CN103954226B - Long-distance distributed type large-measuring-range rapid response optical fiber dynamic strain sensing device - Google Patents
Long-distance distributed type large-measuring-range rapid response optical fiber dynamic strain sensing device Download PDFInfo
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Abstract
The invention provides a long-distance distributed type large-measuring-range rapid response optical fiber dynamic strain sensing device. The device comprises a phase modulator, a multi-frequency signal generating module, an intensity modulator, a microwave switch, an electric pulse generating module, a microwave signal generating module and other components. The signal generating module comprising multi-frequency components is used for modulating the phase of detection continuous light, so that multi-light-frequency components are generated in the detection continuous light, and corresponding Brillouin gain spectrum amplitudes are adjusted through controlling the amplitudes of all the light-frequency components in the detection continuous light. A Brillouin gain spectrum of a needed spectrum width and a spectrum type is obtained through splicing, and the dynamic strain measuring range is greatly enlarged under the condition that the signal-to-noise ratio and the response speed of a system are not destroyed. The frequency difference between two light beams generating a Brillouin amplification effect is fixed in the middle of a beveled edge linear region of the spliced Brillouin gain spectrum, drifting of the spliced Brillouin gain spectrum is converted into power fluctuation of the detection light, and long-distance distributed type large-measuring-range high response speed quantitative measuring on optical fiber dynamic strain and optical fiber static strain is achieved.
Description
Technical field
The present invention relates to distribution type fiber-optic dynamic strain measurement technical field is and in particular to long-distance distributed big measurement model
Enclose quick response optical fiber dynamic strain sensing device.
Background technology
By dynamic strain, the equipment causing and damage of building get more and more, and especially in earthquake district occurred frequently, vibrate and impact
Ripple etc. is very serious to the destruction in dam, bridge and house etc., and therefore the dynamic strain in the urgent need to having quick response passes
Sense network.Because optical fiber has the significant advantages such as little, high temperature resistant, the corrosion-resistant, insulation of loss, electromagnetism interference, and research is tied
The health status of structure, security, stability and integrality impact are less, and therefore substantially optical fiber sensing technology becomes structure distribution
The optimal selection of formula dynamic strain monitoring.
At present, the research realizing distribution type fiber-optic dynamic strain sensing technology mainly has several classes as follows: one is based on optical fiber
Grating dynamic strain sensing technology (refers to a.cusano, et al., sens.actuator a-phys.110,276 (2004)),
Extraneous dynamic strain or vibration cause the dynamic drift of fiber grating reflection wavelength, but build ultra-large fiber grating and dynamically should
The technical difficulty and the cost that become sensing network are very high；Two is (to be referred to based on the dynamic strain sensing technology of fiber interference structure
Tapanes edward e., us patent, 20030198425, (2003)), using interference structure, optical fiber is subject to extraneous dynamic
Strain or the phase-modulation of vibrational perturbation are converted into luminous power or the change of other parameters, but interference structure need phase-shifter and
Closed-loop control system carrys out real-time stabilization best operating point, and the stability of a system and positioning precision are poor；Three is based on Rayleigh scattering
Distributed dynamic strain sensing technology, wherein more successfully technology is that phase-sensitive optical time domain reflectometer (φ-otdr) is (detailed
See z.pan, et al., proc.of spie8421,842129 (2012)；z.qin,et al.,opt.express20,20459
(2012)), dynamic disturbances are demodulated by measuring the interference Overlay of Rayleigh scattering light in light pulse overlay area, but this side
Case perceives difficulty to gradual disturbance, and cannot realize the quantitative measurment of dynamic strain amplitude.
