CN106525092A - High-spatial resolution long-distance distributed optical fiber temperature strain sensing system - Google Patents
High-spatial resolution long-distance distributed optical fiber temperature strain sensing system Download PDFInfo
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- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
- G01D5/35364—Sensor working in reflection using backscattering to detect the measured quantity using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
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- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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- G01K11/322—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Brillouin scattering
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Abstract
The present invention relates to a high-spatial resolution long-distance distributed optical fiber temperature strain sensing system. The system injects an optical pulse pair of which the pulse widths have a slight difference in a sensing optical fiber based on a pulse pair secondary frequency spectrum differential technology, detects and acquires a time domain brillouin scattering signal generated by each pulse, and adopts two sets of different time window widths to extract the data separately for the spectral analysis, and carries out the secondary frequency spectrum differential operation based on the obtained four sets of brillouin frequency spectrum data, thereby obtaining the space position sensing information covered by the pulse width difference of the optical pulse pair corresponding to the secondary differential brillouin spectrums, and improving the spatial resolution. By designing the pulse widths and the pulse width difference of the optical pulse pair in the system reasonably, the action of a brillouin nonlinear effect is full, and the information within a sensing range of dozens of kilometers is acquired on the condition of keeping a higher signal-to-noise ratio of the system, so that the distributed optical fiber temperature strain sensing system of high spatial resolution (cm magnitude), long distance (greater than 50 kilometers) and high measurement precision (plus or minus 1 DEG C, plus or minus 20 Mu Epsilon) can be realized.
Description
Technical field
The present invention relates to distributed fiber optic temperature strain measurement technique field, and in particular to keeping over long distances（>50 is public
In）, high measurement accuracy（±1℃, ±20με）Performance parameter simultaneously, based on pulse to secondary Brillouin's spectral difference technology
Realize that spatial resolution reaches the distributed fiber optic temperature strain sensing system of centimetres.
Background technology
In the distributing optical fiber sensing based on spontaneous brillouin scattering（BOTDR）In system, in incident pulse light and optical fiber
Acoustical phonon occur interact after produce backward Brillouin scattering light, this scattered light relative to incident illumination frequency displacement be subject to temperature
Degree and the impact for straining, for the single-mode fiber of communication band, Brillouin's spontaneous scattering light is about relative to incident optical frequency shift
It is 1.09 ± 0.08MHz/ DEG C that 11GHz, wherein temperature cause the linear coefficient of Brillouin shift, and strain causes Brillouin shift
Linear coefficient is 0.052 ± 0.004MHz/ μ ε, using the time domain intensity of high speed detector real time record dorsad Brillouin scattering
Spectrogram, can be obtained by optical fiber temperature along the line and stress distribution information by analyzing the frequency shift amount of Brillouin scattering.BODTR
System positioning is the principle based on optical time domain reflection, and light pulse is narrower in theory, and spatial positioning accuracy is higher, and light pulse is narrow extremely
10ns correspondence spatial positioning accuracies are 10ns or so for the acoustical phonon life-span of brillouin effect participation effect in 1m, but optical fiber,
When light pulse is narrow, when 10ns is less than, the effect of Brillouin's nonlinear effect is not abundant enough so that brillouin gain drastically declines,
And finally causing sensing signal to noise ratio deterioration serious, the accuracy of measurement of temperature and strain also drastically declines.Therefore, traditional BOTDR
The system space positioning precision limit is 1m, and as the effect of Brillouin's nonlinear effect is insufficient, is divided in 1m limit spaces
In the case of resolution, the distance sensing and accuracy of measurement of system have largely been deteriorated.And in many actual engineerings
The occasion such as application, such as dam, bridge, oil pipeline, oil depot, high spatial resolution contribute to catching in time fine cracks,
The dangerous situation such as faint deformation and thermograde further carries out localization process in time.Therefore, develop BOTDR system of new generation,
Make full use of high measurement accuracy（±1℃, ±20με）Performance advantage, further solve to realize that spatial resolution reaches centimetre
Magnitude, while distance sensing can reach tens kilometers, it is highly research and the science with fine using value
And technical problem.
