CN104977030A - Dynamic distributed Brillouin sensing device based on low-frequency arbitrary waveform optical frequency agility technology and method thereof - Google Patents
Dynamic distributed Brillouin sensing device based on low-frequency arbitrary waveform optical frequency agility technology and method thereof Download PDFInfo
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Abstract
The invention provides a dynamic distributed Brillouin sensing device based on a low-frequency arbitrary waveform optical frequency agility technology and a method thereof, belongs to the field of optics, and solves problems of high cost and complex system in distributed monitoring on transient signals by adopting an existing frequency agility technology based on an arbitrary waveform technology. The device comprises a laser device, a coupler, a microwave source, an arbitrary function generator, an arbitrary waveform generator, an optical isolator, a data acquisition module, polarization controllers PC1-PC4, optical intensity modulators IM1 and IM2, an Er-doped fiber amplifier EDFA, a circulator R1, a single sideband intensity modulator SSBM and a polarization maintaining fiber PMF to be measured. A lower sideband of hundreds of megahertz is generated to act as probe light by adopting a single sideband modulation method so that frequency agility probe light can be acquired by adopting the low-bandwidth arbitrary waveform generator of hundreds of megahertz.
Description
Technical field
The present invention relates to the dynamic Brillouin sensing technology of a kind of low cost, high reliability, belong to optical field.
Background technology
Development of OFS is rapid in recent years, Brillouin optical time domain analysis technology (BOTDA) obtains extensive research and apply both domestic and external, Brillouin optical time domain analysis technology can carry out sensing and measurement to temperature and strain, has that spatial resolution is high, distance sensing is far away, realize the advantages such as distributed sensing.It is widely used in building structure monitoring, fire monitoring and oil pipeline monitoring etc.
Brillouin optical time domain analysis technology utilizes stimulated Brillouin scattering in optical fiber (SBS) this nonlinear effect to carry out sensing to strain extraneous suffered by optical fiber and temperature.The pump light transmitted in opposite directions carries out energy transferring with detection light by stimulated Brillouin scattering, and the degree that detection light is exaggerated depends on the frequency-splitting between pump light and detection light.General silica fibre Brillouin shift is at about 11GHz, and temperature and strain all can change Brillouin shift, and carrying out frequency sweeping to detection light and just can obtain brillouin gain spectrum, is the size of temperature or strain according to the coefficients conversion of correspondence.Pump light adopt pulsed light so can distributed measurement optical fiber along the line on the information of often.
But traditional Brillouin optical time domain analysis system due to sweep frequency required time longer, cannot the transient change of measuring-signal, static or gradual signal can only be measured.In order to address this problem, realize distributed dynamic sensing technology for the distributed monitoring to transient signal, need to adopt the frequency agility technology based on any wave technology.The core devices of this technology is Arbitrary Waveform Generator (Arbitrary Waveform Generator).Because ordinary optic fibre Brillouin shift is at about 11GHz, so generally need the Arbitrary Waveform Generator of comparable bandwidths.The Arbitrary Waveform Generator cost of high bandwidth is high, and high-frequency apparatus very easily damages and is subject to external interference, significantly limit the actual application value of this method.
Prior art adopts three kinds of schemes to overcome the technical matters that exists when adopting frequency agility technology, first two scheme adopt be that application AWG (Arbitrary Waveform Generator) will the mode of detection light rapid frequency-sweeping.
The I/Q raising frequency method of the AWG of the first scheme employing microwave vector generator and binary channels 500MHz realizes the rapid scanning (YairPeled to brillouin gain spectrum, AviMotil, and Moshe Tur, " Fast Brillouin optical timedomain analysis for dynamic sensing; " Vol 20NO.8Optical Express 8584,2012).The bandwidth that this method reduces AWG used is 500MHz, but its I/Q raising frequency technical costs adopted is also higher.First scheme adopts the second order side frequency of intensity modulator as detection light, so required AWG bandwidth is reduced half (such as application on June 13rd, 2013, publication number be the Chinese patent " dynamic distributed Brillouin light fiber sensing equipment and method " of CN103335666A) from Brillouin shift size.The bandwidth of AWG needed for effective reduction, but still at about 5.5GHz.
