Distributed vector sonic sensor

Abstract

The invention belongs to the technical field of acoustic wave optical fiber sensing, and particularly relates to a distributed vector acoustic wave sensor, which comprises a hollow-core waveguide in which at least one particle is suspended; a laser; the incident light beam splitting module is used for splitting the laser into two beams of control light, the two beams of control light are incident from the two ends of the hollow-core waveguide respectively, and the two beams of control light act on the two sides of the particles respectively so as to adjust the positions of the particles in the axis direction of the hollow-core waveguide; the scattered light splitting module splits the scattered light into two light beams, a light path of one light beam is connected with a first imaging system, and a light path of the other light beam is connected with a position detection system; the scattered light analysis module is used for splitting the scattered light into two light beams, one light beam is connected with a second imaging system, and the other light beam is connected with a Doppler analysis system through a light path. The vector acoustic wave measurement function can be realized by analyzing motion information such as particle oscillation direction, oscillation frequency and oscillation speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensing, and particularly relates to a distributed vector acoustic wave sensor. Background Art

[0002] As an important branch in the field of sensing, the continuous improvement of the hollow-core fiber sensor in terms of structure and function is an inevitable trend. The hollow-core fiber optical particle sensor is a newly emerging distributed sensing platform in recent years, and it has developed rapidly in the field of distributed acoustic wave measurement. Since multi-component acoustic wave measurement can more truly reflect the sound field distribution in space, the measurement methods and technologies for realizing vector acoustic waves using the hollow-core fiber optical particle sensor still need to be explored.

[0003] The existing fiber optic distributed acoustic wave sensing technology introduces a change in optical path difference by changing the local refractive index based on the photoelastic effect of solid-core fibers, and only responds to the acoustic wave component incident along the fiber axis. This makes the traditional fiber optic distributed sensing technology defective in multi-component measurement, thus limiting its application in fields such as oil and gas resource exploration and seismic wave detection. The proposed sensing fiber laying scheme of spiral fiber winding by researchers can solve the vector measurement problem, but this scheme has a high cable laying complexity and requires precise winding angles. The L-shaped cable laying method can achieve the spatial inverse solution of multi-component acoustic waves in the field of fiber optic distributed sensing, but the number of cables to be laid is relatively large.

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

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

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

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

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

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

[0010] An incident light beam splitting module, the incident end of the incident light beam splitting module is optically connected to the output end of the laser, and the incident light beam splitting module is used to split the laser light into two manipulation light beams and respectively incident from both ends of the hollow waveguide, and the two manipulation light beams respectively act on both sides of the particle to adjust the position of the particle in the axial direction of the hollow waveguide;

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

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

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

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

[0015] A polarization beam splitter, the incident end of which is optically connected to the output end of the half-wave plate. The polarization beam splitter is used to split the incident light into a manipulation optical path one and a manipulation optical path two;

[0016] The manipulation optical path one is reflected by a plurality of mirrors and then enters one end of the hollow waveguide through a coupling lens;

[0017] The manipulation optical path two is reflected by a plurality of the other mirrors and then enters the other end of the hollow waveguide through the other coupling lens;

[0018] The manipulation optical path one and the manipulation optical path two are coaxially arranged.

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

[0020] An objective lens, the incident end of which is optically connected to the optical path of the scattered light of the particle;

[0021] A beam splitter one, the incident end of which is optically connected to the output end of the objective lens. The beam splitter one is used to split the scattered light into a scattered optical path one and a scattered optical path two. The scattered optical path one is optically connected to the imaging system, and the scattered optical path two is optically connected to the position detection system.

[0022] Optionally, the position detection system includes:

[0023] A focusing lens one, the incident end of which is optically connected to the scattered optical path two;

[0024] A quadrant position detector, the incident end of which is optically connected to the output end of the focusing lens one.

