CN116576920A - Cable vibration and strain monitoring device and method - Google Patents
Cable vibration and strain monitoring device and method Download PDFInfo
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- CN116576920A CN116576920A CN202310738719.4A CN202310738719A CN116576920A CN 116576920 A CN116576920 A CN 116576920A CN 202310738719 A CN202310738719 A CN 202310738719A CN 116576920 A CN116576920 A CN 116576920A
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- 238000012806 monitoring device Methods 0.000 title claims abstract description 18
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- 238000001514 detection method Methods 0.000 claims abstract description 102
- 239000013307 optical fiber Substances 0.000 claims abstract description 78
- 230000003287 optical effect Effects 0.000 claims abstract description 51
- 238000012545 processing Methods 0.000 claims abstract description 22
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- 238000012544 monitoring process Methods 0.000 claims description 13
- 230000010287 polarization Effects 0.000 claims description 11
- 230000000694 effects Effects 0.000 claims description 8
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- 239000006185 dispersion Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000000253 optical time-domain reflectometry Methods 0.000 description 1
- 238000007781 pre-processing Methods 0.000 description 1
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- 238000000926 separation method Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
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Abstract
The invention relates to the technical field of distributed optical fiber sensing, and discloses a cable vibration and strain monitoring device and method, wherein the device comprises the following components: the device comprises a sensing optical fiber attached to a cable to be tested, a narrow linewidth laser, a first light splitter, a detection signal processing module, a circulator, a second light splitter, a first photoelectric detector, a reference signal processing module, a coupler, a second photoelectric detector and a data acquisition module. According to the invention, the dual-mechanism distributed sensing of a single narrow linewidth laser and a single sensing optical fiber is utilized, the Brillouin scattering signal and the Rayleigh scattering signal are separated from the laser signals generated by the narrow linewidth pulse laser according to the frequency difference of the scattering signals, the Brillouin scattering signal and the Rayleigh scattering signal are detected respectively by utilizing the Brillouin optical time domain reflectometer and the phase sensitive optical time domain reflectometer, and then the vibration and strain information of the cable to be tested is obtained by analysis, so that the simultaneous measurement of the vibration and the strain of the cable to be tested is realized, and the device has a simple structure and low cost.
Description
Technical Field
The invention relates to the technical field of distributed optical fiber sensing, in particular to a cable vibration and strain monitoring device and method.
Background
The optical time domain reflectometer based on Brillouin scattering and Rayleigh scattering has extremely high measurement accuracy and sensitivity because the sensing principle is based on the change of the frequency of the Brillouin scattering light and the phase of the Rayleigh scattering light transmitted in the optical fiber, and is very suitable for detecting strain and vibration events.
Along with the development and application of the optical fiber sensing technology, multi-parameter monitoring has become a necessary development trend of an optical fiber monitoring system, and a more comprehensive judgment basis and a more effective approach are provided for the comprehensive identification of fault events. Optical time domain reflectometers based on Brillouin scattering or Rayleigh scattering can only measure single physical quantity, for example, the Brillouin optical time domain reflectometer (B-OTDR) can only detect strain along the optical fiber, and the phase sensitive optical time domain reflectometer (phi-OTDR) can only detect vibration and distribution along the optical fiber; the phase-sensitive light-sensitive time domain reflectometer detects Rayleigh scattered light, and the Brillouin optical time domain reflectometer detects Brillouin scattered light, so that a single device cannot meet the monitoring application requirements of a multi-parameter physical field; for a common single-mode fiber, the Brillouin frequency shift difference between two scattered lights is about 11GHz, and the existing detection equipment cannot utilize the single-mode fiber to realize simultaneous measurement of the two scattered lights; two laser generators and two sensing fibers are usually required for multi-parameter monitoring, and the device is complex and high in cost.
Disclosure of Invention
Therefore, the invention aims to solve the technical problem that the strain and vibration information cannot be acquired simultaneously by using a single device because the common measurement of the brillouin scattered light and the Rayleigh scattered light cannot be realized by using the single device in the prior art.
