Noise suppression method and device and computer equipment

Abstract

The invention relates to a noise suppression method and device and computer equipment. The method comprises the following steps: outputting continuous coherent light through a laser; the continuous coherent light is separated into local oscillator light and modulated light through an optical fiber coupler; modulating the modulated light into double-sideband pulse light containing positive and negative sidebands through an electro-optical modulation device; injecting the double-sideband pulse light into a sensing optical fiber through an optical fiber circulator; the double-sideband pulse light is received through a sensing optical fiber, backward light is generated, and the backward light is guided to a polarization diversity receiving device through an optical fiber circulator; receiving the local oscillation light and the backward light through a polarization diversity receiving device, and outputting an interference signal; performing synchronous digital sampling on the interference signal through a data acquisition card to obtain a digital interference signal; phase noise is suppressed through phase noise reduction operation by the signal processing unit. By adopting the method, phase noise introduced by modulation frequency drift can be directly eliminated on a signal level, and the long-term stability of the system is enhanced.

Description

Technical Field

[0001] This application relates to the field of fiber optic sensing technology, and in particular to a noise suppression method, apparatus, and computer equipment. Background Technology

[0002] With the rapid development of fiber optic sensing technology, distributed fiber optic acoustic sensing technology has been widely used in key areas such as oil and gas pipeline safety monitoring, perimeter security, and earthquake monitoring due to its unique advantages of being resistant to electromagnetic interference, corrosion, and enabling long-distance distributed measurement.

[0003] In traditional technologies, distributed fiber optic acoustic wave sensing systems commonly employ a pulse heterodyne detection-based approach: a narrow-linewidth laser generates continuous coherent light, which is then modulated into pulses by an electro-optic modulator. This pulsed light is then injected into an optical array via optical components, and finally, a balanced photodetector detects the backlight. A signal processing unit demodulates the phase changes caused by the acoustic wave, thereby achieving acoustic signal sensing. This approach is currently the mainstream implementation path in the industry, and its core relies on the pulse modulation of the electro-optic modulator and the phase demodulation logic of the heterodyne detection technology.

[0004] However, traditional methods have significant technical drawbacks: First, they are highly sensitive to modulation frequency drift. Since the modulation frequency of the electro-optic modulator is provided by the radio frequency (RF) driver, factors such as temperature drift and aging of the RF driver can easily lead to instability in the modulation frequency. This frequency drift is directly converted into phase noise, significantly reducing the system's signal-to-noise ratio. Second, the system has poor long-term stability. The bias point of the electro-optic modulator drifts with temperature and time, causing changes in modulation depth and residual carrier leakage, introducing additional noise and affecting long-term operational reliability. Third, the hardware is costly and complex. To offset the effects of the drift, high-precision temperature control circuits, stable RF drivers, and complex bias point control circuits are required, significantly increasing the system's research and development and deployment costs. Summary of the Invention

[0005] Therefore, it is necessary to provide a noise suppression method, apparatus, or computer device that can reduce phase noise introduced by modulation frequency drift at the signal level, thereby improving the system's immunity to modulation frequency drift and enhancing the system's long-term stability without increasing hardware complexity, in order to address the aforementioned technical problems.

[0006] In a first aspect, this application provides a noise suppression method applied to a fiber optic acoustic wave sensing system, the fiber optic acoustic wave sensing system comprising a laser, a fiber optic coupler, an electro-optic modulation device, a sensing fiber, a fiber optic circulator, a polarization diversity receiver, a data acquisition card, and a signal processing unit, the method comprising:

[0007] The laser outputs continuous coherent light.

[0008] The continuous coherent light is separated into local oscillator light, which is directed to the local oscillator optical path, and modulated light, which is directed to the modulation optical path, through the fiber optic coupler.

[0009] The electro-optic modulation device modulates the modulated light into a double-sideband pulse light containing positive and negative sidebands;

[0010] The double-sideband pulsed light is injected into the sensing fiber through the fiber circulator;

[0011] The double-sideband pulse light is received through the sensing optical fiber and a backlight is generated. The backlight is then guided to the polarization diversity receiving device through the optical fiber circulator.

[0012] The polarization diversity receiver receives the local oscillator light and the backlight and outputs an interference signal.

[0013] The interference signal is synchronously digitally sampled using a data acquisition card to obtain a digital interference signal;

[0014] The digital interference signal is separated into positive and negative sidebands by a signal processing unit to obtain an upper sideband signal and a lower sideband signal. The upper sideband signal and the lower sideband signal are then polarized and combined to obtain an effective upper sideband interference signal and an effective lower sideband interference signal. The effective upper sideband interference signal and the effective lower sideband interference signal are then phase demodulated to obtain an upper sideband differential phase and a lower sideband differential phase. Phase noise reduction is performed on the upper sideband differential phase and the lower sideband differential phase to suppress phase noise introduced by modulation frequency drift.

[0015] In some embodiments of the method, the electro-optic modulation device includes an electro-optic modulator, a radio frequency driver, and a pulse generator. Modulating the modulated light into a double-sideband pulse light containing positive and negative sidebands using the electro-optic modulation device includes:

[0016] The electro-optic modulator is driven by the radio frequency driving source providing the radio frequency signal and the pulse generator providing the pulse width adjustable pulse signal, so that the electro-optic modulator operates in the carrier suppression state and modulates the continuous coherent light into a carrier-suppressed double-sideband pulse light containing positive and negative sidebands.

[0017] In some embodiments of the method, the electro-optic modulation device further includes an electro-optic modulation operating point controller, which includes a bias voltage source and a feedback control circuit. The step of modulating the modulated light into a double-sideband pulse light containing positive and negative sidebands via the electro-optic modulation device further includes:

[0018] The electro-optic modulation operating point controller monitors and controls the bias point of the electro-optic modulator through the bias voltage source and the feedback control circuit, so that the electro-optic modulator operates stably in the carrier suppression state.

[0019] In some embodiments of the method, the polarization diversity receiving device includes a polarization diversity coherent receiver, which includes a first polarization beamsplitter, a second polarization beamsplitter, a first optical 90° mixer, a second optical 90° mixer, a first balanced detector, a second balanced detector, a third balanced detector, and a fourth balanced detector. The step of receiving the local oscillator light and the backlight through the polarization diversity receiving device and outputting an interference signal includes:

[0020] Backlight with arbitrary polarization is input to the first polarization beam splitter and decomposed into horizontal polarization components and vertical polarization components; local oscillator light is input to the second polarization beam splitter and is simultaneously decomposed into horizontal polarization components and vertical polarization components, so as to achieve matching and separation of backlight and local oscillator light in polarization dimension.

[0021] The first optical 90° mixer is used to process the horizontal polarization channel, and its input terminal receives the horizontal polarization component of the backlight and the horizontal polarization component of the local oscillator light respectively; the second optical 90° mixer is used to process the vertical polarization channel, and its input terminal receives the vertical polarization component of the backlight and the vertical polarization component of the local oscillator light respectively.

[0022] The first or second optical 90° mixer internally includes cascaded fiber couplers and phase modulators, specifically including: two 1×2 fiber couplers in the first stage, used to split one input backlight and one local oscillator light into two paths respectively; two 2×2 fiber couplers in the second stage, used to cross-couple and interfere with the split backlight component and the local oscillator light component to achieve interference superposition of optical signals; and a 90° fixed phase shift is introduced in one of the interference optical paths through the phase modulator;

[0023] The four outputs of the first optical 90° mixer are connected to the first balanced detector and the second balanced detector, respectively generating in-phase and quadrature electrical signals for the horizontal polarization channel; the four outputs of the second optical 90° mixer are connected to the third balanced detector and the fourth balanced detector, respectively generating in-phase and quadrature electrical signals for the vertical polarization channel.

