A distributed vector acoustic wave sensor

Abstract

The application belongs to the technical field of acoustic wave fiber sensing, and particularly relates to a distributed vector acoustic wave sensor, which comprises: a hollow waveguide, at least one particle being suspended in the hollow waveguide; a laser; an incident light splitting module, which is used for splitting the laser into two beams of manipulation light and respectively incident from two ends of the hollow waveguide, the two beams of manipulation light respectively acting on two sides of the particle to adjust the position of the particle in the axial direction of the hollow waveguide; a scattered light splitting module, which splits the scattered light into two beams of light, one of which is connected with an imaging system one, and the other of which is connected with a position detection system; and a scattered light analysis module, which is used for splitting the scattered light into two beams of light, one of which is connected with an imaging system two, and the other of which is connected with a Doppler analysis system. The application can realize the function of vector acoustic wave measurement by analyzing the motion information such as the oscillation direction, oscillation frequency and oscillation speed of the particle.

Description

Technical Field

[0001] This invention belongs to the field of sensing technology, and in particular relates to a distributed vector acoustic wave sensor. Background Technology

[0002] As an important branch of the sensing field, the continuous improvement of hollow fiber optic sensors in terms of structure and function is an inevitable trend. Hollow fiber optic particle sensors are an emerging distributed sensing platform that has seen rapid development in the field of distributed acoustic wave measurement. Since multi-component acoustic wave measurement can more realistically reflect the sound field distribution in space, methods and technologies for measuring vector acoustic waves using hollow fiber optic particle sensors still need further exploration.

[0003] Existing fiber-optic distributed acoustic sensing technology relies on the photoelastic effect of solid-core optical fibers to alter the local refractive index, introducing changes in optical path difference. It only responds to acoustic wave components incident along the fiber axis. This limits its ability to measure multiple components, restricting its application in fields such as oil and gas exploration and seismic wave detection. While researchers have proposed a spiral-wound fiber deployment scheme to address vector measurement, this scheme suffers from high cabling complexity and requires precise winding angles. L-shaped cabling can achieve spatial inverse kinematics for multiple acoustic components in fiber-optic distributed sensing, but requires a large number of cables.

[0004] To address the challenges of vector acoustic wave measurement in fiber optic distributed sensing technology, this invention proposes a distributed vector acoustic wave sensor. Summary of the Invention

[0005] The purpose of this invention is to provide a distributed vector acoustic wave sensor to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A distributed vector acoustic wave sensor, comprising:

[0008] A hollow waveguide, wherein at least one particle is suspended in the hollow waveguide;

[0009] A laser, used to emit laser light;

[0010] An incident beam splitter module is provided, wherein the incident end of the incident beam splitter module is connected to the optical path of the output end of the laser. The incident beam splitter module is used to split the laser into two beams of manipulation light and respectively incident from both ends of the hollow waveguide. The two beams of manipulation light act on both sides of the particle to adjust the position of the particle in the direction of the hollow waveguide axis.

[0011] The scattered light beam splitting module has its incident end connected to the scattered light optical path on the particle surface. The scattered light beam splitting module splits the scattered light into two beams, one of which is connected to the imaging system and the other is connected to the position detection system.

[0012] The scattered light analysis module has its incident end connected to the scattered light path on the particle surface. The scattered light analysis module is used to split the scattered light into two beams, one of which is connected to the imaging system and the other beam is connected to the Doppler analysis system.

[0013] Optionally, the incident light beam splitter module includes:

[0014] A half-wave plate, the incident end of which is connected to the optical path of the laser's output end;

[0015] The incident end of the polarizing beam splitter is connected to the optical path of the exit end of the half-wave plate. The polarizing beam splitter is used to split the incident light into a control optical path one and a control optical path two.

[0016] The manipulation optical path is reflected by several mirrors and then incident on one end of the hollow waveguide through a coupling lens.

[0017] The second manipulation optical path is reflected by several other mirrors and then incident on the other end of the hollow waveguide through another coupling lens.

[0018] The first control optical path and the second control optical path are coaxially arranged.

[0019] Optionally, the scattered light beam splitter module includes:

[0020] The objective lens, with its incident end connected to the optical path of the scattered light from the particle;

[0021] Beam splitter one has its incident end connected to the optical path of the exit end of the objective lens. The beam splitter one is used to split the scattered light into a first scattered light path and a second scattered light path. The first scattered light path is connected to the optical path of the imaging system, and the second scattered light path is connected to the optical path of the position detection system.

