CN104776871B - Optical fiber Brillouin distributed measurement light path, apparatus and method - Google Patents
Optical fiber Brillouin distributed measurement light path, apparatus and method Download PDFInfo
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Abstract
The present embodiments relate to a kind of optical fiber Brillouin distributed measurement light path, apparatus and method, wherein, optical path includes the first coupler, the second coupler, the 3rd coupler, first annular device, the first optical channel, the second optical channel, sensor fibre, the 3rd optical channel and the 4th optical channel.One end input pulse light, the other end of sensor fibre input continuous light to excite Brillouin scattering, so strengthen anti Stokes components, if the intensity of anti-Stokes light is sufficiently strong, so comparatively the intensity of stokes light is then weaker, it can be ignored, the contradiction of input optical pulse luminosity and spatial resolution had so both been solved, can avoid using high-precision filter again.
Description
Technical field
The invention belongs to technical field of optical fiber sensing, more particularly to a kind of optical fiber Brillouin distributed measurement light path,
Apparatus and method.
Background technology
Optical fiber sensing technology is a kind of new sensing technology, with measurement accuracy height, electromagnetism interference and distributed survey
The advantages of amount, in the industry heavy construction structure such as electric power, building, oil and water conservancy health status on-line monitoring and localization of fault
In have a extensive future.At present, the distributed optical fiber sensing system based on Brillouin scattering is broadly divided into three kinds from scheme：Base
Passed in the optical fiber of Brillouin light Time Domain Reflectometry (Brillouin Optical Time Domain Reflectometry, BOTDR)
Sense technology, based on Brillouin light frequency-domain analysis (Brillouin Optical FrequencyDomain Analysis, BOFDA)
Optical fiber sensing technology and based on Brillouin optical time domain analysis (BrillouinOptical Time Domain Analysis,
BOTDA optical fiber sensing technology).Wherein, BOTDR measurements is spontaneous brillouin scattering signal, and because spontaneous Brillouin dissipates
Signal is penetrated relatively weak, so detection difficulty is larger.And in BOFDA e measurement technology, it is long to there is required time of measuring, to surveying
Measure optical fiber local environment and require high, and the shortcomings of signal detection apparatus costliness.
The content of the invention
In view of the shortcomings of the prior art, it is an object of the invention to provide a kind of optical fiber Brillouin distributed measurement light path,
Apparatus and method, to solve the technological deficiency that existing fiber measurement accuracy is not high.
Therefore, embodiment of the present invention provide a kind of optical fiber Brillouin distributed measurement light path, including the first coupler,
Second coupler, the 3rd coupler, first annular device, the first optical channel, the second optical channel, sensor fibre, the 3rd optical channel and
4th optical channel,
The input and the second optical channel of two output ports of first coupler respectively with first optical channel
Input connection, the output end of first optical channel is connected with the input port of the second coupler, second coupler
An output port be connected through the first Polarization Controller with an input port of the 3rd coupler, another output port
It is connected through the 3rd optical channel with one end of the sensor fibre；
The output end of second optical channel is connected with the first port of the first annular device, the first annular device
Second port is connected with the other end of the sensor fibre, and the 3rd port of the first annular device is connected with grating, described
4th port of first annular device is connected with the input of the 4th optical channel；The output end and the described 3rd of 4th optical channel
The input port connection of coupler.
As a kind of perferred technical scheme, first optical channel includes the second polarization to output end successively from input
Controller, phase type electrooptic modulator.
As a kind of perferred technical scheme, second optical channel includes the 3rd polarization to output end successively from input
Controller, intensity type electrooptic modulator, erbium-doped fiber amplifier, the second circulator, optoisolator, the of second circulator
Single port is connected with the output end of the erbium-doped fiber amplifier, and second port is connected with grating, the 3rd port and the light every
Input port from device is connected.
As a kind of perferred technical scheme, the 3rd optical channel includes light filtering to output end successively from input
Device, optoisolator and scrambler.
As a kind of perferred technical scheme, the 4th optical channel includes Er-doped fiber successively from input to output end
Amplifier, the 3rd circulator, dual-pass Mach-Zehnder interferometer, first port and the Er-doped fiber of the 3rd circulator
The output end connection of amplifier, second port is connected with grating, and the 3rd port is defeated with the dual-pass Mach-Zehnder interferometer
Inbound port is connected.
