase signal be recorded on interference signal can be restored by demodulating algorithm below.
Phase carrier demodulation principle:
According to the relevant principle of light, the light intensity I on the second photodetector can be expressed as:
I=A+BcosΦ(t) (1)
In formula (1): A is the average light power that interferometer exports, and B=κ A, κ≤1 is visibility of interference fringes.Φ (t) is the phase differential of interferometer.If Φ (t)=Ccos ω
0t+ φ (t), then formula (1) can be written as:
I=A+Bcos[Ccosω
0t+φ(t)] (2)
Ccos ω in formula (2)
0t is phase carrier; φ (t)=Dcos ω
st+Ψ (t), Dcos ω
st is the phase place change that sensor fibre acoustic field signal causes, and Ψ (t) is the slow change of the initial phase that environmental perturbation etc. causes.Formula (2) is obtained by Bessel functional expansion:
（3）
As shown in Figure 5, phase carrier modulation schematic diagram utilize Bessel functional expansion after interferometer output detector signal I carries out fundamental frequency, two frequencys multiplication are multiplied, in order to overcome the blanking and distortion phenomenon that signal occurs with the fluctuation of the undesired signal of outside, carried out differential multiplication cross (DCM) to two paths of signals, the signal after differential multiplication cross is converted to after differential amplification, integral operation process
B
2GHJ
1(C)J
2(C)φ(t) (4)
By φ (t)=Dcos ω
st+Ψ (t) substitutes into formula (4) to be had
B
2GHJ
1(C)J
2(C)[Dcosω
st+Ψ(t)] (5)
Visible, the signal obtained after integration contains measured signal Dcos ω
st and extraneous environmental information. the normally individual slow varying signal of the latter, and amplitude can be very large, by Hi-pass filter in addition filtering. the last output of system is
B
2GHJ
1(C)J
2(C)Dcosω
st (6)
The Dcos ω of the phase place change that sensor fibre acoustic field signal causes can be solved by formula (6)
st signal.
Device involved in aforementioned " acoustic wave phase information measurement " processing procedure, namely forms the second distributed fiber-optic sensor device of the present invention;
The invention has the beneficial effects as follows: owing to employing the first distributed fiber-optic sensor device based on backward Rayleigh scattering principle and the second distributed fiber-optic sensor device based on Michelson Interferometer principle, first distributed fiber-optic sensor device obtains the sound wave positional information in detected space by corresponding sensor fibre, second distributed fiber-optic sensor device obtains the acoustic wave phase information in detected space by corresponding sensor fibre, it is characterized in that: described first distributed fiber-optic sensor device and the second distributed fiber-optic sensor device share same detection optical fiber, the back rayleigh scattering light that first distributed fiber-optic sensor device utilizes detection optical fiber to return, and the second distributed fiber-optic sensor device utilizes the forward entrance pulsed light of detection optical fiber outgoing, stream oriented device works simultaneously, use phase carrier demodulation scheme, without the need to time division multiplex.Forward entrance signal in detection optical fiber and back of the body phase Rayleigh scattering signal all use by described invention, employing back of the body phase Rayleigh scattering light enters sonic position measurement device and forward entrance pulsed light enters acoustic phase measurement mechanism, stream oriented device structure shares the scheme of same detection optical fiber, record the position of transducing signal simultaneously, frequency, the information such as phase place, phase information is measured and is used phase carrier demodulation scheme, without the need to time-division multiplex technology, achieve monitoring while putting the position of sound wave and phase information in sensing scope, make under the prerequisite not increasing detection optical fiber length, greatly reduce original single acoustic phase sensor requirement, also reduce the technical difficulty that system realizes simultaneously, greatly reduce system cost, and make single cover system can complete monitoring to random point sound wave full detail.
Accompanying drawing explanation
Fig. 1 is system chart of the present invention; Fig. 2 is coupling mechanism P3 port optical waveform schematic diagram; Fig. 3 is coupling mechanism P4 port optical waveform schematic diagram; Fig. 4 is coupling mechanism P2 port optical waveform schematic diagram; Fig. 5 is phase carrier demodulating algorithm schematic diagram.
Embodiment
As shown in Figure 1, a kind of random site point optical fiber distributed type sonic sensor, it comprises distributed feedback (Distributed Feedback, DFB) fiber laser (hereinafter referred to as DFB fiber laser), receive the acousto-optic modulator that DFB fiber laser exports forward entrance light signal, receive the first image intensifer that acousto-optic modulator exports forward entrance pulsed optical signals, first image intensifer output forward entrance pulsed optical signals is delivered to circulator C1 through the first optical filter and is held, and delivers to detection optical fiber from circulator C2 end; The light signal returned by detection optical fiber exports through the C3 end of circulator and delivers to the 3rd optical filter through the second image intensifer, the 3rd optical filter output optical signal to the first photodetector; The forward entrance pulsed optical signals continuing to transmit through detection optical fiber enters the second optical filter through optoisolator, second optical filter output optical signal is held to the P1 of 2 × 2 coupling mechanisms, the P3 end of 2 × 2 coupling mechanisms is by Fiber connection first faraday rotation mirror, the P4 end of 2 × 2 coupling mechanisms connects the second faraday rotation mirror by phase-modulator, the P2 of 2 × 2 coupling mechanisms holds output optical signal to the second photodetector, and the electric signal that the first photodetector and the second photodetector export is to fiber-optic signal demodulating system.Hold the fiber lengths of the first faraday rotation mirror from 2 × 2 coupling mechanism P3 and hold the poor s of the fiber lengths of the second faraday rotation mirror to be the integral multiple of System spatial resolution from 2 × 2 coupling mechanism P4.First image intensifer refers to the first pulsed erbium doped fiber amplifier, and the second image intensifer refers to the second pulsed erbium doped fiber amplifier.