[0022] Optionally, the location detection system includes:

[0023] Focusing lens one, the incident end of which is connected to the second scattering light path;

[0024] A four-quadrant position detector, wherein the incident end of the four-quadrant position detector is connected to the optical path of the exit end of the focusing lens one.

[0025] Optionally, the scattered light analysis module includes:

[0026] Beam splitter 2 is disposed between any set of the reflectors and the coupling lens. The manipulation optical path 1 or manipulation optical path 2 passes through the corresponding beam splitter 2 and is incident on the end of the hollow waveguide. The scattered light of the particle is incident on the reflective surface of the beam splitter 2 through the coupling lens to form a scattered optical path 3.

[0027] Beam splitter three has its incident end connected to the optical path of the scattering light path three. The beam splitter three is used to divide the scattering light path three into scattering light path four and scattering light path five. Scattering light path four is connected to the optical path of the Doppler analysis system, and scattering light path five is connected to the optical path of the imaging system two.

[0028] Optionally, the Doppler analysis system includes:

[0029] Focusing mirror two, the incident end of which is connected to the four optical paths of the scattering light path;

[0030] A photodetector, wherein the incident end of the photodetector is connected to the exit end of the focusing lens 2.

[0031] Optionally, the imaging system includes a camera, and the shooting end of the camera is connected to the optical path of the scattering optical path.

[0032] The imaging system two includes a camera two, and the shooting end of the camera two is connected to the scattering light path five.

[0033] Optionally, the particulate material comprises at least one of dielectric material, crystalline material, semiconductor material, metallic material, and biomaterial;

[0034] The hollow waveguide is one of hollow photonic bandgap fiber, capillary fiber, hollow anti-resonant fiber or porous fiber.

[0035] The objective lens has a magnification of 10× to 100×.

[0036] Optionally, the bandwidth of the four-quadrant position detector is not less than 10 kHz.

[0037] Optionally, the sampling rate of the four-quadrant position detector is greater than twice the particle vibration frequency.

[0038] Compared with the prior art, the present invention has the following advantages and technical effects:

[0039] In use, this invention involves placing at least one particle within a hollow waveguide. After laser light is emitted, it is split into two manipulating beams by an incident light beam splitter module, which then illuminate both ends of the hollow waveguide. These two manipulating beams act on the sides of the particle to adjust its position along the waveguide's axis. A scattered light beam splitter module collects the scattered light from the particle's surface. One scattered beam is connected to an imaging system, and the other is connected to a position detection system. When the particle is disturbed by acoustic waves, the scattered light contains information about the particle's motion. The scattered light can be collected from the side by the imaging and position detection systems. By analyzing the particle's oscillation direction, frequency, and velocity, vector acoustic wave measurement can be achieved. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the structure of the present invention;

[0042] Figure 2 This is a schematic diagram illustrating the forced vibration principle of the particles in the hollow waveguide of this invention.

[0043] Figure 3 This is a schematic diagram illustrating the principle of particle vector measurement and distributed measurement in this invention.

[0044] Figure 4 These are diagrams illustrating the end-face structures of different types of hollow waveguides according to the present invention.

[0045] Among them, 1. Laser; 2. Half-wave plate; 3. Polarizing beam splitter; 4. Mirror; 5. Coupler lens; 6. Hollow waveguide; 7. Particle; 8. Objective lens; 9. Beam splitter one; 10. Camera one; 11. Focusing lens one; 12. Four-quadrant position detector; 13. Beam splitter two; 14. Beam splitter three; 15. Camera two; 16. Focusing lens two; 17. Photodetector. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Reference Figures 1 to 4 This invention discloses a distributed vector acoustic wave sensor, comprising:

[0049] Hollow waveguide 6, with at least one particle 7 suspended in the hollow waveguide 6;

[0050] Laser 1, used to emit laser light;

[0051] An incident beam splitter module is provided, with its incident end connected to the output end of the laser 1. The incident beam splitter module is used to split the laser into two beams of manipulation light, which are then incident from both ends of the hollow waveguide 6. The two beams of manipulation light act on both sides of the particle 7 to adjust the position of the particle 7 in the axial direction of the hollow waveguide 6.

[0052] The scattered light beam splitting module has its incident end connected to the scattered light optical path on the surface of particle 7. The scattered light beam splitting module splits the scattered light into two beams. One beam is connected to the imaging system and the other beam is connected to the position detection system.

