Phase unwrapping method of beat frequency signal, computer equipment and storage medium

Abstract

The invention discloses a phase unwrapping method of a beat frequency signal, computer equipment and a storage medium, and the method is used for carrying out unwrapping processing on phase information obtained by demodulating a sound signal and a vibration signal in a distributed optical fiber sensing system so as to obtain real phase information. According to the method, phase information of an external disturbance signal is obtained through a traditional orthogonal demodulation algorithm, and a winding phase wrapped in # imgabs0 # is obtained through arc tangent operation. The winding phase is converted into the two-dimensional matrix in the space domain direction and the time domain direction, the real phase information can be recovered by performing one-time two-dimensional unwrapping operation on the winding phase through the two-dimensional unwrapping algorithm, and compared with traditional two-time one-dimensional unwrapping, global phase information on the whole space and time domain can be rapidly obtained, and the real phase information can be recovered. The system operation efficiency is improved, the system operation burden is reduced, and the problem of poor system real-time performance caused by large signal data volume and large system operation amount can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of signal processing, and in particular to a phase unwrapping method of a beat frequency signal, a computer device and a storage medium. Background Art

[0002] Phase-sensitive optical time-domain reflectometry fiber optic sensing system is a very powerful technology that can achieve fast response and high sensitivity of fully distributed vibration sensing. Phase-sensitive optical time-domain reflectometry fiber optic sensing system can detect and quantify very small strain changes by simply measuring the optical phase difference of backscattered light from adjacent positions in the optical fiber. It has been applied in many fields such as optical cable construction and maintenance, safety protection, and traffic monitoring.

[0003] In the phase demodulation process of the phase-sensitive optical time-domain reflectometry fiber optic sensor system, the phase information of the signal can be obtained through the inverse tangent operation, and the specific situation of the external disturbance can be judged based on it. However, the phase value obtained by the inverse tangent algorithm will be limited to In between, these are The phases between them are actually winding phases, which differ from the actual phase values , is an integer, so it is necessary to unwrap these wrapped phases to obtain the real phase value. Phase wrapping exists in both the time domain and the space domain of the phase demodulation curve, so it is necessary to perform two phase unwrapping operations to eliminate the phase wrapping phenomenon, which leads to low system operation efficiency and poor system real-time performance. Summary of the invention

[0004] The purpose of the present invention is to provide a phase unwrapping method, computer equipment and storage medium for a beat frequency signal, so as to reduce the system operation burden, improve the system operation efficiency, and effectively solve the problem of poor system real-time performance caused by large signal data volume and large system operation volume.

[0005] In order to solve the above technical problems, the present invention provides a phase unwrapping method of a beat frequency signal, wherein the beat frequency signal is generated by the convergence of a backward Rayleigh scattered light signal generated by a sensing optical fiber and a local oscillator light signal and coherent interference, and the phase unwrapping method comprises: S1, obtaining a photocurrent signal from a beat frequency signal; S2, multiplying the photocurrent signal by a sine signal and a cosine signal whose frequencies are equal to the frequency shift frequency, and then filtering out the double frequency part through a low-pass filter to obtain two orthogonal signals; S3, performing arc tangent on the two orthogonal signals to obtain the winding phase; S4, generating a two-dimensional matrix according to the winding phase; S5. Use a two-dimensional unwrapping algorithm to perform an unwrapping operation on the two-dimensional matrix to obtain a true unwrapping phase. According to the above scheme, the beat frequency signal is expressed as:

[0006] In the formula, is the real-time strength of the beat frequency signal; is the real-time intensity of the local oscillator light; is the amplitude of the local oscillation light; is the initial phase of the local oscillator light; is the real-time intensity of scattered light; is the amplitude of the scattered light; is the light field frequency; The optical frequency shift introduced for the acousto-optic modulator; is the initial phase of the scattered light; For time; is the phase of the external disturbance.

[0007] According to the above scheme, the photocurrent signal is expressed as:

[0008] In the formula, is the real-time intensity of the photocurrent signal in the beat frequency signal.

[0009] According to the above scheme, the results of multiplying the photocurrent signal by the sine signal and the cosine signal are respectively expressed as:

[0010]

[0011] In the formula, is the beat frequency signal multiplied by the eigensignal The real-time intensity of the photocurrent signal is obtained. is the beat frequency signal multiplied by the eigensignal The real-time intensity of the photocurrent signal obtained; The two orthogonal signals are expressed as:

[0012]

[0013] In the formula, The real-time intensity of one of the photocurrent signals obtained after filtering out the double frequency part. It is the real-time intensity of the other photocurrent signal obtained after filtering out the double frequency part.

