Hydrophone system based on optical frequency comb and PGC demodulation method

Abstract

The application relates to the technical field of acoustic signal sensing, and provides a hydrophone system based on an optical frequency comb and a PGC demodulation method, which comprises an optical frequency comb light source, a phase modulator, a wavelength division multiplexer, a fiber acoustic base array, a signal acquisition module and a PGC modulation and demodulation module. The present application adopts the optical frequency comb light source, utilizes the equal-frequency-interval multi-wavelength output of the optical frequency comb, and can precisely match the standard channel grid through the comb tooth interval, so that the characteristics of single-source generation avoid the synchronization problem of multiple lasers under the traditional wavelength division multiplexing system. In addition, the coherence between the comb teeth can also simplify the modulation and demodulation of signals. When the signal is modulated, one phase modulation signal can be used for optical frequency modulation of all input light signals; when the signal is demodulated, one group of mixing signals can be used for algorithm mixing processing of all channel signals of the fiber acoustic base array, so that the complexity of signal processing is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acoustic signal sensing, in particular to a hydrophone system based on an optical frequency comb and a PGC demodulation method. BACKGROUND

[0002] The optical fiber hydrophone can capture acoustic signals underwater, which is the cornerstone of optical fiber underwater acoustic detection. Compared with other types of optical fiber hydrophones, the interferometric optical fiber hydrophone has higher sensitivity and is widely used. The common interferometric optical fiber hydrophone is mainly in the Michelson interferometer structure. Since the light returns once in the interference arm, under the condition of the same structural parameters, the sensitivity of the acoustic pressure response is twice that of the Mach-Zehnder interferometer structure. In addition, the Michelson interferometer is often matched with a 45-degree Faraday rotating mirror as a reflector to realize an optical fiber interferometer with complete non-polarization characteristics, which can eliminate polarization fading and polarization-induced phase noise.

[0003] In addition to the change of polarization affecting the signal-to-noise ratio and phase difference of the interference signal, the initial phase change of the interferometer will also affect the interference signal. The initial phase of the interferometer is contained in the phase of the interference signal. When the initial phase of the interferometer changes randomly with the external environment, the signal-to-noise ratio of the interference signal will also fluctuate randomly, and even the signal will be completely hidden, which seriously affects the stability of the response of the optical fiber hydrophone to the acoustic signal. Signal detection technology is the key to realizing stable detection of the phase of the interferometer.

[0004] Phase carrier modulation and demodulation (PGC) has high detection capability for weak phase signals, strong anti-noise characteristics and good engineering applicability, and is a common means to realize stable detection of the phase change of the interferometer. Based on the PGC method, the received acoustic signal of a single hydrophone can be stably demodulated. However, in underwater detection applications, a single hydrophone has insufficient spatial coverage and is difficult to capture the azimuth information of the target. In addition, even if the sensitivity of a single hydrophone is high, it is easy to be overwhelmed by environmental noise, and the pickup ability of weak acoustic signals deteriorates rapidly. Therefore, when performing underwater detection, optical fiber hydrophones need to be combined into a sensing array to form a specific beam and obtain the necessary spatial gain and directivity. In a hydrophone array composed of a large number of elements, signal transmission is very complex. In order to perform a large number of independent signal transmissions in a limited channel, an effective signal transmission multiplexing technology must be used. SUMMARY

[0005] Therefore, it is necessary to provide a hydrophone system based on an optical frequency comb and a PGC demodulation method, which can reduce the number of required light sources and reduce the cost of the system.

[0006] A hydrophone system based on an optical frequency comb, comprising an optical frequency comb light source, a phase modulator, a demultiplexer, a fiber acoustic array, a signal acquisition module, and a PGC modulation and demodulation module.

