CN112611444A - Distributed optical fiber vibration monitoring system and method capable of achieving accurate positioning - Google Patents
Distributed optical fiber vibration monitoring system and method capable of achieving accurate positioning Download PDFInfo
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- CN112611444A CN112611444A CN202011611765.0A CN202011611765A CN112611444A CN 112611444 A CN112611444 A CN 112611444A CN 202011611765 A CN202011611765 A CN 202011611765A CN 112611444 A CN112611444 A CN 112611444A
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- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
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Abstract
The invention provides a distributed optical fiber vibration monitoring system and method capable of accurately positioning, and solves the problems of low positioning accuracy, high false alarm rate and poor sensitivity of an interference event of the conventional distributed optical fiber vibration monitoring system. The method comprises the following steps: 1) obtaining interference signal D of backward Rayleigh scattering lightn(t); 2) interference signal D to backward Rayleigh scattering lightn(t) performing butterworth filtering; 3) the signal F after filtering the Butterworth filtern(t) carrying out time signal difference and space signal difference processing to obtain a signal X (t) after difference; 4) performing wavelet decomposition and reconstruction on X (t), and determining and selecting the minimum noise amplitude value RqAnd outputs the corresponding reconstruction result as Mq(ii) a 5) To the reconstructed result MqAnd each signal value is compared with a set value, and the output signal value is greater than the position corresponding to the set value, wherein the position is the specific position where the vibration event occurs.
Description
Technical Field
The invention relates to a distributed optical fiber vibration monitoring technology, in particular to a distributed optical fiber vibration monitoring system and method capable of accurately positioning.
Background
With the continuous development of the optical communication industry, the application field of the optical fiber sensing technology is more and more extensive. Unlike conventional sensing techniques, fiber optic sensing is a novel sensor technique that receives and processes optical signals transmitted back through an optical fiber, and resolves information sensed by the optical fiber, such as temperature, pressure, flow, displacement, vibration, etc. The optical fiber sensing system has the advantages of no electromagnetic interference, strong environment adaptability, high safety, low energy consumption and the like. In recent years, a phase-sensitive optical time domain reflection distributed optical fiber vibration monitoring system based on Rayleigh scattering has good application in the fields of security protection, railway, tunnel, pipeline monitoring and the like, and the specific position of an interference event is positioned and alarmed by analyzing the interference result change of backward Rayleigh scattering light returned from an optical fiber.
Due to the influence of photoelectric devices, system stray light and white noise, the existing distributed optical fiber vibration monitoring system generally has the problems of low interference event positioning precision, high false alarm rate, poor sensitivity and the like.
Disclosure of Invention
The invention provides a distributed optical fiber vibration monitoring system and method capable of accurately positioning, and aims to solve the technical problems of low interference event positioning accuracy, high false alarm rate and poor sensitivity of the conventional distributed optical fiber vibration monitoring system.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a distributed optical fiber vibration monitoring system capable of being accurately positioned is characterized in that: the system comprises a distributed optical fiber vibration monitoring sensing unit and a data processing and analyzing unit;
the distributed optical fiber vibration monitoring sensing unit comprises a laser, a photoelectric modulator, an optical fiber amplifier, an optical fiber circulator, a single-mode optical fiber, a case, a photoelectric detector and a data acquisition module,
the photoelectric modulator, the optical fiber amplifier, the optical fiber circulator and the single-mode optical fiber are sequentially arranged along the emergent direction of the laser, one section of the single-mode optical fiber, which is close to the optical fiber circulator, is positioned in the case, and the other sections of the single-mode optical fiber are positioned outside the case;
the single-mode optical fiber is used for generating Rayleigh scattered light signals;
the photoelectric detector is used for performing photoelectric conversion on backward Rayleigh scattering optical signals transmitted back by the single-mode optical fiber and the optical fiber circulator;
the data acquisition module is used for acquiring the backward Rayleigh scattering light signals after photoelectric conversion and acquiring backward Rayleigh scattering light interference signals;
the data processing and analyzing unit is used for processing the backward Rayleigh scattering light interference signals and outputting specific positions of the vibration events so as to realize the accurate positioning of the vibration events.
