A fiber vibration sensing system and method based on self-generated carrier wave by frequency sweeping interference

Abstract

The application relates to the technical field of optical fiber sensing and optical fiber interference measurement, in particular to an optical fiber vibration sensing system and method based on a swept-frequency interference self-generated carrier. The system comprises a swept-frequency optical pulse generation unit, which is used for generating a linear swept-frequency pulse optical signal; a non-equal-arm interference unit, which automatically generates a beat frequency carrier signal by utilizing the interference between the swept-frequency pulse optical signal and a time delay signal thereof; an optoelectrical signal conversion unit, which is used for converting the beat frequency optical signal carrying vibration phase information into an electrical signal and completing analog-digital conversion; and a digital demodulation unit, which is used for demodulating the beat frequency signal to obtain vibration phase information. Compared with a heterodyne detection technology, the application has higher energy utilization rate, and eliminates the influence of modulation depth fluctuation in a PGC detection technology, and has better performance in sensitivity, system stability and complexity. Therefore, the scheme has good engineering practical value and is suitable for popularization and deployment in application scenarios such as a hydrophone array.

Description

Technical Field

[0001] This application relates to the fields of fiber optic sensing and fiber optic interferometry, and in particular to a fiber optic vibration sensing system and method based on frequency sweeping interferometry self-generated carrier. Background Technology

[0002] Interferometric fiber optic vibration sensors are among the most sensitive fiber optic sensing technologies currently available. Typical existing solutions include: (1) Phase Generated Carrier (PGC) Demodulation: The carrier is generated by piezoelectric ceramics or phase modulator. Its disadvantages are: the modulation depth is prone to drift, requiring elliptic fitting correction, poor long-term stability, and complex algorithm.

[0003] (2) Heterodyne demodulation: Frequency-shifted carrier is generated by an acousto-optic modulator. Its disadvantages are: it adopts a dual-pulse structure, resulting in low pulse energy utilization, complex optical links, and high system cost.

[0004] (3) 3×3 coupler demodulation: Quadrature demodulation is achieved by using the phase difference of three channels. Its disadvantages are: it requires three detectors and three analog-to-digital converters, which is costly and sensitive to phase error.

[0005] In summary, existing technologies all require the introduction of additional carrier generation devices or special coupling structures, resulting in high system complexity, limited long-term stability, and an inability to simultaneously achieve both energy efficiency and demodulation ease. Summary of the Invention

[0006] The purpose of this application is to overcome the above-mentioned defects of the prior art and provide a fiber optic vibration sensing system and method based on frequency sweeping interference self-generated carrier, which can be applied to fiber optic hydrophones, marine acoustic monitoring, structural health monitoring, perimeter security, seismic wave detection and other high-sensitivity vibration measurement scenarios.

[0007] To solve the above-mentioned technical problems, the fiber optic vibration sensing system based on frequency sweeping interferometry self-generated carrier provided by this application includes: A swept-frequency optical pulse generation unit is used to generate a swept-frequency pulse optical signal whose frequency varies linearly with time. A non-equidistant arm interference unit is connected to the output end of a swept-frequency optical pulse generation unit; it has a reference arm and a sensing arm with a fixed optical path difference; it is used to receive swept-frequency pulse optical signals and automatically generate beat-frequency carrier signals by utilizing the interference between the swept-frequency pulse optical signals and the time delay signals of the swept-frequency pulse optical signals; wherein, external vibrations act on the sensing arm to cause optical path changes, so that the vibration phase is superimposed on the beat-frequency carrier signal in the form of phase modulation, and an interferometric beat-frequency optical signal carrying vibration phase information is output. The photoelectric signal conversion unit, connected to the output of the non-equidistant arm interferometer, is used to convert the interferometric beat frequency optical signal carrying vibration phase information into an electrical signal and complete the analog-to-digital conversion; and The digital demodulation unit is used to demodulate the digitized beat frequency signal and extract the vibration phase information.