[0007] The optical fiber acoustic array is composed of a plurality of optical fiber interferometric hydrophones;

[0008] The optical frequency comb light source outputs N monochromatic lights with equal frequency intervals, phase coherence and time synchronization to the phase modulator, the N monochromatic lights are uniformly modulated by the phase modulator to generate phase modulation light which is input to the wavelength division demultiplexer, the wavelength division demultiplexer separates the input light signal into N independent single wave light signals according to wavelength and inputs them to the optical fiber acoustic array, the phase modulation light forms interference light signal after passing through the optical fiber acoustic array, the optical fiber acoustic array converts the received underwater target radiated acoustic signal into interference light phase, the interference light signal is input to the signal acquisition module, the signal acquisition module converts the received signal into a digital signal and inputs it to the PGC modulation and demodulation module, and the PGC modulation and demodulation module demodulates the input digital signal to obtain a target acoustic signal.

[0009] In one of the embodiments, the center frequency of each channel of the wavelength division demultiplexer is accurately aligned with the frequency of the target comb tooth of the optical frequency comb light source, and the channel interval of the wavelength division demultiplexer is equal to the repetition frequency of the optical frequency comb light source.

[0010] In one of the embodiments, the modulation signal of the phase modulator is provided by the PGC modulation and demodulation module.

[0011] A PGC demodulation method for the above-mentioned optical frequency comb-based hydrophone system, the method comprising the following steps:

[0012] An optical frequency comb-based hydrophone system is constructed, which comprises an optical frequency comb light source, a phase modulator, a wavelength division demultiplexer, an optical fiber acoustic array, a signal acquisition module and a PGC modulation and demodulation module, and the optical fiber acoustic array is composed of a plurality of optical fiber interferometric hydrophones;

[0013] The PGC modulation and demodulation module provides a high-frequency modulation electrical signal to drive the phase modulator to modulate the N light signals of the optical frequency comb light source in phase;

[0014] The phase-modulated light signal is separated by the wavelength division demultiplexer to obtain N single wave light signals with different wavelengths;

[0015] The separated single wave light signals are input into each optical fiber interferometric hydrophone of the optical fiber acoustic array to generate interference signals of different wave division channels, the interference signals contain light phase changes caused by underwater target radiated acoustic signals, and the interference signals with target acoustic signals are output to the signal acquisition module;

[0016] The signal acquisition module converts the received signal into a digital signal and inputs it to the PGC modulation and demodulation module;

[0017] The PGC modulation and demodulation module synchronously processes two parallel branches of the input single-channel interference signal, the first branch of interference signal is mixed with the fundamental harmonic of the modulation signal and then low-pass filtered to generate channel one filtered signal, and the second branch of interference signal is mixed with the second harmonic of the modulation signal and then low-pass filtered to generate channel two filtered signal;

[0018] The arctangent operation is used on the two branches of filtered signals to obtain the sound disturbance signal corresponding to the current single channel;

[0019] The PGC demodulation is performed on the interference signals of N channels to obtain the sound disturbance signals of all channels.

[0020] In one of the embodiments, the PGC modulation and demodulation module provides a high-frequency modulation electrical signal to drive the phase modulator to perform phase modulation on the N optical signals of the optical frequency comb light source, including:

[0021] The PGC modulation and demodulation module generates a sinusoidal wave to drive the phase modulator, so that the phase modulator generates a carrier wave with a sinusoidal variation of phase size over time and the same frequency as the modulation signal;

[0022] The N optical signals of the optical frequency comb light source are subjected to the same phase modulation when passing through the phase modulator.

[0023] In one of the embodiments, the separated single-wave optical signals are input into the optical fiber interference hydrophones of the optical fiber acoustic array to generate interference signals of different wave division channels, including:

[0024] The separated single-wave optical signals are input into the optical fiber interference hydrophones of the optical fiber acoustic array to generate interference signals of different wave division channels, and the interference signals are:

[0025] ;

[0026] wherein, is a branch of interference signal; is the amplitude of the direct current component of the output interference light; is the amplitude of the alternating current component; is the phase difference generated by the modulation light source; is the phase difference generated by the external environment, the initial phase difference, and the phase difference generated by other factors; is the target signal to be measured;

[0027] ;

[0028] wherein, is the modulation depth; is the modulation frequency; is time.

