CN113483914B - Chaos BOCDA temperature strain measuring device based on few-mode optical fiber - Google Patents
Chaos BOCDA temperature strain measuring device based on few-mode optical fiber Download PDFInfo
- Publication number
- CN113483914B CN113483914B CN202110570531.4A CN202110570531A CN113483914B CN 113483914 B CN113483914 B CN 113483914B CN 202110570531 A CN202110570531 A CN 202110570531A CN 113483914 B CN113483914 B CN 113483914B
- Authority
- CN
- China
- Prior art keywords
- optical
- mode
- optical fiber
- few
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Optical Transform (AREA)
Abstract
The invention belongs to the technical field of distributed optical fiber sensing, and discloses a chaotic BOCDA (Brillouin optical fiber temperature strain) measurement method and device based on a few-mode optical fiber. The method comprises the following steps: s1, dividing the chaotic laser into a detection light signal and a pumping light signal; s2, making the detecting light signal enter the few-mode optical fiber after optical state adjustment and mode selection; enabling a pump light signal to enter a few-mode fiber from the other end after optical state adjustment and mode selection, and measuring a Stokes light beat frequency signal generated in the few-mode fiber to obtain Brillouin frequency shift quantity; s3, changing the modes of the probe light and the pump light, and repeatedly measuring to obtain Brillouin frequency shift quantity; and S4, calculating the temperature and strain information in the sensing optical fiber according to the measured Brillouin frequency shift quantity.
Description
Technical Field
The invention belongs to the field of distributed optical fiber sensing systems, and particularly relates to a chaotic BOCDA temperature strain measuring device and method based on few-mode optical fibers, which can realize simultaneous measurement of temperature and strain of a distributed optical fiber sensing system.
Background
The distributed optical fiber sensing technology has the characteristics of capability of continuously monitoring disturbance information of any point on an optical fiber, long sensing distance, strong anti-electromagnetic interference capability and the like, so that the distributed optical fiber sensing technology has unique advantages for online real-time monitoring of various important infrastructures in severe environments, such as large buildings, oil and gas pipelines, power lines, bridge tunnels, high-speed railways, civil structures and the like, and has wide application prospects in the aspects of safety and health monitoring, early warning and the like of ultra-long lines in traffic, communication, power, transportation and the like.
Currently, distributed sensing technology based on brillouin scattering has been greatly developed because it has great advantages in sensing distance and spatial resolution, etc., and it has the ability to continuously measure temperature or strain along the optical fiber. The brillouin distributed sensing technology is mainly classified into Brillouin Optical Time Domain Reflectometry (BOTDR), Brillouin Optical Time Domain Analysis (BOTDA), Brillouin Optical Coherent Domain Reflectometry (BOCDR), and Brillouin Optical Coherent Domain Analysis (BOCDA). The strain or temperature positioning of the Brillouin optical time domain reflection system and the Brillouin optical time domain analysis system is realized by determining the flight time of a pulse signal, and although long-distance distributed measurement can be realized, the spatial resolution is only a few meters at most due to the service life limitation of an acoustic phonon, so that the contradiction between the sensing distance and the spatial resolution occurs, and the application of the Brillouin time domain technology in specific engineering is limited. In order to improve the spatial resolution, researchers have proposed a brillouin optical coherence domain reflection technique and a brillouin optical coherence domain analysis technique. The former is based on a spontaneous Brillouin scattering process, and the scattered signal is weaker and the signal-to-noise ratio is lower, so that the measurement technology difficulty is higher. The light source is modulated by the sine signal based on the stimulated Brillouin scattering process, a periodic correlation function of a correlation peak can be formed, temperature or strain measurement is finally completed, and high spatial resolution is achieved while a certain sensing distance is guaranteed.
However, BOCDA systems also fail to fundamentally eliminate the conflict between sensing distance and spatial resolution. The chaotic light source is used for solving the problems, namely a distributed optical fiber sensing device and a distributed optical fiber sensing method for chaotic Brillouin optical coherence domain analysis (Chinese patent: ZL201510531253.6) provide that chaotic laser is used as a detection signal for optical fiber sensing, the problem that sensing distance and spatial resolution cannot be considered in a distributed optical fiber sensing system is successfully solved, and optical fiber sensing with long distance and ultrahigh spatial resolution is realized. In addition, 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, so that the simultaneous measurement of the temperature and the strain information becomes a bottleneck problem in the development of the current chaotic BOCDA system. Therefore, a new device and method are needed to solve the problem of simultaneously measuring temperature and strain in the chaotic BOCDA system.