[0024] In some embodiments of the method, the step of separating the positive and negative sidebands of the digital interference signal using a signal processing unit to obtain an upper sideband signal and a lower sideband signal, performing polarization synthesis on the upper sideband signal and the lower sideband signal to obtain an effective upper sideband interference signal and an effective lower sideband interference signal, performing phase demodulation on the effective upper sideband interference signal and the effective lower sideband interference signal respectively to obtain an upper sideband differential phase and a lower sideband differential phase, and performing phase noise reduction operation on the upper sideband differential phase and the lower sideband differential phase to suppress phase noise introduced by modulation frequency drift through the phase noise reduction operation, includes:

[0025] The digital interference signal is filtered to separate the upper sideband signal with a positive radio frequency modulation frequency and the lower sideband signal with a negative radio frequency modulation frequency.

[0026] Polarization synthesis is performed by vector rotation or polarization filtering to construct effective interference signals in the upper and lower sidebands.

[0027] The instantaneous phases of the upper sideband effective interference signal and the lower sideband effective interference signal are calculated respectively. The instantaneous phases include the dynamic sensing phase introduced by the acoustic disturbance, the modulation frequency-related phase, and the laser center frequency-related phase.

[0028] The instantaneous phase of the effective interference signal in the upper sideband corresponding to two points at a preset sampling point interval is differentially divided with front and rear phases to obtain the differential phase of the upper sideband.

[0029] The instantaneous phases of the effective interference signals in the lower sideband corresponding to two points at a preset sampling point interval are differentially divided before and after to obtain the differential phase of the lower sideband.

[0030] In some embodiments of the method, the step of performing phase noise reduction operations on the upper sideband differential phase and the lower sideband differential phase to suppress phase noise introduced by modulation frequency drift includes:

[0031] The upper sideband differential phase and the lower sideband differential phase are subjected to phase summation and mean operation or phase difference and mean operation to make the modulation frequency related phases cancel each other out, so as to suppress the phase noise introduced by modulation frequency drift.

[0032] In some embodiments of the method, the polarization diversity receiving device includes a polarization diversity receiver and an acousto-optic frequency shifter, wherein the polarization diversity receiver includes a third polarization beamsplitter, a fourth polarization beamsplitter, two fiber optic couplers, and two balanced detectors;

[0033] The step of receiving the local oscillator light and the backlight through the polarization diversity receiver and outputting an interference signal includes:

[0034] Before injecting the double-sideband pulsed light output by the electro-optic modulation device into the sensing fiber through the fiber circulator, the acousto-optic frequency shifter is placed in the modulation optical path to shift the modulation light at a fixed frequency, thereby achieving frequency shift of the beat frequency signal.

[0035] Backlight with arbitrary polarization is input to the third polarization beam splitter and decomposed into horizontal polarization components and vertical polarization components; local oscillator light is input to the fourth polarization beam splitter and is simultaneously decomposed into horizontal polarization components and vertical polarization components, so as to achieve matching and separation of backlight and local oscillator light in polarization dimension.

[0036] Two 2×2 fiber couplers correspond to two orthogonal polarization state channels, which are used to cross-couple and interfere with the backlight component and the local oscillator component under the same polarization state to achieve interference superposition of optical signals; the four interference optical signals after coupling are input to two balanced detectors to generate interference electrical signals of horizontal polarization channel and vertical polarization channel, respectively.

[0037] In some embodiments of the method, the sensing fiber includes an ultra-weak reflection microstructure fiber array or a distributed fiber.

[0038] According to a second aspect of the present disclosure, a noise suppression device is provided, applied to a fiber optic acoustic wave sensing system. The fiber optic acoustic wave sensing system includes a laser, a fiber optic coupler, an electro-optic modulation device, a sensing fiber, a fiber optic circulator, a polarization diversity receiver, a data acquisition card, and a signal processing unit. The device includes:

[0039] A light source output module is used to output continuous coherent light via a laser;

[0040] The optical path splitting module is used to separate the continuous coherent light into two paths: local oscillator light, which is directed to the local oscillator optical path, and modulated light, which is directed to the modulation optical path, through an optical fiber coupler.

[0041] An electro-optic modulation module is used to modulate the modulated light into a double-sideband pulse light containing positive and negative sidebands using an electro-optic modulation device;

[0042] A pulsed light injection module is used to inject double-sideband pulsed light output from the electro-optic modulation device into the sensing optical fiber through the optical fiber circulator;

[0043] A sensing reflection module is used to receive the double-sideband pulse light through the sensing optical fiber and generate backlight, and guide the backlight to the polarization diversity receiving device through the optical fiber circulator.

[0044] The coherent receiving module is used to receive the local oscillator light and the backlight through the polarization diversity receiving device and output an interference signal;

[0045] The sampling module is used to synchronously digitize the interference signal through a data acquisition card to obtain a digital interference signal;

[0046] The signal processing module is used to separate the positive and negative sidebands of the digital interference signal through the signal processing unit to obtain an upper sideband signal and a lower sideband signal; to perform polarization synthesis on the upper sideband signal and the lower sideband signal to obtain an effective upper sideband interference signal and an effective lower sideband interference signal; to perform phase demodulation on the effective upper sideband interference signal and the effective lower sideband interference signal to obtain an upper sideband differential phase and a lower sideband differential phase respectively; and to perform phase noise reduction operation on the upper sideband differential phase and the lower sideband differential phase to suppress the phase noise introduced by modulation frequency drift.

[0047] According to a third aspect of the present disclosure, a computer device is provided. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the noise suppression method described above.

[0048] According to a fourth aspect of the present disclosure, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements the noise suppression method described above.

[0049] According to a fifth aspect of the present disclosure, a computer program product is provided. The computer program product includes a computer program that, when executed by a processor, implements the noise suppression method described above.

[0050] The noise suppression scheme provided in this application adopts a carrier-suppressed double-sideband modulation method to modulate continuous light into double-sideband pulse light containing both positive and negative sidebands. By utilizing the opposite response characteristics of the positive and negative sidebands to modulation frequency noise during interference, the phase noise introduced by modulation frequency drift is directly eliminated at the signal level through positive and negative sideband multiplexing and phase noise reduction calculation. This eliminates the need for additional complex hardware, significantly improves the system's immunity to modulation frequency drift, enhances the long-term stability of the system, reduces the cost and complexity of hardware configuration, and makes the system more practical in actual engineering applications.

[0051] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0052] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure, and are not intended to unduly limit this disclosure.

[0053] Figure 1 This is a structural block diagram of an optical fiber acoustic wave sensing system according to an exemplary embodiment;

[0054] Figure 2 This is a schematic flowchart illustrating a noise suppression method according to an exemplary embodiment;

[0055] Figure 3 This is a structural block diagram of an optical fiber acoustic wave sensing system according to another exemplary embodiment;

[0056] Figure 4 This is a specific structural block diagram of an optical fiber acoustic wave sensing system according to another exemplary embodiment;

[0057] Figure 5 This is a structural block diagram of an optical fiber acoustic wave sensing system employing an acousto-optic frequency shifter and a polarization diversity receiver, according to an exemplary embodiment.

[0058] Figure 6 This is a structural block diagram of an optical fiber acoustic wave sensing system employing an acousto-optic frequency shifter and a polarization diversity receiver, according to another exemplary embodiment.

[0059] Figure 7 This is a structural block diagram of a polarization diversity coherent receiver according to an exemplary embodiment;

[0060] Figure 8 This is a structural block diagram of a polarization diversity receiver according to an exemplary embodiment;

[0061] Figure 9 This is a structural block diagram of a noise suppression device according to an exemplary embodiment;

[0062] Figure 10 This is a diagram illustrating the internal structure of a computer device according to an exemplary embodiment.