[0008] As an improvement to the above technical solution, the frequency sweeping optical pulse generation unit uses a narrow linewidth laser with an acousto-optic modulator, or a narrow linewidth laser with an electro-optic modulator, or directly modulates the injection current of a tunable laser to achieve linear frequency sweeping.

[0009] As an improvement to the above technical solution, the non-equilateral interference unit is any one of a Michelson interferometer, a Mach-Zehnder interferometer, or a Fabry-Perot interferometer.

[0010] As an improvement to the above technical solution, a fixed arm length difference exists between the reference arm and the sensing arm of the non-equidistant arm interference unit. The fixed time delay difference between the reference arm and the sensing arm satisfy: ;in, The refractive index of the optical fiber. The speed of light in a vacuum; the beat frequency of the beat frequency carrier signal. satisfy: ;in, The sweep rate of the sweep pulse light; by changing the fixed time delay difference between the reference arm and the sensing arm. and / or change the sweep rate of the sweep pulse light. Change the beat frequency of the beat frequency carrier signal To achieve the beat frequency of the beat frequency carrier signal Flexible configuration.

[0011] As an improvement to the above technical solution, the non-equidistant arm interference unit is provided with an adjustable optical delay line to adjust the fixed time delay difference between the reference arm and the sensing arm. The frequency sweeping optical pulse generation unit changes the frequency sweeping range of the frequency sweeping pulse optical signal. and / or pulse width Adjust the sweep rate of the sweep pulse optical signal. .

[0012] As an improvement to the above technical solution, the photoelectric signal conversion unit is a single-channel photoelectric signal conversion unit, comprising: a PIN photodetector for converting the interference beat frequency optical signal into an electrical signal, and an analog-to-digital converter for analog-to-digital conversion; the digital demodulation unit is a single-channel digital demodulation unit; the digital demodulation unit internally integrates, in sequence: a DC component removal subunit for performing DC component removal processing on the digitized beat frequency signal to obtain an AC beat frequency signal; a Hilbert transform subunit for performing a Hilbert transform on the AC beat frequency signal to construct an analytical signal; and an arctangent operation subunit for extracting the instantaneous phase term of the vibration phase information based on the analytical signal; the instantaneous phase term includes the vibration phase. With environmental slow-drift components The high-pass filter subunit is used to perform high-pass filtering on the instantaneous phase term, outputting a clean vibration phase. Wherein, the cutoff frequency of the high-pass filter subunit is... The lowest frequency component of the vibration to be measured .

[0013] To achieve another objective of the present invention, the present invention also provides an optical fiber vibration sensing method based on a swept-frequency interferometric self-generated carrier, implemented based on the aforementioned optical fiber vibration sensing system based on a swept-frequency interferometric self-generated carrier, comprising: Step 1: Generate a swept-frequency pulse optical signal whose frequency changes linearly with time through the swept-frequency optical pulse generation unit; Step 2: Inject a swept-frequency pulsed optical signal into a non-equidistant arm interferometer with a fixed optical path difference. The swept-frequency pulsed optical signal interferes with the time delay signal of the swept-frequency pulsed optical signal, automatically generating a beat frequency carrier signal. External vibrations act on the sensing arm, causing changes in the optical path, and the vibration phase is superimposed on the beat frequency carrier signal in the form of phase modulation, outputting an interferometric beat frequency optical signal carrying vibration phase information. The beat frequency carrier signal is generated spontaneously by the swept-frequency interference process, without the need for an additional carrier generation device. Step 3: The interferometric beat frequency optical signal carrying vibration phase information is converted into an electrical signal by the photoelectric signal conversion unit, and the analog-to-digital conversion is completed. Step 4: Demodulate the digitized beat frequency signal using a digital demodulation unit to extract the vibration phase information.

