CN110940410A - Vehicle vibration monitoring device and method based on two-mode optical fiber - Google Patents

Vehicle vibration monitoring device and method based on two-mode optical fiber Download PDF

Info

Publication number
CN110940410A
CN110940410A CN201911054228.8A CN201911054228A CN110940410A CN 110940410 A CN110940410 A CN 110940410A CN 201911054228 A CN201911054228 A CN 201911054228A CN 110940410 A CN110940410 A CN 110940410A
Authority
CN
China
Prior art keywords
mode
mold
vibration
time domain
optical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN201911054228.8A
Other languages
Chinese (zh)
Inventor
秦祖军
刘承达
程海博
熊显名
张文涛
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Guilin University of Electronic Technology
Original Assignee
Guilin University of Electronic Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Guilin University of Electronic Technology filed Critical Guilin University of Electronic Technology
Priority to CN201911054228.8A priority Critical patent/CN110940410A/en
Publication of CN110940410A publication Critical patent/CN110940410A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

The invention discloses a vehicle vibration monitoring device and method based on two-mode optical fiber.A laser emits continuous laser which is divided into two parts by an optical coupler, one part is modulated into detection pulses by a pulse generator and sent into two-mode sensing optical fiber, and the other part is used as local oscillation light; after backward Rayleigh scattered light returned by the two-mode sensing optical fiber is combined with a local oscillator, data processing is carried out by a digital signal processing unit, namely, a variation coefficient method is firstly used for processing original data of two modes to obtain a vibration peak with higher signal-to-noise ratio, then time domain data of the position of the vibration peak is extracted, and the time domain data is input into a trained neural network for identification after EMD characteristic extraction. Compared with the prior art, the invention provides the speed and the accuracy rate of vehicle vibration monitoring and identification.