In current existing long-distance distributed optical fiber sensor-based system technology, the application of high spatial resolution is realized, is had
Following several ways, one is by way of fiber spiral winds so that the tested structure space of optical fiber correspondence of several meters of length away from
One meter of scope is less than on, so as to improve the sensing space resolution of tested structure, but is greatly shortened on this technological essence
The actual sensing scope of system, and cannot be suitable for strain and the deformation monitoring field of tested structure（Chinese patent
200910032861）；Two is the Brillouin optical time domain analysis instrument based on prepulsing pumping or pulse to difference（BOTDA）Technology
（Opt. Lett. 30, 370-372 (2005)；Opt. Express 16, 21616-21625 (2008)）, this technology is
Based on excited Brillouin enlarge-effect principle, the side to difference by prepulsing pump excitation acoustical phonon energy field or pulse
Formula, realizes the raising of spatial resolution, but BOTDA technologies need both-end injection laser, and needs to carry out pumping laser high-precision
The tuning of degree high duplication, therefore system structure is complicated and there is optical fiber circuit in practical engineering application, shorten measurement away from
From；Three is Brillouin light domain of dependence analytical technology（BOCDA）, this system is primarily to improve sensing space resolution and sampling
Rate and a kind of analytical technology for proposing, at present it can realize the measurement of 1cm spatial resolution on small-size object, sample rate
57Hz is reached, it is possible to achieve the kinetic measurement of strain, has been expected to replace the point sensor based on FBG（IEEE Photon.
Technol. Lett. 14, 179-181(2002)）.But the sensing scope of this technology is very limited, several meters of spaces are can only achieve
Scope, is not suitable for the safety monitoring of large scale structure building.This several technology takes different technical schemes, realizes high spatial point
The sensing of resolution, but some new problems are all introduced, there is sensing loop etc. in the distance sensing for such as shortening, be also not suitable for using
In actual heavy construction health monitoring occasion.
The content of the invention
In order to overcome the shortcoming of first technology, preferably meet and keeping over long distances（50 kilometers）, high measurement accuracy（±1
℃, ±20με）Performance parameter simultaneously, realize that spatial resolution reaches the distributed fiber optic temperature strain sensing of centimetres
System, the present invention provide one kind and realize that high spatial resolution long-distance distributed optical fiber temperature should based on secondary spectrum differential technique
Become the scheme of sensing.
The purpose of the present invention is realized at least through one of following technical scheme.
High spatial resolution long-distance distributed optical fiber temperature strain sensor-based system, the system is based on pulse to secondary spectrum
Differential technique, the pulse include to secondary spectrum differential technique implementation procedure：Two pulse widths are different and are respectivelyτ 1 Withτ 2
Impulses injection sensor fibre as direct impulse, the time domain Brillouin scattering produced in sensor fibre to each direct impulse
Signal, obtains Brillouin spectrum using FFT spectrum analysis method；When injection direct impulse width isτ 1 When, FFT numbers are extracted respectively
According to time window width it isT 1 WithT 2 Data, carry out spectrum analyses, obtain two Brillouin spectrums, respectivelyG 1 (v)WithG 2 (v)；
When injection direct impulse width isτ 2 When, two other Brillouin spectrum is respectively obtained by same processing procedureG 3 (v)WithG 4 (v)；By second order difference computing obtain equivalent high spatial position corresponding to brillouin frequency spectrum beG dd (v)=[(G 1 (v)-G 2 (v))-(G 3 (v)- G 4 (v))], in this secondary spectrum differential technique, light pulse is to pulsewidthτ 1 Withτ 2 In 20ns ~ 100ns, background of cloth
Deep nonlinear effect effect is abundant so that system obtains the letter of tens kilometers of sensing scopes in the case of keeping compared with high s/n ratio
Breath, realizes the distributed fiber optic temperature strain sensing system of high spatial resolution, long range, high measurement accuracy；The high spatial
Resolution is cm magnitudes, and the long range refers to more than 50 kilometers, and the high measurement accuracy is ± 1 DEG C, ± 20 μ ε.
Further, FFT data time window width isT 1 WithT 2 Compare pulse widthτ 1 Withτ 2 Greatly.