In order to solve the above technical problems, the present invention provides a cable vibration and strain monitoring device, including:
the sensing optical fiber is attached to the cable to be tested, so that the vibration state and the strain state of the sensing optical fiber are consistent with those of the cable to be tested;
the narrow linewidth laser is used for emitting a narrow linewidth pulse light source;
the input end of the first light splitter is connected with the narrow linewidth laser and is used for dividing the narrow linewidth pulse light source into two paths, namely an initial detection signal and an initial reference signal;
the detection signal processing module is connected with the output end of the first beam splitter and is used for modulating the initial detection signal into a pulse signal by using a preset modulation signal, amplifying the power of the pulse signal and outputting the modulated detection signal;
the first port of the circulator is connected with the output end of the detection signal processing module, and is used for transmitting the modulated detection signal into the sensing optical fiber from the second port of the circulator, and the backscattering sensing detection light generated by the sensing optical fiber is returned to the second port of the circulator and is output from the third port;
the input end of the second light splitter is connected with the third port of the circulator and is used for dividing the backward scattering sensing detection light output by the third port of the circulator into two paths which are a first output signal and a second output signal respectively;
the first photoelectric detector is connected with the output end of the second beam splitter and is used for detecting the first output signal to acquire the electric signal of the backward scattering sensing detection light;
the reference signal processing module is connected with the output end of the first optical splitter and used for modulating the phase, the frequency and the polarization of the initial reference signal and outputting the modulated reference signal;
the input end of the coupler is connected with the reference signal processing module and the output end of the second optical splitter, and the modulated reference signal and the second output signal are obtained and are subjected to coherent detection to obtain a difference frequency signal containing the position information of the cable to be detected;
the second photoelectric detector is connected with the output end of the coupler and used for detecting the difference frequency signal to obtain an electric signal of the difference frequency signal;
the data acquisition module is connected with the output ends of the first photoelectric detector and the second photoelectric detector, acquires the electric signals of the backward scattering sensing detection light and the electric signals of the difference frequency signal, separates out the Brillouin scattering signal and the Rayleigh scattering signal, and respectively analyzes the Brillouin scattering signal and the Rayleigh scattering signal to obtain the strain distribution, the vibration and the amplitude distribution of the optical fiber along the line.
In one embodiment of the present invention, the probe signal processing module includes:
the acousto-optic modulator is connected with the output end of the first beam splitter and modulates the initial detection signal by a preset modulation signal based on an acousto-optic effect;
the pulse generator is connected with the acousto-optic modulator and provides a preset electronic driving signal for the acousto-optic modulator;
and the input end of the optical pulse amplifier is connected with the output end of the acousto-optic modulator and is used for amplifying the pulse power of the modulated initial detection signal, reducing the nonlinear effect of the optical fiber and outputting the detection signal.
In one embodiment of the present invention, the reference signal processing module includes:
the input end of the electro-optical modulator is connected with the output end of the first optical splitter, and the phase, the frequency and the polarization of the initial reference signal are modulated by utilizing an electro-optical effect;
the microwave driver is connected with the electro-optical modulator and used for driving the electro-optical modulator to generate a preset bandwidth;
the input end of the scrambler is connected with the output end of the electro-optic modulator, so that the polarization damage of the output signal of the electro-optic modulator is eliminated;
and the input end of the single sideband filter is connected with the output end of the scrambler, filters the output signal of the scrambler and outputs a reference signal.
In one embodiment of the present invention, the data acquisition module includes:
the input end of the spectrum filter is connected with the output ends of the first photoelectric detector and the second photoelectric detector, acquires the electric signals of the backward scattering sensing detection light and the electric signals of the difference frequency signal, separates out the Brillouin scattering signal and the Rayleigh scattering signal, and respectively carries out filtering and amplifying treatment;
the Brillouin optical time domain reflectometer is connected with the output end of the frequency spectrum filter, and the separated Brillouin scattering signals are obtained and analyzed to obtain strain distribution along the optical fiber;
and the phase sensitive optical time domain reflectometer is connected with the output end of the frequency spectrum filter, acquires the separated Rayleigh scattering signals, and analyzes and obtains vibration and amplitude distribution along the optical fiber.