[0063] Reference numerals: 101, laser; 102, electro-optic modulation device; 1021, electro-optic modulator; 1022, radio frequency driver; 1023, pulse generator; 1024, electro-optic modulation operating point controller; 103, sensing fiber; 104, polarization diversity receiver; 105, data acquisition card; 106, signal processing unit; 107, fiber coupler; 108, fiber optic circulator; 109, erbium-doped fiber amplifier; 110, pulse modulator; 111, acousto-optic frequency shifter. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0065] In some embodiments provided in this disclosure, the execution of the noise suppression method can be controlled by a unified controller or by multiple controllers. These controllers may include controllers on local terminals or controllers on remote servers. In some embodiments, the controllers on local terminals and the controllers on servers may work together to complete the noise suppression process. The local terminal mentioned in this disclosure may include, but is not limited to, various robotic devices, in-vehicle devices, personal computers, laptops, smartphones, tablets, wearable devices, medical devices, VR (Virtual Reality) devices, etc. The server may also be a server, server cluster, distributed subsystem, cloud processing platform, server containing blockchain nodes, or a combination thereof. The controllers described in this disclosure may include various control units capable of implementing logic processing functions, including but not limited to CPU (Central Processing Unit), PLC (Programmable Logic Controller), ECU (Electronic Control Unit), MCU (Microcontroller Unit), FPGA (Field Programmable Gate Array), and CPLD (Complex Programmable Logic Device), as well as controllers composed of one or more logic function units, chips, etc.

[0066] refer to Figure 1The fiber optic acoustic wave sensing system includes a laser 101, an electro-optic modulation device 102, a sensing fiber 103, a polarization diversity receiver 104, a data acquisition card 105, and a signal processing unit 106. The laser 101 can be a narrow-linewidth distributed feedback (DFB) type, preferably with a linewidth less than 1 kHz. It possesses continuous coherent light output capability, a narrow linewidth output light signal, and strong frequency stability, providing a stable and reliable light source foundation for the entire sensing system and ensuring the accuracy of subsequent modulation and sensing processes. The electro-optic modulator 1021 (EOM) can be a lithium niobate Mach-Zehnder type, operating in carrier-suppressed mode to modulate continuous light into carrier-suppressed double-sideband light. The sensing fiber 103, serving as the core sensing carrier, can be either an ultra-weak reflection microstructure fiber array or a distributed fiber. The ultra-weak reflection microstructure fiber array has a series of discrete reflection points distributed on it. These reflection points are fabricated through etching or writing processes, exhibiting extremely low reflectivity (typically -40dB to -70dB) and fixed spacing, forming a quasi-distributed sensing structure. This structure combines the advantages of traditional distributed sensing and point sensing, enabling precise perception of disturbances and signal feedback. The data acquisition card 105 features simultaneous digital sampling of multiple electrical signals. Its sampling rate and accuracy match the system's sensing requirements, allowing for rapid and accurate conversion of the analog electrical signals output by the polarization diversity receiver 104 into digital signals. The signal processing unit 106 incorporates core algorithms such as polarization synthesis, positive and negative sideband separation, phase demodulation, and noise suppression. It performs a series of calculations on the acquired digital signals, ultimately achieving noise suppression and acoustic signal demodulation.

[0067] refer to Figure 1 , Figure 3 and Figure 7Taking the sensing fiber 103 as an example of an ultra-weak reflection microstructure fiber array, the fiber optic acoustic wave sensing system also includes a fiber coupler 107 and a fiber optic circulator 108. In some embodiments, the laser 101 is activated to output a continuous and coherent optical signal. This optical signal first enters the fiber coupler 107, which splits the optical signal into two paths according to a design ratio. One path enters the modulation optical path to generate modulation light for subsequent pulse modulation, and the other path enters the local oscillator optical path to generate local oscillator light for interference detection. The optical signal in the modulation optical path is transmitted to the electro-optic modulation device 102. The double-sideband pulse light output by the electro-optic modulation device 102 is transmitted to the input end of the fiber optic circulator 108 through the fiber optic link. The fiber optic circulator 108 utilizes its unidirectional transmission characteristics to efficiently inject the double-sideband pulse light from the output end into the sensing fiber 103. When the double-sideband pulse light propagates in the sensing fiber 103, it encounters discrete reflection points and generates backlight carrying acoustic wave perturbation information. These reflected lights return to the fiber optic circulator 108 along the original optical path. After receiving the returned backlight, the fiber optic circulator 108 guides the backlight from a preset backlight output end through its internal optical path and transmits it directionally to the polarization diversity receiver 104. The polarization diversity receiver 104 receives the backlight from the fiber optic circulator 108 and mixes it with the local oscillator light transmitted through the local oscillator optical path. The polarization beam splitter inside the polarization diversity receiver 104 processes the backlight and local oscillator light separately, decomposing them into orthogonal polarization components. Then, an optical mixer achieves orthogonal interference, and a balanced detector converts the interference light signals into electrical signals, outputting four interference signals.

[0068] In some embodiments of this disclosure, a noise suppression method is provided, such as... Figure 2 As shown, this method is applied to Figure 1 Taking a fiber optic acoustic wave sensing system as an example, the following steps are included:

[0069] S20, continuous coherent light is output through laser 101.

[0070] Specifically, the laser 101 is typically a narrow-linewidth distributed feedback type, preferably a distributed feedback (DFB) laser with a linewidth of less than 1 kHz. It can generate continuous and highly coherent light, and the output optical signal has a narrow linewidth and stable frequency, making it the core light source of the fiber optic acoustic wave sensing system.

[0071] S21. The continuous coherent light is separated into local oscillator light, which is introduced into the local oscillator optical path, and modulated light, which is introduced into the modulation optical path, through the fiber optic coupler 107.

[0072] Specifically, the laser 101 can be activated to output a continuous and coherent optical signal. This optical signal first enters the fiber coupler 107, which splits the optical signal into two paths according to the design ratio. One path enters the modulation optical path as the modulation light for subsequent pulse modulation, and the other path enters the local oscillator optical path as the local oscillator light for interferometry detection.

[0073] S22. The modulated light is modulated into a double-sideband pulse light containing positive and negative sidebands by the electro-optic modulation device 102.

[0074] Specifically, the electro-optic modulation device 102 is a key component for realizing optical signal modulation, used to convert continuous light into pulsed light that meets the requirements. The double-sideband pulsed light containing positive and negative sidebands is a pulsed light signal generated by carrier-suppressed double-sideband modulation. The input continuous coherent light is converted into a pulse form containing both positive and negative sidebands. The two sidebands exhibit opposite response characteristics to modulation frequency noise during interference, providing a basis for subsequent elimination of phase noise through coherent summation and averaging.

[0075] S23. The double-sideband pulse light output by the electro-optic modulation device 102 is injected into the sensing fiber 103 through the fiber optic circulator 108.

[0076] Specifically, the optical signal in the modulation optical path is transmitted to the electro-optic modulation device 102; the double-sideband pulse light output by the electro-optic modulation device 102 is transmitted to the input end of the fiber optic circulator 108 through the fiber optic link, and the fiber optic circulator 108 uses its unidirectional transmission characteristics to inject the double-sideband pulse light from the output end into the sensing fiber 103.

[0077] S24. The double-sideband pulse light is received through the sensing optical fiber 103 and a backlight is generated. The backlight is then guided to the polarization diversity receiver 104 through the optical fiber circulator 108.

[0078] Specifically, the sensing fiber 103 is the core carrier of the sensing. It can be an ultra-weak reflection microstructure fiber array or a distributed fiber. The ultra-weak reflection microstructure fiber array consists of a series of discrete reflection points formed on the fiber. These reflection points have extremely low reflectivity and fixed spacing, which can realize quasi-distributed sensing.

[0079] Backlight refers to the optical signal that, after being modulated by the electro-optic modulator 102 and injected into the sensing fiber 103, is reflected back along the original optical path when it encounters a series of discrete reflection points during propagation. Taking the sensing fiber 103 as an example of an ultra-weak reflection microstructure fiber array, these discrete reflection points are etched or written on the fiber, have extremely low reflectivity and fixed spacing. After the pulse light interacts with the reflection points, reflection occurs, and the resulting backlight carries acoustic wave perturbation that affects the dynamic sensing phase information generated by the fiber segment.

