Distributed speed sensing phase demodulation method, device and equipment

Abstract

The invention provides a distributed speed sensing phase demodulation method, device and equipment, and belongs to the field of optical fiber sensing signal demodulation, and the method comprises the steps: determining an IQ demodulation initial phase and an IQ signal amplitude based on an IQ signal; performing phase decoupling operation on the IQ demodulation initial phase, and sequentially subtracting a receiving point initial phase, a laser pulse initial phase and an optical path integral phase of an optical fiber sensing signal output position from the IQ demodulation initial phase to obtain a displacement sensing phase; performing time difference operation on the displacement sensing phase to obtain speed type sensing data; and performing phase unwrapping and de-noising processing on the speed type sensing data to obtain final speed sensing demodulation phase data. The speed sensing demodulation phase data obtained by the method provided by the invention keeps low wave number information, the actual application effect of optical fiber sensing can be improved, and the consistency with a wave field acquired by a traditional speed type detector is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber optic sensing signal demodulation. Specifically, it relates to a distributed velocity sensing phase demodulation method, a distributed velocity sensing phase demodulation device, an electronic device, and a computer-readable storage medium. Background Art

[0002] Currently, moving coil electronic geophones are generally velocity-type, and the vibration wave field they collect represents the vibration velocity of the mass point. The fiber optic distributed acoustic sensing technology generally uses a phase-sensitive optical time domain reflectometer ( -OTDR), which mainly uses the Rayleigh backscattering of the optical fiber to obtain the vibration information around the optical fiber through phase demodulation. The optical fiber serves as both a sensing medium and a transmission medium, and can continuously sense the acoustic vibration information around the optical fiber and record it through high-density time and space sampling. The fiber optic distributed sensing technology mainly uses the Rayleigh backscattering generated when the laser propagates in the optical fiber. When the medium around the optical fiber vibrates, the Rayleigh backscattering of the probing laser will also change accordingly. By coherent detection and phase demodulation of this optical signal, the vibration wave field information of the medium can be obtained. Since the phase difference between adjacent points at the gauge distance is generally used as the demodulated phase output, its output is actually local strain. When the phase difference before output is further differentiated along time, its output is the local strain rate. This technology has been widely used in well seismic data acquisition, dam safety monitoring, perimeter security, pipeline monitoring, etc.

[0003] -OTDR obtains the phase information of Rayleigh backscattering through phase demodulation. Since the phase information itself is related to the path and has a non-linear relationship with external disturbances, it seriously affects the practical application of phase demodulation. Currently, the existing technology mainly overcomes the non-linear effect and improves the signal-to-noise ratio by calculating the phase difference within the gauge distance and local averaging, but this phase demodulation method will lose the low wavenumber wave field information and cannot reduce the noise level to an ideal level, and there are also obvious differences from the response of traditional geophones. Many experts at home and abroad are committed to the research of high signal-to-noise ratio phase demodulation.

[0004] In summary, most of the existing distributed acoustic sensing phase demodulation methods are strain demodulation, and there are still many deficiencies in practical applications. Therefore, the need to accurately and efficiently perform velocity sensing phase demodulation and maintain broadband wave field information is very urgent. Summary of the Invention

[0005] Aiming at the technical problem of the deficiencies existing in the distributed acoustic wave sensing phase demodulation method in practical applications in the prior art, the present invention provides a distributed velocity sensing phase demodulation method. By adopting this method, it is possible to obtain velocity-type sensing information by performing phase decoupling and then taking a time difference along the time without performing gauge difference calculation, and the frequency characteristics of the signal are completely maintained, and the data quality is significantly improved, providing a guarantee for subsequent data processing and applications.

[0006] To achieve the above object, the first aspect of the present invention provides a distributed velocity sensing phase demodulation method, and the phase demodulation method includes: determining the initial IQ demodulation phase and the IQ signal amplitude based on the IQ signal; performing a phase decoupling operation on the initial IQ demodulation phase, and successively subtracting the initial phase of the receiving point at the output position of the optical fiber sensing signal, the initial phase of the laser pulse, and the optical path integral phase from the initial IQ demodulation phase to obtain the displacement sensing phase; performing a time difference operation on the displacement sensing phase to obtain velocity-type sensing data; determining the coherent fading position in the velocity-type sensing data based on the IQ signal amplitude, and using linear interpolation between adjacent normal points to eliminate the influence of coherent fading to obtain the velocity-type sensing data after coherent fading noise suppression; performing phase unwrapping on the velocity-type sensing data after coherent fading noise suppression to obtain the unwrapped velocity-type sensing data; transposing the unwrapped velocity-type sensing data into trace-order recorded data, and performing denoising through subsequent data processing to obtain the final velocity sensing demodulation phase data.

[0007] In an exemplary embodiment of the present invention, the performing a phase decoupling operation on the initial IQ demodulation phase, and successively subtracting the initial phase of the receiving point at the output position of the optical fiber sensing signal, the initial phase of the laser pulse, and the optical path integral phase from the initial IQ demodulation phase to obtain the displacement sensing phase may include: selecting a plurality of time sampling values for point-by-point statistical analysis at the j-th optical fiber sensing signal output position without an external acoustic wave signal to obtain the initial phase of the receiving point at the j-th optical fiber sensing signal output position Subtracting the initial phase of the receiving point at the j-th optical fiber sensing signal output position from the initial IQ demodulation phase ω 0 (i,j) at the i-th sampling moment and the j-th optical fiber sensing signal output position to obtain the first decoupled phase ω 1 (i,j) at the i-th sampling moment and the j-th optical fiber sensing signal output position; determining the initial phase of the laser pulse at the i-th sampling moment and the phase linear change factor k(i) at the i-th sampling moment based on the linear relationship between different first decoupled phases at the i-th sampling moment with the change of the optical fiber sensing signal output position; determining the optical path integral phase j×k(i) at the i-th sampling moment and the j-th optical fiber sensing signal output position based on the phase linear change factor k(i) at the i-th sampling moment; subtracting the optical path integral phase from the first decoupled phase ω to obtain the displacement sensing phase at the i-th sampling moment and the j-th optical fiber sensing signal output position; and repeating the above steps for each optical fiber sensing signal output position to obtain the displacement sensing phase of all optical fiber sensing signal output positions. 1(i, j) minus the initial phase of the laser pulse Get the second decoupling phase ω of the jth optical fiber sensor signal output position at the i-th sampling moment 2 (i, j); from the second decoupled phase ω 2 The optical path integral phase j×k(i) is subtracted from (i, j) to obtain the third decoupling phase ω of the j-th optical fiber sensor signal output position at the i-th sampling moment 3 (i, j); the third decoupling phase ω 3 (i,j) is determined as the displacement sensing phase of the jth optical fiber sensing signal output position at the i-th sampling moment