Further, the system includes narrow-linewidth single frequency laser instrument, the first fiber coupler, image intensifer, light pulse
Manipulator, drive module, image intensifer, fiber optical circulator, broadband frequency shifter, the second fiber coupler, sensor fibre, light electrical resistivity survey
Survey device, Signal sampling and processing unit, wherein the tail optical fiber output and the first of the first fiber coupler of narrow-linewidth single frequency laser instrument
Port is connected, and the second port of the first fiber coupler is connected with the input port of image intensifer, the output port of image intensifer
It is connected with the input port of light pulse manipulator, the driving port of light pulse manipulator is connected with drive module, light pulse modulation
The output port of device is connected with the input port of image intensifer, the output port of image intensifer and the first port of fiber optical circulator
It is connected, the second port of fiber optical circulator is connected with sensor fibre, the 3rd port of fiber optical circulator-and the second fiber coupler
Input port be connected；3rd port of the first fiber coupler is connected with the input port of broadband frequency shifter, broadband frequency shifter
Output port be connected with the input port of the second fiber coupler, broadband frequency shifter output local light and backward Brillouin dissipate
Penetrate light and optical coherence beat frequency is realized at the second fiber coupler, the output of the second fiber coupler terminates to photodetector
Optical input ports, the electricity output port of photodetector are connected to Signal sampling and processing unit, at signals collecting and place
The transducing signal collection of whole system is realized in reason unit and is processed.
Further, the light pulse manipulator be high speed electro-optical intensity modulator, responsive bandwidth >=10GHz.
Further, the drive module, the electrical pulses for producing ultrafast rise/fall edge drive light pulse modulation
Device, drive module responsive bandwidth >=10GHz, electric pulse rise and fall edge≤0.1ns can be occurred from high speed arbitrary waveform
Device.
Further, broadband frequency shifter includes fiber optical circulator, image intensifer, postpones optical fiber and fiber coupler, broadband
The input port of frequency shifter is connected with the first port of fiber optical circulator, the second port and image intensifer of fiber optical circulator it is defeated
Inbound port is connected, and the output port of image intensifer and postpones optical fiber and is connected, and the of the other end and fiber coupler of delay optical fiber
Single port is connected, and the 3rd port of fiber coupler is connected with the 3rd port of fiber optical circulator, and closure formation one is big inverse
Hour hands one-way optical fiber loop, the second port of fiber coupler as Brillouin laser frequency shifter output port namely broadband move
The output port of frequency device.
Further, broadband frequency shifter includes electro-optic intensity modulator, microwave signal generator, optical fiber circulator and optical fiber
Grating, the input port of broadband frequency shifter are connected with the first port of electro-optic intensity modulator, and microwave signal generator is connected to
The electricity control port of electro-optic intensity modulator, the first port phase of the second port and fiber optical circulator of electro-optic intensity modulator
Even, the second port of fiber optical circulator is connected with fiber grating, and the 3rd port of fiber optical circulator is used as the defeated of microwave frequency shifter
The output port of exit port namely broadband frequency shifter.
Further, described narrow-linewidth single frequency laser instrument is the LASER Light Source of continuous output, and its operation wavelength is in system
In the bandwidth range of each light scholar device and sensor fibre work, 1550nm communication bands can be adopted, laser instrument is single longitudinal mode
The high-coherence light source of operating, live width≤1MHz, output >=1mW.The phosphate high gain glass light of kHz live widths can be selected
Fibre laser, or using the semiconductor laser of MHz live widths.
Further, described light splitting fiber coupler for 1 × 2 fiber coupler, centre wavelength is 1550nm, beam splitting
Than performance and the loss determination of the light scholar's device according to upper and lower two-way.
Further, two described image intensifers, can select the Er-doped fiber of high-gain coefficient to build Er-doped fiber
Amplifier（EDFA）, or using the semiconductor optical amplifier of commercial 1550nm wave bands（SOA）.
Further, described light pulse manipulator, can select high speed electro-optical intensity modulator, in order to realize a centimetre amount
The corresponding narrow light pulse of level spatial resolution is poor, it is desirable to the responsive bandwidth >=10GHz of this light pulse manipulator.
Described fiber optical circulator is three fiber port circulators, one-way conduction, and incoming fiber optic coupling may also be employed
The method of device and isolator, plays a part of fiber optical circulator；Described sensor fibre is surveyed for temperature and stress distribution formula
The sensing unit of amount is general from the less general single mode fiber of loss；
Described broadband frequency shifter is to realize for the optical frequency of seed laser moving down about 11GHz so that the frequency difference after optical beat
In the mf band of hundreds of MHz, it is easy to the reduction of the detector and acquiring and processing device bandwidth and cost of system, Ke Yixuan
With the implementation of optical fiber Brillouin laser, or the implementation that shift frequency is modulated from microwave.
