CN115901043A - Power cable external force monitoring system and method based on distributed optical fiber sensing - Google Patents
Power cable external force monitoring system and method based on distributed optical fiber sensing Download PDFInfo
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Abstract
A power cable external force monitoring system and method based on distributed optical fiber sensing are disclosed, wherein the monitoring system comprises: a laser, 50; when a power cable to be detected vibrates, acquiring light with vibration information through a Michelson interference system and a phase-sensitive optical time domain reflectometer system to obtain light information; obtaining frequency change information of vibration information by analyzing optical information of a Michelson interference system; received by analysing phase-sensitive optical time-domain reflectometry systems
And obtaining amplitude information of the optical information according to the back Rayleigh scattering information, and obtaining the vibration position according to the amplitude information. By means of Michelson interference structures and
combined, michelson structureThe vibration frequency characteristics are analyzed, and then,
by analyzing the vibration position, the invention can effectively reduce the complexity of data analysis and improve the calculation speed.
Description
Technical Field
The invention belongs to the technical field of power cables, and particularly relates to a power cable external force monitoring system and method based on distributed optical fiber sensing.
Background
The power cable is widely distributed, the operation environment is complex, the problem of cable external force damage caused by the actions of engineering machinery construction, theft, modification and the like is solved, the operation safety of the cable is seriously threatened, and an effective monitoring and early warning method is lacked. By detecting the vibration signal of the external force applied to the cable, the existence of the external force can be determined and the stress point can be positioned. The traditional piezoelectric sensor can only carry out quasi-distributed measurement on a plurality of monitoring points, and cannot realize full-distributed measurement. And the volume is large, and the cable cannot be arranged and used in the modes of burying, power cable pipes and the like. Compared with the traditional piezoelectric sensor, the distributed optical fiber sensor has the advantages of full distribution, small volume, wide measurement range, electromagnetic interference resistance and the like.
In the prior art, the Mach-Zehnder interference needs to arrange a photoelectric detector at the tail end of an optical fiber and needs an independent signal loop to return signals, the arrangement process is complicated, and the signals are easily interfered in the transmission process. And the Michelson interference does not need to set up a photoelectric detector at the tail end of the optical fiber, and a signal can be obtained through the return end of the optical fiber circulator at the laser emission side, so that the arrangement is convenient. Under the long distance monitoring operating mode, the structure is interfered to michelson is simpler, and conveniently arranges.
Prior art 1 (CN 102997946A) discloses a "fiber distributed disturbance sensor and disturbance positioning method thereof", which includes: the double-Michelson interferometer is provided with a first Michelson interference optical path and a second Michelson interference optical path, and reflectors of the double-Michelson interferometer are Faraday rotation mirrors with rotation angles of 45 degrees; the system comprises a preprocessing module, a frequency spectrum analysis module and a disturbance positioning module; the disturbance positioning method applying the optical fiber distributed disturbance sensor comprises the following steps: s1: respectively obtaining a first disturbed interference signal and a second disturbed interference signal through the double Michelson interferometer; s2: respectively preprocessing the first and second disturbed interference signals; s3: respectively carrying out spectrum analysis on the preprocessed first disturbed interference signal and the preprocessed second disturbed interference signal; s4: and performing inverse solution processing on the spectrum analysis results of the first and second disturbed interference signals to obtain disturbed position information. The disadvantage of the prior art document 1 is that the calculation process is complicated. The data processing process is simple and convenient, and the calculation speed can be effectively improved.
Prior art 2 (CN 111238551B) discloses "a distributed phase-sensitive optical time domain reflectometer sensing system and phase extraction method", the method includes: at a transmitting end, modulating signal light into pulse light through an acousto-optic modulator, injecting the pulse light into a sensing optical fiber through a circulator, and outputting Rayleigh scattering light reflected from the sensing optical fiber through the circulator, wherein the pulse light becomes a single-sideband signal under the action of frequency shift of the acousto-optic modulator; and at a receiving end, mixing the local oscillator light and Rayleigh scattered light output by the circulator in a second coupler, wherein the optical signal after mixing is a single sideband signal, performing photoelectric conversion on the optical signal after mixing through a single photoelectric detector, performing band-pass filtering on the electric signal after photoelectric conversion, taking one sideband of the filtered electric signal, and performing digital signal processing on the extracted sideband to obtain the position and the phase of the optical fiber disturbance signal. The prior art document 2 has a disadvantage in that it uses only the phase-sensitive optical time domain reflectometer technique, and its response characteristic to frequency is poor. The Michelson interference structure has better frequency response effect.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a power cable external force monitoring system and method based on distributed optical fiber sensing, which can obtain spatial and temporal multidimensional distribution information of vibration information, and measure and monitor the spatial and temporal distribution of a vibration field in real time.
