CN117708506B - Method and system for eliminating deterioration effect caused by distributed acoustic wave sensing coherent fading - Google Patents
Method and system for eliminating deterioration effect caused by distributed acoustic wave sensing coherent fading Download PDFInfo
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- 230000006866 deterioration Effects 0.000 title claims abstract description 11
- 239000013307 optical fiber Substances 0.000 claims abstract description 77
- 238000012545 processing Methods 0.000 claims abstract description 68
- 238000009432 framing Methods 0.000 claims abstract description 55
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Abstract
The embodiment of the application provides a method and a system for eliminating a deterioration effect caused by distributed acoustic wave sensing coherent fading, which relate to the technical field of distributed optical fiber sensing detection and comprise the following steps: collecting backward Rayleigh scattering signals generated by vibration signals along the sensing optical fiber within a preset time period; acquiring first demodulation video-image time domain dynamic information; framing the first demodulated video-image time domain dynamic information along each position along the sensing optical fiber according to the time domain length to obtain a plurality of first framing static information; morphological technology processing is carried out on the first sub-frame static information to obtain corresponding second sub-frame static information so as to inhibit abnormal effects caused by coherent fading; and combining and reconstructing the plurality of second sub-frame processing information to obtain second demodulated video-image time domain dynamic information after the coherent fading effect is restrained. By the arrangement of the embodiment of the application, the method and the system which can restrain the coherent fading effect, reduce the measurement error and improve the measurement precision are provided.
Description
Technical Field
The application relates to the technical field of distributed optical fiber sensing detection, in particular to a method and a system for eliminating a deterioration effect caused by distributed acoustic wave sensing coherent fading.
Background
The optical fiber has strong electromagnetic interference resistance, good electrical insulation and light transmission characteristics. In recent years, distributed optical fiber sensing systems using optical fibers as sensing elements and signal transmission media have received increasing attention in national defense, military, civil facilities and the like. The distributed optical fiber sensing technology measures characteristic information along the optical fiber direction by detecting and analyzing optical effects in the optical fiber. The characteristic information of the optical fiber changes along with the changes of the external temperature, the strain and the vibration, so that the environmental parameters around the optical fiber can be perceived.
In the related art, the distributed optical fiber sensing technology mainly utilizes scattering effects in optical fibers, such as Rayleigh scattering, brillouin scattering and Raman scattering, to detect external information. The distributed optical fiber sensing system comprises a distributed optical fiber acoustic wave sensing system, a distributed optical fiber temperature sensing system and the like, wherein the distributed optical fiber acoustic wave sensing system utilizes the phase of Rayleigh scattered light instead of the light intensity to detect signals such as sound or vibration in an audio frequency range, not only can the magnitude of the phase amplitude be utilized to provide sound or vibration event intensity information, but also the linear quantitative measurement value is utilized to achieve the acquisition of the phase and frequency information of the sound or vibration event.
However, since the distributed optical fiber acoustic wave sensing system uses a high-coherence narrow-linewidth laser, and the refractive index is randomly changed along the optical fiber direction, the rayleigh scattering optical signals at various positions along the optical fiber can be affected by effects such as coherent fading, so that the backward rayleigh scattering light intensity of certain areas is sharply reduced, and is close to or even smaller than the background noise of the optical fiber sensing system, the serious degradation of the signal intensity can cause the inability to demodulate accurate phase information, and further cause positioning errors or signal distortion of demodulation results.
Disclosure of Invention
The embodiment of the application provides a method and a system for eliminating a deterioration effect caused by distributed acoustic wave sensing coherent fading, which are used for solving the technical problems that in the related art, due to the influence of coherent fading and other effects on Rayleigh scattering optical signals at various positions along an optical fiber, the backward Rayleigh scattering light intensity of certain areas is suddenly reduced and is close to or even smaller than the background noise of an optical fiber sensing system, the serious deterioration of the signal intensity can cause the incapability of demodulating accurate phase information, and further, the positioning error or signal distortion of a demodulation result is caused.