Description

Vehicle vibration monitoring device and method based on two-mode optical fiber
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a vehicle vibration monitoring device and method based on two-mode optical fibers.
Background
With the advance of urbanization process and the rapid increase of the number of motor vehicles in China, the traffic volume of highways is continuously increased, and the difficulty of monitoring high-speed vehicles is increasingly high. At present, relatively mature road vehicle monitoring methods mainly comprise vertical monitoring schemes such as annular coils, digital videos and ultrasonic waves, and although the single-point monitoring precision of the technologies is high, the problems of dead angle monitoring, complex networking and the like exist in the vertical monitoring schemes.
The optical fiber sensing technology is a new sensing technology which has emerged along with the optical fiber technology and the optical communication technology in recent decades. The optical fiber sensing sensor uses light waves as sensing signals and optical fibers as signal transmission media to detect external signals, and is different from a traditional electrical sensor in the aspects of sensing modes, signal detection, signal processing and the like. The optical fiber sensor based on the phase-sensitive optical time domain reflectometer is widely applied to the fields of boundary security, petroleum pipeline safety monitoring and the like due to the long-distance, full-distributed, high-sensitivity and other sensing characteristics. The sensing characteristics of the optical fiber are utilized to carry out real-time and whole-course monitoring on the vehicle vibration on the road, and the method has important application value for constructing a road traffic monitoring network with the multi-sensor integration.
The traditional phase-sensitive optical time domain reflectometer uses a single-mode optical fiber as a sensing medium and realizes vibration position positioning by an amplitude difference method. Specifically, the system firstly collects the amplitude data of a backward Rayleigh scattering signal; when the data volume reaches the number set by a user, dividing the collected data into lines according to the length of the optical fiber, wherein the data in each line is a Rayleigh scattering signal generated when the optical pulse completes one-time transmission in the sensing optical fiber; and carrying out difference and absolute value calculation on each row of data and the data of every other k rows, finally accumulating to obtain a frame of data, and determining the position of a vibration peak in the sensing link according to the frame of data.
Although the traditional single-mode optical fiber phase-sensitive optical time domain reflectometer shows better sensing performance in practical application, the following defects still exist: (1) the nonlinear threshold level and the reflected light capture rate of the single-mode fiber are low, so that the injectable pulse light power is limited, and the Rayleigh scattered light signal received by the injection end of the fiber is weak, so that the acquisition and subsequent processing of the scattered signal are not facilitated; (2) the single-mode optical fiber can only transmit optical signals of one mode, is greatly influenced by the non-uniform medium and the non-matched polarization state of the optical fiber, and cannot compensate the sudden change of a vibration peak caused by noise, so that the signal-to-noise ratio is reduced; (3) the difference accumulation algorithm needs to select the number of difference intervals (namely k value) according to the vibration frequency, the difference k value needs to be changed when the vibration frequency is changed, and the selection method of the k value has no clear value selection basis; the algorithm has high requirements on the waveform, and the effect of detecting the irregular vibration source of vehicle vibration is poor.
Disclosure of Invention
The invention provides a vehicle vibration monitoring device and method based on two-mode optical fibers, aiming at the problems of the existing single-mode optical fiber phase-sensitive optical time domain reflectometer.
In order to solve the problems, the invention is realized by the following technical scheme:
a vehicle vibration monitoring device based on two-mode optical fibers comprises a laser, a pulse light generator, a circulator, a mode division multiplexer, two-mode sensing optical fibers, a collection card, a digital signal processing unit, 2 polarization controllers, 2 photoelectric conversion and electric signal processing modules and 4 optical couplers; the output end of the laser is connected with the input end of a first optical coupler, one output end of the first optical coupler is connected with the input end of a pulse light generator, and the other output end of the first optical coupler is connected with the input end of a second optical coupler; the output end of the pulse light generator is connected with the first port of the optical circulator, and the second port of the optical circulator is connected with the LP of the mode division multiplexer01The multiplexing port of the mode division multiplexer is connected with two mode sensing optical fibers; two-mode sensing optical fibers are laid along the road ground; the third port of the optical circulator is connected with one input end of a third optical coupler and the LP of the mode division multiplexer11The mould port is connected with one input end of the fourth optical coupler; one output end of the second optical coupler is connected with the other input end of the third optical coupler through the first polarization controller; the other output end of the second optical coupler is connected with the other input end of the fourth optical coupler through a second polarization controller; two output ends of the third optical coupler are simultaneously connected with two input ends of the first photoelectric conversion and electric signal processing module, and two output ends of the first photoelectric conversion and electric signal processing module are simultaneously connected with the acquisition card;two output ends of the fourth optical coupler are simultaneously connected with two input ends of the second photoelectric conversion and electric signal processing module, and two output ends of the second photoelectric conversion and electric signal processing module are simultaneously connected with the acquisition card; the output end of the acquisition card is connected with the input end of the digital signal processing unit.
In the above scheme, the splitting ratio of the first optical coupler is 80:20, wherein 80% of the output end is connected with the input end of the pulse light generator, and 20% of the output end is connected with the input end of the second optical coupler.
In the above scheme, the splitting ratio of the second optical coupler, the third optical coupler and the fourth optical coupler is 50: 50.
In the above scheme, the pulse light generator is an optical fiber coupled acousto-optic modulator, and a pulse period of pulse light generated by the pulse light generator is longer than a round-trip time for light to propagate in the two-mode sensing optical fiber.
In the above scheme, two output ends of the first photoelectric conversion and electric signal processing module output IQ two-path radio frequency signals, both of which carry LP01Model backward rayleigh scattered light information; two output ends of the second photoelectric conversion and electric signal processing module output IQ two-path radio frequency signals which both carry LP11And (4) mode backward Rayleigh scattering light information.
A vehicle vibration monitoring method based on two-mode optical fibers comprises the following steps:
step 1, LP01The continuous laser of the die is divided into two paths: one path is modulated to generate LP01The mode light pulse is injected into the two-mode sensing optical fiber; the other path generates local oscillation light after polarization regulation;
step 2, enabling a sample vehicle to drive through a certain sampling point of two-mode sensing optical fibers paved on the road ground, namely a sample sampling point, generating vibration on the ground to enable the two-mode sensing optical fibers to be disturbed, and generating an LP carrying vibration information01Mold and LP11Rayleigh scattered light behind the modes;
step 3, carrying the LP of the vibration information01And LP11The Rayleigh scattering light after the mode returns to the injection ends of the two mode sensing optical fibers and is respectively combined with the local oscillator light to obtain LP01Mold and LP11The mode vibration beam combination optical signal;
step 4, for LP obtained in step 301Mold and LP11After the optical signal of the mode vibration beam combination is processed by optical signal processing, photoelectric conversion and electric signal processing, the LP of the two-mode sensing optical fiber at the sample sampling point is obtained by sampling01Mold and LP11A vibrational time domain signal of a mode;
step 5, respectively carrying out LP on the sample sampling points obtained in the step 401Mold and LP11The variance and the range of the vibration time domain signal of the mode are calculated to obtain the LP at the sample sampling point01Mold and LP11Variance and range of the modulus time domain signal;
