Distributed optical fiber sound wave sensing system based on hardware demodulation

Abstract

The utility model relates to the technical field of optical fiber sensing, and provides a distributed optical fiber sound wave sensing system based on hardware demodulation, which comprises a laser, a first coupler, an acoustic optical modulator, a circulator, a second coupler, a photoelectric detector, at least two carrier frequency signal processing units and a field programmable gate array which are sequentially and optically connected, the acousto-optic modulator is optically connected with a first transmission end of the circulator, and a second transmission end of the circulator is used for being optically connected with a sensing optical fiber; the third output end of the circulator is connected with the second coupler, and the second coupler is connected with the first coupler; the second coupler is optically connected with the photoelectric detector; the carrier frequency signal processing unit comprises a hardware demodulation circuit and an analog-to-digital converter which are electrically connected. The hardware demodulation circuit carries out hardware filtering demodulation processing on the electric signals obtained through conversion, and the analog-to-digital converter carries out sampling on the data after filtering demodulation is completed, so that the requirement for the high sampling rate of hardware equipment is reduced, and the manufacturing cost of the system is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of optical fiber sensing technology, more particularly to a kind of distributed optical fiber acoustic wave sensing system based on hardware demodulation. BACKGROUND

[0002] With the development of communication technology, software demodulation technology has strong parallel processing capability. In a distributed optical fiber acoustic wave sensing system (DAS), through software demodulation technology, the DAS system can process multiple bandwidth data simultaneously. This parallel processing capability improves the efficiency of data transmission and the flexibility of the system. In particular, in the application scenarios of multiple carrier frequencies and linear sweep frequencies, software demodulation technology can effectively suppress fading noise, thereby improving the performance of the DAS system.

[0003] However, although software demodulation technology has many advantages, software demodulation technology has high requirements for sampling rate. In order to accurately capture and process multiple carrier frequencies and linear sweep signals, the hardware device must have high-speed and high-precision sampling capability, which increases the hardware cost of the entire DAS system. SUMMARY

[0004] The utility model aims at overcoming at least one defect (deficiency) of the above-mentioned prior art, and provides a distributed optical fiber acoustic wave sensing system based on hardware demodulation, to solve the problem of high sampling rate requirement of software demodulation technology in distributed optical fiber acoustic wave sensing system demodulation signal, which increases the hardware cost of the system.

[0005] The utility model takes the technical scheme, a kind of distributed optical fiber acoustic wave sensing system based on hardware demodulation, the distributed optical fiber acoustic wave sensing system includes laser, first coupler, acoustooptic modulator, circulator, second erbium-doped fiber amplifier, second coupler, photoelectric detector, field programmable gate array and at least two carrier frequency signal processing units;

[0006] Each of the carrier frequency signal processing units is connected between the photoelectric detector and the field programmable gate array.

[0007] Each of the carrier frequency signal processing units includes a hardware demodulation circuit and an analog-to-digital converter. The output of the hardware demodulation circuit is electrically connected to the input of the analog-to-digital converter.

[0008] The laser is optically connected with the input end of the first coupler, the first output end of the first coupler is optically connected with the input end of the acousto-optic modulator, the output end of the acousto-optic modulator is optically connected with the first transmission end of the circulator, and the second transmission end of the circulator is used for optical connection with a sensing optical fiber; the third transmission end of the circulator is optically connected with the first input end of the second coupler, the second input end of the second coupler is optically connected with the second output end of the first coupler; the first output end and the second output end of the second coupler are both optically connected with the input end of the photoelectric detector; the input end of the hardware demodulation circuit is electrically connected with the output end of the photoelectric detector; and the output end of the analog-to-digital converter is electrically connected with the field programmable gate array.

[0009] The optical signal is converted into an electrical signal by the photoelectric detector, a plurality of carrier frequency signal processing units are arranged, each carrier frequency signal processing unit can independently receive the signal from the photoelectric detector for filtering and demodulation at the same time, thereby improving the throughput of signal demodulation. In addition, parallel processing of multiple carrier frequency signal processing units can reduce the time pressure on a single processing path, so that a lower sampling rate analog-to-digital converter can be used to process the signal demodulated by each carrier frequency signal processing unit, thereby effectively reducing the hardware cost of the distributed optical fiber acoustic wave sensing system based on hardware demodulation.

