CN205120239U - Vibration detection device based on optical frequency domain reflectometer - Google Patents
Vibration detection device based on optical frequency domain reflectometer Download PDFInfo
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- CN205120239U CN205120239U CN201520667749.1U CN201520667749U CN205120239U CN 205120239 U CN205120239 U CN 205120239U CN 201520667749 U CN201520667749 U CN 201520667749U CN 205120239 U CN205120239 U CN 205120239U
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Abstract
The utility model provides a vibration detection device based on optical frequency domain reflectometer, the device includes: modulated circuit, the optic fibre that awaits measuring, consecutive narrow linewidth fiber laser, two optical coupler, separate and be in harmonious proportion the data acquisition circuit, wherein: modulated circuit is parallelly connected to be set up between two optical coupler, and the optic fibre that awaits measuring links to each other with modulated circuit, modulated circuit includes: signal generator, mix bait optical fiber amplifier, acoustic optic modem and optical circulator, it includes to separate mediation data acquisition circuit: light bridge, data collection card, two adc and two parallelly connected balanced photoelectric detector, wherein: two parallelly connected balanced photoelectric detector's input links to each other with the light bridge, and the output is continuous with two adc's input respectively, and two adc's output links to each other with data collection card, the utility model discloses combine the optical frequency domain reflectometer technique to draw the phase information of light signal, realize long distance high sensitivity's vibration detection.
Description
Technical field
The utility model relates to a kind of technology of distributing optical fiber sensing field, specifically a kind of vibration detection device based on optical frequency domain reflectometer.
Background technology
In recent years, light reflectometry techniques can realize distributed measurement due to it, has attracted increasing concern.Vibration detection technology wherein based on optical reflectometer is also promoted.Mostly early stage vibration detection technology is based on time domain optical reflectometer (OpticalTime ?DomainReflectometer, OTDR) technology, and mostly vibration detection is to extract based on intensity to differentiate vibration signal.But the spatial resolution of OTDR technology can only reach a meter magnitude, thus limit it has high spatial resolution demand field vibration detection application at some.Extraction based on intensity is merely able to the frequency domain and the position that demodulate vibration, and oscillation intensity can not reflect.By contrast optical frequency domain reflectometer (OpticalFrequency ?DomainReflectometer, OFDR) technology can reach other spatial resolution of centimetre-sized, but detection range is limited to the coherent length of laser instrument, when measuring distance exceedes coherent length, due to the impact of laser phase noise, spatial resolution and signal to noise ratio (S/N ratio) can sharply decline.
In order to improve the intensity sensitivity of vibration detection, improve detection space resolution and detection range, Chinese scholars proposes several improvement project based on OTDR and OFDR.Such as based on the OFDR technology (Z.Ding etc. of relevant treatment, " Long ?rangevibrationsensorbasedoncorrelationanalysisofopticalf requency ?domainreflectometrysignals ", OptExpress20,28319 ?28329 (2012)) vibration detection of high spatial resolution can be realized, but its detecting distance can not exceed the coherent length of laser instrument; Based on the OTDR technology (Z.Pan etc. of phase extraction, " Phase ?sensitiveOTDRsystembasedondigitalcoherentdetection ", AsiaCommunicationsandPhotonicsConferenceandExhibition, 2011) larger sensitivity can be obtained, but its detecting distance is limited to the sensing range that signal to noise ratio (S/N ratio) can only realize several kilometers.
Through finding the retrieval of prior art, Chinese patent literature CN101650197A, day for announcing 2010.2.17, disclose a kind of optical frequency domain reflection-based optical fiber sensor system, primary structure comprises laser instrument, first fiber coupler, optical circulator, detection optical fiber, second fiber coupler, photoelectric detection unit and spectral analysis unit, the laser that laser instrument sends is divided into detection light and reference light by the first fiber coupler, detection light is incident to the first port of optical circulator, and go out to inject detection optical fiber from the second port, the rayleigh backscattering light produced in detection optical fiber is incident to optical circulator second port and from the 3rd port outgoing, the rayleigh backscattering light of outgoing and reference light to be incident in the second fiber coupler and detect by photoelectric detection unit, the signal recorded inputs to spectral analysis unit.