step 6, respectively carrying out LP on the sample sampling points obtained in the step 4 by using an empirical mode decomposition method01Mold and LP11Decomposing the vibration time domain signal of the mode to obtain LP01Mold and LP11A component of a mode vibration signal eigenmode; and respectively to LP01Mold and LP11Integral processing is carried out on the eigenmode component of the mode vibration signal to obtain LP at the sampling point of the sample01Mold and LP11A magnitude of an energy of an eigenmode component of the mode vibration signal;
7, carrying out LP on the sample sampling point obtained in the step 501Mold and LP11The variance and range of the modulus time domain signal and the LP at the sample sampling point obtained in step 601Mold and LP11The energy value of the eigenmode component of the mode vibration signal is used as sample data and is correspondingly input into a neural network for training to obtain a trained neural network;
step 8, collecting LP returned from the two-mode sensing optical fiber in real time01Mold and LP11Rayleigh scattered light in the backward direction of the model is combined with local oscillator light respectively to obtain LP01Mold and LP11A beam combination optical signal is subjected to mode combination;
step 9, for LP obtained in step 801Mold and LP11After the optical signal of the mode beam combination is processed by optical signal processing, photoelectric conversion and electric signal processing, LP of the two-mode sensing optical fiber at each sampling point is obtained by sampling01Mold and LP11A modulo time domain signal;
step 10, for the LP at each sampling point obtained in step 901Mold and LP11The time domain signals of the modes are respectively applied to the LPs by a coefficient of variation method01Mold and LP11Performing coefficient variation processing on the time domain signal of the mode, and processing the coefficient variation to obtain LP01Modulus signal and LP11Multiplying the mode signals to obtain a disturbance curve of the two-mode sensing optical fiber along the line;
step 11, if the disturbance curve obtained in the step 10 has a vibration peak, the LP at each sampling point obtained in the step 9 is used01Mold and LP11Vibration peak LP in the time domain signal of the mode01Mold and LP11The time domain signal of the modulus is sent to steps 12 and 13 simultaneously; if the disturbance curve obtained in the step 10 does not have a vibration peak, ignoring the data of the frame and returning to the step 8;
step 12, vibrating peak LP01Mold and LP11Calculating the variance and range of the time domain signal of the mode to obtain the vibration peak P01Mold and LP11Variance and range of the modulus time domain signal;
step 13, respectively carrying out LP on vibration peaks by using an empirical mode decomposition method01Mold and LP11Decomposing the time domain signal of the module to obtain LP01Mold and LP11A component of a mode vibration signal eigenmode; and respectively to LP01Mold and LP11Integrating the eigenmode component of the time domain signal to obtain the vibration peak LP01Mold and LP11A module time domain signal eigenmode component energy value;
step 14, the vibration peak LP obtained in step 1201Mold and LP11The variance and range of the modulus time domain signal and the vibration peak LP obtained in step 1301Mold and LP11And the energy value of the eigenmode component of the mode time domain signal is used as measured data and is correspondingly sent to a neural network for processing, and the neural network judges and identifies whether the vibration at the position is the vehicle vibration.
Compared with the prior art, the invention has the following characteristics:
1. the two-mode fiber has a higher threshold level than a single-mode fiberThe reflected light capture rate can inject higher-power detection pulses into the two-mode optical fiber to generate stronger backward Rayleigh scattering signals, thereby being beneficial to the acquisition and processing of signals in the later period. At the same time, two modes (LP) are allowed in a two-mode fiber01Mold and LP11Mode), two modes of signals can be subsequently separated for noise compensation of an upper computer, misjudgment of the signals of a certain mode caused by noise is weakened, and the signal-to-noise ratio of the system and the accuracy of vibration judgment are improved.
2. And identifying the vibration signal by adopting a processing mode of combining EMD and a neural network. Compared with other signal analysis means, the EMD does not need to set a basis function for analyzing and extracting the signal characteristics, performs signal decomposition only according to the self time scale characteristics, has self-adaptability, and is particularly suitable for nonlinear signals in the system. After the features are extracted by EMD, the features of the signals are used as the feature values to be input into the neural network for training, and compared with the method of directly training the time domain signals of the vibration points as the feature values, the method reduces the number of the feature values and a large amount of invalid data, and improves the speed and accuracy of training the neural network.
3. Compared with the differential accumulation algorithm for processing time domain signals, the coefficient of variation method does not need to set a differential k value, and has no higher requirement on a measured waveform.
Drawings
FIG. 1 is a schematic structural diagram of a vehicle vibration monitoring device based on two-mode optical fibers according to the present invention;
FIG. 2 is a flow chart of a training phase of a two-mode fiber-based vehicle vibration monitoring method of the present invention;
FIG. 3 is a diagram illustrating the definition of the types of related data in the data processing method according to the present invention;
FIG. 4 is a schematic diagram of the decomposition of time domain data of vibration points by empirical mode decomposition used in the present invention;
fig. 5 is a flowchart of the actual measurement stage of vehicle vibration monitoring based on two-mode optical fiber according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to specific examples.
A vehicle vibration monitoring device based on two-mode optical fibers is shown in figure 1 and comprises a high-power narrow-linewidth laser, a pulse light generator, a circulator, a mode division multiplexer, two-mode sensing optical fibers, a collection card, a digital signal processing unit, 2 polarization controllers, 2 photoelectric conversion and electric signal processing modules and 4 optical couplers. The output end of the high-power narrow linewidth laser is connected with the input end of a first optical coupler, one output end of the first optical coupler is connected with the input end of a pulse light generator, and the other output end of the first optical coupler is connected with the input end of a second optical coupler. The output end of the pulse light generator is connected with the first port of the optical circulator, and the second port of the optical circulator is connected with the LP of the mode division multiplexer01And the mode port and the multiplexing port of the mode division multiplexer are connected with two mode sensing optical fibers. The third port of the optical circulator is connected with one input end of a third optical coupler and the LP of the mode division multiplexer11The die port is connected to an input of a fourth optical coupler. One output end of the second optical coupler is connected with the other input end of the third optical coupler through the first polarization controller. The other output end of the second optical coupler is connected with the other input end of the fourth optical coupler through the second polarization controller. Two output ends of the third optical coupler are simultaneously connected with two input ends of the first photoelectric conversion and electric signal processing module, and two output ends of the first photoelectric conversion and electric signal processing module are simultaneously connected with the acquisition card. Two output ends of the fourth optical coupler are simultaneously connected with two input ends of the second photoelectric conversion and electric signal processing module, and two output ends of the second photoelectric conversion and electric signal processing module are simultaneously connected with the acquisition card. The output end of the acquisition card is connected with the input end of the digital signal processing unit.
High power narrow linewidth laser generation of LP01Continuous laser of the mode, wherein the line width of the laser is not more than 5 kHz. In this embodiment, the high-power narrow linewidth laser emits continuous laser with a wavelength of 1550nm, a linewidth of the laser is 3kHz, an output power is 25mW, and an operating mode is LP01And (5) molding.
The first optical coupler divides the output laser of the high-power narrow linewidth laser into two paths, and the splitting ratio of the two paths is 80: 20. And 80% of the output end of the first optical coupler is connected with the input end of the pulse light generator and is used for generating a detection light pulse. The 20% output of the first optical coupler is connected to the input of the second optical coupler as LP01Mold and LP11And (3) coherent detection of the local oscillator light required by the two paths of backward Rayleigh scattering signals.
