Photoacoustic sensing unit, acoustic signal detection device and acoustic signal detection method

Abstract

The invention discloses a photoacoustic sensing unit, an acoustic signal detection device and an acoustic signal detection method, and relates to the technical field of acoustic detection. The lower wrapping layer is arranged on the upper surface of the substrate, and a mounting groove is formed in the lower wrapping layer; the core layer is arranged in the mounting groove, the core layer comprises a straight waveguide and a circular waveguide, and a coupling distance is formed between the straight waveguide and the circular waveguide; the straight waveguide, the circular waveguide and the coupling space jointly form a light field regulation and control area; the exposed area covers the core layer and the lower wrapping layer, the exposed area comprises a groove, and the sensitive medium packaging layer is used for receiving sound pressure signals, generating corresponding deformation and transmitting the deformation to the core layer to cause the structure or state change of the light field regulation and control area, so that the effective refractive index of the circular waveguide is changed, and the sound pressure signal is generated. The change of the effective refractive index causes the drift of the harmonic peak wavelength, and the variation of the sound pressure signal is determined according to the displacement of the harmonic peak wavelength. The sensitivity of sound pressure detection is improved.

Description

Technical Field

[0001] This application relates to the field of acoustic detection technology, and in particular to photoacoustic sensing sensitive units, acoustic signal detection devices, and acoustic signal detection methods. Background Technology

[0002] Acoustic testing plays an irreplaceable role in fields such as non-destructive testing, acoustic microscopy, and medical imaging. Currently, acoustic sensors are mainly divided into two categories: electroacoustic sensors and photoacoustic sensors. Electroacoustic sensors suffer from drawbacks such as poor electromagnetic interference resistance, narrow response bandwidth, low sensitivity, and poor multiplexing capability; while photoacoustic sensors offer advantages such as strong electromagnetic interference resistance, high sensitivity, wide bandwidth, small size, and ease of integration.

[0003] Currently, most photoacoustic signal detection technologies based on Fabry-Pérot interferometers (FPI), polymer thin-film interferometers, fiber optic or grating FPI rely on strain variables of mechanical deformation to achieve acoustic signal sensing. This is prone to self-resonance, resulting in narrowed frequencies and making it difficult to meet the requirements of ultra-wideband and high-sensitivity acoustic signal detection.

[0004] Therefore, improving the accuracy of underwater acoustic signal detection is a problem that urgently needs to be solved. Summary of the Invention

[0005] The main objective of this application is to provide a photoacoustic sensing unit, an acoustic signal detection device, and an acoustic signal detection method, aiming to solve the technical problem of how to improve the accuracy of underwater acoustic signal detection.

[0006] To achieve the above objectives, this application proposes a photoacoustic sensing element, comprising: Substrate; A lower cladding layer is disposed on the upper surface of the substrate, and a mounting groove is provided in the lower cladding layer; A core layer is disposed within the mounting slot. The core layer includes a straight waveguide and a circular waveguide, with a coupling gap between the straight waveguide and the circular waveguide. The straight waveguide, the circular waveguide, and the coupling gap together constitute an optical field modulation region. A sensitive dielectric encapsulation layer covers the exposed areas of the core layer and the lower cladding layer. The exposed areas include grooves disposed on the upper surface of the core layer. The sensitive dielectric encapsulation layer is used to receive sound pressure signals and generate corresponding deformations, and transmits the deformations to the core layer, causing changes in the geometric structure or stress state of the optical field modulation region, thereby changing the effective refractive index of the circular waveguide. The change in effective refractive index is used to cause a shift in the wavelength of the resonant peak, and the change in the sound pressure signal is determined based on the shift in the wavelength of the resonant peak.

[0007] In one embodiment, the substrate is made of silicon; the lower cladding layer is made of silicon dioxide; and the sensitive medium encapsulation layer is made of polydimethylsiloxane, wherein the polydimethylsiloxane has a Young's modulus of less than 0.75 MPa and a Poisson's ratio of greater than 0.49.

[0008] In one embodiment, the deformation of the sensitive medium encapsulation layer under acoustic pressure acts on the circular waveguide, and the deformation synchronously changes the coupling distance between the straight waveguide and the circular waveguide to modulate the optical field coupling efficiency between the straight waveguide and the circular waveguide.

[0009] In one embodiment, without deformation, the width and height of the corresponding cross-sections of the straight waveguide and the circular waveguide are 6 μm and 6 μm respectively; the micro-ring radius of the circular waveguide is 0.8 cm, the coupling spacing is 4 μm; the thickness of the sensitive dielectric encapsulation layer is 0.5 μm; the groove includes a first groove and a second groove, the cross-sectional dimensions of the first groove 105 are 40 × 6 μm, and the cross-sectional dimensions of the second groove 106 are 20 × 6 μm.

[0010] Furthermore, to achieve the above objectives, this application also proposes an acoustic signal detection device, which includes: As described above, the photoacoustic sensing unit is used to receive the sound pressure signal and, under the action of the sound pressure signal, output the target light signal according to the received laser signal. A photoelectric signal synchronous acquisition device is optically connected to the photoacoustic sensing unit, and is used to emit laser signals to the photoacoustic sensing unit and receive the target light signal output by the photoacoustic sensing unit, and convert the target light signal into a digital signal. The host computer is communicatively connected to the photoelectric signal synchronous acquisition unit and is used to receive and process the digital signal to reconstruct the sound pressure information corresponding to the sound pressure signal.

[0011] In one embodiment, the photoelectric signal synchronous acquisition device includes: Laser module, used to generate laser signals; The photoelectric detection module is used to convert the target light signal output by the photoacoustic sensing unit into a current signal, and the current signal into a voltage signal, wherein the current signal is in the microampere level and the voltage signal is in the millivolt level; The signal acquisition module is used to amplify and filter the voltage signal, and convert the processed voltage signal into a digital signal.

[0012] In one embodiment, the photoelectric signal synchronization acquisition device further includes: The network communication module is used to transmit the digital signal to the host computer in real time; An isolation module is used to isolate a network communication module. The isolation module includes a communication signal isolation unit and a power isolation unit. The communication signal isolation unit is disposed at the front end of the communication interface of the network communication module and is used to electrically isolate the network communication signal. The power isolation unit is used to provide the network communication module with an independent power supply that is isolated from the main power supply.