[0029] In one embodiment, the PGC modulation and demodulation module divides the input single-channel interference signal into two parallel branches for synchronous processing, the first branch interference signal is mixed with the fundamental harmonic of the modulation signal, and then low-pass filtered to generate a channel one filtered signal, the second branch interference signal is mixed with the second harmonic of the modulation signal, and then low-pass filtered to generate a channel two filtered signal, including:

[0030] The PGC modulation and demodulation module divides the single-channel interference signal into two branches;

[0031] The first branch interference signal is mixed with the fundamental harmonic of the modulation signal:

[0032]

[0033] After mixing, low-pass filtering is performed to generate a channel one filtered signal:

[0034]

[0035] wherein, is the channel one filtered signal; is the Bessel function of the 0th order; is the Bessel function of the th order; is the sound disturbance signal containing the target signal to be measured and the sound disturbance signal affected by the external environment disturbance; is the Bessel function of the 1st order;

[0036] The second branch interference signal is mixed with the second harmonic of the modulation signal:

[0037]

[0038] After mixing, low-pass filtering is performed to generate a channel two filtered signal:

[0039]

[0040] wherein, is the channel two filtered signal; is the Bessel function of the th order.

[0041] In one embodiment, the arctangent operation is used on the two filtered signals to obtain the sound disturbance signal corresponding to the current single channel, including:

[0042] The arctangent operation is used on the two filtered signals to obtain the sound disturbance signal corresponding to the current single channel:

[0043] .

[0044] ​​In one of the embodiments, the arctangent operation is used on the two filtered signals to obtain the sound disturbance signal corresponding to the current single channel, and further comprising:

[0045] The frequency component of the interference signal is acquired in real time Value:

[0046] ;

[0047] ;

[0048] ;

[0049] Wherein, The signal component with the frequency of ; The signal component with the frequency of ; C The value is obtained according to the ratio of the arctangent function.

[0050] In one of the embodiments, further comprising:

[0051] The channel disturbance signal corresponding to the current single channel is subjected to high-pass filtering to obtain the target signal .

[0052] The above-mentioned hydrophone system and PGC demodulation method based on optical frequency comb can avoid the synchronization problem of multiple lasers in the traditional wavelength division multiplexing system by using the optical frequency comb light source, utilizing the equal frequency interval multi-wavelength output of the optical frequency comb, and precisely matching the standard channel grid with the comb tooth interval. In addition, the coherence between the comb teeth can also simplify the modulation and demodulation of the signal. When the signal is modulated, one phase modulation signal can be used to perform optical frequency modulation on all input optical signals. When the signal is demodulated, a group of mixing signals can be used to perform algorithm mixing processing on all channel signals of the fiber acoustic array, which greatly reduces the complexity of signal processing.

[0053] The present application uses an optical frequency comb as a multi-wavelength laser instead of the traditional wavelength division multiplexing multi-laser scheme, reduces the number of required light sources, greatly reduces the system cost, and improves the space utilization. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is an application scenario diagram of the hydrophone system and PGC demodulation method based on optical frequency comb in one embodiment;

[0055] Figure 2 It is a flowchart of the PGC demodulation method in one embodiment;

[0056] Figure 3 ​A flowchart of an embodiment of an arctangent demodulation;

[0057] Figure 4 A structural diagram of an embodiment of an optical frequency comb based hydrophone system. DETAILED DESCRIPTION

[0058] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0059] The optical frequency comb based hydrophone system and the PGC demodulation method provided by the present application can be applied in an application environment as shown in Figure 1 The optical frequency comb based hydrophone system 104 receives the acoustic signal from the target 102.

[0060] In an embodiment, as shown in Figure 4 An optical frequency comb based hydrophone system is provided, which comprises an optical frequency comb light source, a phase modulator, a wavelength division demultiplexer, a fiber acoustic array, a signal acquisition module and a PGC modulation and demodulation module.

[0061] The fiber acoustic array is composed of a plurality of fiber interferometric hydrophones.