Embodiment of the present invention additionally provides a kind of optical fiber Brillouin distributed measurement device, including the inspection of laser, photoelectricity
Survey device and digital sampling and processing, in addition to above-mentioned optical fiber Brillouin distributed measurement light path, the laser with it is described
The input port connection of first coupler, the photoelectric detector is connected with the data acquisition and procession module, and the described 3rd
One output port of coupler is connected with the photoelectric detector.
The embodiment of the present invention provides a kind of optical fiber Brillouin distributed measurement method again, including：
The laser that laser is sent is divided into two ways of optical signals, wherein optical signal modulation is into pulsed light all the way, in addition all the way
Optical signal modulation is into the continuous light with Brillouin shift frequency；
The continuous light is divided into the continuous optical signal of the first pulse and the second continuous optical signal；
Described first continuous optical signal and the pulsed light are produced into stimulated Brillouin scattering in sensor fibre, cloth is produced
In deep scattered light；
The Brillouin scattering is interfered with the described second continuous optical signal, surveyed after Data Analysis Services
Measure result.
As a kind of perferred technical scheme, the first pulse luminous intensity accounts for the 95% of the continuous light luminous intensity.
As a kind of perferred technical scheme, it is described " to enter the Brillouin scattering with the described second continuous optical signal
Row interference, measurement result is obtained after Data Analysis Services " the step of include：
Result of interference is carried out with the described second continuous optical signal according to the Brillouin scattering, Brillouin shift is obtained；
Temperature is calculated according to following formula：
νB(T, 0)=vB(T0,0)[1+1.18*10-4ΔT]
Wherein：νBWhen (T, 0) represents strain stress for 0 and constant holding, the relation that Brillouin scattering optical frequency shift is varied with temperature
Formula；T0For reference temperature, 20 DEG C are typically taken；vB(T0, 0) represent temperature be 20 DEG C, strain stress be 0 when Brillouin scattering frequency displacement
Amount；Δ T=T-T0For the temperature variation relative to reference temperature.
As a kind of perferred technical scheme, it is described " to enter the Brillouin scattering with the described second continuous optical signal
Row interference, measurement result is obtained after Data Analysis Services " the step of include：
Result of interference is carried out with the described second continuous optical signal according to the Brillouin scattering, Brillouin shift is obtained；
Calculated and strained according to following formula：
νB(T0, ε) and=vB(T0,0)(1+4.48ε)
Wherein：νB(T0, ε) expression temperature be reference temperature (T0=20 DEG C) when, the pass that Brillouin shift changes with stress ε
It is formula；vB(T0, 0) expression temperature be reference temperature (T0=20 DEG C), stress ε be 0 when Brillouin shift amount.
Compared with prior art, embodiment of the present invention has the advantages that：
1. the optical path, apparatus and method are inputted using single light source, Brillouin is excited to dissipate using double-width grinding laser
Penetrate, so that measuring system is simplified and measurement accuracy is higher；
2. the separation of stimulated Brillouin scattering and Rayleigh scattering is realized using dual-pass Mach-Zehnder interferometer so that point
From effect more preferably, measurement accuracy is improved；
3. one end input pulse light of sensor fibre, the other end input continuous light to excite Brillouin scattering, so strengthen
Anti Stokes components, if the intensity of anti-Stokes light is sufficiently strong, then comparatively the intensity of stokes light is then
It is weaker, it can be ignored, so both solve the contradiction of input optical pulse luminosity and spatial resolution, can avoid again using height
The filter of precision；
4. embodiment of the present invention no longer needs the difference interference method of additional reference light to detect Brillouin shift, reference
Light is modulated the continuous signal for producing about 11GHZ by electrooptic modulator, with treated detection light after filtering in photoelectricity
Sensor carries out difference interference, further simplify system.