[0014] As an improvement to the above technical solution, the method further includes: adjusting the sweep frequency range of the sweep pulse optical signal. and / or pulse width Adjust the sweep rate of the sweep pulse optical signal. By adjusting the fixed arm length difference between the reference arm and the sensing arm of the non-equidistant arm interference unit. Change the fixed delay difference By adjusting the sweep rate of the sweep pulse optical signal. and / or fixed delay difference Change the beat frequency of the beat frequency carrier signal To achieve the beat frequency of the beat frequency carrier signal Flexible configuration.

[0015] As an improvement to the above technical solution, step 4 specifically includes: Step 4.1: Perform DC component removal processing on the digitized beat frequency signal to obtain the AC beat frequency signal; Step 4.2: Perform Hilbert transform on the AC beat frequency signal to construct an analytic signal; Step 4.3: Based on the analytical signal, extract the instantaneous phase term of the vibration phase information; the instantaneous phase term includes the vibration phase. With environmental slow-drift components ;and Step 4.4: Perform a high-pass filter on the instantaneous phase term to output a clean vibration phase. Wherein, the cutoff frequency of the high-pass filter The lowest frequency component of the vibration to be measured .

[0016] As an improvement to the above technical solution, the pulse repetition frequency of the swept-frequency pulse optical signal satisfy: ;in, The highest frequency component of the vibration to be measured is used to avoid spectral aliasing of the vibration signal; the repetition period of the swept pulse optical signal is... satisfy: ;in, For the number of sensing elements, The time delay between sensing elements is used to avoid aliasing of interference pulse signals corresponding to different sensing elements.

[0017] The advantages of this application are: 1. A self-generated carrier mechanism based on frequency sweeping interferometry is proposed, which uses the interference between the frequency sweeping pulse optical signal and its time delay signal to generate a beat frequency carrier, thereby realizing the measurement of interferometric vibration without the need for an external carrier generation device.

[0018] 2. It achieves single-channel digital demodulation without the need for a 3×3 coupler, three detectors, and three analog-to-digital converters; at the same time, it eliminates the need for ellipse fitting algorithms, resulting in low demodulation complexity.

[0019] 3. Especially suitable for engineering applications such as fiber optic hydrophones: No modulation depth control is required, which fundamentally solves the engineering problem of needing to periodically calibrate modulation depth drift in long-term deployment on the seabed using the PGC scheme; Compared with the frequency-shifted double-pulse heterodyne scheme, this invention uses a single sweep pulse to form a beat frequency carrier through non-equidistant arm interference, avoiding energy utilization loss caused by some pulse energy not participating in effective interference in the double-pulse structure. Attached Figure Description

[0020] Figure 1 A schematic diagram of the structural principle of the system provided by the present invention; Figure 2 This is a schematic diagram of the timing of the interference signal in this invention; Figure 3 This is a flowchart of the digital demodulation algorithm of the present invention. Detailed Implementation

[0021] The technical solutions provided in this application are further illustrated below with reference to the embodiments.

[0022] The applicant found that existing interferometric fiber optic vibration sensing schemes all require the introduction of an additional carrier wave. Among them, the demodulation performance of PGC is limited by modulation depth drift, the energy utilization of heterodyne demodulation schemes is low, and the cost of 3×3 coupler schemes is high. Overall, they face the technical bottleneck problem of being unable to balance demodulation simplicity, system stability and high energy utilization.

[0023] Example 1 To address the aforementioned technical problems, this embodiment proposes an optical fiber vibration sensing system based on a self-generated carrier wave using swept-frequency interferometry. The carrier wave self-generation mechanism, based on swept-frequency interferometry, directly generates a beat-frequency carrier wave through the interference of the swept-frequency pulse optical signal and its time delay signal. This beat-frequency carrier wave serves as the vibration phase information carrier, enabling high-sensitivity optical fiber interferometric vibration measurement. Compared to existing solutions, this invention features the advantages of eliminating the need for external carrier devices, utilizing full-pulse energy, and single-channel demodulation. The system is simplified while maintaining high stability and low cost.

