CN113390445B - Sensitivity-enhanced distributed Brillouin optical fiber bending sensor - Google Patents
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- 230000010287 polarization Effects 0.000 claims abstract description 25
- 238000001514 detection method Methods 0.000 claims abstract description 23
- 238000001228 spectrum Methods 0.000 claims abstract description 13
- 230000002269 spontaneous effect Effects 0.000 claims abstract description 9
- 230000005855 radiation Effects 0.000 claims abstract description 7
- 239000000835 fiber Substances 0.000 claims description 58
- 230000003287 optical effect Effects 0.000 claims description 12
- 239000000523 sample Substances 0.000 description 8
- 238000005259 measurement Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 229910052691 Erbium Inorganic materials 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
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- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 1
- -1 erbium ions Chemical class 0.000 description 1
- 238000002189 fluorescence spectrum Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 239000003208 petroleum Substances 0.000 description 1
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- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35329—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using interferometer with two arms in transmission, e.g. Mach-Zender interferometer
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Abstract
The invention discloses a sensitivity-enhanced distributed Brillouin optical fiber bending sensor which comprises a coupler, a first polarization controller, a second polarization controller, a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, a waveform generator, a polarization scrambler, a first wavelength division multiplexer, a first pumping light source, an erbium-doped optical fiber amplifier, a few-mode erbium-doped optical fiber, a second wavelength division multiplexer, a first optical fiber circulator, an isolator, a second pumping light source, a second optical fiber circulator, an optical fiber Bragg grating filter, a photoelectric detector and an oscilloscope. The erbium-doped ring-core few-mode optical fiber is pumped by using a high-power light source to generate a spontaneous radiation spectrum, and signal light transmitted in the optical fiber is amplified to make up for loss generated by bending of the optical fiber, so that a larger bending radius detection range is realized, and the bending radius detection sensitivity is enhanced.
Description
Technical Field
The invention belongs to the technical field of optics, and particularly relates to a distributed Brillouin optical fiber bending sensor with enhanced sensitivity.
Background
In the past decades, optical fiber sensors have been widely studied due to their advantages of compact structure, low cost, long sensing range, corrosion resistance, electromagnetic interference resistance, etc. The distributed optical fiber sensor can realize continuous multipoint measurement on one optical fiber and has the advantages of long measurement distance, simple wiring and the like. The Brillouin optical time domain analysis technology is one of distributed optical fiber sensing technologies, can measure the change of absolute physical quantity, has the advantages of long measurement distance, high spatial resolution, high measurement precision, high signal-to-noise ratio and the like, and has important application value in the fields of bridge tunnels, petroleum pipelines, subway rails, electric power wires, aerospace and the like.
How to realize bending sensing based on the distributed optical fiber sensing technology is a problem that researchers always want to solve. Currently, a Brillouin optical time domain analysis technology is utilized to carry out bending measurement; firstly, the sensing optical fibers are symmetrically adhered to two sides of the steel tape, and because the inner side optical fibers and the outer side optical fibers are stressed differently when the optical fibers are bent, bending sensing is realized by measuring the difference value of Brillouin frequency shift of the inner side optical fibers and the outer side optical fibers. This method can eliminate temperature cross-sensitivity, but single mode fibers have large bending losses, resulting in small measurable radii and poor flexibility.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a distributed brillouin optical fiber bending sensor. The erbium-doped ring-core few-mode optical fiber is pumped by using a high-power light source to generate a spontaneous radiation spectrum, and signal light transmitted in the optical fiber is amplified to make up for loss generated by bending of the optical fiber, so that a larger bending radius detection range is realized, and the bending radius detection sensitivity is enhanced.
The purpose of the invention can be achieved by adopting the following technical scheme:
a sensitivity-enhanced distributed Brillouin optical fiber bending sensor comprises a coupler, a first polarization controller, a second polarization controller, a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, a waveform generator, a polarization scrambler, a first wavelength division multiplexer, a first pumping light source, an erbium-doped optical fiber amplifier, a few-mode erbium-doped optical fiber, a second wavelength division multiplexer, a first optical fiber circulator, an isolator, a second pumping light source, a second optical fiber circulator, an optical fiber Bragg grating filter, a photoelectric detector and an oscilloscope; the first output end of the coupler is connected with the first input end of a first Mach-Zehnder modulator through a first polarization controller, the second input end of the first Mach-Zehnder modulator is connected with a waveform generator and a direct current source, the output end of the first Mach-Zehnder modulator is connected with the input end of an erbium-doped optical fiber amplifier through a scrambler, and the output end of the erbium-doped optical fiber amplifier is connected with the first input end of a first optical fiber circulator; the fiber laser emits laser, and the laser is divided into pump pulse light and continuous detection light through an optical coupler; after passing through the first Mach-Zehnder modulator, the pumping pulse light is driven by a direct current source and a waveform generator to generate two pulses with different pulse widths; then the pump light passes through a polarization scrambler to randomize the polarization state, is amplified by an erbium-doped fiber amplifier to obtain gain, and then enters a first fiber circulator through a circulator;
a second output end of the coupler is connected with a first input end of a second Mach-Zehnder modulator through a second polarization controller, and a second input end of the second Mach-Zehnder modulator is connected with the radio frequency source and the direct current source; the first output end of the second Mach-Zehnder modulator is connected with the input end of the first wavelength division multiplexer through an isolator, and the second output end of the second Mach-Zehnder modulator is connected with the input end of the first pumping light source through the isolator; the output end of the first wavelength division multiplexer is connected with the input end of a second wavelength division multiplexer through a few-mode erbium-doped optical fiber, the first output end of the second wavelength division multiplexer is connected with a second pumping light source, and the second output end of the second wavelength division multiplexer is connected with the second input end of the first optical fiber circulator; the output end of the first optical fiber circulator is connected with the first input end of the second optical fiber circulator, the second input end of the second optical fiber circulator is connected with the output end of the fiber Bragg grating filter, and the output end of the second optical fiber circulator is connected with an oscilloscope through a photoelectric detector; the continuous detection light is modulated into carrier-suppressed double-sideband wave detection light through a second Mach-Zehnder modulator, then enters the few-mode erbium-doped optical fiber through a first wavelength division multiplexer, and meanwhile, a first pumping light source is input into the few-mode erbium-doped optical fiber through the first wavelength division multiplexer; and pumping the few-mode erbium-doped fiber at a second pumping light source through a second wavelength division multiplexer to enable the few-mode erbium-doped fiber to generate a spontaneous radiation spectrum, so that transmitted pumping pulse light and continuous detection light are amplified to make up for optical loss generated by bending.
Preferably, the first pump light source and the second pump light source are single-mode pump light sources.
Preferably, the first pump light source and the second pump light source are 980mm single-mode pump light sources.
The implementation of the invention has the following beneficial effects:
1. the invention pumps the few-mode erbium-doped fiber through the second wavelength division multiplexer at the second pumping light source, so that the few-mode erbium-doped fiber generates a spontaneous radiation spectrum, and the transmitted pumping pulse light and the continuous detection light are amplified to make up for the light loss generated by bending. The amplified detection light enters the photoelectric detector and is collected by the oscilloscope after being filtered by the second optical fiber circulator and the optical fiber Bragg grating filter. The Brillouin gain spectrum of the few-mode erbium-doped fiber can be obtained by gradually changing the frequency of the probe light, and the Brillouin frequency shift of the fiber to be tested can be determined by fitting the gain spectrum. By calibrating Brillouin frequency shift of the few-mode erbium-doped fiber under different bending radii, bending sensing can be realized.
2. The erbium-doped ring-core few-mode optical fiber is pumped by using a high-power light source to generate a spontaneous radiation spectrum, and signal light transmitted in the optical fiber is amplified to make up for loss generated by bending of the optical fiber, so that a larger bending radius detection range is realized, and the bending radius detection sensitivity is enhanced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of the structure of a distributed Brillouin optical fiber bend sensor of the present invention with enhanced sensitivity;
fig. 2 is a schematic structural diagram of a few-mode erbium-doped fiber of a distributed brillouin fiber bend sensor of the present invention with enhanced sensitivity.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.
Examples
Referring to fig. 1 and 2, the present embodiment relates to a distributed brillouin optical fiber bending sensor with enhanced sensitivity, which includes a coupler 1, a first polarization controller 2, a second polarization controller 3, a first mach-zehnder modulator 4, a second mach-zehnder modulator 5, a waveform generator 6, a scrambler 7, a first wavelength division multiplexer 8, a first pump light source 9, an erbium-doped optical fiber amplifier 10, a few-mode erbium-doped optical fiber 11, a second wavelength division multiplexer 12, a first optical fiber circulator 13, an isolator 14, a second pump light source 15, a second optical fiber circulator 16, an optical fiber bragg grating filter 17, a photoelectric detector 18, and an oscilloscope 19; a first output end of the coupler 1 is connected with a first input end of a first Mach-Zehnder modulator 4 through a first polarization controller 2, a second input end of the first Mach-Zehnder modulator 4 is connected with a waveform generator 6 and a direct current source 20, an output end of the first Mach-Zehnder modulator 4 is connected with an input end of an erbium-doped optical fiber amplifier 10 through a scrambler 7, and an output end of the erbium-doped optical fiber amplifier 10 is connected with a first input end of a first optical fiber circulator 13; the optical fiber laser 101 emits laser, and the laser is divided into pump pulse light and continuous detection light through the optical coupler 1; after passing through the first Mach-Zehnder modulator 4, the pumping pulse light is driven by the direct current source 20 and the waveform generator 6 to generate two pulses with different pulse widths; then the pump light passes through a polarization scrambler 7 to randomize the polarization state, and then is amplified by an erbium-doped fiber amplifier 10 to obtain gain and then enters a first fiber circulator 13;
a second output end of the coupler 1 is connected with a first input end of a second Mach-Zehnder modulator 5 through a second polarization controller 3, and a second input end of the second Mach-Zehnder modulator 5 is connected with an RF source 21 and a second DC source 22; a first output end of the second mach-zehnder modulator 5 is connected with an input end of the first wavelength division multiplexer 8 through an isolator 14, and a second output end of the second mach-zehnder modulator 5 is connected with an input end of the first pumping light source 9 through the isolator 14; the output end of the first wavelength division multiplexer 8 is connected with the input end of a second wavelength division multiplexer 12 through a few-mode erbium-doped fiber 11, the first output end of the second wavelength division multiplexer 12 is connected with a second pump light source 15, and the second output end of the second wavelength division multiplexer 12 is connected with the second input end of a first fiber circulator 13; the output end of the first optical fiber circulator 13 is connected with the first input end of the second optical fiber circulator 16, the second input end of the second optical fiber circulator 16 is connected with the output end of the optical fiber Bragg grating filter 17, and the output end of the second optical fiber circulator 16 is connected with an oscilloscope 19 through a photoelectric detector 18; the continuous detection light is modulated into carrier-suppressed double-sideband wave detection light through the second Mach-Zehnder modulator 5, then enters the few-mode erbium-doped fiber 11 through the first wavelength division multiplexer 8, and meanwhile, the first pumping light source 9 is input into the few-mode erbium-doped fiber 11 through the first wavelength division multiplexer 8; the second pumping light source 15 pumps the few-mode erbium-doped fiber 11 through the second wavelength division multiplexer 12, so that the few-mode erbium-doped fiber 11 generates a spontaneous emission spectrum, and the transmitted pumping pulse light and the continuous probe light are amplified to compensate for optical loss generated by bending. The amplified probe light is filtered by the second fiber circulator 16 and the fiber bragg grating filter 17, enters the photoelectric detector 18 and is collected by the oscilloscope 19. By gradually changing the frequency of the probe light, the brillouin gain spectrum of the few-mode erbium-doped fiber 11 can be obtained, and the brillouin frequency shift of the fiber to be measured can be determined by fitting the gain spectrum. By calibrating the brillouin frequency shift of the few-mode erbium-doped fiber 11 at different bending radii, bend sensing can be achieved.
The first pump light source 9 and the second pump light source 15 generate a fluorescence spectrum for erbium ions in the erbium-doped fiber with less modes 11, and amplify the sensing light signal in the erbium-doped fiber with less modes 11 to compensate for light loss generated in the bending process. Compared with the existing distributed Brillouin optical fiber bending sensor in the transverse direction, the few-mode erbium-doped optical fiber 11 used in the invention has more advantages in reducing optical loss caused by bending radius, and the invention uses a differential pulse pair Brillouin optical time domain analysis technology, improves the spatial resolution and the shape perception performance, and increases the effective measurement point number of the sensor.
As shown in fig. 2, the core of the erbium doped fiber with less modes 11 is distributed in a ring shape, and the position of the core in the cross section of the fiber is deviated from the geometric symmetry center of the cross section of the fiber. When the optical fiber is bent, the mode field in the optical fiber is deviated to the outer side of the central axis, so that the optical fiber is stressed by deviating from the central axis, and the Brillouin frequency shift of the optical fiber is sensitive to strain. Therefore, the few-mode erbium-doped fiber 11 is subjected to not only the brillouin frequency shift change due to mode field shift but also the brillouin frequency shift change due to stress caused by bending when bent. The two effects add up to greatly increase the sensitivity of the brillouin shift of the few-mode erbium-doped fiber 11 to bending, whereas the core of a single-mode fiber or a conventional few-mode fiber is located at the geometric center of the fiber and experiences little or no strain due to bending when bent. Therefore, the few-mode erbium-doped fiber 11 of the present invention has higher bending sensitivity.
According to the invention, the erbium-doped ring core 102 few-mode optical fiber is pumped by using a high-power light source to generate a spontaneous radiation spectrum, and signal light transmitted in the optical fiber is amplified to make up for loss generated by bending of the optical fiber, so that a larger bending radius detection range is realized, and the bending radius detection sensitivity is enhanced.
The first pump light source 9 and the second pump light source 15 are single-mode pump light sources. The first pump light source 9 and the second pump light source 15 are 980mm single-mode pump light sources.
The working principle of the invention is as follows:
the fiber laser emits laser, and the laser is divided into an upper branch and a lower branch through an optical coupler 1, wherein the upper branch is pumping pulse light, and the lower branch is continuous probe light; after passing through the first Mach-Zehnder modulator 4, the pumping pulse light is driven by a direct current source and a waveform generator 6 to generate two pulses with different pulse widths; then the pump light passes through a polarization scrambler 7 to randomize the polarization state, and then is amplified by an erbium-doped fiber amplifier 10 to obtain gain, and then enters a lower branch circuit through a first fiber circulator 13;
the continuous detection light is modulated into carrier-suppressed double-sideband wave detection light through the second Mach-Zehnder modulator 5, then enters the few-mode erbium-doped fiber 11 through the first wavelength division multiplexer 8, and meanwhile, the first pumping light source 9 is input into the few-mode erbium-doped fiber 11 through the first wavelength division multiplexer 8; the second pumping light source 15 pumps the few-mode erbium-doped fiber 11 through the second wavelength division multiplexer 12, so that the few-mode erbium-doped fiber 11 generates a spontaneous emission spectrum, and the transmitted pumping pulse light and the continuous probe light are amplified to compensate for optical loss generated by bending. The amplified probe light is filtered by the second fiber circulator 16 and the fiber grating filter, enters the photodetector 18 and is collected by the oscilloscope 19. By gradually changing the frequency of the probe light, the brillouin gain spectrum of the few-mode erbium-doped fiber 11 can be obtained, and the brillouin frequency shift of the fiber to be measured can be determined by fitting the gain spectrum. By calibrating the brillouin frequency shift of the few-mode erbium-doped fiber 11 at different bending radii, bend sensing can be achieved.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (3)
1. A sensitivity-enhanced distributed Brillouin optical fiber bending sensor is characterized by comprising a coupler, a first polarization controller, a second polarization controller, a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, a waveform generator, a polarization scrambler, a first wavelength division multiplexer, a first pumping light source, an erbium-doped optical fiber amplifier, a few-mode erbium-doped optical fiber, a second wavelength division multiplexer, a first optical fiber circulator, an isolator, a second pumping light source, a second optical fiber circulator, an optical fiber Bragg grating filter, a photoelectric detector and an oscilloscope; the first output end of the coupler is connected with the first input end of a first Mach-Zehnder modulator through a first polarization controller, the second input end of the first Mach-Zehnder modulator is connected with a waveform generator and a direct current source, the output end of the first Mach-Zehnder modulator is connected with the input end of an erbium-doped optical fiber amplifier through a scrambler, and the output end of the erbium-doped optical fiber amplifier is connected with the first input end of a first optical fiber circulator; the fiber laser emits laser, and the laser is divided into pump pulse light and continuous detection light through an optical coupler; after passing through the first Mach-Zehnder modulator, the pumping pulse light is driven by a direct current source and a waveform generator to generate two pulses with different pulse widths; then the pump light passes through a polarization scrambler to randomize the polarization state, is amplified by an erbium-doped fiber amplifier to obtain gain, and then enters a first fiber circulator through a circulator;
a second output end of the coupler is connected with a first input end of a second Mach-Zehnder modulator through a second polarization controller, and a second input end of the second Mach-Zehnder modulator is connected with the radio frequency source and the direct current source; the first output end of the second Mach-Zehnder modulator is connected with the input end of the first wavelength division multiplexer through an isolator, and the second output end of the second Mach-Zehnder modulator is connected with the input end of the first pumping light source through the isolator; the output end of the first wavelength division multiplexer is connected with the input end of a second wavelength division multiplexer through a few-mode erbium-doped optical fiber, the first output end of the second wavelength division multiplexer is connected with a second pumping light source, and the second output end of the second wavelength division multiplexer is connected with the second input end of the first optical fiber circulator; the output end of the first optical fiber circulator is connected with the first input end of the second optical fiber circulator, the second input end of the second optical fiber circulator is connected with the output end of the fiber Bragg grating filter, and the output end of the second optical fiber circulator is connected with an oscilloscope through a photoelectric detector; the continuous detection light is modulated into carrier-suppressed double-sideband wave detection light through a second Mach-Zehnder modulator, then enters the few-mode erbium-doped optical fiber through a first wavelength division multiplexer, and meanwhile, a first pumping light source is input into the few-mode erbium-doped optical fiber through the first wavelength division multiplexer; and pumping the few-mode erbium-doped fiber at a second pumping light source through a second wavelength division multiplexer to enable the few-mode erbium-doped fiber to generate a spontaneous radiation spectrum, so that transmitted pumping pulse light and continuous detection light are amplified to make up for optical loss caused by bending.
2. The enhanced sensitivity distributed brillouin fiber bend sensor of claim 1, wherein said first and second pump light sources are single mode pump light sources.
3. The enhanced sensitivity distributed brillouin fiber bend sensor of claim 2, wherein said first and second pump light sources are 980mm single mode pump light sources.
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