Distributed fiber bragg grating sound source positioning method and system based on weak measurement technology

Abstract

The invention provides a distributed fiber bragg grating sound source localization method and system based on a weak measurement technology. The method comprises the steps that S1, a distributed fiber bragg grating sensing platform based on the weak measurement technology is built; s2, the weak reflection array is placed in a sound field, the optical path of a weak reflection element is influenced by a sound source signal, so that the phase is changed, and light is received through a photoelectric detector; s3, Fourier transform is carried out on the difference value of the signals of the first photoelectric detector and the second photoelectric detector, and the phase corresponding to each weak reflection element is calculated; s4, obtaining the distance between the weak reflection primitive and the sound source according to the corresponding relation between the weak reflection primitive phase and the sound pressure; and S5, positioning the sound source according to the distance between the weak reflection element and the sound source. According to the invention, the weak reflection element with low reflectivity is selected, the transmission loss is reduced, multi-measurement-point measurement can be simply and conveniently used under the condition that the output optical power does not need to be improved, the noise and the high-power loss are reduced, and the positioning precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber Bragg gratings, and in particular to a distributed fiber Bragg grating sound source localization method and system based on weak measurement technology. Background Art

[0002] The sound source localization technology based on microphone array has the advantages of flexible beam control, high spatial resolution, and strong anti-interference ability, but the sensor array is usually composed of traditional capacitive and dynamic microphones, which are difficult to apply in harsh environments such as strong electromagnetic interference. Fiber Bragg grating has outstanding advantages in sound source localization in some specific environments, but the cost of the sensor is high, the optical path structure is complex, and the advantage of the large capacity of the fiber optic sensor system is not brought into play, making it difficult to build a large-scale sensor array. Most of the fiber optic sensor positioning methods currently used require more measurement point data to achieve higher-precision sound positioning, increase the number of gratings, and therefore need to use erbium-doped fiber amplifiers, which will cause noise and high power loss. Based on the above reasons, consider how to achieve higher-precision sound positioning without optical power amplification.

[0003] Patent document CN113176536A discloses a step-by-step focusing algorithm for quickly and accurately locating noise sources. The first step is to use M sound pressure sensors to form a measurement array W on the measurement surface, and measure the sound pressure data of each point of the measurement array W through the sound pressure sensor; the second step is to focus for the first time, divide the focusing surface into a regular grid, where each unit of the grid is a square, the intersection of the grid is the focal point of the sound source, and the distance between adjacent intersections of the grid is defined as d, that is, the interval between two adjacent focal points is d, and the focusing algorithm is used to find the large range of the area where the sound source position is located; the third step is to focus for the second time, and the large range of the area where the sound source position is located found in the second step is accurately divided, and the focusing algorithm in the previous step is repeated to perform a second accurate positioning to find the exact position of the sound source. However, the technical means used in this patent are different from those of the present invention, and this patent cannot completely solve the above-mentioned technical problems. Summary of the invention

[0004] In view of the defects in the prior art, the object of the present invention is to provide a distributed fiber Bragg grating sound source localization method and system based on weak measurement technology.

[0005] The distributed fiber Bragg grating sound source localization method based on weak measurement technology provided by the present invention comprises:

[0006] Step S1: Building a distributed fiber Bragg grating sensing platform based on weak measurement technology;

[0007] Step S2: placing the weak reflection array in the sound field, the weak reflection element is affected by the sound source signal, the optical path changes, and the phase changes, and the light is received by the photoelectric detector;

[0008] Step S3: Perform Fourier transform on the difference between the signals of the photodetector 1 and the photodetector 2 to calculate the phase corresponding to each weak reflection primitive;

[0009] Step S4: according to the corresponding relationship between the phase of the weak reflection primitive and the sound pressure, the distance between the weak reflection primitive and the sound source is obtained;

[0010] Step S5: Locate the sound source based on the distance between the weak reflection element and the sound source.

[0011] Preferably, the distributed fiber grating sensing platform comprises: a light source, a pre-selection process, a fiber polarization beam splitter, an acousto-optic modulator, a delay fiber, a fiber 2×1 beam splitter, a weak reflection array, a fiber coupler, a beam splitter, a post-selection process 1, a photodetector 1, a post-selection process 2, a photodetector 2 and a computer;

[0012] The light emitted by the light source is modulated into a preset pre-selection state in the pre-selection process; after passing through the optical fiber polarization beam splitter, in the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) through the acousto-optic modulator and the delay optical fiber, and then reaches the weak reflection array through the optical fiber 2×1 beam splitter; after the optical fiber coupler, the light in the optical fiber is converted into spatial light, and enters the post-selection process through the beam splitter, wherein the angles between the post-selection process 1 and the post-selection process 2 and the pre-selection are opposite to each other; the two light intensities are respectively received by the photodetector 1 and the photodetector 2, and the computer performs data processing to determine the position of the sound source.