Second fiber coupler is beat frequency fiber coupler, for realizing spontaneous brillouin scattering light and broadband shift frequency
Local coherent light afterwards carries out optical coherence beat frequency, and fiber coupler is 2 × 2 fiber coupler, and centre wavelength is 1550nm,
Splitting ratio is 50:50.
Described photodetector, it is desirable to the wave-length coverage of response wave band covering seed laser light source, responsive bandwidth >=
10GHz；Described Signal sampling and processing unit, it is desirable to which the band of data acquisition equipment is wider than 500MHz, acquisition rate >=
1GS/s, signal processing take high-speed parallel processing framework.
Compared with prior art, the invention has the advantages that and technique effect：
（1）The high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system of the present invention, simple structure, compact, behaviour
Make easy, only by injecting pulsewidth slightly differentiated sensing light pulse pair, based on secondary spectrum differential ference spiral technology, you can effectively
Realize being greatly improved for spatial resolution；
（2）The high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system of the present invention, the optical pulse width of employing
For tens ns magnitudes, the effect of Brillouin's nonlinear effect is abundant, it is ensured that the high measurement accuracy of system temperature and strain and and
The measurement range of system overlength.
Description of the drawings
Fig. 1 is the schematic diagram that the present invention realizes high spatial resolution based on pulse to secondary spectrum differential technique；
Fig. 2 is the structural representation of high spatial resolution distributed optical fiber sensing system；
The structural representation one of the broadband frequency shifter of Fig. 3 present invention；
The structural representation two of the broadband frequency shifter of Fig. 4 present invention.
Specific embodiment
Below in conjunction with accompanying drawing and example to the present invention be embodied as be described further, but the enforcement and protection of the present invention
Not limited to this.
The ultimate principle of the present invention is as follows：The light pulse of pulsewidth τ is injected in BOTDR system sensor fibre, and its space is fixed
Position precision be：ΔL=cτ/2n, whereincFor light spread speed 3 × 10 in a vacuum8M/s,nIt is about 1.5 for optical fibre refractivity,
Brillouin's frequency spectrum that demodulation is obtained includes spatial positioning accuracyΔLIn the range of comprehensive heat transfer agent, obtained according to demodulation
Brillouin's frequency spectrum cannot realize the further subdivision of spatial orientation information.Pulsewidth is injected in BOTDR system sensor fibre alternately
Different light pulse τ1And τ2, by pulsewidth τ1And τ2It is arranged in the range of 20ns ~ 100ns, due to the sound of brillouin effect in optical fiber
Phonon lifetime is 10ns or so, and this pulsewidth is arranged and can ensure that Brillouin's nonlinear interaction fully, so as to ensure brillouin frequency
The certainty of measurement of shifting and longer measurement range.