[0008] In an exemplary embodiment of the present invention, multiple phase decoupling operations can be performed on the third decoupling phase, and the third decoupling phase obtained by the final operation is determined as the displacement sensing phase; wherein, in each iterative operation, the IQ demodulation initial phase in the current iterative process is updated to the third decoupling phase obtained in the previous iterative operation.

[0009] In an exemplary embodiment of the present invention, the calculation formula of the initial phase of the receiving point may be:

[0010]

[0011] in, is the initial phase of the receiving point at the jth optical fiber sensor signal output position, m is the number of time sample points used for statistics at each sensor position before the signal to be measured arrives, that is, when the optical fiber is undisturbed and stationary, and w 0 (i, j) is the IQ demodulation initial phase of the j-th optical fiber sensor signal output position at the i-th sampling moment, i is the sampling time sequence number, and j is the optical fiber sensor signal output position sequence number.

[0012] In an exemplary embodiment of the present invention, the initial phase of the laser pulse at the i-th sampling moment is determined based on the linear relationship between the different first decoupling phases at the i-th sampling moment and the output position of the optical fiber sensor signal. and the phase linear change factor k(i) at the i-th sampling moment, may include: determining a plurality of first decoupling phases corresponding to different optical fiber sensor signal output positions at the i-th sampling moment; performing multi-point linear fitting on the plurality of first decoupling phases corresponding to different optical fiber sensor signal output positions at the i-th sampling moment to obtain a linear fitting relationship between the first decoupling phase at the i-th sampling moment and the optical fiber sensor signal output position; determining the intercept of the linear fitting relationship as the initial phase of the laser pulse at the i-th sampling moment. The slope of the linear fitting relationship is determined as the phase linear change factor k(i) at the i-th sampling moment.

[0013] In an exemplary embodiment of the present invention, the calculation formula of the velocity-type sensing data may be:

[0014]

[0015] Wherein, is the velocity-type sensing data at the output position of the j-th fiber optic sensing signal at the i-th sampling moment, is the displacement sensing phase at the output position of the j-th fiber optic sensing signal at the i-th sampling moment, is the displacement sensing phase at the output position of the j-th fiber optic sensing signal at the (i + 1)-th sampling moment.

[0016] A second aspect of the present invention provides a distributed velocity sensing phase demodulation device. The phase demodulation device may include: an initial phase and amplitude determination unit, a phase decoupling operation unit, a velocity sensing determination unit, a coherent fading noise suppression unit, a phase unwrapping processing unit, and a subsequent processing unit; the initial phase and amplitude determination unit is configured to determine the IQ demodulation initial phase ω 0 (i,j) and the IQ signal amplitude A(i,j); the phase decoupling operation unit is configured to perform a phase decoupling operation on the IQ demodulation initial phase ω 0 (i,j), and successively subtract the receiving point initial phase 0 of the fiber optic sensing signal output position, the laser pulse initial phase, and the optical path integral phase j×k(i) from the IQ demodulation initial phase ω to obtain the displacement sensing phase; the velocity sensing determination unit is configured to perform a time difference operation on the displacement sensing phase to obtain the velocity-type sensing data; the coherent fading noise suppression unit is configured to determine the coherent fading position in the velocity-type sensing data based on the IQ signal amplitude, and use linear interpolation of adjacent normal points to eliminate the influence of coherent fading to obtain the velocity-type sensing data after suppressing the coherent fading noise; the phase unwrapping processing unit is configured to perform phase unwrapping on the velocity-type sensing data after suppressing the coherent fading noise to obtain the unwrapped velocity-type sensing data; the subsequent processing unit is configured to transpose the unwrapped velocity-type sensing data into trace-order recorded data and perform denoising through subsequent data processing to obtain the final velocity sensing demodulation phase data.

[0017] In an exemplary embodiment of the present invention, the phase decoupling operation unit may include: a receiving point initial phase determination module, a first decoupled phase determination module, a laser pulse initial phase and linear change factor determination module, an optical path integral phase determination module, a second decoupled phase determination module, a third decoupled phase determination module, and a displacement sensing phase determination module; the receiving point initial phase determination module is configured to perform point-by-point statistical analysis on a plurality of time sampling values selected for the output position of the j-th fiber optic sensing signal without an external acoustic wave signal, and obtain the receiving point initial phase of the output position of the j-th fiber optic sensing signal. The first decoupled phase determination module is configured to subtract the receiving point initial phase of the output position of the j-th fiber optic sensing signal from the IQ demodulation initial phase ω 0 (i, j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment. To obtain the first decoupled phase ω 1 (i, j) of the output position of the j-th fiber optic sensing signal at the i-th sampling moment; the laser pulse initial phase and linear change factor determination module is configured to determine the laser pulse initial phase at the i-th sampling moment And the phase linear change factor k(i) at the i-th sampling moment; the optical path integral phase determination module is configured to determine the optical path integral phase j×k(i) of the output position of the j-th fiber optic sensing signal at the i-th sampling moment based on the phase linear change factor k(i) at the i-th sampling moment; the second decoupled phase determination module is configured to subtract the laser pulse initial phase 1 From the first decoupled phase ω To obtain the second decoupled phase ω 2 (i, j) of the output position of the j-th fiber optic sensing signal at the i-th sampling moment; the third decoupled phase determination module is configured to subtract the optical path integral phase j×k(i) from the second decoupled phase ω 2 To obtain the third decoupled phase ω 3 (i, j) of the output position of the j-th fiber optic sensing signal at the i-th sampling moment; the displacement sensing phase determination module is configured to determine the third decoupled phase ω 3 (i, j) as the displacement sensing phase of the output position of the j-th fiber optic sensing signal at the i-th sampling moment.