In a first aspect, an embodiment of the present application provides a method for eliminating a degradation effect caused by distributed acoustic wave sensing coherent fading, including:
Collecting backward Rayleigh scattering signals generated by vibration signals along the sensing optical fiber within a preset time period;
Acquiring first demodulation video-time domain dynamic information; the first demodulation video-time domain dynamic information is a time dynamic change image of the backward Rayleigh scattering signal at each position along the line of the sensing optical fiber, which is obtained after the backward Rayleigh scattering signal is initially demodulated;
Framing the first demodulated video-time domain dynamic information along each position along the sensing optical fiber according to the time domain length to obtain a plurality of framing static information;
carrying out morphological technical processing on the framing static information to obtain corresponding framing processing information so as to inhibit coherent fading effect;
Combining and reconstructing the plurality of frame processing information to obtain second demodulation video-image time domain dynamic information after inhibiting the coherent fading effect; the second demodulation video-image time domain dynamic information is dynamic change information after the backward Rayleigh scattering signals at all positions along the sensing optical fiber inhibit the coherent fading effect.
In a possible implementation manner, performing morphological technical processing on the sub-frame static information to obtain corresponding sub-frame processing information specifically includes the following steps:
defining a reference structural element as an operator of a primary scale, and expanding the structural element B i of the ith scale by the reference structural element B;
filtering the framing static information by adopting operators of each level of scale to obtain a plurality of filtering results respectively corresponding to the operators;
And combining the filtering results to obtain framing processing information.
In a possible implementation manner, the step of filtering the framing static information by adopting the operators of each stage of scale to obtain a plurality of filtering results respectively corresponding to the operators further includes:
carrying out frequency domain denoising on the framing static information to obtain a preset signal-to-noise ratio;
according to the filtering result and the framing static information, obtaining a filtering signal-to-noise ratio;
if the filtering signal-to-noise ratio is larger than the preset signal-to-noise ratio, expanding the reference structural element and then continuously filtering the sub-frame static information;
and if the filtering signal-to-noise ratio is smaller than the preset signal-to-noise ratio, obtaining a filtering result.
In one possible implementation, the formula for the framing process information I LL is:
；
Wherein I represents framing static information; b i represents a structural element operator of the ith scale obtained by expanding a group of reference structural elements; w i represents the setting of the weight parameters; an open operator for representing corrosion-before-expansion of the framing static information I; Representing an expansion operation; n represents the number of structural elements; i LL denotes the obtained framing processing information.
In one possible implementation, the calculation formula of the weight W i is:
；
wherein, Representing the size of structural element B i.
In a possible implementation manner, the step of performing morphological technical processing on the static information of the sub-frames to obtain corresponding sub-frame processing information so as to suppress the coherent fading effect further includes:
Calculating the ratio of an abnormal pixel value to an integral pixel value in the framing processing information, wherein the abnormal pixel value is a pixel of which the pixel value in the framing processing information is smaller than a preset pixel value;
combining and reconstructing frame processing information with the ratio of the abnormal pixel value to the integral pixel value smaller than a preset ratio to obtain corresponding frame processing information;
and continuing morphological technical processing on the framing processing information with the ratio of the abnormal pixel value to the integral pixel value being larger than the preset ratio.
In one possible implementation, before the step of obtaining the first demodulated video-time domain dynamic information, further comprises:
and filtering and preprocessing the backward Rayleigh scattering signals to filter the backward Rayleigh scattering signals outside the preset frequency.
In one possible implementation, the obtaining the first demodulated video-time domain dynamic information specifically includes the steps of:
Demodulating the backward Rayleigh scattering signal to obtain first demodulation information; the first demodulation information comprises demodulation information containing noise information at each position along the sensing optical fiber;
And constructing first demodulation video-time domain dynamic information according to the first demodulation information.
