CN114543851A - Phase-sensitive optical time domain reflectometer signal conditioning method for improving signal-to-noise ratio and detail characteristics - Google Patents

Phase-sensitive optical time domain reflectometer signal conditioning method for improving signal-to-noise ratio and detail characteristics Download PDF

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CN114543851A
CN114543851A CN202210185871.XA CN202210185871A CN114543851A CN 114543851 A CN114543851 A CN 114543851A CN 202210185871 A CN202210185871 A CN 202210185871A CN 114543851 A CN114543851 A CN 114543851A
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point
rayleigh scattering
time
time diagram
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杜立普
沈玉彬
张华�
尹亮
邹璇
齐敦哲
陈文婷
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Water Conservancy Construction Center Of Ningxia Hui Autonomous Region
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    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
    • G01D5/35354—Sensor working in reflection
    • G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
    • G01D5/35361—Sensor working in reflection using backscattering to detect the measured quantity using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
    • G06F2218/02—Preprocessing
    • G06F2218/04—Denoising
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
    • G06F2218/08—Feature extraction

Abstract

The invention discloses a signal conditioning method of a phase-sensitive optical time domain reflectometer for improving signal-to-noise ratio and detail characteristics, which comprises the following steps: respectively obtaining smoothed Rayleigh scattering curves when the first smoothing operator and the second smoothing operator traverse the Rayleigh scattering curves, obtaining the Rayleigh scattering curves subjected to point-by-point combination, fitting and constructing a new curve between two adjacent Rayleigh scattering curves to obtain 2n-1 Rayleigh scattering curves in total, splicing into a space-time diagram, and using a 1 multiplied by 5 template to pair the initial space-time diagram P1Filtering to obtain filtered space-time diagram P2With 3X 3 template pairs P1Filtering, namely updating the 3 x 3 template to realize filtering for a plurality of times to obtain space-time diagrams with different characteristics; merging the filtered space-time diagrams corresponding to the 3 multiplied by 3 templates, and calculating the mean value point by point of the gray values of the space-time diagrams at the same position as the result of the second filtering to obtain a space-time diagram P3(ii) a To time-space diagram P2And space-time diagram P3Point-by-point mergingAnd obtaining a final space-time diagram P. The invention effectively improves the signal-to-noise ratio of the Rayleigh scattering curve and the time space diagram, and ensures the reliability of the system.

Description

Phase-sensitive optical time domain reflectometer signal conditioning method for improving signal-to-noise ratio and detail characteristics
Technical Field
The invention relates to the field of distributed optical fiber sensing, in particular to a method for improving signal-to-noise ratio and detail characteristics
Figure BDA0003522823510000011
A signal conditioning method (phase-sensitive optical time domain reflectometer).
Background
Distributed optical fiber sensing has become a widely used sensing means in recent years, among them
Figure BDA0003522823510000012
The method is applied to the fields of intrusion early warning, pipeline broken wire detection, event positioning and the like by virtue of the advantages of mature technology, simple structure and the like.
Figure BDA0003522823510000013
Continuous narrow-linewidth light pulses are emitted to the sensing optical cable through the light pulse modulation device, when an external event acts on the optical cable, the optical fiber at the acting point acts on the light pulses, and backward Rayleigh scattering light formed carries relevant information of the event, so that a sensing function based on Rayleigh scattering light is realized. Rayleigh scattering curve is
Figure BDA0003522823510000014
The important data bearing mode reflects the space characteristics of the optical cable along the line. And superposing the Rayleigh scattering curves within a certain time range to obtain a space-time diagram representing time and space characteristics along the optical cable. When a breakpoint or light attenuation caused by torsion exists at a certain position of the optical cable, a significant reflection peak is shown on a Rayleigh scattering curve; when the optical cable has intrusion information such as knocking, digging and the like along the line, the space-time diagram presents characteristic color blocks different from background noise to represent event occurrenceThe spatial location of the birth, the initial time, and the time span.
In practical application, due to the existence of a large amount of background noise, the signal to noise ratio of the acquired data is greatly reduced after the noise is superimposed on the acquired data under an ideal condition, and a large amount of point-like and strip-like characteristic color blocks are displayed on a time-space diagram even under a static condition, so that the stability and the reliability of the system are seriously influenced.