For continuous distributed formula sensing, Brillouin's type Distributed Optical Fiber Sensing Techniques can go up any position along the line to optical fiber
Stress deformation and temperature continuously measured, through the development of twenties years, distributed based on Brillouin's nonlinear effect
Optical fiber sensing technology advantage has obtained fully showing and taking being widely applied.But, this conventional being based on reconstructs Brillouin
The scheme of gain spectral distribution, also cannot meet the active demand of dynamic strain sensing substantially in terms of response speed.State
On border, some research groups, in conventional brillouin distributed optical fiber sensing technical foundation, targetedly explore correlation technique and come
Realize distributed dynamic strain sensing.Related exploration is concentrated mainly on following two aspects:
On the one hand it is to improve response speed.2009, a.minardo et al. proposed what a kind of frequency difference hypotenuse biasing detected
Scheme (refers to r.bernini, et al., opt.lett.34,2613 (2009)), realizes turning the drift of brillouin gain spectrum
Turn to the fluctuation of detection of optical power, thus greatly improving system response time to 98hz, but the model of this scheme dynamic strain measurement
Enclose and be less than ± 350 μ ε (deformation range ± 0.035%).2011, a.voskoboinik et al. proposed one kind no frequency sweep reconstruct cloth
In deep gain spectral scheme (referring to a.voskoboinik, et al., us patent, us20130025374a1, (2013)),
Realization need not scan and can cover sensing frequency spectrum, and therefore response speed also can reach tens hz magnitudes, but this solution technique scheme
Dynamic strain measurement scope also can only achieve ± 900 μ ε.2012, a.loayssa et al. proposed one kind and is based on Brillouin's phase shift
The distributed dynamic strain measurement scheme of analytic type (refers to j.urricelqui, et al., opt.express20,26942
(2012)), the phase place change of brillouin gain is led to realize dynamic strain sensing by demodulation strain, strain in this scheme passes
Sense scope also only reaches ± 1280 μ ε.Although these technical schemes effectively increase system and the response speed of dynamic strain are arrived
100hz, but strain sensing scope be less than ± 1000 μ ε it is impossible to meet practical application to the demand of wide-measuring range (±
More than 4000 μ ε).
The research of another aspect concentrates on expansion dynamic strain measurement scope.2011, in the biasing of aforesaid frequency difference hypotenuse
On the basis of detecting strategy, q.cui et al. adopt 6.5ns pulsewidth pulsed light as pumping pulse so that brillouin gain spectrum spectrum
Spread width and arrive 160mhz, thus strain measurement scope is expanded to ± 1600 μ ε and (refers to q.cui, et al., ieee by realization
Photon.technol.lett.23,1887 (2011)), but this technical scheme sacrifices system response time and signal noise
Than.2012, y.peled et al. adopted AWG to drive the scheme of electrooptic modulator, realizes in high-speed reconstruction cloth
The distribution (referring to y.peled, et al., opt.express20,8584 (2012)) of deep gain spectral, but need during signal transacting
The time-consuming Brillouin shift information extracting strain correlation, therefore this scheme sacrificial system when obtaining bigger strain sensing scope
Response speed, be unfavorable for dynamic strain high speed demodulation.Although these technical schemes can effectively extended dynamic strain measurement
Scope to ± 2000 μ ε, but sacrifice sensor-based system signal to noise ratio so that response speed can only achieve 10hz about it is impossible to
Meet the demand (100hz) to high response speed for the practical application.
Above-mentioned all of distribution type fiber-optic dynamic strain measurement technical scheme, including grating type optical fiber, interference structure type with
And Rayleigh scattering type, all because have be difficult to build large-scale sensing network, working state of system is unstable or is difficult to quantitative survey
The shortcomings of amount, and the demand of practical application cannot be met.And the most potential dynamic strain sensing side based on brillouin effect
In case, do not invent a kind of technology that can simultaneously take into account wide-measuring range and high response speed yet.
Content of the invention
For the shortcoming and defect overcoming current technology to exist, make full use of and continuously divided based on the distance of brillouin effect
The technical advantage of cloth measurement, further solves to realize the dynamic strain sensing of wide-measuring range and high response speed, this
The long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device of bright offer, concrete technical scheme is as follows.