[0010] Optionally, the carrier frequency signal processing unit further comprises a current-voltage conversion circuit and a filter circuit; the output end of the photoelectric detector is sequentially connected with the input end of the hardware demodulation circuit through the current-voltage conversion circuit and the filter circuit.

[0011] The signal converted by the current-voltage conversion circuit is filtered by the filter circuit, which can effectively remove the noise and interference components in the signal and improve the signal-to-noise ratio of the signal.

[0012] Optionally, a phase modulator is arranged between the first coupler and the acousto-optic modulator, the input end of the phase modulator is optically connected with the first output end of the first coupler, and the output end of the phase modulator is optically connected with the output end of the acousto-optic modulator.

[0013] Optionally, the distributed optical fiber acoustic wave sensing system further comprises an arrayed waveguide grating and a radio frequency amplifier connected with each other, the output end of the radio frequency amplifier is connected with another input end of the acousto-optic modulator; the arrayed waveguide grating is used for receiving a linear frequency modulation pulse signal and performing wavelength division multiplexing; and the radio frequency amplifier is used for amplifying the linear frequency modulation pulse signal processed by the arrayed waveguide grating and driving the acousto-optic modulator to modulate the frequency of the optical signal from the first coupler.

[0014] The arrayed waveguide grating receives a linear frequency modulation pulse signal, decomposes the linear frequency modulation pulse signal into a plurality of light signals of different wavelengths for multiplexing, thereby generating a continuous linear frequency modulation pulse signal; then a radio frequency amplifier amplifies the linear frequency modulation pulse signal and drives an acousto-optic modulator to modulate the light signal from the first coupler in frequency. Since the linear sweep signal can cover a wider frequency range, modulating the light signal by the radio frequency amplifier driving the acousto-optic modulator can reduce the fading noise at a specific frequency, thereby improving the signal-to-noise ratio of the signal.

[0015] Optionally, a first erbium-doped fiber amplifier is further arranged between the output end of the acousto-optic modulator and the first transmission end of the circulator, the input end of the first erbium-doped fiber amplifier is optically connected with the output end of the acousto-optic modulator, and the output end of the first erbium-doped fiber amplifier is optically connected with the first transmission end of the circulator; and / or, a second erbium-doped fiber amplifier is further arranged between the third transmission end of the circulator and the first input end of the second coupler, the input end of the second erbium-doped fiber amplifier is optically connected with the third transmission end of the circulator, and the output end of the second erbium-doped fiber amplifier is optically connected with the first input end of the second coupler.

[0016] The erbium-doped fiber amplifier enhances the intensity of the light signal during transmission, effectively compensates for the intensity loss of the light signal in the optical fiber due to factors such as attenuation and scattering, thereby improving the transmission quality and stability of the light signal.

[0017] Optionally, the splitting ratio of the first output end and the second output end of the second coupler is 50:50.

[0018] Optionally, the laser is a narrow linewidth laser.

[0019] Optionally, the photodetector is a balanced photodetector.

[0020] Optionally, the distributed optical fiber acoustic wave sensing system further comprises a laser driving circuit, one end of the laser driving circuit is electrically connected with the laser, and the other end of the laser driving circuit is connected with a power supply.

[0021] The laser driving circuit is used to drive the laser, and the laser driving circuit provides stable current and voltage for the laser, so that the laser can output laser signals more stably.

[0022] Optionally, the distributed optical fiber acoustic wave sensing system further comprises a thermoelectric cooler, and the thermoelectric cooler is used for heat exchange with the laser.

[0023] By contacting the thermoelectric refrigerator with the laser, the heat generated by the laser can be taken away or supplied to the laser using the refrigeration or heating function of the thermoelectric refrigerator, so that the working temperature of the laser can be controlled within a suitable range.

[0024] Compared with the prior art, the present application has the advantages of:

[0025] 1. The optical signal is converted into an electrical signal by the photoelectric detector, the converted electrical signal is subjected to hardware filtering and demodulation processing by the hardware demodulation circuit, and the data after the filtering and demodulation is sampled by the analog-to-digital converter, thereby reducing the requirement for high sampling rate of the ADC and reducing the manufacturing cost of the distributed optical fiber acoustic wave sensing system.

[0026] 2. The linear sweep signal and the multi-carrier frequency signal are added to the driving end, the linear sweep signal can cover a wider frequency range, and the fading noise at a specific frequency can be reduced, thereby improving the signal-to-noise ratio of the signal.