Brief description of the drawings
Fig. 1 is the structural representation for the optical fiber Brillouin distributed measurement light path that embodiment of the present invention is provided；
Fig. 2 is the structure chart that Fig. 1 shows dual-pass Mach-Zehnder interferometer in embodiment；
Fig. 3 is the structural representation for the optical fiber Brillouin distributed measurement device that embodiment of the present invention is provided；
Fig. 4 is the flow chart for the optical fiber Brillouin distributed measurement method that embodiment of the present invention is provided；
Fig. 5 is the Brillouin's backscatter intensity-frequency shift amount-distance and temperature change when not applying temperature and strain
Graph of a relation；
Fig. 6 is excited Brillouin backscatter intensity-frequency displacement when changing a temperature at the 3000m distances of sensor fibre
The graph of a relation of amount-distance and temperature；
Fig. 7 is excited Brillouin backscatter intensity-frequency when applying a microstress at the 3000m distances of sensor fibre
The graph of a relation of shifting amount-distance and temperature；
In figure：
100：Optical fiber Brillouin distributed measurement light path；111：First coupler；112：Second coupler；113：First is inclined
Shake controller；114：3rd coupler；115：First annular device；116：Grating；117：Sensor fibre；120：First optical channel；
121：Second Polarization Controller；122：Phase type electrooptic modulator；130：Second optical channel；131：3rd Polarization Controller；
132：Intensity type electrooptic modulator；133：Erbium-doped fiber amplifier；134：Second circulator；135：Optoisolator；140：3rd
Optical channel；141：Optical filter；142：Optoisolator；143：Scrambler；150：4th optical channel；151：Erbium-doped fiber amplifier
Device；152：3rd circulator；153：Dual-pass Mach-Zehnder interferometer；1531：Coupler；1532：Piezoelectric ceramics；1533：Coupling
Clutch；1534：Optical fiber；1535：Optoisolator；1536：DC voltage controller；200：Laser；300：Photoelectric detector；
400：Data acquisition and procession module.
Embodiment
Below in conjunction with the accompanying drawings, embodiments of the present invention are described further.
Referring to Fig. 1, Fig. 1 is the structural representation for the optical fiber Brillouin distributed measurement light path that embodiment of the present invention is provided
Figure.Optical fiber Brillouin distributed measurement light path 100 shown in Fig. 1 includes the first coupler 111, the second coupler 112, the 3rd coupling
Clutch 114, first annular device 115, the first optical channel 120, the second optical channel 130, sensor fibre 117, the and of the 3rd optical channel 140
4th optical channel 150.
Wherein, input and second light of two output ports of the first coupler 111 respectively with the first optical channel 120 lead to
The input connection in road 130, the output end of the first optical channel 120 is connected with the input port of the second coupler 112.Second coupling
One output port of device 112 is connected through the first Polarization Controller 113 with an input port of the 3rd coupler 114, another
Output port is connected through the 3rd optical channel 140 with one end of sensor fibre 117.
The output end of second optical channel 130 is connected with the first port of first annular device 115, and the of first annular device 115
Two-port netwerk is connected with the other end of sensor fibre 117, and the 3rd port of first annular device 115 is connected with grating, first annular
4th port of device 115 is connected with the input of the 4th optical channel 150.The output end of 4th optical channel 150 and the 3rd coupler
114 input port connection.
Referring to Fig. 1, the first optical channel 120 includes the second Polarization Controller 121, phase successively from input to output end
Type electrooptic modulator 122.Second optical channel 130 includes the 3rd Polarization Controller 131, intensity type successively from input to output end
Electrooptic modulator 132, erbium-doped fiber amplifier 133, the second circulator 134, optoisolator 135, the first of the second circulator 134
Port is connected with the output end of erbium-doped fiber amplifier 133, and second port is connected with grating 116, the 3rd port and optoisolator
135 input port connection.3rd optical channel 140 includes optical filter 141, optoisolator successively from input to output end
142 and scrambler 143.4th optical channel 150 includes erbium-doped fiber amplifier 151, the 3rd ring successively from input to output end
Shape device 152, dual-pass Mach-Zehnder interferometer 153, first port and the erbium-doped fiber amplifier 151 of the 3rd circulator 152
Output end is connected, and second port is connected with grating 116, the 3rd port and the input port of dual-pass Mach-Zehnder interferometer 153
Connection.