Disclosure of Invention
The invention overcomes the defects of the prior art, and solves the technical problems that: a chaotic BOCDA temperature strain measuring device and method based on few-mode optical fiber are provided.
In order to solve the technical problems, the invention adopts the technical scheme that: a chaos BOCDA temperature strain measurement method based on few-mode optical fiber comprises the following steps:
s1, dividing the chaotic laser into two paths, wherein one path is used as a detection light signal, and the other path is used as a pumping light signal;
s2, making the detecting light signal enter the few-mode optical fiber after optical state adjustment and mode selection; enabling the pump light signal to enter a few-mode fiber from the other end after optical state adjustment and mode selection, measuring a Stokes light beat frequency signal generated in the few-mode fiber, and analyzing and processing the beat frequency signal to obtain Brillouin frequency shift quantity;
s3, changing the modes of the probe light and the pump light, and repeatedly measuring to obtain Brillouin frequency shift quantity;
and S4, calculating the temperature and strain information in the sensing optical fiber through the Brillouin frequency shift amount measured in the steps S2 and S3.
In step S2, the optical state adjustment of the probe optical signal includes polarization state adjustment, modulation, delay, amplification, polarization disturbance and isolation;
the optical state of the pump light signal is adjusted, the polarization state is adjusted, amplified, modulated and re-amplified.
In step S2, the mode selection of the probe light signal and the pump light signal is implemented by a photon lantern, the input end of the photon lantern is provided with three single-mode fibers as input fibers, the tail fiber of the single-mode fiber is connected with a few-mode fiber, and the three single-mode fibers correspond to each other: three spatial modes, LP01, LP11a, and LP11 b.
The formula for calculating the temperature and strain information in the sensing optical fiber is as follows:
wherein, Delta T and Delta epsilon are respectively the variation of temperature and strain,
and
the Brillouin frequency shift amounts in the combination of LP01-LP01 modes and the combination of LP11a-LP11a modes,
and
the temperature coefficient and the strain coefficient of the brillouin frequency shift in the combination of LP01-LP01 modes,
and
the temperature coefficient and the strain coefficient of brillouin frequency shift in the LP11a-LP11a mode combinations, respectively.
The temperature coefficient of the LP01-LP01 mode combination is 1.01690 MHz/DEG C, and the strain coefficient is: 0.05924 MHz/. mu.epsilon.the temperature coefficient of the LP11a-LP11a mode combination is 0.99099 MHz/. degree.C, and the strain coefficient is: 0.04872 MHz/. mu.epsilon.
In addition, the invention also provides a chaos BOCDA temperature strain measuring device based on few-mode optical fiber, which comprises: the device comprises a chaotic laser, a beam splitter, a first polarization controller, a first electro-optic modulator, a programmable optical delay generator, a first optical amplifier, an optical polarization scrambler, a first photon lantern, a few-mode optical fiber, a second polarization controller, a second optical amplifier, a second electro-optic modulator, a third optical amplifier, an optical circulator, a tunable filter, a photoelectric detector, a phase-locked amplifier, a data acquisition card and a computer;
the chaotic laser generated by the chaotic laser is divided into two paths by the beam splitter, wherein one path is used as a detection light signal, and the other path is used as a pumping light signal;
the detection light signal sequentially passes through a first polarization controller, a first electro-optic modulator, a programmable light delay generator, a first light amplifier and a light polarization scrambler to respectively carry out polarization state adjustment, modulation, delay, amplification and polarization scrambling on the light signal, then enters a first photon lantern, and enters a few-mode optical fiber after being subjected to mode selection by the first photon lantern;
after the pump light signal is subjected to light signal polarization state adjustment, amplification, modulation and re-amplification sequentially through a second polarization controller, a second light amplifier, a second electro-optic modulator and a third light amplifier, the pump light signal is input from a first port of the light circulator, output from a second port of the light circulator enters a second photon lantern, and is incident to the few-mode optical fiber from the other end after mode selection is carried out on the pump light signal through the second photon lantern;
the third port of the optical circulator is connected with the tunable filter and used for outputting a sensing signal in the few-mode optical fiber, and the sensing signal is filtered by the tunable filter and enters the photoelectric detector to be converted into an electric signal; the electric signal is subjected to phase-locked amplification by a phase-locked amplifier and A/D conversion by a data acquisition card and then enters a computer, and the computer analyzes the acquired data to obtain the temperature and strain information of the position of the stimulated Brillouin scattering action of the detection light and the pumping light signal in the sensing optical fiber.