[0018] A third aspect of the present invention provides an electronic device, the electronic device includes a processor and a memory, at least one computer program is stored in the memory, and the at least one computer program is loaded and executed by one or more of the above processors, so that the processor executes the above-mentioned distributed speed sensing phase demodulation method.

[0019] In a fourth aspect of the present invention, there is provided a computer-readable storage medium storing at least one program code, which is loaded and executed by a processor to cause a computer to execute the above-mentioned distributed velocity sensing phase demodulation method.

[0020] Through the technical solution provided by the present invention, the present invention has at least the following technical effects:

[0021] (1) The present invention provides a new distributed velocity sensing phase demodulation method, which restores the velocity-type response information of the wave field to be measured through a series of targeted phase information decoupling and time difference, and is of great significance for improving the quality of fiber optic sensing data acquisition, protecting low wavenumber wave field information, and comparative analysis and matching processing with traditional geophones;

[0022] (2) The distributed velocity sensing phase demodulation method of the present invention does not require obtaining strain information by taking differences according to the gauge length, completely preserves the frequency characteristics of the signal, and significantly improves the data quality, providing a guarantee for subsequent data processing and applications;

[0023] (3) Compared with traditional geophones, the velocity sensing demodulation phase data obtained by the present invention preserves the low wavenumber information, thereby improving the actual application effect of fiber optic sensing and achieving consistency with the wave field collected by traditional velocity geophones.

[0024] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. Together with the following specific implementation manners, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0026] Figure 1 is a flowchart of the distributed velocity sensing phase demodulation method provided by the embodiment of the present invention;

[0027] Figure 2 is an IQ demodulation initial phase diagram of the fiber optic IQ signal provided by the embodiment of the present invention;

[0028] Figure 3 is a recorded diagram of the displacement phase demodulation of the fiber optic IQ signal provided by the embodiment of the present invention;

[0029] Figure 4 is a recorded diagram of the velocity phase demodulation of the fiber optic IQ signal provided by the embodiment of the present invention;

[0030] Figure 5Structural diagram of the distributed velocity sensing phase demodulation device provided by an embodiment of the present invention;

[0031] Figure 6 Structural diagram of the electronic device provided by an embodiment of the present invention.

[0032] Description of reference numerals

[0033] 101 - Initial phase and amplitude determination unit, 102 - Phase decoupling operation unit, 103 - Velocity sensing determination unit, 104 - Coherent fading noise suppression unit, 105 - Phase unwrapping processing unit, 106 - Subsequent processing unit, 201 - Processor, 202 - Memory. Detailed implementation manners

[0034] The following will describe in detail the specific implementation manners of the embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific implementation manners described herein are only used to illustrate and explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention.

[0035] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0036] In the present invention, "first", "second", etc. are only for the convenience of description and easy distinction, and cannot be understood as indicating or implying relative importance. In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, terms such as "installation", "connection", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection; it can be a wired connection, or a wireless connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0037] In the prior art, in the process of phase demodulation of distributed velocity-type sensing data, generally, the phase difference within the gauge length and local averaging are used to overcome the non-linear effect and improve the signal-to-noise ratio. However, this phase demodulation method will cause the loss of low wavenumber wavefield information and make the noise level unable to be reduced to the ideal level. In order to make up for the deficiencies existing in the existing distributed acoustic wave sensing phase demodulation method in practical applications, the present invention proposes a distributed velocity sensing phase demodulation method that does not require obtaining strain information through the phase difference within the gauge length. This method can accurately and efficiently perform velocity sensing phase demodulation and meet the requirements of maintaining broadband wavefield information.

[0038] The overall technical concept of the present invention is: First, the optical fiber is laid in the measured environment and the optical fiber is fully coupled with the environment by certain means. One end of the optical fiber is connected -OTDR instrument, - The -OTDR instrument emits laser pulses and obtains the IQ quadrature information of the Rayleigh backscattering of the optical pulses through the coherent detection method; then, through a series of phase decoupling operations on the initial phase of the IQ demodulation, the initial phase of the laser pulse, the initial phase of the receiving points within the pulse range at each sensing position, and the optical path integral phase in the initial phase of the IQ demodulation are gradually eliminated to obtain the displacement sensing phase of the signal to be measured; finally, a time difference operation is performed on the displacement sensing phase of the signal to be measured to obtain the required velocity - type sensing data. Through a series of phase decoupling operations and time difference on the demodulated phase, the distributed velocity response information of the wave field to be detected is restored, the low - frequency and low - wavenumber information is fully maintained, and thus the actual application effect of fiber optic sensing is improved, realizing the consistency with the wave field collected by traditional velocity - type detectors.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0040] Please refer to Figure 1 , in the first aspect of the embodiment of the present invention, a distributed velocity sensing phase demodulation method is provided, and the method includes the following steps:

[0041] Step S101: Determine the initial phase ω 0 (i,j) of the IQ demodulation and the amplitude A(i,j) of the IQ signal.