Further, the optical fiber amplifier is an erbium-doped optical fiber amplifier;
the laser is an ultra-narrow linewidth laser.
Meanwhile, the invention also provides a distributed optical fiber vibration monitoring method capable of accurately positioning, which is characterized by comprising the following steps of:
1) obtaining interference signal D of backward Rayleigh scattering lightn(t)
Distributed optical fiber vibration monitoring sensing unit for acquiring backward Rayleigh scattering light interference signal Dn(t); wherein n represents a sampling point, and t represents a sampling moment;
2) interference signal D to backward Rayleigh scattering lightn(t) performing butterworth filtering
2.1) determining a Butterworth filter model H(s) according to the filter order N, the low-pass frequency and the sampling frequency value:
wherein s represents a domain;
2.2) converting the Butterworth filter model H(s) into H (z) according to a bilinear transformation method, and determining a denominator a (i) and a numerator b (i) in the function H (z);
wherein, i is the serial number of the filter coefficient, and i is 1.2.3 … … N;
2.3) mixing Dn(t), a (i), b (i) are substituted into the iterative equation to obtain the signal F filtered by the Butterworth filtern(t)：
3) Differential processing
The signal F after filtering the Butterworth filtern(t) carrying out time signal difference and space signal difference processing to obtain a signal X (t) after difference;
4) wavelet decomposition and reconstruction of X (t)
4.1) selecting m different wavelet bases, and marking all the wavelet bases as AjJ is 1,2,3 … m, and m is an integer of 8-40;
4.2) determining the decomposition layer number of each wavelet base, wherein the layer number is 2-5;
4.3) decomposing the corresponding layer number of the signal X (t) by utilizing each wavelet base;
4.4) performing wavelet reconstruction on the low-frequency part of the decomposed signal X (t) to obtain M wavelet basis reconstruction results, and recording all the wavelet basis reconstruction results as Mj；
4.5) calculating the reconstruction result M for each wavelet basis according to the following formulajNoise amplitude average value R ofj：
In the formula: q is the number of signal samples, and the head end of the single mode fiber in the chassis is selected for sampling, Mj(i) Constructing results M for wavelet basisjThe signal value corresponding to the corresponding sampling point in the time sequence;
4.6) selecting the minimum noise amplitude RqThe method comprises the following steps:
Rq＝min(R1，R2，R3，...Rm)
4.7) according to the minimum noise amplitude RqOutputting the corresponding reconstruction result as Mq；
5) Outputting the result
To the reconstructed result MqEach signal value is compared with a set value, and the output signal value is greater than the position corresponding to the set value, wherein the position is the specific position of the vibration event;
wherein the set value is the minimum noise amplitude RqMultiplying the set threshold。
Further, in step 4.1), m is 20, and 20 wavelet bases are 13 in db02, db03 and … … db14 and 7 in sym02 and sym03 … … sym08 respectively.
Further, in step 4.2), the number of layers is 3.
Further, the step 3) is specifically as follows:
3.1) Butterworth Filter filtered Signal Fn(t) time signal differencing to obtain a time-differentiated signal T (t):
T(t)＝Fn+1(t)-Fn(t)
3.2) performing spatial signal difference on the time-difference signal T (t) to obtain a spatially-difference signal X (t):
X(t)＝T(t+1)-T(t)。
further, the step 1) is specifically as follows:
1.1) the light beam emitted by the laser is modulated into pulse light by a photoelectric modulator, and enters a single mode fiber after passing through a fiber amplifier and a fiber circulator;
1.2) the single mode fiber generates Rayleigh scattering, and backward Rayleigh scattering light signals returned by the single mode fiber and the fiber circulator are collected by a photoelectric detector;
1.3) the photoelectric detector carries out photoelectric conversion on the collected backward Rayleigh scattered light signals and obtains backward Rayleigh scattered light interference signals D through the data collection modulen(t); wherein n represents time, and t represents a sampling point;
further, in step 4.5), q is 100.
