CN105067103B - Vibration detection device and its method based on optical frequency domain reflectometer - Google Patents
Vibration detection device and its method based on optical frequency domain reflectometer Download PDFInfo
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Abstract
A kind of vibration detection device and its method based on optical frequency domain reflectometer, the device include：Modulation module, testing fiber, the narrow cable and wide optical fiber laser being sequentially connected, two photo-couplers, demodulation data acquisition module, wherein：Modulation module is arranged in parallel between two photo-couplers, and testing fiber is connected with modulation module；Modulation module includes：Signal generator, EDFA Erbium-Doped Fiber Amplifier, acousto-optic modulator and optical circulator；Demodulation data acquisition module includes：Light bridge, data collecting card, two analog-digital converters and two balance photodetectors in parallel, wherein：The input of two balance photodetectors in parallel is connected with light bridge, and input of the output end respectively with two analog-digital converters is connected, and the output end of two analog-digital converters is connected with data collecting card；The present invention combines the phase information of optical frequency domain reflectometer technology extraction optical signal, realizes vibration detection highly sensitive over long distances.
Description
Technical field
The present invention relates to a kind of technology in distributing optical fiber sensing field, is specifically that one kind is based on optical frequency domain reflectometer
Vibration detection device and its method.
Background technology
In recent years, light reflectometry techniques have attracted increasing concern because it can realize distributed measurement.Wherein
Vibration detection technology based on optical reflectometer is also promoted.The vibration detection technology of early stage is mostly to be based on time domain optical reflectometer
(Optical Time-Domain Reflectometer, OTDR) technology, and vibration detection is extracted based on intensity to divide mostly
Distinguish vibration signal.But the spatial resolution of OTDR technique can only achieve a meter magnitude, there is high-altitude some so as to limit it
Between resolution requirements field vibration detection application.Extraction based on intensity is merely able to demodulate frequency domain and the position of vibration, shakes
Fatigue resistance can not reflect.Optical frequency domain reflectometer (Optical Frequency-Domain by contrast
Reflectometer, OFDR) technology can reach the other spatial resolution of Centimeter Level, but detection range is limited to laser
Coherence length, when measurement distance exceedes coherence length, due to the influence of laser phase noise, spatial resolution and noise
Than can drastically decline.
In order to improve the intensity sensitivity of vibration detection, detection spatial resolution and detection range, domestic and foreign scholars are improved
Propose several improvement projects based on OTDR and OFDR.Such as OFDR technologies (Z.Ding etc., " Long- based on relevant treatment
range vibration sensor based on correlation analysis of optical frequency‐
Domain reflectometry signals ", Opt Express 20,28319-28329 (2012)) high spatial can be realized
The vibration detection of resolution ratio, but its detecting distance is no more than the coherence length of laser；OTDR technique based on phase extraction
(Z.Pan etc., " Phase-sensitive OTDR system based on digital coherent detection ",
Asia Communications and Photonics Conference and Exhibition, 2011) can obtain larger
Sensitivity, but its detecting distance is limited to signal to noise ratio and can only realize several kilometers of detection range.
Found by the retrieval to 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 include laser, the first fiber coupler, optical circulator,
Detection optical fiber, the second fiber coupler, photoelectric detection unit and spectral analysis unit, the laser that laser is sent is by the first optical fiber
Coupler is divided into detection light and reference light, and detection light is incident to the first port of optical circulator, and is emitted and enters from second port
Detection optical fiber, caused rayleigh backscattering light is incident to optical circulator second port and gone out from the 3rd port in detection optical fiber
To penetrate, rayleigh backscattering light and the reference light of outgoing are incident in the second fiber coupler and detected by photoelectric detection unit,
The signal measured is inputted to spectral analysis unit.
Chinese patent literature CN103528666A, date of publication 2014.1.22, disclose it is a kind of based on Sagnac interference
Long-distance optical fiber vibration detection means and method, including light source, photodetector, optical circulator, 2*2 couplers and fiber delay time
Fibre, the laser signal that the light source is sent pass through optical circulator, are divided into two-way into 2*2 couplers, all the way optical signal A, pass through
Fiber delay time fibre enters testing fiber, the Fresnel reflection optical signal that end returns, into 2*2 couplers；Another way optical signal
B, testing fiber is directly entered, the Fresnel reflection optical signal that end returns is fine into fiber delay time through 2*2 couplers, through light
Fibre one encloses when fine, returns to 2*2 couplers；Optical signal interferes at 2*2 couplers, and interference signal is by optical circulator by light
Electric explorer senses.But above-mentioned technology can produce Insertion Loss when optical signal passes through coupler and optical circulator, and be only capable of detecting
To vibration, oscillation intensity can not be detected.