Referring to Fig. 2, Fig. 2 is the structure chart that Fig. 1 shows dual-pass Mach-Zehnder interferometer 153 in embodiment.Show in Fig. 2
In the embodiment gone out, dual-pass Mach-Zehnder interferometer 153 has two three-dB couplers 1531 and 1533, a cylindrical shape
Piezoelectric ceramics (PZT) 1532 and an optoisolator 1535.In order to realize the regulation of interference free path, by bilateral mach zhender
The optical fiber of one arm of interferometer 153 is wound on cylindrical shape PZT (piezoelectric ceramics 1532), is adjusted by DC voltage controller 1536
Section the DC voltage on the electrodes of PZT two is added in realize the control of interferometer optical path difference so that realize stimulated Brillouin scattering and
The separation of Rayleigh scattering.
The transfer function of dual-pass Mach-Zehnder interferometer 153 is：
F (v)=Iout/Iin=[1+cos (2 π v/FSR)]2/4
At normal temperatures, when optical wavelength is 1550nm, optical fiber Brillouin frequency displacement is 10.85GHz, from above formula, when
During FSR=2vB=21.7GHz, it is possible to achieve the separation of Brillouin scattering and Rayleigh scattering light.
In the embodiment shown in Fig. 1 and Fig. 2, the continuous light that laser is sent is equally divided into through the first coupler 111
Two beams, wherein a branch of enter the first optical channel 120, it is a branch of in addition to enter the second optical channel 130.Into the first optical channel 120
Laser is produced close to Brillouin shift after the laggard applying aspect type electrooptic modulator 122 of the second Polarization Controller 121 by modulation
The continuous light of frequency (about 11GHz).The continuous light is divided into two beam laser after the second coupler 112.Wherein 5% intensity
Laser beam by the first Polarization Controller 113 enter the 3rd coupler 114；And 95% laser beam then enters the 3rd optical channel
140.Laser beam into the 3rd optical channel 140 enters biography after optical filter 141, optoisolator 142 and scrambler 143 successively
Photosensitive fine 117.
Still further aspect, the laser beam of another beam 50% come out from the first coupler 111 is (i.e. into the second optical channel
130 laser beam) through the laggard applying aspect type electrooptic modulator 132 of the 3rd Polarization Controller 131, it is modulated to pulsed light.The arteries and veins
Wash off after being amplified by erbium-doped fiber amplifier 133 after the second circulator 134, enter first annular device through optoisolator 135
115 first port, then comes out the other end for entering sensor fibre 117 from the second port of first annular device 115.So,
The two-beam come out from the 3rd optical channel 140 and the second optical channel 130 produces stimulated Brillouin scattering in sensor fibre 117,
Opposite direction of the backward Brillouin scattering of generation along continuous light enters the second port of first annular device 115, is filtered through grating 116
Afterwards after erbium-doped fiber amplifier 151 amplifies, again pass by after grating 116 is filtered and enter dual-pass Mach-Zehnder interferometer 153.
Dual-pass Mach-Zehnder interferometer 153 separates the Rayleigh scattering light in back scattering and Brillouin scattering, from
And the less Brillouin scattering of noise is obtained, the Brillouin scattering through the first polarizer 113 with entering the 3rd coupler 114
The continuous light (i.e. reference light) of middle input is interfered.
Referring to Fig. 3, Fig. 3 is the structural representation for the optical fiber Brillouin distributed measurement device that embodiment of the present invention is provided
Figure.Optical fiber Brillouin distributed measurement device shown in Fig. 3 includes laser 200, photoelectric detector 300 and data acquisition process
Module 400, and the optical fiber Brillouin distributed measurement light path 100 that above-mentioned embodiment is related to, laser and the first coupler
111 input port connection, photoelectric detector 300 is connected with data acquisition and procession module 400, and the one of the 3rd coupler 114
Output port is connected with photoelectric detector 300.
In the embodiment illustrated in fig. 3, laser 200 can be narrow linewidth laser.The laser that laser 200 is sent
Into the first coupler 111 of the optical fiber Brillouin distributed measurement light path 100 shown in Fig. 1, in the optical fiber Brillouin shown in Fig. 1
After interfering in distributed measurement light path 100, it is radiated at through the 3rd coupler 114 on photoelectric detector 300 and is changed into electric signal.It is dry
Signal is related to be acquired and handle through the circuit in data acquisition and procession module 400.Some preferred embodiment in, adopt
The signal of collection is gathered into computer after conciliation by NI data collecting cards, by the LabVIEW routine calls of computer.
