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

Abstract

This invention provides a distributed fiber Bragg grating sound source localization method and system based on weak measurement technology, comprising: Step S1: constructing a distributed fiber Bragg grating sensing platform based on weak measurement technology; Step S2: placing a weak reflection array in the sound field, where the weak reflection elements are affected by the sound source signal, thus changing their phase, and receiving the light through a photodetector; Step S3: performing a Fourier transform on the difference between the signals of photodetector one and photodetector two to calculate the phase corresponding to each weak reflection element; Step S4: obtaining the distance between the weak reflection element and the sound source based on the correspondence between the phase of the weak reflection element and the sound pressure; Step S5: locating the sound source based on the distance between the weak reflection element and the sound source. This invention uses low-reflectivity weak reflection elements to reduce transmission loss, and allows for convenient multi-point measurement without increasing output optical power, reducing noise and high power loss, and improving positioning accuracy.

Description

Technical Field

[0001] This invention relates to the technical field of fiber Bragg gratings, and more specifically, to a method and system for locating sound sources in distributed fiber Bragg gratings based on weak measurement technology. Background Technology

[0002] Microphone array-based sound source localization technology boasts advantages such as flexible beam control, high spatial resolution, and strong anti-interference capabilities. However, the sensor arrays are typically composed of traditional condenser and dynamic microphones, making them difficult to apply in harsh environments with strong electromagnetic interference. Fiber Bragg gratings (FBGs) offer significant advantages for sound source localization in certain environments, but their high sensor cost, complex optical path structure, and failure to fully utilize the high capacity of fiber optic sensing systems hinder the construction of large-scale sensor arrays. Currently, most fiber optic sensing localization methods require more measurement points and a larger number of gratings to achieve higher accuracy, necessitating the use of erbium-doped fiber amplifiers, which introduce noise and significant power loss. Based on these reasons, this paper considers how to achieve higher accuracy sound localization without optical power amplification.

[0003] Patent document CN113176536A discloses a step-by-step focusing algorithm for rapid and accurate localization of noise sources. The first step involves using M sound pressure sensors to form a measurement array W on a measurement surface, measuring the sound pressure data at each point of the array W. The second step involves a first focusing process, dividing the focusing surface into a regular grid, where each cell is a square. The intersection of the grid points is the focal point of the sound source, and the distance between adjacent intersection points is defined as 'd', i.e., the interval between two adjacent focal points is 'd'. The focusing algorithm identifies a large area containing the sound source. The third step involves a second focusing process, precisely dividing the large area identified in the second step and repeating the focusing algorithm from the previous step to perform a second precise localization, thus pinpointing the exact location of the sound source. However, the technical means employed in this patent differ from those of the present invention, and the patent cannot completely solve the aforementioned technical problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a distributed fiber Bragg grating sound source localization method and system based on weak measurement technology.

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

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

[0007] Step S2: Place the weak reflection array in the sound field. The weak reflection element is affected by the sound source signal, which changes the optical path and thus the phase. The light is received by the photodetector.

[0008] Step S3: Perform a Fourier transform on the difference between the signals of photodetector one and photodetector two to calculate the phase corresponding to each weak reflection element;

[0009] Step S4: Based on the correspondence between the phase of the weak reflection element and the sound pressure, obtain the distance between the weak reflection element and the sound source;

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

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

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

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

[0014] Step S2.1: Modulate the light output from the light source into a pre-selection state |i> through a pre-selection process, where |H> Light vibrates in the horizontal direction, |V> Light vibrates in the vertical direction;

[0015] Step S2.2: The weak reflection array consists of Bragg gratings. Under the influence of the acoustic source signal, the optical path of the weak reflection element changes, and this change is encoded into a time-varying phase φ(t) by the acousto-optic modulator and delay fiber. Represented as: Where i is the imaginary unit and e is the natural constant. For observable measurement of the system, After the interaction, the state of the output light is:

[0016] Light from the light source undergoes pre-selection, splitting into |H> light and |V> light. The |H> light passes through the AOM and delay fiber, then is sequentially reflected by weak reflection elements before reaching the fiber coupler. The |V> light is first reflected by weak reflection elements, then passes through the delay fiber and AOM before reaching the fiber coupler. The AOM is set to Ω... AOM Angular frequency modulation, when |H> light passes through, Ω AOM =Ω0+kt, when |V> the light passes through, Ω AOM =0; |H> light and |V> light travel the same optical path, therefore they arrive at the fiber coupler simultaneously;