[0080] S25. The local oscillator light and the backlight are received by the polarization diversity receiver and an interference signal is output.

[0081] Specifically, the polarization diversity receiver 104 is used to receive reflected light and output interference signals. It may include a polarization beam splitter, an optical mixer and a balanced detector, which can alleviate polarization fading problems and ensure stable signal acquisition.

[0082] The interference signal is an electrical signal generated by the internal optical components after the backlight enters the polarization diversity receiver 104. It is the basis for the sensing system to obtain phase information.

[0083] S26. The interference signal is synchronously digitized and sampled using the data acquisition card 105 to obtain a digital interference signal.

[0084] S27. The signal processing unit 106 performs positive and negative sideband separation on the digital interference signal to obtain an upper sideband signal and a lower sideband signal. The upper sideband signal and the lower sideband signal are polarization synthesized to obtain an effective upper sideband interference signal and an effective lower sideband interference signal. The effective upper sideband interference signal and the effective lower sideband interference signal are phase demodulated to obtain an upper sideband differential phase and a lower sideband differential phase. Phase noise reduction operation is performed on the upper sideband differential phase and the lower sideband differential phase to suppress the phase noise introduced by the modulation frequency drift.

[0085] The data acquisition card 105 is responsible for synchronous digital sampling of electrical signals, while the signal processing unit 106 undertakes core operations such as polarization synthesis, sideband separation, phase demodulation, and noise suppression.

[0086] In some embodiments of this disclosure, a carrier-suppressed double-sideband modulation method is used to modulate continuous light into double-sideband pulse light containing both positive and negative sidebands. By utilizing the opposite response characteristics of the positive and negative sidebands to modulation frequency noise during interference, the phase noise introduced by modulation frequency drift is eliminated at the signal level through positive and negative sideband multiplexing and phase noise reduction operations. This significantly improves the system's immunity to modulation frequency drift without the need for additional complex hardware, while also enhancing the long-term stability of the system and reducing the cost and complexity of hardware configuration, making the system more practical in real-world engineering applications.

[0087] In some embodiments of this disclosure, reference is made to Figure 3 The electro-optic modulation device 102 includes an electro-optic modulator 1021, a radio frequency drive source 1022, and a pulse generator 1023. S22 includes:

[0088] The radio frequency signal provided by the radio frequency driving source 1022 and the pulse width adjustable pulse signal provided by the pulse generator 1023 jointly drive the electro-optic modulator 1021, so that the electro-optic modulator 1021 operates in a carrier-suppressed state, modulating the continuous coherent light into a carrier-suppressed double-sideband pulse light containing positive and negative sidebands.

[0089] In some implementations, the RF driver 1022 outputs an RF signal at a preset frequency. This signal, after passing through a signal conditioning circuit, ensures stable amplitude and meets phase noise requirements. Simultaneously, the pulse generator 1023 is activated. Based on the system's sensing parameter requirements, an appropriate pulse width and repetition frequency are set. A synchronization calibration circuit ensures that the output signal of the pulse generator 1023 is synchronized with the RF signal of the RF driver 1022, reducing modulation distortion caused by signal asynchrony. The synchronized RF signal and pulse signal are input together to the electro-optic modulator 1021. The RF signal provides a frequency reference for modulation, while the pulse signal controls the modulation time window. Under the synergistic drive of these two signals, the refractive index of the lithium niobate crystal inside the electro-optic modulator 1021 changes periodically, causing a phase shift in the input continuous coherent light during transmission. By controlling the amplitude and phase relationship of the two driving signals, the electro-optic modulator 1021 operates in a carrier suppression state, suppressing the carrier frequency component of the continuous light and retaining only the signal components of the upper and lower sidebands. After modulation by the electro-optic modulator 1021, the original continuous coherent light is converted into carrier-suppressed double-sideband pulsed light. This double-sideband pulsed light contains both positive and negative sidebands, with the sideband frequencies determined by the RF signal frequency of the RF driver 1022 and the pulse width determined by the output signal width of the pulse generator 1023. The output double-sideband pulsed light possesses good coherence and stability, meeting the sensing requirements of the subsequent sensing fiber 103 and providing a high-quality modulated optical signal for the noise suppression process.

[0090] In some examples, the double-sideband pulse light that generates carrier suppression can be referred to by the following equation (1):

[0091]

[0092] In equation (1), For pulse envelope function, The center frequency of laser 101 The radio frequency modulation frequency of the electro-optic modulator 1021 The initial phase of the incident laser is random.

[0093] In some embodiments of this disclosure, the electro-optic modulator 1021 is stably operated in carrier suppression state by the coordinated driving of the radio frequency drive source 1022 and the pulse generator 1023. This enables the precise generation of double-sideband pulse light containing both positive and negative sidebands, ensuring the integrity and stability of the sideband signal and laying a good foundation for subsequent noise suppression and signal demodulation.

[0094] In some embodiments of this disclosure, the electro-optic modulation device 102 further includes an electro-optic modulation operating point controller 1024, which includes a bias voltage source and a feedback control circuit. S22 further includes:

[0095] The electro-optic modulation operating point controller 1024 monitors and controls the bias point of the electro-optic modulator 1021 through the bias voltage source and the feedback control circuit, so that the electro-optic modulator 1021 operates stably in the carrier suppression state.

[0096] In some implementations, the bias voltage source outputs a stable and adjustable voltage signal to provide bias support for the electro-optic modulator 1021; the feedback control circuit has real-time monitoring and dynamic adjustment capabilities, and can accurately capture changes in the operating state of the electro-optic modulator 1021. The electro-optic modulation operating point controller 1024 monitors and controls the bias point of the electro-optic modulator 1021 through the bias voltage source and the feedback control circuit, maintaining the stability of the bias point of the electro-optic modulator 1021 and ensuring that it continues to operate in carrier suppression state, thus guaranteeing the stable output of double-sideband pulsed light.

[0097] In some embodiments of this disclosure, the real-time monitoring and feedback control of the electro-optic modulation operating point controller 1024 can effectively reduce the drift of the bias point of the electro-optic modulator 1021 with temperature and time, maintain the stability of the modulation depth, reduce the additional noise caused by residual carrier leakage, and further improve the quality of the modulation signal and the long-term operational reliability of the system.

[0098] In some implementations, the core function of the polarization diversity receiver 104 is to acquire an interference signal containing positive and negative sideband phase information. This function can be decomposed into the following sub-functions: polarization diversity and coherent reception with sideband separation. Specifically, the polarization diversity function is used to address polarization fading and ensure signal stability; the coherent reception with sideband separation function is used to acquire a complete analytical interference signal to separate the positive and negative sidebands.

[0099] In some embodiments of this disclosure, reference is made to Figure 7The polarization diversity receiving device 104 includes a polarization diversity coherent receiver, which comprises a first polarization beamsplitter, a second polarization beamsplitter, a first optical 90° mixer, a second optical 90° mixer, a first balanced detector, a second balanced detector, a third balanced detector, and a fourth balanced detector. The step of receiving the local oscillator light and the backlight and outputting an interference signal through the polarization diversity receiving device includes:

[0100] Backlight of arbitrary polarization state is input to the first polarization beamsplitter and decomposed into horizontal and vertical polarization components. Local oscillator light is input to the second polarization beamsplitter and synchronously decomposed into horizontal and vertical polarization components to achieve matching and separation of the backlight and local oscillator light in polarization dimensions. The first optical 90° mixer is used to process the horizontal polarization channel, and its input terminals receive the horizontal polarization components of the backlight and local oscillator light, respectively. The second optical 90° mixer is used to process the vertical polarization channel, and its input terminals receive the vertical polarization components of the backlight and local oscillator light, respectively. The first or second optical 90° mixer internally includes cascaded fiber couplers and phase modulators, specifically including: two 1×2 fiber couplers in the first stage, used to connect one input backlight path to a... The local oscillator light is split into two paths. Two 2×2 fiber couplers in the second stage are used to cross-couple and interfere with the split backlight component and the local oscillator light component, achieving interference superposition of optical signals. A 90° fixed phase shift is introduced through the phase modulator in one of the interference paths. The four outputs of the first optical 90° mixer are connected to the first and second balanced detectors, generating in-phase and quadrature electrical signals for the horizontal polarization channels, respectively. That is, the first balanced detector outputs in-phase electrical signals for the horizontal polarization channels, and the second balanced detector outputs quadrature electrical signals for the horizontal polarization channels. The four outputs of the second optical 90° mixer are connected to the third and fourth balanced detectors, generating in-phase and quadrature electrical signals for the vertical polarization channels, respectively. That is, the third balanced detector outputs in-phase electrical signals, and the fourth balanced detector outputs quadrature electrical signals. Explained, the first, second, third, and fourth balanced detectors each include two separate sub-unit detectors to receive their respective signals independently. That is, each balanced detector contains two separate unit detectors, ultimately outputting one signal.