As shown in figure 1, by two width different pulses（τ 1 Withτ 2 ）Sensor fibre is injected as direct impulse, to each
The time domain brillouin scattering signal that pulse is produced in sensor fibre, obtains Brillouin spectrum using FFT spectrum analysis method.When
Injecting direct impulse width isτ 1 When, extracting FFT data time window width respectively isT 1 WithT 2 Data（T 1 WithT 2 It is wider than pulse
Degreeτ 1 Withτ 2 Big 5ns or so）, spectrum analyses are carried out, two Brillouin spectrums can be obtained, respectivelyG 1 (v)WithG 2 (v).Work as injection
Direct impulse width isτ 2 When, two other Brillouin spectrum can be respectively obtained by same processing procedureG 3 (v)WithG 4 (v)。
The difference Brillouin spectrum end value obtained by second order difference computing is represented byG dd (v)=[(G 1 (v)- G 2 (v))-(G 3 (v)- G 4 (v))]。
Pulsewidthτ 1 Light pulse is injected in sensor fibre, and its spatial resolution isΔL 1 ；Pulsewidthτ 2 =τ 1 -ΔτLight pulse is noted
Enter in sensor fibre, its spatial resolution isΔL 2 =ΔL 1 -εL.SpaceΔL 2 Scope includesΔL 1 WithεLTwo parts, which is empty
Between cover difference portionεLHeat transfer agent can be by the difference brillouin frequency spectrum information in above formulaG dd (v)Obtain, in difference frequency
SpectrumG dd (v)In, common spectrum composition has been subtracted counteracting, spatial dimensionεLCorresponding heat transfer agent substantially can be embodied
Come.Due toεL=cΔτ /2n, therefore appropriate designΔτFar smaller than pulsewidthτ 1 Withτ 2 , spatial resolution can be caused to obtain pole
It is big to improve.WhenΔτWhen being arranged in the range of 0.1 ~ 1ns, the corresponding spatial resolution of system may be up to 1 ~ 10cm.In addition, comparing
Narrow light pulse is adopted compared with conventional art（<10ns）Realize the sensor-based system less than 1m spatial resolution, light pulse arteries and veins in this system
It is wideτ 1 Withτ 2 In the range of 20ns ~ 100ns, the detection light energy that light pulse is carried is very big for design, and pulsewidth is more than Brillouin in optical fiber
The acoustical phonon life-span 10ns of effect, the effect of Brillouin's nonlinear effect are abundant so that can keep higher system signal noise ratio
In the case of collection obtain tens kilometers of sensing scopes information, finally realize high spatial resolution（Cm magnitudes）, over long distances（>50
Kilometer）, high measurement accuracy（±1℃, ±20με）Distributed fiber optic temperature strain sensing system.
According to above ultimate principle, the present invention based on pulse to the high spatial resolution length of secondary spectrum differential technique away from
Structure from distributed fiber optic temperature strain sensing system is as shown in Fig. 2 the tail optical fiber output and first of narrow-linewidth single frequency laser instrument 1
First port 2-1 of fiber coupler 2 is connected, second port 2-2 of the first fiber coupler 2 and the input of image intensifer 3
Mouth is connected, and the output port of image intensifer 3 is connected with the input port of light pulse manipulator 4, the drive end of light pulse manipulator 4
Mouth is connected with drive module 5, and the output port of light pulse manipulator 4 is connected with the input port of image intensifer 6, image intensifer 6
Output port be connected with first port 7-1 of fiber optical circulator 7, second port 7-2 of fiber optical circulator 7 and sensor fibre 10
It is connected, the 3rd port 7-3 of fiber optical circulator 7 is connected with the input port 9-1 of the second fiber coupler 9；Fiber coupler 2
3rd port 2-3 is connected with the input port 8-1 of broadband frequency shifter 8, the output port 8-2 and the second optical fiber of broadband frequency shifter 8
The input port 9-2 of bonder 9 is connected, and local light realizes optical coherence with backward Brillouin scattering light at fiber coupler 9
Beat frequency, the output of fiber coupler 9 terminate to the optical input ports of photodetector 11, the electricity output of photodetector 11
Port is connected to Signal sampling and processing unit 12, and the transducing signal of whole system is realized in Signal sampling and processing unit 12
Collection and process.
Being embodied as of each device blocks is described as follows.
Narrow-linewidth single frequency laser instrument, is that BOTDR system continuously exports seed laser light source, its operation wavelength system each
In the bandwidth range of light scholar device and sensor fibre work, 1550nm communication bands are typically adopted.Narrow-linewidth single frequency laser instrument
For the high-coherence light source of single longitudinal mode operating, live width≤1MHz, output >=1mW.The high increasing of phosphate of kHz live widths can be selected
Beneficial glass fiber laser, or using the semiconductor laser of MHz live widths.
Fiber coupler, this fiber coupler for 1 × 2 fiber coupler, centre wavelength is 1550nm, is mainly used in point
Light, splitting ratio need the performance of the light scholar's device according to upper and lower two-way and loss to determine.
Image intensifer, amplifies continuous laser for front end so that the output of continuous laser reaches more than 100mW, Ke Yixuan
Erbium-doped fiber amplifier is built with the Er-doped fiber of high-gain coefficient（EDFA）, or partly leading using commercial 1550nm wave bands
Body image intensifer（SOA）.