In one embodiment of the present invention, the sensing optical fiber is fixedly arranged inside the cable to be tested.
In one embodiment of the invention, the sensing optical fiber is fixedly arranged on the outer surface of the cable to be tested.
The embodiment of the invention also provides a cable vibration and strain monitoring method which is applied to the cable vibration and strain monitoring device and comprises the following steps:
attaching the sensing optical fiber to the cable to be tested;
dividing a light source emitted by a narrow linewidth pulse light source into an initial reference signal and an initial detection signal;
modulating the initial detection signal based on an acousto-optic effect to obtain a modulated detection signal; the modulated detection signal passes through the sensing optical fiber to generate backward scattering sensing detection light;
modulating the initial reference signal based on an electro-optical effect to generate a modulated reference signal; performing coherent detection on the modulated reference signal and the backward scattering sensing detection light to obtain a difference frequency signal containing the position information of the cable to be detected;
acquiring electric signals of the backward scattering sensing detection light and the difference frequency signal, and separating a Brillouin scattering signal and a Rayleigh scattering signal from the electric signals according to the frequency difference of the optical signals;
according to the Brillouin scattering signal, strain distribution along the optical fiber of the cable to be tested is obtained;
and according to the Rayleigh scattering signal, obtaining vibration and amplitude distribution of the cable optical fiber to be tested along the line.
In one embodiment of the present invention, the acquiring the electric signal of the back scattering sensing detection light and the difference frequency signal, and separating the brillouin scattering signal and the rayleigh scattering signal according to the optical signal frequency difference, includes:
detecting light and a difference frequency signal based on backward scattering sensing by using a photoelectric detector to obtain a corresponding electric signal;
and utilizing a frequency spectrum filter to separate the Brillouin scattering signal and the Rayleigh scattering signal from the electric signal according to the frequency difference between the Brillouin scattering signal and the Rayleigh scattering signal.
In one embodiment of the present invention, the obtaining the strain distribution along the cable optical fiber to be tested according to the brillouin scattering signal includes:
detecting the Brillouin scattering signal by using a coherent detection mode, and obtaining the center frequency of the Brillouin scattering signal by using Lorentz fitting;
and based on the center frequency, acquiring strain distribution of the cable optical fiber to be tested along the line.
In one embodiment of the present invention, the obtaining vibration and amplitude distribution along the cable optical fiber to be tested according to the rayleigh scattering signal includes:
and detecting the Rayleigh scattering signal by using a direct detection mode, and obtaining vibration and amplitude distribution of the cable optical fiber to be detected along the line by using Fourier transform analysis.
Compared with the prior art, the technical scheme of the invention has the following advantages:
according to the cable vibration and strain monitoring device, a single narrow linewidth laser and a single sensing optical fiber are utilized for dual-mechanism distributed sensing, a Brillouin scattering signal and a Rayleigh scattering signal are separated from laser signals generated by the narrow linewidth pulse laser according to the frequency difference of scattering signals, and are detected by a Brillouin optical time domain reflectometer and a phase sensitive optical time domain reflectometer respectively, so that vibration and strain information of a cable to be tested is analyzed and obtained. According to the invention, the single-path excitation light generated by a single narrow linewidth laser is utilized to pass through a single sensing optical fiber, and the Rayleigh scattering signal and the Brillouin scattering signal in the sensing optical fiber are measured simultaneously, so that the simultaneous measurement of the vibration and the strain of the cable to be tested is realized, the synchronous sensing problem of a common double system is avoided, and the device has a simple structure and low cost.