Long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device, comprising: narrow-linewidth laser
Device, fiber coupler, intensity modulator, lock-in amplifier, microwave switch, electric pulse occur module, microwave signal occur module,
There is module, sense light in the first optical fiber circulator, fiber grating, the second optical fiber circulator, phase-modulator, multifrequency signal
Fibre, photodetector, signal high-speed parallel processing unit；The tail optical fiber output of narrow linewidth laser and the input of fiber coupler
Mouth is connected, and realizes for laser being divided into two-way, the first output port through fiber coupler for wherein one tunnel is defeated with intensity modulator
Inbound port is connected, and the dc voltage bias port of intensity modulator is connected with lock-in amplifier, realizes the automatically anti-of best operating point
Feedback stability contorting, the rf inputs mouth of intensity modulator is connected with the output end of microwave switch, the input of microwave switch and
Microwave signal occurs module to connect, and the input of microwave switch occurs module to be connected with electric pulse；Intensity modulator modulation obtains
High Extinction Ratio broadband shift frequency pumping pulse light exported by the output port of intensity modulator, and be connected to the first optical fiber circulator
Input port, the first optical fiber circulator also have Single port and realize filtering fiber grating be connected, the first optical fiber circulator
Output port is connected with the input port of the second optical fiber circulator, realizes pumping pulse light is injected in sensor fibre；Optical fiber
Another Lu Jingqi second output port of coupler light splitting is connected with the input port of phase-modulator, the radio frequency of phase-modulator
Input port occurs module to be connected with multifrequency signal, and the output port output of phase-modulator comprises the detection of multi-frequency composition
Continuous light is simultaneously injected in sensor fibre；Detect continuous light and pumping pulse light in sensor fibre opposite transmit after with the second light
The another port of fine circulator is connected, and the output port of the second optical fiber circulator connects the input port of photodetector, photoelectricity
The output port of detector is connected with signal high-speed parallel processing unit, realizes the demodulation of transducing signal.It can realize being distributed
Formula optical fiber dynamic strain sensor monitoring, its sensing scope is up to more than 10km, spatial resolution 1～10m, dynamic strain measurement model
Enclose up to ± 5000 μ ε, dynamic strain response speed is up to more than 100hz.
In above-mentioned long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device, adjusted by phase place
Device processed and multifrequency signal occur module construction to go out a kind of optical texture of brillouin gain splicing spectrum, using comprising multi-frequency
The multifrequency signal generation module divided acts on phase-modulator, realizes modulation and detects the phase place of continuous light so that detection connects
Produce many optical frequencies composition in continuous light, adjust each self-corresponding brillouin gain by controlling the amplitude detecting each optical frequency of continuous light
Spectral amplitude, is spliced into the brillouin gain spectrum of required spectrum width and spectral pattern, in the case of lossless system signal to noise ratio and response speed,
Realize very big extended dynamic strain measurement scope.
In above-mentioned long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device, adjusted using intensity
Device processed, lock-in amplifier, microwave switch, electric pulse occur module, microwave signal that module, the first optical fiber circulator, optical fiber occur
Grating and the second optical fiber circulator build the optical texture that pumping pulse light produces, and obtain High Extinction Ratio microwave shift frequency pumping pulse
Light, and then the frequency difference producing Brillouin amplification effect two-beam is fixed in the brillouin gain splicing spectrum hypotenuse range of linearity
Between, the drift of brillouin gain that strain is led to splicing spectrum is converted into the fluctuation of detection of optical power, achievable distributed dynamic,
The quantitative measurment of static strain.
It is further preferred that the live width of described narrow linewidth laser is less than 1mhz, it is operated in 1550nm wave band, power output
More than 20mw need to be reached.
It is further preferred that described fiber grating is the short period optical fiber grating in Prague, its reflection kernel wavelength selects fixed
In system frequency band range under the microwave broadband shift frequency of pumping light pulse；It is applied on fiber grating by temperature or strain, carry out
The tuning of reflection kernel wavelength.
It is further preferred that described fiber grating fiber grating also can be substituted by narrow band filter herein.
It is further preferred that described photodetector responsive bandwidth is higher than 100mhz.
It is further preferred that described signal high-speed parallel processing unit sampling rate is more than 100ms/s.
Described narrow linewidth laser it is desirable to live width be less than 1mhz,.
It is further preferred that described fiber coupler, it is 1 × 2 three port general single mode fiber couplers, is operated in
1550nm wave band.
It is further preferred that described intensity modulator, be electro-optic intensity modulator, be operated in 1550nm wave band it is desirable to
Modulation bandwidth is more than 11ghz.Described lock-in amplifier, is the bias voltage feedback control unit of electrooptic modulator, and feedback is rung
Answer speed khz magnitude.Described microwave switch, controls the opening and closing of microwave signal channels, and response speed is less than 1ns, every
Reach -45db from degree.There is module, frequency range 10～13ghz in described microwave signal.There is module in described electric pulse,
Pulsewidth 10ns magnitude, repetition rate 10khz magnitude.