The input end of first photon lantern and second photon lantern has three single mode fiber as input fiber respectively, and three single mode fiber correspond respectively: LP, LPa and LPb.
The chaotic BOCDA temperature strain measuring device based on the few-mode optical fiber further comprises a signal generator and an arbitrary pulse function generator, wherein the output end of the signal generator is respectively connected with the first electro-optical modulator and the phase-locked amplifier, and the output end of the arbitrary pulse function generator is respectively connected with the second electro-optical modulator and the phase-locked amplifier.
The chaotic BOCDA temperature strain measuring device based on the few-mode optical fiber further comprises a first optical isolator and a second optical isolator, wherein the first optical isolator is arranged between the chaotic laser and the beam splitter, and the second optical isolator is arranged between the optical deflector and the first photon lantern.
According to the chaotic BOCDA temperature strain measuring device based on the few-mode optical fiber, a chaotic laser, a first optical isolator and a beam splitter are sequentially connected through a single-mode optical fiber jumper;
the beam splitter, the first polarization controller, the first electro-optic modulator, the programmable optical delay generator, the first optical amplifier, the optical polarization scrambler, the second optical isolator and the first photon lantern are sequentially connected through a single-mode optical fiber jumper;
the beam splitter, the second polarization controller, the second optical amplifier, the second electro-optic modulator, the third optical amplifier, the optical circulator and the second photon lantern are sequentially connected through single-mode optical fiber jumpers;
the optical circulator (), the tunable filter (19) and the photoelectric detector (20) are connected in sequence through a single-mode optical fiber jumper.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a chaotic BOCDA temperature strain measuring device and method based on few-mode optical fibers, which realize simultaneous measurement of temperature and strain and solve the problem of cross sensitivity of the sensing system application.
2. Compared with the prior art that the LEAF optical fiber is adopted as the sensing optical fiber, the invention utilizes the limited orthogonal mode in the few-mode optical fiber as the independent channel to carry out information transmission, realizes the simultaneous measurement of the temperature and the strain according to the difference of the coefficient of linear relation between the Brillouin frequency shift and the temperature and the strain in different modes, can effectively solve the problem of cross sensitivity of the optical fiber temperature and the strain, has higher precision, simpler experimental device, larger measurement range and lower cost, and is easier to popularize in practical application.
Drawings
Fig. 1 is a schematic structural diagram of a device for simultaneously measuring a chaos BOCDA temperature and a strain based on a few-mode optical fiber according to an embodiment of the present invention;
fig. 2 shows brillouin gain spectrograms of four kinds of few-mode optical fibers with different modes of incident light at two ends, i.e., LP01-LP01, LP01-LP01, LP11a-LP11a and LP11a-LP11b, which are experimentally measured in the embodiment of the present invention, and fig. 2 shows that full widths at half maximum under the four different modes are 53.78MHz, 57.54MHz, 57.59MHz and 57.55MHz, respectively.
In the figure 1, 1-chaotic laser, 2-first optical isolator, 3-beam splitter, 4-first polarization controller, 5-first electro-optical modulator, 6-programmable optical delay generator, 7-first optical amplifier, 8-optical scrambler, 9-second optical isolator, 10-first photon lantern, 11-sensing optical fiber, 12-second photon lantern, 13-second polarization controller, 14-second optical amplifier, 15-signal generator, 16-second electro-optical modulator, 17-third optical amplifier, 18-optical circulator, 19-tunable optical filter, 20-photoelectric detector, 21-arbitrary pulse function generator, 22-phase-locked amplifier and 23-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.
Example one
As shown in fig. 1, an embodiment of the present invention provides a chaotic BOCDA temperature strain measurement device based on a few-mode optical fiber, including: the device comprises a chaotic laser 1, a first optical isolator 2, a beam splitter 3, a first polarization controller 4, a first electro-optic modulator 5, a programmable optical delay generator 6, a first optical amplifier 7, an optical polarization scrambler 8, a second optical isolator 9, a first photon lantern 10, a few-mode optical fiber 11, a second polarization controller 13, a second optical amplifier 14, a second electro-optic modulator 16, a third optical amplifier 17, an optical circulator 18, a tunable filter 19, a photoelectric detector 20, a phase-locked amplifier 22, a data acquisition card 23 and a computer.
The chaotic laser with low coherence generated by the chaotic laser 1 is divided into two paths by the beam splitter 3 after passing through the first optical isolator 2, wherein one path is used as a detection light signal, and the other path is used as a pumping light signal.