[0027] 3. The multiple carrier frequency signal processing units are connected in parallel, each carrier frequency signal processing unit can simultaneously and independently receive the signal from the photoelectric detector for filtering and demodulation processing, thereby improving the signal demodulation throughput of the distributed optical fiber acoustic wave sensing system and reducing the time pressure on the processing path of the single carrier frequency signal processing unit. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A structural schematic diagram of a specific embodiment of the distributed optical fiber acoustic wave sensing system based on hardware demodulation provided by the present application.

[0029] Figure 2 A structural schematic diagram of the carrier frequency signal processing unit of the distributed optical fiber acoustic wave sensing system based on hardware demodulation provided by the present application.

[0030] Figure 3 A structural schematic diagram of a second specific embodiment of the distributed optical fiber acoustic wave sensing system based on hardware demodulation provided by the present application.

[0031] Figure 4 A structural schematic diagram of a third specific embodiment of the distributed optical fiber acoustic wave sensing system based on hardware demodulation provided by the present application.

[0032] Figure 5 A structural schematic diagram of a fourth specific embodiment of the distributed optical fiber acoustic wave sensing system based on hardware demodulation provided by the present application. DETAILED DESCRIPTION

[0033] The drawings of the utility model are only used for example explanation, and can not be understood as the limitation of the utility model. In order to better illustrate the following embodiment, some components of the drawings can be omitted, enlarged or reduced, and the size of actual product is not represented;For those skilled in the art, it can be understood that some well-known structures and their description in the drawings can be omitted.

[0034] Embodiment 1

[0035] As Figure 1 The embodiment provides a distributed optical fiber acoustic wave sensing system based on hardware demodulation, which comprises a laser 1, a first coupler 2, an acousto-optic modulator AOM 3, a circulator 5, a second coupler 8, a photoelectric detector BAPD 9, a field programmable gate array FPGA 12 and at least two carrier frequency signal processing units 10, wherein each carrier frequency signal processing unit 10 is connected between the photoelectric detector BAPD 9 and the field programmable gate array FPGA 12.

[0036] As Figure 2 The carrier frequency signal processing unit 10 comprises a hardware demodulation circuit 102 and an analog-to-digital converter 104.

[0037] In the embodiment, the laser 1 is used to send laser to the first coupler 2, and the laser 1 can be a fiber laser or a semiconductor laser.

[0038] The laser 1 is optically connected with the input end of the first coupler 2, the first output end of the first coupler 2 is optically connected with the input end of the acousto-optic modulator AOM 3, the output end of the acousto-optic modulator AOM 3 is optically connected with the first transmission end of the circulator 5, and the second transmission end of the circulator 5 is used to be connected with a sensing optical fiber 6;The third transmission end of the circulator 5 is connected with the first input end of the second coupler 8, the second input end of the second coupler 8 is connected with the second output end of the first coupler 2;The first output end and the second output end of the second coupler 8 are both optically connected with the input end of the photoelectric detector BAPD 9;The input end of the hardware demodulation circuit 102 is electrically connected with the output end of the photoelectric detector BAPD 9, and the output end of the analog-to-digital converter 104 is electrically connected with the field programmable gate array FPGA 12.

[0039] In this embodiment, light emitted by the laser 1 passes through the first coupler 2 and enters the acousto-optic modulator AOM3 for frequency modulation to generate an optical signal containing multiple carrier frequencies. The optical signal with multiple carrier frequencies passes through the circulator 5 and enters the sensing fiber 6. After being disturbed by the acoustic wave in the sensing fiber 6, scattered light carrying acoustic wave information is generated. The scattered light is transmitted to the photodetector BAPD9 through the second coupler 8 and converted into an electrical signal. Each carrier signal processing unit 10 receives and processes electrical signals of different frequencies, realizing parallel demodulation of multi-carrier frequency data, thereby improving the demodulation efficiency of the system and the throughput of signal demodulation.

[0040] The optical signal is converted into an electrical signal using a photodetector BAPD9. The converted electrical signal is filtered and demodulated by a hardware demodulation circuit 102. The filtered and demodulated data is then sampled by an analog-to-digital converter 104, thereby reducing the requirement for a high ADC sampling rate. Furthermore, the parallel processing of multiple carrier signal processing units 10 reduces the time pressure on a single processing path, allowing the system to use a lower sampling rate analog-to-digital converter 104 to process the demodulated signal of each carrier signal processing unit 10, effectively reducing the system's hardware costs.