[0053] The scattered light analysis module is connected to the incident end of the scattered light path on the surface of particle 7. The scattered light analysis module is used to split the scattered light into two beams, one of which is connected to the imaging system 2, and the other beam is connected to the Doppler analysis system.

[0054] In use, this invention involves placing at least one particle 7 within a hollow waveguide 6. After laser light is emitted from a laser 1, it is split into two manipulating beams by an incident light beam splitting module, which then illuminate both ends of the hollow waveguide 6. These two manipulating beams act on the sides of the particle 7 to adjust its position along the axial direction of the hollow waveguide 6. A scattered light beam splitting module collects the scattered light from the particle 7's surface. One scattered light beam is connected to an imaging system, and the other is connected to a position detection system. When the particle 7 is disturbed by acoustic waves, the scattered light contains information about the particle's motion. The scattered light from the particle 7 can be collected from the side by the imaging system and the position detection system. By analyzing the particle 7's oscillation direction, frequency, and velocity, vector acoustic wave measurement can be achieved. A scattered light analysis module collects the scattered light after the particle has propagated through the hollow waveguide 6. This scattered light is split into two beams, one connected to an imaging system, and the other connected to a Doppler analysis system. When particle 7 is disturbed by acoustic waves, the axial and radial motion information of particle 7 in the hollow waveguide can be analyzed, thereby realizing the distributed vector acoustic wave measurement function.

[0055] As an optional implementation, the incident light beam splitter module includes:

[0056] Half-wave plate 2, the incident end of which is connected to the optical path of the output end of laser 1;

[0057] The incident end of the polarizing beam splitter 3 is connected to the optical path of the output end of the half-wave plate 2. The polarizing beam splitter 3 is used to split the incident light into two control optical paths: control optical path one and control optical path two.

[0058] The manipulating optical path 1 is reflected by several mirrors 4 and then incident on one end of the hollow waveguide 6 through the coupling lens 5;

[0059] The second optical path is reflected by several other mirrors 4 and then incident on the other end of the hollow waveguide 6 through another coupling lens 5;

[0060] The first and second control optical paths are set coaxially.

[0061] As an optional implementation, the scattered light beam splitter module includes:

[0062] Objective lens 8, the incident end of which is connected to the optical path of the scattered light from particle 7;

[0063] Beam splitter 9 has its incident end connected to the exit end of objective lens 8. Beam splitter 9 is used to split the scattered light into scattered light path one and scattered light path two. Scattered light path one is connected to the optical path of the imaging system, and scattered light path two is connected to the optical path of the position detection system.

[0064] As an optional implementation, the location detection system includes:

[0065] Focusing lens 11, the incident end of focusing lens 11 is connected to the second optical path of the scattering light path;

[0066] The four-quadrant position detector 12 has its incident end connected to the output end of the focusing lens 11 via an optical path.

[0067] As an optional implementation, the scattered light analysis module includes:

[0068] Beam splitter 2 13 is set between any set of reflectors 4 and coupling lens 5. The optical path 1 or optical path 2 is manipulated to pass through the corresponding beam splitter 2 13 and be incident on the end of the hollow waveguide 6. The scattered light of the particle 7 is incident on the reflective surface of beam splitter 2 13 through coupling lens 5 to form scattered light path 3.

[0069] Beam splitter 314 has its incident end connected to the three-way scattered light path. Beam splitter 314 is used to split the three-way scattered light path into the four-way scattered light path and the five-way scattered light path. The four-way scattered light path is connected to the optical path of the Doppler analysis system, and the five-way scattered light path is connected to the optical path of the two-way imaging system.

[0070] As an optional implementation, the Doppler analysis system includes:

[0071] Focusing lens 216, the incident end of focusing lens 216 is connected to the four-way scattered light path;

[0072] The photodetector 17 is connected to the optical path of the output end of the focusing lens 16.

[0073] As an optional implementation, the imaging system includes a camera 10, the imaging end of which is connected to the optical path of the scattering light path.

[0074] Imaging system 2 includes camera 2 15, and the shooting end of camera 2 15 is connected to the diffused light path 5.

[0075] As an optional implementation, the particle 7 material includes at least one of dielectric material, crystalline material, semiconductor material, metallic material, and biological material;

[0076] Hollow waveguide 6 is one of hollow photonic bandgap fiber, capillary fiber, hollow anti-resonant fiber or porous fiber.

[0077] Objective lens 8 has a magnification of 10× to 100×.

[0078] As an optional implementation, the bandwidth of the four-quadrant position detector 12 is not less than 10 kHz.