[0024] This fiber optic vibration sensing system based on frequency sweeping interferometry self-generated carrier includes: A swept-frequency optical pulse generation unit is used to generate a swept-frequency pulse optical signal whose frequency varies linearly with time. The non-equidistant arm interference unit is connected to the output end of the sweep frequency optical pulse generation unit. It has a reference arm and a sensing arm with a fixed optical path difference between them. It is used to receive the sweep frequency pulse optical signal and automatically generate the beat frequency carrier signal by utilizing the interference between the sweep frequency pulse optical signal and its time delay signal. At the same time, it causes external vibrations to act on the beat frequency carrier signal in the form of phase modulation. The photoelectric conversion unit is connected to the output of the non-equidistant arm interference unit and is used to convert the interference beat frequency optical signal into an analog electrical signal and perform analog-to-digital conversion. The digital demodulation unit, connected to the output of the photoelectric conversion unit, is used to demodulate the digital beat frequency signal and extract vibration phase information.

[0025] Specifically, the frequency sweeping optical pulse generation unit includes a narrow linewidth laser and an acousto-optic modulator, or includes a narrow linewidth laser and an electro-optic modulator, or achieves linear frequency sweeping by directly modulating the injected current of a tunable laser.

[0026] Specifically, the non-equilateral interference unit is equipped with an adjustable optical delay line to adjust the fixed time delay difference between the reference arm and the sensing arm. This changes the beat frequency carrier frequency. .

[0027] Specifically, the digital demodulation unit is a field-programmable gate array or a digital signal processor, which internally executes a DC-DC converter, a Hilbert transform module, an arctangent operation module, and a high-pass filter module in sequence.

[0028] Specifically, the sensing arm of the non-equidistant interferometer unit is used to attach to the surface of the vibrating body being measured or to place it in the vibration field to be measured, so as to sense the change in optical path caused by external vibration.

[0029] The technical solution provided in this embodiment will be further described below with reference to the accompanying drawings. like Figure 1 As shown, this embodiment provides an optical fiber vibration sensing system based on frequency-sweeping interference self-generated carrier, including a light source 1, an acousto-optic modulator 2, a signal generator 3, a 2×2 optical fiber coupler 4, a 1×2 optical fiber coupler 5, a first Faraday rotator mirror 6, a second Faraday rotator mirror 7, a photoelectric conversion unit 8, an analog-to-digital converter 9, and a digital demodulation unit 10, wherein... The frequency-sweeping light generation unit includes a light source, a signal generator, and an acousto-optic modulator. The light source is a narrow-linewidth laser, and the signal generator drives the acousto-optic modulator to generate linearly frequency-modulated pulsed light with a pulse width of [missing information]. Frequency sweep range Sweep rate .

[0030] The non-equilateral interferometer unit employs a non-equilateral Michelson interferometer, consisting of a 1×2 fiber coupler, a reference arm fiber, a sensing arm fiber, and two Faraday rotators. A fixed arm length difference exists between the reference arm and the sensing arm. Corresponding time delay difference ,in, The refractive index of the optical fiber. The speed of light in a vacuum. After the swept-frequency pulse light is injected, the reflected light from the reference arm and the sensing arm interferes at the coupler, as shown... Figure 2 As shown, due to the linear change of the swept-frequency optical frequency and the fixed time delay difference between the reference arm and the sensing arm, a beat frequency carrier is generated, and its beat frequency satisfies: .

[0031] The optical fiber of the sensing arm is attached to the surface of the vibrating object being measured or placed in the vibration field. External vibrations cause changes in the length and refractive index of the optical fiber, thereby introducing vibration phase into the beat frequency signal. .

[0032] The photoelectric conversion unit uses a PIN photodetector to convert the interference beat frequency signal into an electrical signal, which is then sampled by an analog-to-digital converter (data acquisition card) and sent to the digital demodulation unit.