[0013] Furthermore, to achieve the above objectives, this application also proposes a sound signal detection method, which is applied to the sound signal detection device described above, and the sound signal detection method includes: Control the photoelectric signal synchronous acquisition unit to emit laser signals; The photoacoustic sensing unit receives sound pressure signals and, under the influence of the sound pressure signals, outputs target light signals based on the received laser signals. The photoelectric signal synchronous acquisition device is controlled to receive the target optical signal and convert the target optical signal into a digital signal; Receive the digital signal output by the photoelectric signal synchronous acquisition unit; Based on a preset mapping relationship, sound pressure information corresponding to the sound pressure signal is reconstructed from the digital signal.

[0014] In one embodiment, the photoelectric signal synchronization collector includes a photoelectric detection module and an analog-to-digital converter; the step of controlling the photoelectric signal synchronization collector to receive a target optical signal and converting the target optical signal into a digital signal includes: The photoelectric detection module receives the target optical signal, converts the target optical signal into a current signal, and converts the current signal into a voltage signal, wherein the current signal is in the microampere range and the voltage signal is in the millivolt range. Based on the comparison between the effective value of the voltage signal and the preset threshold, the gain parameter is dynamically adjusted to obtain the voltage signal after gain adjustment. The analog-to-digital converter is controlled to sample and quantize the gain-adjusted voltage signal to obtain the original digital signal; The original digital signal is optimized by using a recursive least squares algorithm to obtain the processed digital signal.

[0015] In one embodiment, the step of reconstructing sound pressure information corresponding to the sound pressure signal based on the digital signal according to a preset mapping relationship includes: The digital signal is analyzed in the time and frequency domains to obtain characteristic parameters including the resonant wavelength shift and the change in light intensity. The feature parameters are calculated based on a preset mapping relationship to obtain preliminary sound pressure values; Environmental parameter compensation and noise suppression processing are performed on the preliminary sound pressure value to obtain the sound pressure information corresponding to the sound pressure signal.

[0016] One or more technical solutions proposed in this application have at least the following technical effects: An optical acoustic sensing sensitive unit includes: a substrate; a lower cladding layer disposed on the upper surface of the substrate, with a mounting groove within the lower cladding layer; a core layer disposed within the mounting groove, the core layer including a straight waveguide and a circular waveguide, with a coupling gap between the straight waveguide and the circular waveguide; the straight waveguide, the circular waveguide, and the coupling gap together constitute an optical field modulation region; a sensitive dielectric encapsulation layer covering the exposed areas of the core layer and the lower cladding layer, the exposed areas including grooves disposed on the upper surface of the core layer; the sensitive dielectric encapsulation layer is used to receive sound pressure signals and generate corresponding deformations, and transmits the deformations to the core layer, causing changes in the geometric structure or stress state of the optical field modulation region, thereby changing the effective refractive index of the circular waveguide, wherein the change in effective refractive index is used to cause a shift in the resonant peak wavelength, and the change in sound pressure signal is determined based on the shift in the resonant peak wavelength. An optical chip consisting of a substrate, a lower cladding layer, and a core layer containing a straight waveguide and a circular waveguide was designed and fabricated, and a polymer sensitive dielectric encapsulation layer with low Young's modulus and high Poisson's ratio was coated on it. By integrating acoustic sensing and optical detection, when an external sound pressure signal acts on the sensitive medium encapsulation layer, this flexible layer deforms. This deformation is directly transmitted to the underlying encapsulated core layer, specifically altering the micro-ring curvature of the circular waveguide and the nanometer-scale coupling distance between the straight and circular waveguides. Using flexible polymers such as PDMS as the direct sound sensing and force transmission medium, its low acoustic impedance enables efficient acoustic energy coupling with the air medium, while its low modulus amplifies weak sound pressure into more significant mechanical deformation. This mechanical deformation, through the combined effects of photoelasticity and waveguide mode coupling, is efficiently converted into a significant change in the effective refractive index of the circular waveguide, thereby greatly improving the sensitivity of sound pressure detection.

[0017] An acoustic signal detection device includes: the aforementioned photoacoustic sensing unit; the photoacoustic sensing unit receives a sound pressure signal and, under the influence of the sound pressure signal, outputs a target optical signal based on the received laser signal; a photoelectric signal synchronous acquisition unit, optically connected to the photoacoustic sensing unit, emits a laser signal to the photoacoustic sensing unit, receives the target optical signal output by the photoacoustic sensing unit, and converts the target optical signal into a digital signal; and a host computer, communicatively connected to the photoelectric signal synchronous acquisition unit, receives and processes the digital signal, and reconstructs the sound pressure information corresponding to the sound pressure signal. By constructing an integrated device in which the photoacoustic sensing unit, the photoelectric signal synchronous acquisition unit, and the host computer work together, the photoacoustic sensing unit modulates the sound pressure signal to be measured onto a laser carrier, fundamentally avoiding the problem of wire connections susceptible to electromagnetic interference in traditional electroacoustic sensing, and improving the reliability of the sensing end. The photoelectric signal synchronous acquisition unit integrates laser emission, photoelectric conversion, and signal conditioning. Its laser module provides stable excitation for the sensing unit, the photoelectric detection module efficiently converts weak light intensity modulation signals into electrical signals, and the signal acquisition module, through a professional amplification and filtering chain, ensures that microvolt-level acoustic signals can be digitized with a high signal-to-noise ratio, solving the problem of weak photoacoustic signal extraction and high-quality acquisition. The integrated isolation module effectively blocks the transmission of high-frequency noise and ground loop interference from external networks and internal switching power supplies to the sensitive analog front end through dual electrical isolation of network communication signals and power supply, greatly improving the stability and measurement accuracy of the entire system in complex electromagnetic environments. Finally, the host computer's real-time reception and software reconstruction of the digitized signal achieves complete recovery of sound pressure information. Through its integrated hardware design for synchronous optical calibration and acquisition, combined with rigorous internal isolation measures, this device achieves high acoustic detection sensitivity while possessing excellent anti-electromagnetic interference and long-term stable operation capabilities.