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

[0026] The beam splitter two is arranged between any one group of the reflectors and the coupling lens. The manipulation optical path one or the manipulation optical path two passes through the corresponding beam splitter two and is incident on the end of the hollow waveguide. The scattered light of the particle is incident on the reflecting surface of the beam splitter two through the coupling lens to form a scattered optical path three;

[0027] The beam splitter three has an incident end optically connected to the optical path of the scattered optical path three. The beam splitter three is used to split the scattered optical path three into a scattered optical path four and a scattered optical path five. The scattered optical path four is optically connected to the Doppler analysis system, and the scattered optical path five is optically connected to the imaging system two.

[0028] Optionally, the Doppler analysis system includes:

[0029] The focusing lens two has an incident end optically connected to the optical path of the scattered optical path four;

[0030] The photodetector has an incident end optically connected to the output end of the focusing lens two.

[0031] Optionally, the imaging system one includes a camera one, and the shooting end of the camera one is optically connected to the optical path of the scattered optical path one;

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

[0033] Optionally, the particle material at least includes one of dielectric material, crystal material, semiconductor material, metal material, and biological material;

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

[0035] The magnification of the objective lens is one of 10× to 100×.

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

[0037] Optionally, the sampling rate of the 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, in the present invention, at least one particle is arranged in a hollow waveguide. After a laser emits laser light, the incident light beam splitting module splits the laser light into two manipulation light beams, which are respectively irradiated on both ends of the hollow waveguide. The two manipulation light beams act on both sides of the particle to adjust the position of the particle in the axial direction of the hollow waveguide, and the scattered light beam splitting module collects the scattered light on the surface of the particle. One path of the scattered light is connected to an imaging system, and the other beam of scattered light is connected to a position detection system. When the particle is disturbed by sound waves, the scattered light of the particle contains particle motion information. The scattered light of the particle can be collected by the imaging system and the position detection system on the side, and the vector acoustic wave measurement function can be realized by analyzing the motion information such as the oscillation direction, oscillation frequency, and oscillation speed of the particle. Brief Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings:

[0041] Figure 1 Structural schematic diagram of the present invention;

[0042] Figure 2 Schematic diagram of the forced vibration of the particle of the present invention in the hollow waveguide;

[0043] Figure 3 Schematic diagram of the particle vector measurement and distributed measurement of the present invention;

[0044] Figure 4 End face structure diagram of different types of hollow waveguides of the present invention;

[0045] Among them, 1. Laser; 2. Half-wave plate; 3. Polarizing beam splitter; 4. Mirror; 5. Coupling lens; 6. Hollow waveguide; 7. Particle; 8. Objective lens; 9. Beam splitter 1; 10. Camera 1; 11. Focusing lens 1; 12. Quadrant position detector; 13. Beam splitter 2; 14. Beam splitter 3; 15. Camera 2; 16. Focusing lens 2; 17. Photoelectric detector. Detailed Embodiments

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0047] To make the above 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] Referring to Figures 1 to 4 , the present invention discloses a distributed vector acoustic wave sensor, including:

[0049] A hollow waveguide 6, in which at least one particle 7 is suspended;

[0050] A laser 1 for emitting laser light;

[0051] An incident light beam splitting module, the incident end of which is optically connected to the output end of the laser 1. The incident light beam splitting module is used to split the laser light into two manipulation light beams and respectively incident from both ends of the hollow waveguide 6. The two manipulation light beams 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] A scattered light beam splitting module, the incident end of which is optically connected to the scattered light path on the surface of the particle 7. The scattered light beam splitting module splits the scattered light into two light beams, one of which is optically connected to an imaging system one, and the other light beam is optically connected to a position detection system;

[0053] A scattered light analysis module, the incident end of which is optically connected 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 light beams, one of which is connected to an imaging system two, and the other light beam is optically connected to a Doppler analysis system.

