CN111141414B - Temperature and strain simultaneous measurement device and method based on chaos BOCDA - Google Patents
Temperature and strain simultaneous measurement device and method based on chaos BOCDA Download PDFInfo
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- CN111141414B CN111141414B CN201911377111.3A CN201911377111A CN111141414B CN 111141414 B CN111141414 B CN 111141414B CN 201911377111 A CN201911377111 A CN 201911377111A CN 111141414 B CN111141414 B CN 111141414B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- 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
- G01B11/18—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge using photoelastic elements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—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
- 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
Abstract
The invention belongs to the field of distributed optical fiber sensing systems, and discloses a temperature and strain simultaneous measurement device based on chaotic BOCDA, which comprises a chaotic laser, an optical fiber coupler, a first polarization controller, a first electro-optic modulator, an optical delay generator, a first optical amplifier, an optical polarization scrambler, a sensing optical fiber, a second polarization controller, a second optical amplifier, a signal generator, a second electro-optic modulator, a third optical amplifier, an optical circulator, a filter, a photoelectric detector, a phase-locked amplifier, an arbitrary pulse function generator, a data acquisition card and a calculation unit. According to the invention, the simultaneous measurement of temperature and strain is realized on the premise of ensuring high spatial resolution by utilizing the characteristics that the Brillouin gain spectrum measured by the chaotic BOCDA system in the LEAF optical fiber has multiple peaks and the Brillouin frequency shift linear coefficients of the peaks are different along with the temperature or strain.
Description
Technical Field
The invention belongs to the field of distributed optical fiber sensing systems, and particularly relates to a temperature and strain simultaneous measurement device and method based on chaotic BOCDA, which are used for realizing simultaneous measurement of temperature and strain.
Background
The optical fiber sensing technology takes optical fiber as a signal sensing and transmission medium, and compared with the traditional sensor, the optical fiber has the advantages of small volume, high sensitivity, strong anti-electromagnetic interference capability and the like, so that the optical fiber sensing technology attracts attention once appearing and is widely applied to the fields of national defense, military, aerospace, measurement and test and the like.
The distributed optical fiber sensing system mainly comprises three sensing systems based on Rayleigh scattering effect, Raman scattering effect and Brillouin scattering effect. The distributed optical fiber sensing system based on the brillouin scattering effect has become the most potential development direction in the optical fiber sensing technology because the distributed optical fiber sensing system can realize the measurement of temperature and strain information at different positions along the optical fiber. Optical fiber sensing systems based on brillouin scattering are classified into optical time domain systems and optical coherence domain systems. The optical time domain system comprises a Brillouin optical time domain reflection technology (BOTDR) and a Brillouin optical time domain analysis technology (BOTDA). The time domain system has great advantages in sensing distance, can realize long-distance sensing, but is limited by the service life of acoustic phonons, and has low spatial resolution, so that the application range of the time domain system is limited. The optical coherent domain system comprises a Brillouin optical coherent domain reflection technology (BOCDR) and a Brillouin optical coherent domain analysis technology (BOCDA), the spatial resolution of the optical coherent domain system depends on the coherence length of a light source, high spatial resolution can be achieved, and long-distance sensing cannot be achieved.