[0041] like Figure 3 As shown, in an optional embodiment, a first erbium-doped fiber amplifier EDFA4 can be arranged between the output end of the acousto-optic modulator AOM3 and the first transmission end of the circulator 5, the input end of the first erbium-doped fiber amplifier EDFA4 is optically connected to the output end of the acousto-optic modulator AOM3, and the output end of the first erbium-doped fiber amplifier EDFA4 is optically connected to the first transmission end of the circulator 3.

[0042] The first erbium-doped fiber amplifier EDFA4 is used to amplify the pulsed light and send it to the first transmission end of the circulator 5 .

[0043] Similarly, a second erbium-doped fiber amplifier EDFA7 can be arranged between the third transmission end of the circulator 5 and the first input end of the second coupler 8; the input end of the second erbium-doped fiber amplifier EDFA7 is optically connected to the third transmission end of the circulator 5, and the output end of the second erbium-doped fiber amplifier EDFA7 is optically connected to the first input end of the second coupler 8.

[0044] The acousto-optic modulator AOM3 is used to modulate the received laser light into pulse light and send it to the first erbium-doped fiber amplifier EDFA4.

[0045] The second erbium-doped fiber amplifier EDFA 7 is used to amplify the optical signal from the third transmission end of the circulator 5 and send it to the first coupler 2 .

[0046] The circulator 5 is used to send the amplified pulse light to the sensing fiber 6 to be tested through the second port, and is used to receive the optical signal generated by the sensing fiber 6 to be tested through the second transmission end and send it to the second erbium-doped fiber amplifier EDFA7 through the third transmission end.

[0047] The carrier signal processing unit 10 is used to filter the pulse light from the photodetector BAPD9 and demodulate the pulse light into an analog signal through hardware demodulation. Specifically, the carrier signal processing unit 10 includes a hardware demodulation circuit 102 and an analog-to-digital converter ADC 104 connected in sequence.

[0048] The photodetector BAPD9 is used to convert the optical signal transmitted from the first coupler 2 into a corresponding electrical signal.

[0049] The analog-to-digital converter ADC104 is used to convert the electrical signal from the photodetector BAPD9 into a digital signal, and send the converted digital signal to the field programmable gate array FPGA12.

[0050] The field programmable gate array FPGA12 is used to further process the digital signal converted by the analog-to-digital converter ADC104.

[0051] The intensity of the optical signal during transmission is enhanced by the first erbium-doped fiber amplifier EDFA4 and the second erbium-doped fiber amplifier EDFA7, which effectively compensates for the intensity loss of the optical signal in the optical fiber due to attenuation, scattering and other factors, thereby improving the transmission quality and stability of the optical signal.

[0052] like Figure 2 、 Figure 3 As shown, in this embodiment, each of the carrier signal processing units 10 further includes a current-voltage conversion circuit 106 and a filtering circuit 108; the output end of the photodetector BAPD9 is electrically connected to the input end of the hardware demodulation circuit 102 through the current-voltage conversion circuit 106 and the filtering circuit 108 in sequence.

[0053] Specifically, the input end of the current-voltage conversion circuit 106 is electrically connected to the output end of the photodetector BAPD9, and the output end of the current-voltage conversion circuit 106 is electrically connected to the input end of the filter circuit 108; the output end of the filter circuit 108 is electrically connected to the input end of the hardware demodulation circuit 102.

[0054] By filtering the signal converted by the current-voltage conversion circuit 106 through the filtering circuit 108 , noise and interference components in the signal can be effectively removed, thereby improving the signal-to-noise ratio of the signal.

[0055] An analog-to-digital converter ADC 104 is connected behind each carrier frequency signal processing unit 10, and the analog signal after demodulation is converted into a digital signal by the analog-to-digital converter ADC 104, and the converted digital signal is transmitted to the field programmable gate array FPGA 12 for further processing. Compared with using one analog-to-digital converter ADC 104 to process all the digital signals converted by the carrier frequency signal processing unit 10, the sampling rate requirement of a single analog-to-digital converter ADC 104 is reduced by setting an analog-to-digital converter ADC 104 behind each carrier frequency signal processing unit 10, and the analog-to-digital conversion efficiency of the distributed optical fiber acoustic wave sensing system based on hardware demodulation is also accelerated.