The pulse light generator is an optical fiber coupling acousto-optic modulator, and the modulation bandwidth is 200 MHz. The pulse light generator modulates continuous laser input by the first optical coupler into pulse light, the pulse width of the pulse light is 100ns, the rising time and the falling time are both 2.5ns, the period of the repeated pulse is determined by the length of the optical fiber, and particularly the period of the repeated pulse is required to be larger than the time of the light transmitting in the optical fiber back and forth. In this example, the length of the optical fiber is 2km, and the time for light to travel back and forth in the optical fiber is about 19.34us, so that the pulse period is set to 20 us. The output frequency of the pulse light is shifted down by 200MHz while the pulse light is modulated.
The circulator converts LP generated by the pulse light generator01The mode light pulse passes through a mode division multiplexer LP01The mode ports inject two-mode sensing fibers. LP generated by two-mode sensing fiber01The model backward Rayleigh scattering signal passes through the LP of the model division multiplexer01The mode port returns to the second port of the circulator and is output to one input end of the third optical coupler through the third port of the circulator. LP generated by two-mode sensing fiber11Model backward Rayleigh scattering signal LP through model division multiplexer11The mode port is coupled to an input of a fourth optical coupler.
Mode division multiplexer supporting LP in C wave band01Mold and LP11And multiplexing and demultiplexing the mode light waves. Mode division multiplexer and LP01The mode laser is injected into the two-mode sensing fiber. Mode division multiplexer for LP returned from two-mode sensing optical fiber01Mold and LP11After the model backward Rayleigh scattering signal is demultiplexed, one path of LP01Model backward Rayleigh scattering signal via LP01The mode port is sent to a third optical coupler through a circulator, and one path of LP11Model backward Rayleigh scattering signal via LP11Die portTo a fourth optocoupler.
The two-mode sensing optical fiber is laid along a road and used for sensing vehicles. In the two-mode sensing fiber in this embodiment, the normalized frequency V in the C band satisfies: 2.4048<V<3.8327, support LP01Mold and LP11And the mode light wave transmission is 2km in length. LP01Rayleigh scattering is continuously generated when mode light waves are transmitted in the forward direction of the optical fiber, and the Rayleigh scattering light exists in LP01And LP11In two modes, LP01Mold and LP11The rayleigh scattered light behind the mode propagates back to the fiber injection end along the sensing fiber.
The second optical coupler divides the laser output by the first optical coupler into a first local oscillator light and a second local oscillator light, the splitting ratio of the first local oscillator light to the second local oscillator light is 50:50, and two output ends of the second local oscillator light are respectively connected with the input ends of the first polarization controller and the second polarization controller.
The first polarization controller PC1 performs polarization control on the first local oscillation light output by the second optical coupler.
The second polarization controller PC2 performs polarization control on the second local oscillation light output by the second optical coupler.
The third optical coupler firstly outputs the first local oscillator light output by the first polarization controller and the LP output by the third port of the circulator01And combining the mode backward Rayleigh scattered light, wherein the equation of the light wave electric field after combination is formula (1). And then splitting the beam combination light in a ratio of 1:1, wherein the light wave electric field equation after splitting is an equation (2) and an equation (3), and the two paths of split optical signals have a phase difference of pi/2.
E＝Esexp(iωst+φS)+ELexp(iωLt+φL) (1)
Figure RE-GDA0002360926590000061
Figure RE-GDA0002360926590000062
Wherein E issTo signal light amplitude, ELIs a local oscillator lightAmplitude of vibration.
The fourth optical coupler firstly outputs the second local oscillator light output by the second polarization controller and the mode division multiplexer LP11LP of modular port output11Combining the mode backward Rayleigh scattered light, then splitting the combined light by 1:1, and splitting the split two paths of optical signals with the phase difference of pi/2. The optical wave electric field equation after the fourth optical coupler is combined and split is as described in the third optical coupler.
The first photoelectric conversion and electric signal processing module firstly carries out photoelectric conversion and beat frequency detection on two paths of optical signals with the phase difference of pi/2 output by the third optical coupler so as to reduce common mode noise of the system and improve signal to noise ratio, detection sensitivity and dynamic range. Amplifying, filtering and IQ demodulating the electrical signal, sending the demodulated IQ two-path radio frequency signal to an acquisition card, wherein the radio frequency signal carries the LP in the two-mode optical fiber01And (4) mode backward Rayleigh scattering light information.
The second photoelectric conversion and electric signal processing module firstly carries out photoelectric conversion and beat frequency detection on two paths of optical signals with the phase difference of pi/2 output by the fourth optical coupler so as to reduce the common mode noise of the system and improve the signal-to-noise ratio, the detection sensitivity and the dynamic range of the signals. Amplifying, filtering and IQ demodulating the electrical signal, sending the demodulated IQ two-path radio frequency signal to an acquisition card, wherein the radio frequency signal carries the LP in the two-mode optical fiber11And (4) mode backward Rayleigh scattering light information.
The acquisition card simultaneously carries out A/D conversion on IQ two-path radio-frequency signals sent by the first photoelectric conversion and electric signal processing module and IQ two-path radio-frequency signals sent by the second photoelectric conversion and electric signal processing module, and sends the IQ two-path radio-frequency signals into the digital signal processing module. In addition, the acquisition card sets different sampling rates aiming at the backward Rayleigh scattering signals of the two modes so as to compensate the difference of the propagation speeds of the light of the two modes in the optical fiber. The acquisition card can continuously acquire a part of data and then intensively transmit the data to the digital signal processing module. In this example, the acquisition card provides a maximum real-time sampling rate of 10GS/s on each of four channels, a recording length of 500M points.
The digital signal processing module processes the digital signals sent by the acquisition card, and comprises the steps of extracting time domain signals of sampling points, analyzing characteristics, training a neural network in a training stage, judging vibration positions in an actual measurement stage, analyzing the characteristics of the time domain signals of the vibration positions, processing and identifying the vibration signals by the neural network and the like.
The working process of the vehicle vibration monitoring device with the two-mode optical fiber is as follows:
high power narrow linewidth laser generation of LP01The continuous laser of the mode is input into a first optical coupler, and the first optical coupler divides the laser output by the high-power narrow linewidth laser into two parts: in the first branch, the pulse light generator modulates the laser (80%) output by the first optical coupler into a detection pulse, and the detection pulse sequentially passes through the first port of the circulator, the second port of the circulator and the mode division multiplexer LP01The mode ports inject two-mode sensing fibers. LP in two-mode sensing fiber01The mode backward Rayleigh scattering light passes through a mode division multiplexer LP in sequence01The mode port, the circulator second port and the circulator third port are input into one input end of a third optical coupler. LP in two-mode sensing fiber11Mode backward Rayleigh scattered light passes through a mode division multiplexer LP11The mode port is input to one input of a fourth optical coupler. In the second branch, the second optical coupler divides another part of the laser light (20%) divided by the first optical coupler into two local oscillation light paths, which are marked as first local oscillation light and second local oscillation light. The first local oscillator light and the second local oscillator light are respectively input into the third optical coupler and the fourth optical coupler after being subjected to polarization regulation and control by the first polarization controller and the second polarization controller. The third optical coupler enables the first local oscillator light and the LP returned by the third port of the circulator01The light is combined by the mode back Rayleigh scattering light and input into the first photoelectric conversion and electric signal processing module. The fourth optical coupler enables the second local oscillator light and the mode division multiplexer LP11LP with return from mould port11The light is combined after the mode back Rayleigh scattering and input into a second photoelectric conversion and electric signal processing module. The first photoelectric conversion and electric signal processing module and the second photoelectric conversion and electric signal processing module send the processed optical signals to the acquisition card for acquisition and then input the optical signals to the digital signal processing unit for signal processing.