The content of the invention
The present invention is directed to deficiencies of the prior art, proposes a kind of vibration detection dress based on optical frequency domain reflectometer
Put and its method, pass through the compensation of EDFA Erbium-Doped Fiber Amplifier and the modulation of acousto-optic modulator, vibration signal is gathered, by balancing light
Electric explorer and digital analog converter obtain the full detail of vibration signal, improve detection range and spatial resolution.
The present invention is achieved by the following technical solutions：
The present invention relates to a kind of vibration detection device based on optical frequency domain reflectometer, including：Modulation module, testing fiber,
Narrow cable and wide optical fiber laser, two photo-couplers, the demodulation data acquisition module being sequentially connected, wherein：Modulation module is in parallel
It is arranged between two photo-couplers, testing fiber is connected with modulation module.
Described modulation module includes：Signal generator, the acousto-optic modulator being sequentially connected, EDFA Erbium-Doped Fiber Amplifier and light
Circulator, wherein：Signal generator is connected with acousto-optic modulator.
Described demodulation data acquisition module includes：Light bridge, data collecting card, two analog-digital converters and two parallel connections
Balance photodetector, wherein：The input of two balance photodetectors in parallel is connected with light bridge, output end respectively with
The input of two analog-digital converters is connected, and the output end of two analog-digital converters is connected with data collecting card.
The present invention relates to the method for detecting vibration of said apparatus, comprise the following steps：
Step 1, piezoelectric ceramics (PZT) is attached to testing fiber a bit, vibration signal is loaded into by signal generator
On PZT, while accelerometer is posted to detect the acceleration of current vibration signal on PZT.
Optical signal is divided into two-way by photo-coupler caused by step 2, narrow cable and wide optical fiber laser, all the way detect light B according to
It is secondary that testing fiber is inputted by the acousto-optic modulator through signal generator frequency sweep, EDFA Erbium-Doped Fiber Amplifier, optical circulator, treat light-metering
Rayleigh backscattering light caused by fine end enters optical circulator and inputs another photo-coupler；Another way reference light A is direct
Interfered into the photo-coupler with detecting light B rayleigh backscattering light；Two-way light after interference after light bridge by demodulating
Form phase difference.
Step 3, the two ways of optical signals of formation phase difference pass sequentially through balance photodetector and are converted into electric signal, pass through mould
Number converter is gathered after being changed into data signal by data collecting card, obtains the information of vibration signal.
Technique effect
Compared with prior art, the present invention compensate for Insertion Loss caused by part interference, base during vibration detection
The distance verses time graphics of vibration signal is obtained in phase extraction and oscillation intensity information, detecting distance reach 40km.
Brief description of the drawings
Fig. 1 is schematic diagram of the present invention；
In figure：1 is narrow cable and wide optical fiber laser, and 2a and 2b are photo-coupler, and 3 be EDFA Erbium-Doped Fiber Amplifier, and 4 be that acousto-optic is adjusted
Device processed, 5 be optical circulator, and 6 be testing fiber, and 7 be signal generator, and 8 be light bridge, and 9 be balance photodetector, and 10 be digital-to-analogue
Converter, 11 be data collecting card, and A is reference light, and B is detection light；
Fig. 2 is the experiment effect figure of 100 groups of data investigations at testing fiber 30km；
In figure：(a) it 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；
In figure：(a) it is the distance verses time graphics based on phase-detection, (b) is vibration area F based on phase-detection
When m- phase curve, (c) is the distance verses time graphics based on intensity detection, and (d) is vibration area F based on intensity detection
When m- phase curve；
Fig. 4 is the experiment effect figure of the 800Hz vibration signals based on phase-detection at testing fiber 30km；
In figure：(a) it is the distance verses time graphics based on phase-detection, (b) is the when m- phase curve of vibration area.