Traditional basic structure of Brillouin optical time domain analysis instrument (botda) and principle are: be in sensor fibre two ends
Pumping pulse light is injected in opposite directions in sensor fibre by laser instrument respectively with detecting continuous light, when pumping pulse light and the continuous light of detection
Light frequency difference when being in the range of optical fiber regional area brillouin gain spectrum, excited Brillouin will be produced in this region non-linear
Enlarge-effect, energy transfer occurs between pumping pulse light and the continuous light of detection, and (for loss-type botda, energy is from continuous light
Transfer to pulsed light).It is injected into the transmission time δ t in optical fiber according to pumping pulse light, you can the positioning non-linear effect of Brillouin
The particular location (l=c × δ t/n, wherein c are light spread speed in a vacuum, and n is optical fibre refractivity) that should occur, accordingly
Realize the positioning analysis of sensing.Hair-breadth tuning is carried out within the specific limits to the frequency of continuous light, detects another from optical fiber simultaneously
Detection continuous light luminous power that one end transmits is so that it may to determine on optical fiber each segment region that energy transfer reaches institute during maximum right
The difference on the frequency answered, because the Brillouin shift in optical fiber has linear relationship with temperature, strain, shown in equation below, according to cloth
In deep gain spectral can get the temperature of each localized positions, strain information, and then realize temperature and the distributed measurement of strain:
νb=cεδε+ctδt+νbo
Wherein, νbFor Brillouin shift amount in the case of strain, thermal perturbation for the optical fiber, νboAt the beginning of in the case of undisturbed
Beginning Brillouin shift amount, cεFor the linear coefficient of strain impact Brillouin shift, δ ε is strain applied amount, ctAffect cloth for temperature
In deep frequency displacement linear coefficient, δ t is temperature applied amount.
This traditional botda scheme, is to scan reconstruct to obtain optical fiber Brillouin along the line increasing by the tuning of laser instrument
Benefit spectrum νbDistribution, and then realize temperature and the distributed measurement of strain, commonly required frequency tuning sweep limits is about
200mhz, tuning precision is about 1mhz, the tuning performance of laser instrument is required very high, the restriction of Stimulated Light device tuned speed and
Need during signal transacting to do multiple cumulative mean to improve signal to noise ratio, realize once long-distance distributed complete demodulation and survey
Amount, typically at least needs the time of a few minutes even longer, and this metering system cannot meet 100hz amount in speed completely
The rapid response to customer's need of level dynamic strain.
vb(t)=cεaεcosft+vbo
Wherein aεFor the amplitude of dynamic strain, f is the frequency of dynamic strain, as above shown in formula, this dynamic restructuring cloth
In deep gain spectral vbT scheme that () is distributed, the measurement of dynamic strain substantially difficult to realize.Therefore as institute in foregoing Background
State, have researcher to propose the scheme that a kind of frequency difference hypotenuse biasing detects, the frequency difference of the two-beam of relative transport is fixed on
In the middle of the hypotenuse range of linearity on the left of brillouin gain spectrum during undisturbed, if optical fiber local has temperature or the disturbance of strain to cause
The drift of brillouin gain spectrum, this scheme just can realize the drift of brillouin gain spectrum is converted into the ripple of detection of optical power
Dynamic (p (t)=bεThe optical power fluctuation that cosft, wherein p (t) cause for dynamic strain, bεCause the line of optical power fluctuation for strain
Property coefficient), such that it is able to avoid reconstructing brillouin gain spectrum vbT (), greatly improves system response time so that distance is distributed
Formula dynamic strain response speed can reach more than 100hz magnitude.But in view of brillouin gain spectrum limited spectrum (～
35mhz), the scope of this scheme dynamic strain measurement is less than ± 350 μ ε (deformation range ± 0.035%), and this measurement range is too little
And the Practical Project demand of the overwhelming majority cannot be met.Also have some schemes other, sacrifice response speed to a certain extent, expand
The scope of Larger Dynamic strain measurement, but temporarily also do not have a kind of technology can take into account high response speed and wide-measuring range simultaneously.
In the present invention, the long-distance distributed optical fiber dynamic strain sensing technology side based on brillouin gain splicing spectrum
Case, using comprising multifrequency signal and occur module to modulate to detect the phase place of continuous light so that producing how light in the continuous light of detection
Frequency composition, adjusts each self-corresponding brillouin gain spectrum amplitude by controlling the amplitude detecting each optical frequency of continuous light, is spliced into
Required spectrum width and the brillouin gain spectrum of spectral pattern, in the case of lossless system signal to noise ratio and response speed, realize greatly extending
Dynamic strain measurement scope；The frequency difference producing Brillouin amplification effect two-beam is fixed on brillouin gain splicing spectrum hypotenuse line
Property region in the middle of, the drift of brillouin gain splicing spectrum is converted into the fluctuation of detection of optical power, can realize distributed dynamic simultaneously
State, the quantitative measurment of static strain.