[0033] like Figure 3 As shown, the digital demodulation unit uses a field-programmable gate array or a digital signal processor to perform the following operations: (1) Remove the DC component from the digital beat frequency signal after analog-to-digital conversion to obtain the AC beat frequency signal; (2) Perform Hilbert transform on the AC beat frequency signal to construct an analytic signal; (3) Perform arctangent operation on the amplitude of the analytical signal to extract the instantaneous phase term containing vibration phase information. The instantaneous phase term contains the vibration phase. With environmental slow-drift components ; (4) High-pass filtering is applied to the instantaneous phase term, with its cutoff frequency set below the lowest frequency component of the vibration to be measured, in order to filter out slowly varying interferences such as ambient temperature changes and low-frequency noise, and finally output a pure vibration phase. .

[0034] It should be noted that the demodulation method of the present invention does not rely on precise control of the modulation depth, nor does it require three orthogonal signals or additional carrier synchronization circuits, and has the advantages of simple calculation and strong real-time performance.

[0035] System parameter design guidelines: Let the highest frequency of the vibration signal to be measured be... ,but: Repetition frequency of sweep pulse Should meet To avoid spectral aliasing of vibration signals, whereby, The highest frequency component of the vibration to be measured; Repetition period of sweep pulse Should meet To avoid aliasing between interference pulse signals, where The repetition period of the sweep pulse. For the number of sensing elements, The time delay between sensing primitives; Cutoff frequency of a high-pass filter It should be less than the lowest frequency component of the vibration being measured. In order to preserve complete vibration information.

[0036] As an alternative to the above embodiments, the frequency sweeping light generation unit can also achieve linear frequency scanning by using an electro-optic modulator or by directly modulating the current of a tunable laser.

[0037] As an alternative to the above embodiments, the non-equilateral interferometer unit is not limited to the Michelson interferometer, but can also be a non-equilateral Mach-Zehnder interferometer or a non-equilateral Fabry-Perot interferometer.

[0038] As an improvement to the above technical solution, by adjusting the sweep frequency rate (Change the sweep frequency range or pulse width) or adjust the arm length difference (For example, by adding an adjustable delay line), the shooting frequency can be flexibly changed. The vibration signal spectrum is shifted to a preset low-noise frequency band to further improve the signal-to-noise ratio.

[0039] This embodiment has at least the following advantages: 1. It does not rely on external carrier generation devices, simplifying the system structure; 2. No modulation depth drift issue, good long-term stability; 3. Full pulse energy utilization, high sensitivity; 4. Single-channel demodulation, low system cost; 5. The high-frequency carrier can be flexibly configured and has strong resistance to low-frequency noise; 6. The parameter design criteria are clear, and the project is highly feasible.

[0040] Example 2 This embodiment provides an optical fiber vibration sensing method based on frequency sweeping interferometry self-generated carrier, implemented based on the system provided in Embodiment 1, and includes the following steps: Step 1: Generate a frequency-sweeping pulse optical signal whose frequency changes with time according to a preset sweep frequency law; preferably, the sweep frequency law is a linear sweep frequency, and the sweep frequency rate is... ; Step 2: Inject the swept-frequency pulse optical signal into the non-equilateral interferometer. The non-equilateral interferometer has a reference arm and a sensing arm, and there is a fixed optical path difference between the reference arm and the sensing arm, corresponding to a fixed time delay difference. ; Step 3: In the non-equilateral interferometer, the swept pulse optical signal interferes with its time-delay signal, automatically generating a frequency of... Beat frequency carrier signal; Step 4: External vibrations act on the sensing arm, causing dynamic changes in the optical path length of the sensing arm, and the phase changes caused by the vibrations. It is superimposed on the beat frequency carrier signal in the form of phase modulation; Step 5: Obtain the beat frequency signal carrying vibration phase information Beat frequency signals carrying vibration phase information Single-channel photoelectric conversion and analog-to-digital conversion are performed to obtain a digital beat frequency signal; Step 6: Demodulate the digital beat frequency signal digitally and extract the vibration phase. The beat frequency carrier signal is generated automatically by the frequency sweeping interferometry process, eliminating the need for additional carrier generation devices, thus integrating carrier generation and vibration phase measurement; and the beat frequency carrier frequency... The sweep rate can be adjusted. and / or fixed delay difference Configure it to achieve active shifting of the vibration signal spectrum.

