CN110440851B - Long-distance multi-parameter measuring device and method based on Brillouin and Raman scattering - Google Patents
Long-distance multi-parameter measuring device and method based on Brillouin and Raman scattering Download PDFInfo
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- CN110440851B CN110440851B CN201910604419.0A CN201910604419A CN110440851B CN 110440851 B CN110440851 B CN 110440851B CN 201910604419 A CN201910604419 A CN 201910604419A CN 110440851 B CN110440851 B CN 110440851B
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Abstract
The invention discloses a long-distance multi-parameter measuring device based on Brillouin and Raman scattering, which comprises a semiconductor laser 1, a first 1 x 2 optical fiber coupler 2, an optical fiber polarization controller 3, a high-speed electro-optical modulator 4, a microwave signal source 5, a second 1 x 2 optical fiber coupler 6, an optical polarization scrambler 7, an optical switch 8, a third 1 x 2 optical fiber coupler 9, a band-pass filter 10, a first erbium-doped optical fiber amplifier 11, a first optical circulator 12 and a first optical fiber grating 13, the device comprises a sensing fiber 14, a semiconductor optical amplifier 15, a second erbium-doped fiber amplifier 16, a second optical circulator 17, a second fiber grating 18, a third optical circulator 19, a wavelength division multiplexer 20, a first avalanche photodiode 21, a photodetector 22, a second avalanche photodiode 23, a first signal amplifier 24, a second signal amplifier 25 and a data acquisition and processing system 26. The invention effectively solves the problems that the cross sensitivity and the long-distance and high-precision measurement among a plurality of measured parameters of the existing distributed optical fiber sensing system can not be considered at the same time.
Description
Technical Field
The invention relates to the field of distributed optical fiber sensing, in particular to a long-distance multi-parameter measuring device and method based on Brillouin and Raman scattering.
Background
The distributed optical fiber sensing has the advantages of electromagnetic interference resistance, good electrical insulation and good corrosion resistance, can realize continuous measurement of a plurality of parameters along the sensing optical fiber, and the like, and shows unique application prospect in the application of various fields of petrochemical industry, aerospace, bridge and tunnel, large-scale basic building structure health monitoring and the like.
Distributed optical fiber sensing based on the optical scattering effect obtains information such as temperature and strain at each position of an optical fiber by detecting backscattered light (raman scattering or brillouin scattering) generated when an incident optical pulse is transmitted in the optical fiber. The Brillouin Optical Time Domain system is divided into Brillouin Optical Time Domain Reflectometry (BOTDR) which is based on the spontaneous Brillouin scattering effect of an Optical fiber and Brillouin Optical Time Domain Analysis (BOTDA) which is based on the stimulated Brillouin scattering effect of an Optical fiber. The BOTDA technology has a longer sensing distance relative to the BOTDR technology. Because the brillouin scattering light is sensitive to both temperature and strain, a two-parameter measurement can be performed, but because of the simultaneous sensitivity, the cross-sensitivity problem is also caused. A distributed optical fiber Raman time domain reflectometer (ROTDR) is a sensing system which is realized by utilizing the spontaneous Raman scattering effect in optical fibers and combining an optical time domain reflection technology and can be used for measuring the distribution of a space temperature field in a distributed, continuous and real-time manner. The Raman scattering light intensity is mainly influenced by temperature, so that the cross sensitivity problem does not exist, and the temperature measurement can be carried out. Therefore, although the change of parameters along the optical fiber can be measured in the traditional Brillouin scattering and Raman scattering distributed optical fiber sensing system, the simultaneous measurement of multiple parameters cannot be realized, and thus the multiple parameter measurement becomes a research hotspot in the field.
Both pulsed light and continuous light have energy losses during their propagation in optical fibers, and some energy compensation is required to increase the sensing distance, such as Distributed Raman Amplification (DRA) and Distributed Brillouin Amplification (DBA). The gain bandwidth of the DRA sensing system is very wide, but the gain coefficient is small, the required pump power is high (W level), the efficiency is low, and an optical fiber connector is easy to burn out, while the gain coefficient of the DBA sensing system is large, the required pump power is low (mW level), and the efficiency is high. For example, Alayn loyssa et al, university of navala, spain, utilizes a DBA optical signal to perform compensation amplification on pump light, so that the pump light power is amplified by 9.2 dB at the tail fiber of a 50 km sensing fiber, the signal-to-noise ratio is improved by 12.5 dB to the maximum (OPTICS EXPRESS, 2015, vol. 23, number 23, 30448) in the system, but in the system, a laser source independent of brillouin pulses and continuous light is used as a DBA pump, and triangular wave modulation frequency scanning is performed on the DBA pump, so that the device is complex, the measurement time is long, and in the invention, high-frequency sidebands filtered in a detection path of a traditional BOTDA system are effectively utilized, and stimulated brillouin effect is generated in the sensing fiber together with reverse pump light, so that the pump light is synchronously amplified on line. The extra complex modulation is avoided, the cost device of the system is reduced, the structure is simpler, and the measuring time is shorter.