The third the modulation system of detection gloss comb frequency spectrum is avoided the kinetic measurement scheme of frequency sweeping (such as application on April 6th, 2012, publication number be the Chinese patent " the BOTDA system based on comb frequency spectrum continuous probe light " of CN102645236B).But the measurement of brillouin gain spectrum needs the method adopting heterodyne detection, and need the scanning of a local oscillator electric signal in heterodyne detection process, electric scanning needs the regular hour, and therefore the program actual measurement time is still longer, really cannot realize kinetic measurement.
Summary of the invention
The present invention seeks to solve existing employing that cost is high, the problem of system complex based on existing when appointing the frequency agility technology of wave technology to carry out distributed monitoring to transient signal, providing a kind of dynamic distributed Brillouin sensing device and method of the optics frequency agility technology based on any ripple of low frequency.
The dynamic distributed Brillouin sensing device of the optics frequency agility technology based on any ripple of low frequency of the present invention, it comprises laser instrument, coupling mechanism, microwave source, arbitrary-function generator, Arbitrary Waveform Generator, optoisolator, data acquisition module, the first Polarization Controller PC1, the second Polarization Controller PC2, the 3rd Polarization Controller PC3, the 4th Polarization Controller PC4, the first light intensity modulator IM1, the second light intensity modulator IM2, erbium-doped optical fiber amplifier EDFA, circulator R1, single-side belt intensity modulator SSBM and polarization maintaining optical fibre PMF to be measured;
The laser beam that laser instrument sends is divided into two bundle laser by coupling mechanism;
Wherein beam of laser enters the first light intensity modulator IM1 through the first Polarization Controller PC1, on first light intensity modulator IM1 carries out the laser of input under the control of microwave source, lower side frequency is modulated, on, light beam after lower side frequency modulation is modulated through the second light intensity modulator IM2 and is exported square pulse light, this square pulsed light light is via optical fiber bragg grating FBG filtering lower side frequency, the light beam of light beam output after erbium-doped optical fiber amplifier EDFA amplifies of filtering lower side frequency is as pump light, this pump light enters 1 mouthful of circulator R1 through the 3rd Polarization Controller PC3, 2 mouthfuls from circulator R1 export to polarization maintaining optical fibre PMF to be measured,
Another beam of laser enters single-side belt intensity modulator SSBM through the second Polarization Controller PC2, single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator, the light beam that single-side belt intensity modulator SSBM exports is as detection light, described detection light, through optoisolator and the 4th Polarization Controller PC4, enters from another direction polarization maintaining optical fibre PMF to be measured;
In polarization maintaining optical fibre PMF to be measured, meet detection light and the pump light generation Brillouin amplification process of Brillouin amplification condition; Detection light through Brillouin amplification enters 2 mouthfuls of circulator R1, and exports data acquisition module to from 3 mouthfuls of circulator R1;
Arbitrary Waveform Generator synchronously triggers arbitrary-function generator and provides square pulse-modulated signal to the second light intensity modulator IM2; The synchronous trigger data acquisition modules acquiring data of Arbitrary Waveform Generator.
Based on the method for the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency, the method comprises the following steps:
Laser beam is divided into two bundles by step one, coupling mechanism, and wherein beam of laser utilizes step 2 to generate pump light, and another beam of laser utilizes step 3 to generate detection light; Pump light and detection light all complete under the control of Arbitrary Waveform Generator, Arbitrary Waveform Generator sends three tunnel control signals, is respectively to the radiofrequency signal of single-side belt intensity modulator SSBM, to the trigger pip of arbitrary-function generator with to the trigger pip of data acquisition module;
Step 2, wherein beam of laser regulate after polarization state through the first Polarization Controller PC1 and enter the first light intensity modulator IM1, and microwave source controls the upper lower side frequency that the first light intensity modulator IM1 modulates incident laser, frequency each frequency displacement f up and down of incident laser
rFlaser after frequency displacement is modulated through the second light intensity modulator IM2 and is exported square pulse light, this square pulsed light is via optical fiber bragg grating FBG filtering lower side frequency, and the light beam of light beam output after erbium-doped optical fiber amplifier EDFA amplifies of filtering lower side frequency is as pump light; Pump light is by the pulse train of N number of identical cycle T; Wherein, f
rFfor the microwave modulating frequency of microwave source;
Step 3, another beam of laser regulate after polarization state through the second Polarization Controller PC2 and enter single-side belt intensity modulator SSBM, single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator, and the light beam that single-side belt intensity modulator SSBM exports is as detection light;
The pump light that step 4, step 2 generate enters polarization maintaining optical fibre PMF to be measured from a direction; The detection light that step 3 generates enters polarization maintaining optical fibre PMF to be measured from another direction; In polarization maintaining optical fibre PMF to be measured, meet detection light and the pump light generation Brillouin amplification process of Brillouin amplification condition; Detection light through Brillouin amplification exports data acquisition module to through circulator;
Step 5, determine SBS effect position in a fiber according to the time of return detector, when after the scanning completing a frequency sweep cycle T, obtain the brillouin gain spectrum in each spatial point on the polarization maintaining optical fibre PMF to be measured under this frequency state;
Step 6, according to Brillouin shift υ
bwith the linear functional relation υ of strain stress
b=υ
b0+ C
sε, completes the measurement of the strain of polarization maintaining optical fibre PMF to be measured under this frequency state,
Wherein, υ
b0the Brillouin shift of testing fiber free state, C
sit is the coefficient of strain.