[0013] Preferably, step S2 comprises the following steps:

[0014] Step S2.1: modulate the light output by the light source into a pre-selected state |i> through a pre-selection process, where |H> light is light that vibrates horizontally, and |V> light is light that vibrates vertically;

[0015] Step S2.2: The weak reflection array is composed of Bragg gratings. The optical path of the weak reflection element changes under the influence of the sound source signal and is encoded into a time-varying phase φ(t) through the acousto-optic modulator and the delay fiber. It is expressed as: Among them, i is the imaginary unit, e is the natural constant, is the observable quantity of the system, After the interaction, the state of the output light is

[0016] The light from the light source is pre-selected and divided into |H> light and |V> light. The |H> light passes through the AOM and the delay fiber and is reflected by the weak reflection element in turn to reach the fiber coupler; the |V> light is first reflected by the weak reflection element in turn, then passes through the delay fiber and AOM to reach the fiber coupler; the AOM is set to Ω AOM Angular frequency modulation, when |H> light passes, Ω AOM =Ω0+kt, when |V> light passes, Ω AOM =0; the optical paths of |H> light and |V> light are the same, so they arrive at the fiber coupler at the same time;

[0017] In a weak reflection array, the phase delay of the light reflected by the i-th reflector |H> is expressed as The phase of light traveling along the same path in opposite directions is expressed as The phase difference between the two beams is Where L a is the optical path of the delay fiber, L i is the optical path from the fiber 2×1 beam splitter to the i-th weak reflection element, ν is the speed of light in the fiber, ω c is the central angular frequency of the light source. Due to the effect of the delayed optical fiber, the light |V> reaches the weak reflection element first, and the light |H> reaches the weak reflection element later. The time difference is τ=L a / ν, in the time difference τ between |V> light and |H> light reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL,|H>The light phase becomes The phase difference is That is, φ(t) introduced by the weak reflector array during the interaction process;

[0018] Step S2.3: After the light passes through the beam splitter, the post-selection state |f> is modulated to be within a preset orthogonal range with the pre-selection state, the post-selection angle of the post-selection process 1 is set to ε, and the post-selection angle of the post-selection process 2 is set to -ε, and the light intensity is projected onto the post-selection state. The post-selection process 1 is The second post-selection process is

[0019] The light intensity is used as the detection index for detection. The initial light intensity is I0(t), and the reflection coefficient of the i-th weak reflection element is r i , the light intensity reflected by the i-th weak reflection element received by the photodetector is The light intensity reflected by the i-th weak reflection element received by the photodetector 2 is In fact, the light intensity received by the photodetector is the sum of the light intensities reflected by all weak reflection elements. Therefore, the light intensity received by the photodetector is The light intensity received by photodetector 2 is

[0020] Preferably, the step S3 comprises:

[0021] The acoustic signal is demodulated according to the phase change of the weak reflection element, and the light intensity received by the photodetector 1 and the photodetector 2 is obtained. Through Fourier transform, the vibration information is demodulated from the phase change. Since the distance between each weak reflection element and the sound source is different, according to the sound source attenuation effect, the sound level received by each weak reflection element is also different. i is the attenuation coefficient from the sound source to the i-th weak reflection element, i = 1, 2, 3…, the sound source signal is x(t);

[0022] According to the photoelastic effect, during the time difference τ between the light |V> and the light |H> reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL, where ΔL=γL i-1,i α i [x(t-τ)-x(t)], where γ is the effective photoelastic coefficient, L i-1,i is the distance between the i-1th weak reflection primitive and the i-th weak reflection primitive; Get frequency Ignoring the size of 2ΔLkt / υ, It is deduced that the vibration ΔL is derived from the phase change Δθ i Extracted from C i There is no effect on vibration detection. Substituting ΔL into the equation gives right After fast Fourier transform, the frequency term f is obtained i , phase term θ i and reflectivity r i , through weak measurement technology, amplify the reflectivity r i ; Each weak reflection element has a different L i , so the frequency Corresponding to each weak reflection primitive, the signals from different weak reflection primitives are separated, and then the θ corresponding to each weak reflection primitive is obtained. i .

[0023] Preferably, the step S4 comprises: i Get the attenuation coefficient α corresponding to each weak reflection primitive iAccording to the corresponding relationship between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial positioning of the sound source is obtained through geometric calculation.

[0024] The distributed fiber Bragg grating sound source localization system based on weak measurement technology provided by the present invention comprises:

[0025] Module M1: Building a distributed fiber Bragg grating sensing platform based on weak measurement technology;

[0026] Module M2: Place the weak reflection array in the sound field. The weak reflection element is affected by the sound source signal and the optical path changes, thus changing the phase, and the light is received by the photoelectric detector.

[0027] Module M3: Perform Fourier transform on the difference between the signals of photodetector 1 and photodetector 2 to calculate the phase corresponding to each weak reflection primitive;

[0028] Module M4: According to the corresponding relationship between the phase of the weak reflection element and the sound pressure, the distance between the weak reflection element and the sound source is obtained;

[0029] Module M5: Locate the sound source based on the distance between the weak reflection element and the sound source.

[0030] Preferably, the distributed fiber grating sensing platform comprises: a light source, a pre-selection process, a fiber polarization beam splitter, an acousto-optic modulator, a delay fiber, a fiber 2×1 beam splitter, a weak reflection array, a fiber coupler, a beam splitter, a post-selection process 1, a photodetector 1, a post-selection process 2, a photodetector 2 and a computer;

[0031] The light emitted by the light source is modulated into a preset pre-selection state in the pre-selection process; after passing through the optical fiber polarization beam splitter, in the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) through the acousto-optic modulator and the delay optical fiber, and then reaches the weak reflection array through the optical fiber 2×1 beam splitter; after the optical fiber coupler, the light in the optical fiber is converted into spatial light, and enters the post-selection process through the beam splitter, wherein the angles between the post-selection process 1 and the post-selection process 2 and the pre-selection are opposite to each other; the two light intensities are respectively received by the photodetector 1 and the photodetector 2, and the computer performs data processing to determine the position of the sound source.

