Distributed microphone array device based on ultra-weak fiber grating

Abstract

The application discloses a distributed microphone array device based on ultra-weak fiber grating, which comprises a fiber microphone array, an acousto-optic demodulation unit, and the fiber microphone is made by tightly winding an ultra-weak fiber grating sensor to a sound-sensitive structure of a thin-walled cylinder and covering the surface with an adhesive, and is used for acquiring a sound pressure signal; a plurality of fiber microphones are connected in series to form the fiber microphone array; the acousto-optic demodulation unit demodulates the phase change of the reflected light wave signal of the fiber microphone array to inversely calculate the sound pressure change; and a data processing and display unit processes and displays in real time the signal collected by the acousto-optic demodulation unit. The application uses a single optical fiber and a plurality of thin-walled cylinders to construct a series type distributed microphone sensing array based on the high sensitivity performance of the ultra-weak fiber grating microphone and the characteristics of the ultra-weak fiber grating, such as low reflectivity and high multiplexing capacity, and combines acousto-optic demodulation and data processing to realize the restoration of sound signals, thereby providing an effective scheme for distributed sound wave sensing.

Description

Technical Field

[0001] This invention relates to the field of acoustic sensing technology, specifically to a distributed microphone array device based on an ultra-weak fiber Bragg grating. Background Technology

[0002] Traditionally, electronic microphones are used to pick up sound signals. However, in actual measurements, microphones, due to their wide bandwidth, are susceptible to electromagnetic interference and inevitably affected by environmental noise, resulting in a significant decrease in the signal-to-noise ratio and thus affecting the sound signal. In recent years, the technology of picking up sound vibration signals along optical fibers has been widely used, and fiber optic microphones have become a research hotspot. Fiber optic microphones reconstruct the vibration waveform of sound signals by measuring various parameters such as phase, intensity, and frequency. Because they possess inherently strong resistance to electromagnetic interference, small size, simple design, high sensitivity, and the low loss, corrosion resistance, high temperature and high pressure resistance of optical fibers themselves, as well as being safe and reliable, they are suitable for picking up sound signals in various environments.

[0003] Currently, mainstream fiber optic microphones mainly include intensity-type fiber optic microphones and interferometric fiber optic microphones. Among them, intensity-type fiber optic microphones are affected by external sound pressure, which causes a change in the transmitted light intensity, thus reflecting the change in sound pressure.

[0004] The Chinese patent “A fiber optic microphone (patent number: ZL: 201010101144.8)” provides a light intensity modulation MEMS fiber optic microphone with high sensitivity, resistance to electromagnetic interference, and the ability to work in harsh environments. However, the microphone has a delicate and complex structure, is difficult to build, and has low sensitivity.

[0005] The Chinese patent "Fiber Optic Microphone with Laser Ring Cavity (Patent No.: ZL: 202010210103.6)" proposes a fiber optic microphone based on a laser ring cavity, utilizing the sensitive sensing function of a tunable fiber optic ring cavity. However, the fiber optic coil used for sound sensing in this microphone needs to be longer than 1 km, and its sensitivity is relatively low. In an interferometric fiber optic microphone, the phase of the optical signal in the transmission fiber is modulated by external sound pressure, causing a corresponding change. By constructing an interferometer, the phase change value of the optical signal is demodulated, and the sound signal is then retrieved.

[0006] The Chinese patent "Distributed Interferometric Fiber Optic Microphone Array Device Based on Spatial Division Multiplexing (Patent No.: ZL: 201010224955.7)" proposes a distributed array device for interferometric fiber optic microphones based on spatial division multiplexing. It uses red LEDs as the light source for fiber optic microphones, which is low in cost, has a simple light source driving circuit, and high stability. However, this device achieves data acquisition from multiple channels by switching optical switches, and cannot acquire data from multiple sensors simultaneously.

[0007] In summary, existing fiber optic microphones are complex in structure, costly, and the constructed microphone arrays are multi-channel single microphones with a limited number of channels. Therefore, constructing a single-channel multi-microphone array to achieve single-optical transceiver is of practical significance. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a distributed microphone array device based on an ultra-weak fiber optic grating. This device employs an ultra-weak fiber optic grating sensor and a thin-walled cylindrical acoustic enhancement structure to construct a highly sensitive fiber optic microphone. Furthermore, a large number of fiber optic microphones can be constructed on a single fiber, which not only greatly simplifies the structure but also reduces costs.

