A wind erosion monitoring system and method based on distributed optical fiber

Abstract

This invention provides a wind erosion monitoring system and method based on distributed optical fiber, belonging to the field of optical-based wind and sand monitoring technology. It includes: constructing a wind erosion monitoring system comprising a linearly tunable laser, an optical isolator, a first coupler, an upper branch, a lower branch, a sand particle capture sensor, a photoelectric detection and acquisition module, and a host computer; utilizing the Rayleigh scattering signal of the linearly swept laser in the sensing optical fiber and the interference with a reference light, the vibration information distributed along the optical fiber is obtained by demodulating the beat frequency signal; combining the constructed sand particle impact and optical fiber coupling model, the dynamic strain generated by sand particle impact is converted into phase changes, realizing the acquisition of sand particle impact location, sand particle size, and sand particle quantity. This invention enables continuous distributed monitoring of wind and sand flows with high spatial resolution, and has advantages such as resistance to electromagnetic interference, strong environmental adaptability, and multi-parameter sensing, and can operate stably for a long time in harsh desert environments.

Description

Technical Field

[0001] This invention relates to the field of optical-based wind and sand monitoring technology, and in particular to a wind erosion monitoring system and method based on distributed optical fibers. Background Technology

[0002] Wind erosion and its resulting sand movement are key surface processes in arid and semi-arid regions. Under wind influence, sand particles move through suspension, displacement, and creep, with displacement being the primary mode of sand transport. Wind erosion not only leads to topsoil loss, decreased land productivity, and ecosystem degradation, but also impacts regional and even global climate and air quality through dust release, severely restricting regional ecological security and sustainable development.

[0003] Obtaining information on wind erosion intensity and sand particle size is fundamental to understanding wind and sand transport mechanisms, assessing soil erosion levels, and optimizing windbreak and sand-fixing measures. Therefore, there is an urgent need to develop monitoring technologies with high precision, high spatiotemporal resolution, and the ability to simultaneously acquire multiple parameters.

[0004] Traditional wind erosion and sandstorm monitoring technologies mainly include sand collection weighing, capacitive wind erosion sensors, laser particle counters, and remote sensing inversion. Sand collection weighing, which physically collects and weighs displaced sand particles and then uses sieving to obtain particle size distribution, is one of the most classic methods. However, it has low temporal resolution (typically greater than or equal to 1 minute), sparse spatial sampling points, and is easily affected by sand particle size, impacting sampling efficiency. Capacitive wind erosion sensors identify wind erosion events by detecting capacitance changes caused by sand particle impacts, but they struggle to provide spatial location information for sand particles. Laser particle counters are used for sand particle number measurement and particle size spectrum analysis, offering millisecond to second-level temporal resolution. However, they are susceptible to interference from harsh outdoor environments (such as high concentrations of dust and strong light) and cannot provide spatial location information for sand particle impacts, thus relying on point-based monitoring. Remote sensing inversion technology offers advantages such as wide coverage and large-scale monitoring capabilities, but its spatial resolution is limited, making it difficult to achieve detailed observation of near-surface displacement processes. Furthermore, its inversion accuracy is significantly affected by atmospheric and surface conditions.

[0005] In summary, existing technologies generally suffer from the following limitations: First, they rely on single monitoring parameters, making it impossible to simultaneously and in-situ acquire multi-dimensional information such as sand particle size, quantity, and spatial location. Second, they struggle to balance spatiotemporal resolution and monitoring accuracy, resulting in either sparse sampling or susceptibility to environmental interference. Third, they lack the ability to perform refined analysis of the vertical structure of windblown sand flows, making it difficult to reveal the microscopic mechanisms of near-surface wind-blown sand exchange. These limitations constrain the deepening of basic research on windblown sand movement and the demand for high-precision engineering assessments. Summary of the Invention

[0006] In view of this, the present invention provides a wind erosion monitoring system and method based on distributed optical fiber, which is used for synchronous and continuous distributed monitoring of sand particle size, quantity and impact position during wind and sand transition, to clarify the specific transition height distribution of sand particles with destructive particle size, and to accurately assess the degree of erosion threat of wind and sand flow to different windward surfaces of crops, surface crusts or engineering facilities, and is suitable for complex and harsh desert environments.

[0007] The technical solution adopted by the embodiments of the present invention to solve its technical problem is as follows:

[0008] The first aspect of the present invention provides a wind erosion monitoring system based on distributed optical fiber, comprising: a linearly tunable laser (1), an optical isolator (2), a first coupler (3), an upper branch, a lower branch, a sand grain capture sensor (16), a photodetector, a data acquisition module (14), and a host computer (15); the upper branch is provided with a second coupler (4), a variable attenuator (6), a polarization controller (7), and a third coupler (8) in sequence along the optical path; the lower branch is provided with a fourth coupler (9), a delay fiber (10), and a fifth coupler (11) in sequence along the optical path;

[0009] The laser output from the linearly tunable laser (1) enters the first coupler (3) through the optical isolator (2), and is proportionally divided into upper branch light and lower branch light, which enter the upper branch and lower branch respectively.

[0010] In the lower branch, the lower branch light passes through an unbalanced Mach-Zehnder interference structure containing a delay fiber, generating an auxiliary interference signal that is received by the first balanced photodetector (12).

[0011] In the upper branch, the second coupler (4) divides the upper branch light into a reference light signal and a measurement light signal; the reference light signal passes through a variable attenuator (6) and a polarization controller (7) in sequence to form a reference arm light signal that is input to the third coupler (8); the measurement light signal enters the sensing fiber in the sand grain capture sensing device (16) through a circulator (5), and the generated backscattered Rayleigh signal returns and is input to the third coupler (8) through the circulator (5), where it is coupled with the reference arm light signal at the third coupler (8); the third coupler (8) outputs an interference beat frequency signal that enters the second balanced photodetector (13);

[0012] The sand capture sensor (16) includes a sand capture device fixing rod (20), a height adjustment slider (19), and a sand capture plate (18); the sand capture plate (18) is fixed on the vertically set fixing rod (20) by the height adjustment slider (19), and the height adjustment slider (19) adjusts the height of the sand capture plate (18) in the vertical direction; the sensing optical fiber is fixed on the surface of the sand capture plate (18) and arranged in a regular manner to form a high-density sensing array;

[0013] The acquisition module (14) is used to receive the auxiliary interference signal and extract periodic feature points with corresponding equal optical frequency variation intervals as external clock trigger sources; under the triggering action of the external clock trigger source, the acquisition module (14) performs synchronous sampling of the interference beat frequency signal with equal optical frequency intervals;

[0014] The host computer analyzes the two photoelectric signals to obtain wind erosion monitoring data:

[0015] Demodulate the interference beat frequency signal, obtain the dynamic response main frequency and main frequency amplitude when a single sand grain impact event occurs on the sand grain capture plate (18), and calculate the equivalent diameter of the sand grain corresponding to the impact point;

[0016] Based on the laying pattern of the sensing fiber on the sand capture plate (18), the layout height of the sand capture plate (18), and the sensing distance of the backscattered Rayleigh signal in the sensing fiber, the two-dimensional coordinates of the impact point on the sand capture plate (18) and its absolute spatial height in actual space are determined.

