CN113687158A - High-resolution phi-OTDR distributed optical fiber sensing system and method - Google Patents
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 58
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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- G—PHYSICS
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- 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
- G01D5/36—Forming the light into pulses
Abstract
A high resolution phi-OTDR distributed optical fiber sensing system and method, comprising: the device comprises an ultra-narrow linewidth laser, a polarization controller, an optical splitter, an acousto-optic modulator, an EDFA optical amplifier, an arbitrary waveform generator, an optical circulator, an optical coupler, a narrow-band filter, an EVOA, a photoelectric detector and an oscilloscope. According to the invention, the backscattering signals of the sensing optical fiber at the short distance and the long distance are respectively processed, so that the spatial distribution of the whole optical fiber is obtained, the spatial resolution of the system is improved, the EVOA in the system only attenuates the signals from the short-distance channel, other signals are allowed to pass through without attenuation, the signal saturation of the short-distance channel and the attenuation of the signals of the far-end channel are eliminated, the signal-to-noise ratio is improved, and more sensitive detection is realized.
Description
Technical Field
The invention belongs to the field of on-line monitoring of electrical equipment, and particularly relates to a high-resolution phi-OTDR distributed optical fiber sensing system and method.
Background
Due to the advantages of long monitoring distance, wide monitoring range and the like, the distributed optical fiber sensing system has attracted wide attention in recent years in the aspects of safety monitoring and the like in large distance ranges such as pipelines, railways and the like. The distributed optical fiber sensing system takes an optical fiber as a detection carrier and uses laser as a detection signal, and information of a measured parameter on the whole optical fiber length, which changes along with time in space, can be obtained. The sensing system based on the Optical Time Domain Reflectometer (OTDR) technology has a simple system structure, is stable and easy to realize, can perform characteristic description and fault location on the optical fiber transmission cable, and has become a new concern in the existing distributed optical fiber sensing system.
The traditional OTDR system can only provide loss and reflection profiles of optical links, and the distributed optical fiber sensing system based on phi-OTDR can measure phase change of optical fibers by using a high-coherence narrow-linewidth light source, and has the advantages of high sensitivity, high positioning accuracy, simple data processing and the like. Therefore, the method is suitable for the environment with higher real-time requirement, however, the improvement of the spatial resolution of the distributed optical fiber sensing system based on the phi-OTDR is still limited by other performances.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a high-resolution phi-OTDR distributed optical fiber sensing system and a method thereof, which can improve the spatial resolution of the whole sensing system and inhibit the reduction of the signal-to-noise ratio of the sensing system, thereby realizing more sensitive detection.
The invention adopts the following technical scheme:
a high resolution phi-OTDR distributed fiber sensing system comprising: the system comprises an ultra-narrow linewidth laser, a polarization controller, an optical splitter, an acousto-optic modulator, an EDFA optical amplifier, an arbitrary waveform generator, an optical circulator, an optical coupler, a narrow-band filter, an EVOA, a photoelectric detector and an oscilloscope;
wherein, the continuous light emitted by the ultra-narrow linewidth laser is input into the polarization controller, and the polarization state of the continuous light is controlled by the polarization controller, the optical splitter is connected with the polarization controller and splits the continuous light, the acousto-optic modulator is connected with the optical splitter and modulates the continuous light into optical pulses, the EDFA optical amplifier can amplify the optical pulses, the arbitrary waveform generator is used for generating pulse wave signals, the optical circulator is connected with the EDFA optical amplifier and receives and transmits the optical pulses, the optical coupler is connected with the optical circulator and converts the optical pulses into beat frequency signals, the narrow-band filter can obtain band-pass signals near optical carrier frequency shift, the EVOA is connected with the optical coupler and is used for controlling the attenuation of the optical signals, and the photoelectric detector is used for converting the optical signals into electric signals, and the oscilloscope receives and displays the electric signal.
Preferably, the ultra-narrow linewidth laser is a continuous wave laser with a center wavelength of 1550nm for emitting continuous laser light.