[0032] Preferably, the module M2 comprises:

[0033] Module M2.1: modulate the light output by the light source into the pre-selected state |i> through the pre-selection process, where |H> light is light that vibrates horizontally, and |V> light is light that vibrates vertically;

[0034] Module M2.2: The weak reflection array consists of Bragg gratings. The optical path of the weak reflection element changes under the influence of the sound source signal. After passing through the acou-optic modulator and the delay optical fiber, it is encoded into a time-varying phase φ(t) and interacts It is expressed as: where i is the imaginary unit and e is the natural constant, is the observable of the system, |V><V|. After the interaction, the state of the output light is

[0035] The light from the light source passes through pre-selection and is divided into |H> light and |V> light. The |H> light is reflected by the weak reflection elements in turn after passing through the AOM and the delay optical fiber and reaches the fiber coupler; the |V> light is first reflected by the weak reflection elements in turn and then passes through the delay optical fiber and the AOM and reaches the fiber coupler; the AOM is set to be modulated at an angular frequency of Ω AOM When the |H> light passes through, Ω AOM =Ω0 + kt, and when the |V> light passes through, Ω AOM =0; the optical paths of the |H> light and the |V> light are the same, so they reach the fiber coupler at the same time;

[0036] In the weak reflection array, the phase delay of the |H> light reflected by the i-th reflector is expressed as The phase of the |V> light propagating along the same path in the opposite direction is expressed as The phase difference between the two light beams is where L a is the optical path of the delay optical fiber, L i is the optical path from the fiber 2×1 beam splitter to the i-th weak reflection element, ν is the speed of light in the optical fiber, ω c is the central angular frequency of the light source. Due to the action of the delay optical fiber, the |V> light reaches the weak reflection element first and the |H> light reaches the weak reflection element later. The time difference is τ = L a / ν. During the time difference τ between the arrival of the |V> light and the |H> light at the i-th weak reflection element, the position of the i-th weak reflection element changes from L i to L i +ΔL, and the phase of the |H> light becomes The phase difference is which is φ(t) introduced by the weak reflector array during the interaction process;

[0037] After the light passes through the beam splitter, the post-selection state |f> is modulated to be within a preset orthogonal range with the pre-selection state. The post-selection angle of the first post-selection process is ε, and the post-selection angle of the second post-selection process is -ε. The light intensity is projected onto the post-selection state. The first post-selection process is The second post-selection process is

[0038] The light intensity is used as the detection index for detection. The initial light intensity is I0(t), and the reflection coefficient of the i-th weak reflection element is r i , the light intensity reflected by the i-th weak reflection element received by the photodetector is The light intensity reflected by the i-th weak reflection element received by the photodetector 2 is In fact, the light intensity received by the photodetector is the sum of the light intensities reflected by all weak reflection elements. Therefore, the light intensity received by the photodetector is The light intensity received by photodetector 2 is

[0039] Preferably, the module M3 comprises:

[0040] The acoustic signal is demodulated according to the phase change of the weak reflection element, and the light intensity received by the photodetector 1 and the photodetector 2 is obtained. Through Fourier transform, the vibration information is demodulated from the phase change. Since the distance between each weak reflection element and the sound source is different, according to the sound source attenuation effect, the sound level received by each weak reflection element is also different. i is the attenuation coefficient from the sound source to the i-th weak reflection element, i = 1, 2, 3…, the sound source signal is x(t);

[0041] According to the photoelastic effect, during the time difference τ between the light |V> and the light |H> reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL, where ΔL=γL i-1,i α i [x(t-τ)-x(t)], where γ is the effective photoelastic coefficient, L i-1,i is the distance between the i-1th weak reflection primitive and the i-th weak reflection primitive; Get frequency Ignoring the size of 2ΔLkt / υ, It is deduced that the vibration ΔL is derived from the phase change Δθ i Extracted from C i There is no effect on vibration detection. Substituting ΔL into the equation gives right After fast Fourier transform, the frequency term f is obtained i , phase term θ i and reflectivity r i, through weak measurement technology, amplify the reflectivity r i ; Each weak reflection element has a different L i , so the frequency Corresponding to each weak reflection primitive, the signals from different weak reflection primitives are separated, and then the θ corresponding to each weak reflection primitive is obtained. i .

[0042] Preferably, the module M4 comprises: i Get the attenuation coefficient α corresponding to each weak reflection primitive i According to the corresponding relationship between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial positioning of the sound source is obtained through geometric calculation.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The present invention uses weak reflection primitives with low reflectivity to reduce transmission loss. It can simply use multiple measurement points for measurement without increasing the output optical power, reduce noise and high power loss, and improve positioning accuracy.