[0054] In use, in the present invention, at least one particle 7 is arranged in the hollow waveguide 6. After the laser 1 emits laser light, the incident light beam splitting module splits the laser light into two manipulation light beams and respectively irradiates both ends of the hollow waveguide 6. The two manipulation light beams 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, and the scattered light beam splitting module collects the scattered light on the surface of the particle 7. One path of the scattered light is connected to the imaging system one, and the other scattered light beam is connected to the position detection system. When the particle 7 is disturbed by acoustic waves, the scattered light of the particle 7 contains particle motion information. The scattered light of the particle 7 can be collected by the imaging system and the position detection system on the side. By analyzing the motion information such as the oscillation direction, oscillation frequency, and oscillation speed of the particle 7, the vector acoustic wave measurement function can be realized. The scattered light analysis module collects the scattered light after the particle passes through the hollow waveguide 6. The scattered light is divided into two beams, one of which is connected to the imaging system two, and the other scattered light beam is connected to the Doppler analysis system. When the particle 7 is disturbed by acoustic waves, the axial and radial motion information of the particle 7 in the hollow waveguide can be analyzed, thereby realizing the distributed vector acoustic wave measurement function.

[0055] As an optional embodiment, the incident light beam splitting module includes:

[0056] A half-wave plate 2, with its incident end optically connected to the light path of the output end of the laser 1;

[0057] The incident end of a polarization beam splitter 3 is optically connected to the output end of the half-wave plate 2. The polarization beam splitter 3 is used to split the incident light into a manipulation optical path 1 and a manipulation optical path 2;

[0058] The manipulation optical path 1 is reflected by a plurality of mirrors 4 and then enters one end of a hollow waveguide 6 through a coupling lens 5;

[0059] The manipulation optical path 2 is reflected by a plurality of other mirrors 4 and then enters the other end of the hollow waveguide 6 through another coupling lens 5;

[0060] The manipulation optical path 1 and the manipulation optical path 2 are coaxially arranged.

[0061] As an optional implementation manner, the scattered light splitting module includes:

[0062] An objective lens 8, with its incident end optically connected to the light path of the scattered light of the particle 7;

[0063] A beam splitter 9, with its incident end optically connected to the output end of the objective lens 8. The beam splitter 9 is used to split the scattered light into a scattered light path 1 and a scattered light path 2. The scattered light path 1 is optically connected to the imaging system, and the scattered light path 2 is optically connected to the position detection system.

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

[0065] A focusing lens 11, with its incident end optically connected to the scattered light path 2;

[0066] A quadrant position detector 12, with its incident end optically connected to the output end of the focusing lens 11.

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

[0068] A beam splitter 13 is arranged between any group of mirrors 4 and the coupling lens 5. The manipulation optical path 1 or the manipulation optical path 2 passes through the corresponding beam splitter 13 and enters the end of the hollow waveguide 6. The scattered light of the particle 7 enters the reflecting surface of the beam splitter 13 through the coupling lens 5 to form a scattered light path 3;

[0069] A beam splitter 14, with its incident end optically connected to the scattered light path 3. The beam splitter 14 is used to split the scattered light path 3 into a scattered light path 4 and a scattered light path 5. The scattered light path 4 is optically connected to the Doppler analysis system, and the scattered light path 5 is optically connected to the imaging system 2.

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

[0071] The second focusing lens 16, the incident end of the second focusing lens 16 is optically connected to the fourth scattering optical path;

[0072] The photodetector 17, the incident end of the photodetector 17 is optically connected to the exit end of the second focusing lens 16.

[0073] As an alternative embodiment, the first imaging system includes a first camera 10, the shooting end of the first camera 10 is optically connected to the first scattering optical path;

[0074] The second imaging system includes a second camera 15, the shooting end of the second camera 15 is optically connected to the fifth scattering optical path.

[0075] As an alternative embodiment, the material of the particle 7 at least includes one of a dielectric material, a crystal material, a semiconductor material, a metal material, and a biological material;

[0076] The hollow waveguide 6 is one of a hollow photonic bandgap fiber, a capillary fiber, a hollow anti-resonant fiber, or a porous fiber;

[0077] The magnification of the objective lens 8 is one of 10× to 100×.

[0078] As an alternative embodiment, the bandwidth of the quadrant position detector 12 is not less than 10 kHz.