Referring to Fig. 4, Fig. 4 is the flow chart for the optical fiber Brillouin distributed measurement method that embodiment of the present invention is provided.Fig. 4
The optical fiber Brillouin distributed measurement method shown includes step S401-S404.
In step S401, the laser that laser is sent is divided into two ways of optical signals, wherein optical signal modulation is into arteries and veins all the way
Wash off, in addition all the way optical signal modulation into the continuous light with Brillouin shift frequency.
In step S402, continuous light is divided into the first continuous optical signal and the second continuous optical signal.Preferred at some
In embodiment, the first continuous luminous intensity accounts for the 95% of continuous luminous intensity.
In step S403, the first continuous optical signal and pulsed light is produced into excited Brillouin in sensor fibre 117 and dissipated
Penetrate, produce Brillouin scattering.
In step s 404, Brillouin scattering is interfered with the second continuous optical signal, after Data Analysis Services
Obtain measurement result.
Referring to Fig. 5, Fig. 5 be do not apply temperature and strain when Brillouin's backscatter intensity-frequency shift amount-distance and
Temperature change graph of a relation.In some embodiments, can be according to Brillouin shift and the pass of the temperature change of sensor fibre 117
System, calculates temperature.For example, carrying out result of interference according to Brillouin scattering and the second continuous optical signal, Brillouin shift is obtained；
Then, temperature is calculated according to following formula：
νB(T, 0)=vB(T0,0)[1+1.18*10-4ΔT]
Wherein：νBWhen (T, 0) represents strain stress for 0 and constant holding, the relation that Brillouin scattering optical frequency shift is varied with temperature
Formula；T0For reference temperature, 20 DEG C are typically taken；vB(T0, 0) represent temperature be 20 DEG C, strain stress be 0 when Brillouin scattering frequency displacement
Amount；Δ T=T-T0For the temperature variation relative to reference temperature.
According to Brillouin shift calculate the temperature change of sensor fibre 117 to implement process as follows：
The first step：Because the change of temperature can trigger the thermal expansion effects in sensor fibre 117, so as to influence optical fiber close
Degree.The thermo-optic effect of sensor fibre 117 can cause optical fibre refractivity to change, and the free energy of sensor fibre 117 is varied with temperature
The change of the physical parameters such as the Young's modulus and Poisson's ratio of sensor fibre 117 can be caused.Biography is assumed initially that when calculating temperature influence
Photosensitive fine 117 is strained, i.e. ε=0, using imfinitesimal method when temperature change is smaller, according to formula
Calculated with Taylor series expansion and the numerical value that substitutes into infinitesimal.Here no longer make further to beg for deriving in detail
By making ε=0, finally give Brillouin shift is to the variation relation of temperature：
νB(T, 0)=vB(T,0)[1+(Δnr+Δρr+ΔEr+Δkr)ΔT] (2)
In formula, T0For reference temperature, refer generally to T0=20 DEG C, temperature variation is Δ T.nTIt is thermal refractive index coefficient.ρT
It is density of optic fibre temperature coefficient, ETAnd kTIt is Young's modulus temperature coefficient and Poisson's ratio temperature coefficient respectively.Normal single mode quartz light
The fine parameters value related to temperature be：
In formula (2) generation, is arrived into formula (3), by pushing over calculating, the relational expression of Brillouin shift and temperature change is finally drawn：
νB(T, 0)=vB(T,0)[1+1.18*10-4ΔT] (4)
When T=20 DEG C, strain as 0, during a length of 1550nm of incident light wave, the Brillouin shift of general single mode fiber is about
10.85GHz, understands that temperature and Brillouin shift are linear by formula (4), and temperature often changes 1 DEG C, and Brillouin shift changes about
For 1.2803MHz.