The invention adopts the following technical scheme.
Power cable external force monitoring system based on distributed optical fiber sensing includes: a laser, 50;
an optical michelson interference system comprising: the device comprises a first optical fiber circulator, a one-to-two optical fiber coupler, a reference arm optical fiber, a measuring arm optical fiber, a first Faraday reflector, a second Faraday reflector, a photoelectric detector and a collecting card;
the phase sensitive optical time domain reflectometry system comprises: a balanced photodetector, a 2 x 2 coupler, a 90,
a sensing optical fiber;
laser output by the laser passes through 50: the 50 optical fiber coupler is divided into two branches, and the laser of the two branches respectively enters an optical Michelson interference system and a phase-sensitive optical time domain reflectometer system;
laser entering the optical Michelson interference system passes through a first optical fiber circulator and a one-to-two coupler, light beams are respectively input into a reference arm optical fiber and a measuring arm optical fiber, the output end of the reference arm optical fiber is connected with a first Faraday reflector, the output end of the measuring arm optical fiber is connected with a second Faraday reflector, the return end of the first optical fiber circulator is connected with a photoelectric detector, optical information is converted into electrical information, and the electrical information is sent into an acquisition card for data acquisition;
the laser entering the phase sensitive optical time domain reflectometry system passes through 90: the 10 coupler is divided into two branches, the 90 proportion of branch laser passes through an acousto-optic modulator and an erbium-doped fiber amplifier, a second fiber circulator enters an OTDR sensing fiber, the return end of the second fiber circulator and the 10 proportion of branch laser enter a 2 x 2 fiber coupler and then enter a balance photoelectric detector, the balance photoelectric detector converts optical information into electrical information, and the electrical information is sent to an acquisition card for data acquisition.
The laser is used for emitting laser;
the 50;
the first fiber optic circulator is used to connect 50: the device comprises a 50 optical fiber coupler, a one-to-two optical fiber coupler and a photoelectric detector, wherein return light of the one-to-two optical fiber coupler is injected into the photoelectric detector;
the one-to-two coupler is used for connecting the optical fiber circulator, the reference arm optical fiber and the measuring arm optical fiber;
the first Faraday reflector is used for reflecting light information to enable the light information of the reference arm optical fiber to return along the original optical path;
the second Faraday reflector is used for reflecting the optical information, so that the optical information of the optical fiber of the measuring arm returns along the original optical path;
the photodetector is used for receiving the return light injected by the optical fiber circulator from the one-to-two optical fiber coupler.
The acousto-optic modulator is used for modulating optical information;
the erbium-doped fiber amplifier is used for improving the optical power;
the second optical fiber circulator is used for connecting the erbium-doped optical fiber amplifier,
A sensing fiber and a 2 x 2 fiber coupler. Will be/are>
Injecting backward Rayleigh scattered light returned by the sensing optical fiber into the 2 x 2 optical fiber coupler;
the balanced photoelectric detector is used for receiving the optical information from the 2 x 2 optical fiber coupler 12 and converting the received optical information into electric information; carrying out differential amplification detection on interference light information;
90:10 coupler for connecting 50:50 fiber coupler, 2 x 2 fiber coupler and acousto-optic modulator, the laser light is modulated according to a 90: the 10 proportion is respectively input into an acousto-optic modulator and a 2 multiplied by 2 optical fiber coupler;
a 2 x 2 fiber coupler is used to modulate the optical phase.
Preferably, the acquisition card is used to acquire information from the photodetector and the balancing photodetector.
Preferably, the sensing optical fiber is adhered to the outer surface of the power cable and fixed by an adhesive.
The external force monitoring method of the power cable based on the distributed optical fiber sensing comprises the following steps:
step 1, when a power cable to be detected vibrates, acquiring light with vibration information through a Michelson interference system and a phase-sensitive optical time domain reflectometer system to obtain light information;
received by analysing phase-sensitive optical time domain reflectometry systems
And obtaining amplitude information of the optical information according to the back Rayleigh scattering information, and obtaining the vibration position according to the amplitude information.