Fig. 5 is the experiment effect figure that oscillation intensity is respectively 0.08g, 0.12g, 0.16g and 0.2g；
In figure：(a) m- phase curve when being, (b) is phase diagram.
Embodiment
Embodiments of the invention are elaborated below, the present embodiment is carried out lower premised on technical solution of the present invention
Implement, give detailed embodiment and specific operating process, but protection scope of the present invention is not limited to following implementation
Example.
Embodiment 1
As shown in figure 1, the present embodiment includes：Modulation module, testing fiber 6, the narrow cable and wide optical fiber laser being sequentially connected
1st, two photo-coupler 2a and 2b, demodulation data acquisition modules, wherein：Modulation module is arranged in parallel in two photo-coupler 2a
Between 2b, testing fiber 6 is connected with modulation module.
Described photo-coupler 2a and 2b is 3dB, 50/50 photo-coupler.
Described testing fiber 6 is 40km single-mode fiber (SMF).
Described modulation module includes：Signal generator 7, the acousto-optic modulator 4 being sequentially connected, EDFA Erbium-Doped Fiber Amplifier 3
With optical circulator 5, wherein：Signal generator 7 is connected with acousto-optic modulator 4.
Described optical circulator 5 has 3 ports 5a, 5b and 5c.
Described demodulation data acquisition module includes：11, two light bridge 8, data collecting card analog-digital converters 10 and two
Individual balance photodetector 9 in parallel, wherein：The input of two balance photodetectors 9 in parallel is connected with light bridge 8, and two
Input of the output end of individual balance photodetector 9 respectively with two analog-digital converters 10 is connected, two analog-digital converters 10
Output end be connected with data collecting card 11.
Described light bridge 8 carries out I/Q demodulation to the optical signal of input and obtains phase.
Described data collecting card 11 is 8-bit data collecting cards.
The present embodiment comprises the following steps：
When step 1, vibration detection, PZT is attached at the 30km and 40km of testing fiber 6, vibration signal is sent out by signal
Raw device 7 is loaded on PZT, and PZT oscillation intensity and the on-load voltage of signal generator 7 are directly proportional, while is posted and added on PZT
Speedometer is to detect the acceleration of current vibration signal.
Wavelength caused by step 2, narrow cable and wide optical fiber laser 1 is that 1550nm optical signal is divided into two by photo-coupler 2a
Road：Reference light A and detection light B；Signal generator 7 synthesizes 60MHz FM signals, is modulated to by acousto-optic modulator 4 into entering tone
On the detection light B of optical modulator 4；Detection light B after modulation pass sequentially through EDFA Erbium-Doped Fiber Amplifier 3 amplify, the 5a of optical circulator 5
Port and 5b ports input testing fiber 6, rayleigh backscattering light caused by the end of testing fiber 6 is from the 5b ends of optical circulator 5
Mouth, which enters optical circulator 5 and passes through 5c ports, inputs photo-coupler 2b；Reference light A is directly entered photo-coupler 2b and detection light B
Rayleigh backscattering light interfered；Two-way light forms phase difference by being demodulated after light bridge 8.
Step 3, the reference light A for forming phase difference and detection light B pass sequentially through balance photodetector 9 and are converted into telecommunications
Number, be changed into being gathered by data collecting card 11 after data signal by analog-digital converter 10, by the single frequency modulation on pulse collected and
Measured signal carries out Coherent processing, the distance verses time graphics based on phase is obtained, so as to obtain the information of vibration signal.
Described 1 exomonental repetition rate of narrow cable and wide optical fiber laser is 2kHz.
Described EDFA Erbium-Doped Fiber Amplifier 3 is used for the insertion loss that Compensation Modulation is brought.
The frequency modulated time of described acousto-optic modulator 4 is 8 μ s, modulation bandwidth 60MHz, and simple signal rejection ratio is more than
30dB。
The frequency sweep light frequency that described acousto-optic modulator 4 exports is 60MHz, and 1.6m theoretical space point is corresponded in OFDR
Resolution.
The sweep velocity of described signal generator 7 is 7.5THz/s, and tuning range is 170~230MHz.
Described reference light A and detection light B after light bridge 8 caused phase difference be 90 ° ± 5 °.