At present, the development and application of long-distance distributed sensing are greatly restricted by the contradiction between the measuring distance and the spatial resolution in the long-distance sensing process. Because the spatial resolution in the traditional BOTDA system is limited by the pulse width (the pulse width is limited by the phonon life), 1m is difficult to break through, and the spatial resolution in the sensing pulse system adopting the differential pulse pair is determined by the pulse width difference and the rising and falling edge time. For example, Bao Xiao Ying et al, Ottawa university, Canada, implemented 0.18m spatial resolution (50/49 ns) and 0.15m spatial resolution (20/19 ns) on 1km sensing fiber using differential pulse pairs (OPTICS EXPRESS, 2008, Vol. 16, number 26, 21616-.
Based on the above description, the conventional distributed optical fiber sensing system has the problem that cross sensitivity and long-distance and high-precision measurement among multiple measured parameters cannot be considered, so that it is necessary to invent a brand-new distributed optical fiber sensing system capable of performing multi-parameter measurement and long-distance and high spatial resolution.
Disclosure of Invention
The invention provides a long-distance multi-parameter measuring device and method based on Brillouin and Raman scattering, aiming at solving the problem that cross sensitivity and long-distance and high-precision measurement among multiple measured parameters of the existing distributed optical fiber sensing system cannot be considered at the same time.
The invention is realized by adopting the following technical scheme:
a long-distance multi-parameter measuring device based on Brillouin and Raman scattering comprises a semiconductor laser, a first 1 x 2 optical fiber coupler, an optical fiber polarization controller, a high-speed electro-optic modulator, a microwave signal source, a second 1 x 2 optical fiber coupler, an optical deflector, an optical switch, a third 1 x 2 optical fiber coupler, a band-pass filter, a first erbium-doped optical fiber amplifier, a first optical circulator, a first optical fiber grating, a sensing optical fiber, a semiconductor optical amplifier, a second erbium-doped optical fiber amplifier, a second optical circulator, a second optical fiber grating, a third optical circulator, a wavelength division multiplexer, a first avalanche photodiode, a photoelectric detector, a second avalanche photodiode, a first signal amplifier, a second signal amplifier and a data acquisition and processing system.
The emergent end of the semiconductor laser is connected with the incident end of the first 1 multiplied by 2 optical fiber coupler.
The first emergent end of the first 1 x 2 optical fiber coupler is connected with the incident end of the optical fiber polarization controller, the emergent end of the optical fiber polarization controller is connected with the incident end of the high-speed electro-optical modulator, the output end of the microwave signal source is connected with the input end of the high-speed electro-optical modulator, and the emergent end of the high-speed electro-optical modulator is connected with the incident end of the second 1 x 2 optical fiber coupler.
The first emergent end of the second 1 x 2 optical fiber coupler is connected with the incident end of the optical polarization scrambler, the emergent end of the optical polarization scrambler is connected with the incident end of the optical switch, and the emergent end of the optical switch is connected with one incident end of the third 1 x 2 optical fiber coupler.
The second exit end of the second 1 × 2 optical fiber coupler is connected with the incident end of the band-pass filter, the exit end of the band-pass filter is connected with the incident end of the first erbium-doped optical fiber amplifier, the exit end of the first erbium-doped optical fiber amplifier is connected with the incident end of the first optical circulator, the reflection end of the first optical circulator is connected with the first optical fiber grating, the exit end of the first optical circulator is connected with the other incident end of the third 1 × 2 optical fiber coupler, and the exit end of the third 1 × 2 optical fiber coupler is connected with one end of the sensing optical fiber.
The second emergent end of the first 1X 2 optical fiber coupler is connected with the incident end of the semiconductor optical amplifier, the emergent end of the semiconductor optical amplifier is connected with the incident end of the second erbium-doped optical fiber amplifier, the emergent end of the second erbium-doped optical fiber amplifier is connected with the incident end of the second optical circulator, the reflecting end of the second optical circulator is connected with the second optical fiber grating, the emergent end of the second optical circulator is connected with the incident end of the third optical circulator, and the reflecting end of the third optical circulator is connected with the other end of the sensing optical fiber.