Preferably, the arbitrary waveform generator is configured to generate a pulse wave signal, and the pulse wave signal is a rectangular pulse with a rise/fall time of 2ns, a repetition frequency of 10kHz, a pulse width of 100ns, and a frequency shift of 100 MHz.
Preferably, the optical splitter is an 1/9 optical splitter, and is used for splitting the received continuous laser into two parts, which respectively account for 90% and 10% of the original laser.
The invention also relates to a high-resolution phi-OTDR distributed optical fiber sensing method, which comprises the following steps:
step 1: generating an input pulse by an ultra-narrow linewidth laser;
step 2: modifying the original interrogation signal by adding a separate optical carrier to the input pulse to obtain an optical pulse generated by modulation by the acousto-optic modulator;
and step 3: modeling the propagation of the optical pulse along the fiber as a sum of two backscattered components according to the linearity of the convolution;
and 4, step 4: and after receiving the beat frequency signal, the photoelectric detector converts the beat frequency signal to generate an electric signal.
Preferably, the pulse P is inputstd(t, z) is:
wherein E is0Is the amplitude of the pulsed field, τpIs the pulse width, beta1(z) is the propagation delay, Pcp(t, z) is linear chirp, and β1(z) and Pcp(t, z) satisfy:
where δ v is the total applied chirp.
Preferably, the optical pulse P (t, z) generated by the modulation of the acousto-optic modulator is:
and P isoc(t, z) satisfies:
wherein the content of the first and second substances,
the optical frequency of the photo-carriers.
Preferably, the sum of the two backscatter components, e (t), is:
E(t)＝P(t,z)*r(z)＝Eoc(t)+Ecp(t)
wherein r (z) is the fiber Rayleigh backscattering distribution function, Eoc(t) is a signal corresponding to the added optical carrier, Ecp(t) represents the signal represented by the original signal light.
Preferably, the generated electrical signal i (t) can be represented as:
I(t)＝E(t)Ecc(t)＝Ibb(t)+Ipb(t)
and Ibb(t) and Ipb(t) satisfy:
Ibb(t)＝|Eoc(t)|2+|Ecp(t)|2
wherein E isoc(t) represents the added optical carrier signal;
Ecp(t) represents an intrinsic signal optical signal;
Ecp cc(t) represents the optical signal after convolution of the intrinsic optical signal with the back Rayleigh scattering curve.
Preferably, the method further comprises data demodulation, wherein the data demodulation is based on sub-band processing, an optical carrier with a specific frequency is added into the interrogation pulse, the response of the optical fiber to the chirped pulse is allowed to be extracted from the signal received from the intermediate frequency, the optical fiber response spectrum is divided into a plurality of sub-bands by using a narrow-band filter, the sub-bands are overlapped in a time domain after being finally subjected to inverse transformation, and an averaging operation is performed during sub-band analysis.
The invention has the advantages that compared with the prior art, the invention attenuates the optical signal from the close-distance channel by the EVOA and allows other signals to pass through without attenuation; the backscattering signals of the sensing optical fiber at a short distance and a long distance are respectively processed, so that the spatial distribution of the whole optical fiber is obtained, the signal power close to the transmitting end is attenuated, the signal power close to the far end of the optical fiber is kept at the maximum level, the signal saturation of a short-distance channel and the attenuation of a far-end channel signal are eliminated, and the signal-to-noise ratio is improved; the orthogonal demodulation method is combined, the limitation of the system space resolution is broken through, the signal-to-noise ratio of the whole system is improved by utilizing the moving average technology, and therefore the detection system with high resolution and sensitivity is realized.