The a width of 1.6GHz of band of described balance photodetector 9.
The sample rate of described data collecting card 11 is 2GS/s.
The time-domain signal that described data collecting card 11 collects can obtain point of testing fiber 6 by Fourier transform
Cloth backscatter signals.
As shown in Fig. 2 (a) and (c), at the 30km of testing fiber 6, when there is vibration event generation, such as A and D institutes in figure
Show, intensity pattern and differential phase pattern will diverge.
As shown in Fig. 2 (a)-(c), cause to interfere phase due to that can interfere between the optical signal of each different interference points
Long or interference cancellation, as shown in B, C and E in figure, in the region of interference cancellation, because poor signal to noise can cause the information of gained not
Accurately, produce " dead band ".
It is a connector reflection peak schematic diagram in testing fiber 6 as shown in Fig. 2 (d), by that can be obtained in figure, its space
Resolution ratio is 3.5m.
As shown in Fig. 3 (a), (b), at the 40km of testing fiber 6, the vibration area F of 200Hz, 0.08g vibration signal
It can be detected based on phase extraction, as shown in Fig. 3 (c), (d), identical vibration event can not then be extracted by intensity and is detected
Arrive；I.e. relative to the detection based on intensity, the detection based on phase has higher oscillation intensity sensitivity.
As shown in figure 5, meet preferable linear relationship between phase deviation and oscillation intensity caused by vibration.
The frequency modulated time of described acousto-optic modulator 4 is 8 μ s, and effect of phase noise is smaller.
The investigative range of the present embodiment is 40km, sensitivity 0.08g.
For the present embodiment while phase noise is greatly decreased, it is 0.08g to realize 40km, response frequency 800Hz and intensity
Vibration signal investigative range.
Claims (6)
- A kind of 1. vibration detection device based on optical frequency domain reflectometer, it is characterised in that including：Modulation module, testing fiber, according to Secondary connected narrow cable and wide optical fiber laser, two photo-couplers, demodulation data acquisition module, wherein：Modulation module parallel connection is set It is placed between two photo-couplers, testing fiber is connected with modulation module；Described modulation module includes：Signal generator, the acousto-optic modulator being sequentially connected, EDFA Erbium-Doped Fiber Amplifier and ring of light shape Device, wherein：Signal generator is connected with acousto-optic modulator；Described demodulation data acquisition module includes：Light bridge, data collecting card, two analog-digital converters and two are in parallel flat Weigh photodetector, wherein：The input of two balance photodetectors in parallel is connected with light bridge, output end respectively with two The input of analog-digital converter is connected, and the output end of two analog-digital converters is connected with data collecting card.
- 2. vibration detection device according to claim 1, it is characterized in that, described photo-coupler is 50/50 photo-coupler.
- 3. vibration detection device according to claim 1, it is characterized in that, the transmitting pulse of described narrow cable and wide optical fiber laser Frequency be 2kHz.
- 4. vibration detection device according to claim 1, it is characterized in that, the frequency modulated time of described acousto-optic modulator is 8 μ S, modulation bandwidth 60MHz.
- 5. vibration detection device according to claim 1, it is characterized in that, phase difference caused by described light bridge is 90 ° ± 5°。
- A kind of 6. method for detecting vibration based on vibration detection device described in any of the above-described claim, it is characterised in that including Following steps：Step 1, PZT is attached to testing fiber a bit, vibration signal is loaded on PZT by signal generator, while in PZT On post accelerometer to detect the acceleration of current vibration signal；Optical signal is divided into two-way by photo-coupler caused by step 2, narrow cable and wide optical fiber laser, detects light B all the way and leads to successively Cross the acousto-optic modulator through signal generator frequency sweep, EDFA Erbium-Doped Fiber Amplifier, optical circulator input testing fiber, testing fiber end Rayleigh backscattering light caused by end enters optical circulator and inputs another photo-coupler；Another way reference light A is directly entered The photo-coupler is interfered with detecting light B rayleigh backscattering light；Two-way light after interference is formed by being demodulated after light bridge Phase difference；Step 3, the two ways of optical signals of formation phase difference pass sequentially through balance photodetector and are converted into electric signal, pass through modulus and turn Parallel operation is gathered after being changed into data signal by data collecting card, obtains vibration signal information.
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