Second step：Frequency deviation measurement.Frequency deviation measurement refers to carry out frequency modulation by detection light and pump light to incidence system, made
The frequency difference of two light sources is stably in stimulated Brillouin scattering magnification region, so as to be directly excited by power detection
Brillouin scattering gain spectral is so as to detect Brillouin shift.Principle is as follows：
If the intensity of single-ended incident laser is：
The electric-field intensity of microwave modulated signal is：
Em=Amcos(2πfmt) (6)
After ovennodulation, total intensity can be expressed as：
Above formula deformation is obtained：
Wherein fmFor frequency displacement, m is amplitude modulation coefficient.Incident laser its distribution of light intensity after frequency modulation is distributed as center field strength
Also symmetrical two sideband carriers in both sides.By adjusting the modulating frequency of electrooptic modulator, it is set to fall in excited Brillouin
Scattering gain magnification region, light is in transmitting procedure, rightmost side sideband f+fmAmplify center light f, energy is transferred to center
At light, at the same time, center light will also amplify leftmost side sideband f+fm, so realize the distribution of light intensity of sideband carrier and progressively turn
Move, it is final all to move on the sideband of the leftmost side.Finally, we only need to measure power output corresponding to different modulating frequencies
Maximum, can be achieved with the detection of stimulated Brillouin scattering gain spectral, and obtain now corresponding Brillouin shift.
3rd step：Preliminary treatment is carried out to signal using the method for stepping type cumulative mean.
Generally one-dimensional signal model is：
F (t)=s (t)+n (t) (9)
S (t) is useful signal in formula, and n (t) is that average is that 0, variance is σ2White Gaussian noise, open width degree signal to noise ratio is
For linear superposition is average, after m sub-samplings, i-th point of value is：
Because this is a kind of Batch processing algorithm, gathers and its average value is calculated by computer again after m group data, so with meter
The shortcomings of calculation amount is big, occupying system resources are more.Therefore, we use stepping type cumulative mean algorithm, change its cumulative mode with
Overcome the shortcoming that linear superposition is average.
OrderM-1 data average result before moment m-1 is represented,Represent the average result at moment m, fmRepresent
Moment m value, is obtained by above formula：
So, whenever data arrive, you can the average result of last time is updated with new data, so as to obtain new
Average result.
It can be obtained by formula (11)：
As can be seen here, with m increase, above formula Section 2 can be less and less, i.e. the effect of new data can be less and less.When
After m reaches to a certain degree, this goes to zero.Average result afterwards will be stablized constant.
4th step：Wavelet transformation is carried out to signal.
Because Brillouin signal can be because optical fiber be influenceed by temperature, strain and other noises and makes envelope not be one
Preferable smoothed curve, signal envelope has some kicks.Therefore, seeking one kind can suppress to noise, and can detect
Signal processing method to the signal of these projections is highly important, analyzes, is commonly used in field of signal processing based on more than
Wavelet transformation substantially conform to require, the side of the final link of weak signal extraction can be solved with this method in this application
Method.
The principle of wavelet transformation is：
It is assumed that giving a basic functionOrder
A and b are constant in formula, if a and b value is continually changing, can obtain family's functionIf flat
The signal that can be accumulated is x (t), then x (t) wavelet transformation is：
Wherein b is time shift, and a is scale factor, and the wavelet transformation Wx (a, b) that signal x (t) is understood in formula is a and b letter
Number.As wavelet basis, morther waveletBoth it can be real number, and can be complex function again.
It was found from formula, scale factor a effect is pairStretched, and b is the time for determining to analyze x (t)
Position, represent time centre.Therefore, byIt is changed intoThere can be following explanation：Work as a>When 1, a is bigger, thenTime domain width thanBecome bigger.Conversely, working as a<When 1, if a is smaller,Width become narrower.This
Sample a and b, which combine, to be assured that to x (t) centers analyzed and time width.
X (t) is made to be transformed to X (Ω) by fourier,Fourier be transformed to Ψ (Ω), then become by fourier
The property changed understands that the frequency-domain expression of wavelet transformation is：
From implementation process above, when a changes are small, the Time Domain Processing scope to x (t) narrows, but X (Ω) is existed
The accessible scope of frequency is broadened, and its centre frequency is moved to high frequency treatment.Conversely, when a becomes big, at x (t) time domain
Reason scope is broadened, and the accessible scope of frequency domain narrows, and its centre frequency is moved at low frequency.