The beneficial effects of the invention at least comprise:
1. the invention adds an optical frequency shift in the input pulse under the condition of not reducing the pulse width by a phi-OTDR distributed optical fiber sensing system based on a sub-band processing principle, decomposes the backscattering spectrum of the optical fiber into a plurality of sub-bands by utilizing a digital filtering technology, each sub-band corresponds to the optical fiber response generated by the short optical pulse, and each sub-band has high spatial resolution, thereby reducing the signal-to-noise ratio;
2. after the EVOA is added to a phi-OTDR distributed fiber sensing system, it only attenuates signals from close proximity channels and allows other signals to pass through without attenuation. The backscattering signals of the sensing optical fiber at the near distance and the far distance are respectively processed to obtain the spatial distribution of the whole optical fiber, the signal power close to the transmitting end is attenuated, the signal power close to the far end of the optical fiber is kept at the maximum level, the signal saturation of a near-distance channel and the attenuation of a far-end channel signal are eliminated, and the signal-to-noise ratio is improved.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a high resolution phi-OTDR distributed optical fiber sensing system provided by the present invention;
FIG. 2 is a schematic overall flow diagram of a high-resolution phi-OTDR distributed optical fiber sensing method provided by the present invention.
Detailed Description
The present application is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present application is not limited thereby.
Referring to the schematic diagram of fig. 1, the system is an overall structural schematic diagram of the high-resolution phi-OTDR distributed optical fiber sensing system according to the present invention, and the system includes an ultra-narrow linewidth laser, a polarization controller, an optical splitter, an acousto-optic modulator, an EDFA optical amplifier, an arbitrary waveform generator, an optical circulator, an optical coupler, a narrow-band filter, an EVOA, a photodetector, and an oscilloscope.
The continuous light emitted by the ultra-narrow linewidth laser is input into a polarization controller, the polarization state of the continuous light is controlled by the polarization controller, an optical splitter can split the continuous light, an acousto-optic modulator is connected with the optical splitter and modulates the continuous light into optical pulses, an EDFA optical amplifier can amplify the optical pulses and compensate loss introduced by the optical splitter, an arbitrary waveform generator is used for generating pulse wave signals, the optical circulator is connected with the EDFA optical amplifier and receives and transmits the optical pulses, an optical coupler is connected with the optical circulator and converts the optical pulses into beat frequency signals, a narrow-band filter can obtain band-pass signals near optical carrier frequency shift, an EVOA is connected with the optical coupler and is used for controlling attenuation of the optical signals, specifically the EVOA can attenuate signals from a short-distance channel and allows other signals to pass through without attenuation, wherein the short-distance channel signals are signals within hundred meters, the photoelectric detector is used for converting optical signals into electric signals, the electric signals are input into the oscilloscope, and the oscilloscope is used for displaying the electric signals.
Specifically, the ultra-narrow linewidth laser is a continuous wave laser with the central wavelength of 1550nm and can generate continuous light; the polarization controller is used for controlling the polarization state of the light; the optical splitter adopts an 1/9 optical splitter, and the 1/9 optical splitter can split continuous light generated by the laser into two parts; the acousto-optic modulator is used for modulating 90% of continuous light into light pulses; the EDFA is used for amplifying the optical power of the optical pulse, and the rise time of the EDFA is 1 ns; the arbitrary waveform generator is used for generating a pulse wave signal of the acousto-optic modulator, the pulse wave signal is a rectangular pulse, the rising/falling time of the rectangular pulse is 2ns, the repetition frequency is 10kHz, the pulse width is 100ns, and the frequency shift is 100 MHz; the optical circulator is used for injecting the optical pulse generated by the modulation of the acousto-optic modulator into the optical fiber to be measured and receiving backward Rayleigh scattering light in the optical fiber to be measured and injecting the backward Rayleigh scattering light into the optical coupler, and the optical coupler adopts a 2 x 2 optical coupler; the narrow-band filter is used for obtaining a band-pass signal near the frequency shift of the optical carrier, and the EVOA is used for controlling the attenuation of the optical signal; the photoelectric detector is used for converting the optical signal into an electric signal; the oscilloscope is used for displaying and processing the electric signal; the length of the measured optical fiber is 100m, and the measured optical fiber is a standard single-mode optical fiber.