Drawings
In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings, in which
FIG. 1 is a schematic diagram of a cable vibration and strain monitoring device according to the present invention;
FIG. 2 is a schematic diagram of a data acquisition module in a cable vibration and strain monitoring device according to the present invention;
FIG. 3 is a schematic diagram of a spectrum of a sensing signal according to the present invention;
fig. 4 is a flow chart illustrating steps of a method for monitoring vibration and strain of a cable according to the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
Referring to fig. 1, a schematic structural diagram of a cable vibration and strain device of the present invention, the device specifically includes:
the sensing optical fiber is attached to the cable to be tested, so that the vibration state and the strain state of the sensing optical fiber are consistent with those of the cable to be tested;
the narrow linewidth laser is used for emitting a narrow linewidth pulse light source;
the input end of the first light splitter is connected with the narrow linewidth laser and is used for dividing the narrow linewidth pulse light source into two paths, namely an initial detection signal and an initial reference signal;
the detection signal processing module is connected with the output end of the first beam splitter and is used for modulating the initial detection signal into a pulse signal by using a preset modulation signal, amplifying the power of the pulse signal and outputting the modulated detection signal;
the first port of the circulator is connected with the output end of the detection signal processing module, and is used for transmitting the modulated detection signal into the sensing optical fiber from the second port of the circulator, and the backscattering sensing detection light generated by the sensing optical fiber is returned to the second port of the circulator and is output from the third port;
the input end of the second light splitter is connected with the third port of the circulator and is used for dividing the backward scattering sensing detection light output by the third port of the circulator into two paths which are a first output signal and a second output signal respectively;
the first photoelectric detector is connected with the output end of the second beam splitter and is used for detecting the first output signal to acquire the electric signal of the backward scattering sensing detection light;
the reference signal processing module is connected with the output end of the first optical splitter and used for modulating the phase, the frequency and the polarization of the initial reference signal and outputting the modulated reference signal;
the input end of the coupler is connected with the reference signal processing module and the output end of the second optical splitter, and the modulated reference signal and the second output signal are obtained and are subjected to coherent detection to obtain a difference frequency signal containing the position information of the cable to be detected;
the second photoelectric detector is connected with the output end of the coupler and used for detecting the difference frequency signal to obtain an electric signal of the difference frequency signal;
the data acquisition module is connected with the output ends of the first photoelectric detector and the second photoelectric detector, acquires the electric signals of the backward scattering sensing detection light and the electric signals of the difference frequency signal, separates out the Brillouin scattering signal and the Rayleigh scattering signal, and respectively analyzes the Brillouin scattering signal and the Rayleigh scattering signal to obtain the strain distribution, the vibration and the amplitude distribution of the optical fiber along the line.
Specifically, in one embodiment of the present invention, the sensing optical fiber is fixedly disposed inside the cable to be tested; the inside arrangement makes the sensing optical fiber tightly connected with the cable to be tested, and the sensing optical fiber can more accurately represent the vibration and strain states of the cable to be tested.
In another embodiment of the present invention, the sensing optical fiber is fixedly disposed on the outer surface of the cable to be tested; the sensor optical fiber and the cable to be tested are conveniently connected and disassembled, and the use is convenient.
In this embodiment, the narrow linewidth laser is the only sensing optical signal source, and is used for generating a sensing optical signal, and high-precision automatic power and automatic control technology are adopted, so that the wavelength and power output by the light source have very high stability, and meanwhile, the linewidth of the light source is narrow enough, so that the influence of the signal to noise ratio reduction caused by chromatic dispersion of the light source is greatly reduced.