Preferably, in step 2, the information from the balanced photodetector is demodulated, and the amplitude information of the sampled information is calculated by band-pass filtering, quadrature demodulation and low-pass filtering.
The quadrature demodulation process is as follows:
in the formula (I), the compound is shown in the specification,
n represents the serial number of the sample points,
n represents the number of total sample points,
s (n) represents the sampling information,
cos(Δω n n) represents I co-frequency orthogonal information,
sin(Δω n n) represents Q same-frequency orthogonal information,
Δω n ＝2πΔf/f s ，f s representing the sampling rate of the acquisition card, af representing the frequency of the modulation information,
E s (n) represents the light field intensity of the information light,
E o (n) represents the optical field intensity of the local oscillator light,
Y I the I information obtained by the operation is shown,
Y Q the calculated Q information is represented.
Preferably, the sum frequency term in the I and Q information is obtained through quadrature demodulation
And
the double frequency is filtered by a low-pass filter to obtain the information which contains the external disturbance>
And
and/or>
And &>
The relationship of (a) to (b) is as follows:
in the formula (I), the compound is shown in the specification,
Y I ' denotes the I information after passing through the low pass filter,
Y Q ' denotes the Q information after passing through the low pass filter.
Y obtained from low-pass filtering I ' and Y Q ' the amplitude information of the obtained sampling information is as follows:
according to the amplitude information, the serial number of a sampling point at the vibration point at the protrusion of the amplitude is obtained, the serial number of the sampling point is multiplied by sampling interval time and light speed, the product is divided by the refractive index of the optical fiber, and the numerical value of the calculation result is divided by 2, namely the distance between the vibration point and the transmitting end.
The invention has the advantages that compared with the prior art,
the Michelson interference structure is more sensitive to the frequency spectrum characteristic response of vibration information and can compensate
The structure has the disadvantage of poor response to spectral features. Has the advantages of wide vibration frequency response range and high spatial resolution. Using only
The vibration information frequency and position are measured, the data analysis process is complicated, but the vibration information frequency and the vibration information position are analyzed through a Michelson interference structure and->
In combination, the Michelson structure analyzes the vibration frequency characteristic->
And the vibration position is analyzed, so that the data analysis complexity can be effectively reduced, and the calculation speed is improved.
Drawings
FIG. 1 is a structural diagram of a power cable external force monitoring system based on distributed optical fiber sensing according to the present invention;
the reference signs are:
1-laser, 2-50 fiber coupler, 3-first fiber circulator, 4-one-to-two fiber coupler, 5-reference arm fiber, 6-measurement arm fiber, 7-first Faraday reflector, 8-second Faraday reflector, 9-photodetector, 10-acquisition card, 11-balanced photodetector, 12-coupler, 13-90 fiber coupler, 14-acousto-optic modulator, 15-erbium-doped fiber amplifier, 16-second fiber circulator,
a sensing fiber.
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.
Example 1.
As shown in fig. 1, the external force monitoring system for power cable based on distributed optical fiber sensing includes: a laser 1, 50;
an optical michelson interference system comprising: a first optical fiber circulator 3, a one-to-two optical fiber coupler 4, a reference arm optical fiber 5, a measuring arm optical fiber 6, a first Faraday reflector 7, a second Faraday reflector 8, a photoelectric detector 9, an acquisition card 10, a balance photoelectric detector 11, a 2 multiplied by 2 coupler 12,
the phase sensitive optical time domain reflectometry system comprises: 90,
the optical fiber 17 is sensed and, in this case,
preferably, the laser 1 is a 1550nm laser in this embodiment.
The laser 1 is used for emitting laser;
50;
the laser light output by the laser 1 passes through 50:50 the optical fiber coupler 2 is divided into two branches, and the laser of the two branches respectively enters an optical Michelson interference system and a phase-sensitive optical time domain reflectometer system;
laser entering the optical Michelson interference system passes through the first optical fiber circulator 3 and the one-to-two coupler 4 to input light beams into the reference arm optical fiber 5 and the measuring arm optical fiber 6 respectively, the output end of the reference arm optical fiber 5 is connected with the first Faraday reflector 7, and the output end of the measuring arm optical fiber-6 is connected with the second Faraday reflector 8. The return end of the first optical fiber circulator 3 is connected with a photoelectric detector 9, optical information is converted into electrical information, and the electrical information is sent to an acquisition card 10 for data acquisition.