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

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

[0081] The laser 1 serves as the manipulation light source. The laser passes through the half-wave plate 2 and the polarization beam splitter 3 and is divided into two beams of light with adjustable relative power. The two beams of light pass through the coupling lens 5 and enter the hollow waveguide 6 to become the manipulation light that can manipulate the particle 7. When the particle 7 is disturbed by sound waves, the scattered light of the particle 7 contains the particle motion information. The scattered light of the particle 7 can be collected by the first imaging system and the position detection system on the side. After the scattered light of the particle 7 propagates through the hollow waveguide, it can be collected by the second imaging system and the Doppler analysis system.

[0082] The first imaging system includes the objective lens 8, the first beam splitter 9, and the first camera 10, and can intuitively and real-time reflect information such as the movement direction of the particle 7.

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

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

[0085] The distributed vector acoustic fiber sensor adjusts the position, oscillation frequency, motion direction and speed of the particle 7 by modulating the optical power of two manipulation lights, so as to realize the distributed function; the vector acoustic wave measurement function is realized through the motion information such as the oscillation direction, oscillation frequency and oscillation speed of the particle 7 detected by the quadrant position detector 12. Based on the scattered light analysis module, using the Doppler velocity measurement method, the instantaneous velocity of the particle 7 can be analyzed from the beat frequency signal, and the position information of the particle can be obtained by further integrating along time. Combining with the vector acoustic wave detection technology, the distributed vector acoustic wave detection function can be realized.

[0086] The principle of detecting vector acoustic waves by using the vibration of microparticles will be elaborated in detail below.

[0087] The motion state of the particle 7 is affected by the acoustic wave. The acoustic pressure F generated by the acoustic wave on the particle 7 A , the optical gradient force F provided by the laser in the core of the hollow waveguide 6, the gravity G of the microparticle and the air resistance f are balanced, so that the suspended particle 7 has an intrinsic vibration angular frequency ω0 of the microparticle. When a periodic acoustic pressure is applied to the particle 7 by the acoustic wave, the particle 7 will be forced to vibrate. The damped forced vibration makes the particle perform simple harmonic vibration under the action of a continuous periodic external force. The particle 7 will be in a vibration stable state:

[0088]

[0089] where X0 is the amplitude in the stable state, ω is the angular frequency of the external force, t is the time, is the vibration phase.

[0090] 1. When the frequency of the periodic acoustic 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 acoustic pressure tends to infinity and can be equivalent to a constant force. The amplitude of the particle in this region is the displacement X of the particle from the center of the optical trap.

[0091] 2. When the frequency of the periodic acoustic pressure is much larger 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 acoustic pressure. As the acoustic wave frequency increases, the amplitude X0 of the particle decreases and gradually approaches 0.

[0092] 3. When the acoustic wave frequency approaches the eigen-vibration angular frequency ω0, this frequency region is called the resonance region. In the low-frequency and high-frequency regions, the damping has a weak influence on the particle amplitude, but the damping of the medium around the particle in the resonance region has a significant inhibitory effect on the particle amplitude. When the particle is in the small-damping case (damping ratio n is the damping parameter variable), the particle amplitude X0 will increase significantly; when the particle is in the critical-damping and large-damping cases (damping ratio ε≥1), the particle amplitude X0 will not increase.

[0093] The movement direction of particle 7 is related to the sound pressure direction. By monitoring the amplitudes of particle 7 in the axial and radial directions of the hollow waveguide 6, the direction of the acoustic wave can be calculated, so as to achieve the purpose of vector measurement.

[0094] The above shows that the movement state of particle 7 will be affected by the direction, frequency, magnitude of the acoustic wave and the damping of the environment around the particle. Therefore, this system can be used to detect the direction of the acoustic wave, acoustic wave frequency, sound intensity, environmental damping, air pressure. When particle 7 is in the small-damping case, by adjusting the mass of particle 7 and the trapping light intensity, the frequency response characteristics of the sensor can be dynamically adjusted, and the resonance region will increase the particle amplitude and improve the system sensitivity.