[0062] The optical frequency comb light source outputs N monochromatic lights with equal frequency intervals, phase coherence and time synchronization to the phase modulator. After being uniformly modulated by the phase modulator, the N monochromatic lights generate phase modulated light which is input to the wavelength division demultiplexer. The wavelength division demultiplexer separates the input light signal into N independent single wave light signals according to wavelength and inputs them to the fiber acoustic array. The phase modulated light forms an interference light signal after passing through the fiber acoustic array. The fiber acoustic array converts the received underwater target radiated acoustic signal into an interference light phase. The interference light signal is input to the signal acquisition module. After the received signal is converted into a digital signal, the digital signal is input to the PGC modulation and demodulation module. The PGC modulation and demodulation module demodulates the input digital signal to obtain the target acoustic signal.

[0063] In the above optical frequency comb based hydrophone system, by using the optical frequency comb light source, the equal frequency interval multi-wavelength output of the optical frequency comb, and the precise matching of the comb tooth interval to the standard channel grid, the characteristics of single source generation avoid the synchronization problem of multiple lasers under the traditional wavelength division multiplexing system. In addition, the coherence between the comb teeth can also simplify the modulation and demodulation of the signal. When the signal is modulated, one phase modulation signal can be used for optical frequency modulation of all input light signals. When the signal is demodulated, a group of mixing signals can be used for algorithm mixing processing of all channel signals of the fiber acoustic array, which greatly reduces the complexity of signal processing.

[0064] In one embodiment, the center frequency of each channel of the demultiplexer is accurately aligned with the frequency of the target comb tooth of the optical frequency comb light source, and the channel spacing of the demultiplexer is equal to the repetition frequency of the optical frequency comb light source.

[0065] In this embodiment, when the channel spacing is consistent with the repetition frequency, it can be ensured that each comb tooth falls into the corresponding channel to achieve accurate separation.

[0066] In one embodiment, the modulation signal of the phase modulator is provided by the PGC demodulation module.

[0067] In one embodiment, as shown in Figure 4 When the underwater target radiates acoustic signals, the acoustic signals act on the signal arm of the hydrophone to cause a change in the phase of the interference light.

[0068] In one embodiment, as shown in Figure 2 A PGC demodulation method is provided for the optical frequency comb-based hydrophone system in any of the above embodiments, the method comprising the following steps:

[0069] An optical frequency comb-based hydrophone system is constructed, including an optical frequency comb light source, a phase modulator, a demultiplexer, a fiber acoustic array, a signal acquisition module, and a PGC modulation and demodulation module. The fiber acoustic array is composed of a plurality of fiber interferometric hydrophones.

[0070] The PGC modulation and demodulation module provides a high-frequency modulation electrical signal to drive the phase modulator to modulate the N optical signals of the optical frequency comb light source.

[0071] The phase-modulated optical signals are separated by the demultiplexer to obtain N single-wave optical signals of different wavelengths.

[0072] The separated single-wave optical signals are input into each fiber interferometric hydrophone of the fiber acoustic array to generate interference signals of different wavelength channels. The interference signals contain changes in the phase of light caused by the acoustic signals radiated by the underwater target. The interference signals with the target acoustic signals are output to the signal acquisition module.

[0073] The signal acquisition module converts the received signals into digital signals and inputs them into the PGC modulation and demodulation module.

[0074] The PGC modulation and demodulation module processes the input single-channel interference signals in two parallel branches synchronously. The first branch of interference signals is mixed with the fundamental harmonic of the modulation signal and then low-pass filtered to generate channel one filtered signals. The second branch of interference signals is mixed with the second harmonic of the modulation signal and then low-pass filtered to generate channel two filtered signals.

[0075] The arctangent operation is performed on the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel.

[0076] PGC demodulation is performed on the N-channel interference signals to obtain the acoustic disturbance signals of all channels.

[0077] In this embodiment, the adjustment result is not affected by the drift of the working point of the interferometer, and the signal calculation of the multi-wave division channels can be completed in real time, and the coherence of the comb teeth of the optical frequency comb is used to improve the signal-to-noise ratio of the demodulated signal.