Disclosure of Invention
The invention provides a method for improving signal-to-noise ratio and detail characteristics
Figure BDA0003522823510000015
The invention relates to a signal conditioning method, which comprehensively obtains the characteristics of Rayleigh scattering signals on different frequency components in a signal acquisition stage, realizes smooth denoising and image enhancement of a Rayleigh scattering curve by refining the characteristic details of a space-time diagram and filtering for multiple times under different templates in a space-time diagram construction stage, can effectively reduce the interference caused by noise, and greatly improves the noise
Figure BDA0003522823510000016
The reliability and the measurement accuracy of the method effectively improve the signal-to-noise ratio of the Rayleigh scattering curve and the time space diagram, and ensure the reliability of the system, as described in detail in the following: method for improving signal-to-noise ratio and detail characteristics
Figure BDA0003522823510000017
A method of signal conditioning, the method comprising:
performing data alignment operation of sampling point supplement on the primarily processed Rayleigh scattering signals to obtain three paths of aligned Rayleigh scattering curve signals, and obtaining three paths of point-by-point combined Rayleigh scattering weighted signals according to weighting parameters; combining the three paths of Rayleigh scattering weighting signals point by point to obtain a preprocessed Rayleigh scattering curve x (t);
moving from the head end to the tail end of the Rayleigh scattering curve x (t) by taking the centers of the first and second smoothing operators as starting points, and if the center of the template covers the lower part and lacks of data points, carrying out zero filling calculation to obtain the first and second smoothing operatorsAfter x (t), obtaining the Rayleigh scattering curve L after smoothing1、L2；
Obtaining a smoothed Rayleigh scattering curve L1、L2Performing point-by-point combination on the Rayleigh scattering curves K, and fitting two adjacent Rayleigh scattering curves to construct a new Rayleigh scattering curve, so as to obtain 2n-1 Rayleigh scattering curves; splicing 2n-1 Rayleigh scattering curves into a space-time diagram, and marking the initial space-time diagram as P1；
Initial space-time diagram P with 1 x 5 template pair1Filtering to obtain filtered space-time diagram P2Using a 3 × 3 template to pair the initial space-time diagram P1Filtering, namely updating the 3 x 3 template to realize filtering for a plurality of times to obtain space-time diagrams with different characteristics;
merging the filtered space-time diagrams corresponding to the 3 multiplied by 3 templates, and calculating the mean value point by point of the gray values of the space-time diagrams at the same position as the result of the second filtering to obtain a space-time diagram P3(ii) a To time-space diagram P2And space-time diagram P3And combining point by point to obtain a final space-time diagram P.
Wherein the method further comprises:
primarily collecting the Rayleigh scattering signals by adopting a three-channel signal collection mode to obtain three paths of Rayleigh scattering curve signals; and adopting different cut-off frequencies to carry out preliminary filtering on the three paths of Rayleigh scattering curve signals.
Further, the obtaining of the point-by-point combined rayleigh scattering weighting signal according to the weighting parameters specifically includes:
point-by-point merging X1(t)、X2(t) the combined formula is
Figure BDA0003522823510000021
Point-by-point merging X2(t)、X3(t) the combined formula is
Figure BDA0003522823510000022
Point-by-point merging X3(t)、X1(t) the combined formula is
Figure BDA0003522823510000023
Wherein l1、l2、l3As a weighting factor, X1(t)、X2(t)、X3And (t) three paths of aligned Rayleigh scattering signals. Wherein the first and second smoothing operators are:
σ1＝{σ1i}＝k{-(i-α)2+b},σ2＝{σ2i}＝k{|(α-i)3|+b}
wherein σ1iRepresenting the first smoothing operator sigma1Value of each element in (a)2iRepresenting the second smoothing operator σ2The value of each element in the Chinese character is obtained; k is a gain coefficient; i represents the ith element on the smoothing operator; alpha and b are operator smoothing direction adjustment constants.