The exit end of the third optical circulator is connected with the incident end of the wavelength division multiplexer, the first exit end of the wavelength division multiplexer is connected with the incident end of the first avalanche photodiode, the output end of the first avalanche photodiode is connected with the input end of the first signal amplifier, the output end of the first signal amplifier is connected with the data acquisition and processing system, the second exit end of the wavelength division multiplexer is connected with the incident end of the photoelectric detector, the output end of the photoelectric detector is connected with the data acquisition and processing system, the third exit end of the wavelength division multiplexer is connected with the incident end of the second avalanche photodiode, the output end of the second avalanche photodiode is connected with the input end of the second signal amplifier, and the output end of the second signal amplifier is connected with the data acquisition and processing system.
A long-distance multi-parameter measuring method based on Brillouin and Raman scattering (the method is realized in the long-distance multi-parameter measuring device based on Brillouin and Raman scattering), which is realized by adopting the following steps:
A. laser emitted by the semiconductor laser 1 is divided into two paths through a first 1 x 2 optical fiber coupler: the first path of laser is used as a detection optical signal and a pumping compensation optical signal, and the second path of laser is used as a pumping optical signal. The first path of laser signal firstly passes through an optical fiber polarization controller and a high-speed electro-optic modulator, a microwave signal source drives the high-speed electro-optic intensity modulator to modulate in a mode of carrier suppression and double side bands, so that the frequency shift of the path of optical signal is close to Brillouin frequency shift, and then the first path of optical signal is divided into two paths through a second 1 x 2 optical fiber coupler: the first branch optical signal is used as a detection optical signal, and the second branch optical signal is used as a pumping compensation optical signal; the detection light sequentially passes through the optical polarization scrambler and the optical switch and then enters one path of incident end of the third 1X 2 optical fiber coupler; the pump compensation optical signal is sequentially filtered out a high-frequency sideband optical signal through a band-pass filter, a first erbium-doped optical fiber amplifier, a first optical circulator and a first optical fiber grating, amplified, filtered and filtered to remove spontaneous radiation noise introduced by the first erbium-doped optical fiber amplifier and then enters the other incident end of the third 1 x 2 optical fiber coupler; the detection optical signal and the pump compensation optical signal pass through the third 1 x 2 optical fiber coupler and are incident to one end of the sensing optical fiber. The pumping light signal passes through the semiconductor optical amplifier to modulate a differential pulse pair, then passes through the second erbium-doped optical fiber amplifier, the second optical circulator, the second optical fiber grating and the third optical circulator in sequence to be amplified, and then enters the other end of the sensing optical fiber after being filtered and looped to remove spontaneous radiation noise introduced by the second erbium-doped optical fiber amplifier.
B. When the optical switch is switched off, the differential pulse pair is used as pump light to generate Raman scattering in the sensing optical fiber, backward Raman scattering light carrying temperature information enters the wavelength division multiplexer through the third circulator, the wavelength division multiplexer can filter out Stokes light and anti-Stokes light, and then the backward Raman scattering light respectively enters the data acquisition and processing system after entering the first avalanche photodiode, the first signal amplifier, the second avalanche photodiode and the second signal amplifier; the high-frequency pump compensation optical signal and the reverse pump light generate stimulated Brillouin amplification in the sensing optical fiber, and the energy of the pump compensation optical signal is transferred to the pump light in the process, so that the synchronous online amplification of the pump light is realized.
When the optical switch is closed, the differential pulse pair is used as pumping light and detecting light to generate stimulated Brillouin scattering in the sensing optical fiber, backward Brillouin scattering light carrying temperature and strain information enters the wavelength division multiplexer through the third circulator, the wavelength division multiplexer filters out Stokes light, and the Stokes light enters the data acquisition and processing system after entering the photoelectric detector; the high-frequency pump compensation optical signal and the reverse pump light generate stimulated Brillouin amplification in the sensing optical fiber, and the energy of the pump compensation optical signal is transferred to the pump light in the process, so that the synchronous online amplification of the pump light is realized.