[0041] Specifically, digital demodulation in step 6 includes: Remove the DC component from the digital beat frequency signal; Perform a Hilbert transform on the signal after removing DC to construct an analytic signal; Perform arctangent operation on the analytical signal to extract the instantaneous phase term containing the vibration phase; High-pass filtering is applied to the instantaneous phase term to remove low-frequency ambient drift, thus obtaining the vibration phase. .

[0042] Specifically, the pulse repetition frequency of the swept pulse light satisfy: ,in, The highest frequency component of the vibration to be measured is denoted as .

[0043] Specifically, the repetition period of the swept pulse light With the number of sensing elements and the time delay between adjacent primitives Between This is to avoid aliasing of interference signals between adjacent pulses.

[0044] Specifically, the frequency sweep rate By changing the sweep frequency range of the sweep pulse and / or pulse width Adjustments are made to fix the time delay difference. By changing the difference in arm length between the reference arm and the sensing arm And / or connect a dimmable delay line for adjustment.

[0045] Specifically, the non-equilateral interferometer is any one of the Michelson interferometer, Mach-Zehnder interferometer, or Fabry-Perot interferometer.

[0046] It is important to note that this invention differs fundamentally from traditional Frequency-Modulated Continuous-Wave (FMCW) interferometry: FMCW interferometry uses the interference of continuously swept light with a time-delayed local oscillator to obtain distance / time delay information, and its beat frequency directly reflects the target distance; while this invention uses pulsed swept light with a fixed time delay difference of a non-equilateral interferometer to generate a carrier wave. This carrier wave is not the target itself, but rather serves as an information carrier for vibration phase modulation. The vibration information is extracted through phase demodulation rather than through frequency ranging. In other words, this invention transforms swept interferometry from a "ranging tool" to a "carrier generation tool," representing a fundamental change in the application mode of swept interferometry.

[0047] The core of the self-generated carrier mechanism based on frequency sweeping interferometry provided by this invention lies in the fact that the carrier is not actively injected by external devices, but rather the same frequency sweeping pulse interferes with two beams of light reflected from the two arms of a non-equilateral interferometer. Furthermore, the beat frequency is the product of the frequency sweeping rate and the time delay difference between the two arms of the interferometer, and this beat frequency serves as the carrier for subsequent phase demodulation. Therefore, this invention does not require any external carrier source or special coupling structure, and is a self-generated carrier mechanism. The essential differences between this invention and existing technologies are shown in Table 1 below: Table 1: Essential differences between the present invention and the prior art

[0048] The innovation of this invention lies not in making complex improvements to traditional phase demodulation algorithms, but in proposing a self-generated carrier mechanism based on swept-frequency interferometry. This mechanism automatically generates a beat-frequency carrier by utilizing the interference between the swept-frequency pulse optical signal and its time delay signal, and applies the phase change caused by external vibration to the beat-frequency carrier in the form of phase modulation, thereby realizing interferometric fiber vibration measurement without the need for additional carrier generation devices.