Light pulse manipulator, it is from high speed electro-optical intensity modulator, corresponding in order to realize centimetres spatial resolution
Light pulse is poor, the responsive bandwidth >=10GHz of this light pulse manipulator.
Drive module, produces the electrical pulses on ultrafast rise/fall edge, for driving light pulse manipulator, it is desirable to drive
Responsive bandwidth >=the 10GHz of module, electric pulse rise and fall edge≤0.1ns, can select high speed arbitrary waveform generator.
Image intensifer, amplifies pulse laser for rear end so that the peak power of pulse laser reaches more than 1W, Ke Yixuan
Erbium-doped fiber amplifier is built with the Er-doped fiber of high-gain coefficient（EDFA）, or partly leading using commercial 1550nm wave bands
Body image intensifer（SOA）.
Fiber optical circulator, is three fiber port circulators, one-way conduction, may also be employed incoming fiber optic bonder and every
From the method for device, play a part of fiber optical circulator.
The optical frequency of seed laser is moved down 11GHz by broadband frequency shifter, realization so that the frequency difference after optical beat is in several
The mf band of hundred MHz, is easy to the reduction of the detector and acquiring and processing device bandwidth and cost of system, can select optical fiber
The implementation of Brillouin laser, or the implementation of shift frequency is modulated from microwave.
Fiber coupler, for realizing that spontaneous brillouin scattering light carries out optics phase with the local coherent light after the shift frequency of broadband
Dry beat frequency, fiber coupler are 2 × 2 fiber coupler, and centre wavelength is 1550nm, and splitting ratio is 50:50.
Sensor fibre, sensor fibre are the sensing units measured for temperature and stress distribution formula, it is general from loss compared with
Little general single mode fiber, such as meets ITU-T.G.652, ITU-T.G.653, ITU-T.G.655 of International Telecommunication Union's standard
Deng single-mode fiber, while in order to be applied to Practical Project environment, extraordinary overcoat can be reinforced to optical fiber carries out protection reinforcement encapsulation,
Possess which and anti-suppress the functions such as stretch-proof.
Photodetector, response carry the Brillouin scattering beat signal of heat transfer agent, it is desirable to which response wave band is covered
The wave-length coverage of seed laser light source, responsive bandwidth >=10GHz.
Information gathering and processing unit, for the data acquisition and processing (DAP) of whole system, it is desirable to the band of data acquisition equipment
500MHz is wider than, acquisition rate >=1GS/s, signal processing can take high-speed parallel processing framework.
Fig. 3 is involved in centimetres high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system of the present invention
And one of the concrete structure schematic diagram of Primary Component broadband frequency shifter 8, including：Fiber optical circulator 13, image intensifer 14, delay
Optical fiber 15, fiber coupler 16.
The input port 8-1 of broadband frequency shifter 8 is connected with first port 13-1 of fiber optical circulator 13, fiber optical circulator 13
Second port 13-2 be connected with the input port 14-1 of image intensifer 14, the output port 14-2 of image intensifer 14 and postpone light
Fine 15 are connected, and the other end for postponing optical fiber 15 is connected with first port 16-1 of fiber coupler 16, and the of fiber coupler 16
Three port 16-3 are connected with the 3rd port 13-3 of fiber optical circulator 13, and closure forms a big one-way optical fiber ring counterclockwise
Road, the output port of second port 16-2 of fiber coupler 16 as Brillouin laser frequency shifter, namely broadband frequency shifter 8
Output port 8-2.
The enforcement of each device blocks is described as follows.
Fiber optical circulator, is three fiber port circulators, one-way conduction, may also be employed incoming fiber optic bonder and every
From the method for device, play a part of fiber optical circulator.
Image intensifer, is mainly used in amplifying the pump light signals and faint brillouin scattering signal in loop, in order to not
The performance of Brillouin laser output is affected, the optical amplifier for taking optical effect length shorter is needed, 2cm length is such as can select
The Yb codoped phosphate glass optical fiber of high-gain coefficient build fiber amplifier as gain media, or from high increasing
The Er-doped fiber of beneficial coefficient builds erbium-doped fiber amplifier（EDFA）, or adopt the semiconductor light of commercial 1550nm wave bands to put
Big device（SOA）.