[0079] As an alternative implementation, the sampling rate of the four-quadrant position detector 12 is greater than twice the vibration frequency of the particle 7.

[0080] The distributed vector acoustic fiber optic sensor consists of a laser 1, a half-wave plate 2, a polarizing beam splitter 3, a reflector 4, a coupling lens 5, a hollow waveguide 6, a particle 7, an objective lens 8, a beam splitter 1 9, a camera 1 10, a focusing lens 1 11, a four-quadrant position detector 12, a beam splitter 2 13, a beam splitter 3 14, a camera 2 15, a focusing lens 2 16, and a photodetector 17.

[0081] Laser 1 serves as the source of the manipulating light. The laser beam is split into two beams with adjustable relative power by passing through a half-wave plate 2 and a polarizing beam splitter 3. These two beams then pass through a coupling lens 5 and enter a hollow waveguide 6 to become the manipulating light capable of controlling particles 7. When particle 7 is disturbed by acoustic waves, the scattered light from particle 7 contains information about the particle's motion. The scattered light from particle 7 can be collected laterally by imaging system one and a position detection system. After propagating through the hollow waveguide, the scattered light from particle 7 can be collected by imaging system two and a Doppler analysis system.

[0082] The imaging system includes an objective lens 8, a beam splitter 9, and a camera 10, which can intuitively and in real time reflect information such as the motion direction of the particles 7.

[0083] The position detection system includes a focusing lens 11 and a four-quadrant position detector 12. By analyzing the voltage signal of the four-quadrant position detector 12, more motion information of the particles can be obtained, which can reflect vector sound wave information.

[0084] The Doppler analysis system includes a focusing mirror 16 and a photodetector 17. By analyzing the collected scattered and non-scattered light, information such as the radial and axial positions of particle 7 in the hollow waveguide can be obtained.

[0085] This distributed vector acoustic wave fiber optic sensor achieves distributed functionality by modulating the optical power of two manipulation beams to adjust the position, oscillation frequency, direction of motion, and velocity of particle 7. The motion information, such as the oscillation direction, frequency, and velocity of particle 7, detected by the four-quadrant position detector 12, enables vector acoustic wave measurement. Based on the scattered light analysis module and using Doppler velocimetry, the instantaneous velocity of particle 7 can be extracted from the beat frequency signal, and further integration over time yields the particle's position information. Combined with vector acoustic wave detection technology, distributed vector acoustic wave detection functionality can be realized.

[0086] The following section will elaborate on the principle of using particle vibration to detect vector sound waves.

[0087] The motion of particle 7 is affected by sound waves. The sound pressure F generated by the sound waves on particle 7 A The balance between the optical gradient force F provided by the laser in the core of the hollow waveguide 6, the particle's gravity G, and the air resistance f results in the suspended particle 7 having an intrinsic vibrational angular frequency ω0. When a sound wave applies periodic acoustic pressure to the particle 7, the particle 7 will be forced to vibrate. Damped forced vibration causes the particle to undergo simple harmonic motion under the action of a continuous periodic external force. The particle 7 will then reach a vibrational steady state.

[0088]

[0089] Where X0 is the amplitude in the steady state, ω is the angular frequency of the external force, and t is time. This is the vibration phase.

[0090] 1. When the frequency of the periodic sound pressure is much smaller than the intrinsic vibration angular frequency ω0, this frequency region is called the low-frequency region. At this time, the period of the external periodic sound pressure tends to be infinite, which can be equivalent to a constant force. In this region, the particle amplitude is the displacement X of the particle from the center of the optical trap.

[0091] 2. When the frequency of the periodic sound pressure is much greater than the intrinsic vibration angular frequency ω0, this region is called the high-frequency region. In the high-frequency region, the forced vibration is opposite to the direction of the sound pressure. As the sound wave frequency increases, the particle amplitude X0 decreases and gradually approaches 0.

[0092] 3. When the frequency of the sound wave approaches the intrinsic vibration angular frequency ω0, this frequency region is called the resonance region. In the low and high frequency regions, damping has a weak effect on particle amplitude, but in the resonance region, the damping of the medium surrounding the particle has a significant suppressive effect on particle amplitude. When the particle is in a low-damping condition (damping ratio...), When n is a damping parameter, the particle amplitude X0 will increase significantly; when the particle is in the critical damping and high damping conditions (damping ratio ε≥1), the particle amplitude X0 will not increase.

[0093] The direction of motion of particle 7 is related to the direction of acoustic pressure. By monitoring the amplitude of particle 7 in the axial and radial directions of the hollow waveguide 6, the direction of the sound wave can be calculated, thereby achieving the purpose of vector measurement.