Chinese patent literature CN103528666A, date of publication 2014.1.22, disclose a kind of long-distance optical fiber vibration pick-up unit based on Sagnac interference and method, comprise light source, photodetector, optical circulator, 2*2 coupling mechanism and fiber delay time fine, the laser signal that described light source sends, through optical circulator, enters 2*2 coupling mechanism and is divided into two-way, one road light signal A, enter testing fiber through fiber delay time fibre, the Fresnel reflection light signal that end returns, enters 2*2 coupling mechanism; Another road light signal B, directly enters testing fiber, and the Fresnel reflection light signal that end returns, through 2*2 coupling mechanism, enters fiber delay time fibre, and when optical fiber, a fine circle, gets back to 2*2 coupling mechanism; Light signal interferes at 2*2 coupling mechanism place, and interference signal is sensed by photodetector through optical circulator.But above-mentioned technology all can produce Insertion Loss at light signal through coupling mechanism and optical circulator, and only can vibration be detected, cannot detect oscillation intensity.
Utility model content
The utility model is for prior art above shortcomings, a kind of vibration detection device based on optical frequency domain reflectometer is proposed, by the compensation of Erbium-Doped Fiber Amplifier and the modulation of acousto-optic modulator, gather vibration signal, obtained the full detail of vibration signal by balance photodetector and digital to analog converter, improve detection range and spatial resolution.
The utility model is achieved through the following technical solutions:
The utility model comprises: modulation circuit, testing fiber, the narrow cable and wide optical fiber laser be connected successively, two photo-couplers, solution mediation data acquisition circuits, wherein: modulation circuit is arranged in parallel between two photo-couplers, and testing fiber is connected with modulation circuit.
Described modulation circuit comprises: signal generator, the acousto-optic modulator, Erbium-Doped Fiber Amplifier and the optical circulator that are connected successively, wherein: signal generator is connected with acousto-optic modulator.
Described solution is in harmonious proportion data acquisition circuit and comprises: light bridge, data collecting card, two analog to digital converters and two balance photodetectors in parallel, wherein: the input end of two balance photodetectors in parallel is connected with light bridge, output terminal is connected with the input end of two analog to digital converters respectively, and the output terminal of two analog to digital converters is connected with data collecting card.
Technique effect
Compared with prior art, the utility model compensate in vibration detection process a part interfere time produce Insertion Loss, based on phase extraction obtain vibration signal Ju Li ?time three-dimensional plot and oscillation intensity information, detecting distance reaches 40km.
Accompanying drawing explanation
Fig. 1 is the utility model schematic diagram;
In figure: 1 is narrow cable and wide optical fiber laser, 2a and 2b is photo-coupler, and 3 is Erbium-Doped Fiber Amplifier, 4 is acousto-optic modulator, 5 is optical circulator, and 6 is testing fiber, and 7 is signal generator, 8 is light bridge, 9 is balance photodetector, and 10 is digital to analog converter, and 11 is data collecting card, A is reference light, and B is detection light;
Fig. 2 is the experiment effect figure of the 100 groups of data investigation in testing fiber 30km place;
In figure: (a) is intensity map, (b) is phase diagram, and (c) is differential phase figure, and (d) is single connector reflection peak;
Fig. 3 is the experiment effect figure at testing fiber 40km place;
In figure: (a) be based on phase-detection Ju Li ?time three-dimensional plot, (b) for vibration area F based on phase-detection Shi Jian ?phase curve, (c) be based on intensity detection Ju Li ?time three-dimensional plot, (d) for vibration area F based on intensity detection Shi Jian ?phase curve;
Fig. 4 is the experiment effect figure of testing fiber 30km place based on the 800Hz vibration signal of phase-detection;
In figure: (a) be based on phase-detection Ju Li ?time three-dimensional plot, the Shi Jian that (b) is vibration area ?phase curve.
Fig. 5 is the experiment effect figure that oscillation intensity is respectively 0.08g, 0.12g, 0.16g and 0.2g;
In figure: (a) for Shi Jian ?phase curve, (b) is phase diagram.
Embodiment
Below embodiment of the present utility model is elaborated; the present embodiment is implemented under premised on technical solutions of the utility model; give detailed embodiment and concrete operating process, but protection domain of the present utility model is not limited to following embodiment.
Embodiment 1
As shown in Figure 1, the present embodiment comprises: modulation circuit, testing fiber 6, narrow cable and wide optical fiber laser 1, two photo-coupler 2a and 2b be connected successively, solution mediation data acquisition circuit, wherein: modulation circuit is arranged in parallel between two photo-coupler 2a and 2b, and testing fiber 6 is connected with modulation circuit.
Described photo-coupler 2a and 2b is 3dB, 50/50 photo-coupler.
Described testing fiber 6 is the single-mode fiber (SMF) of 40km.