Fig. 6 shows that excited Brillouin back scattering when changing a temperature at the 3000m distances of sensor fibre 117 is strong
The relation of degree-frequency shift amount-distance and temperature.
In other embodiment, result of interference is carried out according to Brillouin scattering and the second continuous optical signal, obtained
Take Brillouin shift；
Calculated and strained according to following formula：
νB(T0, ε) and=vB(T0,0)(1+4.48ε)
Wherein：νB(T0, ε) expression temperature be reference temperature (T0=20 DEG C) when, the pass that Brillouin shift changes with stress ε
It is formula；vB(T0, 0) expression temperature be reference temperature (T0=20 DEG C), stress ε be 0 when Brillouin shift amount.
Referring to Fig. 7, to scattered after excited Brillouin when Fig. 7 is one microstress of application at the 3000m distances of sensor fibre
Penetrate the graph of a relation of intensity-frequency shift amount-distance and temperature.The specific of the strain variation of sensor fibre 117 is calculated according to Brillouin shift
Implementation process is as follows：
Make temperature for that under conditions of certain value, Brillouin's frequency drift can be caused to carry out theory analysis strain, passed in light
Can occur elasto-optical effect during defeated, and then result in influence of the strain to optical fibre refractivity, also cause optical fiber Young's modulus and
The change of Poisson's ratio.It is available according to pushing over：
For small strain, in ε=0 pair, formula (16) carries out Taylor series expansion, is accurate to ε first order, can derive
Relation between strain and Brillouin shift：
νB(T, 0)=vB(T,0)[1+(Δnε+Δρε+ΔEε+Δkε)ε] (17)
Therefore, strain and the relational expression of Brillouin shift are：
νB(T0, ε) and=vB(T0,0)(1+4.48ε) (19)
ΔνB(T0,ε)-vB(T0, 0) and=4.48vB(T0,0)ε (20)
At normal temperatures, general single mode fiber Brillouin shift in the case of strainless is 10.85GHz, so each micro-
Brillouin shift changes delta v caused by strainBAbout 0.0486MHz.Wherein, frequency deviation measurement and signal transacting and calculating temperature
The embodiment of change is similar.
It should be understood that the invention is not limited in above-mentioned embodiment, every various changes or modification to the present invention are not
Depart from the spirit and scope of the present invention, if these change and modification belong to the present invention claim and equivalent technologies scope it
Interior, then the present invention is also implied that comprising these changes and modification.
Claims (9)
1. a kind of optical fiber Brillouin distributed measurement light path, it is characterised in that including the first coupler, the second coupler, the 3rd
Coupler, first annular device, the first optical channel, the second optical channel, sensor fibre, the 3rd optical channel and the 4th optical channel,
Two output ports of first coupler are defeated with the input of first optical channel and the second optical channel respectively
Enter end connection, the output end of first optical channel is connected with the input port of the second coupler, the one of second coupler
Individual output port is connected through the first Polarization Controller with an input port of the 3rd coupler, and another output port is through institute
The 3rd optical channel is stated to be connected with one end of the sensor fibre；
The output end of second optical channel is connected with the first port of the first annular device, and the second of the first annular device
Port is connected with the other end of the sensor fibre, and the 3rd port of the first annular device is connected with grating, and described first
4th port of circulator is connected with the input of the 4th optical channel；The output end of 4th optical channel is coupled with the described 3rd
The input port connection of device；
First optical channel includes the second Polarization Controller, phase type electrooptic modulator successively from input to output end.
2. optical fiber Brillouin distributed measurement light path as claimed in claim 1, it is characterised in that second optical channel is from defeated
Enter end includes the 3rd Polarization Controller, intensity type electrooptic modulator, erbium-doped fiber amplifier, the second annular to output end successively
Device, optoisolator, the first port of second circulator are connected with the output end of the erbium-doped fiber amplifier, second port
It is connected with grating, the 3rd port is connected with the input port of the optoisolator.
3. optical fiber Brillouin distributed measurement light path as claimed in claim 2, it is characterised in that the 3rd optical channel is from defeated
Enter end to output end includes optical filter, optoisolator and scrambler successively.