[0078] In one of the embodiments, the PGC modulation and demodulation module provides a high-frequency modulation electrical signal to drive the phase modulator to perform phase modulation on the N optical signals of the optical frequency comb light source, including:

[0079] The PGC modulation and demodulation module generates a sinusoidal wave to drive the phase modulator, so that the phase modulator generates a carrier wave with a sinusoidal variation of phase size over time and the same frequency as the modulation signal.

[0080] The N optical signals of the optical frequency comb light source are subjected to the same phase modulation when passing through the phase modulator.

[0081] In this embodiment, by sinusoidal modulation of the phase of the optical signal, a large-amplitude phase modulation carrier is generated in the unbalanced interferometer, and the weak acoustic signal is loaded on the large-amplitude, high-frequency carrier, which can avoid being submerged.

[0082] In one of the embodiments, the separated single-wave optical signals are input into each fiber interferometric hydrophone of the fiber acoustic array to generate interference signals of different wave division channels, including:

[0083] The separated single-wave optical signals are input into each fiber interferometric hydrophone of the fiber acoustic array to generate interference signals of different wave division channels, and the interference signals are:

[0084] ;

[0085] wherein, is one interference signal; is the amplitude of the direct current component of the output interference light; is the amplitude of the alternating current component; is the phase difference generated by the modulation light source; is the phase difference generated by the external environment, the initial phase difference, and the phase difference generated by other factors; is the target signal to be measured;

[0086] ;

[0087] wherein, is the modulation depth; is the modulation frequency; is time.

[0088] The target signal to be measured is brought into the interference signal, and can be expanded by Bessel function formula:

[0089] ;

[0090] .

[0091] In one embodiment, referring to Figure 3 , the PGC modulation and demodulation module divides the input single-channel interference signal into two parallel branches for synchronous processing. The first interference signal is mixed with the fundamental harmonic of the modulation signal, and then low-pass filtered to generate a channel one filtered signal. The second interference signal is mixed with the second harmonic of the modulation signal, and then low-pass filtered to generate a channel two filtered signal, including:

[0092] The PGC modulation and demodulation module divides the single-channel interference signal into two paths;

[0093] The first interference signal is mixed with the fundamental harmonic of the modulation signal:

[0094]

[0095] After mixing, low-pass filtering is performed to generate a channel one filtered signal:

[0096] ;

[0097] wherein, is the channel one filtered signal; is the Bessel function of the 0th order; is the Bessel function of the th order; is the sound disturbance signal containing the target signal to be measured and affected by external environmental disturbances; is the Bessel function of the 1st order;

[0098] The second interference signal is mixed with the second harmonic of the modulation signal:

[0099]

[0100] After mixing, low-pass filtering is performed to generate a channel two filtered signal:

[0101] ;

[0102] wherein, is the channel two filtered signal; is the Bessel function of the th order.

[0103] In this embodiment, the interference signal is divided into two paths, and is mixed with a one-fold frequency reference signal of the carrier and a double frequency reference signal mixing; due to the modulation frequency far greater than the frequency of the signal to be measured and its multiple, by low-pass filtering to filter out the signal containing and its multiple, to obtain a filtered signal.

[0104] In one embodiment, the inverse tangent operation is used on the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel, including:

[0105] The inverse tangent operation is used on the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel:

[0106] .

[0107] For the inverse tangent algorithm, when C = 2.63, , the detection amplitudes of the two channels are the same. Although the first derivative is 0 at the peak point, a slight fluctuation in the value of C has little effect on the stability of the demodulation signal, but for weak signals, the effect of C value drift cannot be ignored. Therefore, the actual system needs to obtain the value of C in real time to eliminate the influence of modulation depth.

[0108] In one embodiment, the inverse tangent operation is used on the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel, further comprising:

[0109] The value of C is obtained in real time by the frequency component of the interference signal:

[0110] ;

[0111] ;

[0112] ;

[0113] wherein, is the signal component with a frequency of ; is the signal component with a frequency of ; C The value of C is obtained according to the ratio of Bessel functions.