Advantage of the present invention: the present invention adopts the method for single-sideband modulation to produce the lower sideband of hundreds of megahertz as detection light, and the AWG (Arbitrary Waveform Generator) of the hundreds of megahertz of low bandwidth so just can be adopted to obtain frequency agility detection light.Adopt low frequency optics frequency agility technology and based on the dynamic distributed Brillouin light fiber sensing equipment of this technology and method, reduce instrument cost and improve the reliability of system.
Accompanying drawing explanation
Fig. 1 is the dynamic distributed Brillouin sensing apparatus structure schematic diagram of the optics frequency agility technology based on any ripple of low frequency of the present invention;
Fig. 2 is the sequential chart of detection light and pump light;
Fig. 3 is detection light and pump light frequency relation figure;
Fig. 4 is schematic diagram when measuring stress.
Embodiment
Embodiment one: present embodiment is described below in conjunction with Fig. 1 to Fig. 4, based on the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency described in present embodiment, it comprises laser instrument 1, coupling mechanism 2, microwave source 3, arbitrary-function generator 4, Arbitrary Waveform Generator 5, optoisolator 6, data acquisition module 7, first Polarization Controller PC1, second Polarization Controller PC2, 3rd Polarization Controller PC3, 4th Polarization Controller PC4, first light intensity modulator IM1, second light intensity modulator IM2, erbium-doped optical fiber amplifier EDFA, circulator R1, single-side belt intensity modulator SSBM and polarization maintaining optical fibre PMF to be measured,
The laser beam that laser instrument 1 sends is divided into two bundle laser by coupling mechanism 2;
Wherein beam of laser enters the first light intensity modulator IM1 through the first Polarization Controller PC1, on first light intensity modulator IM1 carries out the laser of input under the control of microwave source 3, lower side frequency is modulated, on, light beam after lower side frequency modulation is modulated through the second light intensity modulator IM2 and is exported square pulse light, this square pulsed light light is via optical fiber bragg grating FBG filtering lower side frequency, the light beam of light beam output after erbium-doped optical fiber amplifier EDFA amplifies of filtering lower side frequency is as pump light, this pump light enters 1 mouthful of circulator R1 through the 3rd Polarization Controller PC3, 2 mouthfuls from circulator R1 export to polarization maintaining optical fibre PMF to be measured,
Another beam of laser enters single-side belt intensity modulator SSBM through the second Polarization Controller PC2, single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator 5, the light beam that single-side belt intensity modulator SSBM exports is as detection light, described detection light, through optoisolator 6 and the 4th Polarization Controller PC4, enters from another direction polarization maintaining optical fibre PMF to be measured;
In polarization maintaining optical fibre PMF to be measured, meet detection light and the pump light generation Brillouin amplification process of Brillouin amplification condition; Detection light through Brillouin amplification enters 2 mouthfuls of circulator R1, and exports data acquisition module 7 to from 3 mouthfuls of circulator R1;
Arbitrary Waveform Generator 5 synchronously triggers arbitrary-function generator 4 and provides square pulse-modulated signal to the second light intensity modulator IM2; Synchronous trigger data acquisition module 7 image data of Arbitrary Waveform Generator 5.