The first fiber optic circulator 3 is used to connect 50:50 the optical fiber coupler 2, the one-to-two optical fiber coupler 4 and the photodetector 9, and injects the return light of the one-to-two optical fiber coupler 4 into the photodetector 9.
A one-to-two coupler 4 is used to connect the fiber circulator 3, the reference arm fiber 5 and the measurement arm fiber 6.
The first faraday mirror 7 is used to reflect the optical information and return the optical information of the reference arm optical fiber 5 along the original optical path.
The second faraday mirror 8 is used to reflect the optical information and return the optical information of the measurement arm optical fiber 6 along the original optical path.
The photodetector 9 is used for receiving the return light from the one-to-two optical fiber coupler 4 injected by the optical fiber circulator 3.
The laser entering the phase sensitive optical time domain reflectometry system passes through 90: the coupler 13 of the 10 is divided into two branches, the branched laser with the proportion of 90 passes through an acousto-optic modulator 14 and an erbium-doped fiber amplifier 15, and a second fiber circulator 16 enters an OTDR sensing fiber 17. The return end of the second fiber circulator 16 enters the 2 × 2 fiber coupler 12 together with the branched laser light of the ratio 10, and then enters the balanced photodetector 11. The balanced photoelectric detector 11 converts the optical information into electrical information, and sends the electrical information to the acquisition card 10 for data acquisition.
The acousto-optic modulator 14 is used to modulate optical information.
The erbium-doped fiber amplifier 15 is used to boost the optical power.
The second optical fiber circulator 16 is used for connecting the erbium-doped optical fiber amplifier 15,
A sensing fiber 17 and a 2 x 2 fiber coupler 12. Will->
The backward rayleigh scattered light returned from the sensing fiber 17 is injected into the 2 x 2 fiber coupler 12.
The balanced photodetector 11 is used for receiving the optical information from the 2 × 2 fiber coupler 12 and converting the received optical information into electrical information. And carrying out differential amplification detection on the interference light information.
90:10 coupler 13 for connecting 50:50 fiber coupler 2, 2 x 2 fiber coupler 12 and acousto-optic modulator 14, laser light is modulated according to a 90: the ratio of 10 is inputted to the acousto-optic modulator 14 and the 2 × 2 fiber coupler 12, respectively.
The 2 x 2 fiber coupler 12 is used to modulate the optical phase.
The acquisition card 10 is used to collect information from the photo detector 9 and the balancing photo detector 11.
The sensing optical fiber 17 is adhered to the outer surface of the power cable and fixed by an adhesive.
Example 2.
The external force monitoring method of the power cable based on the distributed optical fiber sensing comprises the following steps:
step 1, when the power cable to be detected vibrates, acquiring light with vibration information through a Michelson interference system and a phase-sensitive optical time domain reflectometer system to obtain light information, wherein the light information comprises vibration information generated by actions of engineering instruments such as an electric drill, an electric hammer, a shovel and an excavator.
Received by analytically balanced photodetectors
Obtaining the position information of the vibration information by the back Rayleigh scattering information;
when the power cable to be tested is vibrated,
the energy of the vibration position in the back rayleigh scattering information changes.
Optical information is acquired by the photoelectric detector, the balance photoelectric detector and the acquisition card. And carrying out spectrum analysis on the optical information from the photoelectric detector to obtain the frequency characteristic of the vibration information. Demodulating the information from the balanced photodetector, band-pass filtering, digital quadrature demodulation, low-pass filtering,
and 3, obtaining the vibration position by observing the energy change.