The detection light signal sequentially passes through a first polarization controller 4, a first electro-optic modulator 5, a programmable light delay generator 6, a first light amplifier 7, a light polarization scrambler 8 and a second light isolator 9 to respectively perform polarization state adjustment, modulation, delay, amplification, polarization scrambling and isolation of the light signal, enters a first photon lantern 10, and enters a few-mode optical fiber 11 after mode selection is performed on the first photon lantern 10.
After the optical signal polarization state adjustment, amplification, modulation and re-amplification are sequentially performed on the pump optical signal through the second polarization controller 13, the second optical amplifier 14, the second electro-optical modulator 16 and the third optical amplifier 17, the pump optical signal is input from the first port of the optical circulator 18, output from the second port enters the second photon lantern 12, and enters the few-mode optical fiber 11 from the other end after mode selection is performed on the pump optical signal through the second photon lantern 12.
The detection light signal and the pump light signal generate stimulated brillouin scattering in the sensing optical fiber 11 and generate stokes light, the stokes light and the pump light signal generate interference beat frequency effect, and the generated beat frequency signal is the sensing signal. After being output from the few-mode optical fiber 11, the sensing signal returns to the optical circulator 18 through the second photon lantern 12, is output from a third port of the optical circulator 18, is filtered by the tunable filter 19, and enters the photoelectric detector 20 to be converted into an electric signal; the electrical signal is phase-locked and amplified by the phase-locked amplifier 22, the data acquisition card 23 performs A/D conversion and then enters the computer, and the computer analyzes the acquired data to obtain the temperature and strain information of the position where the detection light and the pump light signal generate the stimulated Brillouin scattering effect in the sensing fiber 11.
Specifically, the chaotic BOCDA temperature strain measurement device based on the few-mode optical fiber further includes a signal generator 15 and an arbitrary pulse function generator 21, an output end of the signal generator 15 is connected to the first electro-optical modulator 5 and the lock-in amplifier 22, respectively, and an output end of the arbitrary pulse function generator 21 is connected to the second electro-optical modulator 16 and the lock-in amplifier 22, respectively. The signal generator 15 is configured to drive the first electro-optical modulator 5 to modulate the probe optical signal, and the arbitrary pulse function generator 21 is configured to drive the second electro-optical modulator 16 to pulse-modulate the probe optical signal. The modulated signals from the signal generator 15 and the arbitrary pulse function generator 21 are also sent to a lock-in amplifier, and the detected electric signals are subjected to lock-in amplification processing.
Specifically, in this embodiment, three single-mode fibers are respectively provided at the input ends of the first photon lantern 10 and the second photon lantern 12 as input fibers, and input light enters different input fibers and then exits into the few-mode sensing fiber 11 through a single-mode pigtail. In this embodiment, the core structure of the few-mode fiber is step-type, and the inner cladding is doped with fluorine (F) with a certain concentration, which has a fixed radius of the core and the cladding and a refractive index, so that the propagation mode of the few-mode fiber is determined. Due to the existence of degenerate modes, in fact, three spatial modes exist for a two-mode step fiber: LP01, LP11a, and LP11 b. Therefore, in the present embodiment, the first photon lantern 10 and the second photon lantern 12 having three single mode fibers at the input end are connected to the few-mode fiber, and the three single mode fibers respectively correspond to: the three spatial modes LP01, LP11a and LP11b can convert the fundamental mode in the single-mode fiber into corresponding different modes in the few-mode fiber, thereby realizing mode selection. That is, by coupling the probe light and the pump light into different input fibers of the photonic lantern at two ends of the sensing fiber, mode selection can be performed on the probe light and the pump light, so that different combinations based on the three spatial modes, namely, four mode combinations of LP01-LP01, LP11a-LP11a, LP01-LP11, and LP11a-LP11b, are obtained. The LP01-LP01 modes represent that the probe light is switched into the LP01 mode, and the pump light is switched into the LP01 mode; the LP11a-LP11a modes represent probe light access LP11a mode, and pump light access LP11a mode; the modes LP01-LP11 represent that the probe light is switched into the mode LP01, and the pump light is switched into the modes LP11a or LP11 b; the LP11a-LP11b modes indicate that the probe light is switched into the LP11a mode and the pump light is switched into the LP11b mode.
Specifically, in this embodiment, the chaotic laser 1, the first optical isolator 2, and the beam splitter 3 are connected in sequence by a single-mode optical fiber jumper; the beam splitter 3, the first polarization controller 4, the first electro-optic modulator 5, the programmable optical delay generator 6, the first optical amplifier 7, the optical polarization scrambler 8, the second optical isolator 9 and the first photon lantern 10 are sequentially connected through a single-mode optical fiber jumper; the beam splitter 3, the second polarization controller 13, the second optical amplifier 14, the second electro-optical modulator 16, the third optical amplifier 17, the optical circulator 18 and the second photon lantern 12 are sequentially connected through a single-mode optical fiber jumper; the optical circulator 18, the tunable filter 19 and the photoelectric detector 20 are connected in sequence through a single-mode optical fiber jumper.