The model that arbitrary-function generator 4 adopts is AFG3252.
Present embodiment is the optics frequency agility technology based on low bandwidth AWG (Arbitrary Waveform Generator), first pumping pulse light is carried out large-scale upshift, makes the frequency difference of pump light and carrier frequency light be slightly less than the Brillouin shift of testing fiber.On this basis, adopt low bandwidth AWG (Arbitrary Waveform Generator) to carry out the lower sideband frequencies scanning of hundreds of megahertz to detection light, dynamic distributed Brillouin fiber optic sensing can be realized.
First laser device laser exports and is divided into two-way through photo-coupler.Set out on a journey as pump light, first regulate the polarization state entering the first light intensity modulator IM1 through PC1, setting microwave source 3 rf frequency is slightly less than the Brillouin shift under the free state of testing fiber.Carry out modulation to laser frequency and produce upper lower side frequency, IM1 output directly enters IM2 and is modulated to square pulse light, through FBG filtering lower side frequency.Recycling erbium-doped optical fiber amplifier EDFA amplifies pumping pulse light, is regulated the polarization state entering polarization maintaining optical fibre PMF to be measured through circulator R1 by PC3.
Lower road, as detection light, regulates the polarization state entering SSBM by PC2, and SSBM modulation exports lower side frequency.Optoisolator 6 is used to be to allow detection light pass through and to stop the pump light of high-power reverse transfer to be propagated, PC4 regulates the polarization state entering polarization maintaining optical fibre PMF to be measured from the other end, entering 3 ports through circulator 2 port after detection light and pump light interact to export, is finally that data acquisition module 7 gathers the detection light after amplification.
One tunnel of IM1, IM2 is for generation of pump light.Single-side belt intensity modulator SSBM is operated in lower side frequency output mode, the radio frequency signals drive of the frequency step change sent by AWG (Arbitrary Waveform Generator) 5.IM1 is for realizing on pump light downshift a little less than optical fiber Brillouin frequency displacement, IM2 is used for continuous print pumping laser to be modulated to square pulse light, and the 3rd Polarization Controller PC3 and the 4th Polarization Controller PC4 is used for the polarization state of detection light and pump light to be adjusted in the same optical axis of polarization maintaining optical fibre to be measured.Detection light after amplification is monitored by data acquisition module 7.This data acquisition module is operated in external trigger pattern, and trigger pip is provided by AWG (Arbitrary Waveform Generator) 5.
The detection light exported after modulating via detection optical SSB intensity modulator SSBM and pump light intensities modulator IM1, IM2 and the sequential of pump light are according to Fig. 2.Frequency range as radiofrequency signal is f
1to f
2, number of frequency steps f
s, then
if arbitrary frequency sweep cycle is T.Completing the single pass time used is NT, and the sampling rate under this parameter reaches as high as
namely can be to highest frequency
dynamic Signal measure.
As shown in Figure 4, be placed on two eccentric motors 8 at polarization maintaining optical fibre PMF to be measured, and on polarization maintaining optical fibre PMF to be measured, place compacting fixture 9, recycling Fig. 1 shown device is measured.
By being handled as follows the detection waveform data after the amplification utilizing data acquisition module to record, the Brillouin shift of testing fiber each point can be obtained.Utilize Brillouin shift and the linear relationship treating sensing physical quantity-strain (Dynamic Signal), the numerical value of the Dynamic Signal of testing fiber each point can be recorded.
1) by the data (being frame data) after the amplification corresponding to single frequency sweeping temporally length be T intercept, be divided into N section.If every segment data count as L, then these data are divided into the matrix of N × L, if matrix is called A;
2) according to treating the linear functional relation of sensing physical quantity (strain) with brillouin gain spectrum, calculate the numerical value of the sensing physical quantity (stress) of each point on this frequency sweeping moment testing fiber, obtain matrix B, dimension is N × L, i.e. the data of this Dynamic Signal one frame.
3) for the data of frequency sweeping each time, do as above 1), 2) step operation, the data of all frames of Dynamic Signal to be measured can be obtained, thus complete the measurement to Dynamic Signal.