Specifically, the first optical splitter splits a sensing optical signal generated by the narrow linewidth laser into two paths; one path of detection signals is modulated by a detection signal processing module to generate pulse sensing excitation light, and the pulse sensing excitation light is amplified and filtered to generate a phase sensitive optical time domain reflectometer and a Brillouin optical time domain reflectometer which are required together and used as modulated detection signals of the sensing excitation light and are input into a sensing optical fiber through a circulator; the other path of detection signals are subjected to phase, frequency and polarization modulation by a reference signal processing module to generate reference signals required by coherent detection, and are input to a signal detection and acquisition module, and are subjected to coherent detection and sensing detection signal spectrum separation with the back scattering sensing detection light generated by the modulated detection signals in a sensing optical fiber; and separating the Rayleigh scattering light detection signal of the phase sensitive optical time domain reflectometer from the Brillouin scattering light detection signal of the Brillouin optical time domain reflectometer according to the signal spectrum difference.
Specifically, the detection signal preprocessing module is configured to modulate an input optical signal into pulses sequentially through an acousto-optic modulator, and then enter an optical fiber through an optical pulse amplifier and a circulator as a detection signal, and specifically includes:
the acousto-optic modulator is connected with the output end of the first beam splitter, and utilizes an acousto-optic effect to generate an ultrasonic wave field in the modulator by utilizing a preset modulation signal to change the refractive index of the device, change the phase of light passing through the device and realize light modulation;
the pulse generator is connected with the acousto-optic modulator and provides a preset electronic driving signal for the acousto-optic modulator;
and the input end of the optical pulse amplifier is connected with the output end of the acousto-optic modulator, and the optical pulse amplifier reduces the nonlinear effect of the optical fiber and outputs a detection signal when outputting and amplifying laser pulse power.
Specifically, the circulator transmits the incident wave entering any port of the circulator into the next port according to the direction determined by the static bias magnetic field; that is, a signal input from the first port will be output from the second port, a signal input from the second port will be output from the third port, and a signal input from the third port will be output from the first port.
Specifically, the reference signal processing module eliminates polarization related damage in optical information transmission through the effect of a scrambler after the initial reference signal is subjected to frequency modulation by an electro-optical modulator, and then enters a coupler after being filtered by a single sideband filter, specifically comprising the following steps:
the input end of the electro-optical modulator is connected with the output end of the first optical splitter, and the phase, the frequency and the polarization of the initial reference signal are modulated by utilizing an electro-optical effect;
the microwave driver is connected with the electro-optical modulator and used for driving the electro-optical modulator to generate a preset bandwidth and has the performances of high gain, low jitter, ultrafast impulse response and the like;
the input end of the scrambler is connected with the output end of the electro-optic modulator, so that the polarization damage of the output signal of the electro-optic modulator is eliminated;
and the input end of the single sideband filter is connected with the output end of the scrambler, filters the output signal of the scrambler and outputs a reference signal.
Specifically, the second optical splitter splits an input detection signal into two paths, namely a Rayleigh scattering signal and a Brillouin scattering signal, which are generated by the action of the detection signal in an optical fiber; after one path of output signal is input into a coupler, mixing with a reference signal to obtain a difference frequency signal containing position information, and analyzing the difference frequency signal to obtain strain information along the optical fiber; the other output signal is directly received and collected by the first photoelectric detector, and analysis of vibration information of the optical fiber along the line is carried out.
The first photoelectric detector and the second photoelectric detector respectively filter, amplify and convert separated phase-sensitive photo-time domain reflectometer detection signals and Brillouin photo-time domain reflectometer detection signals into electric signals through a photovoltaic effect, and then input the electric signals to the data acquisition module.
Specifically, referring to fig. 2, the data acquisition module uses a dual-channel data acquisition device to sample, fuses the B-OTDR and Φ -OTDR technologies, performs lorentz fitting on brillouin scattering signal data, obtains the center frequency of the brillouin scattering signal through a fitting result, and analyzes and obtains strain distribution along the optical fiber; fourier transform analysis is carried out on the Rayleigh scattering signal, vibration and amplitude distribution along the optical fiber are obtained, and dual-parameter measurement of vibration and strain is realized, and the method specifically comprises the following steps:
the input end of the spectrum filter is connected with the output ends of the first photoelectric detector and the second photoelectric detector, acquires the electric signals of the backward scattering sensing detection light and the electric signals of the difference frequency signal, separates out the Brillouin scattering signal and the Rayleigh scattering signal, and respectively carries out filtering and amplifying treatment;
the Brillouin optical time domain reflectometer is connected with the output end of the frequency spectrum filter, and the separated Brillouin scattering signals are obtained and analyzed to obtain strain distribution along the optical fiber;
and the phase sensitive optical time domain reflectometer is connected with the output end of the frequency spectrum filter, acquires the separated Rayleigh scattering signals, and analyzes and obtains vibration and amplitude distribution along the optical fiber.