[0017] By adjusting the height adjustment slider (19), data is collected at different levels of height. The impact time, absolute spatial height, and equivalent diameter of sand grains corresponding to each impact point are used as data features to form a multi-dimensional feature joint database.

[0018] Based on a multidimensional feature database, joint statistics of spatial distribution features are performed to obtain the height-particle size distribution matrix and feature parameter profile curves, thereby analyzing the degree of wind erosion threat.

[0019] Preferably, the linearly tunable laser (1) outputs a narrow-linewidth laser with a center wavelength located in the optical fiber communication band, which is split into two paths at a ratio of 99:1 by the first coupler (3).

[0020] Preferably, the sensing fiber is fixed to the surface of the sand trapping plate (18) by a special adhesive or embedded microgroove; the sand trapping plate (18) is set perpendicular to the ground and the sensing fiber is located on the surface of the windward side.

[0021] Preferably, the sensing optical fibers are laid out in a serpentine, close-packed pattern, and the spacing D of the sensing optical fibers on the surface of the capture plate is related to the spatial resolution of the system. Satisfying Relationships ,in, It is a positive integer. , The speed of light in a vacuum. The effective refractive index of the sensing fiber. This represents the sweep bandwidth of the tunable laser.

[0022] Preferably, the host computer calculates the equivalent diameter of the sand grains based on the interferometric beat frequency signal, specifically by defining a grain size calculation model, which includes:

[0023] When the sensing optical fiber is struck by sand grains, generating a vibration signal, the expression for the change in fiber strain is:

[0024] ;

[0025] In the formula, The frequency of the sinusoidal vibration that occurs in the sensing optical fiber. Amplitude;

[0026] Phase modulation of backscattered Rayleigh light signal caused by fiber vibration The expression is:

[0027] ;

[0028] In the formula, n is the refractive index of the optical fiber. , These are the elastic coefficients in the direction of sand grain impact and the elastic coefficients perpendicular to the direction of sand grain impact, respectively. The incident wavelength, This represents the physical distance that light travels in an optical fiber. A constant less than 1; Indicates the phase modulation amplitude;

[0029] Based on the OFDR sensing principle, the backscattered Rayleigh light signal at impact point i on the sensing fiber... Represented as:

[0030] ;

[0031] In the formula, Let i be the scattering rate at point i. Let be the amplitude of the incident light field. The initial center frequency of the laser is . Let i be the time delay at point i. The frequency modulation speed of the linearly tunable laser (1) is... Let i be the initial random phase at point i;

[0032] The backscattered Rayleigh signal at point i is interfered with the reference arm optical signal by the second balanced photodetector (13) to obtain the interference beat frequency signal at point i. :

[0033] ;

[0034] Will The signal is Fourier transformed to the frequency domain to obtain the spectrum. :

[0035] ;

[0036] ;

[0037] Amplitude spectrum in the neutral frequency range for:

[0038] ;

[0039] In the formula, the main frequency amplitude ;

[0040] Establish a quantitative relationship between sand grain impact and optical fiber vibration response: When a jumping sand grain impacts an optical fiber perpendicularly, part of its kinetic energy is converted into the local vibrational energy of the optical fiber; the instantaneous impact kinetic energy of the sand grain... Represented as:

[0041] ;

[0042] In the formula, d is the equivalent diameter of the sand grain. m is the density of the sand grain, and m is the mass of the sand grain. Here, v is the velocity coefficient, representing wind speed; This represents the elastic modulus of the optical fiber material; The peak vibration strain is obtained by measuring the wind erosion measurement system. , The outer diameter of the optical fiber is the effective length of the fiber that deforms / vibrates when struck by sand. , ;

[0043] The function defining the equivalent diameter d of a sand grain is:

[0044] ;

[0045] In the formula, the main frequency for The maximum value; constant ,constant , It is a proportionality constant;

[0046] By solving the particle size calculation model, the equivalent diameter d of the sand grain at impact point i is obtained.

[0047] Preferably, the host computer determines the three-dimensional coordinates of the impact point by:

[0048] Calculate the transmission distance at impact point i. , ;

[0049] Based on the equal-length round-trip laying method of the sensing fiber, a one-dimensional plane coordinate system for the fiber length and the sand trapping plate (18) is established based on piecewise linear interpolation and inter-row turning logic. The mapping relationship between them will Convert to two-dimensional plane coordinates for:

[0050] ;

[0051] ;

[0052] ;

[0053] ;

[0054] In the formula, Indicates the row number, starting with the row where the transmission fiber originates, and sorted from bottom to top; For offset, it indicates the position at the 1st position. The length of optical fiber already laid within the industry; The length of a single row of sensing optical fiber laid on the sand grain trapping plate;

[0055] Calculate the absolute spatial height corresponding to impact point i. , , The current level height of the sand trapping plate is set on the fixed rod (20) by the height adjustment slider (19).

[0056] Preferably, the host computer establishes a multi-dimensional feature joint database for wind erosion monitoring, including:

[0057] Data can be collected at different height levels by adjusting the height adjustment slider (19);

[0058] Acquire data features of each impact point A multidimensional feature joint database is formed, in which Let i be the impact time corresponding to impact point i;

[0059] Based on a multi-dimensional feature database, joint statistics of spatial distribution features were performed to obtain a height-particle size distribution matrix, feature parameter profile curves, impact hotspot distribution map on the plane of the capture plate, vertical profile curve of sand particle kinetic energy flux as a function of height, and histograms of sand particle size distribution at each height level, thereby analyzing the degree of wind erosion threat.

[0060] The vertical section is arranged according to Divide the height into J height intervals and calculate the height of each interval. The total number of sand impacts within time T. ; Calculate the kinetic energy flux in height interval j and the total kinetic energy flux of the J height ranges :

[0061] ;

[0062] ;

[0063] In the formula, For the kinetic energy of the sand grains, Let j be the wind speed corresponding to the altitude range. This represents the effective acquisition area of ​​the sensing fiber on the sand grain capture plate. For monitoring duration; j∈[1,J];

[0064] Calculate the mass flux in height interval j and the total mass flux of J height intervals :

[0065] ; ;

[0066] ;

[0067] In the formula, The kinetic energy of the sand grains;

[0068] Will Convert to the current wind erosion modulus, and query the corresponding wind erosion intensity level and total kinetic energy flux for the current wind erosion modulus. Check if the corresponding wind erosion intensity levels are consistent, and output the wind erosion intensity level if the levels are the same.