Described modulation circuit comprises: signal generator 7, the acousto-optic modulator 4, Erbium-Doped Fiber Amplifier 3 and the optical circulator 5 that are connected successively, wherein: signal generator 7 is connected with acousto-optic modulator 4.
Described optical circulator 5 has 3 ports 5a, 5b and 5c.
Described solution is in harmonious proportion data acquisition circuit and comprises: light bridge 8, data collecting card 11, two analog to digital converters 10 and two balance photodetectors 9 in parallel, wherein: the input end of two balance photodetectors 9 in parallel is connected with light bridge 8, the output terminal of two balance photodetectors 9 is connected with the input end of two analog to digital converters 10 respectively, and the output terminal of two analog to digital converters 10 is connected with data collecting card 11.
The light signal of described light bridge 8 to input carries out I/Q demodulation and obtains phase place.
Described data collecting card 11 be 8 ?bit data collecting card.
The present embodiment comprises the following steps:
When step 1, vibration detection, PZT is attached to 30km and the 40km place of testing fiber 6, vibration signal is loaded on PZT by signal generator 7, the oscillation intensity of PZT and the on-load voltage of signal generator 7 are directly proportional, and post accelerometer to detect the acceleration of current vibration signal on PZT simultaneously.
The wavelength that step 2, narrow cable and wide optical fiber laser 1 produce is that the light signal of 1550nm is divided into two-way by photo-coupler 2a: reference light A and detection light B; Signal generator 7 synthesizes 60MHz FM signal, is modulated to enters on the detection light B of acousto-optic modulator 4 by acousto-optic modulator 4; Detection light B after modulation is amplified by Erbium-Doped Fiber Amplifier 3 successively, the 5a port of optical circulator 5 and 5b port input testing fiber 6, and the rayleigh backscattering light that testing fiber 6 end produces enters optical circulator 5 and by 5c port input photo-coupler 2b from the 5b port of optical circulator 5; Reference light A directly enters photo-coupler 2b to be interfered with the rayleigh backscattering light of detection light B; Two-way light forms phase differential by demodulation after light bridge 8.
Step 3, the reference light A forming phase differential and detection light B are converted into electric signal by balance photodetector 9 successively, gathered by data collecting card 11 after becoming digital signal by analog to digital converter 10, the single frequency modulation on pulse collected and measured signal are carried out Coherent processing, obtain based on phase place Ju Li ?time three-dimensional plot, thus obtain the information of vibration signal.
The described exomonental repetition frequency of narrow cable and wide optical fiber laser 1 is 2kHz.
The insertion loss that described Erbium-Doped Fiber Amplifier 3 is brought for Compensation Modulation.
The frequency modulated time of described acousto-optic modulator 4 is 8 μ s, and modulation band-width is 60MHz, and simple signal rejection ratio is greater than 30dB.
The frequency sweep light frequency that described acousto-optic modulator 4 exports is 60MHz, the theoretical space resolution of corresponding 1.6m in OFDR.
The sweep velocity of described signal generator 7 is 7.5THz/s, and tuning range is 170 ~ 230MHz.
Described reference light A and the detection light phase differential that B is producing after light bridge 8 are 90 ° ± 5 °.
The bandwidth of described balance photodetector 9 is 1.6GHz.
The sampling rate of described data collecting card 11 is 2GS/s.
The time-domain signal that described data collecting card 11 collects can obtain the distributed backscatter signals of testing fiber 6 through Fourier transform.
As shown in Fig. 2 (a) He (c), at the 30km place of testing fiber 6, when there being vibration event to occur, as shown in A and D in figure, intensity pattern and differential phase pattern will be dispersed out.
As Fig. 2 (a) ?shown in (c), mutually can interfere between light signal due to each different interference point and cause interfering long or interfere and disappear mutually mutually, as shown in B, C and E in figure, interfering the region disappeared mutually, because signal to noise ratio (S/N ratio) missionary society causes the information of gained inaccurate, produce " dead band ".
As shown in Fig. 2 (d), be the connector reflection peak schematic diagram of in testing fiber 6, can obtain by figure, its spatial resolution is 3.5m.
As shown in Fig. 3 (a), (b), at the 40km place of testing fiber 6,200Hz, the vibration area F of the vibration signal of 0.08g can be detected based on phase extraction, as shown in Fig. 3 (c), (d), identical vibration event does not then extract by intensity and is detected; Namely relative to the detection based on intensity, the detection based on phase place has higher oscillation intensity sensitivity.
As shown in Figure 5, vibrate between the phase deviation caused and oscillation intensity and meet good linear relationship.
