CN114777903A - Multi-point vibration detection method and device for optical frequency domain reflectometer based on signal cross correlation - Google Patents
Multi-point vibration detection method and device for optical frequency domain reflectometer based on signal cross correlation Download PDFInfo
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Abstract
The invention discloses a multi-point vibration detection method and a device of an optical frequency domain reflectometer based on signal cross correlation, which comprises the following steps: on the basis of constructing a non-vibration signal for simulation and a vibration signal according to the frequency of a historical vibration point, constructing a current simulation cross-correlation curve according to the non-vibration signal for simulation and the high-frequency vibration signal for current simulation to determine a vibration point, and calculating the frequency of the vibration point.
Description
Technical Field
The invention belongs to the field of distributed optical fiber sensing, and particularly relates to a multi-point vibration detection method and device for an optical frequency domain reflectometer based on signal cross-correlation.
Background
Distributed fiber sensing technology has the capability of distributed measurement, enabling detection of a continuous distribution of measurands over time and space. The optical frequency domain reflectometer detects the quantity to be measured by detecting the phase change of the light, has the advantages of high resolution and electromagnetic interference resistance, has good application prospect, and is suitable for long-distance distributed measurement.
The literature Ding Z, Yang D, Liu K, et al, Long-Range OFDR-Based Distributed Vibration optics of Rayleigh Scattering [ J ] IEEE semiconductors Journal,2017,9(5):1-10. Low frequency detection of two points of Optical Frequency Domain Reflectometry (OFDR) was performed, the position and frequency of a first Vibration point were successfully obtained on an Optical Fiber up to several tens km in length by using a threshold positioning method, and the position of a second Vibration point was positioned by using a multi-parameter positioning method, but the positions of the two Vibration points were relatively short.
When the optical frequency domain reflectometer system performs frequency sweeping, certain nonlinear change interference generally exists, and corresponding information can be deteriorated when signals are collected and processed, so that the performance of the system is influenced. In the existing research, the influence of nonlinear variation can be greatly reduced by adding a compensation structure and assisting a corresponding algorithm, such as the documents Tiegen, Liu, Yang, et al.40-km OFDR-Based Distributed distribution Optical Fiber Sensor [ J ]. IEEE Photonics Technology Letters,2016,28(7):771-774.
Patent document CN112229501A discloses an apparatus and method for automatically detecting a vibration signal based on OFDR, and specifically, the apparatus and method locate the position of single-point vibration based on cross correlation coefficients and an automatic discrimination threshold curve, and cannot realize multi-point vibration detection.
In short, the analysis of the conventional optical frequency domain reflectometer system as described above fails to realize multi-point vibration detection for detecting high-frequency vibration of the optical frequency domain reflectometer.
Disclosure of Invention
In view of the above, the present invention provides a method and an apparatus for detecting multipoint oscillation of optical frequency domain reflectometer based on signal cross-correlation, which can detect multipoint oscillation of high frequency oscillation.
In order to achieve the above object, an embodiment of the present invention provides a method for detecting multipoint vibration of an optical frequency domain reflectometer based on signal cross-correlation, including the following steps:
step 3, constructing a non-vibration signal for simulation, constructing a high-frequency vibration signal for current simulation according to the historical vibration point frequency, performing cross-correlation simulation calculation on the non-vibration signal for simulation and the high-frequency vibration signal for current simulation, and constructing a current simulation cross-correlation curve according to cross-correlation values;
step 4, carrying out difference calculation on corresponding points of the current simulated cross-correlation curve and the actual cross-correlation curve, taking the average value of the difference values as a current screening threshold value, taking the position of the screening difference value larger than the current screening threshold value as a vibration point determined by the current round, and calculating the frequency of the vibration point;
and 5, repeating the steps 3 and 4 to detect and obtain a plurality of vibration points and vibration point frequencies.