[0095] There is a wide selection range for the particle size and material of particle 7, which can be selected as dielectric materials, metal materials, semiconductor materials, biological materials, etc. This can broaden the application range of this sensor, and make the system have functions such as electromagnetic sensing according to 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 makes the sensor have the function of distributed sensing. When multiple particles 7 are suspended in the core of the hollow waveguide, each particle can be regarded as a multi-component sensing oscillator, and some positioning functions of the quantity to be measured can be realized.

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

[0097] Based on the laser Doppler velocimetry, the axial instantaneous velocity of the particle can be measured, and then by integrating the particle instantaneous velocity over time, the position information of the suspended particle can be obtained. 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. Since there is a Doppler frequency shift of the backward scattered light of the particle relative to the incident light during the movement process, 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 the particle is transmitting in the optical fiber, based on the Doppler effect, the particle far from the light source makes the light frequency L undergo a redshift compared with the light source frequency υ; then, the particle far from the fixed photodetector (PD) makes the light frequency further undergo redshift. Therefore, for the velocity of non-relativistic particles, the frequency of the reflected light of the particles is Then the frequency difference between the light emitted by the particles and the incident light is:

[0099]

[0100] where v p is the moving velocity of the suspended particles, and Δυ D represents the frequency difference between the reflected light of the moving particles and the reflected light of the fiber end face. Therefore, the beat frequency between the reflected light of the particles detected by the PD and the reflected light of the fiber end face can be used to inversely calculate the velocity information of the moving particles at high speed. Further integrating the velocity of the moving particles over time can obtain the position information of the particles. At the same time, the change in the light intensity monitored by the PD can be used to calculate the change in the radial position of the particles in the hollow waveguide through calculation. Combining the above position detection technology with the vector acoustic wave detection technology in the device can realize the distributed sensing function of the sensor.

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

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

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

[0104] In the embodiment of the present invention, the laser 1 emits laser light as a light source, which is divided into two beams of manipulation light by the half-wave plate 2 and the polarization beam splitter 3. After being collimated by the mirrors 4, the two beams of light respectively couple the laser light into the fiber core from both ends of the hollow waveguide 6 by using the coupling lenses 5. The particles 7 are trapped by the two beams of light and suspended in the hollow waveguide 6.

[0105] By adjusting the power ratio of the two beams of light, the axial movement speed and direction of the particles 7 can be controlled. Placing the particles 7 at different axial positions in the hollow waveguide 6 can monitor the acoustic waves at different spatial positions.

[0106] By controlling the total laser power, the radial eigen-vibration frequency and amplitude of the particles 7 can be controlled.

[0107] The scattered light of the particles 7 is received by the high-power objective lens 8 on the side and then divided into two beams of scattered light by the beam splitter 1 9. One beam of scattered light is collected by the camera 1 10, and the other beam of scattered light is focused by the focusing lens 1 11 into the quadrant position detector 12.

[0108] By analyzing the vibration frequency and amplitude of the particles 7 in the fiber axial and radial directions monitored by the quadrant position detector 12, the direction, frequency and intensity of the acoustic waves can be detected.

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

[0110] By analyzing the change in the shape of the scattered light spot output from the hollow waveguide monitored by the second camera 15, the change in the radial position of the particle along the hollow waveguide can be detected.

[0111] By analyzing the scattered light of the particle 7 monitored by the photodetector 17, the axial and radial positions of the particle along 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: Use the polarization beam splitter 3 to split the laser emitted by the laser 1, and after adjusting the two manipulation beams into two coaxial beams facing each other through several reflectors 4, select a coupling lens 5 with an appropriate focal length for the fundamental mode coupling of the hollow waveguide 6;

[0114] Step 2, Particle axial position control: Use the half-wave plate 2 and the polarization beam splitter 3 to adjust the relative light intensity of the two beams of light, and rotate the half-wave plate 2 to make the particle 7 move along the fiber axis;

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

[0116] Step 4, Construction of a signal acquisition system for the axial and radial motion positions of the particle: The scattered light of the particle 7 passing through the other path of scattered light split by the first beam splitter 9 is focused into the quadrant position detector 12, and the axial and radial motion signals of the particle 7 are collected.