In a second aspect, an embodiment of the present application further provides a distributed acoustic wave sensing system, where the method for suppressing coherent fading applied to the distributed acoustic wave sensing system in any one of the first aspect is adopted;
the system comprises a demodulation unit and a control unit, wherein the demodulation unit and the control unit are connected through signals;
The demodulation unit is configured to collect backward Rayleigh scattering signals generated by vibration signals in the line of the sensing optical fiber within a preset time period;
The demodulation unit is configured to acquire first demodulated video-time domain dynamic information; the first demodulation video-time domain dynamic information is a time dynamic change image of the backward Rayleigh scattering signal at each position along the line of the sensing optical fiber, which is obtained after the backward Rayleigh scattering signal is initially demodulated;
The control unit is configured to frame the first demodulation video-time domain dynamic information along each position along the sensing optical fiber according to the time domain length to obtain a plurality of frame static information;
The control unit is configured to perform morphological technical processing on the static information of the sub-frames to obtain corresponding sub-frame processing information so as to inhibit the coherent fading effect;
The control unit is configured to combine and reconstruct the plurality of frame processing information to obtain second demodulated video-image time domain dynamic information after the coherent fading effect is restrained; the second demodulation video-image time domain dynamic information is dynamic change information after the backward Rayleigh scattering signals at all positions along the sensing optical fiber inhibit the coherent fading effect.
In a first aspect, an embodiment of the present application provides a method for eliminating a degradation effect caused by distributed acoustic wave sensing coherent fading, where the embodiment of the present application demodulates a backward rayleigh scattering signal to obtain first demodulated video-time domain dynamic information, frames the first demodulated video-time domain dynamic information along each position along a sensing optical fiber according to a time domain length to obtain a plurality of frame-division static information, and performs morphological processing on the frame-division static information to obtain frame-division processing information, where the frame-division static information is subjected to morphological processing to suppress a coherent fading suppression effect, and then combines and reconstructs a plurality of frame-division processing information to obtain second demodulated video-image time domain dynamic information after suppressing the coherent fading effect, that is, a dynamic change image after suppressing the coherent fading effect by the backward rayleigh scattering signal at each position along the sensing optical fiber, thereby avoiding the coherent fading effect, reducing a measurement error, and improving a measurement accuracy of the distributed acoustic wave sensing system.
In a second aspect, an embodiment of the present application provides a distributed acoustic wave sensing system, which adopts the method for suppressing coherent fading in any one of the above schemes, so that all the beneficial effects of the method for suppressing coherent fading in any one of the above schemes are provided, and are not repeated herein.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:
FIG. 1 is a schematic diagram of a distributed acoustic wave sensor system according to an embodiment of the present application;
FIG. 2 is a method step diagram of a method for eliminating degradation effects caused by distributed acoustic wave sensing coherent fading according to an embodiment of the present application;
Fig. 3 is a specific step diagram of S400 in fig. 2.
Reference numerals illustrate:
1-a laser emitting unit; a 2-sensing unit; a 3-demodulation unit;
a 101-laser; 102-an isolator; 103-an acousto-optic modulator; 104-a first erbium-doped fiber amplifier;
201-a circulator; 202-sensing optical fibers; 203-piezoelectric ceramic;
301-a second erbium-doped fiber amplifier; 302-a first coupler; 303-a second coupler; 304-a photodetector; 304 a-a first photodetector; 304 b-a second photodetector; 304 c-a third photodetector; 305-acquisition card.
Detailed Description
In order to make the technical solution of the present application better understood by those skilled in the art, the technical solution of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, shall fall within the scope of the present application.
It should be noted that in the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than as described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.
The optical fiber has strong electromagnetic interference resistance, good electrical insulation and light transmission characteristics. In recent years, distributed optical fiber sensing systems using optical fibers as sensing elements and signal transmission media have received increasing attention in national defense, military, civil facilities and the like. The distributed optical fiber sensing technology measures characteristic information along the optical fiber direction by detecting and analyzing optical effects in the optical fiber. The characteristic information of the optical fiber changes along with the changes of the external temperature, the strain and the vibration, so that the environmental parameters around the optical fiber can be perceived.