The vehicle vibration monitoring method based on the two-mode optical fiber comprises the following specific steps of:
step 1, LP01The continuous laser of the die is divided into two paths: one path is modulated to generate LP01And (4) performing mode light pulse and injecting the mode light pulse into the two-mode sensing optical fiber. And the other path generates local oscillation light after polarization regulation.
(1) Training phase (see fig. 2):
step 2, embedding the two-mode optical fiber at one side of the road, enabling a sample vehicle to pass through a certain sampling point of the two-mode sensing optical fiber paved on the ground of the road, generating vibration on the ground to enable the two-mode sensing optical fiber to be disturbed, and changing the refractive index of the two-mode optical fiber at the point, so as to change backward Rayleigh scattered light, LP (linear polarization) light, generated at the point in the optical fiber01Mold and LP11The mode back Rayleigh scattering light carries vibration information.
Step 3, carrying the LP of the vibration information01And LP11The Rayleigh scattered light after the mode is transmitted back to the injection end of the two-mode sensing optical fiber and is respectively combined with the local oscillator light to obtain LP01Mold and LP11The beam light signals are combined in a mode.
Step 4, LP01Mold and LP11After the optical signal processing, the photoelectric conversion and the electric signal processing are carried out on the mode beam combination optical signal, the LP at the sampling point of the two-mode sensing optical fiber where the sample vehicle is located is obtained through sampling01Mold and LP11The vibrational time domain signal of the mode.
Designing different sampling rates aiming at backward Rayleigh scattering signals of different light wave modes, and compensating LP01Mold and LP11The difference in the velocity of the mode in the sensing fiber. LP in sensing fiber01Mold and LP11The modes have different effective indices of refraction that are not uniform in their propagation velocity in the sensing fiber. If the two signals are not compensated, the two signals are directly integrated after data processing, the signal-to-noise ratio of the signals is reduced, and the phenomenon that one vibration source corresponds to two vibration peaks occurs. The invention provides a compensation mode of adopting different sampling rates in different light wave modes aiming at the problem. Specifically, the sampling frequency of the acquisition card is set to ensure that the light waves with the sampling period corresponding to the mode are transmitted in the sensing optical fiberThe time is l meters, that is, each data acquired by the acquisition card corresponds to the rayleigh scattering signal of one point on the sensing optical fiber, and each point is separated by l meters. Sampling frequency
Figure RE-GDA0002360926590000074
The calculation formula of (2) is as follows:
Figure RE-GDA0002360926590000071
Figure RE-GDA0002360926590000072
where i is a propagation mode of light in the optical fiber (i ═ 01 denotes LP01And (5) molding. i-11 denotes LP11Mode), c is the propagation speed of light in vacuum,
Figure RE-GDA0002360926590000073
is the effective refractive index of the corresponding mode light wave in the sensing fiber. The acquisition card aiming at LP can be determined by the formulas (4) and (5)01Mold and LP11The sampling frequency of the modulo setting.
In this embodiment, the sampling period is set to correspond to the time that the mode light wave propagates in the sensing fiber for 1 meter, specifically, LP01The effective index of the mode in the sensing fiber is 1.4498, LP11The effective refractive index of the mode is 1.4468, the propagation time of two modes in the optical fiber is 4.8360 multiplied by 10m-9s and 4.8260X 10-9s, the sampling rates of the two modes should be set to 1.0339 × 10 respectively8Hz and 1.0361X 108Hz。
For a better description of the data, the data is now defined as follows: as shown in fig. 3, the acquisition card is configured to acquire a rayleigh scattering signal in an optical wave mode returned by a single probe pulse as a piece of backward rayleigh scattering data. Two modes (LP) for returning single detection pulse are collected01Mold and LP11Mode) is a frame of backward rayleigh scattered data. Setting n pieces of backward Rayleigh scattering data to be specific samplingThe time domain data corresponding to the sampling point is time domain data of a sampling point. From the above, the number of sampling points in one piece of backward rayleigh scattering data is determined by the length of the optical fiber, in this embodiment, the length of the sensing optical fiber is 2km, 2000 sampling points are in one piece of backward rayleigh scattering data, and 4000 sampling points are in one piece of frame data. The number of time domain data of one sampling point is determined by the value of n.
The acquisition card continuously acquires n frames of backward Rayleigh scattering data, ensures that two adjacent backward Rayleigh scattering data in each light wave mode are amplitude information of backward Rayleigh scattering signals generated by adjacent detection pulses, and can determine the sampling period of a sampling point time domain signal (the sampling period is the repetition period of the detection pulses). The acquisition process is stored by the acquisition card, and after the acquisition is finished, the acquisition data is transmitted to the digital signal processing unit in a centralized manner to be processed.
In this embodiment, the design rule of the n value is: the vibration frequency of the vehicle to the ground is in the range of 0-100Hz, with the main energy concentrated in the low frequency range around 50 Hz. Half a period is sufficient to characterize a signal, and the time to collect n pieces of data is half the period of the vibration signal (not limited thereto). The sensing medium of this embodiment is a 2km optical fiber, the pulse repetition period is 20 mus, and the value of n is 10ms/20 mus equals 500 for vibration signals around 50 Hz. That is, 500 pieces of backward rayleigh scattering data are collected in each light wave mode in a centralized manner and transmitted into the digital signal processing unit, and the number of one piece of time domain data of a certain sampling point in each light wave mode is 500.
In this embodiment, since the vehicle vibration occurs at 1km of the optical fiber, the time domain signal of the data at 1km of the optical fiber is extracted, the sampling frequency of each mode is the distance corresponding to 1m of the propagation of the light wave mode in the optical fiber, so the data of the time domain signal at 1km is the set of 1000 th data of each backward rayleigh scattering signal, and the number of the time domain data of each mode is 500.
Step 5, respectively carrying out comparison on the LP obtained in the step 401Mold and LP11Carrying out variance and range calculation on the vibration time domain signal of the mode to obtain LP01Mold and LP11The variance and range of the modulus time domain signal.
The range calculation formula is as follows:
R＝max(xi)-min(xi) (6)
the variance calculation formula is as follows:
Figure RE-GDA0002360926590000081
wherein x isiA piece of time-domain data is represented,
Figure RE-GDA0002360926590000082
is the average value of a time domain number, and n is the data volume of a piece of data.
Step 6, using Empirical Mode Decomposition (EMD) method to respectively process the LPs obtained in the step 401Mold and LP11Decomposing the vibration point time domain signal of the mode to obtain LP01Mold and LP11The eigenmode component of the mode vibration signal. And respectively to LP01Mold and LP11Integrating the eigenmode component of the mode vibration signal to obtain LP01Mold and LP11And (4) the energy value of the eigenmode component of the mode vibration signal.
And taking time domain data at the vibration point of the vehicle, performing noise reduction and feature extraction on the time domain data by using an empirical mode decomposition method, and inputting the time domain data, the variance and the range of the time domain signal as feature values into a subsequent neural network for training. After empirical mode decomposition, each piece of time domain data can be represented as a plurality of intrinsic components (IMFs)i) And a linear sum of trend terms, i.e. a non-stationary signal x (t), can be expressed as:
Figure RE-GDA0002360926590000091
where the frequency of IMF1 is highest and thereafter decreases, γ (t) is the trend term for very low frequencies.
Specifically, LP is extracted01Mold and LP11Respectively carrying out empirical mode decomposition on time domain signal data of vehicle vibration points of the model to obtain two groups of IMFs, eliminating extremely low frequency components in the IMFs, and carrying out integral processing on two groups of residual IMFs to obtainThe energy value of the eigenmode component of the vibration signal corresponding to the optical wave mode.
Step 5 and step 6 are to perform feature extraction on the time domain signal, and the feature extraction flow is shown in fig. 2. In the figure Fi(x) The amplitude function of the time-domain signal for the vibration point of the corresponding light wave mode (i ═ 01 denotes LP01And (5) molding. i-11 denotes LP11A mold).