[0056] As shown in Figure 4 The phase modulator PM 23 is arranged between the first coupler 2 and the acousto-optic modulator AOM 3, and is used for phase modulating the optical signal from the first coupler 2 and transmitting the phase-modulated optical signal to the acousto-optic modulator AOM 3.

[0057] As shown in Figure 5 The distributed optical fiber acoustic wave sensing system based on hardware demodulation provided by the embodiment further comprises an arrayed waveguide grating AWG 341 and a radio frequency amplifier RFA 342 connected with each other, and an output end of the radio frequency amplifier RFA 342 is connected to another input end of the acousto-optic modulator AOM 3.

[0058] The arrayed waveguide grating AWG 341 is used for receiving the linear frequency modulation pulse signal and performing wavelength division multiplexing.

[0059] The radio frequency amplifier RFA 342 is used for amplifying the continuous linear frequency modulation pulse signal processed by the arrayed waveguide grating AWG 341 and driving the acousto-optic modulator AOM 3 to modulate the frequency of the optical signal from the first coupler 2, so as to realize linear sweep of the optical signal.

[0060] In a specific embodiment, the laser 1 can be a narrow linewidth laser 1. The photoelectric detector BAPD 9 is a balanced photoelectric detector. The splitting ratio of the first output end and the second output end of the first coupler 2 is 1:99. The splitting ratio of the second coupler 8 is 50:50.

[0061] In an alternative embodiment, the hardware demodulation-based distributed optical fiber acoustic wave sensing system provided in the embodiment further comprises a laser driver circuit (not shown in the figure), one end of the laser driver circuit is connected with the laser 1, and the other end of the laser driver circuit is connected with a power supply. The laser driver circuit is used for driving the laser 1, and the laser driver circuit adjusts the output wavelength of the laser 1 by controlling the current input into the laser 1. The laser driver circuit is used for driving the laser 1, and the laser driver circuit provides stable current and voltage for the laser 1, so that the laser 1 can more stably output laser signals.

[0062] In another alternative embodiment, the hardware demodulation-based distributed optical fiber acoustic wave sensing system provided in the embodiment further comprises a thermoelectric cooler (not shown in the figure), which is used for heat exchange with the laser 1. By contacting the thermoelectric cooler with the laser 1, the heat generated by the laser 1 can be taken away or heat can be provided to the laser 1 by using the cooling or heating function of the thermoelectric cooler, so that the working temperature of the laser 1 can be controlled within a suitable range.

[0063] In operation, the laser emitted by the laser 1 is transmitted to the first coupler 2, and then passes through the acousto-optic modulator AOM 3, which modulates the laser into pulsed light and transmits the pulsed light to the first erbium-doped fiber amplifier EDFA 4 for amplification. The amplified pulsed light is transmitted to the sensing optical fiber 6 through the first transmission end of the circulator 5 for testing, and the optical signal generated by the sensing optical fiber is returned through the third transmission end of the circulator 5 and amplified again by the second erbium-doped fiber amplifier EDFA 7. At the same time, the other output end of the first coupler 2 and the output end of the second erbium-doped fiber amplifier EDFA 7 are combined through the second coupler 8, and the combined optical signal is transmitted to the photodetector BAPD 9 to be converted into an electrical signal. The converted electrical signal is filtered and demodulated into an analog signal by the hardware demodulation circuit 102, and then converted into a digital signal by the analog-to-digital converter ADC 104 and transmitted to the field programmable gate array FPGA 12 for further processing.

[0064] The hardware demodulation-based distributed optical fiber acoustic wave sensing system of the utility model through hardware filter demodulation processing to the converted electrical signal by hardware demodulation circuit 102, through analog-to-digital converter ADC 104 to the data after filter demodulation sampling, thereby reduce the requirement of ADC high sampling rate, reduce the manufacturing cost of distributed optical fiber acoustic wave sensing system. By setting multiple carrier frequency signal processing units 10, each carrier frequency signal processing unit 10 can simultaneously and independently receive the signal from the photodetector BAPD 9 for filtering and demodulation processing, thereby improving the throughput of signal demodulation of the system and reducing the time pressure on the processing path of a single carrier frequency signal processing unit 10.

[0065] Obviously, the above embodiments of the present application are merely examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the specific implementation manners of the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application claims shall be included in the protection scope of the present application claims.