[0045] 2. The present invention has a wide range of applications. By combining weak measurement technology with fiber grating sensors, it can resist electromagnetic interference and realize distributed long-distance sensing, and can overcome the defects of existing fiber optic sensing positioning technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0047] Figure 1 It is a schematic diagram of the principle of the present invention;

[0048] Reference numerals:

[0049] 1-light source; 2-pre-selection process; 3-fiber polarization beam splitter; 4-acoustic-optic modulator; 5-delay fiber; 6-fiber 2×1 beam splitter; 7-weak reflection array; 8-fiber coupler; 9-beam splitter; 10-post-selection process one; 11-photodetector one; 12-post-selection process two; 13-photodetector two; 14-computer. DETAILED DESCRIPTION

[0050] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0051] Example 1

[0052] The present invention provides a distributed fiber Bragg grating sound source localization method based on weak measurement technology, comprising:

[0053] Step S1: Building a distributed fiber Bragg grating sensing platform based on weak measurement technology;

[0054] Step S2: placing the weak reflection array in the sound field, the weak reflection element is affected by the sound source signal, the optical path changes, and the phase changes, and the light is received by the photoelectric detector;

[0055] Step S3: Perform Fourier transform on the difference between the signals of the photodetector 1 and the photodetector 2 to calculate the phase corresponding to each weak reflection primitive;

[0056] Step S4: according to the corresponding relationship between the phase of the weak reflection primitive and the sound pressure, the distance between the weak reflection primitive and the sound source is obtained;

[0057] Step S5: Locate the sound source based on the distance between the weak reflection element and the sound source.

[0058] Specifically, the distributed fiber grating sensing platform in step S1 includes: a light source 1, a pre-selection process 2 (composed of a half wave plate and a polarizer), a fiber polarization beam splitter (PBS) 3, an acousto-optic modulator (AOM) 4, a delay fiber 5, a fiber 2×1 beam splitter 6, a weak reflection array 7, a fiber coupler 8, a beam splitter 9, a post-selection process 1 (composed of a half wave plate, a polarizer, and a quarter wave plate) 10, a photodetector 1 11, a post-selection process 2 (composed of a half wave plate, a polarizer, and a quarter wave plate) 12, a photodetector 2 13, and a computer 1 4; the light emitted by the light source 1 is modulated into a preset pre-selected state in the pre-selected process 2; in the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) via the acousto-optic modulator 4 and the delay fiber 5, and the above process is transmitted in the optical fiber; through the optical fiber coupler 8, the light in the optical fiber is converted into spatial light, and enters the post-selected process through the beam splitter 9, wherein the angles between the post-selected process 1 10 and the post-selected process 2 12 and the pre-selected process are opposite to each other; the two light intensities are received by the photodetector 1 11 and the photodetector 2 13 respectively, and the computer 14 performs data processing to determine the position of the sound source.

[0059] Specifically, step S2 includes the following steps:

[0060] Step S2.1: modulate the light output by light source 1 into a pre-selection state |i> through pre-selection process 2, where |H> light is the light that vibrates horizontally, and |V> light is the light that vibrates vertically.

[0061] Step S2.2: The weak reflection array is composed of Bragg gratings. The optical path of the weak reflection element changes under the influence of the sound source signal and is encoded into a time-varying phase φ(t) by the acousto-optic modulator 4 and the delay fiber 5. It is expressed as: Among them, i is the imaginary unit, e is the natural constant, is the observable quantity of the system, After the interaction, the state of the output light is

[0062] After the light from the light source is pre-selected, it is divided into |H> light and |V> light. The |H> light passes through the AOM and the delay fiber and is reflected by the weak reflection element in turn, reaching the fiber coupler; the |V> light is first reflected by the weak reflection element in turn, then passes through the delay fiber and AOM, and reaches the fiber coupler. Set the AOM to Ω AOM Angular frequency modulation, when |H> light passes, Ω AOM =Ω0+kt, when |V> light passes, Ω AOM = 0; the optical paths of |H> light and |V> light are the same, so they arrive at the fiber coupler at the same time. In the weak reflection array, the phase delay of |H> light reflected by the i-th reflector is expressed as The phase of light traveling along the same path in opposite directions can be expressed as The phase difference between the two beams Where L a is the optical path of the delay fiber, L i is the optical path from the fiber 2×1 beam splitter to the i-th weak reflection element, ν is the speed of light in the fiber, ω c is the central angular frequency of the light source. Due to the effect of the delayed optical fiber, the light |V> reaches the weak reflection element first, and the light |H> reaches the weak reflection element later. The time difference is τ=L a / ν, in the time difference τ between |V> light and |H> light reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL,|H>The light phase becomes The phase difference is That is φ(t) introduced by the weak reflector array during the interaction process.

[0063] Step S2.3: After the light passes through the beam splitter, the post-selection state |f> is modulated to be within a preset orthogonal range with the pre-selection state, the post-selection angle of the post-selection process 1 is set to ε, and the post-selection angle of the post-selection process 2 is set to -ε, and the light intensity is projected onto the post-selection state. Post-selection process II The light intensity is used as the detection index for detection. The initial light intensity is I0(t), and the reflection coefficient of the i-th weak reflection element is r i , the light intensity reflected by the i-th weak reflection element received by the photodetector is The light intensity reflected by the i-th weak reflection element received by the photodetector 2 is In fact, the light intensity received by the photodetector is the sum of the light intensities reflected by all weak reflection elements. Therefore, it can be obtained that the light intensity received by the photodetector is The light intensity received by photodetector 2 is