In the related art, the distributed optical fiber sensing technology mainly utilizes scattering effects in optical fibers, such as Rayleigh scattering, brillouin scattering and Raman scattering, to detect external information. The distributed optical fiber sensing system comprises a distributed optical fiber acoustic wave sensing system, a distributed optical fiber temperature sensing system and the like, wherein the distributed optical fiber acoustic wave sensing system utilizes the phase of Rayleigh scattered light instead of the light intensity to detect signals such as sound or vibration in an audio frequency range, not only can the magnitude of the phase amplitude be utilized to provide sound or vibration event intensity information, but also the linear quantitative measurement value is utilized to achieve the acquisition of the phase and frequency information of the sound or vibration event.
However, since the distributed optical fiber acoustic wave sensing system uses a high-coherence narrow-linewidth laser, and the refractive index is randomly changed along the optical fiber direction, the rayleigh scattering optical signals at various positions along the optical fiber can be affected by effects such as coherent fading, so that the backward rayleigh scattering light intensity of certain areas is sharply reduced, and is close to or even smaller than the background noise of the optical fiber sensing system, the serious degradation of the signal intensity can cause the inability to demodulate accurate phase information, and further cause positioning errors or signal distortion of demodulation results.
The embodiment of the application provides a method and a system for eliminating a deterioration effect caused by distributed acoustic wave sensing coherent fading, which are used for solving the technical problems that in the related art, due to the influence of coherent fading and other effects on Rayleigh scattering optical signals at various positions along an optical fiber, the backward Rayleigh scattering light intensity of certain areas is suddenly reduced and is close to or even smaller than the background noise of an optical fiber sensing system, the serious deterioration of the signal intensity can cause the incapability of demodulating accurate phase information, and further, the positioning error or signal distortion of a demodulation result is caused.
Fig. 1 is a schematic structural diagram of a distributed acoustic wave sensor system according to an embodiment of the present application.
In some examples, referring to fig. 1, the distributed acoustic wave sensing system includes a laser emitting unit 1, a sensing unit 2, a demodulation unit 3, and a control unit. The output end of the laser emission unit 1 is connected with the input end of the sensing unit 2, the output end of the sensing unit 2 is connected with the input end of the demodulation unit 3, and the output end of the demodulation unit 3 is connected with the input end of the control unit.
The laser emitting unit 1 comprises a laser 101, an isolator 102, an acousto-optic modulator 103 and a first erbium-doped fiber amplifier 104, wherein the output end of the laser 101 is connected with the input end of the isolator 102, the output end of the isolator 102 is connected with the input end of the acousto-optic modulator 103, the output end of the acousto-optic modulator 103 is connected with the input end of the first erbium-doped fiber amplifier 104, and the output end of the erbium-doped fiber amplifier is connected with the input end of the sensing unit 2. The laser 101 is configured to emit a laser signal to an input of the isolator 102; the isolator 102 is configured such that the laser beam is output unidirectionally by the isolator 102 to the acousto-optic modulator 103; the acousto-optic modulator 103 is configured to modulate the pulse width between pulses of the laser signal and the number of frequencies between pulses; the first erbium-doped fiber amplifier 104 is configured to amplify the laser signal output by the output terminal of the acousto-optic modulator 103.
The sensing unit 2 comprises a circulator 201, a sensing optical fiber 202 and a piezoelectric ceramic 203; the input end of the circulator 201 is connected with the output end of the first erbium-doped fiber amplifier 104, the first output end of the circulator 201 is connected with the input end of the piezoelectric ceramic 203, and the output end of the piezoelectric ceramic 203 is connected with the sensing fiber 202; a second output of circulator 201 is connected to an input of demodulation unit 3.
The demodulation unit 3 comprises a second erbium doped fiber amplifier 301, a first coupler 302, a second coupler 303, a photodetector 304 and an acquisition card 305. The input end of the second erbium-doped fiber amplifier 301 is connected with the output end of the sensing unit 2, and the second erbium-doped fiber amplifier 301 is configured to amplify the backward rayleigh scattering signal output by the output end of the sensing unit 2; the output end of the second erbium-doped fiber amplifier 301 is connected with the input end of the first coupler 302, the output end of the first coupler 302 is connected with the input end of the second coupler 303, the output end of the second coupler 303 is connected with the input end of the photoelectric detector 304, the output end of the photoelectric detector 304 is connected with the input end of the acquisition card 305, and the output end of the acquisition card 305 is connected with the input end of the control unit. Three photodetectors 304 are provided, namely, a first photodetector 304a, a second photodetector 304b, and a third photodetector 304c.