[0069] A second aspect of this invention provides a wind erosion monitoring method based on distributed optical fibers, comprising the following steps:

[0070] Step S1: The acquisition module receives the auxiliary interference signal output by the first balanced photodetector and extracts the periodic feature points with corresponding equal optical frequency variation intervals as external clock trigger sources. Under the triggering action of the external clock trigger source, the acquisition module performs synchronous sampling of the interference beat frequency signal output by the second balanced photodetector with equal optical frequency intervals.

[0071] Step S2: The host computer analyzes the two photoelectric signals to obtain wind erosion monitoring data.

[0072] Demodulate the interferometric beat frequency signal to obtain the dynamic response main frequency and main frequency amplitude when a single sand grain impact event occurs on the sand grain capture plate, and calculate the equivalent diameter of the sand grain corresponding to the impact point.

[0073] Based on the laying pattern of the sensing fiber of the sand grain capture plate, the deployment height of the sand grain capture plate, and the sensing distance of the backscattered Rayleigh signal in the sensing fiber, the two-dimensional coordinates of the impact point on the sand grain capture plate and its absolute spatial height in actual space are determined.

[0074] By adjusting the height adjustment slider, data is collected at different levels of height. The impact time, absolute spatial height, and equivalent diameter of sand grains corresponding to each impact point are used as data features to form a multi-dimensional feature joint database.

[0075] Based on a multidimensional feature database, joint statistics of spatial distribution features are performed to obtain the height-particle size distribution matrix and feature parameter profile curves, thereby analyzing the degree of wind erosion threat.

[0076] Preferably, based on a multi-dimensional feature joint database, joint statistics of spatial distribution features are performed to obtain a height-grain size distribution matrix and feature parameter profile curves, and the degree of wind erosion threat is analyzed, including:

[0077] Data can be collected at different height levels by adjusting the height adjustment slider.

[0078] Acquire data features of each impact point A multidimensional feature joint database is formed, in which Let i be the impact time corresponding to impact point i;

[0079] Based on a multi-dimensional feature database, joint statistics of spatial distribution features were performed to obtain a height-particle size distribution matrix, feature parameter profile curves, impact hotspot distribution map on the plane of the capture plate, vertical profile curve of sand particle kinetic energy flux as a function of height, and histograms of sand particle size distribution at each height level, thereby analyzing the degree of wind erosion threat.

[0080] The vertical section is arranged according to Divide the height into J height intervals and calculate the height of each interval. The total number of sand impacts within time T. ; Calculate the kinetic energy flux in height interval j and the total kinetic energy flux of the J height ranges :

[0081] ;

[0082] ;

[0083] In the formula, For the kinetic energy of the sand grains, Let j be the wind speed corresponding to the altitude range. This represents the effective acquisition area of ​​the sensing fiber on the sand grain capture plate. For monitoring duration; j∈[1,J];

[0084] Calculate the mass flux in height interval j and the total mass flux of J height intervals :

[0085] ; ;

[0086] ;

[0087] In the formula, The kinetic energy of the sand grains;

[0088] Will Convert to the current wind erosion modulus, and query the corresponding wind erosion intensity level and total kinetic energy flux for the current wind erosion modulus. Check if the corresponding wind erosion intensity levels are consistent, and output the wind erosion intensity level if the levels are the same.

[0089] As can be seen from the above technical solutions, the wind erosion monitoring system and monitoring method based on distributed optical fiber provided by the embodiments of the present invention. The wind erosion monitoring system consists of a linearly tunable laser, an optical isolator, a first coupler, an upper branch, a lower branch, a sand grain capture sensor (16), a photodetector, a data acquisition module, and a host computer. The laser output from the linearly tunable laser enters the first coupler through the optical isolator and is proportionally distributed into upper branch light and lower branch light, which enter the upper branch and lower branch respectively. In the upper branch, the second coupler distributes the upper branch light into a reference light signal and a measurement light signal. The reference light signal passes through a variable attenuator and a polarization controller in sequence to form a reference arm light signal, which is input to the third coupler. The measurement light signal enters the sensing fiber in the sand grain capture sensor through a circulator. The generated backscattered Rayleigh signal returns and enters the third coupler through the circulator, where it couples with the reference arm light signal. The third coupler outputs an interference beat frequency signal, which enters the second balanced photodetector. In the lower branch, the lower branch light passes through an unbalanced Mach-Zehnder interference structure containing a delay fiber, generating an auxiliary interference signal that is received by the first balanced photodetector. The system receives auxiliary interference signals and extracts periodic feature points with corresponding equal optical frequency variation intervals as external clock trigger sources. Under the triggering action of the external clock trigger source, the interference beat frequency signals are synchronously sampled at equal optical frequency intervals. The host computer analyzes the two photoelectric signals and uses the impact time, absolute spatial height, and equivalent diameter of sand grains corresponding to each impact point as data features to form a multi-dimensional feature joint database. Based on the multi-dimensional feature joint database, joint statistics of spatial distribution features are performed to obtain the height-particle size distribution matrix and feature parameter profile curves, analyzing the degree of wind erosion threat. This can be used for synchronous and continuous distributed monitoring of sand particle size, quantity, and impact position during wind and sand transitions, clarifying the specific transition height distribution of sand particles with destructive particle sizes, and accurately assessing the degree of erosion threat of wind and sand flow to different windward surfaces of crops, surface crusts, or engineering facilities. Utilizing the millimeter-level spatial resolution and millisecond-level response capability of distributed fiber optic sensing technology, synchronous and distributed sensing of sand particle impact position, particle size, and quantity is achieved. This provides a new technical means for the study of the microscopic mechanism of wind and sand movement and the scientific evaluation and optimization of windbreak and sand fixation projects. Attached Figure Description

[0090] Figure 1 This is a block diagram of a wind erosion monitoring system based on distributed optical fiber according to the present invention;

[0091] Figure 2 This is a diagram of the sand particle capture device in the wind erosion monitoring system based on distributed optical fiber of the present invention;

[0092] Figure 3 This is a diagram showing the fiber optic cable laying pattern for the sand grain capture plate of the wind erosion monitoring system based on distributed optical fiber according to the present invention.

[0093] Figure 4 This is a schematic diagram illustrating the sand particle location of the wind erosion monitoring system based on distributed optical fiber according to the present invention.

[0094] Figure 5 This is a schematic diagram of the spectrum of the wind erosion monitoring system based on distributed optical fiber according to the present invention;

[0095] 1. Linear tunable laser; 2. Optical isolator; 3. First coupler; 4. Second coupler; 5. Circulator; 6. Variable attenuator; 7. Polarization controller; 8. Third coupler; 9. Fourth coupler; 10. Delay fiber; 11. Fifth coupler; 12. First balanced photodetector; 13. Second balanced photodetector; 14. Data acquisition card; 15. Host computer; 16. Sand capture device; 17. Slider fixing mechanism; 18. Sand capture plate; 19. Sand capture plate height adjustment slider; 20. Sand capture device fixing rod. Detailed Implementation

[0096] The technical solution and effects of the present invention will be further described in detail below with reference to the accompanying drawings.