Claims

1. A distributed fiber optic acoustic wave sensing system based on hardware demodulation, characterized in that: The distributed fiber optic acoustic wave sensing system includes a laser, a first coupler, an acousto-optic modulator, a circulator, a second coupler, a photodetector, a field programmable gate array, and at least two carrier frequency signal processing units; Each of the carrier frequency signal processing units is connected between the photodetector and the field programmable gate array respectively; The carrier frequency signal processing unit includes a hardware demodulation circuit and an analog-to-digital converter; The output end of the hardware demodulation circuit is electrically connected to the input end of the analog-to-digital converter; The laser is optically connected to the input end of the first coupler, the first output end of the first coupler is optically connected to the input end of the acousto-optic modulator, the output end of the acousto-optic modulator is optically connected to the first transmission end of the circulator, and the second transmission end of the circulator is used to be optically connected to the sensing optical fiber; the third transmission end of the circulator is optically connected to the first input end of the second coupler, and the second input end of the second coupler is optically connected to the second output end of the first coupler; the first output end and the second output end of the second coupler are both optically connected to the input end of the photodetector; The input end of the hardware demodulation circuit is electrically connected to the output end of the photodetector; the output end of the analog-to-digital converter is electrically connected to the field programmable gate array.

2. A distributed fiber optic acoustic wave sensing system based on hardware demodulation according to claim 1, characterized in that: The carrier frequency signal processing unit also includes a current-voltage conversion circuit and a filtering circuit; The output end of the photodetector is electrically connected to the input end of the hardware demodulation circuit through the current-voltage conversion circuit and the filter circuit in sequence.

3. A distributed fiber optic acoustic wave sensing system based on hardware demodulation according to claim 2, characterized in that: A phase modulator is provided between the first coupler and the acousto-optic modulator, the input end of the phase modulator is optically connected to the first output end of the first coupler, and the output end of the phase modulator is optically connected to the output end of the acousto-optic modulator.

4. A distributed fiber optic acoustic wave sensing system based on hardware demodulation according to claim 2, characterized in that: The distributed fiber optic acoustic wave sensing system further includes an arrayed waveguide grating (AWG) and a radio frequency amplifier connected to each other, wherein the output end of the radio frequency amplifier is connected to the other input end of the acousto-optic modulator (AOM). The AWG is used to receive linear frequency modulated pulse signals and perform wavelength division multiplexing. The AOM is used to amplify the linear frequency modulated pulse signals processed by the AWG and drive the AOM to modulate the frequency of the optical signal from the first coupler.

5. The distributed optical fiber acoustic wave sensing system based on hardware demodulation according to claim 1, characterized in that: A first erbium-doped fiber amplifier is further provided between the output end of the acousto-optic modulator and the first transmission end of the circulator, the input end of the first erbium-doped fiber amplifier is optically connected to the output end of the acousto-optic modulator, and the output end of the first erbium-doped fiber amplifier is optically connected to the first transmission end of the circulator; And / or, a second erbium-doped fiber amplifier is further arranged between the third transmission end of the circulator and the first input end of the second coupler; the input end of the second erbium-doped fiber amplifier is optically connected to the third transmission end of the circulator, and the output end of the second erbium-doped fiber amplifier is optically connected to the first input end of the second coupler.

6. The distributed fiber optic acoustic wave sensing system based on hardware demodulation according to claim 1, characterized in that: The splitting ratio between the first output end and the second output end of the second coupler is 50:

50.

7. The distributed fiber optic acoustic wave sensing system based on hardware demodulation according to claim 1, characterized in that: The laser is a narrow linewidth laser.

8. The distributed fiber optic acoustic wave sensing system based on hardware demodulation according to claim 1, characterized in that: The photodetector is a balanced photodetector.

9. A distributed fiber optic acoustic wave sensing system based on hardware demodulation according to any one of claims 1 to 8, characterized in that: The distributed optical fiber acoustic wave sensing system further includes a laser driving circuit, one end of which is electrically connected to the laser, and the other end of which is connected to a power supply.

10. A distributed fiber optic acoustic wave sensing system based on hardware demodulation according to any one of claims 1 to 8, characterized in that: The distributed optical fiber acoustic wave sensing system further includes a thermoelectric cooler, which is used for performing heat exchange with the laser.

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