In a specific implementation, a laser signal is input by the laser 101, sequentially passes through the isolator 102, the acousto-optic modulator 103 and the first erbium-doped fiber amplifier 104, and then is output to the sensing fiber 202 through the first output end of the circulator 201, the sensing fiber 202 is provided with the piezoelectric ceramics 203 along the line, the vibration signal generated by the piezoelectric ceramics 203 generates a backward rayleigh scattering signal in a preset time period, and the backward rayleigh scattering signal is sequentially output to the demodulation unit 3 through the second output end of the circulator 201.
The backward rayleigh scattering signal after entering the demodulation unit 3 is output to the photodetector 304 through the second erbium-doped fiber amplifier 301 and the first coupler 302, and is output to the acquisition card 305 through the photodetector 304, the acquisition card 305 outputs the acquired backward rayleigh scattering signal to the controller, and the coherent fading of the backward rayleigh scattering signal is suppressed in the controller.
Fig. 2 is a method step diagram of a method for eliminating a degradation effect caused by distributed acoustic wave sensing coherent fading according to an embodiment of the present application.
In a first aspect, referring to fig. 2, an embodiment of the present application provides a method for eliminating a degradation effect caused by distributed acoustic wave sensing coherent fading, including the steps of:
S100: the backward Rayleigh scattering signal generated by the vibration signal along the line of the sensing optical fiber 202 in a preset time period is collected.
For example, in testing the distributed optical fiber acoustic wave sensing system, the distributed optical fiber acoustic wave sensing system may be built, for example, a vibration signal is applied to the piezoelectric ceramic 203 on the sensing optical fiber 202 on the acousto-optic modulator 103, and the demodulation unit 3 is used to collect backward rayleigh scattering signals generated by the sensing optical fiber 202 along the line in a preset period of time.
S200: acquiring first demodulation video-time domain dynamic information; the first demodulated video-time domain dynamic information is an image of the backward rayleigh scattering signal at each position along the line, which is obtained by initially demodulating the backward rayleigh scattering signal, dynamically changing with time.
Illustratively, the demodulation unit 3 is employed to obtain first demodulated video-time domain dynamic information.
In some examples, acquiring the first demodulated video-time domain dynamic information specifically includes the steps of:
s210: demodulating the backward Rayleigh scattering signal to obtain first demodulation information; wherein the first demodulation information includes demodulation information including noise information at various locations along the sensing fiber 202.
And demodulating the backward Rayleigh scattering signal by adopting a controller to obtain first demodulation information.
S220: and constructing first demodulation video-time domain dynamic information according to the first demodulation information.
And constructing first demodulation video-time domain dynamic information according to the first demodulation information by adopting a controller.
In some other examples, prior to acquiring the first demodulated video-time domain dynamic information, further comprising the steps of:
S200a: and filtering and preprocessing the backward Rayleigh scattering signals to filter the backward Rayleigh scattering signals outside the preset frequency.
For example, a filter may be provided between the circulator 201 and the second erbium doped fiber amplifier 301 to filter out backward rayleigh scattering signals outside the preset frequency using the filter.
For another example, the frequency range of the backward Rayleigh scattering signal may be 20MHz, and the center frequency is determined by the frequency shift value of the acousto-optic modulator 103, such as 200MHz or 150MHz.
S300: the first demodulated video-time domain dynamic information is framed along each position along the sensing fiber 202 according to the time domain length to obtain a plurality of framed static information.
For example, the first demodulated video-time domain dynamic information may be divided into a number of sub-frame static information with 0.01s as one frame, where the sub-frame static information is a static image.
S400: and carrying out morphological technical processing on the framing static information to obtain corresponding framing processing information so as to inhibit the coherent fading effect.