In the specific implementation, the central wavelength of the chaotic laser source is 1550nm, the beam splitter 3 adopts a 1x2 optical fiber coupler, the coupling ratio is 90:10 (detection light path: pumping light path), the first electro-optical modulator 5 and the second electro-optical modulator 16 adopt AZ-DK5-20-FFU-SFU-LV-SRF1W type intensity modulators, the programmable optical delay generator 6 adopts an ODG-101 high-precision programmable optical delay line, the first optical amplifier 7, the second optical amplifier 14 and the third optical amplifier 17 adopt erbium-doped fiber amplifiers, the optical polarization scrambler 8 adopts a PCD-104 type polarization scrambler, the sensing fiber 11 adopts a few-mode fiber, the length of which is 10km, the signal generator 15 adopts an EXG-N5173B type signal source, the tunable filter 19 is an XTM-50 bandwidth wavelength tunable filter, and the photodetector 20 is a PM100D detector.
The embodiment provides a chaotic BOCDA temperature strain measuring device based on a few-mode optical fiber, which can measure the frequency shift quantity of a Brillouin gain spectrum by changing the mode combination of incident light at two ends of the few-mode optical fiber so as to realize simultaneous detection of temperature and strain.
In this embodiment, mode selection is performed on probe light and pump light through two photon lanterns, and brillouin frequency shift measurement is performed through two different modes (LP01-LP01 mode combination and LP11a-LP11a mode combination), that is, temperature and strain information in a few-mode fiber can be demodulated simultaneously.
The relationship between brillouin frequency shift and temperature and strain in the combination of LP01-LP01 modes and the combination of LP11a-LP11a modes is:
from equations (1) and (2), the amount of change in temperature and strain is:
wherein, Delta T and Delta epsilon are respectively the variation of temperature and strain,
and
brillouin frequency shifts in the LP01-LP01 mode combination and the LP11a-LP11a mode combination respectively,
and
the temperature coefficient and the strain coefficient of the brillouin frequency shift in the combination of LP01-LP01 modes,
and
the temperature coefficient and the strain coefficient of brillouin frequency shift in the LP11a-LP11a mode combinations, respectively.
Through experimental measurement, the temperature and strain coefficients of the combination of LP01-LP01 mode and the combination of LP11a-LP11a mode are shown in Table 1, and the Brillouin gain spectra of the combination of LP01-LP01, LP01-LP11, LP11a-LP11a and LP11a-LP11b in four different modes are shown in FIG. 2.
TABLE 1 experimentally measured temperature and strain coefficients for the combination of LP01-LP01 and LP11a-LP11a modes obtained
From table 1, values of Δ T and Δ ∈ can be calculated from brillouin frequency shifts obtained by substituting equations (3) and (4) with combinations of LP01 to LP01 modes and LP11a to LP11a modes. According to the simulation results, the Δ T and Δ ε were calculated to be 24.8 ℃ and 1003.5 μ ε, respectively, in the obtained Brillouin frequency shifts 84.7MHz and 73.5MHz equations. The temperature error and the strain error are respectively 0.2 ℃ and 3.5 mu epsilon, which are very close to the actual set temperature and strain changes.
Example two
The embodiment of the invention provides a chaotic BOCDA temperature strain measurement method based on a few-mode optical fiber, which comprises the following steps:
s1, dividing the chaotic laser into two paths, wherein one path is used as a detection light signal, and the other path is used as a pumping light signal;
s2, making the detecting light signal enter the few-mode optical fiber 11 after the optical state adjustment and the mode selection; enabling the pump light signal to enter the few-mode fiber 11 from the other end after optical state adjustment and mode selection, measuring a Stokes light beat frequency signal generated in the few-mode fiber 11, and analyzing and processing the beat frequency signal to obtain Brillouin frequency shift quantity;
s3, changing the modes of the probe light and the pump light, and repeatedly measuring to obtain Brillouin frequency shift quantity;
and S4, calculating the temperature and strain information in the sensing optical fiber through the Brillouin frequency shift amount measured in the steps S2 and S3.