[0017] In a weakly reflective array, the phase delay of the |H> light reflected by the i-th reflector is expressed as: The phase of light propagating along the same path in opposite directions is represented as: The phase difference between the two beams is Where L a For the optical path of the delay fiber, L i Let ν be the optical path from the 2×1 fiber beam splitter to the i-th weakly reflecting element, and ω be the speed of light in the fiber. c Let L be the center angular frequency of the light source. Due to the effect of the delay fiber, light with |V> arrives at the weak reflection element first, and light with |H> arrives at the weak reflection element later, with a time difference of τ = L. a / ν, in the time difference τ between the arrival of |V> light and |H> light at 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 changes Phase difference is This refers to 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 to the pre-selection state. The post-selection angle of post-selection process one is set to ε, and the post-selection angle of post-selection process two is set to -ε. The light intensity is projected onto the post-selection state. Post-selection process one is... The second selection process is

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

[0020] Preferably, step S3 includes:

[0021] The acoustic signal is demodulated based on the phase change of the weak reflection element, and the light intensity received by photodetector one and photodetector two is used to obtain... By using Fourier transform, vibration information is demodulated from the phase change. Since each weakly reflecting element is at a different distance from the sound source, and due to the sound source attenuation effect, the volume of the sound received by each weakly reflecting element from the sound source is also different. α i Let x(t) be the attenuation coefficient from the sound source to the i-th weak reflection element, where i = 1, 2, 3… and the sound source signal is x(t).

[0022] According to the photoelastic effect, during the time difference τ between the arrival of |V> light and |H> light at the i-th weakly reflecting element, the position of the i-th weakly reflecting 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, and L i-1,i Let be the distance between the (i-1)th weak reflection primitive and the ith weak reflection primitive; from Obtain frequency Ignore the magnitude of 2ΔLkt / υ The derivation shows that the vibration ΔL originates from the phase transition Δθ. i Extracted from C i It has no effect on vibration detection; substituting ΔL yields... right After performing a fast Fourier transform, the frequency term f is obtained. i Phase term θ i and reflectivity r i By using weak measurement techniques, the reflectivity r is amplified. i Each weak reflection primitive has a different L i Therefore, frequency Corresponding to each weak reflection primitive, signals from different weak reflection primitives are separated, thereby obtaining θ corresponding to each weak reflection primitive. i .

[0023] Preferably, step S4 includes: via θ i The attenuation coefficient α corresponding to each weak reflection element is obtained. iBased on the correspondence between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial location of the sound source is obtained through geometric calculation.

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

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

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

[0027] Module M3: Performs a Fourier transform on the difference between the signals from photodetector one and photodetector two to calculate the phase corresponding to each weak reflection element;

[0028] Module M4: Based on the correspondence 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: Locates the sound source by measuring the distance between the weak reflection element and the sound source.

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

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

[0032] Preferably, the module M2 includes:

[0033] Module M2.1: Modulates the light output from the light source into a pre-selected state |i> through a pre-selection process, where |H> Light vibrates in the horizontal direction, |V> Light vibrates in the vertical direction;

[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, and is encoded into a time-varying phase φ(t) through an acou-optic modulator and a delay fiber, 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 is preselected and 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 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 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 by, Ω AOM =Ω0 + kt, when the |V> light passes by, 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 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 delay 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-selected state |f> is modulated to be within a preset orthogonal range with the pre-selected 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-selected state. The first post-selection process is The second selection process is

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

[0039] Preferably, the module M3 includes:

[0040] The acoustic signal is demodulated based on the phase change of the weak reflection element, and the light intensity received by photodetector one and photodetector two is used to obtain... By using Fourier transform, vibration information is demodulated from the phase change. Since each weakly reflecting element is at a different distance from the sound source, and due to the sound source attenuation effect, the volume of the sound received by each weakly reflecting element from the sound source is also different. α i Let x(t) be the attenuation coefficient from the sound source to the i-th weak reflection element, where i = 1, 2, 3… and the sound source signal is x(t).