[0101] In some embodiments, the polarization diversity receiver 104 integrates two polarization beamsplitters, two optical 90° mixers, and four balanced detectors. The polarization beamsplitters process the backlight and local oscillator light respectively, decomposing them into orthogonal polarization components; the optical 90° mixers achieve orthogonal interference; and the balanced detectors are responsible for converting the optical signal into an electrical signal, ultimately outputting four interference signals, effectively solving the polarization fading problem.

[0102] The polarization beamsplitter in the polarization diversity receiver 104 decomposes the backlight and local oscillator light into two orthogonal polarization components. Then, two optical 90° mixers cause interference between the corresponding polarization components. Finally, four balanced detectors convert the optical signals into electrical signals, ultimately forming two sets of mutually perpendicular signals: in-phase and orthogonal electrical signals for the horizontal polarization channel, and in-phase and orthogonal electrical signals for the vertical polarization channel. These two sets of signals contain complete phase information for both positive and negative sidebands and effectively solve the polarization fading problem, providing stable data support for subsequent polarization synthesis, sideband separation, and phase demodulation.

[0103] In other embodiments of this disclosure, reference is made to Figure 5 , Figure 6 and Figure 8 The polarization diversity receiving device 104 includes a polarization diversity receiver and an acousto-optic frequency shifter 111; see reference Figure 8 The polarization diversity receiver includes a third polarization beamsplitter, a fourth polarization beamsplitter, two fiber couplers, and two balanced detectors. The polarization diversity receiver receives the local oscillator light and the backlight light and outputs an interference signal. This includes placing the acousto-optic frequency shifter 111 in the modulation optical path before injecting the double-sideband pulse light output from the electro-optic modulation device into the sensing fiber through the fiber circulator, thereby shifting the modulation light at a fixed frequency to achieve frequency shift of the beat frequency signal. Backlight of arbitrary polarization state is input to the third polarization beamsplitter and decomposed into horizontal and vertical polarization components. Local oscillator light is input to the fourth polarization beamsplitter and simultaneously decomposed into horizontal and vertical polarization components to achieve matching separation of the backlight and local oscillator light in polarization dimensions. Two 2×2 fiber couplers correspond to two orthogonal polarization state channels, respectively, used to cross-couple and interfere with the backlight component and local oscillator light component under the same polarization state, achieving interference superposition of optical signals. The four coupled interference optical signals are input to two balanced detectors, respectively generating interference electrical signals for the horizontal and vertical polarization channels. (Explanatory) Figure 8 The two balance detectors in the system also include two separate sub-unit detectors to receive the corresponding signals and ultimately output a signal.

[0104] In some embodiments, a combination of a polarization diversity receiver and an acousto-optic frequency shifter 111 can be used instead, with the acousto-optic frequency shifter 111 placed in the modulation optical path to fix the frequency of the modulation light (e.g., ...). The frequency shifting of the polarization diversity receiver is achieved by two polarization beamsplitters, two fiber couplers, and two balanced detectors. The two polarization beamsplitters process the backlight and local oscillator light respectively. The two 2×2 fiber couplers correspond to two orthogonal polarization state channels, which are used to cross-couple and interfere with the backlight component and the local oscillator light component under the same polarization state, so as to realize the interference superposition of optical signals. The two balanced detectors simultaneously acquire the interference signals of the two orthogonal polarization states.

[0105] Working principle: After frequency shifting by the acousto-optic frequency shifter 111, the heterodyne frequencies of the positive and negative sideband signals and the local oscillator light become respectively... and The two sidebands are distinguished and separated in the frequency domain through subsequent digital signal processing, and then their respective phases are demodulated. This provides an alternative technical approach for sideband separation while maintaining polarization fading suppression capabilities.

[0106] In some implementations, refer to Figure 4 The fiber optic acoustic wave sensing system may also include an erbium-doped fiber amplifier 109, which can serve as a pulsed optical power amplifier and is placed after the electro-optic modulation device 102 to increase the peak power of the pulse injected into the sensing fiber, thereby enhancing the back-reflected signal strength. In some examples, for short-distance or high-reflectivity sensing arrays, the erbium-doped fiber amplifier 109 may not be configured.

[0107] In some implementations, refer to Figure 4 The fiber optic acoustic wave sensing system may also include a pulse modulator 110, which may include an acousto-optic modulator or a semiconductor optical amplifier, positioned after the electro-optic modulation device 102 and before or after the erbium-doped fiber amplifier 109, to further improve the extinction ratio of the optical pulse and suppress spontaneous emission noise. In some examples, for short-range sensing, the pulse modulator 110 may not be configured.

[0108] In some embodiments of this disclosure, S27 includes:

[0109] The digital interference signal is filtered to separate the upper sideband signal with a positive radio frequency modulation frequency and the lower sideband signal with a negative radio frequency modulation frequency.

[0110] Polarization synthesis is performed by vector rotation or polarization filtering to construct effective interference signals in the upper and lower sidebands.

[0111] The instantaneous phases of the upper sideband effective interference signal and the lower sideband effective interference signal are calculated respectively. The instantaneous phases include the dynamic sensing phase introduced by the acoustic disturbance, the modulation frequency-related phase, and the laser center frequency-related phase.

[0112] The instantaneous phase of the effective interference signal in the upper sideband corresponding to two points at a preset sampling point interval is differentially divided with front and rear phases to obtain the differential phase of the upper sideband.

[0113] The instantaneous phases of the effective interference signals in the lower sideband corresponding to two points at a preset sampling point interval are differentially divided before and after to obtain the differential phase of the lower sideband.

[0114] Specifically, in some dependencies Figure 3 , Figure 4 and Figure 7 In the example of the system, the pulsed light propagates in the sensing fiber 103, and each discrete reflection point returns the back light, as shown in the following equation (2):

[0115] (2)

[0116] In formula (2) Let be the complex reflection coefficient of the i-th reflection point. Let be the round-trip time delay of the light pulse reaching the i-th reflection point and returning. is the group velocity of light in the optical fiber; The cumulative dynamic sensing phase of the fiber segment between the beginning of the fiber and the i-th reflection point is determined by the acoustic perturbation.

[0117] The backlight enters the polarization diversity coherent receiver via the fiber optic circulator 108. In the receiver, the backlight is split into two orthogonal polarization components, horizontal (X) and vertical (Y), by a first polarization beamsplitter. Simultaneously, the local oscillator light is split into two orthogonal polarization components, X and Y, by a second polarization beamsplitter. Subsequently, the X-polarized component of the backlight interferes with the X-polarized component of the local oscillator light in a first 90° optical mixer, generating four X-polarized interference signals; the Y-polarized component of the backlight interferes with the Y-polarized component of the local oscillator light in a second 90° optical mixer, generating four Y-polarized interference signals.