[0114] In this embodiment, the ratio of the two is unique to the ratio of Bessel functions of different orders of C value, so that the value of C can be obtained in real time. That is, the value of C can be obtained by the above formula.

[0115] In one embodiment, the inverse tangent operation is used on the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel, further comprising:

[0116] ​​The channel to-be-measured disturbance signal corresponding to the current single channel is processed by high-pass filtering to obtain a to-be-measured target signal .

[0117] Since the change of the initial phase of the interferometer is extremely slow compared with , the to-be-measured target signal can be obtained by processing the demodulated phase signal by high-pass filtering .

[0118] It should be understood that, although each step in the flowchart of Figure 2 is shown in sequence according to the arrow, these steps are not necessarily executed in sequence according to the arrow. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, Figure 2 at least part of the steps in may include multiple sub-steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these sub-steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least part of other steps or sub-steps or stages of other steps.

[0119] Each technical feature of the above embodiments can be combined arbitrarily, and in order to make the description simple, each technical feature in the above embodiments is not described in all possible combinations, however, as long as the combination of these technical features does not exist contradictory, it should be considered as the scope of the present application.

[0120] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the application. It should be pointed out that, for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A hydrophone system based on an optical frequency comb, characterized in that, It includes an optical frequency comb light source, a phase modulator, a wavelength division multiplexer, an optical fiber acoustic array, a signal acquisition module, and a PGC modulation and demodulation module; The fiber optic acoustic array is composed of multiple fiber optic interferometric hydrophones; The optical frequency comb light source outputs N monochromatic lights with equal frequency spacing, coherent phase, and synchronized time to the phase modulator. The N monochromatic lights are uniformly modulated by the phase modulator to generate phase modulated light, which is then input to the dewavelength division multiplexer. The dewavelength division multiplexer separates the input optical signal into N independent single-wavelength optical signals according to wavelength and inputs them to the fiber optic acoustic array. The separated single-wavelength optical signals are passed through the fiber optic acoustic array to form an interference optical signal. The fiber optic acoustic array converts the received underwater target radiated acoustic signal into the phase of the interference light. The interference optical signal is input to the signal acquisition module. The signal acquisition module converts the received signal into a digital signal and inputs it to the PGC modulation and demodulation module. The PGC modulation and demodulation module demodulates the input digital signal to obtain the target acoustic signal. The PGC modulation and demodulation module generates a sinusoidal wave to drive the phase modulator, so that the phase modulator generates a carrier whose phase magnitude changes sinusoidally with time and has the same frequency as the modulation signal; when the N optical signals of the optical frequency comb light source pass through the phase modulator, they are subjected to the same phase modulation. The PGC modulation and demodulation module divides the input single-channel interference signal into two parallel branches for synchronous processing. The first interference signal is mixed with the fundamental harmonic of the modulation signal and then low-pass filtered to generate the channel one filtered signal. The second interference signal is mixed with the second harmonic of the modulation signal and then low-pass filtered to generate the channel two filtered signal. The arctangent operation is applied to the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel.

2. The system according to claim 1, characterized in that, The center frequencies of each channel of the dewavelength division multiplexer are accurately aligned with the frequency of the target comb teeth of the optical frequency comb light source, and the channel spacing of the dewavelength division multiplexer is equal to the repetition frequency of the optical frequency comb light source.

3. The system according to claim 1, characterized in that, The modulation signal of the phase modulator is provided by the PGC modulation and demodulation module.