[0041] According to the photoelastic effect, during the time difference τ between the arrival of |V> light and |H> light at the i-th weakly reflecting element, the position of the i-th weakly reflecting 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, and L i-1,i Let be the distance between the (i-1)th weak reflection primitive and the ith weak reflection primitive; from Obtain frequency Ignore the magnitude of 2ΔLkt / υ The derivation shows that the vibration ΔL originates from the phase transition Δθ. i Extracted from C i It has no effect on vibration detection; substituting ΔL yields... right After performing a fast Fourier transform, the frequency term f is obtained. i Phase term θ i and reflectivity r iBy using weak measurement techniques, the reflectivity r is amplified. i Each weak reflection primitive has a different L i Therefore, frequency Corresponding to each weak reflection primitive, signals from different weak reflection primitives are separated, thereby obtaining θ corresponding to each weak reflection primitive. i .

[0042] Preferably, the module M4 includes: via θ i The attenuation coefficient α corresponding to each weak reflection element is obtained. i Based on the correspondence between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial location 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. This invention selects a weakly reflective element with low reflectivity to reduce transmission loss. It can be easily used for multi-point measurement without increasing the output optical power, thereby reducing noise and high power loss and improving positioning accuracy.

[0045] 2. This invention has wide applications. By combining weak measurement technology with fiber optic grating sensors, it can resist electromagnetic interference and realize distributed long-distance sensing, thus overcoming the shortcomings of existing fiber optic sensing and positioning technologies. Attached Figure Description

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

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

[0048] Figure label:

[0049] 1-Light source; 2-Pre-selection process; 3-Fiber polarization beam splitter; 4-Acousto-optic modulator; 5-Delay fiber; 6-Fiber 2×1 beam splitter; 7-Weak reflection array; 8-Fiber coupler; 9-Band splitter; 10-Post-selection process one; 11-Photodetector one; 12-Post-selection process two; 13-Photodetector two; 14-Computer. Detailed Implementation

[0050] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0051] Example 1

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

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

[0054] Step S2: Place the weak reflection array in the sound field. The weak reflection element is affected by the sound source signal, which changes the optical path and thus the phase. The light is received by the photodetector.

[0055] Step S3: Perform a Fourier transform on the difference between the signals of photodetector one and photodetector two to calculate the phase corresponding to each weak reflection element.

[0056] Step S4: Based on the correspondence between the phase of the weak reflection element and the sound pressure, obtain the distance between the weak reflection element and the sound source;

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

[0058] Specifically, the distributed fiber optic 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 2×1 fiber beam splitter 6, a weak reflection array 7, a fiber coupler 8, a beam splitter 9, a post-selection process one (composed of a half-wave plate, a polarizer, and a quarter-wave plate) 10, a photodetector one 11, a post-selection process two (composed of a half-wave plate, a polarizer, and a quarter-wave plate) 12, a photodetector two 13, and a computer 1. 4; The light emitted by light source 1 is modulated into a preset pre-selection state in the pre-selection process 2; In the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) by 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-selection process through the beam splitter 9, wherein the angles between post-selection process one 10 and post-selection process two 12 and the pre-selection process are opposites; The two light intensities are received by photodetector one 11 and photodetector two 13 respectively, and the computer 14 performs data processing to determine the location of the sound source.

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

[0060] Step S2.1: The light output from light source 1 is modulated into a pre-selection state |i> through a pre-selection process 2, where |H> light is light that vibrates in the horizontal direction, and |V> light is light that vibrates in the vertical direction.

[0061] Step S2.2: The weak reflection array consists of Bragg gratings. Under the influence of the acoustic source signal, the optical path of the weak reflection element changes, and this change is encoded into a time-varying phase φ(t) by the acousto-optic modulator 4 and the delay fiber 5. Represented as: Where i is the imaginary unit and e is the natural constant. For observable measurement of the system, After the interaction, the state of the output light is:

[0062] Light from the light source undergoes pre-selection, splitting into |H> light and |V> light. The |H> light passes through the AOM and delay fiber, then is sequentially reflected by weak reflection elements before reaching the fiber coupler. The |V> light is first reflected by weak reflection elements, then passes through the delay fiber and AOM before reaching the fiber coupler. The AOM is set to Ω... AOM Angular frequency modulation, when |H> light passes through, Ω AOM =Ω0+kt, when |V> the light passes through, Ω AOM =0; |H> light and |V> light travel the same optical path, therefore they arrive at the fiber coupler simultaneously. In a weakly reflective array, the phase delay of the |H> light reflected by the i-th reflector is expressed as... The phase of light propagating along the same path in opposite directions can be represented as: Phase difference between two beams Where L a For the optical path of the delay fiber, L i Let ν be the optical path from the 2×1 fiber beam splitter to the i-th weakly reflecting element, and ω be the speed of light in the fiber. c Let L be the center angular frequency of the light source. Due to the effect of the delay fiber, light with |V> arrives at the weak reflection element first, and light with |H> arrives at the weak reflection element later, with a time difference of τ = L. a / ν, in the time difference τ between the arrival of |V> light and |H> light at 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 changes Phase difference is This refers to 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 to the pre-selection state. The post-selection angle of post-selection process one is set to ε, and the post-selection angle of post-selection process two is set to -ε. The light intensity is projected onto the post-selection state. Post-selection process one Post-selection process two Light intensity is used as the detection index. The initial light intensity is I0(t), and the reflection coefficient of the i-th weakly reflective element is r. i The intensity of the light reflected by the i-th weakly reflective element received by the photodetector is The intensity of the light reflected by the i-th weakly reflective element received by photodetector 2 is In reality, the light intensity received by the photodetector is the sum of the light intensities reflected by all the weakly reflective elements. Therefore, the light intensity received by photodetector one is... The light intensity received by photodetector 2 is

[0064] Specifically, in step S3, the acoustic signal can be demodulated based on the phase change of the weak reflection element, and the intensity of the light received by photodetector one and photodetector two can be used to obtain... By using Fourier transform, vibration information is demodulated from the phase change. Since each weakly reflecting element is at a different distance from the sound source, and due to the sound source attenuation effect, the volume of the sound received by each weakly reflecting element from the sound source is also different. α i (i = 1, 2, 3…) represents 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, as mentioned above, during the time difference τ between the arrival of |V> light and |H> light at the i-th weakly reflective element, the position of the i-th weakly reflective 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, and L i-1,i Let be the distance between the (i-1)th weak reflection primitive and the ith weak reflection primitive. Frequency can be obtained 2ΔLkt / υ is very small and can be ignored. The derivation shows that the vibration ΔL originates from the phase transition Δθ. i Extracted from C i It has no effect on vibration detection; substituting ΔL yields... right After performing a Fast Fourier Transform, the frequency term f can be obtained. i Phase term θ i and reflectivity r i By using weak measurement techniques, the reflectivity r was amplified. i Each weakly reflective primitive has a different L. i Therefore, frequency Corresponding to each weak reflection primitive, signals from different weak reflection primitives can be separated, thereby obtaining θ corresponding to each weak reflection primitive. i .

[0066] Specifically, in step S4, through θ i The attenuation coefficient α corresponding to each weak reflection element is obtained. i Based on the correspondence between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained. The spatial positioning of the sound source is obtained through geometric calculation, thereby improving 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 implemented 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 embodiment of the distributed fiber Bragg grating sound source localization system based on weak measurement technology.

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

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

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

[0072] Module M3: Performs a Fourier transform on the difference between the signals of photodetector one and photodetector two to calculate the phase corresponding to each weak reflection element;

[0073] Module M4: Based on the correspondence 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: Locates the sound source by measuring the distance between the weak reflection element and the sound source.

[0075] Specifically, the distributed fiber optic grating sensing platform in 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 2×1 fiber beam splitter 6, a weak reflection array 7, a fiber coupler 8, a beam splitter 9, a post-selection process one (composed of a half-wave plate, a polarizer, and a quarter-wave plate) 10, a photodetector one 11, a post-selection process two (composed of a half-wave plate, a polarizer, and a quarter-wave plate) 12, a photodetector two 13, and a computer 1. 4; The light emitted by light source 1 is modulated into a preset pre-selection state in the pre-selection process 2; In the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase φ(t) by 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-selection process through the beam splitter 9, wherein the angles between post-selection process one 10 and post-selection process two 12 and the pre-selection process are opposites; The two light intensities are received by photodetector one 11 and photodetector two 13 respectively, and the computer 14 performs data processing to determine the location of the sound source.