[0097] refer to Figure 1 As shown, a wind erosion monitoring system based on distributed optical fiber, such as Figure 1 As shown, the system consists of an optical frequency domain reflection sensing demodulation device combined with a specially designed "serpentine" fiber optic sand-catching device. This method utilizes the Rayleigh scattering signal of a linearly swept laser in the sensing fiber and its interference with a reference light to obtain vibration information distributed along the fiber by demodulating the beat frequency signal. Using a sand impact and fiber coupling model, the vibration signal generated by the sand impact is converted into a phase change, establishing the distribution law of sand impact position and impact energy along the entire sensing fiber. The sensing position of the fiber under test corresponds to the spatial coordinates on the sand-catching plate. The sand impact position is determined using the optical frequency domain reflection principle, and the particle size and quantity are reflected through the amplitude-frequency characteristics of the vibration response.

[0098] The first aspect of the present invention provides a wind erosion monitoring system based on distributed optical fiber, comprising: a linearly tunable laser (1), an optical isolator (2), a first coupler (3), an upper branch, a lower branch, a sand grain capture sensor (16), a photodetector, a data acquisition module (14), and a host computer (15); the upper branch is provided with a second coupler (4), a variable attenuator (6), a polarization controller (7), and a third coupler (8) in sequence along the optical path; the lower branch is provided with a fourth coupler (9), a delay fiber (10), and a fifth coupler (11) in sequence along the optical path;

[0099] The linear tunable laser (1) outputs a narrow linewidth laser with a center wavelength located in the optical fiber communication band (1550nm). After passing through an optical isolator (2) to prevent backlighting, it is split into an upper branch and a lower branch by a first coupler (3) in a ratio (e.g., 99:1) and enters the upper and lower branches respectively.

[0100] The lower branch includes a fourth coupler (9), a delay fiber (10), and a fifth coupler (11). The fourth coupler (9) divides the lower branch light into a first optical signal and a second optical signal; the second optical signal is input to the fifth coupler (11) via the delay fiber (10) and coupled with the first optical signal at the fifth coupler (11); the coupled signal of the fifth coupler (11) enters the first balanced photodetector (12); the lower branch light passes through an unbalanced Mach-Zehnder interference structure containing the delay fiber, generating an auxiliary interference signal that is received by the first balanced photodetector (12); this signal is transmitted to the data acquisition card (14) as an external clock trigger source to eliminate the influence of nonlinear frequency sweep of the light source and achieve equal frequency interval sampling.

[0101] In the upper branch, the second coupler (4) divides the upper branch light into a reference light signal and a measurement light signal; the reference light signal passes through the variable attenuator (6) and the polarization controller (7) in sequence to form a reference arm light signal that is input to the third coupler (8); the measurement light signal enters the sensing fiber in the sand grain capture sensing device (16) through the circulator (5), and the generated backscattered Rayleigh signal returns and is input to the third coupler (8) through the circulator (5), where it is coupled with the reference arm light signal at the third coupler (8); the third coupler (8) outputs an interference beat frequency signal that enters the second balanced photodetector (13);

[0102] The sand-catching sensor device (16) includes a sand-catching device fixing rod (20), a height adjustment slider (19), and a sand-catching plate (18). The sand-catching plate (18) is fixed to the vertically set fixing rod (20) by the height adjustment slider (19), and the height of the sand-catching plate (18) can be freely adjusted vertically by the height adjustment slider (19). The sensing optical fiber is fixed to the surface of the catching plate by a special adhesive or embedded microgrooves, and is arranged regularly to form a high-density sensing array to ensure sensitive response to the impact of small sand particles. The sand-catching plate (18) is set perpendicular to the ground, and the sensing optical fiber is located on the surface on the windward side.

[0103] The acquisition module (14) is used to receive the auxiliary interference signal and extract the periodic feature points (such as zero crossings) with corresponding equal optical frequency change intervals as external clock trigger sources. Under the triggering action of the external clock trigger source, the acquisition module (14) performs synchronous trigger acquisition on the interference beat frequency signal output by the upper branch, so that each data acquisition action occurs on equal optical frequency intervals, thereby transforming the non-uniform sampling in the time domain into equal frequency interval sampling in the optical frequency domain, thereby eliminating the nonlinear influence of the linear tunable laser (1) in the frequency sweeping process.

[0104] Furthermore, such as Figure 2 As shown, the sand grain capture device in the wind erosion measurement optical system based on distributed optical fibers includes multi-level height settings. The vertical profile of the wind-blown sand flow to be measured is divided into N height levels: level-1 (near the ground surface), level-2, ..., level-i, ..., level-N; by adjusting the height of the sand grain capture plate on a vertically fixed sliding rod, the active wind-blown sand transition layer from 0cm to 100cm and above the ground surface is covered, achieving refined analysis of the vertical structure of the wind-blown sand flow.

[0105] The sensing optical fibers are laid out in a serpentine, tightly packed pattern, and the spacing D of the sensing optical fibers on the surface of the capture plate satisfies the following relationship: ,in, It is a positive integer; when the linearly tunable laser performs a linear frequency sweep, the spatial resolution of the system is... Determined by the sweep frequency range: , The speed of light in a vacuum. The effective refractive index of the sensing fiber. This refers to the sweep bandwidth of the tunable laser. By employing this tightly packed, serpentine arrangement, the one-dimensional fiber position is mapped to two-dimensional coordinates on the capture plate, enabling the location of sand grains' landing points (x, y) on the capture plate. By utilizing a high-bandwidth linear sweep frequency light source, the system achieves millimeter-level spatial positioning capabilities, overcoming the limitations of traditional point sensors in spatial resolution.

[0106] The host computer analyzes the two photoelectric signals to obtain wind erosion monitoring data:

[0107] Demodulate the interference beat frequency signal, obtain the dynamic response main frequency and main frequency amplitude when a single sand grain impact event occurs on the sand grain capture plate (18), and calculate the equivalent diameter of the sand grain corresponding to the impact point;

[0108] Based on the laying pattern of the sensing fiber on the sand capture plate (18), the layout height of the sand capture plate (18), and the sensing distance of the backscattered Rayleigh signal in the sensing fiber, the two-dimensional coordinates of the impact point on the sand capture plate (18) and its absolute spatial height in actual space are determined.

[0109] By adjusting the height adjustment slider (19), data is collected at different levels of height. The impact time, absolute spatial height, and equivalent diameter of sand grains corresponding to each impact point are used as data features to form a multi-dimensional feature joint database.

[0110] Based on a multidimensional feature database, joint statistics of spatial distribution features are performed to obtain the height-particle size distribution matrix and feature parameter profile curves, thereby analyzing the degree of wind erosion threat.