[0094] The above indicates that the motion state of particle 7 is affected by the direction, frequency, and magnitude of the sound wave, as well as the damping of the surrounding environment. Therefore, this system can be used to detect the direction, frequency, intensity, environmental damping, and air pressure of the sound wave. When particle 7 is under low damping, the frequency response characteristics of the sensor can be dynamically adjusted by regulating the mass of particle 7 and the intensity of the captured light. The resonance region will increase the particle amplitude and improve the system sensitivity.

[0095] The particle size and material of particle 7 can be selected from a wide range, including dielectric materials, metallic materials, semiconductor materials, and biological materials. This broadens the application range of the sensor, and the system can have electromagnetic sensing functions depending on the selection of particle 7. By detecting the vibration direction of particle 7, the direction of the vector to be measured can be detected. By modulating the relative light intensity at both ends of the optical fiber, the axial position of the particle in the optical fiber can be changed, which enables the sensor to have distributed sensing capabilities. When multiple particles 7 are suspended in the core of a hollow waveguide, each particle can be regarded as a multi-component sensing oscillator, enabling some measurement positioning functions.

[0096] Based on the scattered light analysis module, the distributed sensing principle of the sensor will be explained in detail below:

[0097] Based on laser Doppler velocimetry, the instantaneous axial velocity of a particle can be measured, and the position information of the suspended particle can be obtained by integrating the instantaneous velocity over time. The axial position of the particle within the fiber can be varied by modulating the relative light intensity at both ends. Since the backscattered light from the particle exhibits a Doppler frequency shift relative to the incident light during its motion, the instantaneous velocity of the particle can be calculated by measuring the instantaneous Doppler frequency shift value in the signal received by the photodetector.

[0098] When particles propagate in an optical fiber, due to the Doppler effect, particles farther from the light source cause the light frequency to be lower than the light source frequency υ. L occur The light frequency then shifts further away from the fixed photodetector (PD) due to a redshift; subsequently, the particles moving away from the fixed photodetector (PD) cause the light frequency to change further. The redshift. Therefore, for non-relativistic particle velocities, the frequency of the reflected light from the particle is The frequency difference between the emitted light and the incident light is:

[0099]

[0100] Among them, v p Let Δυ be the velocity of the suspended particles. D This represents the frequency difference between the reflected light from the moving particle and the reflected light from the fiber endface. Therefore, the beat frequency between the particle's reflected light and the fiber endface, detected by the PD, can be used to quickly deduce the particle's velocity information. Further integration of the particle's velocity over time yields its position information. Simultaneously, the light intensity changes monitored by the PD can be used to calculate the particle's radial position change within the hollow waveguide. Combining this position detection technology with vector acoustic wave detection technology in the device enables the sensor's distributed sensing function.

[0101] Furthermore, hollow waveguides operate in a low-loss region in the optical manipulation band, and the fiber structure is not fixed.

[0102] Furthermore, the wavelength of the captured light is not fixed.

[0103] Furthermore, the sampling frequency of the position detection system is more than twice the particle vibration frequency.

[0104] In this embodiment of the invention, laser 1, acting as a light source, emits laser light which is split into two manipulating beams by a half-wave plate 2 and a polarizing beam splitter 3. The two beams are then collimated by a reflecting mirror 4 and coupled into the fiber core from both ends of a hollow waveguide 6 using coupling lenses 5. Particle 7 is captured by the two beams and suspended within the hollow waveguide 6.

[0105] By adjusting the power ratio of the two beams, the axial speed and direction of particle 7 can be controlled. By placing particle 7 at different axial positions in hollow waveguide 6, sound waves at different spatial positions can be monitored.

[0106] The radial intrinsic vibration frequency and amplitude of particle 7 can be controlled by controlling the total laser power.

[0107] The scattered light from particle 7 is received by the high-power objective lens 8 on the side and then split into two beams by the beam splitter 9. One beam is collected by the camera 10, and the other beam is focused by the focusing lens 11 into the four-quadrant position detector 12.

[0108] By analyzing the vibration frequency and amplitude of particle 7 in the axial and radial directions of the optical fiber monitored by the four-quadrant position detector 12, the direction, frequency and intensity of the sound wave can be detected.

[0109] The output light spot of the hollow waveguide 6 is collected by the coupling lens 5 and reflected by the beam splitter 13 to the beam splitter 14. The scattered light is split into two beams by the beam splitter 14. One beam is collected by the camera 15, and the other beam is focused by the focusing lens 16 into the photodetector 17.