Embodiment two: present embodiment is described further embodiment one, the microwave modulating frequency f of microwave source 3
rFby formula
f
RF＝min{υ
B0+△υ
B_plus-max(f
AWG),υ
B0-
|△υ
B_neg |-min(f
AWG)}
Ask for;
Wherein: υ
b0for the Brillouin shift of testing fiber free state, △ υ
b_negfor the maximum negative strain of testing fiber, △ υ
b_plusfor the normal strain upper limit of testing fiber, f
aWGfor Low Frequency Arbitrary Waveform Generator modulating frequency.
Embodiment three: present embodiment is described further embodiment one, when single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator 5, has two schemes:
The first: it is that the two paths of signals of 90 ° exports to single-side belt intensity modulator SSBM as control signal that Arbitrary Waveform Generator 5 sends phase differential.
The second: Arbitrary Waveform Generator 5 sends the identical signal of two-way, wherein a road signal produces after 90 ° of phase differential through phase-shifter, jointly exports to single-side belt intensity modulator SSBM as control signal with another road.
Embodiment four: based on the method for the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency described in embodiment one, it is characterized in that, the method comprises the following steps:
Laser beam is divided into two bundles by step one, coupling mechanism 2, and wherein beam of laser utilizes step 2 to generate pump light, and another beam of laser utilizes step 3 to generate detection light; Pump light and detection light all complete under the control of Arbitrary Waveform Generator 5, Arbitrary Waveform Generator 5 sends three tunnel control signals, is respectively to the radiofrequency signal of single-side belt intensity modulator SSBM, to the trigger pip of arbitrary-function generator 4 with to the trigger pip of data acquisition module 7;
Arbitrary Waveform Generator 5 inversion frequency is very fast, in order to each frequency of sensing measurement just should a corresponding pulse signal as Fig. 2, its this output pulse signal is told exactly to the trigger pip of arbitrary-function generator 4, square shape pulsed signal is sent by arbitrary-function generator 4, process is exactly that Arbitrary Waveform Generator 5 exports a frequency, it tells that (triggering) arbitrary-function generator 4 exports a pulse signal simultaneously, kinetic measurement very fast (microsecond) exports again next frequency, it needs again to tell that (triggering) arbitrary-function generator 4 exports a pulse signal simultaneously, trigger and just tell when it exports square pulse, this waveform of square pulse is still exported by arbitrary-function generator 4.
Step 2, wherein beam of laser regulate after polarization state through the first Polarization Controller PC1 and enter the first light intensity modulator IM1, and microwave source 3 controls the upper lower side frequency that the first light intensity modulator IM1 modulates incident laser, frequency each frequency displacement f up and down of incident laser
rFlaser after frequency displacement is modulated through the second light intensity modulator IM2 and is exported square pulse light, this square pulsed light is via optical fiber bragg grating FBG filtering lower side frequency, and the light beam of light beam output after erbium-doped optical fiber amplifier EDFA amplifies of filtering lower side frequency is as pump light; Pump light is by the pulse train of N number of identical cycle T; Wherein, f
rFfor the microwave modulating frequency of microwave source 3;
Step 3, another beam of laser regulate after polarization state through the second Polarization Controller PC2 and enter single-side belt intensity modulator SSBM, single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator 5, and the light beam that single-side belt intensity modulator SSBM exports is as detection light;
The pump light that step 4, step 2 generate enters polarization maintaining optical fibre PMF to be measured from a direction; The detection light that step 3 generates enters polarization maintaining optical fibre PMF to be measured from another direction; In polarization maintaining optical fibre PMF to be measured, meet detection light and the pump light generation Brillouin amplification process of Brillouin amplification condition; Probe light through Brillouin amplification exports data acquisition module 7 to through circulator;
Step 5, determine SBS effect position in a fiber according to the time of return detector, when after the scanning completing a frequency sweep cycle T, obtain the brillouin gain spectrum in each spatial point on the polarization maintaining optical fibre PMF to be measured under this frequency state;
Step 6, according to Brillouin shift υ
bwith the linear functional relation υ of strain stress
b=υ
b0+ C
sε, completes the measurement of the strain of polarization maintaining optical fibre PMF to be measured under this frequency state,
Wherein, υ
b0the Brillouin shift of testing fiber free state, C
sit is the coefficient of strain.