Referring to fig. 3, since a frequency difference of about 11GHz exists between brillouin scattered light and rayleigh scattered light, and a difference of frequencies of sensing signals generated after coherent detection of both scattered light is about 11GHz, the brillouin scattered signal and the rayleigh scattered signal can be easily separated by the frequency difference. In this embodiment, the phase-sensitive optical time domain reflectometer sensing detection signal and the brillouin optical time domain reflectometer sensing detection signal are separated by a spectrum filter by using the frequency difference of 11GHz existing between the brillouin scattering signal and the rayleigh scattering signal, and filtering and amplifying processing are performed.
According to the cable vibration and strain monitoring device, a single narrow linewidth laser and a single sensing optical fiber are utilized for dual-mechanism distributed sensing, a Brillouin scattering signal and a Rayleigh scattering signal are separated from laser signals generated by the narrow linewidth pulse laser according to the frequency difference of scattering signals, and are detected by a Brillouin optical time domain reflectometer and a phase sensitive optical time domain reflectometer respectively, so that vibration and strain information of a cable to be tested is analyzed and obtained. According to the invention, the single-path excitation light generated by a single narrow linewidth laser is utilized to pass through a single sensing optical fiber, and the Rayleigh scattering signal and the Brillouin scattering signal in the sensing optical fiber are measured simultaneously, so that the simultaneous measurement of the vibration and the strain of the cable to be tested is realized, the synchronous sensing problem of a common double system is avoided, and the device has a simple structure and low cost.
Based on the cable vibration and strain monitoring device, the embodiment of the invention provides a cable vibration and strain monitoring method, which is shown by referring to fig. 4, and specifically comprises the following steps:
s1: attaching the sensing optical fiber to the cable to be tested;
s2: dividing a light source emitted by a narrow linewidth pulse light source into an initial reference signal and an initial detection signal;
s3: modulating the initial detection signal based on an acousto-optic effect to obtain a modulated detection signal; the modulated detection signal passes through the sensing optical fiber to generate backward scattering sensing detection light;
s4: modulating the initial reference signal based on an electro-optical effect to generate a modulated reference signal; performing coherent detection on the modulated reference signal and the backward scattering sensing detection light to obtain a difference frequency signal containing the position information of the cable to be detected;
s5: acquiring electric signals of the backward scattering sensing detection light and the difference frequency signal, and separating a Brillouin scattering signal and a Rayleigh scattering signal from the electric signals according to the frequency difference of the optical signals;
detecting light and a difference frequency signal based on backward scattering sensing by using a photoelectric detector to obtain a corresponding electric signal; according to the frequency difference between the Brillouin scattering signal and the Rayleigh scattering signal, a spectrum filter is utilized to separate the Brillouin scattering signal and the Rayleigh scattering signal from the electric signal;
s6: detecting the Brillouin scattering signal by using a coherent detection mode, and obtaining the center frequency of the Brillouin scattering signal by using Lorentz fitting; based on the center frequency, strain distribution along the cable optical fiber to be tested is obtained;
s7: and detecting the Rayleigh scattering signal by using a direct detection mode, and obtaining vibration and amplitude distribution of the cable optical fiber to be detected along the line by using Fourier transform analysis.