Compared with prior art, the features and advantages of the invention are:
(1) the optical fiber dynamic strain sensing with traditional scheme such as grating type optical fiber, interference structure type and Rayleigh scattering type
Network is compared, and the present invention is based on excited Brillouin nonlinear effect, does not exist and is difficult to build large-scale sensing network, system work
State labile or the shortcomings of be difficult to quantitative measurment, can effectively realize the quantitative of long-distance distributed optical fiber strain and exist in real time
Line measures at a high speed.
(2) compared with existing Brillouin's type optical fiber dynamic strain sensing technology at present, for currently brillouin distributed
The shortcoming that in dynamic strain sensing technology, measurement range and response speed cannot mutually be taken into account, the present invention adopts brillouin gain to spell
Connect the technology of spectrum, take the research think of simultaneously realizing wide-measuring range and high response speed using multiple brillouin gain splicing spectrum
Road, can effectively realize for dynamic strain measurement scope expanding to more than ± 5000 μ ε, simultaneity factor response speed can ensure completely
Reach the highest level of similar technique.
(3) be based on this technology, can effectively realize distribution type fiber-optic dynamic strain sensor monitoring, its sensing scope up to
More than 10km, spatial resolution 1～10m, dynamic strain measurement scope up to ± 5000 μ ε, dynamic strain response speed up to
More than 100hz.
Brief description
Fig. 1 is the schematic diagram with the Frequency Design detecting continuous light for the pumping pulse light of the present invention.
Fig. 2 is the principle schematic of the optical fiber Brillouin gain splicing spectrum of the present invention.
Fig. 3 is the long-distance distributed wide-measuring range high response speed light based on brillouin gain splicing spectrum of the present invention
Fine dynamic strain sensing device structure chart.
Specific embodiment
With reference to embodiment and accompanying drawing, the enforcement of the present invention is described further, but the enforcement of the present invention and protection are not
It is limited to this.
Structure design such as Fig. 3 institute of long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device
Show, the tail optical fiber output of narrow linewidth laser 1 is connected with the input port 2-1 of fiber coupler 2, and seed laser is divided into two-way,
The output port 2-2 through fiber coupler 2 for wherein one tunnel is connected with the input port 3-1 of intensity modulator 3, intensity modulator 3
Dc voltage bias port 3-2 be connected with lock-in amplifier 4, the automatic feedback realizing intensity modulator 3 best operating point is stable
Control；The rf inputs mouth 3-3 of intensity modulator 3 is connected with the output port 5-3 of microwave switch 5, the input of microwave switch 5
End 5-1 occurs module 7 to be connected with microwave signal, and the input 5-2 of microwave switch 5 occurs module 6 to be connected with electric pulse.Through intensity
The High Extinction Ratio broadband shift frequency pumping pulse light that modulator 3 modulation obtains is exported by output port 3-4 and is connected to the first optical fiber
The input port 8-1 of circulator 8, the port 8-2 of the first optical fiber circulator 8 is connected with the fiber grating 9 realizing filter action, the
The output port 8-3 of one optical fiber circulator 8 is connected with the input port 10-1 of the second optical fiber circulator 10, realizes pumping pulse
Light is injected in sensor fibre 13.Another Lu Jingqi output port 2-3 of fiber coupler 2 light splitting is defeated with phase-modulator 11
Inbound port 11-1 is connected, and the rf inputs mouth 11-2 of phase-modulator 11 occurs module 12 to be connected with multifrequency signal, comprises
The output port 11-3 of the detection phase modulated device of continuous light 11 of multi-frequency composition is injected in sensor fibre 13.Detect continuous
Light is transmitted in sensor fibre 13 in opposite directions with pumping pulse light, detect continuous optical transport after sensor fibre 13 with the second optical fiber
The port 10-2 of circulator 10 is connected, and is connected to high speed optoelectronic detection by the output port 10-3 of the second optical fiber circulator 10
The input port 14-1 of device 14, the output port 14-2 of high-speed photodetector 14 and signal high-speed parallel processing unit 15 phase
Even, realize the demodulation of transducing signal.