Embodiment 1 adopts the DFB fiber laser (RFLM-25-3-1550-1 of narrow linewidth, low noise, NP Photonics, wavelength 1550nm) as light source, then through acousto-optic modulator (ZY-AOM-SM-1550-10, Beijing Amethyst Optoelectronic Technology Limited Company) form forward entrance pulse, after the first image intensifer (PB-pluse-EDFA-M-CB-0-0-FC/APC, Beijing one hundred Te Guangtong Science and Technology Ltd.) and the first optical filter, incide circulator C1 again to hold.Circulator C2 holds and connects detection optical fiber.Detection optical fiber is ordinary optic fibre, and be 2km in the length of this hypothesis sensor fibre, laser pulse pulsewidth τ is 50ns, be then 5m according to front described spatial resolution Δ L.The backward Rayleigh scattering signal of detection optical fiber is held by circulator C3, the first photodetector (OP-APD-1550-D is directly entered after the second image intensifer and the 3rd optical filter, Tianjin Jun Feng great achievement Electro-optical Technology, INC. (US) 62 Martin Road, Concord, Massachusetts 017), in fiber-optic signal demodulating system, carry out the location algorithm of the differential superposition of acoustic signals, determine the positional information of sound wave.
From the forward entrance pulsed light of detection optical fiber tail end outgoing, through optoisolator, after second optical filter, enter by 2 × 2 coupling mechanisms, phase-modulator (KG-PM-1550-10-PS-FA, Beijing Kang Guan century Electro-optical Technology, INC. (US) 62 Martin Road, Concord, Massachusetts 017), first faraday rotation mirror (MFRM-A-1550, Beijing Hua Tuoguang grinds Science and Technology Ltd.), the Michelson interferometer of the second faraday rotation mirror composition, arm length difference s is set to measuring accuracy Δ L(5m), namely the interference of adjacent two forward entrance pulsed optical signals can be realized, bring out from P2 the interference signal penetrated and enter into the second photodetector, the demodulation of the phase information of acoustic signals is carried out in fiber-optic signal demodulating system, utilize Such phase carrier wave demodulation Scheme Solving formula I
p2=B
2gHJ
1(C) J
2(C) Dcos ω
sthe Dcos ω of the phase place change that in t, sensor fibre acoustic field signal causes
st signal, carries out the demodulation of the phase information of acoustic signals, determines sound wave frequency, phase information.To sum up by determining the position of sound wave, frequency, phase information, complete the monitoring to this random point sound wave full detail.
Claims (3)
1. a random site point optical fiber distributed type sonic sensor, it comprises DFB fiber laser, receive the acousto-optic modulator that DFB fiber laser exports forward entrance light signal, receive the first image intensifer that acousto-optic modulator exports forward entrance pulsed optical signals, first image intensifer output forward entrance pulsed optical signals is delivered to circulator C1 through the first optical filter and is held, then delivers to detection optical fiber from circulator C2 end; The light signal returned by detection optical fiber exports through the C3 end of circulator and delivers to the 3rd optical filter through the second image intensifer, the 3rd optical filter output optical signal to the first photodetector; The forward entrance pulsed optical signals continuing to transmit through detection optical fiber enters the second optical filter through optoisolator, second optical filter output optical signal is held to the P1 of 2 × 2 coupling mechanisms, the P3 end of 2 × 2 coupling mechanisms is by Fiber connection first faraday rotation mirror, the P4 end of 2 × 2 coupling mechanisms connects the second faraday rotation mirror by phase-modulator, the P2 of 2 × 2 coupling mechanisms holds output optical signal to the second photodetector, and the electric signal that the first photodetector and the second photodetector export is to fiber-optic signal demodulating system.
2., according to the random site point optical fiber distributed type sonic sensor described in claim 1, it is characterized in that holding the fiber lengths of the first faraday rotation mirror from 2 × 2 coupling mechanism P3 and holding the poor s of the fiber lengths of the second faraday rotation mirror to be the integral multiple of System spatial resolution from 2 × 2 coupling mechanism P4.
3., according to the random site point optical fiber distributed type sonic sensor described in claim 1, it is characterized in that the first image intensifer refers to the first pulsed erbium doped fiber amplifier.
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| CN106404154B (en) * | 2016-11-23 | 2022-09-20 | 山东省科学院激光研究所 | Optical fiber sound wave detection system |
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