Compared with the existing distributed optical fiber sensing system, the long-distance multi-parameter measuring device and method based on Brillouin and Raman scattering have the following advantages:
the invention relates to a long-distance multi-parameter measuring device and method based on Brillouin and Raman scattering, which are characterized in that an optical switch device is added in a detection path to realize simultaneous measurement of temperature and strain along a sensing optical fiber. Specifically, when the optical switch is in a closed state, the temperature measurement is realized by utilizing the characteristic that a backward Rayleigh scattering signal of pump pulse light in the sensing optical fiber is only sensitive to the temperature; when the switch is in an open state, the temperature and the strain are simultaneously measured by utilizing the stimulated Brillouin scattering effect of the probe light and the pump light in the sensing optical fiber. The problem of cross sensitivity of multi-parameter measurement in the traditional BOTDA system is avoided.
Compared with the traditional distributed Brillouin pumping amplification system, the long-distance multi-parameter measurement device and method based on Brillouin and Raman scattering are characterized in that the distributed Brillouin pumping device is added in a detection path to synchronously compensate and amplify the pumping light, so that the transmission loss of pumping light signals in sensing optical fibers is avoided, and the signal-to-noise ratio and the sensing distance of the system are effectively improved; compared with the conventional sensing device, the sensing device realizes stimulated Brillouin amplification of the pump light by using the second laser and triangular wave modulation, and is characterized in that the high-frequency sideband filtered in a detection path of the traditional BOTDA system is effectively utilized and is subjected to stimulated Brillouin amplification in the sensing optical fiber together with the reverse pump light, so that the pump light is synchronously amplified on line. Thus avoiding additional complex modulation and reducing the cost of the system. Meanwhile, the signal-to-noise ratio of the system is effectively improved, and the sensing distance and the measurement precision of the system are further improved.
The pump light in the long-distance multi-parameter measuring device and method based on Brillouin and Raman scattering is a differential pulse pair, and the spatial resolution of the system can be improved by adopting the differential pulse pair.
The distributed optical fiber sensing system is reasonable in design, effectively solves the problem that cross sensitivity and long-distance and high-precision measurement among multiple measured parameters of the existing distributed optical fiber sensing system cannot be considered at the same time, and is suitable for the field of distributed optical fiber sensing.
Drawings
Fig. 1 shows a schematic structural diagram of a sensing device based on brillouin and raman scattering long-distance multi-parameter measurement according to the present invention.
In the figure: 1-semiconductor laser, 2-first 1 x 2 optical fiber coupler, 3-optical fiber polarization controller, 4-high speed electro-optical modulator, 5-microwave signal source, 6-second 1 x 2 optical fiber coupler, 7-optical polarizer, 8-optical switch, 9-third 1 x 2 optical fiber coupler, 10-band-pass filter, 11-first erbium-doped optical fiber amplifier, 12-first optical circulator, 13-first optical fiber grating, 14-sensing optical fiber, 15-semiconductor optical amplifier, 16-second erbium-doped optical fiber amplifier, 17-second optical circulator, 18-second optical fiber grating, 19-third optical circulator, 20-avalanche multiplexer, 21-first avalanche photodiode, 22-photodetector, 23-second photodiode, 24-a first signal amplifier, 25-a second signal amplifier, 26-a data acquisition and processing system.
Detailed Description
The following detailed description of specific embodiments of the invention refers to the accompanying drawings.
A long-distance multi-parameter measuring device based on brillouin and raman scattering, as shown in figure 1, the optical fiber polarization controller comprises a semiconductor laser 1, a first 1 x 2 optical fiber coupler 2, an optical fiber polarization controller 3, a high-speed electro-optical modulator 4, a microwave signal source 5, a second 1 x 2 optical fiber coupler 6, an optical polarization scrambler 7, an optical switch 8, a third 1 x 2 optical fiber coupler 9, a band-pass filter 10, a first erbium-doped optical fiber amplifier 11, a first optical circulator 12, a first optical fiber grating 13, a sensing optical fiber 14, a semiconductor optical amplifier 15, a second erbium-doped optical fiber amplifier 16, a second optical circulator 17, a second optical fiber grating 18, a third optical circulator 19, a wavelength division multiplexer 20, a first avalanche photodiode 21, a photoelectric detector 22, a second avalanche photodiode 23, a first signal amplifier 24, a second signal amplifier 25 and a data acquisition and processing system 26.
Wherein, the exit end of the semiconductor laser 1 is connected with the incident end of the first 1 × 2 optical fiber coupler 2.
The first emergent end of the first 1 x 2 optical fiber coupler 2 is connected with the incident end of the optical fiber polarization controller 3, the emergent end of the optical fiber polarization controller 3 is connected with the incident end of the high-speed electro-optical modulator 4, the output end of the microwave signal source 5 is connected with the input end of the high-speed electro-optical modulator 4, and the emergent end of the high-speed electro-optical modulator 4 is connected with the incident end of the second 1 x 2 optical fiber coupler 6.