Hereinafter the realization to each device blocks is described as follows again:
Narrow linewidth laser 1, is the distributed wide-measuring range high response speed optical fiber based on brillouin gain splicing spectrum
The seed light source of dynamic strain sensor-based system.Due to single-mode fiber brillouin gain spectrum spectrum width be 35mhz about it is therefore desirable to pump
The live width of Pu seed light source is narrower.The light source adopting in the present invention is 1550nm wave band narrow-line width single frequency optical fiber laser, its line
A width of 2khz, laser power can reach more than 100mw (authorize patent of invention 200810220661.x with reference to the applicant,
201110280866.9,201110241520.8)；Using other kinds of commercialization narrow linewidth laser, but line can also be required
Width is less than 1mhz.
Fiber coupler 2, general single mode fiber 1550nm wave band, 1 × 2 three ports, splitting ratio needs to be implemented according to actual
When luminous power set.
Intensity modulator 3, is to realize obtaining High Extinction Ratio, the modulation device of broadband shift frequency pumping pulse light in a device,
It is operated in 1550nm wave band, 20ghz bandwidth lithium niobate electro-optic intensity modulator can be adopted.
Lock-in amplifier 4, is the bias voltage feedback control unit of electrooptic modulator so as to operate at best operating point
Place, can be using the lock-in amplifier of commercial khz magnitude response speed.
Microwave switch 5, is for controlling the opening and closing of microwave signal channels it is desirable to response speed is less than in a device
1ns, isolation reaches more than -45db, may be selected to meet the commercial microwave switch of parameter request.
There is module 6 in electric pulse, be the electric pulse for producing high-contrast, narrow spaces in a device, and triggering controls micro-
Ripple switches on and closes it is desirable to the electric pulse pulsewidth that produces reaches 10ns magnitude, and pulse recurrence frequency 10khz magnitude can
Select to meet the commercial pulse signal generator of parameter request.
There is module 7 in microwave signal, be used in a device producing microwave signal and export and be applied to electro-optic intensity modulator
Above so that the laser frequency modulated obtains broadband shift frequency, because single-mode fiber Brillouin shift is about 11ghz, therefore microwave
Signal generating module can adopt the commercial microwave signal generator of frequency range 10～13ghz, and its microwave output power needs
Drive with the intensity modulator being used and match.
First fiber optical circulator 8 and the second fiber optical circulator 10, are all three fiber port circulators, one-way conduction,
The method of incoming fiber optic coupler and isolator may also be employed, play the effect of fiber optical circulator.
Fiber grating 9, the short period optical fiber grating in Prague, its reflection kernel wavelength selects customization micro- in pumping light pulse
In frequency band range under the shift frequency of ripple broadband；In addition can be applied on fiber grating by temperature or strain, carry out a range of
The tuning of reflection kernel wavelength.Fiber grating also can be substituted by narrow band filter herein.
Phase-modulator 11, is the modulation device realizing obtaining the continuous light of detection comprising multi-frequency composition in a device,
It is operated in 1550nm wave band, 2.5ghz bandwidth lithium niobate electro-optic phase modulator can be adopted.
There is module 12 in multifrequency signal, be for producing the high frequency modulated sine wave comprising multi-frequency composition in a device
Electric signal, interval between 750～1250mhz, multi-frequency composition for its working frequency range about 1mhz and multi-frequency composition
Up to more than 500, this signal generating module is applied in electro-optic phase modulator the laser frequency shift frequency so that being modulated to quantity
Obtain multi-frequency composition afterwards, can select to meet the commercial programming function signal generator of parameter request.
Sensor fibre 13, is the basic sensing unit of whole distribution type fiber-optic dynamic strain sensor-based system, and extraneous is dynamic
Effects of strain, on sensor fibre, affects the brillouin gain spectrum of this section of optical fiber, by obtaining correlation in terminal demodulation
Strain and positional information.In such a system, can be using the communication single-mode fiber of commercial g652 model as sensor fibre.
Photodetector 14, converts optical signals to electric signal, can be higher than the high-speed light of 100mhz from responsive bandwidth
Electric explorer.
Signal high-speed parallel processing unit 15, is acquisition of information and the place of whole distribution type fiber-optic dynamic strain sensor-based system
Reason part, including signals collecting, data transfer, data high-speed processes and sensing outcome shows and preserve some, wherein, is
Acquisition high time resolution, needs to adopt high-speed data acquisition card, sampling rate need to reach more than 100ms/s, data processing
High-speed parallel processing framework can be taken, realize real-Time Signal Transfer and process.