Specifically, in step S2, the optical state adjustment of the probe optical signal includes polarization state adjustment, modulation, delay, amplification, polarization disturbance and isolation; the optical state of the pump light signal is adjusted, the polarization state is adjusted, amplified, modulated and re-amplified. The polarization state adjustment, modulation, delay, amplification, polarization disturbance and isolation of the light beam are respectively realized by a polarization controller, a modulator, an optical delay generator, an optical amplifier, an optical polarization winder and an optical isolator.
Specifically, in step S2, the mode selection of the probe light signal and the pump light signal is implemented by a photon lantern, three single-mode fibers are respectively provided at an input end of the photon lantern as input fibers, a pigtail of the single-mode fiber is connected with the few-mode fiber 11, and the three single-mode fibers respectively correspond to: three spatial modes, LP01, LP11a, and LP11 b.
In summary, the invention provides a chaotic BOCDA temperature strain measurement method and device based on a few-mode fiber, which can realize ultrahigh spatial resolution based on low-coherence chaotic laser, use a sensing fiber as the few-mode fiber, use a limited orthogonal mode in the few-mode fiber as an independent channel for information transmission, realize simultaneous measurement of temperature and strain according to different linear relation coefficients of brillouin frequency shift and temperature and strain in different modes, can effectively solve the problem of cross sensitivity of fiber temperature and strain, and have the advantages of higher precision, simpler experimental device, larger measurement range, lower cost and easier popularization in practical application.
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 (9)
1. A chaos BOCDA temperature strain measuring device based on few-mode optical fiber is characterized by comprising: the device comprises a chaotic laser (1), a beam splitter (3), a first polarization controller (4), a first electro-optic modulator (5), a programmable optical delay generator (6), a first optical amplifier (7), an optical polarization scrambler (8), a first photon lantern (10), a few-mode optical fiber (11), a second polarization controller (13), a second optical amplifier (14), a second electro-optic modulator (16), a third optical amplifier (17), an optical circulator (18), a tunable filter (19), a photoelectric detector (20), a phase-locked amplifier (22), a data acquisition card (23) and a computer;
the chaotic laser generated by the chaotic laser (1) is divided into two paths by the beam splitter (3), wherein one path is used as a detection light signal, and the other path is used as a pumping light signal;
the detection light signal sequentially passes through a first polarization controller (4), a first electro-optic modulator (5), a programmable light delay generator (6), a first light amplifier (7) and a light polarization scrambler (8) to respectively carry out polarization state adjustment, modulation, delay, amplification and polarization scrambling on the light signal, then enters a first photon lantern (10), and enters a few-mode optical fiber (11) after mode selection is carried out on the first photon lantern (10); after the pump light signals are subjected to light signal polarization state adjustment, amplification, modulation and re-amplification sequentially through a second polarization controller (13), a second light amplifier (14), a second electro-optic modulator (16) and a third light amplifier (17), the pump light signals are input from a first port of a light circulator (18), output from a second port enters a second photon lantern (12), and are subjected to mode selection through the second photon lantern (12) and then enter a few-mode optical fiber (11) from the other end;
a third port of the optical circulator (18) is connected with the tunable filter (19) and is used for outputting a sensing signal in the few-mode optical fiber (11), and the sensing signal enters the photoelectric detector (20) after being filtered by the tunable filter (19) and is converted into an electric signal; the electric signal is subjected to phase-locked amplification through a phase-locked amplifier (22) in sequence, and is subjected to A/D conversion through a data acquisition card (23) and then enters a computer, and the computer analyzes the acquired data to obtain temperature and strain information of the position where the detection light and the pumping light signal generate stimulated Brillouin scattering in the sensing optical fiber (11);
the calculation formula of the temperature and strain information is as follows:
wherein, Delta T and Delta epsilon are respectively the variation of temperature and strain,
and
the Brillouin frequency shift amounts in the combination of LP01-LP01 modes and the combination of LP11a-LP11a modes,
and
the temperature coefficient and the strain coefficient of the brillouin frequency shift in the combination of LP01-LP01 modes,
and
the temperature coefficient and the strain coefficient of brillouin frequency shift in the LP11a-LP11a mode combinations, respectively.
2. The chaotic BOCDA temperature strain measuring device based on few-mode optical fiber according to claim 1, wherein the input ends of the first photon lantern (10) and the second photon lantern (12) respectively have three single-mode optical fibers as input optical fibers, and the three single-mode optical fibers respectively correspond to the input optical fibers: three spatial modes, LP01, LP11a, and LP11 b.