Compared with the prior art, the invention has the advantages that:
1. the invention firstly compares the signal Dn(t) filtering to remove part of white noise and improve the signal-to-noise ratio of the system; secondly, the filtered data is subjected to signal difference processing twice, white noise is eliminated, the signal-to-noise ratio of the system is further improved, then, the signal is subjected to wavelet decomposition, wavelet reconstruction is carried out on a low-frequency part, the optimal signal-to-noise ratio is extracted by comparing various wavelet bases, the accurate positioning characteristic of the system is optimized, and the specific position of the vibration event can be accurately determined(ii) a And finally, selecting a threshold value and outputting a result.
2. The section of the single-mode fiber close to the fiber circulator is positioned in the case, and the signal of the single-mode fiber in the case is taken as a noise signal, so that the accuracy of noise amplitude calculation is improved, the positioning precision of a system for judging a vibration event is improved, the false alarm rate is reduced, and the sensitivity of the system is improved.
Drawings
FIG. 1 is a schematic structural diagram of a distributed optical fiber vibration monitoring system capable of being accurately positioned according to the present invention;
FIG. 2 is a schematic flow chart of a distributed optical fiber vibration monitoring method for precise positioning according to the present invention;
FIG. 3 is a schematic diagram of wavelet decomposition and reconstruction processes in the distributed optical fiber vibration monitoring method capable of accurately positioning according to the present invention;
FIG. 4 is a schematic diagram of the result of 3-layer wavelet decomposition performed on a signal X (t) in the distributed optical fiber vibration monitoring method capable of accurately positioning according to the present invention;
wherein the reference numbers are as follows:
the system comprises a laser 1, a photoelectric modulator 2, an optical fiber amplifier 3, an optical fiber circulator 4, a photoelectric detector 5, a data acquisition module 6, a data processing and analyzing unit 7, a single-mode optical fiber 8, a standard optical fiber section 81, a field optical fiber section 82 and a case 9.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
As shown in fig. 1, a distributed optical fiber vibration monitoring system capable of accurately positioning includes a distributed optical fiber vibration monitoring and sensing unit and a data processing and analyzing unit 7, wherein the distributed optical fiber vibration monitoring and sensing unit obtains a backward rayleigh scattering light interference result based on backward rayleigh scattering, the data processing and analyzing unit 7 calculates and processes the backward rayleigh scattering light interference result, and outputs a specific position of an event, thereby realizing accurate positioning of a vibration event.
The distributed optical fiber vibration monitoring sensing unit comprises a laser 1, a photoelectric modulator 2, an optical fiber amplifier 3, an optical fiber circulator 4, a single-mode optical fiber 8, a case 9, a photoelectric detector 5 and a data acquisition module 6, wherein one section of the single-mode optical fiber 8 is positioned in the case 9 and is used as a standard optical fiber section 81, and the other section of the single-mode optical fiber is positioned outside the case 9 and is used as a field optical fiber section 82; in this embodiment, the laser 1 is an ultra narrow linewidth laser, and the fiber amplifier 3 is an erbium-doped fiber amplifier.