[0111] Preferably, the host computer calculates the equivalent diameter of the sand grains based on the interferometric beat frequency signal, specifically by defining a grain size calculation model, which includes:

[0112] When the sensing optical fiber is struck by sand particles, generating a vibration signal, the fiber vibration is actually a dynamically changing strain applied to the fiber. When a sinusoidal vibration exists, the expression for the resulting fiber strain change is:

[0113] (1)

[0114] In the formula, The frequency of the sinusoidal vibration that occurs in the sensing optical fiber. The maximum strain of the optical fiber under vibration represents the magnitude of the vibration amplitude.

[0115] When an optical fiber is subjected to a vibration load, the resulting phase modulation is determined by the amplitude, frequency, and length of the fiber subjected to the vibration. The phase modulation of the backscattered Rayleigh light signal caused by the fiber vibration is... The expression is:

[0116] (2)

[0117] In the formula, n is the refractive index of the optical fiber. , These are the elastic coefficients in the direction of sand grain impact and the elastic coefficients perpendicular to the direction of sand grain impact, respectively. The incident wavelength, This represents the physical distance that light travels in an optical fiber. A constant less than 1 ; Indicates the phase modulation amplitude;

[0118] As shown in equation (2), when an optical fiber is subjected to a vibration load, the resulting phase modulation is determined by the amplitude, the vibration frequency, and the length of the optical fiber subjected to the vibration. The above equation can be simplified to:

[0119] (3)

[0120] In the formula, This indicates the phase modulation amplitude.

[0121] Based on the OFDR sensing principle, assuming the fiber under test... The aforementioned vibration exists at a point i, and the backscattered Rayleigh light signal at impact point i on the sensing fiber... Represented as:

[0122] (4)

[0123] In the formula, Let i be the scattering rate at point i. Let be the amplitude of the incident light field. The initial center frequency of the laser is . Let i be the time delay at point i. The frequency modulation speed of the linearly tunable laser (1) is... Let i be the initial random phase at point i;

[0124] The backscattered Rayleigh signal at point i is interfered with the reference arm optical signal by the second balanced photodetector (13) to obtain the interference beat frequency signal at point i. :

[0125] (5)

[0126] In the formula, Includes beat frequency terms that vary linearly with time. ; The phase is constant;

[0127] Will The signal is Fourier transformed to the frequency domain to obtain the spectrum. :

[0128] (6)

[0129] (7)

[0130] Amplitude spectrum in the neutral frequency range for:

[0131] (8)

[0132] In the formula, the main frequency amplitude ;like Figure 5 As shown, the particle size of the corresponding impacting sand grains can then be obtained.

[0133] Next, a quantitative relationship between sand grain impact and optical fiber vibration response was established: when a jumping sand grain impacts an optical fiber perpendicularly, part of its kinetic energy is converted into local vibrational energy of the fiber, causing micro-bending and phase changes in the fiber. Based on classical collision theory, the instantaneous impact kinetic energy of the sand grain... Represented as:

[0134] (9)

[0135] In the formula, d is the equivalent diameter of the sand grain. m is the density of the sand grain, and m is the mass of the sand grain. Let v be the velocity coefficient (between 0.3 and 0.5), and v represent the wind speed; assume that the kinetic energy is considered to be generated in a very short contact time. Vibrational energy internally converted into optical fiber:

[0136] (10)

[0137] This represents the elastic modulus of the optical fiber material, approximately 7.0 × 10¹. 0 N / m²; The peak vibration strain is obtained by measuring the wind erosion measurement system. , The outer diameter of the optical fiber. The effective length of the optical fiber that deforms / vibrates when struck by sand grains is . , ;

[0138] The function defining the equivalent diameter d of a sand grain is:

[0139] (11)

[0140] In the formula, the main frequency for The maximum value; constant ,constant , This is a proportionality constant related to the optical fiber and its collision mechanical properties;

[0141] By solving the particle size calculation model, the equivalent diameter d of the sand grain at impact point i is obtained.

[0142] Furthermore, the system uses preset "serpentine" laying parameters (board length) , laying spacing A one-dimensional fiber length was established. coordinates of the two-dimensional capture plate plane The mapping relationship between them is implemented based on piecewise linear interpolation and inter-row steering logic, ensuring that each fiber position uniquely corresponds to a coordinate point on the board, thereby achieving planar positioning of the sand particle impact position.

[0143] line number This indicates how many complete "round trips" of fiber optic cable have been laid, with each round trip being [length missing]. (outbound journey) Add spacing ).

[0144] Offset : Indicates the length of optical fiber already laid in the current row.

[0145] Coordinate determination: If This indicates that the current line is still being laid in the forward direction. Coordinates Increase, The coordinates remain unchanged; if This indicates that the laying has been reversed. Coordinates from maximum value Decreasing.

[0146] The host computer determines the three-dimensional coordinates of the impact point, including:

[0147] Calculate the transmission distance at impact point i. , ;

[0148] Based on the equal-length round-trip laying method of the sensing fiber, a one-dimensional plane coordinate system for the fiber length and the sand trapping plate (18) is established based on piecewise linear interpolation and inter-row turning logic. The mapping relationship between them will Convert to two-dimensional plane coordinates for:

[0149] (12)

[0150] (13)

[0151] (14)

[0152] (15)

[0153] In the formula, Indicates the row number, starting with the row where the transmission fiber originates, and sorted from bottom to top; For offset, it indicates the position at the 1st position. The length of optical fiber already laid within the industry; The length of a single row of sensing optical fiber laid on the sand grain trapping plate;

[0154] Calculate the absolute spatial height corresponding to impact point i. , , The current level height of the sand trapping plate is set on the fixed rod (20) by the height adjustment slider (19).

[0155] Ideally, the host computer establishes a multi-dimensional feature joint database for wind erosion monitoring, including:

[0156] Data can be collected at different height levels by adjusting the height adjustment slider (19);

[0157] Acquire data features of each impact point A multidimensional feature joint database is formed, in which Let i be the impact time corresponding to impact point i;

[0158] Joint statistics of spatial distribution features were performed based on a multi-dimensional feature database to obtain the following charts: height-particle size distribution matrix, feature parameter profile curves, impact hotspot distribution map on the plane of the capture plate, vertical profile curve of sand particle kinetic energy flux as a function of height, histogram of sand particle size distribution at each height level, time variation graph of sand collection amount, and sand quantity statistics table; the degree of wind erosion threat was analyzed.

[0159] The vertical section is arranged according to Divide the height into J intervals (e.g., 0–10cm, 10–20cm, etc.), and calculate the height for each interval. The total number of sand impacts within time T. ; Calculate the kinetic energy flux in height interval j and the total kinetic energy flux of the J height ranges :

[0160] (16)

[0161] (17)

[0162] In the formula, For the kinetic energy of the sand grains, The wind speed corresponding to height range j (can be obtained synchronously from an anemometer at the same location). The effective acquisition area (m²) of the sensing fiber on the sand grain capture plate. For monitoring duration (s); The unit is This indicator directly reflects the impact destructive force of sand particles at this height level.