Furthermore, in the high-resolution phi-OTDR distributed optical fiber sensing system provided by the invention, the continuous laser with the wavelength of 1550nm generated by the ultra-narrow linewidth laser passes through the polarization controller and then is injected into the 1/9 optical splitter; 1/9 the optical splitter divides the laser into two parts, which respectively account for 90% and 10% of the total laser, wherein 90% of the laser enters the acousto-optic modulator and is modulated into optical pulse signals, and 10% of the laser directly enters the 2 x 2 optical coupler of the splitting ratio 1/1 as intrinsic light; the optical pulse signals generated by the acousto-optic modulator are amplified in optical power through an EDFA optical amplifier, and the amplified pulse light is injected into the optical fiber to be detected through an optical circulator; after a backward Rayleigh scattering signal generated by the pulsed light in the optical fiber to be detected passes through the EVOA, the backward Rayleigh scattering signal is injected into the 2 x 2 optical coupler through the optical circulator to form a beat frequency signal; the narrow-band filter is used for obtaining a band-pass signal near the optical carrier frequency shift, and the beat signal is converted into an electric signal through the photoelectric detector and is input into the oscilloscope for display processing.
Further, referring to the schematic diagram of fig. 2, the present invention further provides a high-resolution phi-OTDR distributed optical fiber sensing method, which can be implemented based on the above-mentioned high-resolution phi-OTDR distributed optical fiber sensing system, and the method specifically includes the following steps:
step 1: generation of input pulses P by ultra narrow linewidth lasersstd(t,z)：
Wherein E is0Is the amplitude of the pulsed field, τpIs the pulse width, beta1(z) is the propagation delay, Pcp(t, z) is linear chirp, and β1(z) and Pcp(t, z satisfy:
where φ v is the total applied chirp,
step 2: modifying the original interrogation signal by adding a separate optical carrier to the input pulse, resulting in an optical pulse P (t, z) generated by modulation by the acousto-optic modulator:
and P isoc(t, z) satisfies:
wherein the content of the first and second substances,
the optical frequency of the photo-carriers.
And step 3: the propagation of the light pulse P (t, z) along the fiber is modeled as the sum of two backscattered components e (t) according to the linearity of the convolution:
E(t)＝p(t，z)*r(z)＝Eoc(t)+Ecp(t)
wherein r (z) is the fiber Rayleigh backscattering distribution function, Eoc(t) is a signal corresponding to the added optical carrier, Ecp(t) represents the signal represented by the original signal light.
And 4, step 4: after the photodetector receives the beat signal, the electrical signal i (t) generated by conversion can be represented as:
I(t)＝E(t)Ecc(t)＝Ibb(t)+Ipb(t)
and Ibb(t) and Ipb(t) satisfy:
Ibb(t)＝|Eoc(t)|2+|Ecp(t)|2
wherein E isoc(t) represents the added optical carrier signal;
Ecp(t) represents an intrinsic signal optical signal;
Ecp cc(t) represents the optical signal after convolution of the intrinsic optical signal with the back Rayleigh scattering curve.
Due to the application to Pcp(t, z), any sub-window of the input pulse in P (t, z) will produce a particular sub-slot. The spectrum of each sub-band corresponds to the spectrum generated when the fibre is interrogated with a short pulse, thus ensuring a high spatial resolution.
Further, the high resolution phi-OTDR distributed optical fiber sensing method further comprises data demodulation, wherein the data demodulation is based on sub-band processing, an optical carrier with a specific frequency is added into the interrogation pulse, the response of the optical fiber to the chirped pulse is allowed to be extracted from the signal received from the intermediate frequency, the response spectrum of the optical fiber is divided into a plurality of sub-bands by using a narrow-band filter, finally, after inverse transformation, the sub-bands are overlapped in a time domain, and averaging operation is performed during sub-band analysis. Analysis of any one of the sub-bands ensures that the phi-OTDR recorded data has high resolution, but reduces signal-to-noise ratio and maximum measurable strain temperature change; by performing the averaging operation during the sub-band analysis, the signal-to-noise ratio can be reduced.