Preferably, in step 1, FFT processing is performed on the non-vibration signal and the vibration signal respectively to convert the signals into a frequency domain, so as to obtain an amplitude-frequency graph corresponding to the non-vibration signal and the vibration signal respectively, and the amplitude-frequency graph is scaled to the length of the optical fiber based on the linear relationship between the frequency value and the actual position of the optical fiber, so that the frequency value corresponds to the actual position of the optical fiber one to one.
Preferably, in step 2, constructing an actual cross-correlation curve according to the cross-correlation values, includes: and taking the calculated cross-correlation value as a vertical coordinate and the signal transmission distance as a horizontal coordinate to construct an actual cross-correlation curve.
Preferably, in step 2, locating the 1 st vibration point according to the actual cross-correlation curve comprises: averaging all cross-correlation values on the actual cross-correlation curve to obtain a first screening threshold, and screening the position larger than the first screening threshold on the actual cross-correlation curve as a 1 st vibration point.
Preferably, in step 3, constructIs not vibrating signal E for simulationSi(t)' is:
ESi(t)′＝E0exp{j[2πf0(t-τLi)+πγ(t-τLi)2]}
constructing high-frequency vibration signal E for current simulation according to historical vibration point frequencySi(t) is:
δi＝cos(2pili/L)
L＝v/(2fvi)
wherein, E0Representing the intensity of the light field, t time, τLiDelay time of a point on the fiber from the origin, f0Eigenfrequency of light, fviIndicates the ith vibration point frequency, liThe length of a point on the fiber from the location of vibration, v is the speed of light in the fiber, L is the length of one modulation period, and fviRelated to, deltaiRepresenting a modulated signal.
Preferably, the calculation process of the vibration point frequency comprises the following steps:
taking the corresponding position of the vibration point in the amplitude-frequency diagram corresponding to the non-vibration signal as a non-vibration origin;
and taking the corresponding position of the vibration point in the amplitude-frequency graph corresponding to the vibration signal as a vibration origin, calculating the cross-correlation value of the adjacent preamble frequency sequence of the vibration origin and the frequency corresponding to the non-vibration origin, and selecting the frequency corresponding to the maximum cross-correlation value as the vibration point frequency.
The adjacent preamble frequency sequence of the vibration origin is a sequence formed by all frequencies from the vibration origin as a reference to the previous vibration point frequency.
To achieve the above object, an embodiment of the present invention further provides an optical frequency domain reflectometer multipoint vibration detecting apparatus based on signal cross correlation, including a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor implements the following steps when executing the computer program:
step 3, constructing a non-vibration signal for simulation, constructing a high-frequency vibration signal for current simulation according to the historical vibration point frequency, performing cross-correlation simulation calculation on the non-vibration signal for simulation and the high-frequency vibration signal for current simulation, and constructing a current simulation cross-correlation curve according to cross-correlation values;
step 4, carrying out difference calculation on corresponding points of the current simulated cross-correlation curve and the actual cross-correlation curve, taking the average value of the difference values as a current screening threshold value, taking the position of the screening difference value larger than the current screening threshold value as a vibration point determined by the current round, and calculating the frequency of the vibration point;
and 5, repeating the steps 3 and 4 to detect and obtain a plurality of vibration points and vibration point frequencies.
Compared with the prior art, the invention has the beneficial effects that at least:
on the basis of constructing a non-vibration signal for simulation and a vibration signal according to the historical vibration point frequency, constructing a current simulation cross-correlation curve according to the non-vibration signal for simulation and the high-frequency vibration signal for current simulation to determine a vibration point, and calculating the vibration point frequency.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 and fig. 2 are flow charts of a multipoint vibration detection method of an optical frequency domain reflectometer based on signal cross-correlation provided by an embodiment;
FIG. 3 is a schematic diagram of the location of vibration points provided by the embodiment;
fig. 4 is a graph of the analysis result of the vibration point frequency provided by the embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the detailed description and specific examples, while indicating the scope of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
In order to solve the problem of multi-point multi-frequency vibration of OFDR detection high-frequency vibration, the embodiment provides a method and a device for OFDR multi-point vibration detection based on signal cross-correlation.