Described narrow linewidth laser 1 becomes two-way by coupler 2 light splitting, and wherein one tunnel is modulated into through intensity modulator 3
High Extinction Ratio, broadband shift frequency pumping pulse light, retain shift frequency optical frequency composition through fiber grating 9 filtering after it, through circulator 10
Enter in sensor fibre 13；Another road enters phase-modulator 11 as detecting continuous light, synthesizes letter using multi-frequency composition
Number occur module 12 to drive phase-modulator 11, detect continuous light and be modulated into and comprise many shift frequencies optical frequency composition, using its lower frequency
In shift frequency band, the corresponding many brillouin gain spectrum splicings of many optical frequencies cut out wider more linear brillouin gain spectrum.By pumping arteries and veins
The difference on the frequency washing and detecting continuous light off is fixed in the middle of the brillouin gain splicing spectrum left side line style spectrum hypotenuse of sensor fibre 13,
When sensor fibre 13 local is subject to dynamic strain disturbance, brillouin gain splicing spectrum in optical fiber local also can occurrence dynamics be drifted about,
Fluctuation using high-speed photodetector 14 detection of optical power can demodulate dynamic strain, need not reconstruct in optical fiber cloth along the line
Deep gain spectral, realizes the distributed dynamic strain letter of wide-measuring range high response speed using signal high-speed parallel processing unit 15
Number demodulation.
In scheme, building initial brillouin gain splicing spectrum is to realize long-distance distributed wide-measuring range high response speed
The key of the optical fiber dynamic strain sensing of degree.Its general principle is as follows: is the pumping arteries and veins based on Brillouin's nonlinear effect first
Wash and detect the design of continuous light frequency off, select the frequency matching method of Brillouin's loss-type, namely detect continuous light frequency
It is in anti-Stokes frequency, as shown in figure 1, pumping pulse light frequency is vp-, driven using multi-frequency compound signal generator
Electro-optic phase modulator, the working frequency range (750～1250mhz) of design multi-frequency compound signal generator, multi-frequency become to divide it
Between interval (～1mhz) and the quantity (～500) of multi-frequency composition comprise many shift frequencies optical frequency composition so that being modulated into
Detect a few rank optical frequencies in continuous light downshift frequency band and pumping pulse light is exactly in the frequency spectrum of Brillouin's nonlinear interaction
In the range of；Meanwhile, the amplitude-controllable of every fundamental frequency signal that multi-frequency compound signal generator produces, every to realize detection light
The amplitude of single order optical frequency is adjustable.This downshift frequency band that partly controlled multifrequency phase reasonable in design is modulated is to build in optical fiber cloth
The key of deep gain splicing spectrum.
Next to that the design of optical fiber Brillouin gain splicing spectrum, as shown in Fig. 2 the every single order optical frequency detecting in continuous light is equal
A corresponding brillouin gain spectrum, many optical frequencies frequency interval (～1mhz) and each self-corresponding multiple Brillouin's frequency spectrum centre frequency
Interval holding is consistent；The amplitude of brillouin gain spectrum is determined by the Nonlinear Coupling detecting continuous light and pumping pulse light,
The amplitude of fixing pumping pulsed light, adjusts each self-corresponding brillouin gain by controlling the amplitude detecting each optical frequency of continuous light
Spectral amplitude, the corresponding many brillouin gain spectrum of many optical frequencies are non-fully overlapping on frequency domain, effectively suppress many brillouin gain spectrum it
Between weak coupling action effect, can achieve every single order brillouin gain spectrum amplitude-controllable, appropriate design each rank Brillouin increase
The centre frequency of benefit spectrum and amplitude, can achieve, on frequency domain, the brillouin gain spectrum being spliced into various spectrum widths and spectral pattern, including such as
The required linear on a large scale sideband of the sensing of dynamic strain shown in Fig. 2.