The method adds an optical carrier frequency shift of a specific frequency to the optical pulse through an acousto-optic modulator, and allows the response of the optical fiber to the optical pulse to be extracted from a signal received at an intermediate frequency. By using digital filters, the fiber response spectrum is divided into multiple sub-bands, which eventually overlap. Analysis of any of these sub-bands ensures that the phi-OTDR recorded data has high resolution, but reduces the signal-to-noise ratio and maximum measurable strain temperature change. By performing the averaging operation during the sub-band analysis, the signal-to-noise ratio can be improved.
The present invention has an advantageous effect in that it attenuates an optical signal from a close-range channel and allows other signals to pass through without attenuation, through sub-band processing and addition of EVOA, compared to the prior art. The backscattering signals of the sensing optical fiber at the near distance and the far distance are respectively processed to obtain the spatial distribution of the whole optical fiber, the signal power close to the transmitting end is attenuated, the signal power close to the far end of the optical fiber is kept at the maximum level, the signal saturation of a near-distance channel and the attenuation of a far-end channel signal are eliminated, and the signal-to-noise ratio is improved. The orthogonal demodulation method is combined, the limitation of the system space resolution is broken through, the signal-to-noise ratio of the whole system is improved by utilizing the moving average technology, and therefore the detection system with high resolution and sensitivity is realized.
1. The invention respectively processes the backscattering signals of the sensing optical fiber at a short distance and a long distance so as to obtain the spatial distribution of the whole optical fiber. The signal power near the launch end is attenuated while the signal power near the distal end of the fiber is maintained at a maximum level;
2. signal saturation of the near channel and attenuation of the far channel signal are eliminated, the EVOA attenuates only the signal from the near channel and allows other signals to pass through without attenuation, thereby compensating the signal-to-noise ratio of the system.
The term is defined as:
OTDR: optical time-domain reflectometer, optical time domain reflectometer;
EDFA optical amplifier: an erbium-doped optical amplifier;
EVOA: an electrical variable optical attenuator.
The present applicant has described and illustrated embodiments of the present invention in detail with reference to the accompanying drawings, but it should be understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for limiting the scope of the present invention, and on the contrary, any improvement or modification made based on the spirit of the present invention should fall within the scope of the present invention.
Claims (10)
1. A high resolution phi-OTDR distributed fiber sensing system, comprising: the system comprises an ultra-narrow linewidth laser, a polarization controller, an optical splitter, an acousto-optic modulator, an EDFA optical amplifier, an arbitrary waveform generator, an optical circulator, an optical coupler, a narrow-band filter, an EVOA, a photoelectric detector and an oscilloscope;
wherein, the continuous light emitted by the ultra-narrow linewidth laser is input into the polarization controller, and the polarization state of the continuous light is controlled by the polarization controller, the optical splitter is connected with the polarization controller and splits the continuous light, the acousto-optic modulator is connected with the optical splitter and modulates the continuous light into optical pulses, the EDFA optical amplifier can amplify the optical pulses, the arbitrary waveform generator is used for generating pulse wave signals, the optical circulator is connected with the EDFA optical amplifier and receives and transmits the optical pulses, the optical coupler is connected with the optical circulator and converts the optical pulses into beat frequency signals, the narrow-band filter can obtain band-pass signals near optical carrier frequency shift, the EVOA is connected with the optical coupler and is used for controlling the attenuation of the optical signals, and the photoelectric detector is used for converting the optical signals into electric signals, and the oscilloscope receives and displays the electric signal.
2. The high resolution phi-OTDR distributed optical fiber sensing system of claim 1,
the ultra-narrow linewidth laser is a continuous wave laser with the central wavelength of 1550nm and is used for emitting continuous laser.
3. The high resolution phi-OTDR distributed optical fiber sensing system of claim 1 or 2,
the arbitrary waveform generator is used for generating a pulse wave signal, the pulse wave signal is a rectangular pulse, the rising/falling time of the pulse wave signal is 2ns, the repetition frequency is 10kHz, the pulse width is 100ns, and the frequency shift is 100 MHz.