Embodiment four: present embodiment is described further embodiment three, the acquisition process detecting light in step 3 is:
The modulation signal f that Arbitrary Waveform Generator 5 sends to the modulated terminal of single-side belt intensity modulator SSBM
mthe t wave train that () changes for N number of frequency step:
Wherein: f
m0for the original frequency of the wave train, f
sfor number of frequency steps, T is arbitrary frequency sweep cycle,
for rounding, t is the time;
The beam of laser of input is modulated into the detection light f that lower side frequency exports by single-side belt intensity modulator SSBM
tcg(t):
f
tcg(t)＝f
0-f
m(t)，
Wherein: f
0for the frequency of the beam of laser of input;
Obtaining detecting light is be the light set of the different frequency of T by N number of cycle.
The microwave modulating frequency f of microwave source 3
rFby formula
f
RF＝min{υ
B0+△υ
B_plus-max(f
AWG),υ
B0-
|△υ
B_neg |-min(f
AWG)}
Ask for;
Wherein: υ
b0for the Brillouin shift of testing fiber free state, △ υ
b_negfor the maximum negative strain of testing fiber, △ υ
b_plusfor the normal strain upper limit of testing fiber, f
aWGfor Low Frequency Arbitrary Waveform Generator modulating frequency.
Claims (8)
1. based on the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, it comprises laser instrument (1), coupling mechanism (2), microwave source (3), arbitrary-function generator (4), Arbitrary Waveform Generator (5), optoisolator (6), data acquisition module (7), first Polarization Controller PC1, second Polarization Controller PC2, 3rd Polarization Controller PC3, 4th Polarization Controller PC4, first light intensity modulator IM1, second light intensity modulator IM2, erbium-doped optical fiber amplifier EDFA, circulator R1, single-side belt intensity modulator SSBM and polarization maintaining optical fibre PMF to be measured,
The laser beam that laser instrument (1) sends is divided into two bundle laser by coupling mechanism (2);
Wherein beam of laser enters the first light intensity modulator IM1 through the first Polarization Controller PC1, on first light intensity modulator IM1 carries out the laser of input under the control of microwave source (3), lower side frequency is modulated, on, light beam after lower side frequency modulation is modulated through the second light intensity modulator IM2 and is exported square pulse light, this square pulsed light light is via optical fiber bragg grating FBG filtering lower side frequency, the light beam of light beam output after erbium-doped optical fiber amplifier EDFA amplifies of filtering lower side frequency is as pump light, this pump light enters 1 mouthful of circulator R1 through the 3rd Polarization Controller PC3, 2 mouthfuls from circulator R1 export to polarization maintaining optical fibre PMF to be measured,
Another beam of laser enters single-side belt intensity modulator SSBM through the second Polarization Controller PC2, single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator (5), the light beam that single-side belt intensity modulator SSBM exports is as detection light, described detection light, through optoisolator (6) and the 4th Polarization Controller PC4, enters from another direction polarization maintaining optical fibre PMF to be measured;
In polarization maintaining optical fibre PMF to be measured, meet detection light and the pump light generation Brillouin amplification process of Brillouin amplification condition; Detection light through Brillouin amplification enters 2 mouthfuls of circulator R1, and exports data acquisition module (7) to from 3 mouthfuls of circulator R1;
Arbitrary Waveform Generator (5) synchronously triggers arbitrary-function generator (4) and provides square pulse-modulated signal to the second light intensity modulator IM2; Synchronous trigger data acquisition module (7) image data of Arbitrary Waveform Generator (5).
2., according to claim 1 based on the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, the microwave modulating frequency f of microwave source (3)
rFby formula
f
RF＝min{υ
B0+Δυ
B_plus-max(f
AWG),υ
B0-|Δυ
B_neg|-min(f
AWG)}
Ask for;
Wherein: υ
b0for the Brillouin shift of testing fiber free state, Δ υ
b_negfor the maximum negative strain of testing fiber, Δ υ
b_plusfor the normal strain upper limit of testing fiber, f
aWGfor Low Frequency Arbitrary Waveform Generator modulating frequency.
3., according to claim 1 based on the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, the model that arbitrary-function generator (4) adopts is AFG3252.
4. according to claim 1 based on the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, when single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator (5), it is that the two paths of signals of 90 ° exports to single-side belt intensity modulator SSBM as control signal that Arbitrary Waveform Generator (5) sends phase differential.
5. according to claim 1 based on the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, when single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator (5), Arbitrary Waveform Generator (5) sends the identical signal of two-way, wherein a road signal produces after 90 ° of phase differential through phase-shifter, jointly exports to single-side belt intensity modulator SSBM as control signal with another road.
6. described in claim 1 based on the method for the dynamic distributed Brillouin sensing device of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, the method comprises the following steps:
Laser beam is divided into two bundles by step one, coupling mechanism (2), and wherein beam of laser utilizes step 2 to generate pump light, and another beam of laser utilizes step 3 to generate detection light; Pump light and detection light all complete under the control of Arbitrary Waveform Generator (5), Arbitrary Waveform Generator (5) sends three tunnel control signals, is respectively to the radiofrequency signal of single-side belt intensity modulator SSBM, to the trigger pip of arbitrary-function generator (4) with to the trigger pip of data acquisition module (7);
Step 2, wherein beam of laser regulate after polarization state through the first Polarization Controller PC1 and enter the first light intensity modulator IM1, microwave source (3) controls the upper lower side frequency that the first light intensity modulator IM1 modulates incident laser, frequency each frequency displacement f up and down of incident laser
rFlaser after frequency displacement is modulated through the second light intensity modulator IM2 and is exported square pulse light, this square pulsed light is via optical fiber bragg grating FBG filtering lower side frequency, and the light beam of light beam output after erbium-doped optical fiber amplifier EDFA amplifies of filtering lower side frequency is as pump light; Pump light is by the pulse train of N number of identical cycle T; Wherein, f
rFfor the microwave modulating frequency of microwave source (3);
Step 3, another beam of laser regulate after polarization state through the second Polarization Controller PC2 and enter single-side belt intensity modulator SSBM, single-side belt intensity modulator SSBM carries out lower side frequency modulation to input beam under the control of Arbitrary Waveform Generator (5), and the light beam that single-side belt intensity modulator SSBM exports is as detection light;
The pump light that step 4, step 2 generate enters polarization maintaining optical fibre PMF to be measured from a direction; The detection light that step 3 generates enters polarization maintaining optical fibre PMF to be measured from another direction; In polarization maintaining optical fibre PMF to be measured, meet detection light and the pump light generation Brillouin amplification process of Brillouin amplification condition; Probe light through Brillouin amplification exports data acquisition module (7) to through circulator;
Step 5, determine SBS effect position in a fiber according to the time of return detector, when after the scanning completing a frequency sweep cycle T, obtain the brillouin gain spectrum in each spatial point on the polarization maintaining optical fibre PMF to be measured under this frequency state;
Step 6, according to Brillouin shift υ
bwith the linear functional relation υ of strain stress
b=υ
b0+ C
sε, completes the measurement of the strain of polarization maintaining optical fibre PMF to be measured under this frequency state,
Wherein, υ
b0the Brillouin shift of testing fiber free state, C
sit is the coefficient of strain.
7., according to claim 6 based on the dynamic distributed Brillouin sensing method of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, the acquisition process detecting light in step 3 is:
The modulation signal f that Arbitrary Waveform Generator (5) sends to the modulated terminal of single-side belt intensity modulator SSBM
mthe t wave train that () changes for N number of frequency step:
Wherein: f
m0for the original frequency of the wave train, f
sfor number of frequency steps, T is arbitrary frequency sweep cycle,
for rounding, t is the time;
The beam of laser of input is modulated into the detection light f that lower side frequency exports by single-side belt intensity modulator SSBM
tcg(t):
f
tcg(t)＝f
0-f
m(t)，
Wherein: f
0for the frequency of the beam of laser of input;
Obtaining detecting light is be the light set of the different frequency of T by N number of cycle.
8., according to claim 6 based on the dynamic distributed Brillouin sensing method of the optics frequency agility technology of any ripple of low frequency, it is characterized in that, the microwave modulating frequency f of microwave source (3)
rFby formula
f
RF＝min{υ
B0+Δυ
B_plus-max(f
AWG),υ
B0-|Δυ
B_neg|-min(f
AWG)}
Ask for;
Wherein: υ
b0for the Brillouin shift of testing fiber free state, Δ υ
b_negfor the maximum negative strain of testing fiber, Δ υ
b_plusfor the normal strain upper limit of testing fiber, f
aWGfor Low Frequency Arbitrary Waveform Generator modulating frequency.
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|---|---|---|---|
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