The chaotic laser is used as a low-coherence light source and is used for solving the problem that the sensing distance and the spatial resolution cannot be considered simultaneously in the Brillouin optical coherence domain distributed optical fiber sensing technology. The Chinese patents ZL201310045097.3 and ZL201510531253.6 propose that the chaotic laser is used as a light source for optical fiber sensing, successfully solve the problem that the sensing distance and the spatial resolution cannot be considered simultaneously in a distributed optical fiber sensing system, and realize optical fiber sensing with long distance and ultrahigh spatial resolution. However, the brillouin optical coherence domain system is based on the measurement of the temperature or strain information along the sensing optical fiber by using the variable optical delay line, so that each measurement can only be performed on the temperature or strain information at a certain point on the optical fiber, and the continuous measurement of the information along the optical fiber cannot be realized. A Brillouin distributed optical fiber sensing device and method (Chinese patent: ZL201610305960.8) for positioning by a chaos correlation method obtains a Brillouin gain spectrum by recording the corresponding relation between the modulation frequency of a modulation sideband of chaotic detection light and the average power of the detection light, a chaos Brillouin optical time domain/coherent domain fusion analysis device and method (Chinese patent: ZL201710848003.4) utilize a pulse modulation method, and the device and method provided by the two patents realize the continuous measurement of the temperature or the strain of a long-distance sensing optical fiber under the condition that the chaotic laser is used as a light source. Because the brillouin frequency shift has the same linear change coefficient with the temperature and the strain, the measurement of the temperature and the strain cannot be simultaneously obtained according to one variable of the brillouin frequency shift. Therefore, the simultaneous measurement of temperature and strain information becomes a bottleneck problem in the development of the current chaotic BOCDA system. A distributed optical fiber sensing system (Chinese patent: ZL201611002982.3) based on the chaotic Brillouin dynamic grating realizes simultaneous detection of temperature and strain by using a method of generating the Brillouin dynamic grating in polarization-maintaining optical fiber by chaotic laser. However, the method for simultaneously measuring the temperature and the strain by using the chaotic brillouin dynamic grating has a complex structure, and a device for generating the brillouin dynamic grating needs to be arranged in a sensing system. Moreover, the effective grating length of the brillouin dynamic grating generated in the polarization maintaining optical fiber is limited, and it is difficult to popularize in practical applications. Therefore, there is a need for a new device and method to solve the problem of measuring temperature and strain simultaneously in the optical fiber sensing system by the chaotic laser.
Disclosure of Invention
The invention overcomes the defects of the prior art, and solves the technical problems that: a device and a method for simultaneously measuring temperature and strain based on chaotic BOCDA are provided to realize simultaneous measurement of temperature and strain.
In order to solve the technical problems, the invention adopts the technical scheme that: a temperature and strain simultaneous measurement device based on chaotic BOCDA comprises a chaotic laser, an optical fiber coupler, a first polarization controller, a first electro-optic modulator, an optical delay generator, a first optical amplifier, an optical scrambler, a sensing optical fiber, a second polarization controller, a second optical amplifier, a signal generator, a second electro-optic modulator, a third optical amplifier, an optical circulator, a filter, a photoelectric detector, a phase-locked amplifier, an arbitrary pulse function generator, a data acquisition card and a calculation unit;
the emergent end of the chaotic laser is connected with the incident end of the optical fiber coupler; the first emergent end of the optical fiber coupler is connected with the incident end of the first polarization controller; the emergent end of the first polarization controller is connected with the light incident end of the first electro-optic modulator; the radio frequency output end of the signal generator is connected with the radio frequency incident end of the first electro-optical modulator; the light emergent end of the first electro-optical modulator is connected with the incident end of the optical delay generator; the emergent end of the optical delay generator is connected with the incident end of the first optical amplifier; the emergent end of the first optical amplifier is connected with the incident end of the optical polarization scrambler; the emergent end of the optical polarization scrambler is connected with one end of the sensing optical fiber; the other end of the sensing optical fiber is connected with the reflection end of the optical circulator;
the second emergent end of the optical fiber coupler is connected with the incident end of the second polarization controller; the emergent end of the second polarization controller is connected with the incident end of the second optical amplifier; the emergent end of the second optical amplifier is connected with the light incident end of the second electro-optic modulator; the radio frequency output end of the random pulse function generator is connected with the radio frequency input ends of the second electro-optical modulator and the phase-locked amplifier and is used for providing a modulation signal for the second electro-optical modulator and a phase-locked reference signal for the phase-locked amplifier; the light emergent end of the second electro-optical modulator is connected with the incident end of the third optical amplifier; the exit end of the third optical amplifier is connected with the incident end of the optical circulator;
the optical signal output by the exit end of the optical circulator is filtered by a filter and then detected by a photoelectric detector; and the calculating unit is used for calculating and obtaining temperature information and strain information of the position of the sensing optical fiber where the stimulated Brillouin scattering effect occurs according to the frequency shifts of the first peak and the second peak in the Brillouin gain spectrum acquired by the data acquisition card.
The radio frequency output end of the signal generator is also connected with the radio frequency input end of the phase-locked amplifier and is used for synchronizing the data sampling process of the phase-locked amplifier with the frequency scanning of the first electro-optical modulator.
The temperature and strain simultaneous measurement device based on the chaotic BOCDA further comprises a first optical isolator and a second optical isolator, wherein the first optical isolator is arranged between the emergent end of the chaotic laser and the incident end of the optical fiber coupler, and the second optical isolator is arranged between the emergent end of the optical deflector and the incident end of the sensing optical fiber.
The sensing optical fiber is a LEAF optical fiber.
The central wavelength of the chaotic laser source is 1550nm, the optical fiber coupler is a 1 × 2 optical fiber coupler, and the coupling ratio of the first emergent end to the second emergent end is 90: 10, the first electro-optical modulator and the second electro-optical modulator adopt AZ-DK5-20-FFU-SFU-LV-SRF1W type intensity modulators, the optical delay generator adopts an ODG-101 high-precision programmable optical delay line, the first optical amplifier, the second optical amplifier and the third optical amplifier adopt erbium-doped optical fiber amplifiers, the optical polarization scrambler adopts a PCD-104 type polarization scrambler, the signal generator adopts an EXG-N5173B type signal source, the filter adopts an XTM-50 bandwidth wavelength adjustable filter, and the photoelectric detector adopts a PM100D detector; the arbitrary pulse function generator is used for sending a pulse signal to the second electro-optical modulator.
The chaotic laser and the optical fiber coupler are connected through a single-mode optical fiber jumper, the optical fiber coupler, the first polarization controller, the first electro-optic modulator, the optical delay generator, the first optical amplifier and the optical polarization scrambler are connected through a single-mode optical fiber jumper, and the optical fiber coupler, the second polarization controller, the second optical amplifier, the second electro-optic modulator and the third optical amplifier are connected through a single-mode optical fiber jumper.
In addition, the invention also provides a temperature and strain simultaneous measurement method based on the chaotic BOCDA, which is realized in the temperature and strain simultaneous measurement device based on the chaotic BOCDA, and specifically comprises the following steps:
s1, building a measuring device and starting the measuring device;
s2, after the noise signal is filtered by the filter, sampling the Stokes light signal detected by the photoelectric detector by the lock-in amplifier, wherein the reference frequency of the lock-in amplifier is the output signal of any pulse function generator;
s3, collecting Brillouin gain spectrum signals through a data acquisition card and sending the Brillouin gain spectrum signals to a calculation unit;
s4, calculating the temperature value and the strain value through a calculation unit, wherein the calculation method comprises the following steps:
identifying a first peak and a second peak from the Brillouin gain spectrum signal, and obtaining the first peak and the second peakBrillouin frequency shift amount of peak two
And
and according to the Brillouin frequency shift quantity of the first peak and the second peak
And
calculating to obtain variation delta T and delta epsilon of temperature and strain; the calculation formula is as follows:
wherein the content of the first and second substances,
the temperature coefficient and the strain coefficient of the first peak Brillouin frequency shift respectively,
the temperature coefficient and the strain coefficient of the Brillouin frequency shift of the second peak are respectively.
The method for simultaneously measuring the temperature and the strain based on the chaotic BOCDA further comprises the steps of measuring and calibrating the temperature coefficient and the strain coefficient of the first peak Brillouin frequency shift
And temperature coefficient and strain coefficient of Brillouin frequency shift of peak two
The step (2).
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a temperature and strain simultaneous measurement device and method based on chaotic BOCDA, which uses a LEAF optical fiber as a sensing optical fiber, and realizes simultaneous measurement of temperature and strain on the premise of ensuring high spatial resolution by utilizing the characteristics that a Brillouin gain spectrum measured in the LEAF optical fiber by a chaotic BOCDA system has multiple peaks and the linearity coefficients of the Brillouin frequency shift of each peak along with the temperature or strain are different.
2. The experimental device is simpler, has larger measurement range and lower cost, and is easier to popularize in practical application.
3. The invention adopts a Brillouin optical correlation domain analysis system, and solves the problem of low spatial resolution in an optical time domain system. Meanwhile, the chaotic laser is used as a light source, so that the performance of the device is further improved, and long-distance optical fiber sensing can be realized on the premise of ensuring the spatial resolution.
Drawings
FIG. 1 is a schematic structural diagram of a temperature and strain simultaneous measurement device based on chaotic BOCDA according to the present invention;
fig. 2 is a graph showing the results of the brillouin gain spectrum in the sensing optical fiber measured according to the embodiment of the present invention as a function of temperature; the corresponding temperatures in the figure are 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃ and 50 ℃ from left to right;
FIG. 3 is a graph showing the results of the changes in the Brillouin gain spectrum in the sensing fiber measured according to the embodiment of the present invention with strain; in the figure, the stresses corresponding to the respective stresses from left to right are 0. mu. epsilon, 100. mu. epsilon, 200. mu. epsilon, 300. mu. epsilon, 400. mu. epsilon, 500. mu. epsilon, 600. mu. epsilon, 700. mu. epsilon, 800. mu. epsilon, 900. mu. epsilon, and 1000. mu. epsilon.
In FIG. 1, 1-chaotic laser, 2-first optical isolator, 3-1 × 2 optical fiber coupler, 4-first polarization controller, 5-first electro-optical modulator, 6-programmable optical delay generator, 7-first optical amplifier, 8-optical polarization scrambler, 9-second optical isolator, 10-sensing optical fiber, 11-second polarization controller, 12-second optical amplifier, 13-signal generator, 14-second electro-optical modulator, 15-third optical amplifier, 16-optical circulator, 17-tunable filter, 18-optical photodetector, 19-phase-locked amplifier, 20-arbitrary pulse function generator, 21-data acquisition card.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, an embodiment of the present invention provides a device for simultaneously measuring temperature and strain based on chaotic BOCDA, which includes a chaotic laser 1, an optical fiber coupler 3, a first polarization controller 4, a first electro-optical modulator 5, an optical delay generator 6, a first optical amplifier 7, an optical scrambler 8, a sensing optical fiber 10, a second polarization controller 11, a second optical amplifier 12, a signal generator 13, a second electro-optical modulator 14, a third optical amplifier 15, an optical circulator 16, a filter 17, a photodetector 18, a lock-in amplifier 19, an arbitrary pulse function generator 20, a data acquisition card 21, and a computing unit; the emergent end of the chaotic laser 1 is connected with the incident end of the optical fiber coupler 3; the first emergent end of the optical fiber coupler 3 is connected with the incident end of the first polarization controller 4; the emergent end of the first polarization controller 4 is connected with the light incident end of the first electro-optical modulator 5; the radio frequency output end of the signal generator 13 is connected with the radio frequency incident end of the first electro-optical modulator 5; the light emergent end of the first electro-optical modulator 5 is connected with the incident end of the optical delay generator 6; the emergent end of the optical delay generator 6 is connected with the incident end of the first optical amplifier 7; the emergent end of the first optical amplifier 7 is connected with the incident end of the optical polarization scrambler 8; the emergent end of the optical polarization scrambler 8 is connected with one end of a sensing optical fiber 10; the other end of the sensing optical fiber 10 is connected with the reflection end of the optical circulator 16; the second emergent end of the first optical fiber coupler 3 is connected with the incident end of the second polarization controller 11; the exit end of the second polarization controller 11 is connected with the entrance end of the second optical amplifier 12; the emergent end of the second optical amplifier 12 is connected with the light incident end of the second electro-optical modulator 14; the radio frequency output end of the arbitrary pulse function generator 20 is connected with the radio frequency input ends of the second electro-optical modulator 14 and the lock-in amplifier 19; the light emitting end of the second electro-optical modulator 14 is connected with the incident end of the third optical amplifier 15; the exit end of the third optical amplifier 15 is connected with the entrance end of the optical circulator 16; the optical signal output by the exit end of the optical circulator 16 is filtered by the filter 17 and then detected by the photoelectric detector 18; the signal output by the photoelectric detector 18 is sampled by the lock-in amplifier 19, and then is subjected to AD conversion by the data acquisition card 21 and then output to the calculation unit, and the calculation unit is used for calculating temperature information and strain information of the position where the stimulated brillouin scattering occurs in the sensing optical fiber 10 according to the frequency shifts of the first peak and the second peak in the brillouin gain spectrum acquired by the data acquisition card 21.
Specifically, as shown in fig. 1, in this embodiment, the rf output terminal of the signal generator 13 is further connected to the rf input terminal of the lock-in amplifier 19, so as to synchronize the data sampling process of the lock-in amplifier 19 with the frequency scanning of the first electro-optical modulator 5.
Specifically, as shown in fig. 1, the device for simultaneously measuring temperature and strain based on the chaotic BOCDA provided by the present embodiment further includes a first optical isolator 2 and a second optical isolator 9, where the first optical isolator 2 is disposed between the exit end of the chaotic laser 1 and the incident end of the optical fiber coupler 3, and the second optical isolator 9 is disposed between the exit end of the optical deflector 8 and the incident end of the sensing optical fiber 10.
Specifically, in this embodiment, the chaotic laser 1, the first optical isolator 2 and the optical fiber coupler 3 are all connected by a single-mode optical fiber jumper, the optical fiber coupler 3, the first polarization controller 4, the first electro-optical modulator 5, the optical delay generator 6, the first optical amplifier 7 and the optical polarization scrambler 8 are connected by a single-mode optical fiber jumper, and the optical fiber coupler 3, the second polarization controller 11, the second optical amplifier 12, the second electro-optical modulator 14 and the third optical amplifier 15 are connected by a single-mode optical fiber jumper. The single-mode optical fiber jumper connection is favorable for building and debugging the optical path, and the optical path testing efficiency is improved.
Specifically, in this example, the sensing fiber is a LEAF fiber.
Specifically, in this embodiment, the center wavelength of the chaotic laser source 1 is 1550nm, the optical fiber coupler 3 is a 1 × 2 optical fiber coupler, and the coupling ratio between the first exit end and the second exit end is 90: 10, the first electro-optical modulator 5 and the second electro-optical modulator 14 adopt AZ-DK5-20-FFU-SFU-LV-SRF1W type intensity modulators, the optical delay generator 6 adopts an ODG-101 high-precision programmable optical delay line, the first optical amplifier 7, the second optical amplifier 12 and the third optical amplifier 15 adopt erbium-doped fiber amplifiers, the optical polarization scrambler 8 adopts a PCD-104 type polarization scrambler, the signal generator 13 adopts an EXG-N5173B type signal source, the filter 17 adopts an XTM-50 bandwidth wavelength adjustable filter, and the photoelectric detector 18 adopts a PM100D detector; the arbitrary pulse function generator 20 is configured to send a pulse signal to the second electro-optical modulator 14, modulate the pump light passing through the second electro-optical modulator 14, and send the pulse signal to the lock-in amplifier 19 to provide a reference frequency for the lock-in amplifier. In this embodiment, the model of any pulse function generator 20 is Agilent 81150 a.