Wherein, the 3 × 3 template is:
Figure BDA0003522823510000031
wherein the content of the first and second substances,
Figure BDA0003522823510000032
further, the time-space diagram P2And space-time diagram P3Point-by-point combination is carried out, and a final time-space diagram P is obtained:
Figure BDA0003522823510000033
in the formula, PijRepresenting the gray value, P, of the merged space-time diagram2ijRepresenting a space-time diagram P2Pixel point of upper corresponding position, P3ijRepresenting a space-time diagram P3And the pixel points of the corresponding positions.
The technical scheme provided by the invention has the beneficial effects that:
1. the method comprises the steps of performing three-channel sampling on initial Rayleigh scattering signals, respectively performing filtering processing, and comprehensively acquiring signal characteristics of the Rayleigh scattering signals on different frequency components;
2. according to the invention, the characteristic details of the space-time diagram are refined by performing curve interpolation processing on the Rayleigh scattering curve used for constructing the space-time diagram;
3. according to the invention, through filtering processing under different templates on the space-time image, image characteristics with different characteristics are extracted, smooth denoising and image enhancement on the space-time image are realized, and the signal-to-noise ratio of the space-time image is improved; is greatly lifted
Figure BDA0003522823510000034
The reliability and the measurement accuracy of the method effectively improve the signal to noise ratio of the Rayleigh scattering curve and the space-time diagram, and ensure the reliability of the system.
Drawings
FIG. 1 is a flow chart of signal acquisition;
FIG. 2 is a schematic optical path diagram of the system illustrating a flow chart of data processing and image enhancement;
fig. 3 is a schematic diagram of a curve smoothing operation in data processing.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below.
Example 1
Method for improving signal-to-noise ratio and detail characteristics
Figure BDA0003522823510000044
Signal conditioning method, see fig. 1, comprising the steps of:
101: performing data alignment operation of sampling point supplement on the primarily processed Rayleigh scattering signals to obtain three paths of aligned Rayleigh scattering curve signals, and obtaining three paths of point-by-point combined Rayleigh scattering weighted signals according to weighting parameters; combining the three paths of Rayleigh scattering weighting signals point by point to obtain a preprocessed Rayleigh scattering curve x (t);
102: moving from the head end to the tail end of the Rayleigh scattering curve x (t) by taking the centers of the first and second smoothing operators as starting points, and if the template is usedWhen the data points are lacked under the central coverage, zero filling calculation is carried out, and when the first smoothing operator and the second smoothing operator are obtained and x (t) is traversed, a smoothed Rayleigh scattering curve L is obtained respectively1、L2；
103: obtaining a smoothed Rayleigh scattering curve L1、L2Performing point-by-point combination on the Rayleigh scattering curves K, and fitting two adjacent Rayleigh scattering curves to construct a new Rayleigh scattering curve, so as to obtain 2n-1 Rayleigh scattering curves; splicing 2n-1 Rayleigh scattering curves into a space-time diagram, and marking the initial space-time diagram as P1；
104: initial space-time diagram P with 1 x 5 template pair1Filtering to obtain filtered space-time diagram P2Using a 3 × 3 template to pair the initial space-time diagram P1Filtering, namely updating the 3 x 3 template to realize filtering for a plurality of times to obtain space-time diagrams with different characteristics;
105: merging the filtered space-time diagrams corresponding to the 3 multiplied by 3 templates, and calculating the mean value point by point of the gray values of the space-time diagrams at the same position as the result of the second filtering to obtain a space-time diagram P3(ii) a To time-space diagram P2And space-time diagram P3And combining point by point to obtain a final space-time diagram P.
Wherein, before step 101, the method further comprises:
primarily collecting the Rayleigh scattering signals by adopting a three-channel signal collection mode to obtain three paths of Rayleigh scattering curve signals;
and performing primary filtering on the three paths of Rayleigh scattering curve signals by adopting different cut-off frequencies.
The obtaining of the point-by-point combined rayleigh scattering weighted signal according to the weighting parameter in step 101 is specifically:
point-by-point merging X1(t)、X2(t) the combined formula is
Figure BDA0003522823510000041
Point-by-point merging X2(t)、X3(t) the combined formula is
Figure BDA0003522823510000042
Point-by-point merging X3(t)、X1(t) the combined formula is
Figure BDA0003522823510000043
Wherein l1、l2、l3As a weighting factor, X1(t)、X2(t)、X3And (t) three paths of aligned Rayleigh scattering signals.