[0064] Specifically, in step S3, the acoustic signal can be demodulated according to the phase change of the weak reflection element, and the light intensity received by the photodetector 1 and the photodetector 2 can be obtained. Through Fourier transform, the vibration information is demodulated from the phase change. Since the distance between each weak reflection element and the sound source is different, according to the sound source attenuation effect, the sound level received by each weak reflection element is also different. i (i=1,2,3…) is the attenuation coefficient from the sound source to the i-th weak reflection element, and the sound source signal is x(t);

[0065] According to the photoelastic effect, in the time difference τ between the light |V> and the light |H> reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL, where ΔL=γL i-1,i α i [x(t-τ)-x(t)], where γ is the effective photoelastic coefficient, L i-1,i is the distance between the i-1th weak reflection primitive and the i-th weak reflection primitive. You can get the frequency 2ΔLkt / υ is very small and can be ignored. It is deduced that the vibration ΔL is derived from the phase change Δθ i Extracted from C i There is no effect on vibration detection. Substituting ΔL into the equation gives right After fast Fourier transform, the frequency term f can be obtained i , phase term θ i and reflectivity r i , through the weak measurement technique, the reflectivity r i Each weak reflection element has a different L i , so the frequency Corresponding to each weak reflection primitive, the signals from different weak reflection primitives can be separated, and then the θ corresponding to each weak reflection primitive can be obtained. i .

[0066] Specifically, in step S4, by θ i Get the attenuation coefficient α corresponding to each weak reflection primitive i According to the corresponding relationship between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial positioning of the sound source is obtained through geometric calculation, which improves the positioning accuracy.

[0067] Example 2

[0068] The present invention also provides a distributed fiber Bragg grating sound source localization system based on weak measurement technology. The distributed fiber Bragg grating sound source localization system based on weak measurement technology can be realized by executing the process steps of the distributed fiber Bragg grating sound source localization method based on weak measurement technology, that is, those skilled in the art can understand the distributed fiber Bragg grating sound source localization method based on weak measurement technology as a preferred implementation of the distributed fiber Bragg grating sound source localization system based on weak measurement technology.

[0069] The present invention provides a distributed fiber Bragg grating sound source localization system based on weak measurement technology, comprising the following modules:

[0070] Module M1: Building a distributed fiber Bragg grating sensing platform based on weak measurement technology;

[0071] Module M2: Place the weak reflection array in the sound field. The weak reflection element is affected by the sound source signal and the optical path changes, thus changing the phase, and the light is received by the photoelectric detector.

[0072] Module M3: Perform Fourier transform on the difference between the signals of photodetector 1 and photodetector 2 to calculate the phase corresponding to each weak reflection primitive;

[0073] Module M4: According to the corresponding relationship between the phase of the weak reflection element and the sound pressure, the distance between the weak reflection element and the sound source is obtained;

[0074] Module M5: Locate the sound source based on the distance between the weak reflection element and the sound source.

[0075] Specifically, the distributed fiber Bragg grating sensing platform in the module M1 includes: a light source 1, a pre-selection process 2 (composed of a half wave plate and a polarizer), a fiber polarization beam splitter (PBS) 3, an acousto-optic modulator (AOM) 4, a delay fiber 5, a fiber 2×1 beam splitter 6, a weak reflection array 7, a fiber coupler 8, a beam splitter 9, a post-selection process 1 (composed of a half wave plate, a polarizer, and a quarter wave plate) 10, a photodetector 1 11, a post-selection process 2 (composed of a half wave plate, a polarizer, and a quarter wave plate) 12, a photodetector 2 13, and a computer 1 4; the light emitted by the light source 1 is modulated into a preset pre-selected state in the pre-selected process 2; in the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) via the acousto-optic modulator 4 and the delay fiber 5, and the above process is transmitted in the optical fiber; through the optical fiber coupler 8, the light in the optical fiber is converted into spatial light, and enters the post-selected process through the beam splitter 9, wherein the angles between the post-selected process 1 10 and the post-selected process 2 12 and the pre-selected process are opposite to each other; the two light intensities are received by the photodetector 1 11 and the photodetector 2 13 respectively, and the computer 14 performs data processing to determine the position of the sound source.

[0076] Specifically, the module M2 includes the following modules:

[0077] Module M2.1: modulate the light output by light source 1 into the pre-selection state |i> through pre-selection process 2, where |H> light is the light that vibrates horizontally, and |V> light is the light that vibrates vertically.

[0078] Module M2.2: The weak reflection array is composed of Bragg gratings. The optical path of the weak reflection element changes under the influence of the sound source signal, and is encoded into a time-varying phase φ(t) through the acousto-optic modulator 4 and the delay fiber 5. It is expressed as: Among them, i is the imaginary unit, e is the natural constant, is the observable quantity of the system, After the interaction, the state of the output light is

[0079] After the light from the light source is pre-selected, it is divided into |H> light and |V> light. The |H> light passes through the AOM and the delay fiber and is reflected by the weak reflection element in turn, reaching the fiber coupler; the |V> light is first reflected by the weak reflection element in turn, then passes through the delay fiber and AOM, and reaches the fiber coupler. Set the AOM to Ω AOM Angular frequency modulation, when |H> light passes, Ω AOM =Ω0+kt, when |V> light passes, Ω AOM= 0; the optical paths of |H> light and |V> light are the same, so they arrive at the fiber coupler at the same time. In the weak reflection array, the phase delay of |H> light reflected by the i-th reflector is expressed as The phase of light traveling along the same path in opposite directions can be expressed as The phase difference between the two beams Where L a is the optical path of the delay fiber, L i is the optical path from the fiber 2×1 beam splitter to the i-th weak reflection element, ν is the speed of light in the fiber, ω c is the central angular frequency of the light source. Due to the effect of the delayed optical fiber, the light |V> reaches the weak reflection element first, and the light |H> reaches the weak reflection element later. The time difference is τ=L a / ν, in the time difference τ between |V> light and |H> light reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL,|H>The light phase becomes The phase difference is That is φ(t) introduced by the weak reflector array during the interaction process.