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

[0077] Module M2.1: Modulates the light output from light source 1 into a pre-selection state |i> through a pre-selection process 2, where |H> light is light that vibrates in the horizontal direction, and |V> light is light that vibrates in the vertical direction.

[0078] Module M2.2: The weak reflection array consists of Bragg gratings. The optical path of the weak reflection elements changes under the influence of the acoustic source signal, and is encoded into a time-varying phase φ(t) by the acousto-optic modulator 4 and the delay fiber 5. These elements interact... Represented as: Where i is the imaginary unit and e is the natural constant. For observable measurement of the system, After the interaction, the state of the output light is:

[0079] Light from the light source undergoes pre-selection, splitting into |H> light and |V> light. The |H> light passes through the AOM and delay fiber, then is sequentially reflected by weak reflection elements before reaching the fiber coupler. The |V> light is first reflected by weak reflection elements, then passes through the delay fiber and AOM before reaching the fiber coupler. The AOM is set to Ω... AOM Angular frequency modulation, when |H> light passes through, Ω AOM =Ω0+kt, when |V> the light passes through, Ω AOM=0; |H> light and |V> light travel the same optical path, therefore they arrive at the fiber coupler simultaneously. In a weakly reflective array, the phase delay of the |H> light reflected by the i-th reflector is expressed as... The phase of light propagating along the same path in opposite directions can be represented as: Phase difference between two beams Where L a For the optical path of the delay fiber, L i Let ν be the optical path from the 2×1 fiber beam splitter to the i-th weakly reflecting element, and ω be the speed of light in the fiber. c Let L be the center angular frequency of the light source. Due to the effect of the delay fiber, light with |V> arrives at the weak reflection element first, and light with |H> arrives at the weak reflection element later, with a time difference of τ = L. a / ν, in the time difference τ between the arrival of |V> light and |H> light at 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 changes Phase difference is This refers to 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 within a preset orthogonal range to the pre-selection state. The post-selection angle of post-selection process one is set to ε, and the post-selection angle of post-selection process two is set to -ε. The light intensity is projected onto the post-selection state. Post-selection process one... Post-selection process two Light intensity is used as the detection index. The initial light intensity is I0(t), and the reflection coefficient of the i-th weakly reflective element is r. i The intensity of the light reflected by the i-th weakly reflective element received by the photodetector is The intensity of the light reflected by the i-th weakly reflective element received by photodetector 2 is In reality, the light intensity received by the photodetector is the sum of the light intensities reflected by all the weakly reflective elements. Therefore, the light intensity received by photodetector one is... The light intensity received by photodetector 2 is

[0081] Specifically, in module M3, the acoustic signal can be demodulated based on the phase change of the weak reflection element, and the intensity of the light received by photodetector one and photodetector two can be used to obtain... By using Fourier transform, vibration information is demodulated from the phase change. Since each weakly reflecting element is at a different distance from the sound source, and due to the sound source attenuation effect, the volume of the sound received by each weakly reflecting element from the sound source is also different. α i (i = 1, 2, 3…) represents 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, as mentioned above, during the time difference τ between the arrival of |V> light and |H> light at the i-th weakly reflective element, the position of the i-th weakly reflective 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, and L i-1,i Let be the distance between the (i-1)th weak reflection primitive and the ith weak reflection primitive. Frequency can be obtained 2ΔLkt / υ is very small and can be ignored. The derivation shows that the vibration ΔL originates from the phase transition Δθ. i Extracted from C i It has no effect on vibration detection; substituting ΔL yields... right After performing a Fast Fourier Transform, the frequency term f can be obtained. i Phase term θ i and reflectivity r i By using weak measurement techniques, the reflectivity r was amplified. i Each weakly reflective primitive has a different L. i Therefore, frequency Corresponding to each weak reflection primitive, signals from different weak reflection primitives can be separated, thereby obtaining θ corresponding to each weak reflection primitive. i .