4. The high resolution phi-OTDR distributed optical fiber sensing system of claim 3,
the optical splitter is an 1/9 optical splitter and is used for splitting the received continuous laser into two parts which respectively account for 90% and 10% of the original laser.
5. A high-resolution phi-OTDR distributed optical fiber sensing method based on the high-resolution phi-OTDR distributed optical fiber sensing system of any one of claims 1-4 is characterized by comprising the following steps:
step 1: generating an input pulse by an ultra-narrow linewidth laser;
step 2: modifying the original interrogation signal by adding a separate optical carrier to the input pulse to obtain an optical pulse generated by modulation by the acousto-optic modulator;
and step 3: modeling the propagation of the optical pulse along the fiber as a sum of two backscattered components according to the linearity of the convolution;
and 4, step 4: and after receiving the beat frequency signal, the photoelectric detector converts the beat frequency signal to generate an electric signal.
6. The high resolution phi-OTDR distributed optical fiber sensing method of claim 5,
input pulse Pstd(t, z) is：
Wherein E is0Is the amplitude of the pulsed field, τpIs the pulse width, beta1(z) is the propagation delay, Pcp(t, z) is linear chirp, and β1(z) and Pcp(t, z) satisfy:
where δ v is the total applied chirp.
7. The high resolution phi-OTDR distributed optical fiber sensing method of claim 6,
the optical pulse P (t, z) generated by the modulation of the acousto-optic modulator is as follows:
and P isoc(t, z) satisfies:
wherein the content of the first and second substances,
the optical frequency of the photo-carriers.
8. The high resolution phi-OTDR distributed optical fiber sensing method of claim 7,
the sum of the two backscatter components e (t) is:
E(t)＝P(t，z)*r(z)＝Eoc(t)+Ecp(t)
wherein r (z) is the fiber Rayleigh backscattering distribution function, Eoc(t) is a signal corresponding to the added optical carrier, Ecp(t) represents the signal represented by the original signal light.
9. The high resolution phi-OTDR distributed fiber sensing method of claim 8,
the generated electrical signal i (t) can be represented as:
I(t)＝E(t)Ecc(t)＝Ibb(t)+Ipb(t)
and Ibb(t) and Ipb(t) satisfy:
Ibb(t)＝|Eoc(t)|2+|Ecp(t)|2
wherein E isoc(t) represents the added optical carrier signal;
Ecp(t) represents an intrinsic signal optical signal;
Ecp cc(t) represents the optical signal after convolution of the intrinsic optical signal with the back Rayleigh scattering curve.
10. The high resolution phi-OTDR distributed fiber sensing method of claim 9,
and further comprising data demodulation based on sub-band processing, adding an optical carrier of a specific frequency to the interrogation pulse, allowing to extract the response of the fiber to the chirped pulse from the signal received at intermediate frequency, dividing the fiber response spectrum into a plurality of sub-bands by using a narrow band filter, finally performing an inverse transformation, overlapping in the time domain, and performing an averaging operation during sub-band analysis.
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| US20190288475A1 (en) * | 2019-01-31 | 2019-09-19 | University Of Electronic Science And Technology Of China | Long-distance fiber optic distributed acoustic sensing amplification system and method thereof |
| CN110160569A (en) * | 2019-04-24 | 2019-08-23 | 国网浙江省电力有限公司信息通信分公司 | For the noise-reduction method of distributing optical fiber sensing signal, system and storage medium |
| CN110375841A (en) * | 2019-07-25 | 2019-10-25 | 上海交通大学 | Vibration sensing method based on distribution type fiber-optic acoustic wave sensing system |
| CN111854918A (en) * | 2020-07-01 | 2020-10-30 | 国网河南省电力公司焦作供电公司 | Sub-band processing method for improving spatial resolution of distributed optical fiber detection |
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