[0042] It should be noted that the IQ signal includes the in - phase signal I(i,j) and the quadrature signal Q(i,j) respectively. According to the in - phase signal I(i,j) and the quadrature signal Q(i,j), the initial phase ω 0 (i,j) of the IQ demodulation and the amplitude A(i,j) of the IQ signal can be calculated.

[0043] The calculation formula for the initial phase ω 0 (i,j) of the IQ demodulation is:

[0044]

[0045] The calculation formula for the amplitude A(i,j) of the IQ signal is:

[0046]

[0047] In formulas (1) - (2), ω 0 (i,j) is the initial phase of the IQ demodulation at the output position of the j - th fiber optic sensing signal at the i - th sampling moment; Q(i,j) is the quadrature signal at the output position of the j - th fiber optic sensing signal at the i - th sampling moment; I(i,j) is the in - phase signal at the output position of the j - th fiber optic sensing signal at the i - th sampling moment; A(i,j) is the amplitude of the IQ signal at the output position of the j - th fiber optic sensing signal at the i - th sampling moment.

[0048] Step S102: For the initial phase ω 0 (i, j) of IQ demodulation, perform phase decoupling operation, and successively subtract from the initial phase ω 0 (i, j) the initial phase of the receiving point at the output position of the fiber optic sensing signal, the initial phase of the laser pulse, and the optical path integral phase j×k(i) to obtain the displacement sensing phase

[0049] Here, it should be noted that for the initial phase ω 0 (i, j) of the j-th fiber optic sensing signal output position at the i-th sampling moment, the following relational expression should be satisfied:

[0050]

[0051] Therefore, the displacement sensing phase of the signal to be measured can be obtained through the following calculation formula:

[0052]

[0053] In formulas (3) to (4), ω 0 (i, j) is the initial phase of IQ demodulation at the j-th fiber optic sensing signal output position at the i-th sampling moment, is the displacement sensing phase at the j-th fiber optic sensing signal output position at the i-th sampling moment, is the initial phase of the receiving point at the j-th fiber optic sensing signal output position, is the initial phase of the laser pulse at the i-th sampling moment, and j×k(i) is the optical path integral phase at the j-th fiber optic sensing signal output position at the i-th sampling moment.

[0054] Step S103: Perform time difference operation on the displacement sensing phase to obtain velocity-type sensing data.

[0055] Here, the calculation formula for the velocity-type sensing data is:

[0056]

[0057] In formula (5), is the velocity-type sensing data at the j-th fiber optic sensing signal output position at the i-th sampling moment, is the displacement sensing phase at the j-th fiber optic sensing signal output position at the i-th sampling moment, is the displacement sensing phase at the j-th fiber optic sensing signal output position at the (i + 1)-th sampling moment.

[0058] Step S104: Based on the amplitude of the IQ signal, determine the coherent fading positions in the velocity-type sensing data, and use linear interpolation between adjacent normal points to eliminate the influence of coherent fading, thereby obtaining the velocity-type sensing data after suppressing the coherent fading noise.

[0059] Step S105: Perform phase unwrapping on the velocity-type sensing data after suppressing the coherent fading noise to obtain the velocity-type sensing data after unwrapping.

[0060] Step S106: Transpose the velocity-type sensing data after unwrapping into trace-order recorded data, and perform denoising through subsequent data processing to obtain the final velocity sensing demodulation phase data.

[0061] Further, in a possible implementation manner, in step S102, for the initial IQ demodulation phase ω 0 (i,j), perform phase decoupling operation, and successively subtract from the initial IQ demodulation phase ω 0 (i,j) the initial phase of the receiving point at the output position of the optical fiber sensing signal the initial phase of the laser pulse and the optical path integral phase j×k(i) to obtain the displacement sensing phase The process may include but is not limited to the following sub-steps S1021 to sub-step S1027.

[0062] Sub-step S1021: Select a plurality of time sampling values for point-by-point statistical analysis at the j-th optical fiber sensing signal output position without an external acoustic wave signal to obtain the initial phase of the receiving point at the j-th optical fiber sensing signal output position

[0063] Specifically, the formula for the initial phase of the receiving point at the j-th optical fiber sensing signal output position is:

[0064]

[0065] In formula (6), is the initial phase of the receiving point at the j-th optical fiber sensing signal output position; m is the number of time sample points selected before the arrival of the signal to be measured at each sensing position, that is, the number of time sample points used to statistically analyze the initial phase of the receiving point when the optical fiber is in a stationary state; ω 0 (i,j) is the initial IQ demodulation phase at the j-th optical fiber sensing signal output position at the i-th sampling moment; i is the sampling time sequence number; j is the optical fiber sensing signal output position sequence number.

[0066] Sub-step S1022: Subtract from the initial IQ demodulation phase ω 0 (i,j) at the j-th optical fiber sensing signal output position at the i-th sampling moment the initial phase of the receiving point at the j-th optical fiber sensing signal output position Obtain the first decoupled phase ω 1 (i, j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment.

[0067] That is, the first decoupled phase ω 1 (i, j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment is calculated as follows:

[0068]

[0069] In Equation (7), ω 1 (i, j) is the first decoupled phase at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; ω 0 (i, j) is the initial IQ demodulation phase at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; is the initial phase of the receiving point at the output position of the j-th fiber optic sensing signal.

[0070] Sub-step S1023: Determine the initial laser pulse phase at the i-th sampling moment and the phase linear change factor k(i) based on the linear relationship between different first decoupled phases at the i-th sampling moment and the change of the fiber optic sensing signal output position. and the phase linear change factor k(i) at the i-th sampling moment.

[0071] Specifically, it can be assumed that the signal to be measured has a mean value of 0 in the fitting segment, that is, it has no influence on the calculation of the fitting parameters. Using the first decoupled phase ω 1 (i, j) after eliminating the receiving point initial phase response, the initial laser pulse phase and the phase linear change factor k(i) at different sampling moments are obtained through linear fitting.