[0163] Calculate the mass flux in height interval j and the total mass flux of J height intervals :

[0164] ; (18)

[0165] (19)

[0166] In the formula, The kinetic energy of the sand grains;

[0167] Will Convert to units Based on Table 1, the wind erosion modulus is used to query the corresponding wind erosion intensity level and total kinetic energy flux. Whether the corresponding wind erosion intensity levels are consistent, and if the levels are the same, output the wind erosion intensity level (slight, mild, moderate, strong, very strong, severe).

[0168] The assessment of wind erosion intensity mainly relies on the core quantitative indicator of wind erosion modulus, and the intensity level is classified with reference to the national standard for classification and grading of soil erosion (SL 190-2007).

[0169] Core evaluation indicators: sand mass flux (wind erosion modulus) (t / (km²·a)), kinetic energy flux range (W / m²);

[0170] According to the "Classification and Grading Standard for Soil Erosion," based primarily on the annual average wind erosion modulus, wind erosion is classified into six levels: slight, mild, moderate, severe, very severe, and extreme. The specific classifications are shown in Table 1 below.

[0171]

[0172] Table 1

[0173] A second aspect of this invention provides a wind erosion monitoring method based on distributed optical fibers, comprising the following steps:

[0174] Step S1: The acquisition module receives the auxiliary interference signal output by the first balanced photodetector and extracts the periodic feature points with corresponding equal optical frequency variation intervals as external clock trigger sources. Under the triggering action of the external clock trigger source, the acquisition module performs synchronous sampling of the interference beat frequency signal output by the second balanced photodetector with equal optical frequency intervals.

[0175] Step S2: The host computer analyzes the two photoelectric signals to obtain wind erosion monitoring data.

[0176] Demodulate the interferometric beat frequency signal to obtain the dynamic response main frequency and main frequency amplitude when a single sand grain impact event occurs on the sand grain capture plate, and calculate the equivalent diameter of the sand grain corresponding to the impact point.

[0177] Based on the laying pattern of the sensing fiber of the sand grain capture plate, the deployment height of the sand grain capture plate, and the sensing distance of the backscattered Rayleigh signal in the sensing fiber, the two-dimensional coordinates of the impact point on the sand grain capture plate and its absolute spatial height in actual space are determined.

[0178] By adjusting the height adjustment slider, data is collected at different levels of height. The impact time, absolute spatial height, and equivalent diameter of sand grains corresponding to each impact point are used as data features to form a multi-dimensional feature joint database.

[0179] Based on a multidimensional feature database, joint statistics of spatial distribution features are performed to obtain the height-particle size distribution matrix and feature parameter profile curves, thereby analyzing the degree of wind erosion threat.

[0180] Preferably, based on a multi-dimensional feature joint database, joint statistics of spatial distribution features are performed to obtain a height-grain size distribution matrix and feature parameter profile curves, and the degree of wind erosion threat is analyzed, including:

[0181] Data can be collected at different height levels by adjusting the height adjustment slider.

[0182] System continuous uptime Inside, sand grain impact events are recorded, and data characteristics of each impact point are obtained. A multidimensional feature joint database is formed, in which Let i be the impact time corresponding to impact point i;

[0183] Based on a multi-dimensional feature database, joint statistics of spatial distribution features are performed to obtain a height-particle size distribution matrix, feature parameter profile curves, impact hotspot distribution map on the plane of the capture plate, vertical profile curve of sand particle kinetic energy flux as a function of height, and histograms of sand particle size distribution at each height level. The above output results can be directly used for the study of wind and sand movement mechanisms, wind erosion disaster assessment, and evaluation of the effectiveness of sand prevention and fixation projects, and to analyze the degree of wind erosion threat.

[0184] The vertical section is arranged according to Divide the height into J intervals (e.g., 0–10cm, 10–20cm, etc.), and calculate the height for each interval. The total number of sand impacts within time T. ; Calculate the kinetic energy flux in height interval j and the total kinetic energy flux of the J height ranges :

[0185] (20)

[0186] (twenty one)

[0187] In the formula, For the kinetic energy of the sand grains, The wind speed corresponding to height range j (can be obtained synchronously from an anemometer at the same location). The effective acquisition area (m²) of the sensing fiber on the sand grain capture plate. The monitoring duration is in seconds (s). The unit is ;j∈[1,J];This index directly reflects the impact destructive force of sand particles at this height level;

[0188] Calculate the mass flux in height interval j and the total mass flux of J height intervals :

[0189] ; (twenty two)

[0190] (twenty three)

[0191] In the formula, The kinetic energy of the sand grains;

[0192] Will Convert to units Based on Table 1, the wind erosion modulus is used to query the corresponding wind erosion intensity level and total kinetic energy flux. Whether the corresponding wind erosion intensity levels are consistent, and if the levels are the same, output the wind erosion intensity level (slight, mild, moderate, strong, very strong, severe).

[0193] further, Figure 4 It is a wind erosion measurement optical system for Figure 3 A schematic diagram of the real-time measurement results at a certain location (marked as point i) on the medium sand grain capture plate (18). Figure 4 The system demonstrates the localization results of the impact event at point i on the two-dimensional capture plate plane. Based on the mapping relationship between the one-dimensional fiber position and its laying, the system accurately outputs the planar coordinates of the sand grain impact point. This enabled the location of the impact point.

[0194] Furthermore, the amplitude spectrum of the vibration response of the sensing fiber is finally measured by the aforementioned distributed optical fiber-based wind erosion measurement optical system, as shown below. Figure 5 As shown above. Figure 5 Due to the differences in amplitude and frequency response characteristics, this system performs fast Fourier transform analysis on the acquired beat frequency signal to extract the dominant frequency and amplitude characteristics of the vibration signal. Combined with the reference values ​​of particle size and frequency, and particle size and amplitude relationship calculated by model theory, the particle size of the sand grains impacting the optical fiber can be calculated in reverse, thereby realizing the identification of sand grain size distribution.

[0195] Compared with previous wind erosion monitoring systems (such as sand collectors and piezoelectric sensors), the present invention, after adopting the above technical solution, has the following advantages:

[0196] 1. Currently, there is no distributed wind erosion measurement optical system or method that can simultaneously achieve high spatial resolution, multi-parameter sensing (sand grain size, quantity, and impact location), and is suitable for harsh desert environments. This invention fills the technological gap in this field. Utilizing millimeter-level spatial resolution and millisecond-level time response, the system can simultaneously acquire the grain size, quantity, and impact location of sand grains, achieving multi-parameter synchronous sensing of the microscopic processes of wind and sand movement.