Fig. 1 and fig. 2 are flowcharts of a multipoint vibration detection method of an optical frequency domain reflectometer based on signal cross-correlation according to an embodiment. As shown in fig. 1 and fig. 2, the embodiment provides a multipoint vibration detection method of an optical frequency domain reflectometer based on signal cross-correlation, comprising the following steps:
In the embodiment, the non-vibration signal and the vibration signal in the distributed optical fiber are collected by a collection card of an optical frequency domain reflectometer, and the collected non-vibration signal and the collected vibration signal are subjected to frequency domain conversion and scaling adjustment.
Specifically, FFT (fast fourier transform) processing is performed on the non-vibration signal and the vibration signal respectively to convert the signals into a frequency domain, so as to obtain an amplitude-frequency graph corresponding to the non-vibration signal and the vibration signal respectively, and the amplitude-frequency graph is scaled to the length of the optical fiber based on the linear relationship between the frequency value and the actual position of the optical fiber, so that the frequency value corresponds to the actual position of the optical fiber one to one.
And 2, performing cross-correlation calculation on the non-vibration signal and the vibration signal processed in the step 1, constructing an actual cross-correlation curve according to the cross-correlation value, positioning a 1 st vibration point according to the actual cross-correlation curve, and calculating the frequency of the 1 st vibration point.
In the embodiment, cross-correlation calculation is performed on the amplitude-frequency diagram corresponding to the non-vibration signal and the signal amplitude in the amplitude-frequency diagram corresponding to the vibration signal to obtain a cross-correlation value, and an actual cross-correlation curve is constructed according to the cross-correlation value.
In an embodiment, locating the 1 st vibration point according to the actual cross-correlation curve comprises: averaging all cross-correlation values on the actual cross-correlation curve to obtain a first screening threshold A, screening all position points on the actual cross-correlation curve, and when the cross-correlation data of a certain position point is greater than the first screening threshold A, taking the position point as a 1 st vibration point.
In the embodiment, after the 1 st vibration point is determined, the 1 st vibration point frequency is calculated, and the 1 st vibration point frequency is used for constructing a high-frequency vibration signal for modeling simulation. Specifically, determining the 1 st vibration point frequency comprises: taking the corresponding position of the vibration point in the amplitude-frequency diagram corresponding to the non-vibration signal as a non-vibration origin point; and taking the corresponding position of the vibration point in the amplitude-frequency diagram corresponding to the vibration signal as a vibration origin, calculating the cross-correlation value of the adjacent preorder frequency sequence of the vibration origin and the frequency corresponding to the non-vibration origin, and selecting the frequency corresponding to the maximum cross-correlation value as the vibration point frequency.
It should be noted that the adjacent preamble frequency sequence of the vibration origin refers to a sequence formed by all frequencies from the forward distance to the previous vibration point frequency with the vibration origin as a reference. For the 1 st vibration origin, the adjacent preamble frequency sequence refers to a sequence of all frequencies from the zero point to the current vibration origin.
In the embodiment, due to the existence of the vibration signal corresponding to the 1 st vibration point, the left end and the right end of the frequency after the vibration signal position carry the frequency signals with the same intensity, and the distances between the center frequencies corresponding to the vibration points are equal, that is, the frequency intervals are equal. Based on the above, the cross-correlation value of the adjacent subsequent frequency sequence of the vibration origin and the frequency corresponding to the non-vibration origin can be calculated, and the frequency corresponding to the maximum cross-correlation value is selected as the vibration point frequency. Observing the calculation result, the vibration point frequency determined by the adjacent preamble frequency sequence and the calculation according to the adjacent preamble frequency sequence is equal.
It should be noted that the adjacent subsequent frequency sequence is a sequence formed by taking the vibration origin as a reference and ranging from all frequencies in a next frequency segment, and the length of the adjacent subsequent frequency sequence is equal to that of the adjacent preceding frequency sequence.
