High-speed optical fiber Fabry-Perot sensor demodulation method and system based on photon time stretching

Abstract

The invention relates to a high-speed optical fiber Fabry-Perot sensor demodulation method and system based on photon time stretching. The method comprises the following steps: emitting a broadband pulse light signal through a pulse broadband light source; transmitting the broadband pulse optical signal to an optical fiber Fabry-Perot sensor, sensing physical quantity by the optical fiber Fabry-Perot sensor, and generating a frequency domain Fabry-Perot interference signal containing cavity length information; transmitting the frequency domain Fabry-Perot interference signal to a time stretching element, and mapping the frequency domain Fabry-Perot interference signal from a frequency domain to a time domain to obtain a time domain Fabry-Perot interference signal; performing photoelectric conversion and acquisition on the time domain Fabry-Perot interference signal to obtain a digital electric signal; and tracking the time domain characteristic change of the time domain Fabry-Perot interference signal, and demodulating the cavity length of the optical fiber Fabry-Perot sensor. According to the method, high precision of frequency domain interference and high speed of time domain acquisition are combined, and Doppler errors in dynamic measurement are avoided, so that high-speed, high-precision and high-dynamic demodulation of the cavity length of the optical fiber Fabry-Perot sensor is realized.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing technology, specifically relating to a fiber optic Fabry-Perot sensor demodulation method and system based on photonic time stretching technology, suitable for high-speed dynamic measurement. Background Technology

[0002] A fiber optic Fabry-Perot sensor is a miniature sensor with a Fabry-Perot cavity built on an optical fiber. When an external physical quantity (such as vibration, pressure, or displacement) acts on the Fabry-Perot cavity, it causes a change in the optical path difference of the interference within the cavity. By detecting and analyzing this optical path difference, the corresponding physical quantity can be sensed and measured. Especially in high-frequency, dynamically changing physical fields, the Fabry-Perot cavity causes rapid changes in the interference optical path difference. Therefore, accurately demodulating the Fabry-Perot cavity length becomes a core issue in achieving high-speed physical quantity measurement.

[0003] Traditional demodulation techniques have many limitations. White light interferometry and peak tracking methods cannot meet the growing demand for high-frequency dynamic measurements due to limitations in spectrometer resolution and spectral acquisition rate. High-speed ranging methods widely used in industry include multi-wavelength interferometry, but these suffer from phase errors during dynamic measurements, struggle to cope with imbalances and disturbances caused by different optical paths, and are limited by half-wavelength variations in the measured distance. To expand the measurement range, phase-generated carrier methods based on two orthogonal signals have been developed. Laser-modulated phase-generated carrier methods are compact, maintain strong electromagnetic interference resistance, and can achieve high phase sampling rates, but their data processing is relatively complex. Frequency-modulated continuous wave radar (FMCW) and frequency-swept interferometry are a widely used class of measurement methods. In these methods, the frequency of the optical signal changes with time, achieving a mapping from the frequency domain to the time domain during signal generation, offering advantages such as high measurement accuracy, high resolution, and strong anti-interference capabilities. However, during dynamic measurement, the target under test will move within one frequency sweep cycle, causing the received interference signal to have the Doppler frequency domain, which will cause measurement error.

[0004] Therefore, existing technologies lack a dynamic demodulation scheme for fiber optic Fabry-Perot sensors that can simultaneously achieve high speed, high precision, and effectively avoid dynamic errors. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fiber optic Fabry-Perot sensor demodulation method and system based on photonic time stretching technology, suitable for high-speed dynamic measurement. It maps the frequency domain Fabry-Perot interference signal to the time domain at high speed for acquisition, combining the high precision of frequency domain interference with the high speed of time domain acquisition, while avoiding Doppler error in dynamic measurement, thereby achieving high-speed, high-precision, and high-dynamic demodulation of the fiber optic Fabry-Perot sensor cavity length.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a high-speed fiber optic Fabry-Perot sensor demodulation method based on photon time stretching, comprising the following steps:

[0007] Step S1: Emit broadband pulsed light signals through a broadband pulsed light source;

[0008] Step S2: The broadband pulsed optical signal is transmitted to the fiber optic Fabry-Perot sensor, which senses physical quantities and generates a frequency domain Fabry-Perot interference signal containing cavity length information.