[0049] In summary, the fiber optic vibration sensing system and method based on sweep frequency interference self-generated carrier provided by this invention belongs to the field of fiber optic sensing technology. Addressing the problems of existing PGC demodulation relying on modulation depth stability, low energy utilization of heterodyne demodulation, and high complexity of 3×3 coupler systems, this invention utilizes the interference between the sweep frequency pulse optical signal and its time delay signal to generate a beat frequency carrier, eliminating the need for additional carrier generation devices. External vibrations are superimposed on the beat frequency signal in the form of phase modulation, and the vibration phase is extracted after single-channel photoelectric conversion and digital demodulation. The beat frequency carrier frequency is jointly determined by the sweep rate and the time delay difference and can be flexibly configured. This invention eliminates the need for modulation depth control, dual-pulse heterodyne structures, and 3×3 couplers, offering advantages such as high energy utilization, simple structure, good stability, low cost, and strong resistance to low-frequency noise. It is suitable for applications such as fiber optic hydrophones, marine acoustic monitoring, structural health monitoring, and distributed vibration sensing.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A fiber optic vibration sensing system based on swept-frequency interferometry self-generated carrier, comprising: A swept-frequency optical pulse generation unit is used to generate a swept-frequency pulse optical signal whose frequency varies linearly with time. The non-equidistant arm interference unit is connected to the output end of the frequency sweeping optical pulse generation unit; it has a reference arm and a sensing arm with a fixed optical path difference. It is used to receive swept pulse optical signals and automatically generate beat frequency carrier signals by utilizing the interference between the swept pulse optical signal and the time delay signal of the swept pulse optical signal; wherein, external vibration acts on the sensing arm to cause optical path change, so that the vibration phase is superimposed on the beat frequency carrier signal in the form of phase modulation, and outputs an interference beat frequency optical signal carrying vibration phase information. The photoelectric signal conversion unit, connected to the output of the non-equidistant arm interferometer, is used to convert the interferometric beat frequency optical signal carrying vibration phase information into an electrical signal and complete the analog-to-digital conversion; and The digital demodulation unit is used to demodulate the digitized beat frequency signal and extract the vibration phase information.

2. The fiber optic vibration sensing system based on frequency sweeping interferometry self-generated carrier as described in claim 1, characterized in that, The frequency sweeping optical pulse generation unit achieves linear frequency sweeping by using a narrow linewidth laser with an acousto-optic modulator, or a narrow linewidth laser with an electro-optic modulator, or by directly modulating the injection current of a tunable laser.

3. The fiber optic vibration sensing system based on frequency sweeping interferometry self-generated carrier as described in claim 1, characterized in that, The non-equilateral interference unit is any one of a Michelson interferometer, a Mach-Zehnder interferometer, or a Fabry-Perot interferometer.

4. The fiber optic vibration sensing system based on frequency sweeping interferometry self-generated carrier as described in claim 1, characterized in that, There is a fixed arm length difference between the reference arm and the sensing arm of the non-equidistant arm interference unit. The fixed time delay difference between the reference arm and the sensing arm satisfy: ； in, The refractive index of the optical fiber. The speed of light in a vacuum; The beat frequency of the beat frequency carrier signal satisfy: ； in, The sweep rate of the sweep pulse light; By changing the fixed time delay difference between the reference arm and the sensing arm and / or change the sweep rate of the sweep pulse light. Change the beat frequency of the beat frequency carrier signal To achieve the beat frequency of the beat frequency carrier signal Flexible configuration.

5. The fiber optic vibration sensing system based on frequency sweeping interferometry self-generated carrier as described in claim 4, characterized in that, The non-equidistant arm interference unit is equipped with an adjustable optical delay line to adjust the fixed time delay difference between the reference arm and the sensing arm. ; The frequency sweeping optical pulse generation unit changes the frequency sweeping range of the frequency sweeping pulse optical signal. and / or pulse width Adjust the sweep rate of the sweep pulse optical signal. .