Ultra-narrow linewidth laser 1 emits line-width extremely-narrow continuous light (linewidth 3KHz), which is modulated into pulse light by photoelectric modulator 2(SOA modulation), and then enters single-mode fiber 8 through fiber amplifier 3 and fiber circulator 4, Rayleigh scattering occurs at each position in single-mode fiber 8, wherein, backward Rayleigh scattering light interference result passes through single-mode fiber 8, fiber circulator 4 returns to photoelectric detector 5, photoelectric detector 5 performs photoelectric conversion on collected backward Rayleigh scattering light signals, and backward Rayleigh scattering light interference signal D is acquired by data acquisition module 6n(t)。
Based on the distributed optical fiber vibration monitoring system capable of accurately positioning, the embodiment provides a distributed optical fiber vibration monitoring method capable of accurately positioning, and an original signal D is firstly subjected ton(t) performing filtering processing; secondly, performing signal differential processing twice on the filtered data; thirdly, performing wavelet decomposition on the signal, filtering out a high-frequency part in the signal, performing wavelet reconstruction on a low-frequency part, comparing various wavelet bases, preferably selecting the wavelet bases, refining the optimal signal-to-noise ratio, and optimizing the accurate positioning characteristic of the system; finally, threshold selection is performed and a result is output, as shown in fig. 2, the detection method specifically includes the following steps:
1) obtaining interference signal D of backward Rayleigh scattering lightn(t)
1.1) emitting continuous light with extremely narrow line width by an ultra-narrow line width laser 1, modulating the continuous light into pulse light by a photoelectric modulator 2, and entering a single mode fiber 8 after passing through a fiber amplifier 3 and a fiber circulator 4;
1.2) the single mode fiber 8 generates Rayleigh scattering, and backward Rayleigh scattering light signals returned by the single mode fiber 8 and the fiber circulator 4 are collected by the photoelectric detector 5;
1.3) the photoelectric detector 5 carries out photoelectric conversion on the collected backward Rayleigh scattered light signals and obtains the backward Rayleigh scattered light through the data collection module 6Optical interference signal Dn(t); wherein n represents a sampling point, and t represents a sampling moment;
2) for signal Dn(t) performing Butterworth filtering and performing preliminary filtering processing on system white noise
2.1) determining the filter order N, the low-pass frequency fcSampling frequency f, and according to N, fcF, determining the Butterworth filter model H(s):
wherein s represents a domain;
2.2) converting the Butterworth filter model H(s) into H (z) according to a bilinear transformation method, and determining a denominator a (i) and a numerator b (i) in the function H (z);
wherein, i is the serial number of the filter coefficient, and i is 1.2.3 … … N;
2.3) mixing DnSubstituting (t), a (i), b (i) into the iterative equation to solve the signal F filtered by the Butterworth filtern(t)：
3) Differential processing
3.1) Butterworth Filter filtered Signal Fn(t) carrying out time signal difference to improve the signal-to-noise ratio of the system, and obtaining a signal T (t) after the time difference:
T(t)＝Fn+1(t)-Fn(t)
3.2) carrying out spatial signal difference on the signals T (t) after the time difference, further improving the signal-to-noise ratio of the system, and obtaining signals X (t) after the spatial difference:
X(t)＝T(t+1)-T(t)。
4) wavelet decomposition and reconstruction of X (t)
4.1) As shown in FIG. 3, m different wavelet bases are selected, and all wavelet bases are marked as AjJ is 1,2,3 … m, and m is an integer of 8-40; the true bookIn the embodiment, m is preferably 20, 20 wavelets are respectively db02, db03, db04, db05, db06, db07, db08, db09, db10, db11, db12, db13 and db14, and sym02, sym03, sym04, sym05, sym06, sym07 and sym08, and 20 wavelets are respectively marked as A02, db03, db04, db03, db12, db13 and 20 wavelets are respectively marked as A, and1、A2、……A20；
4.2) determining the decomposition layer number of each wavelet base, wherein the layer number is 2-5, and the decomposition layer number of the wavelet base is 3 in the embodiment;
4.3) decomposing the signal X (t) by using each wavelet basis according to the corresponding layer number, wherein the decomposition structure diagram of the signal X (t) is shown in FIG. 4;
4.4) removing the wavelet decomposition high-frequency part, performing wavelet reconstruction by using the low-frequency part CD3 of the decomposed signal X (t), and obtaining 20 wavelet basis reconstruction results, wherein all the wavelet basis reconstruction results are marked as Mj，(j＝1,2,3…20)；
4.5) taking the signal of the single mode fiber 8 in the case 9 as a noise signal, calculating the average value of the noise amplitude, and specifically calculating the reconstruction result M of each wavelet basis according to the following formulajNoise amplitude average value R ofj：
In the formula: q is the signal sampling number, and the head end of the standard optical fiber section 81 in the case 9 is selected, in this embodiment, q is 100, and M isj(i) Constructing results M for wavelet basisjThe signal value corresponding to the corresponding sampling point in the time sequence;
4.6) constructing the result M from all the calculated wavelet basisjNoise amplitude average value R ofjAverage value R for all noise amplitudesjPreferably selecting the minimum noise amplitude Rq：
Rq＝min(R1，R2，R3，...R20)
4.7) according to the minimum noise amplitude RqOutputting a corresponding reconstruction result as M (t) Mq；
5) Outputting the result
Let the reconstruction result MqWherein the set of all signals is represented by { (A)1,B1),(A2,B2),…,(AN,BN)}，A1、A2……ANDenotes the position coordinates, B1、B2……BNSignal magnitude indicating the corresponding position coordinates by pair B1、B2……BNIs compared with a set value, the set value is the minimum noise amplitude value RqAnd multiplying the signal value by a set threshold value, and if the signal value is greater than the set value, outputting a position corresponding to the signal value, wherein the position is the specific position where the vibration event occurs.