[0009] Step S3: The frequency domain Fabry-Perot interference signal is transmitted to a time stretching element, which maps the frequency domain Fabry-Perot interference signal from the frequency domain to the time domain to obtain a time-domain broadened Fabry-Perot interference signal;

[0010] Step S4: Perform photoelectric conversion and acquisition on the time-domain Fabry-Perot interferometric signal to obtain the corresponding digital electrical signal;

[0011] Step S5: Process the digital electrical signal, track the time-domain characteristic changes of the time-domain Fabry-Perot interference signal, and demodulate the cavity length of the fiber optic Fabry-Perot sensor.

[0012] Furthermore, in step S1, the demodulation rate of the demodulation method is the repetition frequency of the pulse broadband light source. By increasing the repetition frequency of the pulse broadband light source, a higher demodulation rate can be obtained.

[0013] Furthermore, in step S3, the time stretching element utilizes the group velocity dispersion effect to map the frequency domain Fabry-Perot interference signal from the frequency domain to the time domain.

[0014] Furthermore, the time stretching element is a dispersion-compensating fiber or a chirped Bragg grating.

[0015] Furthermore, in step S4, the cavity length of the fiber optic Fabry-Perot sensor is demodulated by tracking the temporal position changes of the peaks or troughs of the time-domain Fabry-Perot interference signal.

[0016] Furthermore, let the broadband pulsed optical signal be I0. When the broadband pulsed optical signal reaches the fiber optic Fabry-Perot sensor under test, it generates a frequency-domain Fabry-Perot interference signal and returns to the optical path. The expression for the frequency-domain Fabry-Perot interference signal is:

[0017] (1)

[0018] in, The signal is a frequency domain Fabry-Perot interference signal, L is the length of the Fabry-Perot cavity to be measured, the interference optical path difference is 2L, ω is the angular frequency, ω=2πυ, υ is the optical frequency, φ1 is the initial phase, and ω0 is the center angular frequency.

[0019] Then, the frequency-domain Fabry-Perot interference signal is transmitted to a time-stretching element, which uses group velocity dispersion to map the frequency-domain Fabry-Perot interference signal from the optical frequency domain to the time domain; the expression for the frequency-domain Fabry-Perot interference signal after photon time stretching is:

[0020] (2)

[0021] in, The signal is the frequency domain Fabry-Perot interference signal after photonic time stretching, where β2 is the second-order group dispersion coefficient of the time-stretching element, and L... DCF The length of the stretching element is determined by time;

[0022] According to equation (2), the output time-domain Fabry-Perot interference signal is obtained through inverse Fourier transform, and its expression is:

[0023] (3)

[0024] Where t is time; according to equation (3), the relationship between angular frequency and time is:

[0025] (4)

[0026] When the length of the Fabry-Perot cavity under test changes, the change in the time-domain position of the interference trough can be tracked to achieve cavity length demodulation; specifically:

[0027] If the distance oscillates in the form of a sinusoidal signal, then the expression for the distance is:

[0028] (5)

[0029] Where L(t) is the distance, L0 is the initial distance, A is the vibration amplitude, and f L The vibration frequency;

[0030] When the repetition frequency of the pulse broadband light source, i.e., the measurement rate, is determined, the tracking formula is used. The changes in the valleys of the time-domain interference spectrum can be observed, thus demodulating the changes in distance and achieving cavity length demodulation.

[0031] The present invention also provides a high-speed fiber optic Fabry-Perot sensor demodulation system based on photon time stretching for implementing the above method, characterized in that it comprises:

[0032] A pulsed broadband light source is used to generate and output broadband pulsed light signals;

[0033] A fiber optic Fabry-Perot sensor is connected to the output optical path of the pulsed broadband light source and is used to receive the broadband pulsed optical signal and generate a frequency domain Fabry-Perot interference signal.