The first exit end of the second 1 × 2 optical fiber coupler 6 is connected to the incident end of the optical polarization scrambler 7, the exit end of the optical polarization scrambler 7 is connected to the incident end of the optical switch 8, and the exit end of the optical switch 8 is connected to one incident end of the third 1 × 2 optical fiber coupler 9.
The second exit end of the second 1 × 2 fiber coupler 6 is connected to the incident end of the band-pass filter 10, the exit end of the band-pass filter 10 is connected to the incident end of the first erbium-doped fiber amplifier 11, the exit end of the first erbium-doped fiber amplifier 11 is connected to the incident end of the first optical circulator 12, the reflection end of the first optical circulator 12 is connected to the first fiber grating 13, the exit end of the first optical circulator 12 is connected to the other incident end of the third 1 × 2 fiber coupler 9, and the exit end of the third 1 × 2 fiber coupler 9 is connected to one end of the sensing fiber 14.
The second exit end of the first 1 × 2 optical fiber coupler 2 is connected to the incident end of the semiconductor optical amplifier 15, the exit end of the semiconductor optical amplifier 15 is connected to the incident end of the second erbium-doped optical fiber amplifier 16, the exit end of the second erbium-doped optical fiber amplifier 16 is connected to the incident end of the second optical circulator 17, the reflection end of the second optical circulator 17 is connected to the second optical fiber grating 18, the exit end of the second optical circulator 17 is connected to the incident end of the third optical circulator 19, and the reflection end of the third optical circulator 19 is connected to the other end of the sensing optical fiber 14.
The exit end of the third optical circulator 19 is connected to the entrance end of the wavelength division multiplexer 20, the first exit end of the wavelength division multiplexer 20 is connected to the entrance end of the first avalanche photodiode 21, the output end of the first avalanche photodiode 21 is connected to the first signal amplifier 24, the output end of the first signal amplifier 24 is connected to the data acquisition and processing system 26, the second exit end of the wavelength division multiplexer 20 is connected to the entrance end of the photodetector 22, the output end of the photodetector 22 is connected to the data acquisition and processing system 26, the third exit end of the wavelength division multiplexer 20 is connected to the entrance end of the second avalanche photodiode 23, the output end of the second avalanche photodiode 23 is connected to the second signal amplifier 25, and the output end of the second signal amplifier 25 is connected to the data acquisition and processing system 26.
A long-distance multi-parameter measuring method based on Brillouin and Raman scattering (the method is realized in the long-distance multi-parameter measuring device based on Brillouin and Raman scattering), which is realized by adopting the following steps:
(1) the laser emitted by the semiconductor laser 1 is divided into two paths through the first 1 x 2 optical fiber coupler 2: the first path of laser is used as a detection optical signal and a pumping compensation optical signal, and the second path of laser is used as a pumping optical signal; the first path of laser signal firstly passes through the optical fiber polarization controller 3 and the high-speed electro-optic modulator 4, the microwave signal source 5 drives the high-speed electro-optic intensity modulator 4 to modulate in a mode of carrier suppression and double side bands, so that the frequency shift of the path of optical signal is near the Brillouin frequency shift (generally, the frequency shift range is 200MHz, so that the frequency shift of the path of optical signal is as close to the Brillouin frequency shift as possible), and then the first path of optical signal is divided into two paths through the second 1 x 2 optical fiber coupler 6: the first branch optical signal is used as a detection optical signal, and the second branch optical signal is used as a pumping compensation optical signal; the detection light sequentially passes through the optical polarization scrambler 7 and the optical switch 8 and then enters one path of incident end of the third 1 x 2 optical fiber coupler 9; the pump compensation optical signal is sequentially filtered out a high-frequency sideband optical signal through a band-pass filter 10, a first erbium-doped optical fiber amplifier 11, a first optical circulator 12 and a first optical fiber grating 13, amplified, filtered and filtered to remove spontaneous radiation noise introduced by the first erbium-doped optical fiber amplifier 11 and then enters the other incident end of a third 1 x 2 optical fiber coupler 9; the detection optical signal and the pump compensation optical signal pass through a third 1 x 2 optical fiber coupler 9 and enter one end of a sensing optical fiber 14; the pumping light signal passes through the semiconductor optical amplifier 15 to modulate a differential pulse pair (only pulse intervals are required to be ensured to enable pulses to enter the sensing optical fiber in sequence by changing the pulse width of the differential pulse pair), and then passes through the second erbium-doped optical fiber amplifier 16, the second optical circulator 17, the second optical fiber grating 18 and the third optical circulator 19 in sequence to be amplified, so that spontaneous radiation noise introduced by the second erbium-doped optical fiber amplifier 16 is filtered, and the pumping light signal circulates and enters the other end of the sensing optical fiber 14.