[0117] Step 5, Construction of a scattered light analysis module: The scattered light and the unscattered light of the particle in the hollow waveguide are collected by the coupling lens 5 and reflected by the second beam splitter 13 into the third beam splitter 14 and split into two beams of scattered light. One path of scattered light is collected by the second camera 15, and the other path of scattered light is focused by the second focusing lens 16 into the photodetector 17. The change signal of the output light of the hollow waveguide caused by the particle 7 is collected, and the vibration information of the particle is further analyzed. Further, the transmission and reflection ratios of the polarization beam splitter 3, the first beam splitter 9, and the second beam splitter 13 are one of 50:50, 70:30, or 90:10.

[0118] Further, the type of the hollow waveguide 6 is one of a hollow photonic bandgap fiber, a capillary fiber, a hollow anti-resonant fiber, or a porous fiber, Figure 4The cross-sectional microscope patterns of capillary optical fibers, hollow-core photonic bandgap fibers, and hollow-core anti-resonant fibers are given; the shape and aperture of the air core of the hollow waveguide 6 are not limited.

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

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

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

[0122] To facilitate the understanding of the present invention, the present invention will be further elaborated below in conjunction with specific embodiments. The presentation form of the present invention is not limited to the following embodiments.

[0123] Step 1, beam collimation and beam coupling: Remove the coating layer of the hollow waveguide 6 with a cladding diameter of 285 μm and a core diameter of 30 μm and cut the fiber end face flat. The hollow waveguide 6 is a hollow-core anti-resonant fiber. Align two opposite beams and the fiber coaxially, and use a coupling lens to couple the beam into the fiber as the fundamental mode;

[0124] Step 2, suspension of the particle 7 and adjustment of the axial position: Sprinkle an appropriate amount of the particle 7 on the end face of the hollow waveguide 6, and the particle 7 is pushed into the fiber core of the hollow waveguide 6 by optical force. Rotate the half-wave plate 2 to adjust the light intensity at both ends of the beam so that the particle 7 is suspended in the fiber core of the hollow waveguide 6 and the axial position of the particle can be adjusted;

[0125] Step 3, adjustment of the particle 7 motion state information acquisition system: When the particle 7 is suspended at a specific position, apply sound waves to the particle 7. The direction and amplitude of the sound waves will affect the vibration direction and amplitude of the particle 7. Collect the scattered light of the particle 7 from the side of the fiber. The scattered light enters the camera 10 through the objective lens 8 and the first beam splitter 9, so as to realize the real-time monitoring of the motion direction and speed of the particle. Another beam of scattered light is collected by the quadrant position detector 12 after being reflected by the first beam splitter 9 and focused by the first focusing lens 11. The quadrant position detector 12 can output an electrical signal containing the position of the particle 7 and the signal of the scattered light intensity of the particle 7. By analyzing the amplitude ratio of the particle 7 in the axial and radial motions, the motion direction of the particle 7 can be judged and the direction of the sound wave can be inferred. The output signal of the quadrant position detector 12 also contains the amplitude size and vibration speed of the particle 7, and information such as the direction, amplitude, and frequency of the sound wave can be analyzed.

[0126] Step 4. Adjustment of the system for obtaining the axial movement position of the particle 7 in the hollow waveguide: After the 1064 nm laser is coupled into the core, the suspended particles far from the light source will generate Doppler frequency-shifted light. The beat signal generated by the frequency-shifted light and the non-frequency-shifted light is received by the photodetector. The movement speed of the particle is resolved from this signal, and the integral of this movement speed with respect to time gives the particle position, thus realizing distributed sensing.

[0127] The beneficial effects of the solution conceived in the present invention compared with the existing distributed acoustic fiber sensing technology are as follows:

[0128] 1. Since the sensitive element of this sensor is the suspended microparticles, compared with the existing distributed acoustic fiber sensors, the sensing parameters and performance indicators of this sensor can break through the limitations of the quartz fiber itself.

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

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

[0131] 4. Compared with the existing fiber sensors, this sensor can be more flexible by changing the suspended particles according to the quantity to be measured.