The Quadrature Demodulation (In-phase/Quadrature Demodulation) process is as follows: the quadrature I and Q information obtained by S (n) may be expressed as:
in the formula (I), the compound is shown in the specification,
n represents the serial number of the sampling point,
n represents the number of total sample points,
s (n) represents the sampling information,
cos(Δω n n) represents I co-frequency orthogonal information,
sin(Δω n n) represents Q co-frequency orthogonal information,
Δω n ＝2πΔf/f s ，f s representing the sampling rate of the acquisition card, af representing the frequency of the modulation information,
E s (n) represents the light field intensity of the information light,
E o (n) represents the optical field intensity of the local oscillator light,
Y I representing the I signal obtained by the operationIn the form of a capsule, the particles,
Y Q represents the Q information obtained by the operation,
I. sum frequency term in Q information
And &>
The medium frequency is twice of the AOM frequency shift, and the double frequency is filtered by a low-pass filter to obtain the information on the external disturbance>
And &>
Y I ' and Y Q ' and>
and &>
The relationship of (c) is as follows:
in the formula (I), the compound is shown in the specification,
Y I ' denotes the I information after passing through the low pass filter,
Y Q ' indicates the Q information after passing through the low-pass filter,
further, amplitude information of S (n) can be obtained, and can be expressed as:
according to the amplitude information, the serial number of a sampling point at the vibration point at the protrusion of the amplitude is obtained, the serial number of the sampling point is multiplied by sampling interval time and light speed, the product is divided by the refractive index of the optical fiber, and the numerical value of the calculation result is divided by 2, namely the distance between the vibration point and the transmitting end.
The invention has the advantages that compared with the prior art,
the Michelson interference structure is more sensitive to the frequency spectrum characteristic response of vibration information and can compensate
The structure has poor response to the spectrum characteristics. Has the advantages of wide vibration frequency response range and high spatial resolution. Using only
The vibration information frequency and position are measured, the data analysis process is complicated, but the vibration information frequency and the vibration information position are analyzed through a Michelson interference structure and->
In combination, the Michelson structure analyzes the vibration frequency characteristic->
And the vibration position is analyzed, so that the data analysis complexity can be effectively reduced, and the calculation speed is improved.
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. Power cable external force monitoring system based on distributed optical fiber sensing, its characterized in that, monitoring system includes: a laser, 50;
an optical michelson interference system comprising: the device comprises a first optical fiber circulator, a one-to-two optical fiber coupler, a reference arm optical fiber, a measuring arm optical fiber, a first Faraday reflector, a second Faraday reflector, a photoelectric detector and a collecting card;
the phase-sensitive optical time domain reflectometry system includes: a balanced photodetector, a 2 x 2 coupler, a 90,
a sensing optical fiber;
laser output by the laser passes through 50: the 50 optical fiber coupler is divided into two branches, and the laser of the two branches respectively enters an optical Michelson interference system and a phase-sensitive optical time domain reflectometer system;
laser entering the optical Michelson interference system passes through a first optical fiber circulator and a one-to-two coupler, light beams are respectively input into a reference arm optical fiber and a measuring arm optical fiber, the output end of the reference arm optical fiber is connected with a first Faraday reflector, the output end of the measuring arm optical fiber is connected with a second Faraday reflector, the return end of the first optical fiber circulator is connected with a photoelectric detector, optical information is converted into electrical information, and the electrical information is sent into an acquisition card for data acquisition;
the laser entering the phase sensitive optical time domain reflectometry system passes through 90: the 10 coupler is divided into two branches, the 90 proportion of branch laser passes through an acousto-optic modulator and an erbium-doped fiber amplifier, a second fiber circulator enters an OTDR sensing fiber, the return end of the second fiber circulator and the 10 proportion of branch laser enter a 2 x 2 fiber coupler and then enter a balance photoelectric detector, the balance photoelectric detector converts optical information into electrical information, and the electrical information is sent to an acquisition card for data acquisition.
2. The power cable external force monitoring system based on distributed optical fiber sensing as claimed in claim 1, wherein:
the laser is used for emitting laser;
the 50;
the first fiber optic circulator is used to connect 50: the device comprises a 50 optical fiber coupler, a one-to-two optical fiber coupler and a photoelectric detector, wherein return light of the one-to-two optical fiber coupler is injected into the photoelectric detector;
the one-to-two coupler is used for connecting the optical fiber circulator, the reference arm optical fiber and the measuring arm optical fiber;
the first Faraday reflector is used for reflecting light information to enable the light information of the reference arm optical fiber to return along the original optical path;
the second Faraday reflector is used for reflecting the optical information to return the optical information of the optical fiber of the measuring arm along the original optical path;
the photodetector is used for receiving the return light injected by the optical fiber circulator from the one-to-two optical fiber coupler.