[0083] Specifically, in module M4, via θ i The attenuation coefficient α corresponding to each weak reflection element is obtained. i Based on the correspondence between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained. The spatial positioning of the sound source is obtained through geometric calculation, thereby improving the positioning accuracy.

[0084] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0085] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented 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, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0086] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for locating a distributed fiber optic grating sound source based on weak measurement technology, characterized in that, include: Step S1: Build a distributed fiber optic grating sensing platform based on weak measurement technology; Step S2: Place the weak reflection array in the sound field. The weak reflection element is affected by the sound source signal, which changes the optical path and thus the phase. The light is received by the photodetector. Step S3: Perform a Fourier transform on the difference between the signals of photodetector one and photodetector two to calculate the phase corresponding to each weak reflection element; Step S4: Based on the correspondence between the phase of the weak reflection element and the sound pressure, obtain the distance between the weak reflection element and the sound source; Step S5: Locate the sound source by measuring the distance between the weak reflection element and the sound source; Step S3 includes: The acoustic signal is demodulated based on the phase change of the weak reflection element, and the light intensity received by photodetector one and photodetector two is used to obtain... By using Fourier transform, 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 volume of the sound received by each weak reflection element from the sound source is also different. Let be the attenuation coefficient from the sound source to the i-th weakly reflecting element. The sound source signal is ; The intensity of the light received by the photodetector. The intensity of the light received by photodetector two. The initial light intensity, To select the angle later, Phase difference; According to the photoelastic effect, Light and Time difference of light reaching the i-th weakly reflecting primitive In the middle, the position of the i-th weak reflection primitive starts from... Change to ,in In the formula For the effective photoelastic coefficient, Let be the distance between the (i-1)th weak reflection primitive and the ith weak reflection primitive. For time difference; by to obtain frequency ,neglect Size, ,in To delay the optical path of the fiber, The speed of light in an optical fiber. The central angular frequency of the light source is given; the vibration is derived. From phase transition Extracted from It has no impact on vibration detection. Substitute to get ;right After performing a fast Fourier transform, the frequency term is obtained. Phase Term and reflectivity Amplify reflectivity through weak measurement techniques Each weak reflection primitive has different Therefore, frequency Corresponding to each weak reflection primitive, signals from different weak reflection primitives are separated, thereby obtaining the signal corresponding to each weak reflection primitive. .

2. The distributed fiber optic grating sound source localization method based on weak measurement technology according to claim 1, characterized in that, The distributed fiber optic grating sensing platform includes: a light source (1), a pre-selection process (2), a fiber polarization beam splitter (3), an acousto-optic modulator (4), a delay fiber (5), and fiber 2.

1. Beam splitter (6), weak reflection array (7), fiber coupler (8), beam splitter (9), post-selection process one (10), photodetector one (11), post-selection process two (12), photodetector two (13) and computer (14). The light emitted by the light source (1) is modulated into a preset preselection state during the preselection process (2); after passing through the fiber polarization beam splitter (3), during the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase by the acousto-optic modulator (4) and the delay fiber (5). Then through fiber optic 2 1. The beam splitter (6) reaches the weak reflection array (7); through the fiber coupler (8), the light in the fiber is converted into spatial light, and enters the post-selection process through the beam splitter (9). The angles between the first post-selection process (10) and the second post-selection process (12) and the first selection process are opposites. The two light intensities are received by photodetector 1 (11) and photodetector 2 (13) respectively, and the data is processed by the computer (14) to determine the location of the sound source.

3. The distributed fiber optic grating sound source localization method based on weak measurement technology according to claim 2, characterized in that, Step S2 includes the following steps: Step S2.1: Modulate the light output from the light source into a pre-selected state through a pre-selection process. ,in , Light is light that vibrates in the horizontal direction. Light is light that vibrates in a perpendicular direction; Step S2.2: The weak reflection array is composed of Bragg gratings. Under the influence of the acoustic source signal, the optical path of the weak reflection element changes, and is encoded into a time-varying phase by the acousto-optic modulator and delay fiber. ,interaction Represented as: ,in, The imaginary unit, It is a natural constant. For observable measurement of the system, After the interaction, the output light is in the following state: ; Light from the light source is pre-selected and divided into... Light and Light, After passing through the AOM and the time-delay fiber, the light is reflected in sequence by the weak reflection element and reaches the fiber coupler. The light is first reflected sequentially by weak reflection elements, then passes through a time-delay fiber and an AOM (Aspect-Oriented Fiber Optic Unit) before reaching the fiber coupler; the AOM is configured to... Angular frequency modulation, in When light passes by, ,exist When light passes by, ; Light and Since the light travels the same optical path, they arrive at the fiber coupler simultaneously. In a weakly reflective array, the i-th reflector reflects... The phase delay of light is expressed as , The phase of light traveling along the same path in opposite directions is represented as The phase difference between the two beams is ,in To delay the optical path of the fiber, This is the optical path from the 2×1 fiber beam splitter to the i-th weakly reflecting element. The speed of light in an optical fiber. The center angular frequency of the light source is determined by the delay fiber. Light first reaches the weakly reflective elementary element. The time difference between the light reaching the weakly reflecting elementary element is... ,exist Light and Time difference of light reaching the i-th weakly reflecting primitive In the middle, the position of the i-th weak reflection primitive starts from... Change to , Light phase change The phase difference is , This refers to the interaction process introduced by the weak reflector array. ; Step S2.3: After the light passes through the beam splitter, the post-selected state... The modulation is set to be within a preset orthogonal range to the previous selection state, and the post-selection angle of the first post-selection process is set to... The subsequent selection angle in the second selection process is... The light intensity is projected onto the post-selection state; the post-selection process is as follows: Then, the second selection process is... ; The detection is performed using light intensity as the detection index, with an initial light intensity of... The reflection coefficient of the i-th weakly reflective element is The intensity of the light reflected by the i-th weakly reflective element received by the photodetector is The intensity of the light reflected by the i-th weakly reflective element received by photodetector two is In reality, the light intensity received by the photodetector is the sum of the light intensities reflected by all the weakly reflective elements. Therefore, the light intensity received by photodetector one is... The light intensity received by photodetector two is .

4. The distributed fiber optic grating sound source localization method based on weak measurement technology according to claim 1, characterized in that, Step S4 includes: through Obtain the attenuation coefficient corresponding to each weak reflection element. Based on the correspondence between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial location of the sound source is obtained through geometric calculation.

5. A distributed fiber optic grating sound source localization system based on weak measurement technology, characterized in that, include: Module M1: Construct a distributed fiber Bragg grating sensing platform based on weak measurement technology; Module M2: The weak reflection array is placed in the sound field. The weak reflection element is affected by the sound source signal, which changes the optical path and thus the phase. The light is received by the photodetector. Module M3: Performs a Fourier transform on the difference between the signals from photodetector one and photodetector two to calculate the phase corresponding to each weak reflection element; Module M4: Based on the correspondence 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: Locates the sound source by measuring the distance between the weak reflection element and the sound source; The module M3 includes: The acoustic signal is demodulated based on the phase change of the weak reflection element, and the light intensity received by photodetector one and photodetector two is used to obtain... By using Fourier transform, 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 volume of the sound received by each weak reflection element from the sound source is also different. Let be the attenuation coefficient from the sound source to the i-th weakly reflecting element. The sound source signal is ; The intensity of the light received by the photodetector. The intensity of the light received by photodetector two. The initial light intensity, To select the angle later, Phase difference; According to the photoelastic effect, Light and Time difference of light reaching the i-th weakly reflecting primitive In the middle, the position of the i-th weak reflection primitive starts from... Change to ,in In the formula For the effective photoelastic coefficient, Let be the distance between the (i-1)th weak reflection primitive and the ith weak reflection primitive. For time difference; by to obtain frequency ,neglect Size, ,in To delay the optical path of the fiber, The speed of light in an optical fiber. The central angular frequency of the light source is given; the vibration is derived. From phase transition Extracted from It has no impact on vibration detection. Substitute to get ;right After performing a fast Fourier transform, the frequency term is obtained. Phase Term and reflectivity Amplify reflectivity through weak measurement techniques Each weak reflection primitive has different Therefore, frequency Corresponding to each weak reflection primitive, signals from different weak reflection primitives are separated, thereby obtaining the signal corresponding to each weak reflection primitive. .

6. The distributed fiber optic grating sound source localization system based on weak measurement technology according to claim 5, characterized in that, The distributed fiber optic grating sensing platform includes: a light source (1), a pre-selection process (2), a fiber polarization beam splitter (3), an acousto-optic modulator (4), a delay fiber (5), and fiber 2.

1. Beam splitter (6), weak reflection array (7), fiber coupler (8), beam splitter (9), post-selection process one (10), photodetector one (11), post-selection process two (12), photodetector two (13) and computer (14). The light emitted by the light source (1) is modulated into a preset preselection state during the preselection process (2); after passing through the fiber polarization beam splitter (3), during the interaction process, the weak reflection array affected by the sound field is encoded into a time-varying phase by the acousto-optic modulator (4) and the delay fiber (5). Then through fiber optic 2 1. The beam splitter (6) reaches the weak reflection array (7); through the fiber coupler (8), the light in the fiber is converted into spatial light, and enters the post-selection process through the beam splitter (9). The angles between the first post-selection process (10) and the second post-selection process (12) and the first selection process are opposites. The two light intensities are received by photodetector 1 (11) and photodetector 2 (13) respectively, and the data is processed by the computer (14) to determine the location of the sound source.

7. The distributed fiber optic grating sound source localization system based on weak measurement technology according to claim 6, characterized in that, The module M2 includes: Module M2.1: Modulates the light output from the light source into a pre-selected state through a pre-selection process. ,in , Light is light that vibrates in the horizontal direction. Light is light that vibrates in a perpendicular direction; Module M2.2: The weak reflection array consists of Bragg gratings. Under the influence of the acoustic source signal, the optical path of the weak reflection element changes, and the result is encoded into a time-varying phase by an acousto-optic modulator and a delay fiber. ,interaction Represented as: ,in, The imaginary unit, It is a natural constant. For observable measurement of the system, After the interaction, the output light is in the following state: ; Light from the light source is pre-selected and divided into... Light and Light, After passing through the AOM and the time-delay fiber, the light is reflected in sequence by the weak reflection element and reaches the fiber coupler. The light is first reflected sequentially by weak reflection elements, then passes through a time-delay fiber and an AOM (Aspect-Oriented Fiber Optic Unit) before reaching the fiber coupler; the AOM is configured to... Angular frequency modulation, in When light passes by, ,exist When light passes by, ; Light and Since the light travels the same optical path, they arrive at the fiber coupler simultaneously. In a weakly reflective array, the i-th reflector reflects... The phase delay of light is expressed as , The phase of light traveling along the same path in opposite directions is represented as The phase difference between the two beams is ,in To delay the optical path of the fiber, This is the optical path from the 2×1 fiber beam splitter to the i-th weakly reflecting element. The speed of light in an optical fiber. The center angular frequency of the light source is determined by the delay fiber. Light first reaches the weakly reflective elementary element. The time difference between the light reaching the weakly reflecting elementary element is... ,exist Light and Time difference of light reaching the i-th weakly reflecting primitive In the middle, the position of the i-th weak reflection primitive starts from... Change to , Light phase change The phase difference is , This refers to the interaction process introduced by the weak reflector array. ; Module M2.3: After the light passes through the beam splitter, it will be in a post-selected state. The modulation is set to be within a preset orthogonal range to the previous selection state, and the post-selection angle of the first post-selection process is set to... The subsequent selection angle in the second selection process is... The light intensity is projected onto the post-selection state; the post-selection process is as follows: Then, the second selection process is... ; The detection is performed using light intensity as the detection index, with an initial light intensity of... The reflection coefficient of the i-th weakly reflective element is The intensity of the light reflected by the i-th weakly reflective element received by the photodetector is The intensity of the light reflected by the i-th weakly reflective element received by photodetector two is In reality, the light intensity received by the photodetector is the sum of the light intensities reflected by all the weakly reflective elements. Therefore, the light intensity received by photodetector one is... The light intensity received by photodetector two is .

8. The distributed fiber optic grating sound source localization system based on weak measurement technology according to claim 5, characterized in that, The module M4 includes: via Obtain the attenuation coefficient corresponding to each weak reflection element. Based on the correspondence between sound field attenuation and distance, the distance between each weak reflection element and the sound source is obtained, and the spatial location of the sound source is obtained through geometric calculation.

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