(2) When the optical switch 8 is switched off, the differential pulse pair is used as pump light to generate Raman scattering in the sensing optical fiber 14, backward Raman scattering light carrying temperature information enters the wavelength division multiplexer 20 through the third circulator 19, the wavelength division multiplexer 20 filters out Stokes light and anti-Stokes light, and the Stokes light and the anti-Stokes light respectively enter the data acquisition and processing system 26 after entering the first avalanche photodiode 21, the first signal amplifier 24, the second avalanche photodiode 23 and the second signal amplifier 25; the high-frequency pump compensation optical signal and the reverse pump light are subjected to stimulated brillouin amplification in the sensing optical fiber 14, and the energy of the pump compensation optical signal is transferred to the pump light in the process, so that synchronous online amplification of the pump light is realized.
When the optical switch 8 is closed, the differential pulse pair is used as pump light and probe light to generate stimulated brillouin scattering in the sensing optical fiber 14, backward brillouin scattering light carrying temperature and strain information enters the wavelength division multiplexer 20 through the third circulator 19, the wavelength division multiplexer 20 filters out stokes light, and the stokes light enters the data acquisition and processing system 26 after entering the photoelectric detector 22; the high-frequency pump compensation optical signal and the reverse pump light are subjected to stimulated brillouin amplification in the sensing optical fiber 14, and the energy of the pump compensation optical signal is transferred to the pump light in the process, so that synchronous online amplification of the pump light is realized.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the detailed description is made with reference to the embodiments of the present invention, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the protection scope of the claims of the present invention.
Claims (2)
1. A long-distance multi-parameter measuring device based on Brillouin and Raman scattering is characterized in that: the device comprises a semiconductor laser (1), a first 1 x 2 optical fiber coupler (2), an optical fiber polarization controller (3), a high-speed electro-optical modulator (4), a microwave signal source (5), a second 1 x 2 optical fiber coupler (6), an optical polarization scrambler (7), an optical switch (8), a third 1 x 2 optical fiber coupler (9), a band-pass filter (10), a first erbium-doped optical fiber amplifier (11), a first optical circulator (12), a first optical fiber grating (13), a sensing optical fiber (14), a semiconductor optical amplifier (15), a second erbium-doped optical fiber amplifier (16), a second optical circulator (17), a second optical fiber grating (18), a third optical circulator (19), a wavelength division multiplexer (20), a first avalanche photodiode (21), a photoelectric detector (22), a second avalanche photodiode (23), a first signal amplifier (24), A second signal amplifier (25), a data acquisition and processing system (26);
the emergent end of the semiconductor laser (1) is connected with the incident end of the first 1 multiplied by 2 optical fiber coupler (2);
the first emergent end of the first 1 x 2 optical fiber coupler (2) is connected with the incident end of the optical fiber polarization controller (3), the emergent end of the optical fiber polarization controller (3) is connected with the incident end of the high-speed electro-optical modulator (4), the output end of the microwave signal source (5) is connected with the input end of the high-speed electro-optical modulator (4), and the emergent end of the high-speed electro-optical modulator (4) is connected with the incident end of the second 1 x 2 optical fiber coupler (6);
the first emergent end of the second 1 x 2 optical fiber coupler (6) is connected with the incident end of the optical polarization scrambler (7), the emergent end of the optical polarization scrambler (7) is connected with the incident end of the optical switch (8), and the emergent end of the optical switch (8) is connected with one incident end of the third 1 x 2 optical fiber coupler (9);
the second emergent end of the second 1 x 2 optical fiber coupler (6) is connected with the incident end of the band-pass filter (10), the emergent end of the band-pass filter (10) is connected with the incident end of the first erbium-doped optical fiber amplifier (11), the emergent end of the first erbium-doped optical fiber amplifier (11) is connected with the incident end of the first optical circulator (12), the reflecting end of the first optical circulator (12) is connected with the first optical fiber grating (13), the emergent end of the first optical circulator (12) is connected with the other incident end of the third 1 x 2 optical fiber coupler (9), and the emergent end of the third 1 x 2 optical fiber coupler (9) is connected with one end of the sensing optical fiber (14);
the second emergent end of the first 1 x 2 optical fiber coupler (2) is connected with the incident end of a semiconductor optical amplifier (15), the emergent end of the semiconductor optical amplifier (15) is connected with the incident end of a second erbium-doped optical fiber amplifier (16), the emergent end of the second erbium-doped optical fiber amplifier (16) is connected with the incident end of a second optical circulator (17), the reflecting end of the second optical circulator (17) is connected with a second optical fiber grating (18), the emergent end of the second optical circulator (17) is connected with the incident end of a third optical circulator (19), and the reflecting end of the third optical circulator (19) is connected with the other end of the sensing optical fiber (14);
the exit end of the third optical circulator (19) is connected with the entrance end of the wavelength division multiplexer (20), the first exit end of the wavelength division multiplexer (20) is connected with the entrance end of the first avalanche photodiode (21), the output end of the first avalanche photodiode (21) is connected with the first signal amplifier (24), the output end of the first signal amplifier (24) is connected with the data acquisition and processing system (26), the second exit end of the wavelength division multiplexer (20) is connected with the entrance end of the photodetector (22), the output end of the photodetector (22) is connected with the data acquisition and processing system (26), the third exit end of the wavelength division multiplexer (20) is connected with the entrance end of the second avalanche photodiode (23), the output end of the second avalanche photodiode (23) is connected with the second signal amplifier (25), and the output end of the second signal amplifier (25) is connected with the data acquisition and processing system (26).