3. The system for monitoring external force of power cable based on distributed optical fiber sensing according to claim 1, wherein:
the acousto-optic modulator is used for modulating optical information;
the erbium-doped fiber amplifier is used for improving the optical power;
the second optical fiber circulator is used for connecting the erbium-doped optical fiber amplifier,
A sensing fiber and a 2 x 2 fiber coupler. Will be provided with
Injecting backward Rayleigh scattering light returned by the sensing optical fiber into the 2 x 2 optical fiber coupler;
the balanced photodetector is used for receiving the optical information from the 2 x 2 optical fiber coupler 12 and converting the received optical information into electrical information; carrying out differential amplification detection on interference light information;
90:10 coupler for connecting 50:50 fiber coupler, 2 x 2 fiber coupler and acousto-optic modulator, the laser light is modulated according to a 90: the 10 proportion is respectively input into an acousto-optic modulator and a 2 multiplied by 2 optical fiber coupler;
a 2 x 2 fiber coupler is used to modulate the optical phase.
4. The system for monitoring external force of power cable based on distributed optical fiber sensing according to claim 1, wherein:
the acquisition card is used for acquiring information from the photoelectric detector and the balance photoelectric detector.
5. The system for monitoring external force of power cable based on distributed optical fiber sensing according to claim 1, wherein:
the sensing optical fiber is adhered to the outer surface of the power cable and fixed through an adhesive.
6. A method for monitoring external force of a power cable based on distributed optical fiber sensing by using the system of any one of claims 1 to 5, which is characterized by comprising the following steps:
step 1, when a power cable to be detected vibrates, acquiring light with vibration information through a Michelson interference system and a phase-sensitive optical time domain reflectometer system to obtain light information;
step 2, obtaining frequency change information of vibration information by analyzing optical information of the Michelson interference system;
received by analysing phase-sensitive optical time domain reflectometry systems
And obtaining amplitude information of the optical information according to the back Rayleigh scattering information, and obtaining the vibration position according to the amplitude information.
7. The external force monitoring method for the power cable based on the distributed optical fiber sensing as claimed in claim 6, wherein:
and step 2, demodulating the information from the balanced photoelectric detector, and calculating the information through band-pass filtering, quadrature demodulation and low-pass filtering to obtain amplitude information of the sampling information.
8. The external force monitoring method for the power cable based on the distributed optical fiber sensing is characterized in that:
the quadrature demodulation process is as follows:
in the formula (I), the compound is shown in the specification,
n represents the serial number of the sampling point,
n represents the number of total sample points,
s (n) represents the sampling information,
cos(Δω n n) represents I co-frequency orthogonal information,
sin(Δω n n) represents Q same-frequency orthogonal information,
Δω n ＝2πΔf/f s ，f s representing the sampling rate of the acquisition card, af representing the frequency of the modulation information,
E s (n) represents the light field intensity of the information light,
E o (n) represents the optical field intensity of the local oscillator light,
Y I the I information obtained by the operation is shown,
Y Q and representing the calculated Q information.
9. The external force monitoring method for the power cable based on the distributed optical fiber sensing as claimed in claim 8, wherein:
obtaining sum frequency terms in I and Q information through quadrature demodulation
And &>
The frequency doubling is filtered by a low-pass filter to obtain the value containing the external disturbance information>
And &>
And/or>
And &>
The relationship of (a) to (b) is as follows:
in the formula (I), the compound is shown in the specification,
Y′ I representing the I information after passing through the low-pass filter,
Y′ Q representing the Q information after passing through a low pass filter.
10. The external force monitoring method for the power cable based on the distributed optical fiber sensing is characterized in that:
y 'obtained by low-pass filtering' I And Y' Q The amplitude information of the obtained sampling information is as follows:
according to the amplitude information, the serial number of a sampling point at the vibration point at the protrusion of the amplitude is obtained, the serial number of the sampling point is multiplied by sampling interval time and light speed, the product is divided by the refractive index of the optical fiber, and the numerical value of the calculation result is divided by 2, namely the distance between the vibration point and the transmitting end.
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| US20180058983A1 (en) * | 2016-08-29 | 2018-03-01 | United States Of America As Represented By The Administrator Of Nasa | System and Method for Optical Frequency Domain Reflectometer |
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