[0080] Module M2.3: After the light passes through the beam splitter, the post-selection state |f> is modulated to be in a preset orthogonal range with the pre-selection state, the post-selection angle of the post-selection process one is set to ε, and the post-selection angle of the post-selection process two is set to -ε, and the light intensity is projected onto the post-selection state. Post-selection process II The light intensity is used as the detection index for detection. The initial light intensity is I0(t), and the reflection coefficient of the i-th weak reflection element is r i , the light intensity reflected by the i-th weak reflection element received by the photodetector is The light intensity reflected by the i-th weak reflection element received by the photodetector 2 is In fact, the light intensity received by the photodetector is the sum of the light intensities reflected by all weak reflection elements. Therefore, it can be obtained that the light intensity received by the photodetector is The light intensity received by photodetector 2 is

[0081] Specifically, in the module M3, the acoustic signal can be demodulated according to the phase change of the weak reflection element, and the light intensity received by the photodetector 1 and the photodetector 2 can be obtained. Through Fourier transform, the vibration information is demodulated from the phase change. Since the distance between each weak reflection element and the sound source is different, according to the sound source attenuation effect, the sound level received by each weak reflection element is also different. i (i=1,2,3…) is the attenuation coefficient from the sound source to the i-th weak reflection element, and the sound source signal is x(t);

[0082] According to the photoelastic effect, in the time difference τ between the light |V> and the light |H> reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL, where ΔL=γL i-1,i α i [x(t-τ)-x(t)], where γ is the effective photoelastic coefficient, L i-1,i is the distance between the i-1th weak reflection primitive and the i-th weak reflection primitive. You can get the frequency 2ΔLkt / υ is very small and can be ignored. It is deduced that the vibration ΔL is derived from the phase change Δθ i Extracted from C i There is no effect on vibration detection. Substituting ΔL into the equation gives right After fast Fourier transform, the frequency term f can be obtained i , phase term θ i and reflectivity r i , through the weak measurement technique, the reflectivity r i Each weak reflection element has a different L i , so the frequency Corresponding to each weak reflection primitive, the signals from different weak reflection primitives can be separated, and then the θ corresponding to each weak reflection primitive can be obtained. i .

[0083] Specifically, in the module M4, by θ i Get the attenuation coefficient α corresponding to each weak reflection primitive i According to the corresponding relationship between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial positioning of the sound source is obtained through geometric calculation, which improves the positioning accuracy.

[0084] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0085] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0086] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A distributed fiber Bragg grating sound source localization method based on weak measurement technology, characterized in that: include: Step S1: Building a distributed fiber Bragg grating sensing platform based on weak measurement technology; Step S2: placing the weak reflection array in the sound field, the weak reflection element is affected by the sound source signal, the optical path is changed, and the phase is changed, and the light is received by the photoelectric detector; Step S3: Perform Fourier transform on the difference between the signals of the photodetector 1 and the photodetector 2 to calculate the phase corresponding to each weak reflection primitive; Step S4: according to the corresponding relationship between the phase of the weak reflection primitive and the sound pressure, the distance between the weak reflection primitive and the sound source is obtained; Step S5: Locate the sound source based on the distance between the weak reflection element and the sound source.

2. The distributed fiber Bragg grating sound source localization method based on weak measurement technology according to claim 1 is characterized in that: The distributed fiber grating sensing platform comprises: a light source (1), a pre-selection process (2), a fiber polarization beam splitter (3), an acousto-optic modulator (4), a delay fiber (5), a fiber 2×1 beam splitter (6), a weak reflection array (7), a fiber coupler (8), a beam splitter (9), a post-selection process 1 (10), a photodetector 1 (11), a post-selection process 2 (12), a photodetector 2 (13) and a computer (14); The light emitted by the light source (1) is modulated into a preset pre-selection state in the pre-selection process (2); after passing through the optical fiber polarization beam splitter (3), in the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) through the acousto-optic modulator (4) and the delay optical fiber (5), and then passes through the optical fiber 2×1 beam splitter (6) to reach the weak reflection array (7); after passing through the optical fiber coupler (8), the light in the optical fiber is converted into spatial light, and enters the post-selection process through the beam splitter (9), wherein the angles between the post-selection process 1 (10) and the post-selection process 2 (12) and the pre-selection are opposite to each other; the two paths of light intensity are respectively received by the photodetector 1 (11) and the photodetector 2 (13), and the data is processed by the computer (14) to determine the position of the sound source.