[0132] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0133] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A distributed vector acoustic wave sensor, characterized in that, Comprising: A hollow waveguide (6) in which at least one particle (7) is suspended; A laser (1) for emitting laser light; An incident light beam splitting module, the incident end of which is optically connected to the output end of the laser (1), and the incident light beam splitting module is used to split the laser light into two manipulation light beams and respectively enter from both ends of the hollow waveguide (6), and the two manipulation light beams respectively 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); A scattered light beam splitting module, the incident end of which is optically connected to the scattered light path on the surface of the particle (7), and the scattered light beam splitting module splits the scattered light into two light beams, one of which is optically connected to an imaging system one, and the other light beam is optically connected to a position detection system; A scattered light analysis module, the incident end of which is optically connected to the scattered light path on the surface of the particle (7), and the scattered light analysis module is used to split the scattered light into two light beams, one of which is connected to an imaging system two, and the other light beam is optically connected to a Doppler analysis system.

2. The distributed vector acoustic wave sensor according to claim 1, wherein The incident light beam splitting module includes: A half-wave plate (2), the incident end of which is optically connected to the output end of the laser (1); A polarization beam splitter (3), the incident end of which is optically connected to the output end of the half-wave plate (2), and the polarization 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 one is reflected by a plurality of reflectors (4) and then enters one end of the hollow waveguide (6) through a coupling lens (5); The manipulation optical path two is reflected by a plurality of the other reflectors (4) and then enters the other end of the hollow waveguide (6) through the other coupling lens (5); The manipulation optical path one and the manipulation optical path two are coaxially arranged.

3. The distributed vector acoustic wave sensor according to claim 2, characterized in that, The scattered light beam splitting module includes: An objective lens (8), the incident end of which is optically connected to the scattered light path of the particle (7); A beam splitter one (9), the incident end of which is optically connected to the output end of the objective lens (8), and the beam splitter one (9) is used to split the scattered light into a scattered optical path one and a scattered optical path two, the scattered optical path one is optically connected to the imaging system, and the scattered optical path two is optically connected to the position detection system.

4. The distributed vector acoustic wave sensor according to claim 3, wherein The position detection system includes: A focusing lens one (11), the incident end of which is optically connected to the scattered optical path two; A quadrant position detector (12), the incident end of which is optically connected to the output end of the focusing lens one (11).

5. A distributed vector acoustic wave sensor according to claim 4, characterized in that, The scattered light analysis module includes: A beam splitter two (13) is arranged between any one group of the reflectors (4) and the coupling lens (5), and the manipulation optical path one or the manipulation optical path two passes through the corresponding beam splitter two (13) and enters the end of the hollow waveguide (6), and the scattered light of the particle (7) enters the reflecting surface of the beam splitter two (13) through the coupling lens (5) to form a scattered optical path three; Beam splitter three (14), the incident end of which is optically connected to the third scattering optical path. The beam splitter three (14) is used to split the third scattering optical path into a fourth scattering optical path and a fifth scattering optical path. The fourth scattering optical path is optically connected to the Doppler analysis system, and the fifth scattering optical path is optically connected to the second imaging system.

6. A distributed vector acoustic wave sensor according to claim 5, characterized in that, The Doppler analysis system includes: Focusing lens two (16), the incident end of the focusing lens two (16) is optically connected to the fourth scattering optical path; Photoelectric detector (17), the incident end of the photoelectric detector (17) is optically connected to the output end of the focusing lens two (16).

7. The distributed vector acoustic wave sensor according to claim 6, characterized in that: The first imaging system includes camera one (10), and the shooting end of the camera one (10) is optically connected to the first scattering optical path; The second imaging system includes camera two (15), and the shooting end of the camera two (15) is optically connected to the fifth scattering optical path.

8. A distributed vector acoustic wave sensor according to claim 3, characterized in that: The material of the particle (7) includes at least one of dielectric material, crystal material, semiconductor material, metal 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 magnification of the objective lens (8) is one of 10× to 100×.

9. A distributed vector acoustic wave sensor according to claim 4, characterized in that: The bandwidth of the quadrant position detector (12) is not less than 10 kHz.

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

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