[0072] Exemplarily, the process of determining the initial laser pulse phase and the phase linear change factor k(i) at the i-th sampling moment based on the linear relationship between different first decoupled phases at the i-th sampling moment and the change of the fiber optic sensing signal output position may include but is not limited to the following sub-steps S10231 to sub-step S10234.

[0073] Sub-step S10231: Determine a number of first decoupled phases corresponding to different fiber optic sensing signal output positions at the i-th sampling moment.

[0074] Sub-step S10232: Plot a linear fitting curve of a number of first decoupled phases corresponding to different fiber optic sensing signal output positions at the i-th sampling moment with respect to the change of the fiber optic sensing signal output position.

[0075] Sub-step S10233: According to the linear fitting curves of the first decoupling phases corresponding to the output positions of the optical fiber sensor signals at different sampling moments, the first decoupling phase at the i-th sampling moment and the output position of the optical fiber sensor signal are determined. Linear fitting relationship.

[0076] That is, assuming that the first decoupling phase ω at the i-th sampling time 1 (i,j) changes with the output position j of the optical fiber sensor signal The linear fitting relationship is:

[0077]

[0078] In formula (8), ω 1 (i, j) is the first decoupling phase of the j-th optical fiber sensor signal output position at the i-th sampling moment; is the initial phase of the laser pulse at the i-th sampling moment; j is the output position number of the optical fiber sensor signal; k(i) is the phase linear change factor at the i-th sampling moment.

[0079] In order to eliminate as much as possible The influence on fitting accuracy should be considered. The far end of the optical fiber with weaker signal and later arrival time should be selected as the fitting segment. To ensure the fitting accuracy, the fitting segment should not be too short and should generally be more than one quarter of the optical fiber length. The influence of phase winding should be considered during fitting and unwinding should be performed.

[0080] Sub-step S10234: The intercept in the linear fitting relationship is determined as the initial phase of the laser pulse at the i-th sampling moment Will The slope in the linear fitting relationship is determined as the phase linear change factor k(i) at the i-th sampling moment.

[0081] Sub-step S1024: Based on the phase linear variation factor k(i) at the i-th sampling moment, determine the optical path integrated phase j×k(i) of the j-th optical fiber sensor signal output position at the i-th sampling moment.

[0082] Sub-step S1025: Detecting the first decoupling phase ω of the j-th optical fiber sensor signal output position at the i-th sampling moment 1 (i, j) minus the initial phase of the laser pulse at the i-th sampling time Get the second decoupling phase ω of the jth optical fiber sensor signal output position at the i-th sampling moment 2 (i,j).

[0083] Sub-step S1026: Detecting the second decoupling phase ω of the j-th optical fiber sensor signal output position at the i-th sampling moment2 Subtract the optical path integral phase \(j\times k(i)\) at the \(j\)-th optical fiber sensing signal output position at the \(i\)-th sampling moment from \((i, j)\) to obtain the third decoupled phase \(\omega\) at the \(j\)-th optical fiber sensing signal output position at the \(i\)-th sampling moment. 3 (i, j).

[0084] Sub-step S1027: Determine the third decoupled phase \(\omega\) at the \(j\)-th optical fiber sensing signal output position at the \(i\)-th sampling moment 3 as the displacement sensing phase at the \(j\)-th optical fiber sensing signal output position at the \(i\)-th sampling moment.

[0085] Furthermore, in a possible implementation manner, to ensure the demodulation accuracy, the above sub-steps S1021 to S1027 can be iterated multiple times, and the third decoupled phase obtained by the final operation is determined as the final displacement sensing phase. Among them, during each iterative operation, update the IQ demodulation initial phase \(\omega\) 0 (i, j) in the current iterative process to the third decoupled phase \(\omega\) 3 (i, j) obtained in the previous iterative operation.

[0086] To verify the effectiveness and practicality of the distributed velocity sensing phase demodulation method of the present invention, taking the IQ data collected by the actual optical fiber -OTDR of a certain oil well as an example, the above distributed displacement sensing phase demodulation method is used to perform velocity sensing phase demodulation on the IQ data.

[0087] First, lay the optical fiber in the well, connect the optical fiber from the upper part by using an optical fiber distributed acoustic wave sensing receiving instrument, and collect the IQ data of the -OTDR instrument, and then perform velocity sensing phase demodulation processing on the IQ data collected by the actual optical fiber -OTDR of a certain oil well. The specific processing flow can include the following:

[0088] (1) Perform imbalance correction on the IQ signal outputs \(I(i, j)\) and \(Q(i, j)\) at different moments and different observation points obtained to ensure the orthogonality of the IQ signals.

[0089] (2) Calculate the IQ demodulation initial phase \(\omega\) of the IQ signals through formula (1) 0 (i, j).

[0090] (3) Perform point-by-point statistics on each output position of the optical fiber sensing without external acoustic wave signals to obtain the initial phase of the receiving point at the optical fiber sensing signal output position \(j\)

[0091] (4) The IQ demodulation initial phase \(\omega\) 0Subtract the initial phase of the receiving point corresponding to each optical fiber sensing signal output position from (i,j) to obtain the first decoupled phase ω after eliminating the influence of the initial phase of the receiving point at each sensing position 1 (i,j).

[0092] (5) Use the first decoupled phase ω 1 (i,j) corresponding to each sensing position at the i sampling moment and perform linear fitting with each optical fiber sensing signal output position j to obtain the laser pulse phase and the phase linear change factor k(i) at the i sampling moment.