And 3, constructing a non-vibration signal for simulation, constructing a high-frequency vibration signal for current simulation according to the historical vibration point frequency, performing cross-correlation simulation calculation on the non-vibration signal for simulation and the high-frequency vibration signal for current simulation, and constructing a current simulation cross-correlation curve according to the cross-correlation value.
Since the non-vibration signal and the vibration signal transmitted in the distributed optical fiber collected by the optical frequency domain reflectometer are high-frequency vibration signals, the non-vibration signal for simulation and the high-frequency vibration signal for simulation are constructed based on the periodic variation of the high-frequency vibration signals.
Specifically, the constructed non-vibration signal E for simulationSi(t)' is:
ESi(t)′＝E0exp{j[2πf0(t-τLi)+πγ(t-τLi)2]}
constructing high-frequency vibration signal E for current simulation according to historical vibration point frequencySi(t) is:
δi＝cos(2pili/L)
L＝v/(2fvi)
wherein E is0Representing the intensity of the light field, t time, τLiDelay time of a point on the fiber from the origin, f0Eigenfrequency of light, fviIndicates the ith vibration point frequency, liThe length of a point on the fiber from the vibration location, v is the speed of light in the fiber, L is the length of one modulation period, and fviRelated to, deltaiThe modulation signal is represented, and the historical vibration point frequencies are all the vibration point frequencies calculated up to the present.
After the non-vibration signal for simulation and the high-frequency vibration signal for current simulation are obtained through construction, the signals are converted into a frequency domain through sampling by adopting FFT (fast Fourier transform algorithm), amplitude-frequency graphs corresponding to the non-vibration signal for simulation and the vibration signal for current simulation are obtained, and the amplitude-frequency graphs are scaled to the length of the optical fiber, so that the frequency values correspond to the actual positions of the optical fiber one by one.
In the embodiment, when cross-correlation simulation analog calculation is performed on the non-vibration signal for simulation and the high-frequency vibration signal for current simulation, the signal amplitude in an amplitude-frequency diagram is specifically subjected to cross-correlation calculation to obtain a cross-correlation value, and a current simulation cross-correlation curve is constructed according to the cross-correlation value.
And 4, carrying out difference calculation on corresponding points of the current simulated cross-correlation curve and the actual cross-correlation curve, taking the average value of the difference values as a current screening threshold value, taking the position where the screening difference value is greater than the current screening threshold value as a vibration point determined by the current round, and calculating the frequency of the vibration point.
In the embodiment, the periodicity of the high-frequency vibration signal is utilized, and the position and the frequency of the front n-1(n is more than or equal to 2) vibration points are analyzed to simulate and reconstruct the current simulated cross-correlation curve of which the cross-correlation of only n-1 vibration points is distributed according to the distance. And (3) carrying out difference calculation on the simulated reconstructed cross-correlation curve and the corresponding point of the actual cross-correlation curve obtained in the step (2) according to the actual data stage, adding and averaging the difference results to obtain a current screening threshold value B, and when the difference value at a certain position in the distance-distributed difference curve exceeds the current screening threshold value B, determining the position as the vibration point determined in the current round.
Because the high-frequency vibration signals for simulation constructed in each round are constructed according to the historical vibration point frequency, the vibration points determined in the current round obtained by calculation are different.
In the embodiment, the frequency of the vibration point determined by calculating the current round is the same as that in step 2, and is not described herein again.
And 5, repeating the steps 3 and 4 to detect and obtain a plurality of vibration points and vibration point frequencies.
In the circulation process of the step 3 and the step 4, the position of the 2 nd vibration point is positioned by adopting a mode of combining frequency simulation reconstruction and cross-correlation numerical value positioning, and meanwhile, the frequency of the 2 nd vibration point is calculated. And then, carrying out frequency simulation reconstruction on the obtained 1 st and 2 nd vibration point frequencies to obtain a simulation cross-correlation curve with only 1 and 2 vibration points, and positioning the 3 rd vibration point position and frequency by a method combining the frequency simulation reconstruction and cross-correlation numerical positioning. According to the process, the frequency simulation is carried out in a circulating mode to reconstruct the simulated cross-correlation curve of only 1,2, …, n (n is more than or equal to 1) vibration points, and then the position and the frequency of the (n + 1) th vibration point are positioned.