Postpone optical fiber, delay optical fiber herein plays offer spontaneous brillouin scattering light and the non-linear gain amplifier of Brillouin
Function, can adopt commercialization G652 models communication single-mode fiber, postpone fiber lengths be less than 50m, note this delay optical fiber
15 are slightly distinguished with the selection of sensor fibre 10, due to different batches or different preform single-mode fibers out, its
Brillouin shift slightly can be distinguished, eventually through select cause two kinds of optical fiber Brillouin shift difference control 100MHz ~
Between 1GHz.
Fiber coupler, is 1 × 2 fiber coupler, and centre wavelength is 1550nm, and splitting ratio is 10:90, wherein 10%
Port as Brillouin laser outfan.
Fig. 4 is involved in centimetres high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system of the present invention
And Primary Component broadband frequency shifter 8 concrete structure schematic diagram two, including electro-optic intensity modulator 17, microwave signal occur
Device 18, optical fiber circulator 19, fiber grating 20.
The input port 8-1 of broadband frequency shifter 8 is connected with first port 17-1 of electro-optic intensity modulator 17, microwave signal
Generator 18 is connected to the electricity control port of electro-optic intensity modulator 17, second port 17-2 of electro-optic intensity modulator 17 and
First port 19-1 of fiber optical circulator 19 is connected, and second port 19-2 of fiber optical circulator 19 is connected with fiber grating 20, light
Output ports of the 3rd port 19-3 of fine circulator 19 as microwave frequency shifter, namely the output port 8- of broadband frequency shifter 8
2。
Being embodied as of each device blocks is described as follows.
Electro-optic intensity modulator, high speed electro-optical intensity modulator, its responsive bandwidth >=10GHz can select commercialization 10GHz
LiNbO3Electro-optic intensity modulator,
Microwave signal generator, for driving electro-optic intensity modulator 17, and realizes high-frequency microwave shift frequency, therefore, this microwave is believed
The operating frequency range of number generator is in 9 ~ 14GHz, and frequency can be with fine tuning so that the local light after microwave shift frequency with from
The optical coherence beat frequency rate for sending out Brillouin scattering is controlled between 100MHz ~ 1GHz；
Fiber optical circulator, is three fiber port circulators, and one-way conduction may also be employed incoming fiber optic bonder and isolator
Method, play a part of fiber optical circulator.
Fiber grating, can adopt uniform Bragg fiber grating, be customized according to the parameter of system laser wavelength so as in
Cardiac reflex wavelength moves down the optical frequency of frequency radio-frequency component to quasi-microwave, and trickle off resonance can be by the temperature to fiber grating and should
Become tuning to correct, it is desirable to fiber grating reflectance>50%, reflectance is as high as possible to reduce filtering loss, fiber grating reflection
Bandwidth<0.17nm, the reflection bandwidth effect that more preferably can realize suppressing fundamental frequency light as narrow as possible.
Claims (7)
1. high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system, it is characterised in that the system is based on pulse pair
Secondary spectrum differential technique, the pulse include to secondary spectrum differential technique implementation procedure：Two pulse widths are different and divide
It is notτ 1 Withτ 2 Impulses injection sensor fibre as direct impulse, the time domain produced in sensor fibre to each direct impulse
Brillouin scattering signal, obtains Brillouin spectrum using FFT spectrum analysis method；When injection direct impulse width isτ 1 When, point
Indescribably taking FFT data time window width isT 1 WithT 2 Data, carry out spectrum analyses, obtain two Brillouin spectrums, respectivelyG 1 (v)WithG 2 (v)；When injection direct impulse width isτ 2 When, two other Brillouin spectrum is respectively obtained by same processing procedureG 3 (v)WithG 4 (v)；By second order difference computing obtain equivalent high spatial position corresponding to brillouin frequency spectrum beG dd (v)=[(G 1 (v)-G 2 (v))-(G 3 (v)- G 4 (v))], in this secondary spectrum differential technique, light pulse is to pulsewidthτ 1 Withτ 2 In 20ns ~ 100ns
Interior, the effect of Brillouin's nonlinear effect is abundant so that system obtains tens kilometers of sensing models in the case of keeping compared with high s/n ratio
The information enclosed, realizes the distributed fiber optic temperature strain sensing system of high spatial resolution, long range, high measurement accuracy.