4. optical fiber Brillouin distributed measurement light path as claimed in claim 3, it is characterised in that the 4th optical channel is from defeated
Enter end to output end includes erbium-doped fiber amplifier, the 3rd circulator, dual-pass Mach-Zehnder interferometer, the 3rd ring successively
The first port of shape device is connected with the output end of the erbium-doped fiber amplifier, and second port is connected with grating, the 3rd port with
The input port connection of the dual-pass Mach-Zehnder interferometer.
5. a kind of optical fiber Brillouin distributed measurement device, it is characterised in that including laser, photoelectric detector and data acquisition
Processing module, in addition to the optical fiber Brillouin distributed measurement light path as described in claim any one of 1-4, the laser with
The input port connection of first coupler, the photoelectric detector is connected with the data acquisition and procession module, described
One output port of the 3rd coupler is connected with the photoelectric detector.
6. a kind of optical fiber Brillouin distributed measurement method, it is characterised in that including：
The laser that laser is sent is divided into two ways of optical signals, wherein optical signal modulation is into pulsed light all the way, light is believed all the way in addition
Number it is modulated into the continuous light with Brillouin shift frequency；
The continuous light is divided into the first continuous optical signal and the second continuous optical signal；
Described first continuous optical signal and the pulsed light are produced into stimulated Brillouin scattering in sensor fibre, Brillouin is produced
Scattered light；
The Brillouin scattering is interfered with the described second continuous optical signal, measurement knot is obtained after Data Analysis Services
Really.
7. a kind of optical fiber Brillouin distributed measurement method as claimed in claim 6, it is characterised in that the first continuous light
Intensity accounts for the 95% of the continuous light luminous intensity.
8. a kind of optical fiber Brillouin distributed measurement method as claimed in claim 6, it is characterised in that described " by the cloth
In deep scattered light interfered with the described second continuous optical signal, measurement result is obtained after Data Analysis Services " the step of wrap
Include：
Result of interference is carried out with the described second continuous optical signal according to the Brillouin scattering, Brillouin shift is obtained；
Temperature is calculated according to following formula：
νB(T, 0)=vB(T0,0)[1+1.18*10-4ΔT]
Wherein：νBWhen (T, 0) represents strain stress for 0 and constant holding, the relational expression that Brillouin scattering optical frequency shift is varied with temperature；T0
For reference temperature；vB(T0, 0) represent temperature be 20 DEG C, strain stress be 0 when Brillouin scattering frequency shift amount；Δ T=T-T0For phase
For the temperature variation of reference temperature.
9. a kind of optical fiber Brillouin distributed measurement method as claimed in claim 6, it is characterised in that described " by the cloth
In deep scattered light interfered with the described second continuous optical signal, measurement result is obtained after Data Analysis Services " the step of wrap
Include：
Result of interference is carried out with the described second continuous optical signal according to the Brillouin scattering, Brillouin shift is obtained；
Calculated and strained according to following formula：
νB(T0, ε) and=vB(T0,0)(1+4.48ε)
Wherein：νB(T0, ε) expression temperature be T0At=20 DEG C, the relational expression that Brillouin shift changes with stress ε；vB(T0, 0) and table
Temperature displaying function is T0=20 DEG C, stress ε be 0 when Brillouin shift amount.
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| CN105241390B (en) * | 2015-10-21 | 2018-05-15 | 吉林大学 | Quick Brillouin optical time domain analysis type strain gauge means and data processing method |
| CN105588587B (en) * | 2015-12-11 | 2017-10-24 | 中国电子科技集团公司第四十一研究所 | Spontaneous brillouin scattering signal extracting device and method based on auto level control |
| CN105953724A (en) * | 2016-04-20 | 2016-09-21 | 北京信息科技大学 | Two-channel adjustable Mach-Zehnder interferometer |
| CN105910546A (en) * | 2016-04-20 | 2016-08-31 | 北京信息科技大学 | BOTDR system based on dual-channel Mach-Zehnder interferometer |
| CN109084883A (en) * | 2018-08-09 | 2018-12-25 | 合肥工业大学 | Based on phase-BOTDR optical fiber distributed type Brillouin's vibrating sensing measurement method |
| CN114720780B (en) * | 2022-06-09 | 2022-09-09 | 杭州微纳智感光电科技有限公司 | High-power high-frequency microwave field intensity sensing method and device |
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