According to the optical frequency domain reflectometer multipoint vibration detection method based on signal cross correlation, specific calculation detection is carried out, and fig. 3 is a vibration positioning result graph, and multipoint multi-frequency vibration is realized on a 10km optical fiber. A vibration source A with the vibration frequency of 50kHz is arranged at the position of 1km, a vibration source B with the vibration frequency of 20kHz is arranged at the position of 3km, and the vibration position at the position of 1km and the vibration position at the position of 3km are successfully positioned by adopting the method. Fig. 4 is a graph showing the result of frequency analysis of the vibration position. Wherein, (1) is 1km place, vibration source A vibration frequency analytic graph; (2) at 3km, vibration source B vibrates the frequency resolution chart.
Embodiments also provide an optical frequency domain reflectometry multipoint vibration detection apparatus based on signal cross-correlation, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the following steps when executing the computer program:
step 3, constructing a non-vibration signal for simulation, constructing a high-frequency vibration signal for current simulation according to the historical vibration point frequency, performing cross-correlation simulation calculation on the non-vibration signal for simulation and the high-frequency vibration signal for current simulation, and constructing a current simulation cross-correlation curve according to cross-correlation values;
step 4, carrying out difference calculation on corresponding points of the current simulated cross-correlation curve and the actual cross-correlation curve, taking the average value of the difference values as a current screening threshold value, taking the position of the screening difference value larger than the current screening threshold value as a vibration point determined by the current round, and calculating the frequency of the vibration point;
and 5, repeating the steps 3 and 4 to detect and obtain a plurality of vibration points and vibration point frequencies.
It should be noted that the computer memory may be volatile memory at the near end, such as RAM, or non-volatile memory, such as ROM, FLASH, floppy disk, mechanical hard disk, etc., or may be a remote storage cloud. The computer processor may be a Central Processing Unit (CPU), microprocessor unit (MPU), Digital Signal Processor (DSP), or Field Programmable Gate Array (FPGA), i.e., the steps of optical frequency domain reflectometry multi-point vibration detection based on signal cross-correlation may be implemented by these processors.
The technical solutions and advantages of the present invention have been described in detail in the foregoing detailed description, and it should be understood that the above description is only the most preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, additions, and equivalents made within the scope of the principles of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A multi-point vibration detection method of an optical frequency domain reflectometer based on signal cross correlation is characterized by comprising the following steps:
step 1, acquiring an un-vibration signal and a vibration signal in a distributed optical fiber, converting the signals into a frequency domain, and scaling signal data to the length of the optical fiber according to a proportion;
step 2, performing cross-correlation calculation on the non-vibration signal and the vibration signal processed in the step 1, constructing an actual cross-correlation curve according to cross-correlation values, positioning a 1 st vibration point according to the actual cross-correlation curve, and calculating the frequency of the 1 st vibration point;
step 3, constructing a non-vibration signal for simulation, constructing a high-frequency vibration signal for current simulation according to the historical vibration point frequency, performing cross-correlation simulation calculation on the non-vibration signal for simulation and the high-frequency vibration signal for current simulation, and constructing a current simulation cross-correlation curve according to cross-correlation values;
step 4, carrying out difference calculation on corresponding points of the current simulated cross-correlation curve and the actual cross-correlation curve, taking the average value of difference values as a current screening threshold value, taking the position where the screening difference value is larger than the current screening threshold value as a vibration point determined by the current round, and calculating the frequency of the vibration point;
and 5, repeating the steps 3 and 4 to detect and obtain a plurality of vibration points and vibration point frequencies.
2. The multi-point vibration detection method for optical frequency domain reflectometry based on signal cross-correlation as in claim 1, wherein in step 1, FFT processing is performed on the un-vibrated signal and the vibrated signal respectively to convert the signals to the frequency domain, so as to obtain amplitude-frequency graphs corresponding to the un-vibrated signal and the vibrated signal respectively, and the amplitude-frequency graphs are scaled to the length of the optical fiber based on the linear relationship between the frequency values and the actual positions of the optical fiber, so that the frequency values correspond to the actual positions of the optical fiber one to one.