[0009] The technical solution adopted in this invention is as follows:

[0010] A distributed microphone array device based on ultra-weak fiber Bragg gratings includes:

[0011] The system includes an optical fiber microphone array, an acoustic-optical demodulation unit, and a data processing and display unit. The optical fiber microphone array is connected to the acoustic-optical demodulation unit, and the acoustic-optical demodulation unit is connected to the data processing and display unit.

[0012] The fiber optic microphone is made by tightly winding an ultra-weak fiber optic grating sensor onto a thin-walled cylinder and covering the surface with an adhesive, in order to acquire a highly sensitive sound pressure signal.

[0013] Multiple fiber optic microphones are connected in series to form a fiber optic microphone array for spatial distributed acoustic wave sensing; the acousto-optic demodulation unit demodulates the phase change of the reflected light wave signal from the fiber optic microphone array to invert the sound pressure change.

[0014] The data processing and display unit processes and displays the signals collected by the audio-visual demodulation unit in real time.

[0015] The acoustic sensitizing structure of the thin-walled cylinder includes a polycarbonate cylinder, and protective sleeves are fixed at both ends of the polycarbonate cylinder, wherein the polycarbonate cylinder and the protective sleeves are connected by an adhesive.

[0016] The polycarbonate cylinder is placed on a shock-absorbing sponge, which is used for sound absorption, that is, to absorb excess sound waves and improve the signal-to-noise ratio of the received sound.

[0017] The adhesive is an organosilicon sealant, applied to the surface of the ultra-weak fiber Bragg grating sensor and the thin-walled cylinder. This sealant is then attached to the microphone surface to fix and protect the optical fiber, with a thickness of 0.2mm to 0.4mm.

[0018] The ultra-weak fiber optic grating sensor is a single-mode fiber with high bending fatigue resistance and a grating spacing of 5m. The ultra-weak fiber optic grating sensor with a grating spacing of 5m is tightly wound onto the surface of a polycarbonate cylinder with an outer diameter of 20mm, a thickness of 0.5mm, and a length of 100mm. Protective sleeves are fixed at both ends, and the sensor is placed on shock-absorbing sponge. Silicone sealant is then applied to the surface of the fiber and the cylinder.

[0019] When an external sound signal is applied to the fiber optic microphone, the acoustic enhancement structure of the thin-walled cylinder undergoes a radial change, causing a change in the fiber length. This, in turn, generates a phase change between the two ultra-weak fiber gratings, achieving sound pressure-phase conversion. Optical emission generates optical pulse signals of a specific pulse width via a laser pulse generator. The acousto-optic demodulation unit includes optical emission, acquisition, and processing. The emitted pulsed light is reflected by the sensing grating and then interfered with to demodulate the phase change of the signal, converting it into an electrical signal for acquisition and processing.

[0020] The acousto-optic demodulation unit includes a laser pulse generator, a first circulator, a second circulator, a 3×3 coupler, a photoelectric converter, an A / D acquisition unit, and a processor module;

[0021] The output of the laser pulse generator is connected to the first output of the circulator. The first output of the first circulator is coupled to the input of the fiber optic microphone array. The second output of the first circulator is connected to the input of the second circulator. The first output of the second circulator is connected to the first input of the photoelectric converter. The input of the 3×3 coupler is coupled to the first output of the second circulator. The second output of the second circulator is directly connected to the first input of the photoelectric converter. The two outputs of the 3×3 coupler are connected to the second and third inputs of the photoelectric converter, respectively. The output of the photoelectric converter is connected to the input of the A / D acquisition unit. The output of the processor module is connected to the input of the laser pulse generator. The input of the processor module is connected to the output of the A / D acquisition unit.

[0022] The processor module adopts a combination of FPGA and ARM. The FPGA can realize high-speed A / D acquisition, high-speed signal transmission and parallel data processing, while the ARM has rich interface resources and low power consumption. Therefore, FPGA+ARM can greatly improve data processing performance, reduce cost and power consumption, and achieve better integration.