2. A long-distance multi-parameter measurement method based on Brillouin and Raman scattering is characterized by comprising the following steps: the method is realized in a long-distance multi-parameter measuring device which comprises a semiconductor laser (1), a first 1 x 2 optical fiber coupler (2), an optical fiber polarization controller (3), a high-speed electro-optical modulator (4), a microwave signal source (5), a second 1 x 2 optical fiber coupler (6), an optical polarization scrambler (7), an optical switch (8), a third 1 x 2 optical fiber coupler (9), a band-pass filter (10), a first erbium-doped optical fiber amplifier (11), a first optical circulator (12), a first optical fiber grating (13), a sensing optical fiber (14), a semiconductor optical amplifier (15), a second optical fiber amplifier (16), a second optical circulator (17), a second optical fiber grating (18), a third optical circulator (19), a wavelength division multiplexer (20), a first photodiode (21), The photoelectric detector (22), the second avalanche photodiode (23), the first signal amplifier (24), the second signal amplifier (25) and the data acquisition and processing system (26);
the emergent end of the semiconductor laser (1) is connected with the incident end of the first 1 multiplied by 2 optical fiber coupler (2);
the first emergent end of the first 1 x 2 optical fiber coupler (2) is connected with the incident end of the optical fiber polarization controller (3), the emergent end of the optical fiber polarization controller (3) is connected with the incident end of the high-speed electro-optical modulator (4), the output end of the microwave signal source (5) is connected with the input end of the high-speed electro-optical modulator (4), and the emergent end of the high-speed electro-optical modulator (4) is connected with the incident end of the second 1 x 2 optical fiber coupler (6);
the first emergent end of the second 1 x 2 optical fiber coupler (6) is connected with the incident end of the optical polarization scrambler (7), the emergent end of the optical polarization scrambler (7) is connected with the incident end of the optical switch (8), and the emergent end of the optical switch (8) is connected with one incident end of the third 1 x 2 optical fiber coupler (9);
the second emergent end of the second 1 x 2 optical fiber coupler (6) is connected with the incident end of the band-pass filter (10), the emergent end of the band-pass filter (10) is connected with the incident end of the first erbium-doped optical fiber amplifier (11), the emergent end of the first erbium-doped optical fiber amplifier (11) is connected with the incident end of the first optical circulator (12), the reflecting end of the first optical circulator (12) is connected with the first optical fiber grating (13), the emergent end of the first optical circulator (12) is connected with the other incident end of the third 1 x 2 optical fiber coupler (9), and the emergent end of the third 1 x 2 optical fiber coupler (9) is connected with one end of the sensing optical fiber (14);
the second emergent end of the first 1 x 2 optical fiber coupler (2) is connected with the incident end of a semiconductor optical amplifier (15), the emergent end of the semiconductor optical amplifier (15) is connected with the incident end of a second erbium-doped optical fiber amplifier (16), the emergent end of the second erbium-doped optical fiber amplifier (16) is connected with the incident end of a second optical circulator (17), the reflecting end of the second optical circulator (17) is connected with a second optical fiber grating (18), the emergent end of the second optical circulator (17) is connected with the incident end of a third optical circulator (19), and the reflecting end of the third optical circulator (19) is connected with the other end of the sensing optical fiber (14);
the exit end of the third optical circulator (19) is connected with the entrance end of the wavelength division multiplexer (20), the first exit end of the wavelength division multiplexer (20) is connected with the entrance end of the first avalanche photodiode (21), the output end of the first avalanche photodiode (21) is connected with the first signal amplifier (24), the output end of the first signal amplifier (24) is connected with the data acquisition and processing system (26), the second exit end of the wavelength division multiplexer (20) is connected with the entrance end of the photodetector (22), the output end of the photodetector (22) is connected with the data acquisition and processing system (26), the third exit end of the wavelength division multiplexer (20) is connected with the entrance end of the second avalanche photodiode (23), the output end of the second avalanche photodiode (23) is connected with the second signal amplifier (25), and the output end of the second signal amplifier (25) is connected with the data acquisition and processing system (26);