[0197] 2. By employing the passive optical fiber described in this invention as the front-end sensing unit, the sand particle capture device requires no power supply, contains no electronic components, and possesses extremely strong resistance to electromagnetic interference, high temperatures, corrosion, and wind and sand abrasion. It is particularly suitable for long-term, continuous monitoring in extreme and harsh environments such as desert hinterlands, solving the technical problems of traditional electronic sensors being easily damaged and experiencing data drift in sandstorm environments.

[0198] 3. The multi-level height-adjustable sand capture plate proposed in this invention can simultaneously monitor the wind-blown sand flow structure from near the ground surface to higher levels, revealing the complex evolution of sand particle size with height. By eliminating the nonlinear effects of the light source in the lower branch section, the sensing accuracy of each sensing point on the long-distance fiber optic link is ensured, providing more effective data support for wind-blown sand physics research and sand control projects.

[0199] This invention constructs a coupled model of sand particle impact and optical fiber vibration, and designs a "serpentine" optical fiber laying scheme integrating sand particle capture and sensing. Utilizing the millimeter-level spatial resolution and millisecond-level response capability of distributed optical fiber sensing technology, it achieves synchronous and distributed sensing of sand particle impact location, size, and quantity. This provides a novel technical means for studying the microscopic mechanisms of wind-blown sand movement and for the scientific evaluation and optimization of windbreak and sand-fixing projects. This invention is used for the synchronous, continuous, and distributed monitoring of sand particle size, quantity, and impact location during wind-blown sand movement, clarifying the specific jump height distribution of sand particles with destructive sizes, and accurately assessing the degree of erosion threat posed by wind-blown sand to different windward surfaces of crops, surface crusts, or engineering facilities. It is applicable to complex and harsh desert environments.

[0200] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A wind erosion monitoring system based on distributed optical fiber, characterized in that, include: A linear tunable laser (1), an optical isolator (2), a first coupler (3), an upper branch, a lower branch, a sand grain capture sensor (16), a photodetector, a data acquisition module (14), and a host computer (15) are arranged in sequence along the optical path of the upper branch: a second coupler (4), a variable attenuator (6), a polarization controller (7), and a third coupler (8); a fourth coupler (9), a delay fiber (10), and a fifth coupler (11) are arranged in sequence along the optical path of the lower branch. The laser output from the linearly tunable laser (1) enters the first coupler (3) through the optical isolator (2), and is proportionally divided into upper branch light and lower branch light, which enter the upper branch and lower branch respectively. In the lower branch, the lower branch light passes through an unbalanced Mach-Zehnder interference structure containing a delay fiber, generating an auxiliary interference signal that is received by the first balanced photodetector (12). In the upper branch, the second coupler (4) divides the upper branch light into a reference light signal and a measurement light signal; the reference light signal passes through a variable attenuator (6) and a polarization controller (7) in sequence to form a reference arm light signal that is input to the third coupler (8); the measurement light signal enters the sensing fiber in the sand grain capture sensing device (16) through a circulator (5), and the generated backscattered Rayleigh signal returns and is input to the third coupler (8) through the circulator (5), where it is coupled with the reference arm light signal at the third coupler (8); the third coupler (8) outputs an interference beat frequency signal that enters the second balanced photodetector (13); The sand capture sensor (16) includes a sand capture device fixing rod (20), a height adjustment slider (19), and a sand capture plate (18); the sand capture plate (18) is fixed on the vertically set fixing rod (20) by the height adjustment slider (19), and the height adjustment slider (19) adjusts the height of the sand capture plate (18) in the vertical direction; the sensing optical fiber is fixed on the surface of the sand capture plate (18) and arranged in a regular manner to form a high-density sensing array; The acquisition module (14) is used to receive the auxiliary interference signal and extract periodic feature points with corresponding equal optical frequency variation intervals as external clock trigger sources; under the triggering action of the external clock trigger source, the acquisition module (14) performs synchronous sampling of the interference beat frequency signal with equal optical frequency intervals; The host computer analyzes the two photoelectric signals to obtain wind erosion monitoring data: Demodulate the interference beat frequency signal, obtain the dynamic response main frequency and main frequency amplitude when a single sand grain impact event occurs on the sand grain capture plate (18), and calculate the equivalent diameter of the sand grain corresponding to the impact point; Based on the laying pattern of the sensing fiber on the sand capture plate (18), the layout height of the sand capture plate (18), and the sensing distance of the backscattered Rayleigh signal in the sensing fiber, the two-dimensional coordinates of the impact point on the sand capture plate (18) and its absolute spatial height in actual space are determined. By adjusting the height adjustment slider (19), data is collected at different levels of height. The impact time, absolute spatial height, and equivalent diameter of sand grains corresponding to each impact point are used as data features to form a multi-dimensional feature joint database. Based on a multidimensional feature database, joint statistics of spatial distribution features are performed to obtain the height-particle size distribution matrix and feature parameter profile curves, thereby analyzing the degree of wind erosion threat.

2. The wind erosion monitoring system based on distributed optical fiber as described in claim 1, characterized in that, The linearly tunable laser (1) outputs a narrow-linewidth laser with a center wavelength located in the optical fiber communication band, which is split into two paths by the first coupler (3) at a ratio of 99:

1.

3. The wind erosion monitoring system based on distributed optical fiber as described in claim 1, characterized in that, The sensing fiber is fixed to the surface of the sand trapping plate (18) by a special adhesive or embedded microgroove; the sand trapping plate (18) is set perpendicular to the ground and the sensing fiber is located on the surface of the windward side.

4. The wind erosion monitoring system based on distributed optical fiber as described in claim 1, characterized in that, The sensing fibers are laid out in a serpentine, close-packed pattern. The spacing D of the sensing fibers on the capture plate surface is related to the spatial resolution of the system. Satisfying Relationships ,in, It is a positive integer. , The speed of light in a vacuum. The effective refractive index of the sensing fiber. This represents the sweep bandwidth of the tunable laser.