Because the intensity of the Brillouin scattering signal in the optical fiber is weaker than that of the Rayleigh scattering signal by about 3 orders of magnitude, the influence of the intensity of the Brillouin scattering signal on the Rayleigh scattering signal can be ignored, and the intensity change of the Rayleigh scattering signal is detected by adopting a direct detection mode.
According to the cable vibration and strain monitoring method, based on the cable vibration and strain monitoring method device, the sensing excitation light and the sensing optical fiber are based on the same path, and the sensing signals returned by the sensing optical fiber and the reference signals are subjected to coherent detection, so that the sensing signals of the phase sensitive optical time domain reflectometer and the sensing signals of the Brillouin optical time domain reflectometer which are separated in frequency spectrum are generated, and therefore simultaneous distributed sensing of double mechanisms is realized, strain and vibration multi-state sensing detection is realized, and the synchronous detection problem of multi-system sensing is solved.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
1. A cable vibration and strain monitoring device, comprising:
the sensing optical fiber is attached to the cable to be tested, so that the vibration state and the strain state of the sensing optical fiber are consistent with those of the cable to be tested;
the narrow linewidth laser is used for emitting a narrow linewidth pulse light source;
the input end of the first light splitter is connected with the narrow linewidth laser and is used for dividing the narrow linewidth pulse light source into two paths, namely an initial detection signal and an initial reference signal;
the detection signal processing module is connected with the output end of the first beam splitter and is used for modulating the initial detection signal into a pulse signal by using a preset modulation signal, amplifying the power of the pulse signal and outputting the modulated detection signal;
the first port of the circulator is connected with the output end of the detection signal processing module, and is used for transmitting the modulated detection signal into the sensing optical fiber from the second port of the circulator, and the backscattering sensing detection light generated by the sensing optical fiber is returned to the second port of the circulator and is output from the third port;
the input end of the second light splitter is connected with the third port of the circulator and is used for dividing the backward scattering sensing detection light output by the third port of the circulator into two paths which are a first output signal and a second output signal respectively;
the first photoelectric detector is connected with the output end of the second beam splitter and is used for detecting the first output signal to acquire the electric signal of the backward scattering sensing detection light;
the reference signal processing module is connected with the output end of the first optical splitter and used for modulating the phase, the frequency and the polarization of the initial reference signal and outputting the modulated reference signal;
the input end of the coupler is connected with the reference signal processing module and the output end of the second optical splitter, and the modulated reference signal and the second output signal are obtained and are subjected to coherent detection to obtain a difference frequency signal containing the position information of the cable to be detected;
the second photoelectric detector is connected with the output end of the coupler and used for detecting the difference frequency signal to obtain an electric signal of the difference frequency signal;
the data acquisition module is connected with the output ends of the first photoelectric detector and the second photoelectric detector, acquires the electric signals of the backward scattering sensing detection light and the electric signals of the difference frequency signal, separates out the Brillouin scattering signal and the Rayleigh scattering signal, and respectively analyzes the Brillouin scattering signal and the Rayleigh scattering signal to obtain the strain distribution, the vibration and the amplitude distribution of the optical fiber along the line.
2. The cable vibration and strain monitoring device of claim 1, wherein the probe signal processing module comprises:
the acousto-optic modulator is connected with the output end of the first beam splitter and modulates the initial detection signal by a preset modulation signal based on an acousto-optic effect;
the pulse generator is connected with the acousto-optic modulator and provides a preset electronic driving signal for the acousto-optic modulator;
and the input end of the optical pulse amplifier is connected with the output end of the acousto-optic modulator and is used for amplifying the pulse power of the modulated initial detection signal, reducing the nonlinear effect of the optical fiber and outputting the detection signal.