[0014] According to the above scheme, the winding phase is expressed as: .

[0015] According to the above scheme, step S5 includes: S501, obtaining a two-dimensional phase map from a two-dimensional matrix, searching for residual points in the two-dimensional phase map, and obtaining q values ​​of the residual points; using the first residual point searched as the first reference residual point; (the residual point is a discontinuous breakpoint of the phase derivative in the interference phase map); S502, continue to detect whether other points are residual points in a window of a set size centered on the reference residual point; When another residual point is found in the window, the point is connected with the reference residual point to form a branch tangent; if the search of all points in the window is completed, and the sum of the q values ​​of all points in the window range is not 0, the window size is expanded to continue the search connection process until the sum of the q values ​​of all points in the window is 0 or the window reaches the image edge of the two-dimensional phase image; when the window reaches the edge of the image, the reference residual point is connected with the edge point to form a branch tangent; the search connection is a process of searching for residual points other than the reference residual point in the window, and connecting the searched residual point with the reference residual point to form a branch tangent; the edge point is the intersection of the window and the image edge; each branch tangent formed according to a certain reference residual point constitutes a branch of the reference residual point; S503, after adding the newly connected residual point, determine whether the sum of the q values ​​of all residual points on the branch is 0: if it is 0, jump to step S501 to start a new branch establishment; if not, take the newly connected residual point as a new reference residual point, jump to step S502 to start a new branch establishment; S504, repeat the above steps until the branch tangent connection of all residual points in the two-dimensional phase diagram is completed, and the sum of the q values ​​of all residual points on each branch is made 0; S506. On the premise of bypassing the connected branch tangent, perform phase gradient integration in the azimuth and distance directions to obtain an unwrapping phase.

[0016] According to the above scheme, step S501 includes: forming a minimum closed loop with a certain point and its three adjacent points, and respectively calculating the phase difference between the adjacent points in the four points in a clockwise or counterclockwise direction, and then calculating the q value of the point according to each phase difference; if q>0, the point is a positive residual point, recorded as +1; if q<0, it is a negative residual point, recorded as -1, and subsequent steps are executed after finding a residual point.

[0017] According to the above plan, the scale is set to 3*3.

[0018] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for phase unwrapping of beat frequency signals when executing the computer program.

[0019] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the phase unwrapping method of the beat frequency signal described above are implemented.

[0020] Beneficial Effects The present invention converts the wrapped phase into a two-dimensional matrix in the spatial domain and the time domain, and uses a two-dimensional unwrapping algorithm to perform a two-dimensional unwrapping operation on the wrapped phase to restore the real phase information. Compared with the traditional two-dimensional unwrapping, the global phase information in the entire space and time domain can be quickly obtained, which improves the system operation efficiency, reduces the system operation burden, and can effectively solve the problem of poor system real-time performance caused by large signal data volume and large system operation volume.

[0021] Furthermore, the present invention improves the efficiency of residual point search and further optimizes the system operation efficiency by setting an initial window of a certain size to perform residual point search and gradually expanding the window according to the search results. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the algorithm flow of the phase unwrapping method of the beat frequency signal according to the first embodiment of the present invention Figure 2 It is a structural schematic diagram of a signal phase digital demodulation system of a phase-sensitive optical time-domain reflectometry optical fiber sensing system according to a second embodiment of the present invention; In the figure: 1- narrow linewidth laser, 2- first fiber coupler, 3- acousto-optic modulator, 4- fiber amplifier, 5- bandpass filter, 6- three-port circulator, 7- sensing fiber, 8- second fiber coupler, 9- double-balanced photodetector, 10- data acquisition device, 11- digital demodulation unit. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0024] See also Figure 1 This embodiment discloses a phase unwrapping method for a beat frequency signal, wherein the beat frequency signal is generated by the convergence of a backward Rayleigh scattered light signal generated by a sensing optical fiber and a local oscillator light signal and coherent interference, and the phase unwrapping method includes: S1, obtaining a photocurrent signal from a beat frequency signal; S2, multiplying the photocurrent signal by a sine signal and a cosine signal whose frequencies are equal to the frequency shift frequency, and then filtering out the double frequency part through a low-pass filter to obtain two orthogonal signals; S3, performing arc tangent on the two orthogonal signals to obtain the winding phase; S4, generating a two-dimensional matrix according to the winding phase; in this embodiment, the two-dimensional matrix is ​​represented by RMN, the number of rows M is the number of sampling groups of the data acquisition card, and the number of columns N is the number of phases obtained by sampling once by the data acquisition card; S5. Use a two-dimensional unwrapping algorithm to perform an unwrapping operation on the two-dimensional matrix to obtain a true unwrapping phase. Further, the beat frequency signal is expressed as:

[0025] In the formula, is the real-time strength of the beat frequency signal; is the real-time intensity of the local oscillator light; is the amplitude of the local oscillation light; is the initial phase of the local oscillator light; is the real-time intensity of scattered light; is the amplitude of the scattered light; is the light field frequency; The optical frequency shift introduced for the acousto-optic modulator; is the initial phase of the scattered light; For time; is the phase of the external disturbance.