Wherein, the first and second smoothing operators in step 102 are:
σ1＝{σ1i}＝k{-(i-α)2+b},σ2＝{σ2i}＝k{|(α-i)3|+b}
wherein σ1iRepresenting the first smoothing operator σ1Value of each element in (a)2iRepresenting the second smoothing operator σ2The value of each element in the Chinese character is obtained; k is a gain coefficient; i represents the ith element on the smoothing operator; alpha and b are operator smoothing direction adjustment constants.
Wherein, the 3 × 3 template in step 104 is:
Figure BDA0003522823510000051
wherein the content of the first and second substances,
Figure BDA0003522823510000052
wherein, the time-space diagram P in step 1052And space-time diagram P3Point-by-point combination is carried out, and the final space-time diagram P is obtained as follows:
Figure BDA0003522823510000053
in the formula, PijRepresenting the gray value, P, of the merged space-time diagram2ijRepresenting a space-time diagram P2Pixel point of upper corresponding position, P3ijRepresenting a space-time diagram P3At upper corresponding positionAnd (6) pixel points.
In summary, the embodiment of the present invention implements smooth denoising and image enhancement on the spatiotemporal image through the above steps 101 to 105, and improves the signal-to-noise ratio of the spatiotemporal image; is greatly lifted
Figure BDA0003522823510000054
The reliability and the measurement accuracy of the method effectively improve the signal to noise ratio of the Rayleigh scattering curve and the space-time diagram, and ensure the reliability of the system.
Example 2
The scheme of example 1 is further described below with reference to specific calculation formulas and examples, which are described in detail below:
step 201: performing primary acquisition on Rayleigh scattering signals;
in practical application, according to the sampling theorem, the sampling rate f used in signal acquisitionsTypically the highest frequency f of the signalmThe component is 5-10 times, and a three-channel signal acquisition mode is adopted in the embodiment of the invention. The embodiment of the invention respectively uses 0.2f for Rayleigh scattering signalss、0.5fs、fsDifferent sampling rates, fsThe three paths of collected Rayleigh scattering curves x are obtained by the self setting of a user1(t)、x2(t)、x3(t)。
Step 202: noise signals are often superposed on target signals in a high-frequency component mode, so that the primarily acquired Rayleigh scattering signals are subjected to primary filtering;
in the embodiment of the invention, the low-pass filtering parameter is set to be 0.1, and the cutoff frequencies of three paths of Rayleigh scattering signals are respectively 0.02fs、0.05fs、0.1fs。
Step 203: completing the initial acquisition and the initial filtering of the Rayleigh scattering signals through the step 201 and the step 202, and performing data alignment operation of sample point supplement on the primarily processed Rayleigh scattering signals;
wherein the step is to obtain the Rayleigh scattering signal x3Number of sampling points n of (t)3For another two paths of Rayleigh scattering signals x as reference1(t)、x2(t) is divided intoSeparately complementing the sampling point on the Rayleigh scattering signal x1(t) supplementing the same value as the previous sample between adjacent samples to obtain a Rayleigh scattering signal x2(t) the adjacent samples are complemented by the same value as the previous sample. Obtaining three paths of aligned Rayleigh scattering signals X after data alignment1(t)、X2(t)、X3(t)。
In practical applications, data alignment is an operation in signal acquisition for different sampling rates, and aims to process data at the same sampling rate. There are several ways of data alignment, affecting the detailed characteristics of the signal.
Step 204: setting the merge weighting parameter, X in this example1(t)、X2(t)、X3(t) weighting factor l1、l2、l30.2, 0.5 and 0.7 respectively;
wherein, the three paths of Rayleigh scattering signals X obtained in the step 204 are combined according to 205-1(t)、X2(t)、X3(t) are, respectively:
step 205: point-by-point merging X1(t)、X2(t) the combined formula is
Figure BDA0003522823510000061
Step 206: point-by-point merging X2(t)、X3(t) the combined formula is
Figure BDA0003522823510000062
Step 207: point-by-point merging X3(t)、X1(t) the combined formula is
Figure BDA0003522823510000063
Step 208: for three paths of weighted signals
Figure BDA0003522823510000064
Point-by-point combination is carried out to obtain a preprocessed Rayleigh scattering curve x (t) with a combination formula
Figure BDA0003522823510000065
And finishing the acquisition and initialization of the Rayleigh scattering signals.