In the method, partial white noise can be filtered by adopting the butterworth filtering preliminary treatment, the signal-to-noise ratio of the system is improved, and then the white noise is eliminated by adopting the time difference and the position difference, so that the signal-to-noise ratio of the system is further improved; and the specific position of the vibration event can be accurately determined by decomposing the signal wavelet, preferably selecting the wavelet basis and refining the optimal signal-to-noise ratio of the system.
The above description is only for the purpose of describing the preferred embodiments of the present invention and does not limit the technical solutions of the present invention, and any known modifications made by those skilled in the art based on the main technical concepts of the present invention fall within the technical scope of the present invention.
Claims (8)
1. The utility model provides a but distributed optical fiber vibration monitoring system of accurate positioning which characterized in that: the system comprises a distributed optical fiber vibration monitoring and sensing unit and a data processing and analyzing unit (7);
the distributed optical fiber vibration monitoring sensing unit comprises a laser (1), a photoelectric modulator (2), an optical fiber amplifier (3), an optical fiber circulator (4), a single-mode optical fiber (8), a case (9), a photoelectric detector (5) and a data acquisition module (6);
the photoelectric modulator (2), the optical fiber amplifier (3), the optical fiber circulator (4) and the single-mode optical fiber (8) are sequentially arranged along the emergent direction of the laser (1), one section of the single-mode optical fiber (8) close to the optical fiber circulator (4) is positioned in the case (9), and the rest sections are positioned outside the case (9);
the single-mode optical fiber (8) is used for generating Rayleigh scattered light signals;
the photoelectric detector (5) is used for performing photoelectric conversion on backward Rayleigh scattering optical signals transmitted back through the single-mode optical fiber (8) and the optical fiber circulator (4);
the data acquisition module (6) is used for acquiring backward Rayleigh scattered light signals after photoelectric conversion to acquire backward Rayleigh scattered light interference signals;
and the data processing and analyzing unit (7) is used for processing the backward Rayleigh scattering light interference signals and outputting specific positions of the vibration events.
2. The precisely positionable distributed fiber optic vibration monitoring system of claim 1, wherein: the optical fiber amplifier (3) is an erbium-doped optical fiber amplifier;
the laser (1) is an ultra-narrow linewidth laser.
3. A distributed optical fiber vibration monitoring method capable of being accurately positioned is characterized by comprising the following steps:
1) obtaining interference signal D of backward Rayleigh scattering lightn(t)
Distributed optical fiber vibration monitoring sensing unit for acquiring backward Rayleigh scattering light interference signal Dn(t); wherein n represents a sampling point, and t represents a sampling moment;
2) interference signal D to backward Rayleigh scattering lightn(t) performing butterworth filtering
2.1) determining a Butterworth filter model H(s) according to the filter order N, the low-pass frequency and the sampling frequency value:
wherein s represents a domain;
2.2) converting the Butterworth filter model H(s) into H (z) according to a bilinear transformation method, and determining a denominator a (i) and a numerator b (i) in the function H (z);
wherein, i is the serial number of the filter coefficient, and i is 1.2.3 … … N;
2.3) mixing Dn(t), a (i), b (i) are substituted into the iterative equation to obtain the signal F filtered by the Butterworth filtern(t)：
3) Differential processing
The signal F after filtering the Butterworth filtern(t) carrying out time signal difference and space signal difference processing to obtain a signal X (t) after difference;
4) wavelet decomposition and reconstruction of X (t)
4.1) selecting m different wavelet bases, and marking all the wavelet bases as AjJ is 1,2,3 … m, and m is an integer of 8-40;
4.2) determining the decomposition layer number of each wavelet base, wherein the layer number is 2-5;
4.3) decomposing the corresponding layer number of the signal X (t) by utilizing each wavelet base;
4.4) performing wavelet reconstruction on the low-frequency part of the decomposed signal X (t) to obtain M wavelet basis reconstruction results, and recording all the wavelet basis reconstruction results as Mj；
4.5) calculating the reconstruction result M for each wavelet basis according to the following formulajNoise amplitude average value R ofj：
In the formula: q is the signal sampling number, and the head end of a single mode fiber (8) in the case (9) is selected for sampling, Mj(i) Constructing results M for wavelet basisjThe signal value corresponding to the corresponding sampling point in the time sequence;
4.6) selecting the minimum noise amplitude RqThe method comprises the following steps:
Rq＝min(R1，R2，R3，...Rm)
4.7) according to the minimum noise amplitude RqOutputting the corresponding reconstruction result as Mq；
5) Outputting the result
To the reconstructed result MqComparing each signal value with a set value, and outputting a position where the signal value is greater than the set value, wherein the position is a specific position where a vibration event occurs;
wherein the set value is the minimum noise amplitude RqMultiplying by a set threshold.
4. The distributed fiber optic vibration monitoring method of claim 3, wherein in step 4.1), m is 20, and 20 wavelet bases are db02, 13 in db03 and … … db14 and 7 in sym02 and sym03 … … sym 08.
5. The distributed fiber optic vibration monitoring method capable of being accurately positioned according to claim 4, wherein in step 4.2), the number of layers is 3.
6. The distributed optical fiber vibration monitoring method capable of being accurately positioned according to claim 3, 4 or 5, wherein the step 3) is specifically as follows:
3.1) Butterworth Filter filtered Signal Fn(t) time signal differencing to obtain a time-differentiated signal T (t):
T(t)＝Fn+1(t)-Fn(t)
3.2) performing spatial signal difference on the time-difference signal T (t) to obtain a spatially-difference signal X (t):
X(t)＝T(t+1)-T(t)。
7. the distributed optical fiber vibration monitoring method capable of being accurately positioned according to claim 6, wherein the step 1) is specifically as follows:
1.1) light beams emitted by a laser (1) are modulated into pulse light by a photoelectric modulator (2), and enter a single-mode optical fiber (8) after passing through an optical fiber amplifier (3) and an optical fiber circulator (4);
1.2) the single mode fiber (8) generates Rayleigh scattering, and backward Rayleigh scattering light signals returned by the single mode fiber (8) and the fiber circulator (4) are collected by a photoelectric detector (5);
1.3) the photoelectric detector (5) performs photoelectric conversion on the collected backward Rayleigh scattered light signals, and a data collection module (6) is used for acquiring backward Rayleigh scattered light interference signals Dn(t)。
8. The distributed fiber optic vibration monitoring method of claim 7, wherein in step 4.5), q is 100.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112857612A (en) * | 2021-04-14 | 2021-05-28 | 西安和其光电科技股份有限公司 | Distributed optical fiber temperature measurement calculation method and system |
| CN112857612B (en) * | 2021-04-14 | 2023-03-31 | 西安和其光电科技股份有限公司 | Distributed optical fiber temperature measurement calculation method |
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