4. A PGC demodulation method, used in the system according to any one of claims 1 to 3, characterized in that, The method includes the following steps: A hydrophone system based on an optical frequency comb is constructed, including an optical frequency comb light source, a phase modulator, a wavelength division multiplexer, an optical fiber acoustic array, a signal acquisition module, and a PGC modulation and demodulation module. The optical fiber acoustic array is composed of multiple optical fiber interferometric hydrophones. The PGC modulation and demodulation module provides a high-frequency modulation electrical signal to drive a phase modulator to perform phase modulation on the N optical signals input from the optical frequency comb light source; The phase-modulated optical signal is separated by the dewavelength division multiplexer to obtain N single-wavelength optical signals of different wavelengths; The separated single-wavelength optical signal is input into each fiber interferometric hydrophone of the fiber acoustic array to generate interference signals with different wavelength division channels. The interference signal contains optical phase changes caused by underwater target radiated acoustic signals. The interference signal with target acoustic signals is output to the signal acquisition module. The signal acquisition module converts the received signal into a digital signal and then inputs it into the PGC modulation and demodulation module. The PGC modulation and demodulation module divides the input single-channel interference signal into two parallel branches for synchronous processing. The first interference signal is mixed with the fundamental harmonic of the modulation signal and then low-pass filtered to generate the channel one filtered signal. The second interference signal is mixed with the second harmonic of the modulation signal and then low-pass filtered to generate the channel two filtered signal. The arctangent operation is applied to the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel. PGC demodulation is performed on the interference signals of N channels to obtain the acoustic disturbance signals of all channels.

5. The method according to claim 4, characterized in that, The PGC modulation and demodulation module provides a high-frequency modulation electrical signal to drive a phase modulator to perform phase modulation on the N optical signals input from the optical frequency comb light source, including: The PGC modulation and demodulation module generates a sinusoidal wave to drive the phase modulator, so that the phase modulator generates a carrier whose phase magnitude changes sinusoidally with time and is at the same frequency as the modulation signal. When the N optical signals of the optical frequency comb light source pass through the phase modulator, they are subjected to the same phase modulation.

6. The method according to claim 4, characterized in that, The separated single-wavelength optical signals are input into each fiber interferometric hydrophone of the fiber acoustic array to generate interference signals in different wavelength division channels, including: The separated single-wavelength optical signal is input into each fiber interferometric hydrophone of the fiber acoustic array to generate interference signals in different wavelength division channels. The interference signals are: in, This is an interference signal; The amplitude of the DC component of the output interference light; For the amplitude of the AC component; The phase difference generated by the modulation light source; Phase difference caused by external environmental influences, initial phase difference, and phase difference caused by other factors; The signal of the target to be measured; in, Modulation depth; The modulation frequency; For time.

7. The method according to claim 6, characterized in that, The PGC modulation and demodulation module processes the input single-channel interference signal synchronously in two parallel branches. The first branch mixes the interference signal with the fundamental harmonic of the modulation signal and then performs a low-pass filter to generate the first-channel filtered signal. The second branch mixes the interference signal with the second harmonic of the modulation signal and then performs a low-pass filter to generate the second-channel filtered signal, including: The PGC modulation and demodulation module splits the single-channel interference signal into two paths. First-channel interference signal mixed with the fundamental harmonic of the modulation signal: After mixing and low-pass filtering, the channel 1 filtered signal is generated: in, This is the filtered signal for channel one; J 0 represents the 0th order Bessel function; J 2k For the 2nd k The Bessel function of order 1; It includes the target signal and the acoustic disturbance signal affected by external environmental disturbances; J 1 represents the first-order Bessel function; Second harmonic mixing of the second interference signal and the modulation signal: After mixing and low-pass filtering, a channel two filtered signal is generated: in, This is a channel two filtered signal; J 2k+1 For the 2nd k Bessel function of order +1.

8. The method according to claim 7, characterized in that, Applying arctangent calculation to the two filtered signals yields the acoustic disturbance signal corresponding to the current single channel, including: The arctangent operation is used to demodulate the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel: 。 9. The method according to claim 8, characterized in that, The arctangent operation is applied to the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel, which also includes: Real-time acquisition of frequency components of the interference signal value: in, For frequency The signal components; For frequency The signal components; C The value is derived by inversely from the ratio of the Bessel function.

10. The method according to claim 8, characterized in that, The arctangent operation is applied to the two filtered signals to obtain the acoustic disturbance signal corresponding to the current single channel, which also includes: The acoustic disturbance signal corresponding to the current single channel is subjected to high-pass filtering to obtain the target signal under test. .

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