3. The cable vibration and strain monitoring device of claim 1, wherein the reference signal processing module comprises:
the input end of the electro-optical modulator is connected with the output end of the first optical splitter, and the phase, the frequency and the polarization of the initial reference signal are modulated by utilizing an electro-optical effect;
the microwave driver is connected with the electro-optical modulator and used for driving the electro-optical modulator to generate a preset bandwidth;
the input end of the scrambler is connected with the output end of the electro-optic modulator, so that the polarization damage of the output signal of the electro-optic modulator is eliminated;
and the input end of the single sideband filter is connected with the output end of the scrambler, filters the output signal of the scrambler and outputs a reference signal.
4. The cable vibration and strain monitoring device of claim 1, wherein the data acquisition module comprises:
the input end of the spectrum filter is connected with the output ends of the first photoelectric detector and the second photoelectric detector, acquires the electric signals of the backward scattering sensing detection light and the electric signals of the difference frequency signal, separates out the Brillouin scattering signal and the Rayleigh scattering signal, and respectively carries out filtering and amplifying treatment;
the Brillouin optical time domain reflectometer is connected with the output end of the frequency spectrum filter, and the separated Brillouin scattering signals are obtained and analyzed to obtain strain distribution along the optical fiber;
and the phase sensitive optical time domain reflectometer is connected with the output end of the frequency spectrum filter, acquires the separated Rayleigh scattering signals, and analyzes and obtains vibration and amplitude distribution along the optical fiber.
5. The cable vibration and strain monitoring device of claim 1, wherein the sensing optical fiber is fixedly arranged inside the cable to be tested.
6. The cable vibration and strain monitoring device of claim 1, wherein the sensing optical fiber is fixedly arranged on the outer surface of the cable to be tested.
7. A cable vibration and strain monitoring method, applied to the cable vibration and strain monitoring device according to any one of claims 1 to 6, comprising:
attaching the sensing optical fiber to the cable to be tested;
dividing a light source emitted by a narrow linewidth pulse light source into an initial reference signal and an initial detection signal;
modulating the initial detection signal based on an acousto-optic effect to obtain a modulated detection signal; the modulated detection signal passes through the sensing optical fiber to generate backward scattering sensing detection light;
modulating the initial reference signal based on an electro-optical effect to generate a modulated reference signal; performing coherent detection on the modulated reference signal and the backward scattering sensing detection light to obtain a difference frequency signal containing the position information of the cable to be detected;
acquiring electric signals of the backward scattering sensing detection light and the difference frequency signal, and separating a Brillouin scattering signal and a Rayleigh scattering signal from the electric signals according to the frequency difference of the optical signals;
according to the Brillouin scattering signal, strain distribution along the optical fiber of the cable to be tested is obtained;
and according to the Rayleigh scattering signal, obtaining vibration and amplitude distribution of the cable optical fiber to be tested along the line.
8. The method for monitoring vibration and strain of a cable according to claim 7, wherein obtaining the electric signals of the back-scattering sensing detection light and the difference frequency signal, and separating the brillouin scattering signal and the rayleigh scattering signal from the electric signals according to the optical signal frequency difference, comprises:
detecting light and a difference frequency signal based on backward scattering sensing by using a photoelectric detector to obtain a corresponding electric signal;
and utilizing a frequency spectrum filter to separate the Brillouin scattering signal and the Rayleigh scattering signal from the electric signal according to the frequency difference between the Brillouin scattering signal and the Rayleigh scattering signal.
9. The method for monitoring vibration and strain of a cable according to claim 7, wherein obtaining strain distribution along a cable optical fiber to be tested according to brillouin scattering signals comprises:
detecting the Brillouin scattering signal by using a coherent detection mode, and obtaining the center frequency of the Brillouin scattering signal by using Lorentz fitting;
and based on the center frequency, acquiring strain distribution of the cable optical fiber to be tested along the line.
10. The method for monitoring vibration and strain of cable according to claim 7, wherein the step of obtaining vibration and amplitude distribution along the cable fiber to be tested according to the rayleigh scattering signal comprises:
and detecting the Rayleigh scattering signal by using a direct detection mode, and obtaining vibration and amplitude distribution of the cable optical fiber to be detected along the line by using Fourier transform analysis.
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