Figure RE-GDA0002360926590000092
Is EMD to Fi(x) And decomposing the obtained eigenmode functions of each order.
Figure RE-GDA0002360926590000093
The integral value of each order of the eigenmode function of the corresponding mode.
Figure RE-GDA0002360926590000094
And RiVibration time domain signals F corresponding to the light wave modes respectivelyi(x) Variance and range of (c). Using LP obtained as described above01Mold and LP11And inputting the energy value, the variance and the range corresponding to the mode as characteristic values into a neural network for training.
In this embodiment, 1 piece of time domain data at the vibration point of two types of light wave modes is taken, and the variance and the range are calculated respectively. And performing decomposition and feature extraction on the two pieces of data by using EMD, wherein each piece of data can obtain 9-10 different IMFs (including trend items with extremely low frequencies), and the EMD decomposition effect graph of one piece of data is shown in FIG. 4. Taking IMF1-IMF8As a characteristic of the signal, it is subjected to integration processing to obtain 16 (two modes, one mode being 8) energy values. And the variance and the range of the time domain data of the corresponding mode are added to 16 energy values, and 20 characteristic values are input into the neural network as a sample to be trained.
Step 7, mixing the LP obtained in step 501Mold and LP11Variance and range of the modes and the LP obtained in step 601Mold and LP11And correspondingly inputting the energy value of the eigenmode component of the mode vibration signal into the neural network for training to obtain the trained neural network.
In this embodiment, the characteristic values are trained using an improved neural network algorithm based on Dropout and ADAM optimizer (not limited to such neural networks), the number of hidden nodes of the network is set to 30, the input layer activation function is ReLU, the output layer activation function is sigmoid function, and Dropout is set to 0.4, which is optimized using ADAM algorithm. The number of iterations is first set to 5000, and the optimal number of iterations is selected by a graph of the number of iterations versus the accuracy. The number of training sets, cross validation sets and test sets meets 6:2: 2.
And obtaining a trained neural network through the steps, and storing the trained neural network in a data signal processing unit of the vehicle vibration monitoring device based on the two-mode optical fiber.
(2) Actual measurement phase (see fig. 5):
step 8, collecting LP returned from the two-mode sensing optical fiber in real time01Mold and LP11Rayleigh scattered light in the backward direction of the model is combined with local oscillator light respectively to obtain LP01Mold and LP11The beam light signals are combined in a mode.
The raw data collected in the training stage is data carrying vehicle vibration signals. The original data collected in this step may or may not carry a vibration signal, and if the original data carries a vibration signal, the original data may or may not be a vibration signal of a vehicle.
Step 9, LP01Mold and LP11After the optical signal of the mode beam combination is processed by optical signal processing, photoelectric conversion and electric signal processing, LP at each sampling point of the two-mode sensing optical fiber is obtained by sampling01Mold and LP11A modulo time domain signal.
Designing different sampling rates aiming at backward Rayleigh scattering signals of different light wave modes, and compensating LP01Mold and LP11The difference in the velocity of the mode in the sensing fiber. The setting of the sampling rate parameters needs to be the same as the sampling rate set during the training phase.
The number of frames of data collected by the acquisition card in the actual measurement stage is the same as the number of frames of data collected by the acquisition card in the training stage. In this example, 500 frames of data are collected in a centralized manner each time in the training stage, and 500 frames of data should be collected in a centralized manner each time and then processed once in the actual measurement stage.
Step 10, for LP at each sampling point01Mold and LP11The time domain signals of the model are subjected to coefficient of variation processing by adopting a coefficient of variation method respectively, and two paths of LPs obtained by processing the coefficient of variation01Mold and LP11And multiplying the mode signals to obtain a disturbance curve along the optical fiber with high signal-to-noise ratio, and determining the position of the vibration point according to the disturbance curve.
And positioning the vibration signal based on a coefficient of variation method. When the neural network obtained in the training stage is used for identifying the vibration signals along the optical fiber, the digital signal processing unit cannot directly carry out empirical mode decomposition, feature extraction and neural network identification on the time domain data at all sampling points, otherwise, the longer the optical fiber length is, the more the sampling points are, and the calculated amount is multiplied. The method comprises the steps of firstly, carrying out preliminary processing on time domain data of each sampling point by adopting a coefficient of variation method, determining positions where vibration is likely to occur, and then extracting the time domain data of the positions where vibration is likely to occur to carry out neural network calculation.
The dispersion degree of the time domain data at the vibration point is far larger than that of the time domain data at the non-vibration point, the dispersion degree of the time domain data is calculated by using a variance coefficient method in statistics, and the position where vibration is likely to occur is judged. The method does not need to consider the influence of measurement dimension and dimension. The specific calculation method is as follows: separately calculate LP01And LP11And (4) judging the position information of the vibration of the optical fiber along the time domain data variation coefficient of each point (such as the sampling rate designed in the step 4, and the interval between two adjacent points is 1m in the example) of the optical fiber. The coefficient of variation CV is calculated as:
Figure RE-GDA0002360926590000101
Figure RE-GDA0002360926590000102
wherein x isiA piece of time-domain data is represented,
Figure RE-GDA0002360926590000103
is the average value of a time domain number, and n is the data volume of a piece of data. Calculated to obtain the sum of LP01And LP11And vibration information of the optical fiber along the line corresponding to the mode. And then multiplying the data processing results of the two light wave modes, removing noise interference under a single light wave mode, obtaining a vibration peak with a higher signal-to-noise ratio, and obtaining the accurate position of the vibration peak.
Step 11, as described in step 8, the data obtained in the actual measurement stage does not necessarily carry a vibration signal, so if a vibration peak exists in the disturbance curve obtained in step 10, the vibration peak LP is extracted from the original data obtained in step 901Mold and LP11The time domain signal of the modulus is fed into steps 12 and 13. And if the vibration peak is not obtained in the disturbance curve obtained in the step 10, it is indicated that the frame data does not carry a vibration signal, the frame data is ignored, the subsequent steps are not performed, and the step 8 is returned.
Step 12, extracting LP of vibration point from the original data obtained in step 901Mold and LP11Time domain data of the model, respectively for the LPs01Mold and LP11The variance and range of the time domain signal of the model are calculated to obtain LP01Mold and LP11The variance and the range of the modes are very poor.
Step 13, extracting LP of vibration point from the original data obtained in step 901Mold and LP11Modeling the time domain data using empirical mode decomposition for the LPs01Mold and LP11Decomposing the time domain signal of the module to obtain LP01Mold and LP11The eigenmode component of the mode vibration signal. And respectively to LP01Mold and LP11Integrating the eigenmode component of the mode vibration signal to obtain LP01Mold and LP11And (4) the energy value of the eigenmode component of the mode vibration signal.
The method of extracting the features of the signal at the extracted vibration point in steps 12 and 13 is the same as the method of extracting the features of the signal at the sample sampling point in steps 5 and 6.
Step 14, the LP obtained in step 1201Mold and LP11Variance and range of modes and LP obtained in step 1301Mold and LP11The energy value of the eigenmode component of the mode vibration signal is correspondingly sent to a neural network for processing, and the neural network judges and identifies whether the vibration at the position is the vehicle vibration.
It should be noted that, although the above-mentioned embodiments of the present invention are illustrative, the present invention is not limited thereto, and thus the present invention is not limited to the above-mentioned embodiments. Other embodiments, which can be made by those skilled in the art in light of the teachings of the present invention, are considered to be within the scope of the present invention without departing from its principles.