For example, the controller performs morphological technical processing on the static information of the sub-frames to obtain corresponding sub-frame processing information so as to suppress the coherent fading effect.
Fig. 3 is a specific step diagram of S400 in fig. 2.
Referring to fig. 3, in some other examples, S400 specifically includes the steps of:
S410: and defining the reference structural element as an operator of the primary scale, and expanding the structural element B i of the ith scale by the reference structural element B.
S420: and filtering the framing static information by adopting operators of each stage of scale to obtain a plurality of filtering results respectively corresponding to the operators.
Wherein, S420 specifically includes the following steps:
s421: and carrying out frequency domain denoising on the framing static information to obtain a preset signal-to-noise ratio.
S422: and obtaining a filtering signal-to-noise ratio according to the filtering result and the framing static information.
S423a: if the filtering signal-to-noise ratio is larger than the preset signal-to-noise ratio, expanding the reference structural element and then continuously filtering the sub-frame static information;
s423b: and if the filtering signal-to-noise ratio is smaller than the preset signal-to-noise ratio, obtaining a filtering result.
S430: and combining the filtering results to obtain framing processing information.
Illustratively, S430 specifically includes the steps of:
s431: calculating the ratio of the abnormal pixel value to the whole pixel value in the framing processing information, wherein the abnormal pixel value is a pixel with the pixel value smaller than the preset pixel value in the framing processing information.
S432a: and continuing morphological technical processing on the framing processing information with the ratio of the abnormal pixel value to the integral pixel value being larger than the preset ratio.
S432b: and continuing morphological technical processing on the framing processing information with the ratio of the abnormal pixel value to the integral pixel value being larger than the preset ratio.
For example, the preset ratio may be set to 2%, and the frame processing information with the ratio of the abnormal pixel value to the overall pixel value being less than 2% may be combined and reconstructed to obtain the corresponding frame processing information;
and continuing morphological technical processing on the framing processing information with the ratio of the abnormal pixel value to the whole pixel value being more than 2%.
In other examples, the framing process information I LL is formulated as:
；
Wherein I represents framing static information; b i represents a structural element operator of the ith scale obtained by expanding a group of reference structural elements; w i represents the setting of the weight parameters; an open operator for representing corrosion-before-expansion of the framing static information I; Representing an expansion operation; n represents the number of structural elements; i LL denotes the obtained framing processing information.
The calculation formula of the weight W i is as follows:
；
wherein, Representing the size of structural element B i.
S500: combining and reconstructing the plurality of frame processing information to obtain second demodulation video-image time domain dynamic information after inhibiting the coherent fading effect; the second demodulated video-image time domain dynamic information is dynamic change information after the backward rayleigh scattering signals at various positions along the sensing optical fiber 202 inhibit the coherent fading effect.
From the above description, it can be seen that the following technical effects are achieved:
In a first aspect, an embodiment of the present application provides a method for eliminating a degradation effect caused by distributed acoustic wave sensing coherent fading, where the embodiment of the present application obtains first demodulated video-time domain dynamic information by demodulating a backward rayleigh scattering signal, frames the first demodulated video-time domain dynamic information along each position along a sensing optical fiber 202 according to a time domain length to obtain a plurality of frame-division static information, and performs morphological processing on the frame-division static information to obtain frame-division processing information, where the frame-division static information is subjected to morphological processing to suppress a coherent fading suppression effect, and then combines and reconstructs a plurality of frame-division processing information to obtain second demodulated video-image time domain dynamic information after suppressing the coherent fading effect, that is, a dynamic change image after suppressing the coherent fading effect by the backward rayleigh scattering signal at each position along the sensing optical fiber 202, thereby avoiding the coherent fading effect, reducing a measurement error, and improving a measurement accuracy of the distributed acoustic wave sensing system.
In a second aspect, an embodiment of the present application provides a distributed acoustic wave sensing system, and the method for suppressing coherent fading applied to the distributed acoustic wave sensing system in any one of the technical solutions of the first aspect is adopted;
The system comprises a demodulation unit 3 and a control unit, wherein the demodulation unit 3 and the control unit are connected through signals;
The demodulation unit 3 is configured to collect backward rayleigh scattering signals generated by vibration signals along the sensing optical fiber 202 within a preset time period;
The demodulation unit 3 is configured to obtain first demodulated video-time domain dynamic information; the first demodulated video-time domain dynamic information is an image of the backward rayleigh scattering signal along each position of the line, which is obtained by initially demodulating the backward rayleigh scattering signal, dynamically changing along time;
The control unit is configured to frame the first demodulated video-time domain dynamic information along each position along the sensing optical fiber 202 according to the time domain length to obtain a plurality of frame static information;
The control unit is configured to perform morphological technical processing on the static information of the sub-frames to obtain corresponding sub-frame processing information so as to inhibit the coherent fading effect;
The control unit is configured to combine and reconstruct the plurality of frame processing information to obtain second demodulated video-image time domain dynamic information after the coherent fading effect is restrained; the second demodulated video-image time domain dynamic information is dynamic change information after the backward rayleigh scattering signals at various positions along the sensing optical fiber 202 inhibit the coherent fading effect.
The embodiment of the application also provides a distributed acoustic wave sensing system, which adopts the method for eliminating the deterioration effect caused by the distributed acoustic wave sensing coherent fading in any one of the above schemes, so that the method has all the beneficial effects of the method for eliminating the deterioration effect caused by the distributed acoustic wave sensing coherent fading in any one of the above schemes, and is not repeated here.
It is to be understood that, based on the several embodiments provided in the present application, those skilled in the art may combine, split, reorganize, etc. the embodiments of the present application to obtain other embodiments, which all do not exceed the protection scope of the present application.
The foregoing detailed description of the embodiments of the present application further illustrates the purposes, technical solutions and advantageous effects of the embodiments of the present application, and it should be understood that the foregoing is merely a specific implementation of the embodiments of the present application, and is not intended to limit the scope of the embodiments of the present application, and any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the embodiments of the present application should be included in the scope of the embodiments of the present application.
Claims (8)
1. A method for canceling a degradation effect caused by distributed acoustic wave sensing coherent fading, comprising:
Collecting backward Rayleigh scattering signals generated by vibration signals along the sensing optical fiber within a preset time period;
Acquiring first demodulation video-image time domain dynamic information; the first demodulation video-image time domain dynamic information is an image of the backward Rayleigh scattering signal along each position of the sensing optical fiber, which is obtained after the backward Rayleigh scattering signal is initially demodulated, which dynamically changes along with time;
framing the first demodulated video-image time domain dynamic information along each position along the sensing optical fiber according to the time domain length to obtain a plurality of framing static information;
Carrying out morphological technical processing on the framing static information to obtain corresponding framing processing information so as to inhibit coherent fading effect; the morphological processing of the static information of the frame division to obtain corresponding processing information of the frame division, so as to inhibit the coherent fading effect, specifically comprises the following steps: defining a reference structural element as an operator of a primary scale, and expanding the structural element B i of the ith scale by the reference structural element B; filtering the framing static information by adopting operators of each level of scale to obtain a plurality of filtering results respectively corresponding to the operators; combining a plurality of filtering results to obtain the framing processing information;
Combining and reconstructing the plurality of frame processing information to obtain second demodulated video-image time domain dynamic information after inhibiting the coherent fading effect; the second demodulation video-image time domain dynamic information is dynamic change information after the backward Rayleigh scattering signals at all positions along the sensing optical fiber inhibit the coherent fading effect.
2. The method for eliminating degradation caused by coherent fading of distributed acoustic wave sensing according to claim 1, wherein after the step of filtering the framing static information by using operators of each level scale to obtain a plurality of filtering results respectively corresponding to the plurality of operators, further comprising:
carrying out frequency domain denoising on the framing static information to obtain a preset signal-to-noise ratio;
According to the filtering result and the framing static information, a filtering signal-to-noise ratio is obtained;
If the filtering signal-to-noise ratio is larger than the preset signal-to-noise ratio, the reference structural element is expanded and then the framing static information is continuously filtered;
and if the filtering signal-to-noise ratio is smaller than the preset signal-to-noise ratio, acquiring the filtering result.
3. The method for eliminating the degradation effect caused by the distributed acoustic wave sensing coherent fading according to claim 1, wherein the formula for obtaining the framing processing information I LL is:
Wherein I represents framing static information; b i represents a structural element operator of the ith scale obtained by expanding a group of reference structural elements; w i represents the setting of the weight parameters; /(I) An open operator for representing corrosion-before-expansion of the framing static information I; and one represents an expansion operation; n represents the number of structural elements; i LL denotes the obtained framing processing information.
4. The method for eliminating degradation effects caused by distributed acoustic wave sensing coherent fading according to claim 3, wherein the calculation formula of the weight W i is:
wherein/> Representing the size of structural element B i.
5. The method for eliminating degradation effects caused by distributed acoustic wave sensing coherent fading according to any one of claims 1 to 4, wherein the step of performing morphological processing on the static information of frames to obtain corresponding frame processing information, further comprises:
calculating the ratio of an abnormal pixel value to an integral pixel value in the framing processing information, wherein the abnormal pixel value is a pixel of which the pixel value in the framing processing information is smaller than a preset pixel value;
Combining and reconstructing framing processing information with the ratio of the abnormal pixel value to the integral pixel value smaller than a preset ratio to obtain corresponding second demodulation video-image time domain dynamic information;
and continuing morphological technical processing on the framing processing information with the ratio of the abnormal pixel value to the integral pixel value being larger than the preset ratio.
6. The method of any one of claims 1-4, further comprising, prior to the step of obtaining the first demodulated video-image time domain dynamic information:
And filtering and preprocessing the backward Rayleigh scattering signal to filter the backward Rayleigh scattering signal outside the preset frequency.
7. The method for eliminating the degradation effect caused by the coherent fading of the distributed acoustic wave sensing according to any one of claims 1 to 4, wherein the step of obtaining the first demodulated video-image time domain dynamic information comprises the steps of:
performing initial demodulation on the backward Rayleigh scattering signal to obtain first demodulation information; the first demodulation information comprises abnormal demodulation information caused by coherent fading phenomena at each position along the sensing optical fiber;
and constructing the first demodulation video-image time domain dynamic information according to the first demodulation information.
8. A distributed acoustic wave sensing system, characterized in that the method for eliminating the deterioration effect caused by the distributed acoustic wave sensing coherent fading is adopted according to any one of claims 1 to 7;
the system comprises a demodulation unit and a control unit, wherein the demodulation unit is connected with the control unit through signals;
the demodulation unit is configured to collect backward Rayleigh scattering signals generated by vibration signals in the line of the sensing optical fiber within a preset time period;
The demodulation unit is configured to acquire first demodulated video-image time domain dynamic information; the first demodulation video-image time domain dynamic information is an image of the backward Rayleigh scattering signal along each position of the sensing optical fiber, which is obtained after the backward Rayleigh scattering signal is initially demodulated, which dynamically changes along with time;
The control unit is configured to frame the first demodulated video-image time domain dynamic information along each position along the sensing optical fiber according to the time domain length to obtain a plurality of frame static information;
The control unit is configured to perform morphological technical processing on the framing static information to obtain corresponding framing processing information so as to inhibit coherent fading effect; the morphological processing of the static information of the frame division to obtain corresponding processing information of the frame division, so as to inhibit the coherent fading effect, specifically comprises the following steps: defining a reference structural element as an operator of a primary scale, and expanding the structural element Bi of the ith scale by the reference structural element B; filtering the framing static information by adopting operators of each level of scale to obtain a plurality of filtering results respectively corresponding to the operators; combining a plurality of filtering results to obtain the framing processing information;
the control unit is configured to combine and reconstruct a plurality of the frame static information to obtain second demodulated video-image time domain dynamic information after the coherent fading effect is restrained; the second demodulation video-image time domain dynamic information is dynamic change information after the backward Rayleigh scattering signals at all positions along the sensing optical fiber inhibit the coherent fading effect.
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