[0026] Further, the photocurrent signal is expressed as:

[0027] In the formula, is the real-time intensity of the photocurrent signal in the beat frequency signal.

[0028] Furthermore, the results of multiplying the photocurrent signal by the sine signal and the cosine signal are respectively expressed as:

[0029]

[0030] In the formula, is the beat frequency signal multiplied by the eigensignal The real-time intensity of the photocurrent signal is obtained. is the beat frequency signal multiplied by the eigensignal The real-time intensity of the photocurrent signal obtained; The two orthogonal signals are expressed as:

[0031]

[0032] In the formula, The real-time intensity of one of the photocurrent signals obtained after filtering out the double frequency part. It is the real-time intensity of the other photocurrent signal obtained after filtering out the double frequency part.

[0033] Furthermore, the winding phase is expressed as: .

[0034] Further, step S5 includes: S501, obtaining a two-dimensional phase map from a two-dimensional matrix, searching for residual points in the two-dimensional phase map, and obtaining q values ​​of the residual points; using the first residual point searched as the first reference residual point; (the residual point is a discontinuous breakpoint of the phase derivative in the interference phase map); S502, continue to detect whether other points are residual points in a window of a set size (in this embodiment, the set initial size is 3*3) centered on the reference residual point; When another residual point is found in the window, the point is connected with the reference residual point to form a branch tangent; if the search of all points in the window is completed, and the sum of the q values ​​of all points in the window range is not 0, the window size is expanded to continue the search connection process until the sum of the q values ​​of all points in the window is 0 or the window reaches the image edge of the two-dimensional phase image; when the window reaches the edge of the image, the reference residual point is connected with the edge point to form a branch tangent; the search connection is a process of searching for residual points other than the reference residual point in the window, and connecting the searched residual point with the reference residual point to form a branch tangent; the edge point is the intersection of the window and the image edge; each branch tangent formed according to a certain reference residual point constitutes a branch of the reference residual point; S503, after adding the newly connected residual point, determine whether the sum of the q values ​​of all residual points on the branch is 0: if it is 0, jump to step S501 to start a new branch establishment; if not, take the newly connected residual point as a new reference residual point, jump to step S502 to start a new branch establishment; S504, repeat the above steps until the branch tangent connection of all residual points in the two-dimensional phase diagram is completed, and the sum of the q values ​​of all residual points on each branch is made 0; S506. On the premise of bypassing the connected branch tangent, perform phase gradient integration in the azimuth and distance directions to obtain an unwrapped phase. In this embodiment, the unwrapped phase is expressed as:

[0035] In the formula, To unwrap the phase, is the phase gradient operator, is the starting point of calculation, is the end point of the calculation, L is the connection and Any path between two points.

[0036] Further, step S501 includes: forming a minimum closed loop with a certain point and its three adjacent points, and respectively calculating the phase difference between the adjacent points in the four points in a clockwise or counterclockwise direction, and then calculating the q value of the point according to each phase difference; if q>0, the point is a positive residual point, recorded as +1; if q<0, it is a negative residual point, recorded as -1, and after finding a residual point, executing the subsequent steps; In step S501 of this embodiment, the phase differences between the four points are respectively expressed as:

[0037] In the formula, For different phase differences, is the element value at the horizontal coordinate i and the vertical coordinate j in the two-dimensional matrix RMN; q is represented by:

[0038] In the above formula, N is lie in An integer.