3. The chaotic BOCDA temperature strain measuring device based on the few-mode optical fiber is characterized by further comprising a signal generator (15) and an arbitrary pulse function generator (21), wherein the output end of the signal generator (15) is respectively connected with the first electro-optical modulator (5) and the lock-in amplifier (22), and the output end of the arbitrary pulse function generator (21) is respectively connected with the second electro-optical modulator (16) and the lock-in amplifier (22).
4. The chaotic BOCDA temperature strain measuring device based on the few-mode optical fiber is characterized by further comprising a first optical isolator (2) and a second optical isolator (9), wherein the first optical isolator (2) is arranged between the chaotic laser (1) and the beam splitter (3), and the second optical isolator (9) is arranged between the optical deflector (8) and the first photon lantern (10).
5. The chaotic BOCDA temperature strain measuring device based on the few-mode optical fiber is characterized in that the chaotic laser (1), the first optical isolator (2) and the beam splitter (3) are sequentially connected through a single-mode optical fiber jumper wire;
the beam splitter (3), the first polarization controller (4), the first electro-optic modulator (5), the programmable optical delay generator (6), the first optical amplifier (7), the optical polarization scrambler (8), the second optical isolator (9) and the first photon lantern (10) are sequentially connected through a single-mode optical fiber jumper;
the beam splitter (3), the second polarization controller (13), the second optical amplifier (14), the second electro-optic modulator (16), the third optical amplifier (17), the optical circulator (18) and the second photon lantern (12) are sequentially connected through single-mode optical fiber jumpers;
the optical circulator (18), the tunable filter (19) and the photoelectric detector (20) are connected in sequence through single-mode optical fiber jumpers.
6. A chaotic BOCDA temperature strain measurement method based on few-mode optical fiber is realized by the device of any one of claims 1-5, and is characterized by comprising the following steps:
s1, dividing the chaotic laser into two paths, wherein one path is used as a detection light signal, and the other path is used as a pumping light signal;
s2, the detection light signal is made to enter the few-mode optical fiber (11) after the optical state adjustment and the mode selection; enabling the pump light signals to enter a few-mode optical fiber (11) from the other end after optical state adjustment and mode selection, measuring Stokes light beat frequency signals generated in the few-mode optical fiber (11), and analyzing and processing the beat frequency signals to obtain Brillouin frequency shift quantity;
s3, changing the modes of the probe light and the pump light, and repeatedly measuring to obtain Brillouin frequency shift quantity;
and S4, calculating the temperature and strain information in the sensing optical fiber through the Brillouin frequency shift amount measured in the steps S2 and S3.
7. The method according to claim 6, wherein in step S2, the optical state adjustment of the probe optical signal includes polarization state adjustment, modulation, delay, amplification, polarization disturbance and isolation;
the optical state adjustment of the pump light signal comprises polarization state adjustment, amplification, modulation and re-amplification.
8. The method for measuring chaotic BOCDA temperature strain based on few-mode fiber according to claim 6, wherein in step S2, the mode selection of the probe optical signal and the pump optical signal is implemented by a photon lantern.
9. The chaotic BOCDA temperature strain measurement method based on the few-mode optical fiber as claimed in claim 6, wherein the temperature coefficient of the LP01-LP01 mode combination is 1.01690MHz/° C, and the strain coefficient is: 0.05924 MHz/. mu.epsilon.the temperature coefficient of the LP11a-LP11a mode combination is 0.99099 MHz/. degree.C, and the strain coefficient is: 0.04872 MHz/. mu.epsilon.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110570531.4A CN113483914B (en) | 2021-05-25 | 2021-05-25 | Chaos BOCDA temperature strain measuring device based on few-mode optical fiber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110570531.4A CN113483914B (en) | 2021-05-25 | 2021-05-25 | Chaos BOCDA temperature strain measuring device based on few-mode optical fiber |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113483914A CN113483914A (en) | 2021-10-08 |
| CN113483914B true CN113483914B (en) | 2022-06-14 |
Family
ID=77933669