[0093] Specifically, first calculate and determine the first decoupled phase ω 1 (i,j) corresponding to each sensing position at the i sampling moment, that is, obtain ω 1 (i,1), ω 1 (i,2) …… ω 1 (i,j), ω 1 (i,j + 1), ω 1 (i,j + 2) and other data points, and then draw the change curve of ω 1 versus the sensing position at the i sampling moment. After multi-point linear fitting, obtain the slope and intercept. This intercept is the laser pulse phase at the i sampling moment, and the slope is the phase linear change factor k at the i sampling moment.

[0094] (6) Subtract the initial phase of the receiving point corresponding to each output position 0 from the IQ demodulation initial phase ω in turn, the initial phase of the laser pulse and the optical path integral phase j×k(i) through formula (4) to obtain the displacement sensing phase

[0095] (7) To ensure the demodulation accuracy, use to replace ω 0 (i,j) and repeat steps (3) to (6).

[0096] (8) Perform time difference on the IQ displacement phase demodulation data through formula (5) to obtain the required velocity-type sensing data

[0097] (9) Use the amplitude of the IQ signal to judge the position of the fading noise and eliminate the influence of coherent fading.

[0098] (10) Perform phase unwrapping on to obtain the unwrapped velocity-type sensing data.

[0099] (11) Repeat steps (1) to (10) for all I / Q signals of all records to be demodulated, and transpose to obtain conventional channel-order record data.

[0100] (12) Denoise through subsequent data processing to obtain the final speed-sensing demodulation phase data.

[0101] (13) Resample the data according to actual needs to provide speed-type fiber optic sensing data for subsequent actual signal processing.

[0102] Figure 2 Shows the initial phase of IQ demodulation of the fiber optic IQ signal; Figure 3 Shows the record after displacement phase demodulation of the fiber optic IQ signal; Figure 4 Shows the record after speed phase demodulation of the fiber optic IQ signal. Combining Figures 2 to 4 It can be seen that after the processing of this method, the phase information of the fiber optic acquisition data represents the speed-sensing response information, and fully retains the low-frequency and low wavenumber information, and can achieve consistency with the wave field acquired by traditional speed-type detectors.

[0103] In addition, the implementation environment of this embodiment includes at least one terminal and a server, and this method is executed on the terminal or the server respectively. The terminal and the server can be communicatively connected to achieve interactive transmission of information.

[0104] Among them, the terminal can be any electronic product that can perform human-computer interaction with the user in one or more ways such as keyboard, touchpad, touch screen, voice interaction, etc., such as a PC (Personal Computer), a PPC (Pocket Personal Computer), a tablet computer, etc.

[0105] The server can be a single server, or a server cluster composed of multiple servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN (Content Delivery Network), and big data and artificial intelligence platforms.

[0106] The second aspect of the embodiment of the present invention also provides a distributed speed-sensing phase demodulation device, see Figure 5 , the phase demodulation device includes: an initial phase and amplitude determination unit 101, a phase decoupling operation unit 102, a speed-sensing determination unit 103, a coherent fading noise suppression unit 104, a phase unwrapping processing unit 105, and a subsequent processing unit 106.

[0107] An initial phase and amplitude determination unit 101 for determining the initial phase ω of IQ demodulation based on the IQ signal 0 (i, j) and the IQ signal amplitude A(i, j).

[0108] A phase decoupling operation unit 102 for performing a phase decoupling operation on the initial phase ω of IQ demodulation 0 (i, j), and sequentially subtracting from the initial phase ω of IQ demodulation 0 (i, j) the initial phase of the receiving point at the output position of the fiber optic sensing signal The initial phase of the laser pulse and the optical path integral phase j×k(i) to obtain the displacement sensing phase

[0109] A velocity sensing determination unit 103 for performing a time difference operation on the displacement sensing phase to obtain velocity-type sensing data.

[0110] A coherent fading noise suppression unit 104 for discriminating the coherent fading positions in the velocity-type sensing data based on the IQ signal amplitude, and using linear interpolation of adjacent normal points to eliminate the influence of coherent fading to obtain the velocity-type sensing data after coherent fading noise suppression.

[0111] A phase unwrapping processing unit 105 for performing phase unwrapping on the velocity-type sensing data after coherent fading noise suppression to obtain the velocity-type sensing data after unwrapping.

[0112] A subsequent processing unit 106 for transposing the velocity-type sensing data after unwrapping into trace-order recorded data and performing denoising through subsequent data processing to obtain the final velocity sensing demodulation phase data.

[0113] Furthermore, in a possible implementation manner, the phase decoupling operation unit 102 may include: a receiving point initial phase determination module, a first decoupled phase determination module, a laser pulse initial phase and linear change factor determination module, an optical path integral phase determination module, a second decoupled phase determination module, a third decoupled phase determination module, and a displacement sensing phase determination module.

[0114] Among them, the receiving point initial phase determination module is used to select a plurality of time sampling values for point-by-point statistical analysis at the output position of the j-th fiber optic sensing signal without an external acoustic wave signal to obtain the initial phase of the receiving point at the output position of the j-th fiber optic sensing signal

[0115] The first decoupled phase determination module is used to subtract from the initial phase ω of IQ demodulation at the output position of the j-th fiber optic sensing signal at the i-th sampling moment 0 (i, j) the initial phase of the receiving point at the output position of the j-th fiber optic sensing signal Obtain the first decoupled phase ω of the output position of the j-th fiber optic sensing signal at the i-th sampling moment 1 (i, j).

[0116] A laser pulse initial phase and linear change factor determination module, which is used to determine the initial phase of the laser pulse at the i-th sampling moment based on the linear relationship between the first decoupled phase at the i-th sampling moment and the change of the output position of the fiber optic sensing signal And the phase linear change factor k(i) at the i-th sampling moment.

[0117] An optical path integral phase determination module, which is used to determine the optical path integral phase j×k(i) of the output position of the j-th fiber optic sensing signal at the i-th sampling moment based on the phase linear change factor k(i) at the i-th sampling moment.

[0118] A second decoupled phase determination module, which is used to subtract the initial phase of the laser pulse from the first decoupled phase ω 1 (i, j) to obtain the second decoupled phase ω of the output position of the j-th fiber optic sensing signal at the i-th sampling moment (i, j). 2 (i, j).

[0119] A third decoupled phase determination module, which is used to subtract the optical path integral phase j×k(i) from the second decoupled phase ω 2 (i, j) to obtain the third decoupled phase ω of the output position of the j-th fiber optic sensing signal at the i-th sampling moment 3 (i, j).

[0120] A displacement sensing phase determination module, which is used to determine the third decoupled phase ω 3 (i, j) as the displacement sensing phase of the output position of the j-th fiber optic sensing signal at the i-th sampling moment

[0121] It should be noted that when the above-mentioned device realizes its functions, only the above-mentioned division of each functional module is used for illustration. In actual applications, the above functions can be allocated to different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the device provided in the above embodiment and the method provided in the above embodiment belong to the same concept, and the specific implementation process can be seen in the method embodiment, which will not be repeated here.

[0122] An embodiment of the present invention also provides an electronic device. See Figure 6, the electronic device includes a processor 201 and a memory 202. At least one computer program is stored in the memory, and the at least one computer program is loaded and executed by one or more of the above-mentioned processors, so that the processor implements the distributed speed sensing phase demodulation method in the above-mentioned embodiments.

[0123] Of course, the electronic device may also have components such as a wired or wireless network interface, a keyboard, and an input / output interface for input / output. The electronic device may also include other components for implementing various functions of the device, which will not be elaborated here.

[0124] An embodiment of the present invention also provides a computer-readable storage medium. At least one program code is stored in the computer-readable storage medium, and the program code is loaded and executed by a processor, so that a computer implements the distributed speed sensing phase demodulation method in the above-mentioned embodiments.

[0125] Optionally, the computer-readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a compact disc read-only memory (CD-ROM), magnetic tape, a floppy disk, and an optical disc data storage device, etc. Those skilled in the art can understand that all or part of the steps in implementing the method of the above embodiments can be completed by a program instructing relevant hardware. The program is stored in a storage medium and includes several instructions for causing a single-chip microcomputer, a chip, or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The foregoing storage media include: USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs, etc., which can store program codes.

[0126] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0127] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination manners.

[0128] In addition, any combination can be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should equally be regarded as the content disclosed by the present invention.

Claims

1. A distributed velocity sensing phase demodulation method, characterized in that, the phase demodulation method includes: determining an IQ demodulation initial phase and an IQ signal amplitude based on an IQ signal; performing a phase decoupling operation on the IQ demodulation initial phase, and successively subtracting a receiving point initial phase, a laser pulse initial phase, and an optical path integration phase at the output position of the fiber optic sensing signal from the IQ demodulation initial phase to obtain a displacement sensing phase; performing a time difference operation on the displacement sensing phase to obtain velocity-type sensing data; determining coherent fading positions in the velocity-type sensing data based on the IQ signal amplitude, and using linear interpolation between adjacent normal points to eliminate the influence of coherent fading to obtain velocity-type sensing data after coherent fading noise suppression; performing phase unwrapping on the velocity-type sensing data after coherent fading noise suppression to obtain unwrapped velocity-type sensing data; transposing the unwrapped velocity-type sensing data into trace-order recorded data, and performing denoising through subsequent data processing to obtain final velocity sensing demodulation phase data.

2. The distributed velocity sensing phase demodulation method according to claim 1, characterized in that, the performing a phase decoupling operation on the IQ demodulation initial phase, and successively subtracting a receiving point initial phase, a laser pulse initial phase, and an optical path integration phase at the output position of the fiber optic sensing signal from the IQ demodulation initial phase to obtain a displacement sensing phase includes: For the j-th optical fiber sensing signal output position without an external acoustic wave signal, a number of time sampling values are selected for point-by-point statistical analysis to obtain the initial phase of the receiving point at the j-th optical fiber sensing signal output position The initial phase ω of IQ demodulation at the output position of the j-th fiber optic sensing signal at the i-th sampling moment 0 Subtract the initial phase of the receiving point at the output position of the j-th fiber optic sensing signal from (i, j) Obtain the first decoupled phase ω(i, j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment 1 (i, j); Determine the initial phase of the laser pulse at the \(i\)-th sampling moment based on the linear relationship between the different first decoupling phases at the \(i\)-th sampling moment and the output position of the fiber optic sensing signal and the phase linear change factor \(k(i)\) at the \(i\)-th sampling moment; determining an optical path integration phase j×k(i) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment based on a phase linear change factor k(i) at the i-th sampling moment; Subtract the initial phase of the laser pulse from the first decoupled phase ω 1 (i, j) to obtain the second decoupled phase ω (i, j) of the output position of the j-th fiber optic sensing signal at the i-th sampling moment; 2 (i, j); From the second decoupled phase ω 2 (i, j), subtract the optical path integral phase j×k(i) to obtain the third decoupled phase ω 3 (i, j) at the j-th optical fiber sensing signal output position at the i-th sampling moment; Determine the third decoupled phase ω 3 (i, j) as the displacement sensing phase at the j-th optical fiber sensing signal output position at the i-th sampling moment 3. The distributed velocity sensing phase demodulation method according to claim 2, characterized in that, performing multiple phase decoupling operations on a third decoupled phase, and determining the finally obtained third decoupled phase as the displacement sensing phase; wherein, in each iterative operation, updating the IQ demodulation initial phase in the current iterative process to the third decoupled phase obtained in the previous iterative operation.