[0110] By analyzing the changes in the shape of the scattered light spot output from the hollow waveguide monitored by camera 215, the changes in the radial position of the particles along the hollow waveguide can be detected.

[0111] By analyzing the scattered light of particle 7 monitored by photodetector 17, the position of the particle along the axial and radial directions of the hollow waveguide can be detected.

[0112] The construction of a distributed vector acoustic fiber optic sensor can be divided into the following steps:

[0113] Step 1, beam collimation and laser coupling: The laser emitted by the laser 1 is split by the polarizing beam splitter 3, and the two beams are adjusted by several mirrors 4 to be two coaxial beams facing each other. Then, the fundamental mode coupling of the hollow waveguide 6 is performed by selecting a coupling lens 5 with a suitable focal length.

[0114] Step 2, Particle Axial Position Control: Adjust the relative light intensity of the two beams using half-wave plate 2 and polarizing beam splitter 3, and rotate half-wave plate 2 to make particle 7 move along the fiber axis.

[0115] Step 3: Construction of a real-time monitoring system for the lateral motion of particles: The scattered light from particle 7 is collected by the high-power objective lens 8 and the lens group, and split by the beam splitter 9. One of the scattered lights is focused on camera 10, and the vibration state of the particle is presented in real time by camera 1.

[0116] Step 4: Construction of the particle axial and radial motion position signal acquisition system: The scattered light from particle 7 is focused into the four-quadrant position detector 12 after being split by beam splitter 9, and the axial and radial motion signals of particle 7 are acquired.

[0117] Step 5: Setting up the scattered light analysis module: The scattered and unscattered light from the particles in the hollow waveguide is collected by coupling lens 5 and reflected by beam splitter 13 to beam splitter 14, where it is split into two scattered beams. One scattered beam is collected by camera 15, and the other is focused by focusing lens 16 into photodetector 17. The change signal of the output light of the hollow waveguide caused by particle 7 is collected, and the vibration information of the particles is further analyzed. Furthermore, the transmission-reflection ratio of polarization beam splitter 3, beam splitter 9, and beam splitter 13 is one of 50:50, 70:30, or 90:10.

[0118] Furthermore, the hollow waveguide 6 is of one type: hollow photonic bandgap fiber, capillary fiber, hollow anti-resonant fiber, or porous fiber. Figure 4Cross-sectional microscope images of capillary fiber, hollow photonic bandgap fiber, and hollow anti-resonant fiber are given; the air core shape and aperture of hollow waveguide 6 are not limited.

[0119] Furthermore, the particle 7 material can be one of dielectric materials, crystal materials, semiconductor materials, biomaterials, or a mixture of the above materials.

[0120] Furthermore, the magnification of objective lens 8 is one of 10× to 100× depending on the size of particle 7.

[0121] Furthermore, the bandwidth of the four-quadrant position detector 12 is either 100kHz or 150kHz, and the sampling rate is set to be more than twice the particle vibration frequency.

[0122] To facilitate understanding of the present invention, specific embodiments are described below. The present invention is not limited to the embodiments described below.

[0123] Step 1: Beam Collimation and Coupling: Remove the coating from the hollow waveguide 6 (cladding diameter 285μm, core diameter 30μm) and flatten the fiber end face. Hollow waveguide 6 is a hollow anti-resonant fiber. Adjust the two opposing beams and the fiber to be coaxial, and use a coupling lens to couple the beams into the fiber as the fundamental mode.

[0124] Step 2, Particle 7 Suspension and Axial Position Adjustment: A suitable amount of particles 7 are sprayed onto the end face of the hollow waveguide 6. The particles 7 are propelled into the fiber core of the hollow waveguide 6 by optical force. Rotating the half-wave plate 2 can adjust the light intensity at both ends of the beam, so that the particles 7 are suspended in the fiber core of the hollow waveguide 6 and the axial position of the particles can be adjusted.

[0125] Step 3: Adjustment of the particle 7 motion state information acquisition system: When particle 7 is suspended at a specific position, a sound wave is applied to particle 7. The direction and amplitude of the sound wave affect the vibration direction and amplitude of particle 7. Scattered light from particle 7 is collected from the side of the optical fiber. The scattered light passes through objective lens 8 and beam splitter 9 and enters camera 10, thereby realizing real-time monitoring of particle motion direction and velocity. Another beam of scattered light is reflected by beam splitter 9 and focused by focusing lens 11 and collected by four-quadrant position detector 12. Four-quadrant position detector 12 can output an electrical signal containing the position of particle 7 and the intensity signal of scattered light from particle 7. By analyzing the amplitude ratio of particle 7's axial and radial motion, the motion direction of particle 7 can be determined and the direction of the sound wave can be inferred. The output signal of four-quadrant position detector 12 also contains the amplitude and vibration velocity of particle 7, and the direction, amplitude, frequency, and other information of the sound wave can be resolved.

[0126] Step 4: Adjustment of the system for obtaining the axial movement position of particle 7 in the hollow waveguide: After the 1064nm laser is coupled into the fiber core, the suspended particle far from the light source will generate Doppler frequency-shifted light. The beat frequency signal generated by this frequency-shifted light and the non-frequency-shifted light is received by the photodetector. The particle's velocity is extracted from this signal, and the particle's position is obtained by integrating this velocity over time, thus realizing distributed sensing.

[0127] Compared with existing distributed acoustic fiber optic sensing technology, the solution conceived in this invention has the following advantages:

[0128] 1. Because the sensing element of this sensor is a suspended particle, compared with the existing distributed acoustic fiber optic sensors, the sensing parameters and performance indicators of this sensor can overcome the limitations of the quartz fiber itself.

[0129] 2. Compared with existing distributed acoustic fiber optic sensors, this sensor can realize vector acoustic wave detection function using a single hollow waveguide, and can achieve high-precision vector acoustic wave detection under relatively simple deployment conditions.

[0130] 3. Compared with existing distributed acoustic fiber optic sensors, this sensor has the advantages of high spatial resolution, high sensitivity, and high integration.

[0131] 4. Compared with existing fiber optic sensors, this sensor is more flexible as it can change the suspended particles according to the measurement.

[0132] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0133] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A distributed vector acoustic wave sensor, characterized in that, include: Hollow waveguide (6), wherein at least one particle (7) is suspended in the hollow waveguide (6); Laser (1), used to emit laser light; An incident beam splitter module is provided, wherein the incident end of the incident beam splitter module is connected to the output end of the laser (1) optical path. The incident beam splitter module is used to split the laser into two beams of manipulation light and respectively incident from both ends of the hollow waveguide (6). The two beams of manipulation light act on both sides of the particle (7) to adjust the position of the particle (7) in the axial direction of the hollow waveguide (6). The incident end of the scattered light beam splitting module is connected to the scattered light optical path on the surface of the particle (7). The scattered light beam splitting module splits the scattered light into two beams, one of which is connected to the imaging system and the other is connected to the position detection system. The scattered light analysis module is connected at the incident end to the scattered light path on the surface of the particle (7). The scattered light analysis module is used to split the scattered light into two beams, one of which is connected to the imaging system II, and the other beam is connected to the Doppler analysis system. The incident light beam splitter module includes: The half-wave plate (2) is connected at the incident end to the optical path of the output end of the laser (1); The incident end of the polarizing beam splitter (3) is connected to the optical path of the exit end of the half-wave plate (2). The polarizing beam splitter (3) is used to split the incident light into a manipulation optical path one and a manipulation optical path two. The manipulation optical path is reflected by several mirrors (4) and then incident on one end of the hollow waveguide (6) through a coupling lens (5); The second manipulation optical path is reflected by several other mirrors (4) and then incident on the other end of the hollow waveguide (6) through another coupling lens (5); The first control optical path and the second control optical path are coaxially arranged; The scattered light beam splitter module includes: The objective lens (8) is connected at its incident end to the optical path of the scattered light from the particle (7); Beam splitter 1 (9) has its incident end connected to the output end of the objective lens (8) via optical path. The beam splitter 1 (9) is used to split the scattered light into a first scattered light path and a second scattered light path. The first scattered light path is connected to the optical path of the imaging system 1, and the second scattered light path is connected to the optical path of the position detection system. The location detection system includes: Focusing lens one (11), the incident end of the focusing lens one (11) is connected to the second scattering light path; The four-quadrant position detector (12) is connected to the output optical path of the focusing lens (11). The scattered light analysis module includes: Beam splitter 2 (13) is disposed between any set of the reflectors (4) and the coupling lens (5). The manipulation optical path 1 or manipulation optical path 2 passes through the corresponding beam splitter 2 (13) and is incident on the end of the hollow waveguide (6). The scattered light of the particle (7) is incident on the reflective surface of the beam splitter 2 (13) through the coupling lens (5) to form the scattered optical path 3. Beam splitter three (14) has its incident end connected to the optical path of the scattering optical path three. The beam splitter three (14) is used to divide the scattering optical path three into scattering optical path four and scattering optical path five. The scattering optical path four is connected to the optical path of the Doppler analysis system, and the scattering optical path five is connected to the optical path of the imaging system two. The Doppler analysis system includes: Focusing lens two (16), the incident end of the focusing lens two (16) is connected to the four optical paths of the scattering light path; Photodetector (17), the incident end of which is connected to the output end of focusing lens (16) in the optical path; The imaging system includes a camera (10), and the shooting end of the camera (10) is connected to the optical path of the scattering optical path. The imaging system 2 includes a camera 2 (15), and the shooting end of the camera 2 (15) is connected to the scattering light path 5. In use, at least one particle (7) is arranged in the hollow waveguide (6). After the laser (1) emits laser light, the laser light is split into two beams of manipulation light by the incident light beam splitting module and respectively irradiates the two ends of the hollow waveguide (6). The two beams of manipulation light act on both sides of the particle (7) to adjust the position of the particle (7) in the axial direction of the hollow waveguide (6). The scattered light beam splitting module collects the scattered light on the surface of the particle (7). One of the scattered light beams is connected to the imaging system and the other scattered light beam is connected to the position detection system. When the particle (7) is disturbed by sound waves, the scattered light of the particle (7) contains particle motion information. The scattered light of the particle (7) is collected by the imaging system and the position detection system on the side. Vector sound wave measurement is achieved by analyzing the oscillation direction, oscillation frequency and oscillation speed of the particle (7). The scattered light collected by the scattered light analysis module after the particle (7) propagates through the hollow waveguide (6) is divided into two beams. One beam of scattered light is connected to the imaging system and the other beam of scattered light is connected to the Doppler analysis system. When the particle (7) is disturbed by the sound wave, the distributed vector sound wave measurement is realized by analyzing the axial and radial motion of the particle (7) in the hollow waveguide (6). Specifically, the laser (1) emits laser light as a light source, which is split into two beams of manipulation light by the half-wave plate (2) and the polarizing beam splitter (3). After the two beams of manipulation light are collimated by the mirror (4), the laser light is coupled into the fiber core from both ends of the hollow waveguide (6) by the coupling lens (5). The particle (7) is captured by the two beams of light and suspended in the hollow waveguide (6). By adjusting the power ratio of the two beams of manipulation light, the axial speed and direction of the particle (7) are controlled, and the particle (7) is placed at different axial positions of the hollow waveguide (6) to monitor the sound waves at different spatial positions. The radial intrinsic vibration frequency and amplitude of the particle (7) are controlled by controlling the total laser power. The scattered light from the particle (7) is received by the objective lens (8) on the side and then split into two beams by the beam splitter (9). One beam is collected by the camera (10), and the other beam is focused into the four-quadrant position detector (12) by the focusing lens (11). By analyzing the vibration frequency and amplitude of the particle (7) in the axial and radial directions of the optical fiber monitored by the four-quadrant position detector (12), the direction, frequency and intensity of the sound wave can be detected. The output light spot of the hollow waveguide (6) is collected by the coupling lens (5) and reflected by the second beam splitter (13) into the third beam splitter (14). The scattered light is split into two beams by the third beam splitter (14). One beam is collected by the second camera (15), and the other beam is focused into the photodetector (17) by the second focusing lens (16). By analyzing the changes in the shape of the scattered light spot output by the hollow waveguide monitored by the second camera (15), the changes in the radial position of the particles along the hollow waveguide can be detected. By analyzing the scattered light of the particle (7) monitored by the photodetector (17), the position of the particle along the axial and radial directions of the hollow waveguide can be detected.

2. The distributed vector acoustic wave sensor according to claim 1, characterized in that: The particulate (7) material comprises at least one of dielectric material, crystal material, semiconductor material, metallic material, and biological material; The hollow waveguide (6) is one of hollow photonic bandgap fiber, capillary fiber, hollow anti-resonant fiber or porous fiber. The objective lens (8) has a magnification of 10× to 100×.

3. A distributed vector acoustic wave sensor according to claim 1, characterized in that: The bandwidth of the four-quadrant position detector (12) is not less than 10 kHz.

4. A distributed vector acoustic wave sensor according to claim 1, characterized in that: The sampling rate of the four-quadrant position detector (12) is more than twice the vibration frequency of the particle (7).

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