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110570531.4A Active CN113483914B (en) | 2021-05-25 | 2021-05-25 | Chaos BOCDA temperature strain measuring device based on few-mode optical fiber |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113483914B (en) |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102322806B (en) * | 2011-08-01 | 2013-08-07 | 杭州欧忆光电科技有限公司 | Brillouin optical time domain analyzer relevant to chaotic laser |
| WO2013020286A1 (en) * | 2011-08-10 | 2013-02-14 | 中国计量学院 | Chaotic laser-related fully distributed optical fiber raman and rayleigh photon sensor |
| WO2013020276A1 (en) * | 2011-08-10 | 2013-02-14 | 中国计量学院 | Brillouin optical time domain analyzer of chaotic laser-related integrated optical fiber raman amplifier |
| CN105136178B (en) * | 2015-08-27 | 2017-09-05 | 太原理工大学 | The distribution type optical fiber sensing equipment and method of the relevant domain analysis of chaos Brillouin light |
| CN105136177B (en) * | 2015-08-27 | 2017-09-05 | 太原理工大学 | The distribution type optical fiber sensing equipment and method of a kind of submillimeter spatial resolution |
| CN105783762B (en) * | 2016-05-10 | 2018-04-06 | 太原理工大学 | The brillouin distributed optical fiber sensing device and method of chaos correlation method positioning |
| CN105784195B (en) * | 2016-05-10 | 2018-04-06 | 太原理工大学 | The distribution type optical fiber sensing equipment and method of single-ended chaos Brillouin optical time domain analysis |
| CN111141414B (en) * | 2019-12-27 | 2021-02-02 | 太原理工大学 | Temperature and strain simultaneous measurement device and method based on chaos BOCDA |
-
2021
- 2021-05-25 CN CN202110570531.4A patent/CN113483914B/en active Active
Non-Patent Citations (3)
| Title |
|---|
| 基于正交偏振控制的布里渊光时域分析长距离分布式光纤传感器;宋牟平等;《中国激光》;20100310;第37卷(第03期);758-762 * |
| 折射率不敏感的级联型单模-少模-单模光纤温度传感器;付兴虎等;《光谱学与光谱分析》;20161115;第36卷(第11期);3726-3731 * |
| 结合布里渊光时域分析和光时域反射计的分布式光纤传感器;宋牟平等;《光学学报》;20100315;第30卷(第03期);650-654 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113483914A (en) | 2021-10-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Li et al. | Physics and applications of Raman distributed optical fiber sensing | |
| Li et al. | Few-mode fiber based optical sensors | |
| CN105136177B (en) | The distribution type optical fiber sensing equipment and method of a kind of submillimeter spatial resolution | |
| CN110375800B (en) | Sensing device and method based on super-continuum spectrum Brillouin optical time domain analyzer | |
| CN101634571B (en) | Optical pulse raster distributed fiber sensing device | |
| CN108844614B (en) | Chaotic Brillouin optical correlation domain analysis system and method based on phase spectrum measurement | |
| CN109959403B (en) | Multi-parameter large-capacity sensing system | |
| KR101633954B1 (en) | System for improving the dynamic range and reducing measurement uncertainty in fibre optic distributed sensors and fibre optic distributed measurement equipment | |
| CN104697558A (en) | Distributed optical fiber multi-parameter sensing measurement system | |
| CN108801305B (en) | Method and device of Brillouin optical time domain reflectometer based on step pulse self-amplification | |
| CN110243493A (en) | Brillouin optical time-domain reflectometer device and method based on super continuous spectrums | |
| CN104111086A (en) | Low-Brillouin scattering threshold sensing fiber-based optical time domain reflectometer device and method | |
| CN110726468B (en) | Distributed optical fiber acoustic wave sensing system based on straight waveguide phase modulator | |
| CN111220284A (en) | Laser line width measuring system and method based on short delay self-homodyne coherent envelope | |
| CN113804412B (en) | Micro-chromatic dispersion measuring device of optical fiber device based on annular light path structure | |
| Huang et al. | Single-end hybrid Rayleigh Brillouin and Raman distributed fibre-optic sensing system | |
| CN111141414B (en) | Temperature and strain simultaneous measurement device and method based on chaos BOCDA | |
| Sheng et al. | Distributed Fiberoptic Sensor for Simultaneous Temperature and Strain Monitoring Based on Brillouin Scattering Effect in Polyimide‐Coated Fibers | |
| Wang et al. | Single-few-single mode fiber structure for simultaneous measurement for curvature and temperature assisted by intensity-correlated pulse twin beams | |
| CN113483914B (en) | Chaos BOCDA temperature strain measuring device based on few-mode optical fiber | |
| Li et al. | A bend-tolerant BOTDR distributed fiber sensor | |
| Hu et al. | Simultaneous measurement of distributed temperature and strain through Brillouin frequency shift using a common communication optical fiber | |
| CN108844615B (en) | Distributed optical fiber sensing device and method based on chaotic Brillouin phase spectrum measurement | |
| CN216524011U (en) | Long-distance Brillouin optical time domain reflectometer monitoring device | |
| Xu et al. | Bending-loss-resistant distributed temperature and strain discriminative Brillouin sensor based on 98 mol% germania-doped few-mode fiber |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |