CN111721338B - Brillouin optical time domain analysis system for alternately modulating high frequency and low frequency of pump light - Google Patents
Brillouin optical time domain analysis system for alternately modulating high frequency and low frequency of pump light Download PDFInfo
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- 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
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- 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
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- 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
- G01D5/35383—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 multiple sensor devices using multiplexing techniques
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Abstract
The invention relates to a distributed optical fiber sensing system, and discloses a Brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light, which comprises a narrow linewidth laser, wherein light emitted by the narrow linewidth laser is divided into two beams after passing through a light splitter, and one beam is used as probe light to be subjected to double-sideband modulation of carrier suppression through a photoelectric modulator; then the light enters the sensing optical fiber after being amplified by the erbium-doped optical fiber amplifier, and the other beam of light is used as pump light and enters the sensing optical fiber from the other end after sequentially passing through the single-side band modulator, the pulse modulator and the pulse optical amplifier; the single-sideband modulator is used for alternately modulating the high frequency and the low frequency of the pump light to enable the pump light to alternate the high frequency sideband and the low frequency sideband and sweep the frequency of the high frequency sideband and the low frequency sideband; the Brillouin gain spectrum signal and the Brillouin loss signal emitted from the other end of the sensing optical fiber are received by the photoelectric detector after the stray light is filtered by the optical filter, and then are collected by the data acquisition card. The invention improves the signal power by 2 times of the traditional BOTDA system and improves the signal-to-noise ratio of the system.
Description
Technical Field
The invention relates to a distributed optical fiber sensing system, in particular to a BOTDA system for obtaining a gain/loss spectrum by alternately modulating pump light at high frequency and low frequency.
Background
The distributed optical fiber sensing technology combines signal transmission with a sensing medium, successfully realizes data measurement of temperature/strain and the like with the length of hundreds of kilometers, has the advantages of electromagnetic interference resistance, high sensitivity, long monitoring distance and the like, and can be widely applied to various fields of engineering and life, such as traffic tunnels, bridge buildings and mine environments, and can realize the functions of temperature monitoring, leakage monitoring, crack detection and the like.
In distributed optical fiber sensing, a BOTDA (Brillouin optical time-domain analysis) system has higher measurement accuracy, longer sensing distance and better system feasibility, so that the invention is based on the BOTDA system. There have been many studies on Balanced Detection techniques for gain and loss spectra (Alejandro Dom i ng uez-L lopez, Alexia L pez-Gil, Sonia Mart i n-L pez, and Miguel Gonz a lez-her a ez. Signal-to-Noise Ratio Improvement in the BOTDA Using Balanced Detection [ J ] IEEE PHOTOTON CHNOLOGY LETTERS 2014, 26(4): 338-341), but the system is complicated and costly. In turn, improvements to existing brillouin time domain analysis systems are needed.
Disclosure of Invention
The invention overcomes the defects of the prior art, and solves the technical problems that: the Brillouin optical time domain analysis system for high-low frequency alternative modulation of the pump light is characterized in that high-low frequency alternative modulation is carried out on the pump light through a single-sideband modulator, frequency sweeping is carried out, a Brillouin gain spectrum and a loss spectrum are obtained simultaneously, and then demodulation is processed through an algorithm, so that the purpose of improving the signal-to-noise ratio is achieved on the premise of greatly reducing the system device cost.
In order to solve the technical problems, the invention adopts the technical scheme that: a Brillouin optical time domain analysis system with alternately modulated pump light at high and low frequencies comprises a narrow linewidth laser, wherein light emitted by the narrow linewidth laser is divided into two beams after passing through a light splitter, one beam of light is used as detection light to be subjected to double-sideband modulation with carrier suppression through an electro-optical modulator, and the obtained frequencies are respectively
And
two sidebands; then the light enters the sensing optical fiber after being amplified by the erbium-doped optical fiber amplifier, and the other beam of light is used as pump light and enters the sensing optical fiber from the other end after sequentially passing through the single-side band modulator, the pulse modulator and the pulse optical amplifier;
the single sideband modulator is used for programmable microwave signalsThe pump light is alternately modulated at high and low frequencies under the drive of the source, so that the pump light alternately generates a frequency with a frequency of
With high frequency sidebands and frequencies of
Sweeping the frequency of the low-frequency sideband; the pulse modulator is used for modulating the pump light into a pulse signal, and the pulse light amplifier is used for amplifying the pulse light and then sending the amplified pulse light to the other end of the sensing optical fiber; wherein,
for the laser frequency emitted by a narrow linewidth laser,f 1in order to detect the frequency-shifted frequency of the light,f 2is the frequency shift frequency of the pump light;
the pumping light pulse light and the detection light alternately generate Brillouin gain and Brillouin loss in the sensing optical fiber, and a Brillouin gain spectrum signal and a Brillouin loss signal which are emitted from the other end of the sensing optical fiber are received by the photoelectric detector after stray light is filtered by the optical filter, and then are collected by the data collection card.
The Brillouin optical time domain analysis system for high-low frequency alternative modulation of the pump light further comprises a calculation unit connected with the data acquisition card, and the calculation unit is used for performing superposition calculation according to a Brillouin gain spectrum and a Brillouin loss spectrum acquired by the data acquisition card to obtain a synthesized Brillouin gain spectrum.
The Brillouin optical time domain analysis system with the alternately modulated high and low frequency of the pump light further comprises a pulse signal generator used for driving the pulse modulator.
The programmable microwave signal source is a two-channel microwave signal source, and a microwave signal output by the other channel of the two-channel microwave signal source is used for driving the electro-optical modulator.
The type of the programmable microwave signal source is as follows: a middle satellite Union SLFS-D series double-channel microwave simulation signal source; the single sideband modulator adopts a KG-ModBox-SSB series carrier suppression single sideband modulation module; the pulse modulator adopts an OPEAK OAM-SOA-PL type pulse modulator, and the pulse optical amplifier adopts an OPEAK EDFA-C-PL-NS-MB type pulse erbium-doped fiber amplifier; the sensing fiber adopts a G652 series single mode fiber.
Frequency shift frequency of probe lightf 1And frequency shift frequency of pump lightf 2The following conditions are satisfied: 10.5GHz< f 1+ f 2<11GHz and has
Wherein
The spectral width of the brillouin gain spectrum is shown.
When the pulse modulator modulates the pump light into a pulse signal, the preset interval of the pump pulse signal is more than 2 times of the transmission time of the pump pulse in the sensing optical fiber.
The pump light high-low frequency alternative modulation Brillouin optical time domain analysis system further comprises a polarization controller, a light deflection device, an optical isolator, an optical circulator and a pulse signal generator, wherein the polarization controller is arranged between the optical splitter and the electro-optical modulator, the light deflection device and the optical isolator are arranged between the erbium-doped optical fiber amplifier and the sensing optical fiber, a first port of the optical circulator is connected with the output end of the pulse optical amplifier, a second port of the optical circulator is connected with the other end of the sensing optical fiber, and a third port of the optical circulator is connected with the optical filter.
The beam splitter is a 1 x 2 optical fiber coupler, and the beam splitter, the polarization controller, the electro-optic modulator, the erbium-doped optical fiber amplifier, the light beam deflector and the optical isolator are connected through a single-mode optical fiber jumper;
the beam splitter, the single-side band modulator, the pulse light amplifier and the optical circulator are connected through single-mode optical fiber jumpers; the optical filter is connected with the photoelectric detector through a single-mode optical fiber jumper.
Compared with the prior art, the invention has the following beneficial effects:
first, the present invention employs a single sideband modulator to alternately modulate a pump signal to a frequency of
High-frequency sideband pump signals or
The low-frequency sideband pump signal is respectively subjected to stimulated Brillouin action with the low-frequency sideband and the high-frequency sideband of the detection signal through frequency sweeping to generate a gain spectrum and a loss spectrum, and then the signal power is improved by 2 times of that of the traditional BOTDA system through algorithm superposition processing, so that the signal-to-noise ratio of the system is improved.
Secondly, the dynamic Brillouin optical time domain analysis system (Chinese invention patent CN 107764297A) based on the pump pulse frequency sweep utilizes an arbitrary waveform generator to perform frequency modulation on the pump pulse to generate high/low frequency two sidebands.
Thirdly, the invention simultaneously satisfies the frequency difference condition of the detection signal and the pumping signal under the condition of obtaining the gain spectrum and the loss spectrum
Modulation frequency of double side bands of detection signal by electro-optical modulatorf 1Minimum satisfaction
I.e., about 5.5GHz in a specific implementation; meanwhile, the dual-channel microwave signal source modulates the frequency of the high/low-frequency single sideband of the pumping signalf 2And in particular implementation about 5.3 GHz. Compared with the traditional BOTDA system, the modulation frequency of the microwave signal source to the detection signal is about 2f 1. Therefore, the requirement of the invention on the bandwidth required by the device is reduced by 2 times, and the cost required by the system is greatly saved.
Drawings
Fig. 1 is a schematic structural diagram of a brillouin optical time domain analysis system with alternately modulated pump light at high and low frequencies according to an embodiment of the present invention;
fig. 2 is a frequency domain schematic diagram of a brillouin optical time domain analysis system with alternately modulated high and low frequencies of pump light, provided by an embodiment of the present invention.
Fig. 3 is a data processing schematic of the present invention.
In the figure: the system comprises a 1-narrow linewidth laser, a 2-optical splitter, a 3-polarization controller, a 4-electro-optic modulator, a 5-erbium-doped fiber amplifier, a 6-optical scrambler, a 7-optical isolator, an 8-bias controller, a 9-single-sideband modulator, a 10-pulse modulator, an 11-pulse optical amplifier, a 12-programmable microwave signal source, a 13-sensing fiber, a 14-optical circulator, a 15-optical filter, a 16-photoelectric detector and a 17-data acquisition card.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, an embodiment of the present invention provides a brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light, including a narrow linewidth laser 1, an optical splitter 2, a polarization controller 3, an electro-optical modulator 4, an erbium-doped fiber amplifier 5, an optical scrambler 6, an optical isolator 7, a bias controller 8, a single-sideband modulator 9, a pulse modulator 10, a pulsed optical amplifier 11, a programmable microwave signal source 12, a sensing fiber 13, an optical circulator 14, an optical filter 15, an optical detector 16, and a data acquisition card 17.
Specifically, in this embodiment, the light emitted by the narrow linewidth laser 1 is divided into two beams after passing through the optical splitter 2, one beam is used as the detection light to be subjected to double-sideband modulation of carrier suppression by the electro-optical modulator 4, and the obtained frequencies are respectively
And
two sidebands; then the signal is amplified by an erbium-doped fiber amplifier 5, deflected by a deflector 6, transmitted in one direction by an optical isolator 7, enters a sensing fiber 13, and then the probe light carrying Stimulated Brillouin Scattering (SBS) information enters a second port b of a circulator 14.
The other beam of the pumping light is used as pumping light, and enters the sensing optical fiber 13 from the other end after sequentially passing through the single-side band modulator 9, the pulse modulator 10 and the pulse optical amplifier 11; the single-sideband modulator 9 is used for alternately modulating the high frequency and the low frequency of the pump light under the drive of the programmable microwave signal source 12, so that the pump light is alternately generated at the frequency of
With high frequency sidebands and frequencies of
Sweeping the frequency of the low-frequency sideband; the pulse modulator 10 is configured to modulate pump light into a pulse signal, and the pulse light amplifier 11 is configured to perform power amplification on the pulse light, enter the first port a of the optical circulator 14, and enter the other end of the sensing fiber 13 from the second port b of the optical circulator 14; wherein,
for the laser frequency emitted by the narrow linewidth laser 1,f 1in order to detect the frequency-shifted frequency of the light,f 2is the frequency-shifted frequency of the pump light.
The pump light pulse light and the detection light are stimulated to have a Brillouin effect in the sensing optical fiber 13, Brillouin back scattering light enters from the second port b of the optical circulator 14 and exits from the third port c of the optical circulator 14, then high/low frequency sideband signals of scattering signals are filtered out through the optical filter 15, the filtered optical signals enter the photoelectric detector 16 for detection, data acquisition and A/D conversion are carried out through the data acquisition card 17, and data demodulation is carried out in the calculation unit, so that distributed sensing measurement is realized.
Specifically, as shown in FIG. 2, in the present embodiment, the frequency alternates to
With high frequency sidebands and frequencies of
Alternately with the low-frequency side bands of the double-sideband probe light
And high frequency sideband
Brillouin enhancement or brillouin attenuation occurs, and thus a brillouin gain spectrum and a brillouin attenuation spectrum can be alternately acquired by the detector. That is, the pump signal is first modulated by a single sideband modulator into
The high-frequency sideband of the pumping light and the low-frequency sideband of the detection signal are subjected to stimulated Brillouin action to obtain a Brillouin gain spectrum; then the pump signal is modulated into
And performing frequency sweeping on the low-frequency sideband, and generating a stimulated Brillouin action between the low-frequency sideband of the pumping light and the high-frequency sideband of the detection signal to obtain a Brillouin loss spectrum.
In this embodiment, before the system collects data, the high/low frequency sideband signals of the detection signal are filtered out by the optical filter, so as to avoid interference of noise and other signals.
Specifically, the brillouin optical time domain analysis system according to the embodiment further includes a calculation unit connected to the data acquisition card 17, and the calculation unit is configured to perform superposition calculation according to the brillouin gain spectrum and the brillouin loss spectrum acquired by the data acquisition card 17 to obtain the synthesized brillouin gain spectrum.
In this embodiment, after the high/low frequency sideband signals of the probe signal are filtered out, the synthesized brillouin spectrum is obtained through algorithm processing. Power variation for brillouin gain spectrum
Proportional relationship between power change of Brillouin loss spectrum and
proportional relation; as described above
In order to be the brillouin gain factor,
is the power of the pump pulse or pulses,
respectively the power of the high and low frequency sidebands of the detection signal. The total signal power value after being superimposed by the algorithm and
in a proportional relationship. Specifically, when the high-frequency and low-frequency sideband power values of the detection signals are equal, the obtained signal power is 2 times that of the traditional system, and if the noise statistical characteristics of the two signals are independent, the signal-to-noise ratio of the system is improved by 3 dB. The data processing principle is shown in fig. 3, wherein the left graph is a gain spectrum and a loss spectrum respectively, and the right graph is a result obtained by processing the gain spectrum and the loss spectrum through a superposition algorithm.
Specifically, the brillouin optical time domain analysis system with alternately modulated pump light at high and low frequencies provided by this embodiment further includes a pulse signal generator for driving the pulse modulator 10. Further, in this embodiment, the programmable microwave signal source 12 is a dual-channel microwave signal source, and the microwave output from another channel of the dual-channel microwave signal sourceThe signal is used to drive the electro-optical modulator 4. Further, in this embodiment, the types of the programmable microwave signal source 12 are: the double-channel microwave analog signal source of the SLFS-D series of the China satellite Union satellite can be set through software, so that the single-sideband modulator 9 can modulate the pump light alternatively, and the frequency generated alternatively is the frequency
With high frequency sidebands and frequencies of
Sweeping the frequency of the low-frequency sideband; the single sideband modulator 9 adopts a KG-ModBox-SSB series carrier suppression single sideband modulation module; the pulse modulator 10 adopts an OPEAK OAM-SOA-PL type pulse modulator, and the pulse optical amplifier 10 adopts an OPEAK EDFA-C-PL-NS-MB type pulse erbium-doped fiber amplifier; the sensing fiber adopts a G652 series single mode fiber.
Specifically, in this embodiment, the center wavelength of the narrow linewidth laser 1 is 1550.12nm, and the linewidth is less than 1 MHz; the splitting ratio of the beam splitter is 50: 50.
further, in the present embodiment, the frequency shift frequency of the probe lightf 1And frequency shift frequency of pump lightf 2The following conditions are satisfied: 10.5GHz< f 1+ f 2<11GHz and has
Wherein
The spectral width of the brillouin gain spectrum is shown, which is approximately 100 MHz. That is, in the present embodiment, the heat treatment is performed byf 1Andf 2satisfy the requirement of
So that the stimulated Brillouin effect is generated between the detection light and the pump, the bandwidth requirement of the system on a microwave signal source can be reduced,
is a brillouin frequency shift.
Further, in this embodiment, when the pulse modulator 10 modulates the pump light into a pulse signal, the preset interval of the pump pulse signal is greater than 2 times of the transmission time of the pump pulse in the sensing fiber, so as to avoid crosstalk between pulses. Specifically, in this embodiment, the conversion period of the high-low frequency alternative modulation of the pump light may be 1 to 10 times the period of the pump light pulse signal. When the high frequency and the low frequency are modulated alternately, one frequency comprises a plurality of pulse periods, so that the acquisition card can acquire data for multiple times for averaging, and the signal-to-noise ratio of the system is further improved.
Further, in this embodiment, the beam splitter 2 is a 1 × 2 fiber coupler, and the beam splitter 2, the polarization controller 3, the electro-optical modulator 4, the erbium-doped fiber amplifier 5, the light beam deflector 6, and the optical isolator 7 are connected by a single-mode fiber jumper; the beam splitter 2, the single-side band modulator 9, the pulse modulator 10, the pulse light amplifier 11 and the optical circulator 14 are connected through single-mode optical fiber jumpers; the optical filter 15 and the photodetector 16 are connected by a single-mode optical fiber jumper. The connection mode of the single-mode optical fiber jumper can enable the optical path of the system to be more stable, and the measurement result is more accurate.
The invention provides a Brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light
High-frequency sideband pump signals or
The low-frequency sideband pump signal is respectively subjected to stimulated Brillouin action with the low-frequency sideband and the high-frequency sideband of the detection signal through frequency sweeping to generate a gain spectrum and a loss spectrum, and then the signal power is improved by 2 times of that of the traditional BOTDA system through algorithm superposition processing, so that the signal-to-noise ratio of the system is improved. In addition, the frequency shift frequency of the pump light and the probe light of the invention is about the sameCompared with the traditional Brillouin time domain analysis system, the half of the Brillouin frequency shift greatly reduces the bandwidth requirement on a microwave driving device.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A pump light high-low frequency alternative modulation Brillouin optical time domain analysis system is characterized by comprising a narrow linewidth laser (1), wherein light emitted by the narrow linewidth laser (1) is divided into two beams after passing through a light splitter (2), one beam is used as detection light to be subjected to double-sideband modulation of carrier suppression through an electro-optical modulator (4), and the obtained frequencies are respectively
And
two sidebands; then the light is amplified by an erbium-doped fiber amplifier (5) and enters a sensing fiber (13), and the other beam of light is used as pump light and enters the sensing fiber (13) from the other end after sequentially passing through a single-side band modulator (9), a pulse modulator (10) and a pulse light amplifier (11);
the single-sideband modulator (9) is used for alternately modulating the pump light at high and low frequencies under the drive of the programmable microwave signal source (12) so as to alternately generate the pump light with the frequency of
With high frequency sidebands and frequencies of
Sweeping the low-frequency sideband; the pulse modulator (10) is used for modulating the pump light into pulse signals, and the pulse light amplifier (11) is used for amplifying the pulse signals and then sending the amplified pulse signals to the other end of the sensing optical fiber (13); wherein,
is the laser frequency emitted by the narrow linewidth laser (1), f 1in order to detect the frequency-shifted frequency of the light, f 2is the frequency shift frequency of the pump light;
the frequency of the pulse signal is
High frequency sideband and probe light medium frequency of
With low frequency side-band effects, the frequency of the pulse signal being
Of low frequency sidebands and the frequency of the probe light is
The high-frequency sideband of the optical fiber is acted, so that Brillouin gain and Brillouin loss are alternately generated in the sensing optical fiber (13), a Brillouin gain spectrum signal and a Brillouin loss spectrum signal which are emitted from the other end of the sensing optical fiber (13) are received by a photoelectric detector (16) after stray light is filtered by an optical filter (15), and then are collected by a data collection card (17);
frequency shift frequency of probe lightf 1And frequency shift frequency of pump lightf 2The following conditions are satisfied: 10.5GHz< f 1+ f 2<11GHz and has
In which
The spectral width of the brillouin gain spectrum is shown,
is a brillouin frequency shift.
2. The Brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light according to claim 1, further comprising a calculation unit connected to the data acquisition card (17), wherein the calculation unit is configured to perform superposition calculation according to the Brillouin gain spectrum and the Brillouin loss spectrum acquired by the data acquisition card to obtain the synthesized Brillouin gain spectrum.
3. A brillouin optical time domain analysis system with high and low frequency alternative modulation of pump light according to claim 1, further comprising a pulse signal generator for driving the pulse modulator (10).
4. The Brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light according to claim 1, wherein the programmable microwave signal source (12) is a dual-channel microwave signal source, and a microwave signal output from another channel of the dual-channel microwave signal source is used for driving the electro-optical modulator (4).
5. The Brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light according to claim 4, wherein the type of the programmable microwave signal source (12) is as follows: a middle satellite Union SLFS-D series double-channel microwave simulation signal source; the single sideband modulator (9) adopts a KG-ModBox-SSB series carrier suppression single sideband modulation module; the pulse modulator (10) adopts an OPEAK OAM-SOA-PL type pulse modulator, and the pulse optical amplifier (11) adopts an OPEAK EDFA-C-PL-NS-MB type pulse erbium-doped fiber amplifier; the sensing fiber adopts a G652 series single mode fiber.
6. The Brillouin optical time domain analysis system with alternately modulated pump light at high and low frequencies according to claim 1, wherein when the pulse modulator (10) modulates the pump light into a pulse signal, the preset interval of the pulse signal is greater than 2 times of the transmission time of the pulse signal in the sensing fiber.
7. The Brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light according to claim 1, further comprising a polarization controller (3), an optical scrambler (6), an optical isolator (7), an optical circulator (14) and a pulse signal generator, wherein the polarization controller (3) is disposed between the optical splitter (2) and the electro-optical modulator (4), the optical scrambler (6) and the optical isolator (7) are disposed between the erbium-doped fiber amplifier (5) and the sensing fiber (13), a first port of the optical circulator (14) is connected with an output end of the pulse optical amplifier (11), a second port is connected with the other end of the sensing fiber (13), and a third port is connected with the optical filter (15).
8. The Brillouin optical time domain analysis system for high-low frequency alternative modulation of pump light according to claim 7, wherein the optical splitter (2) is a 1 x 2 fiber coupler, and the optical splitter (2), the polarization controller (3), the electro-optical modulator (4), the erbium-doped fiber amplifier (5), the optical scrambler (6), and the optical isolator (7) are connected through a single-mode fiber jumper;
the optical splitter (2), the single-side band modulator (9), the pulse modulator (10), the pulse optical amplifier (11) and the optical circulator (14) are connected through single-mode optical fiber jumpers; the optical filter (15) is connected with the photoelectric detector (16) through a single-mode optical fiber jumper.
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| CN112525073B (en) * | 2020-11-19 | 2022-06-03 | 哈尔滨工业大学 | Structural crack identification method based on Brillouin gain spectrum characteristic parameters |
| CN113049014B (en) * | 2021-03-10 | 2022-04-15 | 太原理工大学 | Time-frequency multiplexing BOTDA system based on pumping light frequency sweep and sensing method |
| CN114279476B (en) * | 2021-12-06 | 2023-06-30 | 太原理工大学 | Distributed optical fiber sensing device based on phase type chaotic laser and measuring method thereof |
| CN117490741A (en) * | 2024-01-03 | 2024-02-02 | 华中科技大学 | Quick Brillouin optical time domain analyzer based on double-sideband optical frequency comb |
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