[0023] The 3×3 coupler performs distance compensation on the optical pulse to cause interference, thereby realizing the phase-intensity conversion of the acoustic signal to the optical signal.

[0024] The optical processing modulates the pulse width of the laser pulse by controlling the input of the laser pulse generator through the processor module, and acquires the sound information collected by the A / D converter.

[0025] The data processing and display unit includes a data processing section and a visualization display section;

[0026] The data processing section trains the received sound signal to obtain the required acoustic model, while the visualization section displays the processed results in real time via a PC.

[0027] The present invention relates to a distributed microphone array device based on an ultra-weak fiber Bragg grating, and its technical advantages are as follows:

[0028] 1) This invention uses an ultra-weak fiber optic grating sensor and a thin-walled cylindrical acoustic enhancement structure to make an optical fiber microphone, which has good acoustic enhancement effect, high sensitivity, low cost, simple structure and strong practicality.

[0029] 2) Multiple microphones can be built on a single optical fiber, breaking the limitations of building multi-channel microphone arrays and simplifying the device.

[0030] 3) It has good flexibility and can change the acoustic enhancement structure according to the characteristics of the target sound signal, thereby achieving efficient enhancement of different signals.

[0031] 4) Fast demodulation speed: FPGA is used for high-speed signal processing and phase demodulation. The device has a sampling rate of up to 33kHz, which meets the requirements for rapid acquisition of most audio signals.

[0032] 5) Based on the high sensitivity performance of ultra-weak fiber Bragg grating microphones and the low reflectivity and high multiplexing capability of ultra-weak fiber Bragg gratings, this invention constructs a series-type distributed microphone sensing array using a single optical fiber and multiple thin-walled cylinders. Combined with acousto-optic demodulation and data processing, it realizes the restoration of sound signals, providing an effective solution for distributed sound wave sensing. Attached Figure Description

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0034] Figure 1 This is a diagram of the distributed microphone array device based on ultra-weak fiber Bragg grating proposed in this invention.

[0035] Figure 2 This is a structural diagram of the ultra-weak fiber optic grating microphone proposed in this invention.

[0036] Figure 3 This is a structural diagram of the acousto-optic demodulation unit proposed in this invention.

[0037] Figure 4 The figure shows the test results of the sound pressure sensitivity of the ultra-weak fiber Bragg grating microphone proposed in this invention. Detailed Implementation

[0038] like Figure 1 As shown, a segmented acquisition device for a long-distance ultra-weak fiber optic grating array includes: a fiber optic microphone array 1, an acousto-optic demodulation unit 2, and a data processing and display unit 3. The fiber optic microphone array 1 is connected to the acousto-optic demodulation unit 2, and the acousto-optic demodulation unit 2 is connected to the data processing and display unit 3.

[0039] The fiber optic microphone is made by tightly winding an ultra-weak fiber optic grating sensor 11 onto a thin-walled cylinder to enhance sound sensitivity, and covering the surface with an adhesive layer, in order to acquire high-sensitivity sound pressure signals.

[0040] Multiple fiber optic microphones are connected in series to form a fiber optic microphone array 1, which is used for spatial distributed acoustic wave sensing; the acousto-optic demodulation unit 2 demodulates the phase change of the reflected light wave signal of the fiber optic microphone array 1 to invert the sound pressure change.

[0041] The data processing and display unit 3 processes and displays the signals collected by the audio-visual demodulation unit 2 in real time.

[0042] The fiber optic microphone array 1 is used to acquire sound signals. When the microphone receives a sound pressure signal, the phase of the optical pulse in the optical fiber changes. The acousto-optic demodulation unit 2 emits optical pulse signals with a specific pulse width; optical acquisition performs transmission, interference, and photoelectric conversion of the optical pulse signals; and optical processing controls the width of the emitted optical pulses and controls the A / D converter to acquire the converted electrical signals. The data processing and display unit 3 extracts data features and obtains relevant acoustic models through convolutional neural networks. Based on the acoustic models, it acquires information such as the type and location of the sound and displays the processing results in real time.

[0043] The fiber optic microphone structure of the fiber optic microphone array 1 is as follows: Figure 2 As shown, the fiber optic microphone array 1 consists of N (N is a natural number greater than or equal to 2) fiber optic microphones (m1, m2, ..., mN). Each fiber optic microphone is constructed based on an ultra-weak fiber optic grating sensor and a thin-walled cylindrical acoustic enhancement structure. The acoustic enhancement material is polycarbonate, and the optical fiber is a single-mode high-bending-fatigue-resistance optical fiber. The optical fiber is tightly wound around the thin-walled cylindrical acoustic enhancement structure to achieve acoustic enhancement. A layer of silicone sealant 15 is applied to the structure and the optical fiber to protect and fix the sensing optical fiber.

[0044] The characteristics of the distributed fiber optic microphone array based on ultra-weak fiber gratings are as follows: ①: Ultra-weak fiber grating sensors spaced 5m apart are used as acoustic sensing fibers; ②: Polycarbonate cylinders 12 are made of acoustic sensitizing material polycarbonate with an outer diameter of 20mm, a thickness of 0.5mm, and a length of 100mm to improve the sound pressure sensitivity of the microphone; ③: The low reflectivity and high multiplexing capacity of the ultra-weak fiber grating sensors are utilized to form a single-transmitter distributed serial microphone array.

[0045] The light emission of the acousto-optic demodulation unit 2 is realized by the output of the optical pulse signal through the laser pulse generator 21. The laser pulse generator 21 includes a laser, an SOA (Optical Signal Amplifier), and an EDFA (Electronic Optical Analyzer). The SOA is used to modulate the laser pulse width: 10ns to 50ns, and the EDFA is used to amplify the gain of the modulated optical signal, with a peak output power of 1000mW.

[0046] The optical acquisition of the acousto-optic demodulation unit 2 includes a first circulator 22, a second circulator 23, a 3×3 coupler 24, a photoelectric converter 25, and an A / D acquisition unit 26. The first circulator 22 is used to input the optical pulse signal into the fiber optic microphone array and output the reflected optical signal. After passing through the second circulator 23, the optical pulse is subjected to distance compensation in the 3×3 coupler 24 to cause interference, and is output in three equal phase difference paths. The photoelectric converter 25 converts the optical signal into an electrical signal and sends it to the A / D acquisition unit 26.

[0047] The optical processing of the acousto-optic demodulation unit 2 is achieved by the processor module 27 controlling the optical pulse width of the laser pulse generator 21 and controlling the A / D acquisition unit 26 to acquire data and store it in the ARM, and then uploading it to the host computer via Ethernet.

[0048] The data processing and display unit 3 includes a data processing section and a visualization display section. The data processing section trains the received sound signal to obtain the required acoustic model, and the visualization display section displays the processed results in real time via a PC.

[0049] Figure 4 The figure shows the test results of the sound pressure sensitivity of the ultra-weak fiber optic grating microphone proposed in this invention. The fiber optic microphone has a high sensitivity of 0.8691 rad / Pa (-121.222 dB rel nm / Pa), which meets the requirements of distributed sound wave sensing and lays the foundation for realizing distributed sound source localization.

[0050] The data processing method includes the following steps:

[0051] S1: An optical fiber microphone is made using an ultra-weak fiber optic grating sensor and an acoustic enhancement structure to acquire high-sensitivity sound signals, and an optical fiber microphone array 1 is constructed to realize distributed acoustic wave sensing.

[0052] S2: Perform feature analysis and extraction on the acquired sound signal to obtain the most obvious feature samples, and divide the training sample set and the test sample set.

[0053] S3: Use a convolutional neural network to train the feature training sample set to obtain the corresponding acoustic model.

[0054] S4: Input the test sample set into the acoustic model and obtain the results.

[0055] S5: Analyze and process the acquired results to obtain information such as the type and location of the sound.

[0056] Through the above implementation methods, a distributed fiber optic microphone array was constructed using an ultra-weak fiber optic grating sensor and an acoustic enhancement structure, realizing distributed acoustic sensing with single-light transmission and reception, improving sound sensitivity, and having significant application value in the field of sound monitoring.

Claims

1. A distributed microphone array device based on ultra-weak fiber Bragg gratings, characterized in that... include: Fiber optic microphone array (1), acoustic-optic demodulation unit (2), data processing and display unit (3), fiber optic microphone array (1) is connected to acoustic-optic demodulation unit (2), and acoustic-optic demodulation unit (2) is connected to data processing and display unit (3); The fiber optic microphone is made by tightly winding an ultra-weak fiber optic grating sensor (11) onto a thin-walled cylindrical acoustic enhancement structure and covering the surface with an adhesive, in order to obtain a high-sensitivity sound pressure signal. Multiple fiber optic microphones are connected in series to form a fiber optic microphone array (1) for spatial distributed acoustic wave sensing. The acoustic-optic demodulation unit (2) demodulates the phase change of the reflected light wave signal of the fiber optic microphone array (1) to invert the sound pressure change; The data processing and display unit (3) processes and displays the signals collected by the audio-visual demodulation unit (2) in real time; The acoustic enhancement structure of the thin-walled cylinder includes a polycarbonate cylinder (12) and protective sleeves (13) fixed at both ends of the polycarbonate cylinder (12). The polycarbonate cylinder (12) and the protective sleeves (13) are connected by an adhesive. The polycarbonate cylinder (12) is placed on a shock-absorbing sponge (14). The adhesive is an organosilicon sealant (15) which is applied to the surface of the ultra-weak fiber optic grating sensor (11) and the thin-walled cylinder.

2. The distributed microphone array device based on ultra-weak fiber Bragg gratings according to claim 1, characterized in that: The ultra-weak fiber optic grating sensor (11) is a single-mode fiber with high bending fatigue resistance and a grating spacing of 5m.

3. The distributed microphone array device based on ultra-weak fiber Bragg gratings according to claim 1, characterized in that: The acousto-optic demodulation unit (2) includes a laser pulse generator (21), a first circulator (22), a second circulator (23), a 3×3 coupler (24), a photoelectric converter (25), an A / D acquisition unit (26), and a processor module (27). The output of the laser pulse generator (21) is connected to the first output of the first circulator (22). The first output of the first circulator (22) is coupled to the input of the fiber optic microphone array (1). The second output of the first circulator (22) is connected to the input of the second circulator (23). The first output of the second circulator (23) is connected to the first input of the photoelectric converter (25). The input of the 3×3 coupler (24) is coupled to the first output of the second circulator (23). The second output of the second circulator (23) is directly connected to the first input of the photoelectric converter (25). The two outputs of the 3×3 coupler (24) are connected to the second and third inputs of the photoelectric converter (25), respectively. The output of the photoelectric converter (25) is connected to the input of the A / D acquisition unit (26). The output of the processor module (27) is connected to the input of the laser pulse generator (21). The input of the processor module (27) is connected to the output of the A / D acquisition unit (26).

4. The distributed microphone array device based on ultra-weak fiber Bragg gratings according to claim 3, characterized in that: The 3×3 coupler (24) performs distance compensation on the optical pulse to cause interference, thereby realizing the phase-intensity conversion of the acoustic signal to the optical signal.

5. The distributed microphone array device based on ultra-weak fiber Bragg grating according to claim 3, characterized in that: The processor module (27) controls the input terminal of the laser pulse generator (21) to modulate the pulse width of the laser pulse and acquire the sound information collected by the A / D acquisition unit (26).

6. The distributed microphone array device based on ultra-weak fiber Bragg grating according to claim 3, characterized in that: The data processing and display unit (3) includes a data processing part and a visualization display part; the data processing part trains the characteristics of the received sound signal to obtain the required acoustic model, and the visualization display part displays the processed results in real time through a PC.

7. A sound signal processing method based on the distributed microphone array device as described in any one of claims 1 to 6, characterized in that: When an external sound signal acts on the fiber optic microphone, the acoustic enhancement structure of the thin-walled cylinder will undergo radial changes, thereby causing changes in the fiber length, which in turn will generate a phase change between the two ultra-weak fiber gratings, realizing the conversion of sound pressure to phase; the light emission generates a light pulse signal with a specific pulse width through the laser pulse generator (21), and the acousto-optic demodulation unit (2) includes light emission, acquisition and processing. The emitted pulse light is reflected by the sensing grating and then interfered to demodulate the phase change of the signal, which is then converted into an electrical signal for acquisition and processing.

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