[0039] Embodiment 2: See also Figure 2The present embodiment provides a phase-sensitive optical time-domain reflectometry fiber-optic sensing system signal phase digital demodulation system, comprising a narrow linewidth laser 1, a first fiber coupler 2, an acousto-optic modulator 3, a fiber amplifier 4, a bandpass filter 5, a three-port circulator 6, a sensing fiber 7, a second fiber coupler 8, a double-balanced photodetector 9, a data acquisition device 10, and a digital demodulation unit group 11. The connection mode of the system is as follows: the output end of the narrow line width laser 1 is connected to the first input end of the first coupler 2, the first output end of the first coupler 2 is connected to the input end of the acousto-optic modulator 3, the output end of the acousto-optic modulator 3 is connected to the input end of the optical fiber amplifier 4, the output end of the optical fiber amplifier 4 is connected to the input end of the band pass filter 5, the output end of the band pass filter 5 is connected to the input end of the three-port circulator 6, the reflection end of the three-port circulator 6 is connected to the sensing optical fiber 7, the output end of the three-port circulator 6 is connected to the first input end of the second coupler 8, the second output end of the second coupler 8 is connected to the second input end of the first coupler 2, the two output ends of the second coupler 8 are connected to the two input ends of the double balanced photodetector 9, the output end of the double balanced photodetector 9 is connected to the data acquisition device 10, and the data acquisition device 10 is connected to the digital demodulation unit 11. The digital demodulation unit 11 includes the following processing and analysis of the coherent difference frequency signal: Hilbert transform, time translation transform, trigonometric function cross product, addition and subtraction transform, inverse tangent transform, and phase extraction.

[0040] The working principle of the system of the present invention is as follows: a light source with a working wavelength of 1550nm is emitted by a narrow linewidth laser 1, and enters a 90:10 first coupler 2 to be divided into two paths. The path with high power is used as signal light, and passes through an acousto-optic modulator 3 to generate a 200M frequency shift and modulate the optical signal into a pulse light. The modulated pulse light passes through an optical fiber amplifier 4 to amplify the pulse light energy. Since the optical fiber amplifier 4 generates ASE noise, a bandpass filter 5 with a working wavelength of 1550nm and a bandwidth of 1nm is used to filter out the ASE noise generated by the fiber-doped amplifier 4. The signal light after the noise is filtered out by the bandpass filter passes through a three-port circulator 6. The three ports of the three-port circulator 6 are respectively connected to the signal light passing through the bandpass filter 5, the sensing optical fiber 7, and the backward Rayleigh scattered signal containing vibration information transmitted back through the sensing optical fiber 7. The transmitted signal light and another local oscillator light of the first coupler 2 enter the second coupler 8. At the second coupler 8, the local oscillator light and the backward scattered signal undergo coherent interference, and the coherent signal enters the double-balanced photodetector 9. The double-balanced photodetector 9 converts the optical signal into an electrical signal. After transmitting the electrical signal to the data acquisition device 10, it enters the digital demodulation unit 11. The digital demodulation unit 11 executes the steps of the phase unwrapping method of the beat frequency signal described in Example 1.

[0041] Furthermore, the optical fiber amplifier 4 may be an erbium-doped optical fiber amplifier.

[0042] Embodiment three: This embodiment provides a computer device, such as a smart phone, tablet computer, laptop computer, desktop computer, rack server, blade server, tower server or cabinet server (including an independent server or a server cluster composed of multiple servers) that can execute programs. The computer device of this embodiment includes at least but is not limited to: a memory and a processor that can communicate with each other through a system bus.

[0043] In this embodiment, the memory (i.e., readable storage medium) includes flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory, etc.), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM). The memory may also be an external storage device of a computer device, such as a plug-in hard disk equipped on the computer device, a smart memory card (SmartMedia Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. Of course, the memory may also include both the internal storage unit of the computer device and its external storage device. In this embodiment, the memory is generally used to store the operating system and various application software installed on the computer device, such as the program code of the phase unwrapping method of the beat frequency signal described in the first embodiment. In addition, the memory may also be used to temporarily store various data that have been output or are to be output.

[0044] In some embodiments, the processor may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chips. The processor is generally used to control the overall operation of a computer device. In this embodiment, the processor is used to run the program code stored in the memory or process data to implement the phase unwrapping method of the beat frequency signal described in the first embodiment.

[0045] Embodiment 4: The present application also provides a computer-readable storage medium, such as a flash memory, a hard disk, a multimedia card, a card-type memory (for example, an SD or DX memory, etc.), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a disk, an optical disk, a server, an App application store, etc., on which a computer program is stored, and the program realizes corresponding functions when executed by a processor. The computer-readable storage medium of this embodiment is used to store the program code of the phase unwrapping method of the beat frequency signal, and when executed by the processor, the phase unwrapping method of the beat frequency signal described in Example 1 is realized.