[0018] A method for detecting acoustic signals, applied to the aforementioned acoustic signal detection device, includes: controlling a photoelectric signal synchronous acquisition unit to emit a laser signal; controlling a photoacoustic sensing sensitive unit to receive a sound pressure signal, and under the action of the sound pressure signal, outputting a target optical signal based on the received laser signal; controlling the photoelectric signal synchronous acquisition unit to receive the target optical signal and converting the target optical signal into a digital signal; receiving the digital signal output by the photoelectric signal synchronous acquisition unit; and reconstructing the sound pressure information corresponding to the sound pressure signal based on a preset mapping relationship. This method uses a host computer to precisely control the photoelectric signal synchronous acquisition unit to emit a wavelength-stable laser signal, providing a clean and controllable optical probe for the subsequent sensing process. Furthermore, by controlling the photoacoustic sensing sensitive unit to be exposed to the sound field, and utilizing its unique sensitive medium encapsulation layer and micro-resonant waveguide structure, the weak sound pressure signal, which is difficult to directly acquire with high-quality electrical characteristics, is efficiently and linearly converted into a modulation of the laser resonant wavelength, i.e., the target optical signal. The problem of sound pressure measurement, which is susceptible to electromagnetic noise contamination, is transformed into a stable optical problem of precise distance measurement of light wavelength, fundamentally avoiding the electromagnetic sensitivity problem of traditional microphones in the signal pickup stage. Subsequently, a synchronous photoelectric signal acquisition unit is controlled to receive this modulated light signal simultaneously. Through its internally integrated low-noise photoelectric conversion chain and high-resolution analog-to-digital converter, the slightly varied light wavelength containing acoustic information is converted into a high-fidelity, interference-resistant digital signal. Finally, the host computer performs intelligent reconstruction of the digital signal based on the mapping relationship, decoding the sound pressure information that is proportional to the original physical sound pressure and has clear physical meaning, significantly improving the signal-to-noise ratio and sensitivity of weak sound signal detection. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort. The drawings are for illustrative purposes only, representing schematic diagrams rather than actual objects, and should not be construed as limiting this application. It is understandable that some well-known structures and their descriptions may be omitted in the drawings for those skilled in the art.

[0021] Figure 1 This is a cross-sectional schematic diagram of the photoacoustic sensing sensitive unit of this application; Figure 2 This is a schematic diagram of the structure of the photoacoustic sensing sensitive unit of this application; Figure 3 This is a schematic diagram of the hardware structure of the acoustic signal detection device of this application; Figure 4 This is a schematic diagram of the module structure of the acoustic signal detection device of this application; Figure 5 This is a flowchart illustrating the acoustic signal detection method of this application; Figure 6 The simulated resonant spectrum curve of the photoacoustic sensing unit in this application is shown. Figure 7 The image shows the simulated frequency response curve of the acoustic signal of the photoacoustic sensing sensitive unit in this application. Figure 8 The time-domain response curve of the acoustic signal detected by the acoustic signal detection device of this application at a frequency of 1MHz is shown in the figure. Figure 9 The frequency domain response curve of the acoustic signal detected by the acoustic signal detection device of this application at 1MHz is shown in the test graph.

[0022] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] This application provides a photoacoustic sensing unit, referring to... Figure 1 , Figure 1 This is a cross-sectional schematic diagram of the photoacoustic sensing sensitive unit of this application. Figure 2 This is a schematic diagram of the structure of the photoacoustic sensing sensitive unit of this application.

[0025] In the first embodiment, as Figure 1As shown, the photoacoustic sensing sensitive unit 10 includes a substrate 101, a lower cladding layer 102, a core layer 103, and a sensitive medium encapsulation layer 104. The lower cladding layer 102 is disposed on the upper surface of the substrate 101, and a mounting groove is provided within the lower cladding layer 102. The core layer 103 is disposed within the mounting groove, and the core layer 103 includes a straight waveguide 1031 and a circular waveguide, with a coupling gap between the straight waveguide 1031 and the circular waveguide. The straight waveguide 1031, the circular waveguide 1032, and the coupling gap together constitute the optical field modulation region. The sensitive medium encapsulation layer 104 covers the exposed areas of the core layer 103 and the lower cladding layer 102, and the exposed areas include grooves disposed on the upper surface of the core layer 103. The sensitive medium encapsulation layer 104 is used to receive the acoustic pressure signal and generate corresponding deformation, and transmits the deformation to the core layer 103, causing changes in the geometric structure or stress state of the optical field modulation region, thereby changing the effective refractive index of the circular waveguide 1032. The change in effective refractive index is used to cause a shift in the wavelength of the resonant peak, and the change in the acoustic pressure signal is determined based on the shift in the wavelength of the resonant peak.

[0026] Specifically, the substrate 101 is made of silicon; the lower cladding layer 102 is made of silicon dioxide; and the sensitive medium encapsulation layer 104 is made of polydimethylsiloxane (PDMS), which also serves as a sensing enhancement medium for efficient acoustic coupling. PDMS has a Young's modulus below 0.75 MPa and a Poisson's ratio above 0.49. Without deformation, the width and height of the corresponding cross-sections of the straight and circular waveguides are 6 μm and 6 μm respectively; the micro-ring radius of the circular waveguide is 0.8 cm, and the coupling spacing is 4 μm; the thickness of the sensitive medium encapsulation layer is 0.5 μm; the grooves include a first groove 105 and a second groove 106, with the first groove 105 having a cross-sectional dimension of 40 × 6 μm and the second groove 106 having a cross-sectional dimension of 20 × 6 μm. Among these, in the case of… Figure 2 From a top-down viewpoint, the first groove 105 has a size of 40×40μm, and the second groove 106 has a size of 20×20μm.