2. high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system according to claim 1, its feature
It is that FFT data time window width isT 1 WithT 2 Compare pulse widthτ 1 Withτ 2 Greatly.
3. high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system according to claim 1, its feature
It is to include narrow-linewidth single frequency laser instrument（1）, the first fiber coupler（2）, image intensifer（3）, light pulse manipulator（4）, drive
Dynamic model block（5）, image intensifer（6）, fiber optical circulator（7）, broadband frequency shifter（8）, the second fiber coupler（9）, sensor fibre
（10）, photodetector（11）, Signal sampling and processing unit（12）, wherein narrow-linewidth single frequency laser instrument（1）Tail optical fiber output
With the first fiber coupler（2）First port（2-1）It is connected, the first fiber coupler（2）Second port（2-2）Put with light
Big device（3）Input port be connected, image intensifer（3）Output port and light pulse manipulator（4）Input port be connected, light
Pulse-modulator（4）Driving port and drive module（5）It is connected, light pulse manipulator（4）Output port and image intensifer
（6）Input port be connected, image intensifer（6）Output port and fiber optical circulator（7）First port（7-1）It is connected, light
Fine circulator（7）Second port（7-2）With sensor fibre（10）It is connected, fiber optical circulator（7）The 3rd port（7）-（3）With
Second fiber coupler（9）Input port（9-1）It is connected；First fiber coupler（2）The 3rd port（2-3）Move with broadband
Frequency device（8）Input port（8-1）It is connected, broadband frequency shifter（8）Output port（8-2）With the second fiber coupler（9）'s
Input port（9-2）It is connected, broadband frequency shifter（8）The local light of output is with backward Brillouin scattering light in the second fiber coupler
（9）Realize optical coherence beat frequency, the second fiber coupler in place（9）Output terminate to photodetector（11）Optical input port
Mouthful, photodetector（11）Electricity output port be connected to Signal sampling and processing unit（12）.
4. high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system according to claim 1, its feature
It is the light pulse manipulator（4）For high speed electro-optical intensity modulator, responsive bandwidth >=10GHz.
5. high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system according to claim 1, its feature
It is the drive module（5）, for producing the electrical pulses driving light pulse manipulator on ultrafast rise/fall edge（4）, drive
Module responsive bandwidth >=10GHz, electric pulse rise and fall edge≤0.1ns.
6. high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system according to claim 1, its feature
It is that broadband frequency shifter includes fiber optical circulator, image intensifer, postpones optical fiber and fiber coupler, the input of broadband frequency shifter
Mouth is connected with the first port of fiber optical circulator, and the second port of fiber optical circulator is connected with the input port of image intensifer, light
The output port of amplifier is connected with optical fiber is postponed, and the other end for postponing optical fiber is connected with the first port of fiber coupler, light
3rd port of fine bonder is connected with the 3rd port of fiber optical circulator, and closure forms a big one-way optical fiber ring counterclockwise
Road, the outfan of the second port of fiber coupler as the output port namely broadband frequency shifter of Brillouin laser frequency shifter
Mouthful.
7. high spatial resolution long-distance distributed optical fiber temperature strain sensor-based system according to claim 1, its feature
It is that broadband frequency shifter includes electro-optic intensity modulator, microwave signal generator, optical fiber circulator and fiber grating, broadband shift frequency
The input port of device is connected with the first port of electro-optic intensity modulator, and microwave signal generator is connected to electro-optic intensity modulator
Electricity control port, the second port of electro-optic intensity modulator is connected with the first port of fiber optical circulator, fiber optical circulator
Second port be connected with fiber grating, the 3rd port of fiber optical circulator output port namely broadband as microwave frequency shifter
The output port of frequency shifter.
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| CN107036734A (en) * | 2017-05-17 | 2017-08-11 | 中国地质大学（武汉） | A kind of fully distributed fiber temperature or the method for sensing and sensor of strain |
| CN107356275A (en) * | 2017-06-12 | 2017-11-17 | 中国航空工业集团公司西安飞行自动控制研究所 | A kind of method that spectral resolution is improved in optical frequency domain reflection-based optical fiber distributed sensing |
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| CN108613690A (en) * | 2018-04-18 | 2018-10-02 | 中国地质大学（武汉） | Based on differential pulse pair and the temperature of Raman amplifiction or the sensor of strain and method |
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