3. The distributed fiber Bragg grating sound source localization method based on weak measurement technology according to claim 2 is characterized in that: The step S2 comprises the following steps: Step S2.1: modulate the light output by the light source into a pre-selected state |i> through a pre-selection process, where |H> light is light that vibrates horizontally, and |V> light is light that vibrates vertically; Step S2.2: The weak reflection array is composed of Bragg gratings. The optical path of the weak reflection element changes under the influence of the sound source signal and is encoded into a time-varying phase φ(t) through the acousto-optic modulator and the delay fiber. It is expressed as: Among them, i is the imaginary unit, e is the natural constant, is the observable quantity of the system, After the interaction, the state of the output light is The light from the light source is pre-selected and divided into |H> light and |V> light. The |H> light passes through the AOM and the delay fiber and is reflected by the weak reflection element in turn to reach the fiber coupler; the |V> light is first reflected by the weak reflection element in turn, then passes through the delay fiber and AOM to reach the fiber coupler; the AOM is set to Ω AOM Angular frequency modulation, when |H> light passes, Ω AOM =Ω0+kt, when |V> light passes, Ω AOM =0; the optical paths of |H> light and |V> light are the same, so they arrive at the fiber coupler at the same time; In a weak reflection array, the phase delay of the light reflected by the i-th reflector |H> is expressed as Ω AOM ), the phase of light propagating along the same path in opposite directions is expressed as The phase difference between the two beams is Where L a is the optical path of the delay fiber, L i is the optical path from the fiber 2×1 beam splitter to the i-th weak reflection element, ν is the speed of light in the fiber, ω c is the central angular frequency of the light source. Due to the effect of the delayed optical fiber, the light |V> reaches the weak reflection element first, and the light |H> reaches the weak reflection element later. The time difference is τ=L a / ν, in the time difference τ between |V> light and |H> light reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL,|H>The light phase becomes The phase difference is That is, φ(t) introduced by the weak reflector array during the interaction process; Step S2.3: After the light passes through the beam splitter, the post-selection state |f> is modulated to be within a preset orthogonal range with the pre-selection state, the post-selection angle of the post-selection process 1 is set to ε, and the post-selection angle of the post-selection process 2 is set to -ε, and the light intensity is projected onto the post-selection state. The post-selection process 1 is The second post-selection process is The light intensity is used as the detection index for detection. The initial light intensity is I0(t), and the reflection coefficient of the i-th weak reflection element is r i , the light intensity reflected by the i-th weak reflection element received by the photodetector is The light intensity reflected by the i-th weak reflection element received by the photodetector 2 is In fact, the light intensity received by the photodetector is the sum of the light intensities reflected by all weak reflection elements. Therefore, the light intensity received by the photodetector is The light intensity received by photodetector 2 is 4. The distributed fiber Bragg grating sound source localization method based on weak measurement technology according to claim 3 is characterized in that: The step S3 comprises: The acoustic signal is demodulated according to the phase change of the weak reflection element, and the light intensity received by the photodetector 1 and the photodetector 2 is obtained. Through Fourier transform, the vibration information is demodulated from the phase change. Since the distance between each weak reflection element and the sound source is different, according to the sound source attenuation effect, the sound level received by each weak reflection element is also different. i is the attenuation coefficient from the sound source to the i-th weak reflection element, i = 1, 2, 3…, the sound source signal is x(t); According to the photoelastic effect, during the time difference τ between the light |V> and the light |H> reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL, where ΔL=γL i-1,i α i [x(t-τ)-x(t)], where γ is the effective photoelastic coefficient, L i-1,i is the distance between the i-1th weak reflection primitive and the i-th weak reflection primitive; Get frequency Ignoring the size of 2ΔLkt / υ, It is deduced that the vibration ΔL is derived from the phase change Δθ i Extracted from C i There is no effect on vibration detection. Substituting ΔL into the equation gives right After fast Fourier transform, the frequency term f is obtained i , phase term θ i and reflectivity r i , through weak measurement technology, amplify the reflectivity r i ; Each weak reflection element has a different L i , so the frequency Corresponding to each weak reflection primitive, the signals from different weak reflection primitives are separated, and then the θ corresponding to each weak reflection primitive is obtained. i .

5. The distributed fiber Bragg grating sound source localization method based on weak measurement technology according to claim 4 is characterized in that: The step S4 comprises: i Get the attenuation coefficient α corresponding to each weak reflection primitive i According to the corresponding relationship between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial positioning of the sound source is obtained through geometric calculation.

6. A distributed fiber Bragg grating sound source localization system based on weak measurement technology, characterized in that: include: Module M1: Building a distributed fiber Bragg grating sensing platform based on weak measurement technology; Module M2: Place the weak reflection array in the sound field. The weak reflection element is affected by the sound source signal and the optical path changes, thus changing the phase, and the light is received by the photoelectric detector. Module M3: Perform Fourier transform on the difference between the signals of photodetector 1 and photodetector 2 to calculate the phase corresponding to each weak reflection primitive; Module M4: According to the corresponding relationship between the phase of the weak reflection element and the sound pressure, the distance between the weak reflection element and the sound source is obtained; Module M5: Locate the sound source based on the distance between the weak reflection element and the sound source.