[0046] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, and two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0047] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A phase unwrapping method for a beat frequency signal, wherein the beat frequency signal is generated by the convergence of a backward Rayleigh scattered light signal generated by a sensing optical fiber and a local oscillator light signal and coherent interference, characterized in that: Phase unwrapping methods include: S1, obtaining a photocurrent signal from a beat frequency signal; S2, multiplying the photocurrent signal by a sine signal and a cosine signal whose frequencies are equal to the frequency shift frequency, and then filtering out the double frequency part through a low-pass filter to obtain two orthogonal signals; S3, performing arc tangent on the two orthogonal signals to obtain the winding phase; S4, generating a two-dimensional matrix according to the winding phase; S5. Use a two-dimensional unwrapping algorithm to perform an unwrapping operation on the two-dimensional matrix to obtain a true unwrapping phase.

2. The phase unwrapping method of the beat frequency signal according to claim 1, characterized in that: The beat frequency signal is expressed as: Where I(t) is the real-time intensity of the beat signal; E L (t) is the real-time intensity of the local oscillator light; E L is the amplitude of the local oscillation light; is the initial phase of the local oscillator light; E S (t) is the real-time intensity of scattered light; E S is the amplitude of the scattered light; ν0 is the frequency of the light field; ν1 is the optical frequency shift introduced by the AOM; is the initial phase of the scattered light; t is the time; is the phase of the external disturbance.

3. The phase unwrapping method of the beat frequency signal according to claim 2, characterized in that: The photocurrent signal is expressed as: In the formula, I L (t) is the real-time intensity of the photocurrent signal in the beat frequency signal.

4. The phase unwrapping method of the beat frequency signal according to claim 3, characterized in that: The results of multiplying the photocurrent signal by the sine signal and the cosine signal are respectively expressed as: Where, I1(t) is the real-time intensity of the photocurrent signal obtained by multiplying the beat frequency signal by the intrinsic signal sin(2πν1t), and Q1(t) is the real-time intensity of the photocurrent signal obtained by multiplying the beat frequency signal by the intrinsic signal cos(2πν1t); The two orthogonal signals are expressed as: Wherein, I2(t) is the real-time intensity of one of the photocurrent signals obtained after filtering out the double frequency part, and Q2(t) is the real-time intensity of the other photocurrent signal obtained after filtering out the double frequency part.

5. The phase unwrapping method of the beat frequency signal according to claim 4, characterized in that: The winding phase is expressed as:

6. The phase unwrapping method of the beat frequency signal according to claim 5, characterized in that: Step S5 includes: S501, obtaining a two-dimensional phase diagram from a two-dimensional matrix, searching for residual points in the two-dimensional phase diagram, and obtaining q values ​​of the residual points; using the first residual point searched as the first reference residual point; (the residual point is a discontinuous breakpoint of the phase derivative in the interference phase diagram); S502, continue to detect whether other points are residual points in a window of a set size centered on the reference residual point; When another residual point is found in the window, the point is connected with the reference residual point to form a branch tangent; if the search of all points in the window is completed, and the sum of the q values ​​of all points in the window range is not 0, the window size is expanded to continue the search connection process until the sum of the q values ​​of all points in the window is 0 or the window reaches the image edge of the two-dimensional phase image; when the window reaches the edge of the image, the reference residual point is connected with the edge point to form a branch tangent; the search connection is a process of searching for residual points other than the reference residual point in the window, and connecting the searched residual point with the reference residual point to form a branch tangent; the edge point is the intersection of the window and the image edge; each branch tangent formed according to a certain reference residual point constitutes a branch of the reference residual point; S503, after adding the newly connected residual point, determine whether the sum of the q values ​​of all residual points on the branch is 0: if it is 0, jump to step S501 to start a new branch establishment; if not, take the newly connected residual point as a new reference residual point, jump to step S502 to start a new branch establishment; S504, repeat the above steps until the branch tangent connection of all residual points in the two-dimensional phase diagram is completed, and the sum of the q values ​​of all residual points on each branch is made 0; S506. On the premise of bypassing the connected branch tangent, perform phase gradient integration in the azimuth and distance directions to obtain an unwrapping phase.

7. The phase unwrapping method of the beat frequency signal according to claim 6, characterized in that: Step S501 includes: forming a minimum closed loop with a certain point and its three adjacent points, and respectively calculating the phase difference between the adjacent points in the four points in a clockwise or counterclockwise direction, and then calculating the q value of the point according to each phase difference; if q>0, the point is a positive residual point, recorded as +1; if q<0, it is a negative residual point, recorded as -1, and subsequent steps are executed after finding a residual point.

8. The phase unwrapping method of the beat frequency signal according to claim 6, characterized in that: Set the scale to 3*3.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the phase unwrapping method of the beat frequency signal according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the phase unwrapping method of the beat frequency signal according to any one of claims 1 to 8 are implemented.

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