[0027] It should be noted that the deformation of the sensitive dielectric encapsulation layer 104 under acoustic pressure acts on the circular waveguide 1032. This deformation synchronously changes the coupling distance between the straight waveguide 1031 and the circular waveguide 1032, thereby modulating the optical field coupling efficiency between them. The micro-ring radius of the circular waveguide 1032 refers to... Figure 2 The radius of the entire circular waveguide 1032 from a top-down viewpoint.

[0028] The coupling spacing refers to the vertical distance between adjacent sidewalls of the straight waveguide 1031 and the circular waveguide 1032, and it determines the optical power exchange efficiency between them. When light of a specific wavelength propagates in the straight waveguide 1031, its evanescent field enters the circular waveguide 1032 through this coupling spacing, forming a ring resonance when the optical path length meets the resonance condition. For example, the sensitive dielectric encapsulation layer 104 can also be made of other polymers with low Young's modulus and high Poisson's ratio, such as polyurethane or hydrogel.

[0029] For example, substrate 101 provides mechanical support and functions as an integrated substrate. Its material is single-crystal silicon, and it can be either low-resistivity silicon or high-resistivity silicon with a resistivity in the range of 0.01-100 Ωcm. High-resistivity silicon helps reduce RF loss and is suitable for high-frequency applications. The lower cladding layer 102 is made of silicon dioxide and functions as a lower light field confinement layer. It uses mounting grooves within the lower cladding layer to position the core layer 103 structure. These mounting grooves can be formed using dry or wet etching processes. The core layer 103 is the core functional layer for light field transmission and control. It can be formed within the mounting grooves of the lower cladding layer 102 using micro / nano fabrication techniques, such as ultraviolet lithography or electron beam lithography combined with reactive ion etching. It is composed of straight waveguides 1031 and circular waveguides 1032 arranged in parallel with coupling spacing. The sensitive dielectric encapsulation layer 104 is directly responsible for receiving acoustic pressure signals. Under even slight acoustic pressure, the sensitive dielectric encapsulation layer 104 can undergo significant deformation, which is directly transmitted to the underlying core layer 103. This deformation alters the effective refractive index of the circular waveguide 1032 through strain and elasto-optic effects. The strain effect refers to the slight change in the physical dimensions of the waveguide, such as its perimeter and cross-sectional area; the elasto-optic effect refers to the change in the refractive index of the PDMS itself due to stress. The deformation also slightly perturbs the coupling spacing, thereby altering the efficiency of light entering the circular waveguide 1032 from the straight waveguide 1031.

[0030] In this embodiment, an optical chip consisting of a substrate, a lower cladding layer, and a core layer containing straight and circular waveguides was designed and fabricated, and a polymer sensitive medium encapsulation layer with low Young's modulus and high Poisson's ratio was coated on it. Acoustic sensing and optical detection are integrated. When an external sound pressure signal acts on the sensitive medium encapsulation layer, this flexible layer deforms, and this deformation is directly transmitted to the encapsulated core layer below, specifically simultaneously changing the micro-ring curvature of the circular waveguide and the nanometer-scale coupling distance between the straight and circular waveguides. Using flexible polymers such as PDMS as the direct sound sensing and force transmission medium, its low acoustic impedance characteristics enable efficient acoustic energy coupling with the air medium, while its low modulus characteristics amplify weak sound pressure into more significant mechanical deformation. This mechanical deformation, through the combined effects of photoelasticity and waveguide mode coupling, is efficiently converted into a significant change in the effective refractive index of the circular waveguide, thereby greatly improving the sensitivity of sound pressure detection.

[0031] In a second embodiment, this application provides an acoustic signal detection device, such as... Figure 3 As shown, the acoustic signal detection device includes a photoacoustic sensing unit 10, a photoelectric signal synchronous acquisition unit 20, and a host computer 30, as described in the first embodiment.

[0032] The photoacoustic sensing unit 10 receives the sound pressure signal and, under the influence of the sound pressure signal, outputs a target light signal based on the received laser signal. The photoelectric signal synchronous acquisition unit 20, optically connected to the photoacoustic sensing unit 10, emits a laser signal to the photoacoustic sensing unit 10 and receives the target light signal output by the photoacoustic sensing unit 10, converting the target light signal into a digital signal. The host computer 30, communicatively connected to the photoelectric signal synchronous acquisition unit 20, receives and processes the digital signal, reconstructing the sound pressure information corresponding to the sound pressure signal.

[0033] For example, the photoacoustic sensing unit 10 receives a sound pressure signal from the external environment and modulates the physical parameters of the laser signal transmitted inside it under the action of the sound pressure signal. The working process is as follows: the received laser signal is provided by the photoelectric signal synchronous acquisition unit 20 and enters the straight waveguide 1031 of the photoacoustic sensing unit 10; the sound pressure causes a change in the effective refractive index of the circular waveguide 1032, thereby causing a change in its resonance characteristics; finally, the photoacoustic sensing unit 10 outputs a target optical signal carrying sound pressure information, which can manifest as a change in light intensity or a drift in the resonant wavelength.

[0034] In one implementation, such as Figure 4 As shown, the photoelectric signal synchronous acquisition unit 20 includes a laser module 201, a photoelectric detection module 202, and a signal acquisition module 203. The laser module 201 generates a laser signal; the photoelectric detection module 202 converts the target light signal output from the photoacoustic sensing unit 10 into a current signal, and then converts the current signal into a voltage signal, wherein the current signal is in the microampere range and the voltage signal is in the millivolt range; the signal acquisition module 203 amplifies and filters the voltage signal, and then converts the processed voltage signal into a digital signal.

[0035] For example, the photoelectric signal synchronous acquisition unit 20 also includes a control module 204 for controlling the photoelectric detection module 202 and the signal acquisition module 203. The laser module 201 can use a distributed feedback laser or an external cavity tunable laser as an ultra-narrow linewidth tunable laser source to ensure the monochromaticity and frequency stability of the source. The photoelectric detection module 202 can include a photodetector and a transimpedance amplifier. The photodetector can be, for example, a PIN photodiode or an avalanche photodiode, to convert the optical signal into a weak current signal. The transimpedance amplifier linearly converts the current signal into a voltage signal. The signal acquisition module 203 can include a programmable gain amplifier, an analog-to-digital converter, and a digital signal processor or field-programmable gate array. The programmable gain amplifier is used to adaptively adjust the signal amplitude, the analog-to-digital converter is used for sampling and quantization, and the digital signal processor or field-programmable gate array is used to run digital filtering algorithms, such as recursive least squares algorithms, to finally obtain a digital signal.

[0036] The host computer 30 serves as the system's human-computer interaction and data terminal, used to complete the final analysis and presentation of information. It can exchange data with the photoelectric signal synchronous acquisition unit 20 through a communication connection. The host computer 30 includes display software. The homepage of the display software mainly includes real-time display of underwater acoustic signal waveforms and scatter plots drawn after calculating sensitivity, as well as parameter settings, data display, data storage, and digital filtering functions. Before displaying, the software will first check the device connection status of the sensor and the synchronous acquisition unit and provide a prompt. After successful connection, the acquired signal waveform will be automatically displayed. The historical playback function requires the user to select the data they want to view, which will then recall the selected underwater acoustic signal. The waveform amplitude and time base size are adjustable. The data analysis function can perform calculations and analyses on the selected data, and further visualize the broadband sensitivity of the underwater acoustic signal using parameter settings. It also provides a digitally filtered time-frequency envelope diagram to further filter out noise and display signal characteristics.

[0037] In one implementation, reference Figure 4 The photoelectric signal synchronous acquisition unit 20 also includes a network communication module 205 and an isolation module 206. The network communication module 205 transmits digital signals to the host computer 30 in real time; the isolation module 206 isolates the network communication module 205. Specifically, the isolation module 206 includes a communication signal isolation unit and a power isolation unit. The communication signal isolation unit is located at the front end of the communication interface of the network communication module 205 and is used to electrically isolate the network communication signals. The power isolation unit provides the network communication module 205 with an independent power supply isolated from the main power supply 207.

[0038] For example, the network communication module 205 is used to establish a digital data transmission channel, encapsulate the digital signals acquired and output into data frame formats conforming to standard network protocols, and realize real-time or near real-time transmission to the host computer 30. The physical implementation of the network communication module 205 can be an Ethernet physical layer chip with a media access controller, or a Wi-Fi module conforming to the IEEE 802.11 protocol, or other wired or wireless communication chips, depending on the specific requirements for transmission rate, latency, distance, and power consumption.

[0039] The isolation module 206 ensures the stability of the communication link in complex electromagnetic environments and prevents the conduction of potentially dangerous currents. It comprises two independent and complementary sub-units: a communication signal isolation unit and a power isolation unit. The communication signal isolation unit is positioned between the physical communication interface of the network communication module 205 and the internal controller, electrically creating a high-impedance isolation barrier. This barrier allows data signals to pass through but blocks DC components and common-mode interference. This can be achieved using a network transformer, which transmits differential signals via magnetic coupling while providing electrical isolation. The power isolation unit isolates the power supply path of the network communication module 205. Its necessity lies in the fact that even if the signal lines are isolated, interference can still couple through the power supply path if the power supply shares a common ground. The power isolation unit can be implemented using an isolated DC-DC power module, which integrates an isolation transformer to convert and isolate the main power supply 207 into an independent, floating power rail to power the network communication module 205. The isolation module 206 breaks the loop formed through the common ground wire, further enhancing the anti-interference capability and safety of the acoustic signal detection device.

[0040] In this embodiment, an integrated device is constructed, comprising a photoacoustic sensing unit, a photoelectric signal synchronous acquisition unit, and a host computer working collaboratively. The photoacoustic sensing unit modulates the sound pressure signal to be measured onto a laser carrier, fundamentally avoiding the electromagnetic interference-prone wire connection problems of traditional electroacoustic sensing, thus improving the reliability of the sensing end. The photoelectric signal synchronous acquisition unit integrates laser emission, photoelectric conversion, and signal conditioning. Its laser module provides stable excitation for the sensing unit, the photoelectric detection module efficiently converts the weak light intensity modulation signal into an electrical signal, and the signal acquisition module, through a professional amplification and filtering chain, ensures that the microvolt-level acoustic signal can be digitized with a high signal-to-noise ratio, solving the problem of weak photoacoustic signal extraction and high-quality acquisition. The integrated isolation module effectively blocks the transmission of high-frequency noise and ground loop interference from external networks and internal switching power supplies to the sensitive analog front end through dual electrical isolation of network communication signals and power supply, greatly improving the working stability and measurement accuracy of the entire system in complex electromagnetic environments. Finally, the host computer's real-time reception and software reconstruction of the digitized signal achieves complete recovery of the sound pressure information. This device achieves high acoustic detection sensitivity while possessing excellent resistance to electromagnetic interference and long-term stable operation through a synchronized hardware design that integrates optical calibration and data acquisition, combined with robust internal isolation measures.

[0041] In the third embodiment, this application provides a method for detecting acoustic signals, which is applied to the acoustic signal detection device in the second embodiment and its implementation, such as... Figure 5 As shown, the acoustic signal detection method includes steps S10~S50, specifically: Step S10: Control the photoelectric signal synchronous acquisition device to emit laser signals.

[0042] It should be noted that the photoelectric signal synchronous acquisition unit includes a laser module, which can use a distributed feedback laser or an external cavity tunable laser to emit laser signals to ensure the monochromaticity and frequency stability of the light source.

[0043] Step S20: Control the photoacoustic sensing sensitive unit to receive the sound pressure signal, and under the action of the sound pressure signal, output the target light signal according to the received laser signal.

[0044] It should be noted that the photoacoustic sensing unit can refer to the first embodiment. It receives the physical sound pressure signal, converts sound energy into deformation through the deformation of the sensitive medium encapsulation layer, and converts the deformation into a change in the optical properties of the laser signal by modulating the effective refractive index and coupling distance of the optical field control region, thus generating the target optical signal and achieving the encoding of sound pressure into an optical signal. The sound pressure signal is the original physical quantity to be measured, i.e., the dynamic pressure change caused by underwater sound waves. The target optical signal is the optical signal output by the photoacoustic sensing unit, modulated by the sound pressure signal, in which the wavelength of a specific resonant peak in its spectrum has shifted proportionally to the sound pressure.

[0045] Step S30: Control the photoelectric signal synchronous acquisition device to receive the target light signal and convert the target light signal into a digital signal.

[0046] It should be noted that the digital signal is the final output obtained by the photoelectric signal synchronous acquisition device after processing the target optical signal. This signal can be a discrete data sequence that can be directly processed by the host computer and characterizes the wavelength position of the resonance peak or other spectral features.

[0047] Step S40: Receive the digital signal output by the photoelectric signal synchronous acquisition unit.

[0048] For example, the host computer can receive the digital signal output by the photoelectric signal synchronous acquisition device.

[0049] Step S50: Based on the preset mapping relationship, reconstruct the sound pressure information corresponding to the sound pressure signal from the digital signal.

[0050] It should be noted that the preset mapping relationship establishes a deterministic correspondence between digital signals and physical sound pressure information. The host computer uses the preset mapping relationship to analyze and calculate the received digital signals, identify the positions of spectral valleys and calculate their offset relative to the reference, thereby solving for the time-varying, quantized sound pressure waveform or sound pressure level, completing the transformation from signal to information.

[0051] In this embodiment, the host computer precisely controls the photoelectric signal synchronous acquisition unit to emit a wavelength-stable laser signal, providing a clean and controllable optical probe for the subsequent sensing process. Then, the photoacoustic sensing sensitive unit is exposed to the sound field, utilizing its unique sensitive medium encapsulation layer and micro-resonant waveguide structure to efficiently and linearly convert the weak sound pressure signal, which is difficult to directly acquire with high-quality electrical data, into a modulation of the laser resonant wavelength, i.e., the target light signal. This transforms the sound pressure measurement problem, which is susceptible to electromagnetic noise contamination, into a stable optical problem of precise distance measurement of light wavelength, fundamentally avoiding the electromagnetic sensitivity problem of traditional microphones in the signal pickup stage. Subsequently, the same photoelectric signal synchronous acquisition unit is controlled to synchronously receive this modulated light signal, and through its internally integrated low-noise photoelectric conversion chain and high-resolution analog-to-digital converter, the slightly varied light wavelength containing acoustic information is converted into a high-fidelity, interference-resistant digital signal. Ultimately, based on the mapping relationship, the host computer performs intelligent reconstruction of the digital signal, decoding sound pressure information that is proportional to the original physical sound pressure and has clear physical meaning, significantly improving the signal-to-noise ratio and sensitivity of weak sound signal detection.

[0052] Based on the above embodiments, in one implementation, the photoelectric signal synchronization acquisition device includes a photoelectric detection module and an analog-to-digital converter, and step S30 includes: Step S301: Control the photoelectric detection module to receive the target light signal, convert the target light signal into a current signal, and convert the current signal into a voltage signal.

[0053] The current signal is in the microampere level, and the voltage signal is in the millivolt level.

[0054] Step S302: Based on the comparison result between the effective value of the voltage signal and the preset threshold, the gain parameter is dynamically adjusted to obtain the voltage signal after gain adjustment.

[0055] For example, the amplifier gain coefficient can be adjusted based on the real-time comparison between the effective value of the voltage signal and a preset threshold. If the signal is too weak, i.e., below the preset threshold, the gain is increased to enhance the signal amplitude; if the signal is too strong, i.e., close to saturation, the gain is decreased to prevent distortion, thus achieving adaptive optimization of the signal amplitude.

[0056] Step S303: Control the analog-to-digital converter to sample and quantize the voltage signal after gain adjustment to obtain the original digital signal.

[0057] For example, a continuous analog voltage signal is discretized at a fixed sampling rate, and the voltage value at each sampling moment is converted into a discrete binary digital code to obtain the original digital signal.

[0058] Step S304: The original digital signal is optimized by using a recursive least squares algorithm to obtain the processed digital signal.

[0059] For example, the optimal filter parameters can be recursively calculated and updated based on the statistical properties of the original digital signal to minimize the sum of squared errors between the desired signal and the filter output signal, thereby effectively tracking the slow changes in the signal's statistical properties.

[0060] In this embodiment, after the target optical signal is efficiently converted into a primary electrical signal by the photoelectric detection module, instead of using the traditional fixed-gain amplification method, the gain parameter is dynamically adjusted based on the real-time comparison of the effective value of the voltage signal with a preset threshold. This adaptively adjusts the input signal, which may have large amplitude fluctuations, to the optimal quantization range of the analog-to-digital converter. This fundamentally solves the problem of insufficient resolution for weak signals or saturation distortion for strong signals caused by the wide dynamic range of the signal, ensuring high fidelity in the original digital signal acquisition stage. Subsequently, based on the original digital signal obtained by analog-to-digital conversion, a recursive least squares algorithm is further used for real-time optimization of the filtering parameters. This algorithm can quickly track and adapt to changes in the statistical characteristics of the signal and noise, dynamically calculate the optimal filtering coefficients, and thus perform precise adaptive filtering on the original digital signal. It effectively suppresses complex noise that changes with time or environment, while better preserving the transient characteristics of the sound pressure signal.

[0061] Based on the above embodiments, in one implementation, step S40 includes: Step S401: Perform time-domain and frequency-domain analysis on the digital signal to obtain characteristic parameters including the resonant wavelength drift and the light intensity change.

[0062] It should be noted that time-domain analysis can directly observe the change of signal amplitude over time, and is used to extract features such as pulse rise time and peak value. Frequency-domain analysis can convert the signal to the frequency domain through Fast Fourier Transform, and observe the distribution of its energy at different frequencies, which is used to identify the periodicity, resonant frequency, and noise components of the signal. Using them together aims to extract key feature parameters related to sound pressure levels from digital signals.

[0063] For example, the resonant wavelength shift, i.e., the change in wavelength, can be expressed as: The change in light intensity, i.e., the change in effective refractive index, can be expressed as: Specifically, the amount of change in wavelength Change in effective refractive index The relationship is represented as: in, Indicates the resonant wavelength before deformation. It represents the effective refractive index before deformation.

[0064] Step S402: Based on the preset mapping relationship, the feature parameters are calculated to obtain the preliminary sound pressure value.

[0065] For example, the preset mapping relationship can be based on the change in wavelength. Change in effective refractive index Relationship, change in light intensity With wavelength change The relationship and sensitivity calculation formula are determined, where the change in light intensity With wavelength change The relationship is represented as: Where Q is the sensor quality factor. This represents the change in sound pressure. It's understandable that a higher Q value results in a more significant change in light intensity for the same wavelength shift. The above formula defines... and The nonlinear response between them.

[0066] For example, the formula for calculating sensitivity S can be expressed as: Where T is the transmission spectrum of the resonator and P is the underwater sound pressure. S represents the slope of the transmission spectrum and is proportional to the quality factor Q of the resonator. The higher the Q factor, the higher the S value. It is the shift in resonant wavelength caused by the change in the effective refractive index of the resonator, representing the response to sound pressure.

[0067] Step S403: Perform environmental parameter compensation and noise suppression processing on the preliminary sound pressure value to obtain the sound pressure information corresponding to the sound pressure signal.

[0068] For example, environmental parameter compensation mainly compensates for the effects of factors such as temperature on the sensing core, such as the Young's modulus E and waveguide refractive index of the PDMS. These effects will change the basic parameters of the mapping relationship in step S402, such as... The compensation algorithm can dynamically correct the initial sound pressure value based on real-time monitored ambient temperature data. Digital filtering, such as adaptive filtering and wavelet denoising, can be used to filter out electrical noise, environmental vibration noise, etc. Optimization can be achieved by combining the sensor's inherent frequency response characteristics. The photoacoustic sensing element's response amplitude, encapsulation layer thickness, material density, and Young's modulus are affected by different frequency sound pressure levels; its theoretical response curve is expressed as follows:

[0069] Where h is the cladding thickness and f is the acoustic signal frequency. for Young's modulus For density.

[0070] In this embodiment, by performing time-frequency analysis on the digital signal, the core optical characteristic parameters modulated by sound pressure, namely the resonant wavelength drift and the light intensity change, are directly extracted, providing a theoretical basis for high-sensitivity extraction of sound pressure information from different dimensions. Subsequently, based on the precise mapping relationship established through rigorous system calibration and embedding the above physical relationships, the optical characteristic values ​​are converted into preliminary sound pressure values. This calibration process essentially determines the overall sensitivity of the system, ensuring the accuracy of the quantitative conversion. Finally, by introducing an environmental parameter compensation model and a noise suppression algorithm combined with the inherent frequency response characteristics of the sensor, system errors such as temperature drift and external interference are effectively overcome, significantly improving the signal-to-noise ratio and environmental robustness of the output sound pressure information.

[0071] Based on the third embodiment and its implementation described above, the experimental verification results corresponding to this application are as follows, specifically, Figure 6 and Figure 7 This is a simulation diagram of the photoacoustic sensing sensitive unit. Near-infrared laser light enters the straight waveguide through the input end and propagates via total internal reflection. When the light wave passes through the coupling region, due to the evanescent field effect, the straight waveguide and the ring waveguide achieve efficient coupling in the microgroove region. Part of the light field enters the ring waveguide. After the light circulates once in the resonant cavity, the light field in the ring will interfere with the light field directly transmitted through the straight waveguide. If the circumference of the ring is exactly an integer multiple of the laser wavelength, the light in the straight waveguide and the light in the ring waveguide will resonate, i.e., a resonance enhancement effect. Light that does not meet the resonance condition will be output from the output port of the straight waveguide. This cycle repeats, generating a strong light field within the resonant cavity. By fitting the changes in light intensity and power at the output and input ends, the fitting results are as follows: Figure 6 The image shows the resonant spectrum of the photoacoustic sensing unit, which reflects the localization capability of the light field and the energy conversion efficiency. The smaller the loss, the sharper the spectrum and the higher the energy conversion efficiency. The image also shows the energy response amplitude of the photoacoustic sensing unit at the resonant frequency, which is directly related to the sensitivity and the detection signal-to-noise ratio. The full width at half maximum (FWHM) represents the width of the line shape at half its maximum amplitude. Figure 7 This is a schematic diagram of the acoustic signal frequency response of the photoacoustic sensing unit. The resonant frequency of the sensing unit is mainly determined by the FP (Fabry–Pérot interferometer) resonant cavity effect. Figure 8 and Figure 9To construct an acoustic signal detection device, the time-domain and frequency-domain response results of the acoustic sensor after testing using acoustic signal detection methods are shown in the figures. To verify the performance of the photoacoustic sensing element and the acoustic signal detection device, the time-domain and frequency-domain responses of the photoacoustic sensing element to underwater acoustic signals at different frequencies were studied. During the experiment, the sinusoidal signal transmission frequency of the signal generator was determined, the amplitude of the sinusoidal signal output by the signal generator was set to a suitable value and used to drive the transducer, and the voltage signal responded by the photoacoustic sensing element was recorded. A spectrum analyzer was used to record the sensor's response value at the corresponding driving frequency. A relatively high frequency of 1MHz is selected here for demonstration. Figure 8 This corresponds to the time-domain response diagram of the acoustic signal detected by the acoustic signal detection device at a frequency of 1MHz. Figure 9 This corresponds to the frequency domain response diagram of the acoustic signal detected by the acoustic signal detection device at 1MHz.

[0072] In some embodiments, the host computer provided in this application may include: a memory, a processor, and a computer program stored on the memory and executable on the processor, the computer program being configured to implement the above-described acoustic signal detection method. Specifically, the processor may include, for example, a general-purpose microprocessor, an instruction set processor, and / or an associated chipset and / or a dedicated microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor may also include onboard memory for caching purposes. The processor may be a single processing unit or multiple processing units for performing different actions of the method flow according to the embodiments of this application.

[0073] Memory can be any medium capable of containing, storing, transmitting, propagating, or transmitting instructions. For example, memory can include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, instruments, or propagation media. Specific examples of memory include: magnetic storage devices such as magnetic tape or hard disk drives (HDDs); optical storage devices such as optical discs (CD-ROMs); and also random access memory (RAM) or flash memory; and / or wired / wireless communication links.

[0074] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application. Therefore, the scope of this application should not be limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A photoacoustic sensing unit, characterized in that, include: Substrate; A lower cladding layer is disposed on the upper surface of the substrate, and a mounting groove is provided in the lower cladding layer; A core layer is disposed within the mounting slot. The core layer includes a straight waveguide and a circular waveguide, with a coupling gap between the straight waveguide and the circular waveguide. The straight waveguide, the circular waveguide, and the coupling gap together constitute an optical field modulation region. A sensitive medium encapsulation layer covers the exposed areas of the core layer and the lower cladding layer, the exposed areas including grooves disposed on the upper surface of the core layer; The sensitive medium encapsulation layer is used to receive the acoustic pressure signal and generate corresponding deformation, and transmits the deformation to the core layer, causing changes in the geometric structure or stress state of the optical field modulation region, so as to change the effective refractive index of the circular waveguide. The change in effective refractive index is used to cause a shift in the wavelength of the resonance peak, and the change in the acoustic pressure signal is determined according to the amount of shift in the wavelength of the resonance peak.

2. The photoacoustic sensing unit according to claim 1, characterized in that, The substrate is made of silicon; the lower cladding layer is made of silicon dioxide; and the sensitive medium encapsulation layer is made of polydimethylsiloxane, wherein the polydimethylsiloxane has a Young's modulus of less than 0.75 MPa and a Poisson's ratio of greater than 0.

49.

3. The photoacoustic sensing unit according to claim 2, characterized in that, The deformation of the sensitive medium encapsulation layer under acoustic pressure acts on the circular waveguide, and the deformation synchronously changes the coupling distance between the straight waveguide and the circular waveguide to modulate the optical field coupling efficiency between the straight waveguide and the circular waveguide.

4. The photoacoustic sensing unit according to claim 1, characterized in that, Without deformation, the width and height of the corresponding cross sections of the straight waveguide and the circular waveguide are 6 μm and 6 μm respectively; the micro-ring radius of the circular waveguide is 0.8 cm and the coupling spacing is 4 μm; the thickness of the sensitive dielectric encapsulation layer is 0.5 μm; the groove includes a first groove and a second groove, the cross-sectional dimensions of the first groove 105 are 40 × 6 μm and the cross-sectional dimensions of the second groove 106 are 20 × 6 μm.

5. A sound signal detection device, characterized in that, The acoustic signal detection device includes: The photoacoustic sensing unit as described in any one of claims 1 to 4; the photoacoustic sensing unit is used to receive the sound pressure signal, and under the action of the sound pressure signal, output a target light signal according to the received laser signal; A photoelectric signal synchronous acquisition device is optically connected to the photoacoustic sensing unit, and is used to emit laser signals to the photoacoustic sensing unit and receive the target light signal output by the photoacoustic sensing unit, and convert the target light signal into a digital signal. The host computer is communicatively connected to the photoelectric signal synchronous acquisition unit and is used to receive and process the digital signal to reconstruct the sound pressure information corresponding to the sound pressure signal.

6. The acoustic signal detection device according to claim 5, characterized in that, The photoelectric signal synchronous acquisition device includes: Laser module, used to generate laser signals; The photoelectric detection module is used to convert the target light signal output by the photoacoustic sensing unit into a current signal, and the current signal into a voltage signal, wherein the current signal is in the microampere level and the voltage signal is in the millivolt level; The signal acquisition module is used to amplify and filter the voltage signal, and convert the processed voltage signal into a digital signal.

7. The acoustic signal detection device according to claim 6, characterized in that, The photoelectric signal synchronous acquisition device also includes: The network communication module is used to transmit the digital signal to the host computer in real time; An isolation module is used to isolate a network communication module. The isolation module includes a communication signal isolation unit and a power isolation unit. The communication signal isolation unit is disposed at the front end of the communication interface of the network communication module and is used to electrically isolate the network communication signal. The power isolation unit is used to provide the network communication module with an independent power supply that is isolated from the main power supply.

8. A method for detecting acoustic signals, characterized in that, The acoustic signal detection method is applied to the acoustic signal detection device as described in any one of claims 5 to 7, wherein the acoustic signal detection method comprises: Control the photoelectric signal synchronous acquisition unit to emit laser signals; The photoacoustic sensing unit receives sound pressure signals and, under the influence of the sound pressure signals, outputs target light signals based on the received laser signals. The photoelectric signal synchronous acquisition device is controlled to receive the target optical signal and convert the target optical signal into a digital signal; Receive the digital signal output by the photoelectric signal synchronous acquisition unit; Based on a preset mapping relationship, sound pressure information corresponding to the sound pressure signal is reconstructed from the digital signal.

9. The method according to claim 8, characterized in that, The photoelectric signal synchronous acquisition device includes a photoelectric detection module and an analog-to-digital converter; The step of controlling the photoelectric signal synchronous acquisition device to receive the target optical signal and converting the target optical signal into a digital signal includes: The photoelectric detection module receives the target optical signal, converts the target optical signal into a current signal, and converts the current signal into a voltage signal, wherein the current signal is in the microampere range and the voltage signal is in the millivolt range. Based on the comparison between the effective value of the voltage signal and the preset threshold, the gain parameter is dynamically adjusted to obtain the voltage signal after gain adjustment. The analog-to-digital converter is controlled to sample and quantize the gain-adjusted voltage signal to obtain the original digital signal; The original digital signal is optimized by using a recursive least squares algorithm to obtain the processed digital signal.

10. The method according to claim 8, characterized in that, The step of reconstructing sound pressure information corresponding to the sound pressure signal based on the digital signal according to the preset mapping relationship includes: The digital signal is analyzed in the time and frequency domains to obtain characteristic parameters including the resonant wavelength shift and the change in light intensity. The feature parameters are calculated based on a preset mapping relationship to obtain preliminary sound pressure values; Environmental parameter compensation and noise suppression processing are performed on the preliminary sound pressure value to obtain the sound pressure information corresponding to the sound pressure signal.

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