the specific long-distance multi-parameter measuring method comprises the following steps:
(1) laser emitted by the semiconductor laser (1) is divided into two paths through the first 1 multiplied by 2 optical fiber coupler (2): the first path of laser is used as a detection optical signal and a pumping compensation optical signal, and the second path of laser is used as a pumping optical signal; the first path of laser signals firstly pass through an optical fiber polarization controller (3) and a high-speed electro-optic modulator (4), a microwave signal source (5) drives the high-speed electro-optic intensity modulator (4) to modulate in a mode of carrier suppression and double side bands, so that the frequency shift of the path of optical signals is near Brillouin frequency shift, and then the first path of optical signals are divided into two paths through a second 1 x 2 optical fiber coupler (6): the first branch optical signal is used as a detection optical signal, and the second branch optical signal is used as a pumping compensation optical signal; the detection light sequentially passes through the optical polarization scrambler (7) and the optical switch (8) and then enters one path of incident end of the third 1 x 2 optical fiber coupler (9); the pump compensation optical signal sequentially passes through a band-pass filter (10), a first erbium-doped optical fiber amplifier (11), a first optical circulator (12) and a first optical fiber grating (13) to filter out a high-frequency sideband optical signal, amplify and filter spontaneous radiation noise introduced by the first erbium-doped optical fiber amplifier (11), and then enters the other incident end of a third 1 x 2 optical fiber coupler (9); the detection optical signal and the pump compensation optical signal pass through a third 1 x 2 optical fiber coupler (9) and are incident to one end of a sensing optical fiber (14); the pumping light signal firstly passes through a semiconductor optical amplifier (15) to modulate a differential pulse pair, then sequentially passes through a second erbium-doped optical fiber amplifier (16), a second optical circulator (17), a second optical fiber grating (18) and a third optical circulator (19) to be amplified, spontaneous radiation noise introduced by the second erbium-doped optical fiber amplifier (16) is filtered, and the pumped light signal enters the other end of the sensing optical fiber (14) after being looped;
(2) when the optical switch (8) is switched off, the differential pulse pair is used as pump light to generate Raman scattering in the sensing optical fiber (14), backward Raman scattering light carrying temperature information enters the wavelength division multiplexer (20) through the third circulator (19), the wavelength division multiplexer (20) filters out Stokes light and anti-Stokes light, and the Stokes light and the anti-Stokes light respectively enter the data acquisition and processing system (26) after entering the first avalanche photodiode (21), the first signal amplifier (24), the second avalanche photodiode (23) and the second signal amplifier (25); the high-frequency pump compensation optical signal and the reverse pump light generate stimulated Brillouin amplification in the sensing optical fiber (14), and the energy of the pump compensation optical signal is transferred to the pump light in the process, so that the synchronous online amplification of the pump light is realized;
when the optical switch (8) is closed, the differential pulse pair is used as pump light and probe light to generate stimulated Brillouin scattering in the sensing optical fiber (14), backward Brillouin scattering light carrying temperature and strain information enters the wavelength division multiplexer (20) through the third circulator (19), the Stokes light is filtered out by the wavelength division multiplexer (20), and enters the data acquisition and processing system (26) after entering the photoelectric detector (22); the high-frequency pumping compensation optical signal and the reverse pumping light generate stimulated Brillouin amplification in the sensing optical fiber (14), and the energy of the pumping compensation optical signal is transferred to the pumping light in the process, so that the synchronous online amplification of the pumping light is realized.
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| CN114812635B (en) * | 2022-04-19 | 2023-10-20 | 中国兵器工业第五九研究所 | Modularized multi-parameter water quality monitoring fiber bragg grating sensor |
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