In the embodiment of the invention, the chaotic laser 1 generates chaotic laser with low coherence, so that ultrahigh spatial resolution can be realized. Meanwhile, the used sensing optical fiber is a LEAF optical fiber, the Brillouin gain spectrum of the sensing optical fiber has the characteristic of multiple peaks, and the problem of cross sensitivity of the optical fiber can be solved according to the linear relation between the Brillouin frequency shift of each peak and the temperature and strain.
The working principle of the invention is as follows:
a. the chaotic laser with low coherence generated by the chaotic laser 1 sequentially passes through the first optical isolator 2 and the optical fiber coupler 3, and a light beam is divided into two paths, wherein one path is used as a detection light signal, and the other path is used as a pumping light signal. The detection optical signal passes through a first polarization controller 4, a first electro-optical modulator 5, an optical delay generator 6, a first optical amplifier 7, an optical polarization scrambler 8 and a second optical isolator 9 in sequence to respectively perform polarization state adjustment, modulation, delay, amplification, polarization scrambling and isolation of the optical signal and then enters a sensing optical fiber 10, and the pumping optical signal passes through a second polarization controller 11, a second optical amplifier 12, a second electro-optical modulator 14, a third optical amplifier 15 and an optical circulator 16 in sequence to perform polarization state adjustment, amplification, modulation, re-amplification and circulation of the optical signal and then enters the sensing optical fiber 10;
b. the probe light and the pump light are subjected to stimulated brillouin scattering amplification in the sensing optical fiber 10; the signal enters a filter 17 after passing through an optical circulator 16 to filter out useless signals; the filtered Stokes light signal enters the photoelectric detector 18 and is converted into an electric signal; the electrical signal is sampled by a lock-in amplifier 19; the sampled data is A/D converted by the data acquisition card 21 and then enters the computer, and the computer analyzes the acquired data to obtain the temperature and strain information of the detection light and the pump light at the position where the detection light and the pump light meet in the sensing optical fiber 10.
Further, an embodiment of the present invention further provides a method for simultaneously measuring temperature and strain based on chaotic BOCDA, which is implemented by using the device for simultaneously measuring temperature and strain based on chaotic BOCDA, and specifically includes the following steps:
s1, building a measuring device and starting the measuring device;
s2, after the noise signal is filtered by the filter 17, the Stokes optical signal detected by the photoelectric detector 18 is subjected to phase-locked amplification by the phase-locked amplifier 19, and the phase-locked reference frequency is the output signal of any pulse function generator 20;
s3, collecting Brillouin gain spectrum signals through the data acquisition card 21 and sending the Brillouin gain spectrum signals to the calculation unit;
s4, calculating the temperature value and the strain value through a calculation unit, wherein the calculation method comprises the following steps:
identifying a first peak and a second peak from the Brillouin gain spectrum signal, and obtaining Brillouin frequency shift quantity of the first peak and the second peak
And
and according to the Brillouin frequency shift quantity of the first peak and the second peak
And
the temperature and strain variations Δ T and Δ ∈ were calculated.
The method for simultaneously measuring temperature and strain based on the chaos BOCDA provided by the embodiment is used for simultaneously detecting the temperature and the strain by measuring a multi-peak frequency shift quantity of a LEAF optical fiber brillouin gain spectrum. Specifically, in this embodiment, the first peak and the second peak are selected for measurement, and the relationship between the brillouin frequency shift of the first peak and the second peak and the temperature and the strain is as follows:
the amount of change in temperature and strain can be found from equations (1) and (2) as:
wherein, Delta T and Delta epsilon are respectively the variation of temperature and strain,
and
brillouin frequency shifts of a first peak and a second peak respectively,
respectively the temperature and the strain coefficient of the peak-Brillouin frequency shift,
respectively the temperature and the strain coefficient of the peak two Brillouin frequency shift.
Therefore, after real-time Brillouin gain spectrum signals are obtained through measurement, Brillouin frequency shift quantity according to the first peak and the second peak
And
the amount of change in temperature and strain can be obtained by the equations (3) and (4).
In addition, the method for simultaneously measuring temperature and strain based on chaotic BOCDA of the embodiment further includes measuring and calibrating the temperature coefficient and strain coefficient of the first peak brillouin frequency shift
And temperature coefficient and strain coefficient of Brillouin frequency shift of peak two
The step (2). The specific measurement method can be as follows: the temperature and the strain of the sensing optical fiber are respectively changed, the Brillouin gain spectrum of the sensing optical fiber changing along with the temperature and the strain is obtained, and the temperature coefficient and the strain coefficient of the peak I and the peak II can be obtained by performing linear fitting on Brillouin frequency shift quantities generated by the peak I and the peak II in each Brillouin gain spectrum along with the temperature and the strain respectively.
As shown in fig. 2 and 3, which are the results of the variation of the brillouin shift of the LEAF optical fiber with temperature and the variation with strain measured in the embodiment of the present invention.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A temperature and strain simultaneous measurement device based on chaotic BOCDA comprises a chaotic laser (1), an optical fiber coupler (3), a first polarization controller (4), a first electro-optical modulator (5), an optical delay generator (6), a first optical amplifier (7), an optical polarization scrambler (8), a sensing optical fiber (10), a second polarization controller (11), a second optical amplifier (12), a signal generator (13), a second electro-optical modulator (14), a third optical amplifier (15), an optical circulator (16), a filter (17), a photoelectric detector (18), a lock-in amplifier (19), an arbitrary pulse function generator (20), a data acquisition card (21) and a calculation unit;
the emergent end of the chaotic laser (1) is connected with the incident end of the optical fiber coupler (3); the first emergent end of the optical fiber coupler (3) is connected with the incident end of the first polarization controller (4); the emergent end of the first polarization controller (4) is connected with the light incident end of the first electro-optic modulator (5); the radio frequency output end of the signal generator (13) is connected with the radio frequency incident end of the first electro-optical modulator (5); the light emergent end of the first electro-optical modulator (5) is connected with the incident end of the optical delay generator (6); the emergent end of the optical delay generator (6) is connected with the incident end of the first optical amplifier (7); the emergent end of the first optical amplifier (7) is connected with the incident end of the optical polarization scrambler (8); the emergent end of the optical polarization scrambler (8) is connected with one end of a sensing optical fiber (10); the other end of the sensing optical fiber (10) is connected with the reflection end of the optical circulator (16);
the second emergent end of the optical fiber coupler (3) is connected with the incident end of the second polarization controller (11); the emergent end of the second polarization controller (11) is connected with the incident end of the second optical amplifier (12); the emergent end of the second optical amplifier (12) is connected with the light incident end of the second electro-optical modulator (14); the radio frequency output end of the random pulse function generator (20) is connected with the radio frequency input ends of the second electro-optical modulator (14) and the lock-in amplifier (19) and is used for providing a modulation signal for the second electro-optical modulator (14) and a lock-in reference signal for the lock-in amplifier (19); the light emitting end of the second electro-optical modulator (14) is connected with the incident end of the third optical amplifier (15); the exit end of the third optical amplifier (15) is connected with the entrance end of the optical circulator (16);
an optical signal output by the emergent end of the optical circulator (16) is filtered by a filter (17) and then detected by a photoelectric detector (18); signals output by the photoelectric detector (18) are sampled by the phase-locked amplifier (19), then are subjected to AD conversion by the data acquisition card (21), and then are output to the computing unit, and the computing unit is used for computing and obtaining temperature information and strain information of a position where stimulated Brillouin scattering action occurs in the sensing optical fiber (10) according to frequency shifts of a first peak and a second peak in a Brillouin gain spectrum acquired by the data acquisition card (21).
2. The device for simultaneous measurement of temperature and strain based on chaotic BOCDA according to claim 1, characterized in that the rf output of the signal generator (13) is further connected to the rf input of the lock-in amplifier (19) for synchronizing the data sampling process of the lock-in amplifier (19) with the frequency sweep of the first electro-optical modulator (5).
3. The device for measuring temperature and strain simultaneously based on the BOCDA chaos as claimed in claim 1, further comprising a first optical isolator (2) and a second optical isolator (9), wherein the first optical isolator (2) is arranged between the emergent end of the chaotic laser (1) and the incident end of the fiber coupler (3), and the second optical isolator (9) is arranged between the emergent end of the optical deflector (8) and the incident end of the sensing fiber (10).
4. The device according to claim 1, wherein the sensing fiber is a LEAF fiber.
5. The device for simultaneously measuring temperature and strain based on the chaotic BOCDA according to claim 1, wherein the center wavelength of the chaotic laser (1) is 1550nm, the optical fiber coupler (3) is a 1 x 2 optical fiber coupler, and the coupling ratio of the first emergent end to the second emergent end is 90: the first electro-optical modulator (5) and the second electro-optical modulator (14) adopt AZ-DK5-20-FFU-SFU-LV-SRF1W type intensity modulators, the optical delay generator (6) adopts an ODG-101 high-precision programmable optical delay line, the first optical amplifier (7), the second optical amplifier (12) and the third optical amplifier (15) adopt erbium-doped fiber amplifiers, the optical polarization scrambler (8) adopts a PCD-104 type polarization scrambler, the signal generator (13) adopts an EXG-N5173B type signal source, the filter (17) adopts an XTM-50 bandwidth wavelength tunable filter, and the photoelectric detector (18) adopts a PM100D detector; the arbitrary pulse function generator (20) is used for sending a pulse signal to the second electro-optical modulator (14).
6. The device for measuring the temperature and the strain simultaneously based on the chaotic BOCDA according to claim 1, wherein the chaotic laser (1) and the optical fiber coupler (3) are connected through a single mode fiber jumper, the optical fiber coupler (3), the first polarization controller (4), the first electro-optic modulator (5), the optical delay generator (6), the first optical amplifier (7) and the optical polarization scrambler (8) are connected through a single mode fiber jumper, and the optical fiber coupler (3), the second polarization controller (11), the second optical amplifier (12), the second electro-optic modulator (14) and the third optical amplifier (15) are connected through a single mode fiber jumper.
7. A method for simultaneously measuring temperature and strain based on chaotic BOCDA, which is implemented in the device for simultaneously measuring temperature and strain based on chaotic BOCDA of claim 1, comprising the following steps:
s1, building a measuring device and starting the measuring device;
s2, after the noise signal is filtered by the filter (17), sampling the Stokes light signal detected by the photoelectric detector (18) by the lock-in amplifier (19), wherein the reference frequency of the lock-in amplifier is the output signal of any pulse function generator (20);
s3, collecting Brillouin gain spectrum signals through a data acquisition card (21) and sending the Brillouin gain spectrum signals to a calculation unit;
s4, calculating the temperature value and the strain value through a calculation unit, wherein the calculation method comprises the following steps:
identifying a first peak and a second peak from the Brillouin gain spectrum signal, and obtaining Brillouin frequency shift quantity of the first peak and the second peak
And
and according to the Brillouin frequency shift quantity of the first peak and the second peak
And
calculating the variation of temperature and strain
And
(ii) a The calculation formula is as follows:
wherein the content of the first and second substances,
the temperature coefficient and the strain coefficient of the first peak Brillouin frequency shift respectively,
the temperature coefficient and the strain coefficient of the Brillouin frequency shift of the second peak are respectively.
8. The method for simultaneously measuring temperature and strain based on chaotic BOCDA according to claim 7, further comprising measuring and calibrating the temperature coefficient and strain coefficient of the first peak Brillouin frequency shift
And temperature coefficient and strain coefficient of Brillouin frequency shift of peak two
The step (2).
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