[0118] The four sets of interference signals (eight-way interference signals) are converted into electrical signals by the corresponding balanced detectors (i.e., the first to fourth balanced detectors), and are synchronously sampled by the data acquisition card 105 to obtain:

[0119] , In-phase / quadrature components of the X-polarization channel This refers to the in-phase component of the X-polarization channel. The orthogonal components of the X-polarization channel; and

[0120] , In-phase / quadrature components of the Y-polarization channel For the in-phase component of the Y-polarization channel, These are the orthogonal components of the Y-polarization channel.

[0121] In other examples, complex interference signals for each polarization channel can be constructed, as shown in equation (3):

[0122]

[0123] Then, the complex interference signals of each polarization channel are filtered to... and Separate processing is performed to obtain the upper sideband signal. and the signal above (center frequency is) ); signal below and the lower sideband signal (center frequency is) ).

[0124] Finally, the upper and lower sideband signals can be polarized and synthesized using vector rotation or polarization filtering to construct an effective upper sideband interference signal. and the effective interference signal of the lower sideband .

[0125] Calculate the effective interference signal of the upper sideband respectively. and the effective interference signal of the lower sideband The instantaneous phase is given by the following formula (4):

[0126]

[0127]

[0128] The differential phases of the upper and lower sidebands can be determined by the reflected light signals from adjacent discrete reflection points in the sensing fiber 103, respectively, referring to the following equation (5):

[0129]

[0130]

[0131] In equation (5), The cumulative dynamic sensing phase of the optical fiber segment between the (i-1)th and i-th reflection points is determined by the acoustic perturbation. The distance between discrete reflection points. This is the phase term related to the center frequency of laser 101.

[0132] In some embodiments of this disclosure, the effective phase information of two sidebands is accurately extracted through a complete process of polarization synthesis, sideband separation, phase demodulation, and differential phase solution, and the dynamic sensing phase is clearly separated from other interference phases, thereby improving the accuracy of signal demodulation.

[0133] In some embodiments of this disclosure, S27 further includes:

[0134] The phase summation and mean operation or the phase difference and mean operation are performed on the front and rear differential phases of the upper and lower sidebands to make the phases related to the center frequency of laser 101 cancel each other out, so as to suppress the phase noise introduced by the modulation frequency drift.

[0135] by Figure 3 , Figure 4 and Figure 7 For example, in some implementations, referring to equation (5), if only a single sideband is used, when the modulation frequency drifts... When this happens, the demodulation differential phase will introduce an error, as shown in equation (6):

[0136]

[0137] In equation (6), the positive and negative signs are related to the selected sideband. This error is proportional to the magnitude of the modulation frequency drift and is a major noise source in distributed acoustic sensing.

[0138] In some examples, the positive and negative sidebands can be reused to perform the summation and averaging of the positive and negative sideband phases, as shown in the following formula (7):

[0139]

[0140] The modulation frequency drift was eliminated by averaging the phase summation of the positive and negative sidebands. The effect on the sensing phase achieves natural immunity to frequency drift noise introduced by the electro-optic modulator 1021.

[0141] In addition, refer to Figure 5 , Figure 6 and Figure 8 In another way based on Figure 5 , Figure 6 and Figure 8 In fiber optic sensing systems employing a combination of polarization diversity receivers and acousto-optic frequency shifters (AOMs), placing the AOM in the modulation optical path allows for the modulation of the light at a fixed frequency (e.g., ...). The frequency shift of the signal, after being shifted by the acousto-optic frequency shifter, results in the positive and negative sideband signals and the heterodyne frequencies of the local oscillator light becoming respectively... and The two sidebands are distinguished and separated in the frequency domain through subsequent digital signal processing, and then their respective phases are demodulated. This provides another technical approach for sideband separation while maintaining polarization fading suppression capabilities. The frequency shift magnitude and direction of the acousto-optic frequency shifter can actually be arbitrary; for ease of derivation, we assume... The noise suppression method can be implemented using the following steps:

[0142] Step 1: Output and modulation of laser 101.

[0143] The continuous light output from laser 101 is modulated by electro-optic modulation device 102 to generate carrier-suppressed double-sideband pulsed light, which is then frequency-shifted and modulated by acousto-optic frequency shifter 111 before being input into sensing fiber 103. The formula for the corresponding optical signal can be expressed as:

[0144]

[0145] in, For pulse envelope function, The center frequency of the laser. The radio frequency modulation frequency of the electro-optic modulation device. The modulation frequency of the acousto-optic frequency shifter. The initial phase of the incident laser is random.

[0146] Step 2: Back reflection and polarization diversity reception.

[0147] Specifically, the double-sideband pulsed light propagates in the sensing fiber 103. Taking the sensing fiber 103 as an example of an ultra-weak reflection fiber array, the expression for the reflected light (i.e., the backlight) returned from each discrete reflection point is as follows: (9)

[0148] in, Let be the complex reflection coefficient of the i-th reflection point. Let be the round-trip time delay of the light pulse reaching the i-th reflection point and returning. Let be the group velocity of light in the optical fiber. The cumulative dynamic sensing phase of the fiber segment between the beginning of the fiber and the i-th reflection point is determined by the acoustic perturbation.

[0149] Then, the backlight enters the polarization diversity receiver via the fiber optic circulator 108. In the polarization diversity receiver, the backlight is split into two orthogonal polarization components, X and Y, by the third polarization beam splitter. Simultaneously, the local oscillator light is split into two orthogonal polarization components, X and Y, by the fourth polarization beam splitter. Subsequently, the X-polarization component of the backlight interferes with the X-polarization component of the local oscillator light in one of the 2×2 fiber couplers, generating an X-polarized interference signal; the Y-polarization component of the backlight interferes with the Y-polarization component of the local oscillator light in the second 2×2 fiber coupler, generating a Y-polarized interference signal.

[0150] Step 3: Photoelectric conversion and digital sampling.

[0151] Specifically, the interference signal obtained in step 2 is converted into an electrical signal by the corresponding balanced detector and synchronously sampled by the data acquisition card to obtain: The interference signal in the X-polarization channel contains two frequency components. and ; The interference signal in the Y-polarization channel contains two frequency components. and .

[0152] Step 4: Complex signal construction and positive and negative sideband separation.

[0153] Specifically, the positive and negative sideband separation and complex signal construction are performed using the I / Q quadrature demodulation method, which includes:

[0154] Genesis and Two local digital signals of the same frequency, equal amplitude, and orthogonal to each other, i.e. and Then these two digital signals were respectively compared with... and Perform frequency mixing, and then filter the mixed signal at a frequency of... A bandpass filter is used to obtain the upper sideband complex interference signal. and ;

[0155] Genesis and Two local digital signals of the same frequency, equal amplitude, and orthogonal to each other, i.e. and Then these two digital signals were respectively compared with... and Perform frequency mixing, and then filter the mixed signal at a frequency of... A bandpass filter is used to obtain the lower sideband complex interference signal. and .

[0156] Step 5: Polarization synthesis and phase demodulation.

[0157] Specifically, polarization synthesis is performed using vector rotation or polarization filtering methods to construct an effective interference signal in the upper sideband. and the effective interference signal of the lower sideband .

[0158] Then, the effective interference signals of the upper sidebands are calculated respectively. and the effective interference signal of the lower sideband The instantaneous phase is given by the following formula:

[0159]

[0160] (10)

[0161] Finally, the front-to-back differential phases of adjacent reflection point positions are:

[0162]

[0163] (11)

[0164] in, The cumulative dynamic sensing phase of the optical fiber segment between the (i-1)th and i-th reflection points is determined by the acoustic perturbation. The distance between discrete reflection points. This is the phase term related to the center frequency of the laser.

[0165] Step 6: Noise suppression processing.

[0166] Specifically, according to the demodulation differential phase formula in step 5, if only a single sideband is used, when the modulation frequency drifts... In this case, demodulation of the differential phase will introduce an error:

[0167]

[0168] The sign is related to the selected sideband. This error is proportional to the magnitude of the modulation frequency drift and is a major noise source in distributed acoustic sensing.