3. The method for detecting multipoint vibration of optical frequency domain reflectometer based on signal cross-correlation as claimed in claim 1, wherein in step 2, constructing an actual cross-correlation curve based on the cross-correlation values comprises: and taking the calculated cross-correlation value as a vertical coordinate and the signal transmission distance as a horizontal coordinate to construct an actual cross-correlation curve.
4. The multi-point vibration detection method based on optical frequency domain reflectometry in signal cross-correlation as claimed in claim 1, wherein in step 2, locating the 1 st vibration point according to the actual cross-correlation curve comprises: and averaging all cross-correlation values on the actual cross-correlation curve to obtain a first screening threshold, and screening the position larger than the first screening threshold on the actual cross-correlation curve as a 1 st vibration point.
5. The method for detecting multipoint vibration of optical frequency domain reflectometer based on signal cross-correlation as claimed in claim 1, wherein in step 3, the constructed non-vibration signal E for simulation isSi(t)' is:
ESi(t)′＝E0exp{j[2πf0(t-τLi)+πγ(t-τLi)2]}
constructing high-frequency vibration signal E for current simulation according to historical vibration point frequencySi(t) is:
δi＝cos(2pili/L)
L＝v/(2fvi)
wherein E is0Representing the intensity of the light field, t time, τLiThe delay time from a point on the fiber to the origin,f0eigenfrequency of light, fviIndicates the ith vibration point frequency, liThe length of a point on the fiber from the vibration location, v is the speed of light in the fiber, L is the length of one modulation period, and fviRelated to, deltaiRepresenting a modulated signal.
6. The multi-point vibration detection method based on optical frequency domain reflectometry in signal cross-correlation as claimed in claim 2, wherein the calculation process of vibration point frequency comprises:
taking the corresponding position of the vibration point in the amplitude-frequency diagram corresponding to the non-vibration signal as a non-vibration origin point;
and taking the corresponding position of the vibration point in the amplitude-frequency diagram corresponding to the vibration signal as a vibration origin, calculating the cross-correlation value of the adjacent preorder frequency sequence of the vibration origin and the frequency corresponding to the non-vibration origin, and selecting the frequency corresponding to the maximum cross-correlation value as the vibration point frequency.
7. The multi-point vibration detection method based on optical frequency domain reflectometry (OSDR) of claim 6, wherein the adjacent preamble frequency sequence of the vibration origin is a sequence formed by all frequencies from the vibration origin as a reference to the previous vibration point frequency.
8. An optical frequency domain reflectometry multipoint vibration detection apparatus based on signal cross correlation, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the following steps when executing the computer program:
step 1, acquiring an un-vibration signal and a vibration signal in a distributed optical fiber, converting the signals into a frequency domain, and scaling signal data to the length of the optical fiber according to a proportion;
step 2, performing cross-correlation calculation on the non-vibration signal and the vibration signal processed in the step 1, constructing an actual cross-correlation curve according to cross-correlation values, positioning a 1 st vibration point according to the actual cross-correlation curve, and calculating the frequency of the 1 st vibration point;
step 3, constructing a non-vibration signal for simulation, constructing a high-frequency vibration signal for current simulation according to the historical vibration point frequency, performing cross-correlation simulation calculation on the non-vibration signal for simulation and the high-frequency vibration signal for current simulation, and constructing a current simulation cross-correlation curve according to cross-correlation values;
step 4, carrying out difference calculation on corresponding points of the current simulated cross-correlation curve and the actual cross-correlation curve, taking the average value of difference values as a current screening threshold value, taking the position where the screening difference value is larger than the current screening threshold value as a vibration point determined by the current round, and calculating the frequency of the vibration point;
and 5, repeating the steps 3 and 4 to detect and obtain a plurality of vibration points and vibration point frequencies.
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