7. The distributed fiber Bragg grating sound source localization system based on weak measurement technology according to claim 6, characterized in that: The distributed fiber grating sensing platform comprises: a light source (1), a pre-selection process (2), a fiber polarization beam splitter (3), an acousto-optic modulator (4), a delay fiber (5), a fiber 2×1 beam splitter (6), a weak reflection array (7), a fiber coupler (8), a beam splitter (9), a post-selection process 1 (10), a photodetector 1 (11), a post-selection process 2 (12), a photodetector 2 (13) and a computer (14); The light emitted by the light source (1) is modulated into a preset pre-selection state in the pre-selection process (2); after passing through the optical fiber polarization beam splitter (3), in the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) through the acousto-optic modulator (4) and the delay optical fiber (5), and then passes through the optical fiber 2×1 beam splitter (6) to reach the weak reflection array (7); after passing through the optical fiber coupler (8), the light in the optical fiber is converted into spatial light, and enters the post-selection process through the beam splitter (9), wherein the angles between the post-selection process 1 (10) and the post-selection process 2 (12) and the pre-selection are opposite to each other; the two paths of light intensity are respectively received by the photodetector 1 (11) and the photodetector 2 (13), and the data is processed by the computer (14) to determine the position of the sound source.

8. The distributed fiber Bragg grating sound source localization system based on weak measurement technology according to claim 7, characterized in that: The module M2 comprises: Module M2.1: modulate the light output by the light source into the pre-selected state |i> through the pre-selection process, where |H> light is light that vibrates horizontally, and |V> light is light that vibrates vertically; Module M2.2: The weak reflection array consists of Bragg gratings. The optical path of the weak reflection element changes under the influence of the sound source signal. After passing through the acousto-optic modulator and the delay optical fiber, it is encoded into a time-varying phase φ(t) and interacts It is expressed as: where i is the imaginary unit and e is the natural constant, is the observable of the system, |V><V|. After the interaction, the state of the output light is The light from the light source is pre-selected and divided into |H> light and |V> light. The |H> light passes through the AOM and the delay fiber and is reflected by the weak reflection element in turn to reach the fiber coupler; the |V> light is first reflected by the weak reflection element in turn, then passes through the delay fiber and AOM to reach the fiber coupler; the AOM is set to Ω AOM Angular frequency modulation, when |H> light passes, Ω AOM =Ω0+kt, when |V> light passes, Ω AOM =0; the optical paths of |H> light and |V> light are the same, so they arrive at the fiber coupler at the same time; In a weak reflection array, the phase delay of the light reflected by the i-th reflector |H> is expressed as The phase of light traveling along the same path in opposite directions is expressed as The phase difference between the two beams is Where L a is the optical path of the delay fiber, L i is the optical path from the fiber 2×1 beam splitter to the i-th weak reflection element, ν is the speed of light in the fiber, ω c is the central angular frequency of the light source. Due to the effect of the delayed optical fiber, the light |V> reaches the weak reflection element first, and the light |H> reaches the weak reflection element later. The time difference is τ=L a / ν, in the time difference τ between |V> light and |H> light reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL,|H>The light phase becomes The phase difference is That is, φ(t) introduced by the weak reflector array during the interaction process; Module M2.3: After the light passes through the beam splitter, the post-selection state |f> is modulated to be in a preset orthogonal range with the pre-selection state. The post-selection angle of the post-selection process 1 is set to ε, and the post-selection angle of the post-selection process 2 is set to -ε. The light intensity is projected onto the post-selection state. The post-selection process 1 is The second post-selection process is The light intensity is used as the detection index for detection. The initial light intensity is I0(t), and the reflection coefficient of the i-th weak reflection element is r i , the light intensity reflected by the i-th weak reflection element received by the photodetector is The light intensity reflected by the i-th weak reflection element received by the photodetector 2 is In fact, the light intensity received by the photodetector is the sum of the light intensities reflected by all weak reflection elements. Therefore, the light intensity received by the photodetector is The light intensity received by photodetector 2 is 9. The distributed fiber Bragg grating sound source localization system based on weak measurement technology according to claim 8, characterized in that: The module M3 comprises: The acoustic signal is demodulated according to the phase change of the weak reflection element, and the light intensity received by the photodetector 1 and the photodetector 2 is obtained. Through Fourier transform, the vibration information is demodulated from the phase change. Since the distance between each weak reflection element and the sound source is different, according to the sound source attenuation effect, the sound level received by each weak reflection element is also different. i is the attenuation coefficient from the sound source to the i-th weak reflection element, i = 1, 2, 3…, the sound source signal is x(t); According to the photoelastic effect, during the time difference τ between the light |V> and the light |H> reaching the i-th weak reflection element, the position of the i-th weak reflection element changes from L i Change to L i +ΔL, where ΔL=γL i-1,i α i [x(t-τ)-x(t)], where γ is the effective photoelastic coefficient, L i-1,i is the distance between the i-1th weak reflection primitive and the i-th weak reflection primitive; Get frequency Ignoring the size of 2ΔLkt / υ, It is deduced that the vibration ΔL is derived from the phase change Δθ i Extracted from C i There is no effect on vibration detection. Substituting ΔL into the equation gives right After fast Fourier transform, the frequency term f is obtained i , phase term θ i and reflectivity r i , through weak measurement technology, amplify the reflectivity r i ; Each weak reflection element has a different L i , so the frequency Corresponding to each weak reflection primitive, the signals from different weak reflection primitives are separated, and then the θ corresponding to each weak reflection primitive is obtained. i .

10. The distributed fiber Bragg grating sound source localization system based on weak measurement technology according to claim 9, characterized in that: The module M4 includes: i Get the attenuation coefficient α corresponding to each weak reflection primitive i According to the corresponding relationship between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial positioning of the sound source is obtained through geometric calculation.

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