Step 209: smoothing a curve;
setting a smoothing operator sigma1And σ2. The parameter value of the smoothing operator is obtained according to the following expression:
σ1＝{σ1i}＝k{-(i-α)2+b},σ2＝{σ2i}＝k{|(α-i)3|+b}
wherein σ1And σ2The one-dimensional smoothing operators comprise odd elements, the middle elements of the smoothing operators are used as the center of the template, and the number of the specific elements in the operators is set by a user.
Wherein σ1iRepresenting the first smoothing operator σ1Value of each element in (a)2iRepresenting the second smoothing operator σ2The value of each element in the Chinese character is obtained; k is a gain coefficient, which is a real number greater than 0; i represents the ith element on the smoothing operator, the minimum value is 1, and the maximum value is the total number of elements in the operator; alpha and b are operator smoothing direction adjusting constants which are set by a user to meet different smoothing requirements.
In this example, the smoothing operator σ is set1Is a 1 × 3 template, the parameters are k ═ 1, α ═ 2, b ═ 3, and the obtained σ is1＝[1,2,1](ii) a Smoothing operator sigma2Is a 1 × 5 template, the parameters of the template have values of k ═ 1, α ═ 3, and b ═ 6, and the obtained σ is2＝[2,5,6,5,2]。
Step 210: with the first smoothing operator σ1Center σ of (a)12Traversing the sampling points on the whole Rayleigh scattering curve from the beginning to the end of the Rayleigh scattering curve x (t) for the starting point, and if the template element sigma is11Or σ13When data points are lacked under the coverage, zero filling calculation is carried out to obtain the upper sigma of x (t)12Corresponding sampling point is subjected to a first smoothing operator sigma1And taking the smoothed value, wherein the smoothed value of the template center coverage data point is as follows:
Figure BDA0003522823510000071
in the formula, xjRepresenting the smoothing operator σ1Covering the sampling points of the lower Rayleigh scattering curve x (t) when the operator σ is smoothed1When the Rayleigh scattering curve is traversed, a smoothed Rayleigh scattering curve L is obtained1。
Step 211: with the second smoothing operator σ2Center σ of (a)23Moving the starting point from the head end to the tail end of the Rayleigh scattering curve x (t) to traverse the sampling points on the whole curve if the template element sigma21、σ22Or σ24、σ25When data points are lacked under the coverage, zero filling calculation is carried out to obtain the upper sigma of x (t)23Corresponding sample point is subjected to second smoothing operator sigma2And taking the smoothed value, wherein the smoothed value of the template center coverage data point is as follows:
Figure BDA0003522823510000072
in the formula, xjRepresenting the smoothing operator σ2Covering the sampling points of the lower Rayleigh scattering curve x (t) when the operator σ is smoothed2Obtaining a smoothed Rayleigh scattering curve L after traversing the Rayleigh scattering curve2。
The process of traversing and zero padding steps 210 and 211 is further described below in conjunction with fig. 3, as follows: let the first smoothing operator σ1Center σ of (a)12Traversing the sampling points on the whole curve from the head end to the tail end of the Rayleigh scattering curve x (t), obtaining the smoothed values of the corresponding sampling points according to the calculation formula in the step 210, and obtaining a smoothed curve L1. When the center of the smoothing operator is sigma12Covering Rayleigh scattering curve head end sampling point x1At (t), template element σ11No data points below, this time for σ11Lower zero-filling calculation sampling point x1(t) smoothed values; when the center of the smoothing operator is sigma12Covering Rayleigh scattering curve end sampling point xn(t) template element σ13No data points below, this time forσ13Lower zero-filling calculation sampling point xn(t) smoothed values.