Claims (6)

1. A vehicle vibration monitoring device based on two-mode optical fibers is characterized by comprising a laser, a pulse light generator, a circulator, a mode division multiplexer, two-mode sensing optical fibers, a collection card, a digital signal processing unit, 2 polarization controllers, 2 photoelectric conversion and electric signal processing modules and 4 optical couplers;
the output end of the laser is connected with the input end of a first optical coupler, one output end of the first optical coupler is connected with the input end of a pulse light generator, and the other output end of the first optical coupler is connected with the input end of a second optical coupler;
the output end of the pulse light generator is connected with the first port of the optical circulator, and the second port of the optical circulator is connected with the LP of the mode division multiplexer01The multiplexing port of the mode division multiplexer is connected with two mode sensing optical fibers; two-mode sensing optical fibers are laid along the road ground;
the third port of the optical circulator is connected with one input end of a third optical coupler and the LP of the mode division multiplexer11The mould port is connected with one input end of the fourth optical coupler;
one output end of the second optical coupler is connected with the other input end of the third optical coupler through the first polarization controller; the other output end of the second optical coupler is connected with the other input end of the fourth optical coupler through a second polarization controller;
two output ends of the third optical coupler are simultaneously connected with two input ends of the first photoelectric conversion and electric signal processing module, and two output ends of the first photoelectric conversion and electric signal processing module are simultaneously connected with the acquisition card; two output ends of the fourth optical coupler are simultaneously connected with two input ends of the second photoelectric conversion and electric signal processing module, and two output ends of the second photoelectric conversion and electric signal processing module are simultaneously connected with the acquisition card; the output end of the acquisition card is connected with the input end of the digital signal processing unit.
2. The apparatus of claim 1, wherein the first optical coupler has a splitting ratio of 80:20, wherein 80% of the output is connected to the input of the pulse light generator, and 20% of the output is connected to the input of the second optical coupler.
3. The two-mode optical fiber-based vehicle vibration monitoring device according to claim 1, wherein the second optical coupler, the third optical coupler and the fourth optical coupler have a splitting ratio of 50: 50.
4. The apparatus according to claim 1, wherein the pulse light generator is a fiber coupled acousto-optic modulator that generates pulsed light with a pulse period that is longer than a round-trip time for light to travel through the two-mode sensing fiber.
5. The apparatus as claimed in claim 1, wherein two outputs of the first optical-to-electrical conversion and signal processing module output IQ two-path RF signals, both carrying LP01Model backward rayleigh scattered light information; two output ends of the second photoelectric conversion and electric signal processing module output IQ two-path radio frequency signals which both carry LP11And (4) mode backward Rayleigh scattering light information.
6. A vehicle vibration monitoring method based on two-mode optical fibers is characterized by comprising the following steps: the method comprises the following steps:
step 1, LP01The continuous laser of the die is divided into two paths: one path is modulated to generate LP01The mode light pulse is injected into the two-mode sensing optical fiber; the other path generates local oscillation light after polarization regulation;
step 2, enabling a sample vehicle to drive through a certain sampling point of two-mode sensing optical fibers paved on the road ground, namely a sample sampling point, generating vibration on the ground to enable the two-mode sensing optical fibers to be disturbed, and generating an LP carrying vibration information01Mold and LP11Rayleigh scattered light behind the modes;
step 3, carrying the LP of the vibration information01And LP11The Rayleigh scattering light after the mode returns to the injection ends of the two mode sensing optical fibers and is respectively combined with the local oscillator light to obtain LP01Mold and LP11The mode vibration beam combination optical signal;
step 4, for LP obtained in step 301Mold and LP11After the optical signal of the mode vibration beam combination is processed by optical signal processing, photoelectric conversion and electric signal processing, the LP of the two-mode sensing optical fiber at the sample sampling point is obtained by sampling01Mold and LP11A vibrational time domain signal of a mode;
step 5, respectively carrying out LP on the sample sampling points obtained in the step 401Mold and LP11The variance and the range of the vibration time domain signal of the mode are calculated to obtain the LP at the sample sampling point01Mold and LP11Variance and range of the modulus time domain signal;
step 6, respectively carrying out LP on the sample sampling points obtained in the step 4 by using an empirical mode decomposition method01Mold and LP11Decomposing the vibration time domain signal of the mode to obtain LP01Mold and LP11A component of a mode vibration signal eigenmode; and respectively to LP01Mold and LP11Integral processing is carried out on the eigenmode component of the mode vibration signal to obtain LP at the sampling point of the sample01Mold and LP11A magnitude of an energy of an eigenmode component of the mode vibration signal;
7, carrying out LP on the sample sampling point obtained in the step 501Mold and LP11The variance and range of the modulus time domain signal and the L at the sample sampling point obtained in step 6P01Mold and LP11The energy value of the eigenmode component of the mode vibration signal is used as sample data and is correspondingly input into a neural network for training to obtain a trained neural network;
step 8, collecting LP returned from the two-mode sensing optical fiber in real time01Mold and LP11Rayleigh scattered light in the backward direction of the model is combined with local oscillator light respectively to obtain LP01Mold and LP11A beam combination optical signal is subjected to mode combination;
step 9, for LP obtained in step 801Mold and LP11After the optical signal of the mode beam combination is processed by optical signal processing, photoelectric conversion and electric signal processing, LP of the two-mode sensing optical fiber at each sampling point is obtained by sampling01Mold and LP11A modulo time domain signal;
step 10, for the LP at each sampling point obtained in step 901Mold and LP11The time domain signals of the modes are respectively applied to the LPs by a coefficient of variation method01Mold and LP11Performing coefficient variation processing on the time domain signal of the mode, and processing the coefficient variation to obtain LP01Modulus signal and LP11Multiplying the mode signals to obtain a disturbance curve of the two-mode sensing optical fiber along the line;
step 11, if the disturbance curve obtained in the step 10 has a vibration peak, the LP at each sampling point obtained in the step 9 is used01Mold and LP11Vibration peak LP in the time domain signal of the mode01Mold and LP11The time domain signal of the modulus is sent to steps 12 and 13 simultaneously; if the disturbance curve obtained in the step 10 does not have a vibration peak, ignoring the data of the frame and returning to the step 8;
step 12, vibrating peak LP01Mold and LP11Calculating the variance and range of the time domain signal of the mode to obtain the vibration peak P01Mold and LP11Variance and range of the modulus time domain signal;
step 13, respectively carrying out LP on vibration peaks by using an empirical mode decomposition method01Mold and LP11Decomposing the time domain signal of the module to obtain LP01Mold and LP11A component of a mode vibration signal eigenmode; and respectively to LP01Mold and LP11Integrating the eigenmode component of the time domain signal to obtain the vibration peak LP01Mold and LP11A module time domain signal eigenmode component energy value;
step 14, the vibration peak LP obtained in step 1201Mold and LP11The variance and range of the modulus time domain signal and the vibration peak LP obtained in step 1301Mold and LP11And the energy value of the eigenmode component of the mode time domain signal is used as measured data and is correspondingly sent to a neural network for processing, and the neural network judges and identifies whether the vibration at the position is the vehicle vibration.
CN201911054228.8A 2019-10-31 2019-10-31 Vehicle vibration monitoring device and method based on two-mode optical fiber Pending CN110940410A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201911054228.8A CN110940410A (en) 2019-10-31 2019-10-31 Vehicle vibration monitoring device and method based on two-mode optical fiber