The frequency modulated time of described acousto-optic modulator 4 is 8 μ s, and effect of phase noise is less.
The investigative range of the present embodiment is 40km, and sensitivity is 0.08g.
The present embodiment, while significantly reducing phase noise, realizes the investigative range that 40km, response frequency 800Hz and intensity are the vibration signal of 0.08g.
Claims (7)
1. the vibration detection device based on optical frequency domain reflectometer, it is characterized in that, comprise: modulation circuit, testing fiber, the narrow cable and wide optical fiber laser be connected successively, two photo-couplers, solution mediation data acquisition circuits, wherein: modulation circuit is arranged in parallel between two photo-couplers, and testing fiber is connected with modulation circuit.
2. the vibration detection device based on optical frequency domain reflectometer according to claim 1, it is characterized in that, described modulation circuit comprises: signal generator, the acousto-optic modulator, Erbium-Doped Fiber Amplifier and the optical circulator that are connected successively, wherein: signal generator is connected with acousto-optic modulator.
3. the vibration detection device based on optical frequency domain reflectometer according to claim 1, it is characterized in that, described solution is in harmonious proportion data acquisition circuit and comprises: light bridge, data collecting card, two analog to digital converters and two balance photodetectors in parallel, wherein: the input end of two balance photodetectors in parallel is connected with light bridge, output terminal is connected with the input end of two analog to digital converters respectively, and the output terminal of two analog to digital converters is connected with data collecting card.
4. the vibration detection device based on optical frequency domain reflectometer according to claim 1, is characterized in that, described photo-coupler is 50/50 photo-coupler.
5. the vibration detection device based on optical frequency domain reflectometer according to claim 1, is characterized in that, the exomonental frequency of described narrow cable and wide optical fiber laser is 2kHz.
6. the vibration detection device based on optical frequency domain reflectometer according to claim 2, is characterized in that, the frequency modulated time of described acousto-optic modulator is 8 μ s, and modulation band-width is 60MHz.
7. the vibration detection device based on optical frequency domain reflectometer according to claim 3, is characterized in that, the phase differential that described light bridge produces is 90 ° ± 5 °.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105067103A (en) * | 2015-08-31 | 2015-11-18 | 上海交通大学 | Vibration detection device and method based on optical frequency domain reflectometer |
| CN107340050A (en) * | 2017-07-05 | 2017-11-10 | 成都电科光研科技有限公司 | A kind of optical fiber distribution type vibration sensor-based system and phase demodulation nonlinearity erron modification method |
| CN111579049A (en) * | 2020-05-12 | 2020-08-25 | 山东大学 | OFDR system vibration detection method based on single measurement |
| US11499849B2 (en) | 2019-06-28 | 2022-11-15 | Alcatel Submarine Networks | Method and apparatus for suppression of noise due to transmitted signal instability in a coherent fiber optical sensor system |
| US11828631B2 (en) | 2019-06-28 | 2023-11-28 | Alcatel Submarine Networks | Method and apparatus for suppression of noise due to local oscillator instability in a coherent fiber optical sensor |
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2015
- 2015-08-31 CN CN201520667749.1U patent/CN205120239U/en active Active
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105067103A (en) * | 2015-08-31 | 2015-11-18 | 上海交通大学 | Vibration detection device and method based on optical frequency domain reflectometer |
| CN105067103B (en) * | 2015-08-31 | 2018-01-02 | 上海交通大学 | Vibration detection device and its method based on optical frequency domain reflectometer |
| CN107340050A (en) * | 2017-07-05 | 2017-11-10 | 成都电科光研科技有限公司 | A kind of optical fiber distribution type vibration sensor-based system and phase demodulation nonlinearity erron modification method |
| CN107340050B (en) * | 2017-07-05 | 2023-08-04 | 成都电科光研科技有限公司 | Optical fiber distributed vibration sensing system and phase discrimination nonlinear error correction method |
| US11499849B2 (en) | 2019-06-28 | 2022-11-15 | Alcatel Submarine Networks | Method and apparatus for suppression of noise due to transmitted signal instability in a coherent fiber optical sensor system |
| US11828631B2 (en) | 2019-06-28 | 2023-11-28 | Alcatel Submarine Networks | Method and apparatus for suppression of noise due to local oscillator instability in a coherent fiber optical sensor |
| CN111579049A (en) * | 2020-05-12 | 2020-08-25 | 山东大学 | OFDR system vibration detection method based on single measurement |
| CN111579049B (en) * | 2020-05-12 | 2021-04-20 | 山东大学 | OFDR system vibration detection method based on single measurement |
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