In the same way, let the second smoothing operator σ2Center σ of (a)23Traversing the sampling points on the whole curve from the head end to the tail end of the Rayleigh scattering curve x (t), obtaining the smoothed values of the corresponding sampling points according to the calculation formula 211 in the step, and obtaining a smoothed curve L2. When the center of the smoothing operator is sigma23Covering Rayleigh scattering curve head end sampling point x1(t) template element σ21、σ22No data point below; when the center of the smoothing operator is sigma23Traverse to sample point x2At (t), template element σ21No data point below; when the center of the smoothing operator is sigma23Traverse to sample point xn-1At (t), template element σ25No data point below; when the center of the smoothing operator is sigma23Traverse to the end sample point xnAt (t), template element σ24、σ25There are no data points below. The above-mentioned cases are all zero-filling calculation at the corresponding position of the template element.
Step 212: for the smoothed Rayleigh scattering curve L1And L2Point-by-point combination, the combination formula is
Figure BDA0003522823510000081
Obtaining a combined Rayleigh scattering curve K;
and all the Rayleigh scattering curves K obtained in the step form the space-time diagram within the space-time diagram updating time interval.
Step 213: fitting a new curve;
and selecting n Rayleigh scattering curves in the time interval for updating the space-time diagram, and fitting two adjacent curves to construct a new Rayleigh scattering curve so as to strengthen the detail distribution of the space-time diagram. Starting from the curve 1, a new curve K' is fitted point by point between two adjacent curves. The fitting formula is:
Figure BDA0003522823510000082
i＝1,2,……n-1
in the formula, KijExpress RuiEdge scattering curve Ki2n-1 Rayleigh scattering curves are obtained in total.
Step 214: splicing the 2n-1 Rayleigh scattering curves in the step 213 into a space-time diagram, and marking the initial space-time diagram as P1；
Step 215: initial space-time diagram P with 1 x 5 template pair1Performing first filtering;
wherein the steps are as follows: neglecting the elements within the pixel point of the element 2 at the boundary, the center of the template is from the initial space-time diagram P1The origin is shifted in the positive direction along the time axis and the spatial axis. The new gray value calculation formula of the element under the template center coverage is as follows:
Figure BDA0003522823510000083
wherein P isjRepresenting the gray value of the pixel covered by the template, traversing the initial space-time diagram P1After all the pixel points, obtaining a filtered space-time diagram P2。
Step 216: initial space-time diagram P with 3 x 3 template pair1Filtering for the second time, neglecting the elements within the element 2 pixel point at the boundary, and enabling the center of the template to be self-initiated to the space-time diagram P1The origin is shifted positively along the time and spatial axes.
Wherein, the 3 × 3 template is:
Figure BDA0003522823510000091
specific parameter value satisfies
Figure BDA0003522823510000092
The new gray value of the element under the coverage of the center of the template is calculated by the formula
Figure BDA0003522823510000093
In the formula PijCovering the new gray value of the lower element for the template center, PxyRepresenting the gray value of the corresponding element of the space-time diagram under the coverage of the template. Initial value of sigma in this stepIs 0.5, and the filtered space-time diagram is marked as P31Represents a space-time diagram P1The result of the filtering after the first iteration through step 216.
Step 217: let σ be 0.6, 0.7, 0.8, 0.9, respectively, repeating step 216 for 4 times to obtain P32、P33、P34、P35。
Step 218: merging the filtered spatio-temporal patterns P of 5 iterations in steps 216, 21731、P32、P33、P34、P35Calculating the average value of the gray values of the five space-time diagrams at the same position point by point as the result of the second filtering to obtain a space-time diagram P3。
Step 219: for the filtered space-time diagram P in step 2152And the space-time diagram P in step 2183And (3) point-by-point combination to obtain a final space-time diagram P, wherein the combination formula is as follows:
Figure BDA0003522823510000094
in the formula, PijRepresenting the gray value, P, of the merged space-time diagram2ijRepresenting a space-time diagram P2Pixel point at the upper corresponding position, P3ijRepresenting a space-time diagram P3And the pixel points of the corresponding positions. Therefore, the construction of the space-time diagram is completed, the smooth denoising of the Rayleigh scattering curve signal and the image enhancement of the space-time diagram are completed, and the signal to noise ratio is improved.
In the embodiment of the present invention, except for the specific description of the model of each device, the model of other devices is not limited, as long as the device can perform the above functions.