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201911054228.8A CN110940410A (en) 2019-10-31 2019-10-31 Vehicle vibration monitoring device and method based on two-mode optical fiber

Publications (1)

Publication Number Publication Date
CN110940410A true CN110940410A (en) 2020-03-31

Family

ID=69906395

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201911054228.8A Pending CN110940410A (en) 2019-10-31 2019-10-31 Vehicle vibration monitoring device and method based on two-mode optical fiber

Country Status (1)

Country Link
CN (1) CN110940410A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112432696A (en) * 2020-12-08 2021-03-02 上海工程技术大学 Composite optical fiber vibration sensing system based on phi-OTDR
CN113188704A (en) * 2021-04-30 2021-07-30 中国航发湖南动力机械研究所 Method and device for testing axial force of squirrel-cage elastic support, electronic equipment and medium
CN114577326A (en) * 2022-03-04 2022-06-03 广东电网有限责任公司 Distributed vibration sensing system and method based on few-mode optical fiber
CN115050189A (en) * 2022-04-26 2022-09-13 清华大学 Vehicle identification and lane positioning method and system based on distributed optical fiber sensing

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112432696A (en) * 2020-12-08 2021-03-02 上海工程技术大学 Composite optical fiber vibration sensing system based on phi-OTDR
CN113188704A (en) * 2021-04-30 2021-07-30 中国航发湖南动力机械研究所 Method and device for testing axial force of squirrel-cage elastic support, electronic equipment and medium
CN113188704B (en) * 2021-04-30 2022-07-22 中国航发湖南动力机械研究所 Method and device for testing axial force of squirrel-cage elastic support, electronic equipment and medium
CN114577326A (en) * 2022-03-04 2022-06-03 广东电网有限责任公司 Distributed vibration sensing system and method based on few-mode optical fiber
CN115050189A (en) * 2022-04-26 2022-09-13 清华大学 Vehicle identification and lane positioning method and system based on distributed optical fiber sensing
CN115050189B (en) * 2022-04-26 2024-02-13 清华大学 Vehicle identification and lane positioning method and system based on distributed optical fiber sensing

Similar Documents

Publication Publication Date Title
CN110940410A (en) Vehicle vibration monitoring device and method based on two-mode optical fiber
CN107957276B (en) Phase sensitive optical time domain reflectometer and its measurement method based on frequency-drift compensation
CN105509868B (en) Phase sensitive optical time domain reflection distributed fiber-optic sensor system phase calculation method
CN105067104B (en) Composite optical fiber sensing system and sensing method
CN101764646B (en) Wavelength-encoding optical time domain reflection test device and measurement method thereof
CN107408982A (en) Apparatus and method for the compensation of OTDR transmitter noises
CN104568119A (en) Optical fiber vibration sensing system of single light source pulse and sensing method thereof
CN106768277B (en) A kind of demodulation method of distributed optical fiber vibration sensing device
CN105371941B (en) Distributed optical fiber vibration sensing detection method based on optical circulator
CN102645268A (en) Optical frequency division multiplexing phase-sensitive optical time domain reflectometer
CN104568120B (en) Composite principle optical fiber sensing system and sensing method
CN211013220U (en) Vehicle vibration monitoring device based on two-mode optical fiber
CN104967480A (en) Method of using fractional Fourier transform to monitor optical fiber link nonlinear effect
CN102645236B (en) BOTDA (Brillouin Optical Time-domain Analyzer) system based on comb frequency spectrum continuous probe beam
CN103115695B (en) Double-sideband distributed type optical fiber sensing system parameter measuring device
CN101051869A (en) Safety monitor system of optical cable communication line
CN103644962A (en) Ultra long distance distributed optical fiber vibration sensing device
CN109120337A (en) A kind of few mould time-domain reflectomer
CN110281984A (en) High-speed maglev train positioning system and localization method based on optical frequency domain reflection technology
CN103017887A (en) Optical fiber vibration sensing system and detection method thereof
Wang et al. Distributed optical fiber vibration sensor using generalized cross-correlation algorithm
CN102445416B (en) Real-time online nondestructive detection device for composite material
CN105651373A (en) Two-point synchronous vibration measuring method based on polarization optical time-domain reflection technology
CN108317402B (en) Distributed optical fiber sensing positioning early warning analysis method
CN104210512B (en) A kind of monitor the method that H steel draw-in groove in high-speed rail sound barrier loosens

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination