Distributed displacement sensing phase demodulation method, device and equipment

Abstract

The invention provides a distributed displacement 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; phase decoupling operation is carried out on the IQ demodulation initial phase, the initial phase of the optical fiber sensing signal output position, the laser pulse initial phase and the transmission process path accumulation phase are sequentially subtracted from the IQ demodulation initial phase, and a displacement sensing phase to be measured is obtained; performing phase unwinding processing on the displacement sensing phase to be measured to obtain an unwound displacement sensing phase to be measured; calculating displacement sensing data according to the unwound displacement sensing phase to be measured; and performing de-noising processing on the displacement sensing data. Through the method provided by the invention, displacement sensing phase demodulation can be realized, and the distributed displacement response information of the to-be-measured wave field can be recovered.

Description

Technical Field

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

[0002] Fiber optic distributed acoustic sensing technology (DAS) uses the Rayleigh backscattering of optical fibers to obtain vibration information around the optical fibers 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. This technology has been widely used in well seismic data acquisition, dam safety monitoring, perimeter security, pipeline monitoring, etc. Fiber optic DAS technology mainly utilizes the Rayleigh backscattering generated when a laser propagates in an optical fiber. When the medium around the optical fiber vibrates, the Rayleigh scattering will also change accordingly. By coherent detection and phase demodulation of this optical signal, the vibration wave field information or strain information of the medium can be obtained. Since generally the phase difference between adjacent points at the gauge length is used as the demodulated phase output, its output is actually local strain. When differentiating with respect to time before the phase difference output, its output is the local strain rate.

[0003] Fiber optic DAS generally uses a phase-sensitive optical time domain reflectometer to obtain 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. The current phase demodulation methods mainly overcome the non-linear effect and improve the signal-to-noise ratio by taking the difference of phases within the gauge length and local averaging. However, this phase demodulation method will lose the low wavenumber wave field information and cannot reduce the noise level to an ideal level. Many experts at home and abroad are committed to the research on high signal-to-noise ratio phase demodulation.

[0004] Investigations show that there is currently no phase demodulation method based on fiber optic distributed displacement sensing, and the existing distributed acoustic sensing phase demodulation methods can only achieve velocity sensing phase demodulation, and there are still many deficiencies in the practical application of the phase demodulation results. Therefore, the need to accurately and efficiently perform displacement sensing phase demodulation down to zero frequency while maintaining broadband wave field information is extremely urgent. Summary of the Invention

[0005] Aiming at the technical problem that there is currently no phase demodulation method based on fiber optic distributed displacement sensing in the prior art, the present invention provides a distributed displacement sensing phase demodulation method. By using this method, displacement sensing phase demodulation can be achieved, and the distributed displacement response information of the wave field to be measured can be restored.

[0006] To achieve the above object, a first aspect of the present invention provides a distributed displacement sensing phase demodulation method, and the phase demodulation method includes the following steps: determining the IQ demodulation initial phase ω 0 (i, j) and the IQ signal amplitude A(i, j); performing a phase decoupling operation on the IQ demodulation initial phase ω 0 (i, j), and successively subtracting the initial phase of the optical fiber sensing signal output position, 0 the initial phase of the laser pulse, and the path cumulative phase during the transmission process from the IQ demodulation initial phase ω to obtain the displacement sensing phase to be measured performing a phase unwrapping process on the displacement sensing phase to be measured to obtain the unwrapped displacement sensing phase to be measured; calculating displacement sensing data according to the unwrapped displacement sensing phase to be measured; determining the coherent fading position in the displacement 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 displacement sensing data after suppressing coherent fading noise; transposing the displacement sensing data after suppressing coherent fading noise into trace-order recorded data, and performing denoising through subsequent data processing to obtain the final displacement sensing demodulation phase data.

[0007] In an exemplary embodiment of the present invention, the performing a phase decoupling operation on the IQ demodulation initial phase ω 0 (i, j), and successively subtracting the initial phase of the optical fiber sensing signal output position, 0 (i, j), the initial phase of the laser pulse, and the path cumulative phase during the transmission process from the IQ demodulation initial phase ω to obtain the displacement sensing phase to be measured 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 j-th optical fiber sensing signal output position subtracting the initial phase of the j-th optical fiber sensing signal output position 0 from the IQ demodulation initial phase ω (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 based on the linear relationship between different first decoupled phases at the i-th sampling moment and the change of the optical fiber sensing signal output position and the linearly time-varying factor k(i) at the i-th sampling moment; based on the linearly time-varying factor k(i) at the i-th sampling moment, determine the cumulative phase of the transmission process path at the output position of the j-th fiber optic sensing signal at the i-th sampling moment Subtract the initial laser pulse phase from the first decoupled phase ω 1 (i,j) to obtain the second decoupled phase ω 2 (i,j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; subtract the cumulative phase of the transmission process path from the second decoupled phase ω 2 (i,j) to obtain the third decoupled phase v 3 (i,j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; determine the third decoupled phase ω 3 (i,j) as the displacement sensing phase to be measured at the output position of the j-th fiber optic sensing signal 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 decoupled phase, and the finally obtained third decoupled phase through the operations is determined as the displacement sensing phase to be measured; wherein, during each iterative operation, update the initial IQ demodulation phase in the current iterative process to the third decoupled phase obtained in the previous iterative operation.

[0009] In an exemplary embodiment of the present invention, the calculation formula for the initial phase of the output position of the fiber optic sensing signal can be:

[0010]

[0011] wherein is the initial phase of the output position of the j-th fiber optic sensing signal, m is the number of time samples at each sensing position before the signal to be measured arrives, 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, i is the sampling time sequence number, and j is the fiber optic sensing signal output position sequence number.

[0012] In an exemplary embodiment of the present invention, determine the initial laser pulse phase 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 with the output position of the fiber optic sensing signal The linear change factor k(i) with respect to time at the i-th sampling moment may include: determining a plurality of first decoupled phases corresponding to different optical fiber sensing signal output positions at the i-th sampling moment; performing multi-point linear fitting on the plurality of first decoupled phases corresponding to different optical fiber sensing signal output positions 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 optical fiber sensing signal output position; and determining 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 linear change factor k(i) with respect to time at the i-th sampling moment.

[0013] In an exemplary embodiment of the present invention, the calculation formula for the displacement sensing data may be:

[0014]

[0015] where D(i,j) is the displacement sensing data at the j-th optical fiber sensing signal output position at the i-th sampling moment, is the displacement sensing phase to be measured at the j-th optical fiber sensing signal output position at the i-th sampling moment, λ is the wavelength of the laser pulse, n is the refractive index of the optical fiber, and the value of n is generally 1.46, C ε is the refractive index strain parameter, and for different optical fibers, C ε takes values between -0.16 and -0.63.

[0016] The second aspect of the present invention provides a distributed displacement sensing phase demodulation device. The phase demodulation device may include: an initial phase and amplitude determination unit, a phase decoupling operation unit, a phase unwrapping processing unit, a displacement sensing determination unit, a coherent fading noise suppression unit, and a subsequent processing unit; the initial phase and amplitude determination unit is configured to determine the IQ demodulation initial phase and the IQ signal amplitude based on the IQ signal; the phase decoupling operation unit is configured to perform phase decoupling operation on the IQ demodulation initial phase, and sequentially subtract the initial phase of the optical fiber sensing signal output position, the initial phase of the laser pulse, and the path accumulation phase during the transmission process from the IQ demodulation initial phase to obtain the displacement sensing phase to be measured; the phase unwrapping processing unit is configured to perform phase unwrapping processing on the displacement sensing phase to be measured to obtain the unwrapped displacement sensing phase to be measured; the displacement sensing determination unit is configured to calculate the displacement sensing data according to the unwrapped displacement sensing phase to be measured; the coherent fading noise suppression unit is configured to determine the coherent fading position in the displacement sensing data based on the IQ signal amplitude, and use linear interpolation between adjacent normal points to eliminate the influence of coherent fading to obtain the displacement sensing data after coherent fading noise suppression; the subsequent processing unit is configured to transpose the displacement sensing data after coherent fading noise suppression into trace-order recorded data, and perform denoising through subsequent data processing to obtain the final displacement sensing demodulation phase data.

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

[0018] In a third aspect of the present invention, an electronic device is provided, which 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-mentioned processors, so that the processor executes the above-mentioned distributed displacement sensing phase demodulation method.

[0019] In a fourth aspect of the present invention, a computer-readable storage medium is provided. 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 above-mentioned distributed displacement 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 distributed displacement sensing phase demodulation method provided by the present invention restores the distributed displacement response information of the wave field to be measured through a series of phase decoupling operations on the initial phase of IQ demodulation, and fully preserves the low-frequency and low-wave number information, which can improve the actual application effect of fiber optic sensing;

[0022] (2) The present invention fills the technical gap that there is no phase demodulation method based on fiber optic distributed displacement sensing in the prior art. In actual production applications, it is of great significance for improving the quality of fiber optic sensing data acquisition, protecting low-frequency and low-wave number wave field information, and matching and processing with traditional detectors.

[0023] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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, 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:

[0025] Figure 1 is a flowchart of the distributed displacement sensing phase demodulation method provided by the embodiment of the present invention;

[0026] Figure 2 is an initial phase diagram of IQ demodulation of the fiber optic IQ signal provided by the embodiment of the present invention;

[0027] Figure 3 is a recorded diagram after displacement phase demodulation of the fiber optic IQ signal provided by the embodiment of the present invention;

[0028] Figure 4 is an unwound recorded diagram after displacement phase demodulation provided by the embodiment of the present invention;

[0029] Figure 5The transposed normal trace record diagram provided by the embodiment of the present invention;

[0030] Figure 6 The structural diagram of the distributed displacement sensing phase demodulation device provided by the embodiment of the present invention;

[0031] Figure 7 The structural diagram of the electronic device provided by the embodiment of the present invention.

[0032] Description of reference numerals

[0033] 101 - Initial phase and amplitude determination unit, 102 - Phase decoupling operation unit, 103 - Phase unwrapping processing unit, 104 - Displacement sensing determination unit, 105 - Coherent fading noise suppression 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 convenient 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 defined 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 order to solve the technical problem of the lack of a phase demodulation method based on fiber optic distributed displacement sensing in the prior art, the present invention provides a distributed displacement phase demodulation method. This phase demodulation method realizes displacement sensing phase demodulation by gradually decoupling the initial phase of each fiber sensing position, the initial phase of the laser pulse, the accumulated phase of the transmission path, and the signal to be measured included in the initial demodulation phase.

[0038] The following will describe the present invention in detail with reference to the accompanying drawings and in combination with embodiments.

[0039] Please refer to Figure 1 , on the one hand, the embodiment of the present invention provides a distributed displacement sensing phase demodulation method, and this method includes the following steps:

[0040] Step S101: Determine the initial IQ demodulation phase ω based on the IQ signal 0 (i, j) and the IQ signal amplitude A(i, j).

[0041] Specifically, use an optical fiber distributed acoustic sensing acquisition instrument Connected to the optical fiber coupled to the environment to be measured, emit narrow linewidth and high coherence optical pulses at a certain frequency, and the IQ signals at different times and different observation points can be obtained through the IQ demodulation device. The IQ signals are the in-phase signal I(i, j) and the quadrature signal Q(i, j) respectively. After various corrections are made to the IQ signals, IQ phase demodulation is performed. Among them, i represents the i-th sampling time serial number, and j represents the j-th optical fiber sensing signal output position serial number.

[0042] According to the above IQ signals, the initial IQ demodulation phase ω 0 (i, j) and the IQ signal amplitude A(i, j) can be calculated, and the specific representation is as follows:

[0043]

[0044]

[0045] In the formula, 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; Q(i, j) is the quadrature signal at the j-th optical fiber sensing signal output position at the i-th sampling moment; I(i, j) is the in-phase signal at the j-th optical fiber sensing signal output position at the i-th sampling moment; A(i, j) is the IQ signal amplitude at the j-th optical fiber sensing signal output position at the i-th sampling moment.

[0046] Step S102: Perform phase decoupling operation on the initial IQ demodulation phase ω 0 (i, j), and successively subtract the initial phase of the optical fiber sensing signal output position 0 from the initial IQ demodulation phase ω The initial phase of the laser pulse and the accumulated phase of the transmission process path to obtain the displacement sensing phase to be measured

[0047] Specifically, the optical fiber distributed sensing acquisition instrument is an instrument with an optical time domain reflectometer based on phase sensitivity. The initial IQ demodulation phase ω corresponding to the optical fiber sensing signal output position j at the i-th sampling moment 0 includes four parts, which are the initial phases of each optical fiber sensing signal output position The initial phase of the laser pulse Accumulated phase of the transmission process path and the displacement phase of the signal to be measured That is:

[0048]

[0049] In the formula, 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 displacement sensing phase to be measured at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; is the initial phase at the output position of the j-th fiber optic sensing signal; is the initial phase of the laser pulse at the i-th sampling moment; is the accumulated phase of the transmission process path at the output position of the j-th fiber optic sensing signal at the i-th sampling moment.

[0050] Step S103: Perform phase unwrapping processing on the displacement sensing phase to be measured to obtain the unwrapped displacement sensing phase to be measured.

[0051] Step S104: Calculate and obtain displacement sensing data based on the unwrapped displacement sensing phase to be measured.

[0052] Specifically, the required displacement sensing data D(i, j) can be calculated using the following formula.

[0053]

[0054] In the formula, D(i, j) is the displacement 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 to be measured at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; λ is the wavelength of the laser pulse, generally 1550 nm; n is the refractive index of the optical fiber, and its value is generally 1.46; C ε is the refractive index strain parameter, and for different optical fibers, its value is generally between -0.16 and -0.63.

[0055] Step S105: Based on the amplitude of the IQ signal, determine the coherent fading position in the displacement sensing data, and use linear interpolation between adjacent normal points to eliminate the influence of coherent fading to obtain the displacement sensing data after suppressing coherent fading noise.

[0056] Step S106: Transpose the displacement sensing data after suppressing coherent fading noise into trace-order recorded data, and perform denoising through subsequent data processing to obtain the final displacement sensing demodulation phase data.

[0057] Furthermore, in a possible implementation manner, in step S102, for the initial IQ demodulation phase ω0 Perform phase decoupling operation on (i,j), and subtract the initial phase of the optical fiber sensing signal output position from the initial phase ω of IQ demodulation in sequence 0 from the initial phase of the optical fiber sensing signal output position Initial phase of laser pulse and the accumulated phase of the transmission process path to obtain the displacement sensing phase to be measured The process can include but is not limited to the following sub-steps S1021 to sub-step S1027.

[0058] Sub-step S1021: Select several time sampling values for point-by-point statistical analysis at the j-th optical fiber sensing signal output position without external acoustic signals, and obtain the initial phase of the j-th optical fiber sensing signal output position

[0059] Specifically, the initial phase of the j-th optical fiber sensing signal output position The calculation formula is:

[0060]

[0061] In formula (6), is the initial phase of the j-th optical fiber sensing signal output position; m is the number of time sample points selected before the signal to be measured arrives at each sensing position, that is, the number of time sample points used to statistically analyze the initial phase of the optical fiber sensing signal output position when the optical fiber is in a stationary state; ω 0 (i,j) is the initial phase of IQ demodulation at the j-th optical fiber sensing signal output position at the i-th sampling moment; i is the sampling time serial number; j is the serial number of the optical fiber sensing signal output position.

[0062] Sub-step S1022: Subtract the initial phase of the j-th optical fiber sensing signal output position from the initial phase ω 0 (i,j) of the j-th optical fiber sensing signal output position at the i-th sampling moment to obtain the first decoupled phase ω 1 (i,j) of the j-th optical fiber sensing signal output position at the i-th sampling moment.

[0063] That is, the calculation formula for the first decoupled phase ω 1 (i,j) of the j-th optical fiber sensing signal output position at the i-th sampling moment is:

[0064]

[0065] In formula (6), ω 1 (i,j) is the first decoupled phase of the j-th optical fiber sensing signal output position at the i-th sampling moment; 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; is the initial phase at the j-th optical fiber sensing signal output position.

[0066] Sub-step S1023: Determine the initial laser pulse phase at the i-th sampling moment based on the linear relationship between different first decoupling phases at the i-th sampling moment and the change of the optical fiber sensing signal output position and the phase linear change factor k(i) at the i-th sampling moment.

[0067] Since 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 should satisfy the following relational expression:

[0068]

[0069] Therefore, combining Equation (6) and Equation (7), it can be known that the first decoupling phase ω 1 (i,j) after eliminating the influence of the initial phase at the optical fiber sensing signal output position and the initial laser pulse phase as well as the accumulated phase of the transmission path should satisfy the following relational expression:

[0070]

[0071] Here, if it is assumed that the mean value in the fitting segment is zero, that is, it has no influence on the calculation of the fitting parameters. Then, the first decoupling phase ω 1 (i,j) at the i-th sampling moment and the optical fiber sensing signal output position j will form a linear function relationship of the first order, that is:

[0072]

[0073] At this time, the linear fitting relational expression of different first decoupling phases at the i-th sampling moment with respect to the change of the optical fiber sensing signal output position j can be obtained by performing multi-point linear fitting on the curve of the first decoupling phase ω 1 (i,j) at the i-th sampling moment with respect to the change of the optical fiber sensing signal output position j. The intercept of this linear fitting relational expression is the initial laser pulse phase at the i-th sampling moment The slope of this linear fitting relational expression is the linear change factor k(i) with respect to time at the i-th sampling moment.

[0074] In addition, it should be noted that in order to eliminate as much as possible Regarding the influence on fitting accuracy, the far end of the optical fiber with a weaker measured signal and a later arrival time should be selected as the fitting segment. To ensure fitting accuracy, the fitting segment cannot be too short and generally should reach more than one-fourth of the optical fiber length. The influence of phase winding should be considered during fitting and unwrapping processing should be performed.

[0075] Sub-step S1024: Based on the phase linear change factor k(i) at the i-th sampling moment, determine the cumulative phase of the transmission process path at the output position of the j-th optical fiber sensing signal at the i-th sampling moment

[0076] Specifically, by multiplying the phase linear change factor k(i) at the i-th sampling moment by the output position j of the optical fiber sensing signal, the cumulative phase of the transmission process path at the output position of the j-th optical fiber sensing signal at the i-th sampling moment can be obtained. That is:

[0077]

[0078] In the formula, is the cumulative phase of the transmission process path at the output position of the j-th optical fiber sensing signal at the i-th sampling moment; k(i) is the factor that changes linearly with time at the i-th sampling moment.

[0079] Sub-step S1025: Subtract the initial phase of the laser pulse at the i-th sampling moment from the first decoupled phase ω 1 (i, j) at the output position of the j-th optical fiber sensing signal at the i-th sampling moment to obtain the second decoupled phase ω 2 (i, j) at the output position of the j-th optical fiber sensing signal at the i-th sampling moment.

[0080] Sub-step S1026: Subtract the cumulative phase of the transmission process path at the output position of the j-th optical fiber sensing signal from the second decoupled phase ω 2 (i, j) at the output position of the j-th optical fiber sensing signal at the i-th sampling moment to obtain the third decoupled phase ω 3 (i, j) at the output position of the j-th optical fiber sensing signal at the i-th sampling moment.

[0081] Sub-step S1027: Determine the third decoupled phase ω 3 (i, j) at the output position of the j-th optical fiber sensing signal at the i-th sampling moment as the displacement sensing phase to be measured at the output position of the j-th optical fiber sensing signal at the i-th sampling moment

[0082] Further, in a possible implementation manner, to ensure the demodulation accuracy, the above sub-steps S1021 to S1027 can be iteratively performed multiple times, and the third decoupled phase finally obtained through the operation is determined as the final displacement sensing phase to be measured. Wherein, during each iterative operation, the IQ demodulation initial phase ω 0 (i,j) is updated to the third decoupled phase ω 3 (i,j) obtained in the previous iterative operation.

[0083] To verify the effectiveness and practicality of the distributed displacement sensing phase demodulation method of the present invention, taking the IQ data collected from an actual optical fiber of an oil well as an example, the above distributed displacement sensing phase demodulation method is used to perform displacement sensing phase demodulation on the IQ data. First, the optical fiber is laid in the well, and an optical fiber distributed acoustic sensing receiving instrument is used to connect the optical fiber from the upper part to collect

[0084] the IQ data of the instrument. Then, displacement sensing phase demodulation processing is performed on the IQ data collected from the actual optical fiber of a certain oil well, which specifically may include the following processing procedures: First, the optical fiber is laid in the well, and an optical fiber distributed acoustic sensing receiving instrument is used to connect the optical fiber from the upper part to collect the IQ data of the instrument. Then, displacement sensing phase demodulation processing is performed on the IQ data collected from the actual optical fiber of a certain oil well, which specifically may include the following processing procedures:

[0085] (1) Perform imbalance correction on the output I(i,j) and Q(i,j) of the IQ signals at different times and different observation points obtained to ensure the orthogonality of the IQ signals.

[0086] (2) Calculate the IQ demodulation initial phase ω 0 (i,j) of the IQ signal through formula (1), and calculate the IQ signal amplitude A(i,j) of the IQ signal through formula (2).

[0087] (3) Select m time sampling values for each optical fiber sensing output position without external acoustic signals for point-by-point statistical analysis to obtain the initial phase of Rayleigh backscattering superposition within the optical pulse width range at the optical fiber sensing signal output position j

[0088] wherein, m is the number of time sample points selected before the signal to be measured arrives at each sensing position, that is, the number of time sample points used to statistically analyze the initial phase of the optical fiber sensing signal output position when the optical fiber is in a stationary state.

[0089] (4) After subtracting the initial phase corresponding to each optical fiber sensing signal output position from the IQ demodulation initial phase ω 0 (i,j), the first decoupled phase ω 1 (i,j) that eliminates the influence of the initial phase at each sensing position is obtained.

[0090] (5) Using the first decoupled phase ω corresponding to each sensing position at the i sampling moment​1 (i, j) is linearly fitted with each optical fiber sensing signal output position j to obtain the laser pulse phase at the i - sampling moment. And the phase linear change factor k(i).

[0091] 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 at the i - sampling moment with respect to the sensing position. After multi - point linear fitting, the slope and intercept are obtained. This intercept is the laser pulse phase at the i - sampling moment. The slope is the phase linear change factor k(u) at the i - sampling moment.

[0092] (6) Calculate the path - accumulated phase during the transmission process through formula (10).

[0093] (7) Subtract the initial phase of the laser pulse 0 corresponding to each output position from the initial phase ω of the IQ demodulation at the corresponding positions in sequence from ω (i, j) and the path - accumulated phase during the transmission process to obtain the displacement sensing phase to be measured.

[0094] (8) To ensure the demodulation accuracy, use to replace ω 0 (i, j) and repeat steps (3) to (7).

[0095] (9) Perform phase unwrapping on the IQ displacement phase demodulation data obtained from the above steps, and calculate the required displacement sensing data D(i, j) using formula (4).

[0096] (10) Use the amplitude of the IQ signal to judge the position of the fading noise and eliminate the influence of coherent fading.

[0097] (11) Repeat steps (1) to (10) for all I / Q signals of all records to be demodulated, and transpose to obtain the trace - order record required for subsequent processing. After completing the above steps, the IQ displacement sensing phase demodulation of the optical fiber acquisition data is completed.

[0098] (12) To further eliminate the residual phase low wavenumber noise, zero wavenumber processing is performed on the subsequent data to obtain the final displacement sensing demodulation phase data.

[0099] (13) Data resampling is performed according to actual needs, and actual subsequent processing and applications are carried out using existing technologies.

[0100] Figure 2 shows the initial phase of the 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 unwrapping the displacement phase demodulation; Figure 5 shows the record of the normal trace order after transposition. Combining Figures 2 to 5 It can be seen that after the processing by this method, the phase information of the fiber optic acquisition data represents the displacement sensing response information, achieving the purpose of maintaining the full frequency band information and highlighting the effective seismic waves. And this phase demodulation method does not require taking differences according to the gauge length, completely maintaining the frequency characteristics of the signal, significantly improving the data quality, and providing guarantee for subsequent data processing and applications.

[0101] 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 the interactive transmission of information.

[0102] Among them, the terminal can be any electronic product that can perform human-computer interaction with the user through one or more ways such as a keyboard, a touchpad, a touch screen, and voice interaction, such as a PC (Personal Computer), a PPC (Pocket Personal Computer), a tablet computer, etc.

[0103] 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.

[0104] Another aspect of the embodiment of the present invention also provides a distributed displacement sensing phase demodulation device. Refer to Figure 6 , this phase demodulation device includes: an initial phase and amplitude determination unit 101, a phase decoupling operation unit 102, a phase unwrapping processing unit 103, a displacement sensing determination unit 104, a coherent fading noise suppression unit 105, and a subsequent processing unit 106.

[0105] An initial phase and amplitude determination unit 101 is configured to determine the initial phase ω of IQ demodulation based on the IQ signal 0 (i, j) and the amplitude A(i, j) of the IQ signal.

[0106] A phase decoupling operation unit 102 is configured to perform a phase decoupling operation on the initial phase ω of IQ demodulation 0 (i, j), and sequentially subtract from the initial phase ω of IQ demodulation 0 (i, j) the initial phase of the optical fiber sensing signal output position The initial phase of the laser pulse and the accumulated phase of the transmission process path to obtain the displacement sensing phase to be measured

[0107] A phase unwrapping processing unit 103 is configured to perform a phase unwrapping process on the displacement sensing phase to be measured to obtain the unwrapped displacement sensing phase to be measured.

[0108] A displacement sensing determination unit 104 is configured to calculate and obtain displacement sensing data according to the unwrapped displacement sensing phase to be measured.

[0109] A coherent fading noise suppression unit 105 is configured to determine the coherent fading positions in the displacement 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 displacement sensing data after suppressing the coherent fading noise.

[0110] A subsequent processing unit 106 is configured to transpose the displacement sensing data after suppressing the coherent fading noise into trace-order recorded data, and perform denoising through subsequent data processing to obtain the final displacement sensing demodulation phase data.

[0111] Furthermore, in a possible implementation manner, the phase decoupling operation unit 102 may include: an initial phase determination module for the optical fiber sensing signal output position, a first decoupled phase determination module, a laser pulse initial phase and linear change factor determination module, a transmission process path accumulated phase determination module, a second decoupled phase determination module, a third decoupled phase determination module, and a displacement sensing phase determination module.

[0112] Among them, the initial phase determination module for the optical fiber sensing signal output position is configured to select a plurality of time sampling values for point-by-point statistical analysis for the j-th optical fiber sensing signal output position without an external acoustic wave signal to obtain the initial phase of the j-th optical fiber sensing signal output position

[0113] The first decoupled phase determination module is configured to obtain the initial phase ω of IQ demodulation from the j-th optical fiber sensing signal output position at the i-th sampling moment 0Subtract the initial phase of the j-th fiber optic sensing signal output position from (i, j). Obtain the first decoupled phase ω of the j-th fiber optic sensing signal output position at the i-th sampling moment 1 (i, j).

[0114] Laser pulse initial phase and linear change factor determination module, for determining 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 change of the fiber optic sensing signal output position And the linear change factor k(i) with respect to time at the i-th sampling moment.

[0115] Transmission process path cumulative phase determination module, for determining the transmission process path cumulative phase of the j-th fiber optic sensing signal output position at the i-th sampling moment based on the linear change factor k(i) with respect to time at the i-th sampling moment

[0116] Second decoupled phase determination module, for subtracting the laser pulse initial phase from the first decoupled phase ω 1 (i, j) Obtain the second decoupled phase ω of the j-th fiber optic sensing signal output position at the i-th sampling moment 2 (i, j).

[0117] Third decoupled phase determination module, for subtracting the transmission process path cumulative phase from the second decoupled phase ω 2 (i, j) Obtain the third decoupled phase ω of the j-th fiber optic sensing signal output position at the i-th sampling moment 3 (i, j).

[0118] Displacement sensing phase determination module, for determining the third decoupled phase ω 3 (i, j) as the displacement sensing phase to be measured at the j-th fiber optic sensing signal output position at the i-th sampling moment

[0119] It should be noted that when the above-provided 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 as needed, 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 is detailed in the method embodiment, which will not be repeated here.

[0120] An embodiment of the present invention also provides an electronic device. See Figure 7, 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 displacement sensing phase demodulation method in the above-mentioned embodiments.

[0121] 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.

[0122] 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 displacement sensing phase demodulation method in the above-mentioned embodiments.

[0123] 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), a 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 of implementing the method in the above-mentioned embodiments can be completed by a program instructing relevant hardware. The program is stored in a storage medium, including 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 and other media that can store program codes.

[0124] 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 solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0125] 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 methods.

[0126] 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 displacement sensing phase demodulation method, characterized in that, 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 fiber optic sensing signal output position, the initial laser pulse phase, and the accumulated phase of the transmission path from the initial IQ demodulation phase to obtain the displacement sensing phase to be measured; Performing a phase unwrapping process on the displacement sensing phase to be measured to obtain the unwrapped displacement sensing phase to be measured; Calculating displacement sensing data based on the unwrapped displacement sensing phase to be measured; Identifying the coherent fading positions in the displacement 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 displacement sensing data after suppressing coherent fading noise; Transposing the displacement sensing data after suppressing coherent fading noise into trace-order recorded data, and performing denoising through subsequent data processing to obtain the final displacement sensing demodulation phase data.

2. The distributed displacement sensing phase demodulation method according to claim 1, characterized in that, The performing a phase decoupling operation on the initial IQ demodulation phase, and successively subtracting the initial phase of the fiber optic sensing signal output position, the initial laser pulse phase, and the accumulated phase of the transmission path from the initial IQ demodulation phase to obtain the displacement sensing phase to be measured includes: Select a number of time sampling values for point-by-point statistical analysis at the j-th fiber optic sensing signal output position without an external acoustic wave signal, and obtain the initial phase at the j-th fiber optic 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 at the output position of the j-th fiber optic sensing signal from (i, j) Obtain the first decoupled phase ω 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 change in the output position of the fiber optic sensing signal. And the factor k(i) that varies linearly with time at the i-th sampling moment; Determine the cumulative phase of the transmission process path at the output position of the j-th fiber optic sensing signal at the i-th sampling moment based on the time-varying linear 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) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; 2 (i,j); Subtract the cumulative phase of the transmission process path from the second decoupled phase ω 2 (i,j) to obtain the third decoupled phase ω (i,j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; 3 (i,j); Determine the third decoupled phase ω 3 (i, j) as the displacement sensing phase to be measured at the j-th optical fiber sensing signal output position at the i-th sampling moment 3. The distributed displacement sensing phase demodulation method according to claim 2, characterized in that, Performing multiple phase decoupling operations on the third decoupled phase, and determining the third decoupled phase obtained by the final operation as the displacement sensing phase to be measured; wherein, during each iterative operation, updating the initial IQ demodulation phase in the current iterative process to the third decoupled phase obtained by the previous iterative operation.

4. The distributed displacement sensing phase demodulation method according to claim 2, characterized in that, The calculation formula for the initial phase of the fiber optic sensing signal output position is: Among them, is the initial phase of the j-th optical fiber sensing signal output position, m is the number of time sample points used for statistics at each sensing position before the signal to be measured arrives, that is, when the optical fiber is in a static state without disturbance, ω 0 (i, j) is the IQ demodulation initial phase of the j-th optical fiber sensing signal output position at the i-th sampling moment, i is the sampling time sequence number, and j is the optical fiber sensing signal output position sequence number.

5. The distributed displacement 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 factor $k(i)$ that linearly varies with time at the $i$-th sampling moment, including: Determining a plurality of first decoupled phases corresponding to different fiber optic sensing signal output positions at the i-th sampling moment; Performing multi-point linear fitting on the plurality of first decoupled phases corresponding to different fiber optic sensing signal output positions 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 fiber optic sensing signal output position; 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 factor k(i) that linearly changes with time at the i-th sampling moment.

6. The distributed displacement sensing phase demodulation method according to claim 2, characterized in that, The calculation formula for the displacement sensing data is: Among them, D(i,j) is the displacement sensing data at the j-th output position of the fiber optic sensing signal at the i-th sampling moment. is the displacement sensing phase to be measured at the j-th output position of the fiber optic sensing signal at the i-th sampling moment, λ is the wavelength of the laser pulse, n is the refractive index of the optical fiber, and n generally takes a value of 1.

46. C ε is the refractive index strain parameter, and for different optical fibers, C ε takes values between -0.16 and -0.

63.

7. A distributed displacement 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 phase unwrapping process unit, a displacement sensing determination unit, a coherent fading noise suppression unit, and a subsequent processing unit; The initial phase and amplitude determination unit is used to determine the initial IQ demodulation phase and the IQ signal amplitude based on the 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 optical fiber sensing signal output position, the initial phase of the laser pulse, and the accumulated phase of the transmission process path from the initial phase of IQ demodulation to obtain the displacement sensing phase to be measured; A phase unwrapping processing unit is configured to perform a phase unwrapping process on the displacement sensing phase to be measured to obtain the unwrapped displacement sensing phase to be measured; A displacement sensing determination unit is configured to calculate displacement sensing data based on the unwrapped displacement sensing phase to be measured; A coherent fading noise suppression unit is configured to determine the coherent fading position in the displacement 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 displacement sensing data after coherent fading noise suppression; A subsequent processing unit is configured to transpose the displacement sensing data after coherent fading noise suppression into channel-order recorded data, and perform denoising through subsequent data processing to obtain the final displacement sensing demodulation phase data.

8. The distributed displacement sensing phase demodulation device according to claim 7, wherein, the phase decoupling operation unit includes: an initial phase determination module of the optical fiber sensing signal output position, a first decoupling phase determination module, a laser pulse initial phase and linear change factor determination module, a transmission process path accumulated phase determination module, a second decoupling phase determination module, a third decoupling phase determination module, and a displacement sensing phase determination module; The initial phase determination module for the optical fiber sensing signal output position is used to select several time sampling values for point-by-point statistical analysis for the j-th optical fiber sensing signal output position without an external acoustic wave signal, so as to obtain the initial phase of the j-th optical fiber sensing signal output position The first decoupling phase determination module is used to subtract the initial phase of the j-th fiber optic sensing signal output position from the IQ demodulation initial phase ω 0 (i, j) at the j-th fiber optic sensing signal output position at the i-th sampling moment to obtain the first decoupling phase ω 1 (i, j) of the j-th fiber optic sensing signal output position at the i-th sampling moment; 0 (i,j) from the initial phase of the j-th fiber optic sensing signal output position to obtain the first decoupling phase ω 1 1 (i,j); 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 output position of the fiber optic sensing signal and the linearly varying factor k(i) with respect to time at the i-th sampling moment. A transmission process path cumulative phase determination module, which is used to determine the transmission process path cumulative phase of the output position of the j-th fiber optic sensing signal at the i-th sampling moment based on the factor k(i) that varies linearly with time 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 2 (i,j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; The third decoupling phase determination module is used to subtract the cumulative phase of the transmission process path from the second decoupling phase ω 2 (i, j) to obtain the third decoupling phase ω 3 (i, j) at the output position of the j-th fiber optic sensing signal at the i-th sampling moment; A displacement sensing phase determination module, configured to determine the third decoupled phase ω 3 (i, j) as the displacement sensing phase to be measured 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 processors, so that the processor executes the distributed displacement 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 displacement sensing phase demodulation method according to any one of claims 1 to 6.

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