[0169] The positive and negative sideband multiplexing method is used to calculate the phase half difference of the positive and negative sidebands, i.e., the phase difference mean operation:

[0170] (12)

[0171] Modulation frequency drift can then be eliminated by calculating the average difference between the positive and negative sideband phases. The effect on the sensing phase achieves natural immunity to frequency drift noise introduced by the electro-optic modulator 1021 in the electro-optic modulation device.

[0172] In some embodiments of this disclosure, phase noise reduction operations on the differential phases of the positive and negative sidebands are performed to specifically counteract the phase interference caused by modulation frequency drift, thereby eliminating this main noise source, improving the signal-to-noise ratio of the system, and making the detection of acoustic wave sensing signals more accurate.

[0173] The noise suppression methods disclosed herein employ carrier-suppressed double-sideband modulation to modulate continuous light into pulsed light containing both positive and negative sidebands. By utilizing the opposite response characteristics of the positive and negative sidebands to modulation frequency noise during interference, and through positive and negative sideband multiplexing and phase noise reduction operations, the phase noise introduced by modulation frequency drift is directly eliminated at the signal level. This eliminates the need for additional complex hardware, significantly improves the system's immunity to modulation frequency drift, enhances the long-term stability of the system, reduces the cost and complexity of hardware configuration, and makes the system more practical in real-world engineering applications.

[0174] It is understood that the various embodiments of the methods described in this specification are presented in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. Related details can be found in the descriptions of other method embodiments.

[0175] It should be understood that although the steps in the flowcharts shown in the accompanying drawings are displayed sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the accompanying drawings may include multiple steps or stages, which are not necessarily completed at the same time, but may be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but may be performed alternately or in turn with other steps or at least a portion of the steps or stages of other steps.

[0176] Based on the description of the noise suppression method embodiments described above, this disclosure also provides a noise suppression apparatus for implementing the noise suppression method involved above. The apparatus may include a system (including a distributed system), software (application), module, component, controller, server, terminal, etc., using the method described in the embodiments of this specification, combined with necessary hardware implementation. Based on the same innovative concept, the apparatuses in one or more embodiments provided in this disclosure are as described in the following embodiments. Since the implementation schemes and methods for solving the problem by the apparatus are similar, the implementation of the specific apparatus in the embodiments of this specification can refer to the implementation of the foregoing method, and repeated details will not be repeated. As used below, the terms "unit" or "module" can refer to a combination of software and / or hardware that implements a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0177] Figure 9This is a schematic block diagram illustrating a noise suppression device according to an exemplary embodiment. The device can be the aforementioned terminal, a server, or a module, component, device, control unit, etc., integrated into the terminal. For details, please refer to... Figure 9 The device 200 may include: a light source output module 210, an optical path splitting module 220, an electro-optic modulation module 230, a pulse light injection module 240, a sensing reflection module 250, a coherent receiving module 260, a sampling module 270, and a signal processing module 280. The system includes: a light source output module 210 for outputting continuous coherent light via a laser; an optical path splitting module 220 for separating the continuous coherent light into two paths via an optical fiber coupler: a local oscillator light for input to the local oscillator optical path and a modulation light for input to the modulation optical path; an electro-optic modulation module 230 for modulating the modulation light into a double-sideband pulse light containing positive and negative sidebands via an electro-optic modulation device; a pulse light injection module 240 for injecting the double-sideband pulse light output from the electro-optic modulation device into the sensing optical fiber via the optical fiber circulator; a sensing reflection module 250 for receiving the double-sideband pulse light via the sensing optical fiber and generating backlight, and guiding the backlight to the polarization diversity receiving device via the optical fiber circulator; and a coherent receiving module 260 for receiving the polarization diversity receiving device via the optical fiber. The system receives the local oscillator light and the backlight and outputs an interference signal; a sampling module 270 is used to synchronously digitize the interference signal through a data acquisition card to obtain a digital interference signal; a signal processing module 280 is used to separate the positive and negative sidebands of the digital interference signal through a signal processing unit to obtain an upper sideband signal and a lower sideband signal, to perform polarization synthesis on the upper sideband signal and the lower sideband signal to obtain an effective upper sideband interference signal and an effective lower sideband interference signal, to perform phase demodulation on the effective upper sideband interference signal and the effective lower sideband interference signal to obtain an upper sideband differential phase and a lower sideband differential phase respectively, and to perform phase noise reduction operation on the upper sideband differential phase and the lower sideband differential phase to suppress the phase noise introduced by modulation frequency drift through the phase noise reduction operation.

[0178] Each module in the aforementioned noise suppression device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0179] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 10As shown, the computer device includes a processor, memory, communication interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements a noise suppression method.

[0180] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0181] Based on the foregoing description of the relevant methods and apparatus embodiments, this disclosure also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, it implements the noise suppression method described in any embodiment of this specification.

[0182] Based on the foregoing description of the relevant methods and apparatus embodiments, this disclosure also provides a computer-readable storage medium that, when the instructions in the computer-readable storage medium are executed by the processor of a computer device, enables the computer device to implement the noise suppression method as described in any embodiment of this disclosure.

[0183] Based on the foregoing description of the relevant methods and apparatus embodiments, this disclosure also provides a computer program product, including a computer program that, when executed by a processor, implements the noise suppression method described in any embodiment of this specification.

[0184] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, hardware + program embodiments are relatively simple in description because they are fundamentally similar to method embodiments; relevant parts can be referred to the descriptions in the method embodiments.

[0185] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0186] It should be noted that the apparatus, computer equipment, storage medium, and computer program products described above may also include other implementation methods according to the description of the method embodiments. Specific implementation methods can be found in the description of the relevant method embodiments. Furthermore, new embodiments formed by combinations of features from various methods, apparatuses, devices, and server embodiments still fall within the scope of this disclosure and will not be elaborated upon here.

[0187] For ease of description, the above devices are described in terms of function, divided into various modules. Of course, when implementing one or more of these specifications, the functions of each module can be implemented in the same or different software and / or hardware, or a module that performs the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are merely illustrative. For example, the division of modules or units is only a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling and communication connections between the devices or units shown or described can be implemented through direct and / or indirect coupling / connection, through standard or custom interfaces or protocols, and can be implemented electrically, mechanically, or in other forms.

[0188] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0189] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A noise suppression method, characterized in that, An application is made in a fiber optic acoustic wave sensing system, the fiber optic acoustic wave sensing system comprising a laser, a fiber optic coupler, an electro-optic modulation device, a sensing fiber, a fiber optic circulator, a polarization diversity receiver, a data acquisition card, and a signal processing unit, the method comprising: The laser outputs continuous coherent light. The continuous coherent light is separated into local oscillator light, which is directed to the local oscillator optical path, and modulated light, which is directed to the modulation optical path, through the fiber optic coupler. The electro-optic modulation device modulates the modulated light into a double-sideband pulse light containing positive and negative sidebands; The double-sideband pulsed light is injected into the sensing fiber through the fiber circulator; The double-sideband pulse light is received through the sensing optical fiber and a backlight is generated. The backlight is then guided to the polarization diversity receiving device through the optical fiber circulator. The polarization diversity receiver receives the local oscillator light and the backlight and outputs an interference signal. The interference signal is synchronously digitally sampled using a data acquisition card to obtain a digital interference signal; The digital interference signal is separated into positive and negative sidebands by a signal processing unit to obtain an upper sideband signal and a lower sideband signal. The upper sideband signal and the lower sideband signal are then polarized and combined to obtain an effective upper sideband interference signal and an effective lower sideband interference signal. The effective upper sideband interference signal and the effective lower sideband interference signal are then phase demodulated to obtain an upper sideband differential phase and a lower sideband differential phase. Phase noise reduction is performed on the upper sideband differential phase and the lower sideband differential phase to suppress phase noise introduced by modulation frequency drift.