Claims (8)
1. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device is it is characterised in that include: narrow line
Wide laser instrument (1), fiber coupler (2), intensity modulator (3), lock-in amplifier (4), microwave switch (5), electric pulse occur
Module (6), microwave signal occur module (7), the first optical fiber circulator (8), fiber grating (9), the second optical fiber circulator (10),
There is module (12), sensor fibre (13), photodetector (14), signal at a high speed simultaneously in phase-modulator (11), multifrequency signal
Row processing unit (15)；The tail optical fiber output of narrow linewidth laser (1) is connected with the input port (2-1) of fiber coupler (2), real
Now laser is divided into two-way, the input of the first output port (2-2) through fiber coupler for wherein one tunnel and intensity modulator
Mouth (3-1) is connected, and the dc voltage bias port (3-2) of intensity modulator is connected with lock-in amplifier (4), realizes best operating point
Automatic feedback stability contorting, the rf inputs mouth (3-3) of intensity modulator is connected with the output end (5-3) of microwave switch,
The first input end (5-1) of microwave switch occurs module (7) to be connected with microwave signal, second input (5-2) of microwave switch
Module (6) is occurred to be connected with electric pulse；The High Extinction Ratio broadband shift frequency pumping pulse light that intensity modulator (3) modulation obtains is by strong
Output port (3-4) output of degree modulator, and it is connected to the input port (8-1) of the first optical fiber circulator, the first fiber optic loop
Shape device (8) is also had Single port (8-2) and is connected with the fiber grating (9) realizing filtering, the output port (8- of the first optical fiber circulator
3) it is connected with the input port (10-1) of the second optical fiber circulator, realize pumping pulse light is injected in sensor fibre (13)；
Another Lu Jingqi second output port (2-3) of fiber coupler (2) light splitting and input port (11-1) phase of phase-modulator
Even, the rf inputs mouth (11-2) of phase-modulator is connected with multifrequency signal generation module (12), phase-modulator defeated
Exit port (11-3) exports the continuous light of detection comprising multi-frequency composition and is injected in sensor fibre (13)；Detect continuous light with
Pumping pulse light is connected with the another port (10-2) of the second optical fiber circulator after opposite transmission in sensor fibre (13), and second
The output port (10-3) of optical fiber circulator connects the input port (14-1) of photodetector, the output port of photodetector
(14-2) it is connected with signal high-speed parallel processing unit (15), realize the demodulation of transducing signal.
2. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device as claimed in claim 1, it is special
Levy and be to occur module (12) to construct a kind of brillouin gain splicing spectrum by phase-modulator (11) and multifrequency signal
Optical texture, occurs module (12) to act on phase-modulator (11) using the multifrequency signal comprising multi-frequency composition, real
The phase place that now modulation detects continuous light produces many optical frequencies composition so that detecting in continuous light, detects each light of continuous light by controlling
The amplitude of frequency, to adjust each self-corresponding brillouin gain spectrum amplitude, is spliced into the brillouin gain spectrum of required spectrum width and spectral pattern.
3. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device as claimed in claim 1, it is special
Levy and be, using intensity modulator (3), lock-in amplifier (4), microwave switch (5), electric pulse, module (6), microwave signal occur
Occur module (7), the first optical fiber circulator (8), fiber grating (9) and the second optical fiber circulator (10) to build pumping pulse light to produce
Raw optical texture, obtains High Extinction Ratio microwave shift frequency pumping pulse light, and then will produce Brillouin amplification effect two-beam
Frequency difference is fixed in the middle of the brillouin gain splicing spectrum hypotenuse range of linearity, the drift of the brillouin gain splicing spectrum that strain is led to
It is converted into the fluctuation of detection of optical power, realize the quantitative measurment of distributed dynamic, static strain.
4. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device as claimed in claim 1, it is special
Levy and be that the live width of described narrow linewidth laser (1) is less than 1mhz.
5. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device as claimed in claim 1, it is special
Levy and be that described fiber grating (9) is the short period optical fiber grating in Prague, its reflection kernel wavelength selects customization in pump light arteries and veins
In frequency band range under the microwave broadband shift frequency of punching；It is applied on fiber grating by temperature or strain, carry out reflection kernel wavelength
Tuning.
6. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device as claimed in claim 1, it is special
Levy and be that described fiber grating (9) is substituted by narrow band filter.
7. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device as claimed in claim 1, it is special
Levy and be that described photodetector (14) responsive bandwidth is higher than 100mhz.
8. long-distance distributed wide-measuring range quick response optical fiber dynamic strain sensing device as claimed in claim 1, it is special
Levy and be that described signal high-speed parallel processing unit (15) sampling rate is more than 100ms/s.
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| GB201700984D0 (en) | 2017-01-20 | 2017-03-08 | Smart Fibres Ltd | Apparatus and method for locating a measurand anomaly along a waveguide |
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