6. The fiber optic vibration sensing system based on frequency sweeping interferometry self-generated carrier as described in claim 1, characterized in that, The photoelectric signal conversion unit is a single-channel photoelectric signal conversion unit, comprising: a PIN photodetector for converting interference beat frequency optical signals into electrical signals, and an analog-to-digital converter for analog-to-digital conversion; The digital demodulation unit is a single-channel digital demodulation unit; the digital demodulation unit internally integrates the following components in sequence: The DC component removal subunit is used to remove the DC component from the digitized beat frequency signal to obtain the AC beat frequency signal. The Hilbert transform subunit is used to perform Hilbert transform on the AC beat frequency signal to construct an analytical signal. The arctangent operation subunit extracts the instantaneous phase term of the vibration phase information based on the analytic signal; the instantaneous phase term includes the vibration phase. With environmental slow-drift components ;and The high-pass filter subunit is used to perform high-pass filtering on the instantaneous phase term, outputting a clean vibration phase. Wherein, the cutoff frequency of the high-pass filter subunit is... The lowest frequency component of the vibration to be measured .

7. A fiber optic vibration sensing method based on sweeping interferometry self-generated carrier, implemented based on the fiber optic vibration sensing system based on sweeping interferometry self-generated carrier as described in any one of claims 1-6, comprising: Step 1: Generate a swept-frequency pulse optical signal whose frequency changes linearly with time through the swept-frequency optical pulse generation unit; Step 2: Inject a swept-frequency pulsed optical signal into a non-equidistant arm interferometer with a fixed optical path difference. The swept-frequency pulsed optical signal interferes with the time delay signal of the swept-frequency pulsed optical signal, automatically generating a beat frequency carrier signal. External vibrations act on the sensing arm, causing changes in the optical path, and the vibration phase is superimposed on the beat frequency carrier signal in the form of phase modulation, outputting an interferometric beat frequency optical signal carrying vibration phase information. The beat frequency carrier signal is generated spontaneously by the swept-frequency interference process, without the need for an additional carrier generation device. Step 3: The interferometric beat frequency optical signal carrying vibration phase information is converted into an electrical signal by the photoelectric signal conversion unit, and the analog-to-digital conversion is completed. Step 4: Demodulate the digitized beat frequency signal using a digital demodulation unit to extract the vibration phase information.

8. The fiber optic vibration sensing method based on frequency sweeping interferometry self-generated carrier as described in claim 7, characterized in that, Also includes: By adjusting the sweep frequency range of the sweep pulse optical signal and / or pulse width Adjust the sweep rate of the sweep pulse optical signal. ; By adjusting the fixed arm length difference between the reference arm and the sensing arm of the non-equidistant arm interference unit Change the fixed delay difference ; By adjusting the sweep rate of the sweep pulse optical signal and / or fixed delay difference Change the beat frequency of the beat frequency carrier signal To achieve the beat frequency of the beat frequency carrier signal Flexible configuration.

9. The fiber optic vibration sensing method based on frequency sweeping interferometry self-generated carrier as described in claim 7, characterized in that, Step 4 specifically includes: Step 4.1: Perform DC component removal processing on the digitized beat frequency signal to obtain the AC beat frequency signal; Step 4.2: Perform Hilbert transform on the AC beat frequency signal to construct an analytic signal; Step 4.3: Based on the analytical signal, extract the instantaneous phase term of the vibration phase information; the instantaneous phase term includes the vibration phase. With environmental slow-drift components ;and Step 4.4: Perform a high-pass filter on the instantaneous phase term to output a clean vibration phase. Wherein, the cutoff frequency of the high-pass filter The lowest frequency component of the vibration to be measured .

10. The fiber optic vibration sensing method based on frequency sweeping interferometry self-generated carrier as described in claim 7, characterized in that, The pulse repetition frequency of the swept-frequency pulse optical signal satisfy: ； in, The highest frequency component of the vibration to be measured is used to avoid spectral aliasing of the vibration signal. The repetition period of the swept pulse optical signal satisfy: ； in, For the number of sensing elements, The time delay between sensing elements is used to avoid aliasing of interference pulse signals corresponding to different sensing elements.

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