5. The wind erosion monitoring system based on distributed optical fiber as described in claim 4, characterized in that, The host computer calculates the equivalent diameter of the sand grains based on the interferometric beat frequency signal, specifically by defining a grain size calculation model, which includes: When the sensing optical fiber is struck by sand grains, generating a vibration signal, the expression for the change in fiber strain is: ; In the formula, The frequency of the sinusoidal vibration that occurs in the sensing optical fiber. Amplitude; Phase modulation of backscattered Rayleigh light signal caused by fiber vibration The expression is: ; In the formula, , These are the elastic coefficients in the direction of sand grain impact and the elastic coefficients perpendicular to the direction of sand grain impact, respectively. The incident wavelength, This represents the physical distance that light travels in an optical fiber. A constant less than 1; Indicates the phase modulation amplitude; Based on the OFDR sensing principle, the backscattered Rayleigh light signal at impact point i on the sensing fiber... Represented as: ; In the formula, Let i be the scattering rate at point i. Let be the amplitude of the incident light field. The initial center frequency of the laser is . Let i be the time delay at point i. The frequency modulation speed of the linearly tunable laser (1) is... Let i be the initial random phase at point i; The backscattered Rayleigh signal at point i is interfered with the reference arm optical signal by the second balanced photodetector (13) to obtain the interference beat frequency signal at point i. : ; Will The signal is Fourier transformed to the frequency domain to obtain the spectrum. : ; ; Amplitude spectrum in the neutral frequency range for: ; In the formula, the main frequency amplitude ; Establish a quantitative relationship between sand grain impact and optical fiber vibration response: When a jumping sand grain impacts an optical fiber perpendicularly, part of its kinetic energy is converted into the local vibrational energy of the optical fiber; the instantaneous impact kinetic energy of the sand grain... Represented as: ; In the formula, d is the equivalent diameter of the sand grain. m is the density of the sand grain, and m is the mass of the sand grain. Here, v is the velocity coefficient, representing wind speed; This represents the elastic modulus of the optical fiber material; The peak vibration strain is obtained by measuring the wind erosion measurement system. , The outer diameter of the optical fiber is the effective length of the fiber that deforms / vibrates when struck by sand. , ; The function defining the equivalent diameter d of a sand grain is: ; In the formula, the main frequency for The maximum value; constant ,constant , It is a proportionality constant; By solving the particle size calculation model, the equivalent diameter d of the sand grain at impact point i is obtained.

6. The wind erosion monitoring system based on distributed optical fiber as described in claim 5, characterized in that, The host computer determines the three-dimensional coordinates of the impact point, including: Calculate the transmission distance at impact point i. , ; Based on the equal-length round-trip laying method of the sensing fiber, a one-dimensional plane coordinate system for the fiber length and the sand trapping plate (18) is established based on piecewise linear interpolation and inter-row turning logic. The mapping relationship between them will Convert to two-dimensional plane coordinates for: ; ; ; ; In the formula, Indicates the row number, starting with the row where the transmission fiber originates, and sorted from bottom to top; For offset, it indicates the position at the 1st position. The length of optical fiber already laid within the industry; The length of a single row of sensing optical fiber laid on the sand grain trapping plate; Calculate the absolute spatial height corresponding to impact point i. , , The current level height of the sand trapping plate is set on the fixed rod (20) by the height adjustment slider (19).

7. The wind erosion monitoring system based on distributed optical fiber as described in claim 6, characterized in that, The host computer establishes a multi-dimensional feature joint database for wind erosion monitoring, including: Data can be collected at different height levels by adjusting the height adjustment slider (19); Acquire data features of each impact point A multidimensional feature joint database is formed, in which Let i be the impact time corresponding to impact point i; Based on a multi-dimensional feature database, joint statistics of spatial distribution features were performed to obtain a height-particle size distribution matrix, feature parameter profile curves, impact hotspot distribution map on the plane of the capture plate, vertical profile curve of sand particle kinetic energy flux as a function of height, and histograms of sand particle size distribution at each height level, thereby analyzing the degree of wind erosion threat. The vertical section is arranged according to Divide the height into J height intervals and calculate the height of each interval. The total number of sand impacts within time T. ; Calculate the kinetic energy flux in height interval j and the total kinetic energy flux of the J height ranges : ; ; In the formula, For the kinetic energy of the sand grains, Let j be the wind speed corresponding to the altitude range. This represents the effective acquisition area of ​​the sensing fiber on the sand grain capture plate. For monitoring duration; j∈[1,J]; Calculate the mass flux in height interval j and the total mass flux of J height intervals : ; ; ; In the formula, The kinetic energy of the sand grains; Will Convert to the current wind erosion modulus, and query the corresponding wind erosion intensity level and total kinetic energy flux for the current wind erosion modulus. Check if the corresponding wind erosion intensity levels are consistent, and output the wind erosion intensity level if the levels are the same.

8. A wind erosion monitoring method based on distributed optical fiber, characterized in that, The implementing entity is the wind erosion monitoring system based on distributed optical fiber as described in any one of claims 1-7, and the steps include: Step S1: The acquisition module receives the auxiliary interference signal output by the first balanced photodetector and extracts the periodic feature points with corresponding equal optical frequency variation intervals as external clock trigger sources. Under the triggering action of the external clock trigger source, the acquisition module performs synchronous sampling of the interference beat frequency signal output by the second balanced photodetector with equal optical frequency intervals. Step S2: The host computer analyzes the two photoelectric signals to obtain wind erosion monitoring data. Demodulate the interferometric beat frequency signal to obtain the dynamic response main frequency and main frequency amplitude when a single sand grain impact event occurs on the sand grain capture plate, and calculate the equivalent diameter of the sand grain corresponding to the impact point. Based on the laying pattern of the sensing fiber of the sand grain capture plate, the deployment height of the sand grain capture plate, and the sensing distance of the backscattered Rayleigh signal in the sensing fiber, the two-dimensional coordinates of the impact point on the sand grain capture plate and its absolute spatial height in actual space are determined. By adjusting the height adjustment slider, data is collected at different levels of height. The impact time, absolute spatial height, and equivalent diameter of sand grains corresponding to each impact point are used as data features to form a multi-dimensional feature joint database. Based on a multidimensional feature database, joint statistics of spatial distribution features are performed to obtain the height-particle size distribution matrix and feature parameter profile curves, thereby analyzing the degree of wind erosion threat.

9. The wind erosion monitoring method based on distributed optical fiber according to claim 8, characterized in that, Based on a multi-dimensional feature database, joint statistics of spatial distribution characteristics were performed to obtain the height-grain size distribution matrix and characteristic parameter profile curves, and the degree of wind erosion threat was analyzed, including: Data can be collected at different height levels by adjusting the height adjustment slider. Acquire data features of each impact point A multidimensional feature joint database is formed, in which Let i be the impact time corresponding to impact point i; Based on a multi-dimensional feature database, joint statistics of spatial distribution features were performed to obtain a height-particle size distribution matrix, feature parameter profile curves, impact hotspot distribution map on the plane of the capture plate, vertical profile curve of sand particle kinetic energy flux as a function of height, and histograms of sand particle size distribution at each height level, thereby analyzing the degree of wind erosion threat. The vertical section is arranged according to Divide the height into J height intervals and calculate the height of each interval. The total number of sand impacts within time T. ; Calculate the kinetic energy flux in height interval j and the total kinetic energy flux of the J height ranges : ; ; In the formula, For the kinetic energy of the sand grains, Let j be the wind speed corresponding to the altitude range. This represents the effective acquisition area of ​​the sensing fiber on the sand grain capture plate. For monitoring duration; j∈[1,J]; Calculate the mass flux in height interval j and the total mass flux of J height intervals : ; ; ; In the formula, The kinetic energy of the sand grains; Will Convert to the current wind erosion modulus, and query the corresponding wind erosion intensity level and total kinetic energy flux for the current wind erosion modulus. Check if the corresponding wind erosion intensity levels are consistent, and output the wind erosion intensity level if the levels are the same.

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