4. The distributed velocity sensing phase demodulation method according to claim 2, characterized in that, the calculation formula for the receiving point initial phase is: in, is the initial phase of the receiving point at the jth optical fiber sensor signal output position, m is the number of time sample points used for statistics at each sensor position before the signal to be measured arrives, that is, when the optical fiber is undisturbed and stationary, ω 0 (i, j) is the IQ demodulation initial phase of the j-th optical fiber sensor signal output position at the i-th sampling moment, i is the sampling time sequence number, and j is the optical fiber sensor signal output position sequence number.

5. The distributed velocity sensing phase demodulation method according to claim 2, characterized in that, Determining the initial phase of the laser pulse at the \(i\)-th sampling moment based on the linear relationship between different first decoupling phases at the \(i\)-th sampling moment and the output position of the fiber optic sensing signal and the phase linear change factor \(k(i)\) at the \(i\)-th sampling moment, including: determining a plurality of first decoupled phases corresponding to different output positions of the fiber optic sensing signal at the i-th sampling moment; performing multi-point linear fitting on the plurality of first decoupled phases corresponding to different output positions of the fiber optic sensing signal at the i-th sampling moment to obtain a linear fitting relationship between the first decoupled phase at the i-th sampling moment and the output position of the fiber optic sensing signal; Determine the intercept of the linear fitting relationship as the initial phase of the laser pulse at the i-th sampling moment Determine the slope of the linear fitting relationship as the phase linear change factor k(i) at the i-th sampling moment.

6. The distributed velocity sensing phase demodulation method according to claim 2, characterized in that, the calculation formula for the velocity-type sensing data is: Among them, is the velocity-type sensing data at the j-th optical fiber sensing signal output position at the i-th sampling moment, is the displacement sensing phase at the j-th optical fiber sensing signal output position at the i-th sampling moment, is the displacement sensing phase at the j-th optical fiber sensing signal output position at the (i + 1)-th sampling moment.

7. A distributed velocity sensing phase demodulation device, characterized in that, the phase demodulation device includes: an initial phase and amplitude determination unit, a phase decoupling operation unit, a velocity sensing determination unit, a coherent fading noise suppression unit, a phase unwrapping processing unit, and a subsequent processing unit; the initial phase and amplitude determination unit is configured to determine an IQ demodulation initial phase and an IQ signal amplitude based on an IQ signal; A phase decoupling operation unit is configured to perform a phase decoupling operation on the initial phase of IQ demodulation, and successively subtract the initial phase of the receiving point at the output position of the fiber optic sensing signal, the initial phase of the laser pulse, and the optical path integral phase from the initial phase of IQ demodulation to obtain the displacement sensing phase; A velocity sensing determination unit is configured to perform a time difference operation on the displacement sensing phase to obtain velocity-type sensing data; A coherent fading noise suppression unit is configured to determine the coherent fading position in the velocity-type sensing data based on the amplitude of the IQ signal, and use linear interpolation of adjacent normal points to eliminate the influence of coherent fading to obtain the velocity-type sensing data after coherent fading noise suppression; A phase unwrapping processing unit is configured to perform phase unwrapping on the velocity-type sensing data after coherent fading noise suppression to obtain the velocity-type sensing data after unwrapping; A subsequent processing unit is configured to transpose the velocity-type sensing data after unwrapping into trace-order recorded data, and perform denoising through subsequent data processing to obtain the final velocity sensing demodulation phase data.

8. The distributed velocity sensing phase demodulation device according to claim 7, wherein, the phase decoupling operation unit includes: a receiving point initial phase determination module, a first decoupling phase determination module, a laser pulse initial phase and linear change factor determination module, an optical path integral phase determination module, a second decoupling phase determination module, a third decoupling phase determination module, and a displacement sensing phase determination module; The receiving point initial phase determination module is used to select a number of time sampling values for point-by-point statistical analysis at the output position of the j-th fiber optic sensing signal without an external acoustic wave signal, and obtain the receiving point initial phase at the output position of the j-th fiber optic sensing signal The first decoupling phase determination module is used to subtract the initial phase of the receiving point at the output position of the j-th fiber optic sensing signal from the IQ demodulation initial phase ω 0 (i, j) to obtain the first decoupling phase ω at the output position of the j-th fiber optic sensing signal at the i-th sampling moment 1 (i, j); The laser pulse initial phase and linear change factor determination module is used to determine the laser pulse initial phase at the i-th sampling moment based on the linear relationship between the first decoupled phase at the i-th sampling moment and the output position of the fiber optic sensing signal and the phase linear change factor k(i) at the i-th sampling moment; The optical path integral phase determination module is configured to determine the optical path integral phase j×k(i) of the j-th fiber optic sensing signal output position at the i-th sampling moment based on the phase linear change factor k(i) at the i-th sampling moment; The second decoupling phase determination module is configured to subtract the initial phase of the laser pulse from the first decoupling phase ω 1 (i, j) to obtain the second decoupling phase ω (i, j) at the output position of the jth fiber optic sensing signal at the ith sampling moment; 2 (i, j); The third decoupling phase determination module is configured to subtract the optical path integral phase j×k(i) from the second decoupling phase ω 2 (i,j) to obtain the third decoupling phase ω 3 (i,j) at the j-th optical fiber sensing signal output position at the i-th sampling moment; A displacement sensing phase determination module, which is used to determine the third decoupled phase ω 3 (i, j) as the displacement sensing phase at the output position of the j-th fiber optic sensing signal at the i-th sampling moment 9. An electronic device, wherein, the electronic device includes a processor and a memory, and at least one computer program is stored in the memory, and the at least one computer program is loaded and executed by one or more of the above-mentioned processors so that the processor executes the distributed velocity sensing phase demodulation method according to any one of claims 1 to 6.

10. A computer-readable storage medium, wherein, the computer-readable storage medium stores at least one program code, and the program code is loaded and executed by a processor so that a computer executes the distributed velocity sensing phase demodulation method according to any one of claims 1 to 6.

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