Those skilled in the art will appreciate that the drawings are only schematic illustrations of preferred embodiments, and the above-described embodiments of the present invention are merely provided for description and do not represent the merits of the embodiments.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.

Claims (6)

1. A method for conditioning a phase-sensitive optical time domain reflectometer signal to improve signal-to-noise ratio and detail characteristics, the method comprising:
performing data alignment operation of sampling point supplement on the primarily processed Rayleigh scattering signals to obtain three paths of aligned Rayleigh scattering curve signals, and obtaining three paths of point-by-point combined Rayleigh scattering weighted signals according to weighting parameters; combining the three paths of Rayleigh scattering weighting signals point by point to obtain a preprocessed Rayleigh scattering curve x (t);
moving from the head end to the tail end of the Rayleigh scattering curve x (t) by taking the centers of the first and second smoothing operators as starting points, if the data points are lacked under the coverage of the center of the template, performing zero filling calculation, and obtaining the Rayleigh scattering curve L after smoothing when the first and second smoothing operators finish traversing x (t)1、L2；
Obtaining a smoothed Rayleigh scattering curve L1、L2Performing point-by-point combination on the Rayleigh scattering curves K, and fitting two adjacent Rayleigh scattering curves to construct a new Rayleigh scattering curve, so as to obtain 2n-1 Rayleigh scattering curves; splicing 2n-1 Rayleigh scattering curves into a space-time diagram, and marking the initial space-time diagram as P1；
Initial space-time diagram P with 1 x 5 template pair1Filtering to obtain filtered space-time diagram P2Using a 3 × 3 template to pair the initial space-time diagram P1Filtering, namely updating the 3 x 3 template to realize filtering for a plurality of times to obtain space-time diagrams with different characteristics;
merging the filtered space-time diagrams corresponding to the 3 multiplied by 3 templates, and calculating the mean value point by point of the gray values of the space-time diagrams at the same position as the result of the second filtering to obtain a space-time diagram P3(ii) a To time-space diagram P2And space-time diagram P3And combining point by point to obtain a final space-time diagram P.
2. The method of claim 1, further comprising the steps of:
primarily collecting the Rayleigh scattering signals by adopting a three-channel signal collection mode to obtain three paths of Rayleigh scattering curve signals; and performing primary filtering on the three paths of Rayleigh scattering curve signals by adopting different cut-off frequencies.
3. The method for conditioning the signal of the phase-sensitive optical time domain reflectometer according to claim 1, wherein the obtaining of the point-by-point combined rayleigh scattering weighted signal according to the weighting parameters specifically comprises:
point-by-point merging X1(t)、X2(t) the combined formula is
Figure FDA0003522823500000011
Point-by-point merging X2(t)、X3(t) the combined formula is
Figure FDA0003522823500000012
Point-by-point merging X3(t)、X1(t) the combined formula is
Figure FDA0003522823500000021
Wherein l1、l2、l3As a weighting factor, X1(t)、X2(t)、X3And (t) three paths of aligned Rayleigh scattering signals.
4. The method as claimed in claim 1, wherein the first and second smoothing operators are:
σ1＝{σ1i}＝k{-(i-α)2+b},σ2＝{σ2i}＝k{|(α-i)3|+b}
wherein σ1iRepresenting the first smoothing operator σ1Value of each element in (a)2iRepresenting the second smoothing operator σ2Each ofTaking values of elements; k is a gain coefficient; i represents the ith element on the smoothing operator; alpha and b are operator smoothing direction adjustment constants.
5. The method for conditioning signal of phase-sensitive optical time domain reflectometer according to claim 1, wherein the 3 x 3 template is:
Figure FDA0003522823500000022
wherein the content of the first and second substances,
Figure FDA0003522823500000023
6. the method as claimed in claim 1, wherein the time-space diagram P is a time-domain reflectometer signal conditioning method with improved signal-to-noise ratio and detail feature2And space-time diagram P3Point-by-point combination is carried out, and the final space-time diagram P is obtained as follows:
Figure FDA0003522823500000024
in the formula, PijRepresenting the gray value, P, of the merged space-time diagram2ijRepresenting a space-time diagram P2Pixel point of upper corresponding position, P3ijRepresenting a space-time diagram P3And the pixel points of the corresponding positions.
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