2. The method according to claim 1, characterized in that, The electro-optic modulation device includes an electro-optic modulator, a radio frequency driver, and a pulse generator. Modulating the modulated light into a double-sideband pulse light containing positive and negative sidebands via the electro-optic modulation device includes: The electro-optic modulator is driven by the radio frequency driving source providing the radio frequency signal and the pulse generator providing the pulse width adjustable pulse signal, so that the electro-optic modulator operates in the carrier suppression state and modulates the continuous coherent light into a carrier-suppressed double-sideband pulse light containing positive and negative sidebands.

3. The method according to claim 2, characterized in that, The electro-optic modulation device further includes an electro-optic modulation operating point controller, which includes a bias voltage source and a feedback control circuit. The step of modulating the modulated light into a double-sideband pulse light containing positive and negative sidebands via the electro-optic modulation device further includes: The electro-optic modulation operating point controller monitors and controls the bias point of the electro-optic modulator through the bias voltage source and the feedback control circuit, so that the electro-optic modulator operates stably in the carrier suppression state.

4. The method according to claim 1, characterized in that, The polarization diversity receiving device includes a polarization diversity coherent receiver, which comprises a first polarization beamsplitter, a second polarization beamsplitter, a first optical 90° mixer, a second optical 90° mixer, a first balanced detector, a second balanced detector, a third balanced detector, and a fourth balanced detector. The step of receiving the local oscillator light and the backlight and outputting an interference signal through the polarization diversity receiving device includes: Backlight with arbitrary polarization is input to the first polarization beam splitter and decomposed into horizontal polarization components and vertical polarization components; local oscillator light is input to the second polarization beam splitter and is simultaneously decomposed into horizontal polarization components and vertical polarization components, so as to achieve matching and separation of backlight and local oscillator light in polarization dimension. The first optical 90° mixer is used to process the horizontal polarization channel, and its input terminal receives the horizontal polarization component of the backlight and the horizontal polarization component of the local oscillator light respectively; the second optical 90° mixer is used to process the vertical polarization channel, and its input terminal receives the vertical polarization component of the backlight and the vertical polarization component of the local oscillator light respectively. The first or second optical 90° mixer internally includes cascaded fiber couplers and phase modulators, specifically including: two 1×2 fiber couplers in the first stage, used to split one input backlight and one local oscillator light into two paths respectively; two 2×2 fiber couplers in the second stage, used to cross-couple and interfere with the split backlight component and the local oscillator light component to achieve interference superposition of optical signals; and a 90° fixed phase shift is introduced in one of the interference optical paths through the phase modulator; The four outputs of the first optical 90° mixer are connected to the first balanced detector and the second balanced detector, respectively generating in-phase and quadrature electrical signals for the horizontal polarization channel; the four outputs of the second optical 90° mixer are connected to the third balanced detector and the fourth balanced detector, respectively generating in-phase and quadrature electrical signals for the vertical polarization channel.

5. The method according to claim 1, characterized in that, The process involves separating the positive and negative sidebands of the digital interference signal using a signal processing unit to obtain an upper sideband signal and a lower sideband signal; performing polarization synthesis on the upper and lower sideband signals to obtain an effective upper sideband interference signal and an effective lower sideband interference signal; performing phase demodulation on the effective upper and lower sideband interference signals to obtain an upper sideband differential phase and a lower sideband differential phase, respectively; and performing phase noise reduction operations on the upper and lower sideband differential phases to suppress phase noise introduced by modulation frequency drift. This includes: The digital interference signal is filtered to separate the upper sideband signal with a positive radio frequency modulation frequency and the lower sideband signal with a negative radio frequency modulation frequency. Polarization synthesis is performed by vector rotation or polarization filtering to construct effective interference signals in the upper and lower sidebands. The instantaneous phases of the upper sideband effective interference signal and the lower sideband effective interference signal are calculated respectively. The instantaneous phases include the dynamic sensing phase introduced by the acoustic disturbance, the modulation frequency-related phase, and the laser center frequency-related phase. The instantaneous phase of the effective interference signal in the upper sideband corresponding to two points at a preset sampling point interval is differentially divided with the preceding and following phases to obtain the differential phase of the upper sideband. The instantaneous phases of the effective interference signals in the lower sideband corresponding to two points at a preset sampling point interval are differentially divided before and after to obtain the differential phase of the lower sideband.

6. The method according to claim 5, characterized in that, The step of performing phase noise reduction operations on the upper sideband differential phase and the lower sideband differential phase to suppress phase noise introduced by modulation frequency drift includes: The upper sideband differential phase and the lower sideband differential phase are subjected to phase summation and mean operation or phase difference and mean operation to make the modulation frequency related phases cancel each other out, so as to suppress the phase noise introduced by modulation frequency drift.

7. The method according to claim 1, characterized in that, The polarization diversity receiving device includes a polarization diversity receiver and an acousto-optic frequency shifter. The polarization diversity receiver includes a third polarization beamsplitter, a fourth polarization beamsplitter, two fiber optic couplers, and two balanced detectors. The step of receiving the local oscillator light and the backlight through the polarization diversity receiver and outputting an interference signal includes: Before injecting the double-sideband pulsed light output by the electro-optic modulation device into the sensing fiber through the fiber circulator, the acousto-optic frequency shifter is placed in the modulation optical path to shift the modulation light at a fixed frequency, thereby achieving frequency shift of the beat frequency signal. Backlight with arbitrary polarization is input to the third polarization beam splitter and decomposed into horizontal polarization components and vertical polarization components; local oscillator light is input to the fourth polarization beam splitter and is simultaneously decomposed into horizontal polarization components and vertical polarization components, so as to achieve matching and separation of backlight and local oscillator light in polarization dimension. Two 2×2 fiber couplers correspond to two orthogonal polarization state channels, which are used to cross-couple and interfere with the backlight component and the local oscillator component under the same polarization state to achieve interference superposition of optical signals; the four interference optical signals after coupling are input to two balanced detectors to generate interference electrical signals of horizontal polarization channel and vertical polarization channel, respectively.

8. The method according to claim 1, characterized in that, The sensing fiber includes an ultra-weak reflection microstructure fiber array or a distributed fiber.

9. A noise suppression device, characterized in that, This is applied to a fiber optic acoustic wave sensing system, which includes a laser, a fiber optic coupler, an electro-optic modulation device, a sensing fiber, a fiber optic circulator, a polarization diversity receiver, a data acquisition card, and a signal processing unit. The device includes: A light source output module is used to output continuous coherent light via a laser; An optical path splitting module is used to separate the continuous coherent light into local oscillator light, which is directed to the local oscillator optical path, and modulated light, which is directed to the modulation optical path, through an optical fiber coupler. An electro-optic modulation module is used to modulate the modulated light into a double-sideband pulse light containing positive and negative sidebands using an electro-optic modulation device; A pulsed light injection module is used to inject the double-sideband pulsed light into the sensing fiber through the fiber circulator; A sensing reflection module is used to receive the double-sideband pulse light through the sensing optical fiber and generate backlight, and guide the backlight to the polarization diversity receiving device through the optical fiber circulator. The coherent receiving module is used to receive the local oscillator light and the backlight through the polarization diversity receiving device and output an interference signal; The sampling module is used to synchronously digitize the interference signal through a data acquisition card to obtain a digital interference signal; The signal processing module is used to separate the positive and negative sidebands of the digital interference signal through the signal processing unit to obtain an upper sideband signal and a lower sideband signal; to perform polarization synthesis on the upper sideband signal and the lower sideband signal to obtain an effective upper sideband interference signal and an effective lower sideband interference signal; to perform phase demodulation on the effective upper sideband interference signal and the effective lower sideband interference signal to obtain an upper sideband differential phase and a lower sideband differential phase respectively; and to perform phase noise reduction operation on the upper sideband differential phase and the lower sideband differential phase to suppress the phase noise introduced by modulation frequency drift.

10. A computer device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method according to any one of claims 1 to 8.

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