[0034] A time-stretching element is connected to the output optical path of the fiber optic Fabry-Perot sensor, used to receive the frequency-domain Fabry-Perot interference signal and map it from the frequency domain to the time domain, and output a time-domain Fabry-Perot interference signal;

[0035] A photodetector, connected to the output of the time stretching element, is used to receive the time-domain Fabry-Perot interference signal and convert it into an analog electrical signal;

[0036] A data acquisition unit, connected to the photodetector, is used to convert the analog electrical signal into a digital electrical signal;

[0037] The processing unit, connected to the data acquisition unit, is used to process the digital electrical signal to demodulate the cavity length of the fiber optic Fabry-Perot sensor.

[0038] Furthermore, the demodulation system also includes a circulator, the first port of which is connected to the pulsed broadband light source, the second port of which is connected to the fiber optic Fabry-Perot sensor, and the third port of which is connected to the input of the time stretching element. The circulator is used to guide the broadband pulsed light signal emitted by the pulsed broadband light source to the fiber optic Fabry-Perot sensor and to guide the frequency domain Fabry-Perot interference signal generated by the fiber optic Fabry-Perot sensor to the time stretching element.

[0039] Furthermore, the pulsed broadband light source is a pulsed laser with an adjustable repetition frequency, where the repetition frequency is the demodulation rate of the demodulation method, and the pulsed laser can obtain a higher demodulation rate by changing the repetition frequency.

[0040] Furthermore, the time stretching element is a dispersion-compensating fiber or a chirped Bragg grating.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. High demodulation rate: The measurement rate of this invention is directly determined by the repetition frequency of the pulse broadband light source. By using a pulse laser with a high repetition frequency, real-time demodulation of the corresponding rate can be achieved, breaking through the limitation of the acquisition rate of traditional spectrometers.

[0043] 2. High measurement accuracy: This invention is based on the principle of full-spectrum interferometry demodulation and utilizes all spectral information of broadband light sources for calculation, thus retaining the inherent high-precision advantage of frequency domain interferometry.

[0044] 3. Strong resistance to dynamic errors: The time stretching process of this invention occurs after sensing, and the interference signal generated by the sensor is static in the frequency domain. It is then stretched onto the time axis for observation through dispersion. This differs from the principle of simultaneous time-domain change of the light source frequency and the sensing process in the frequency sweeping interferometry, thus avoiding Doppler frequency shift errors caused by the movement of the measured target within the frequency sweeping period. It is particularly suitable for high-speed, high-acceleration dynamic measurement scenarios.

[0045] 4. Simple and reliable structure: The optical path structure of this system is simple and mainly uses mature fiber optic devices. It has good stability, strong anti-electromagnetic interference ability, is easy to implement and stable and reliable in use. Attached Figure Description

[0046] Figure 1 This is a schematic diagram illustrating the implementation principle of the high-speed fiber optic Fabry-Perot sensor demodulation method and system based on photon time stretching provided in this embodiment of the invention.

[0047] Figure 2 This is a schematic diagram of the photon time stretching principle in an embodiment of the present invention;

[0048] Figure 3 These are Fabry-Perot interference signal diagrams before and after photon time stretching in this embodiment of the invention;

[0049] Figure 4 This is a cavity length demodulation sensitivity diagram in an embodiment of the present invention;

[0050] Figure 5 This is a simulation demodulation result diagram in an embodiment of the present invention. Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0053] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0054] like Figure 1 As shown, this embodiment provides a high-speed fiber optic Fabry-Perot sensor demodulation method based on photon time stretching, including the following steps:

[0055] Step S1: Emit broadband pulsed light signals through a pulsed broadband light source.

[0056] The repetition frequency of the pulse broadband light source is the demodulation rate of the demodulation method. A higher demodulation rate can be obtained by increasing the repetition frequency of the pulse broadband light source.

[0057] Step S2: The broadband pulsed optical signal is transmitted to the fiber optic Fabry-Perot sensor, which senses physical quantities and generates a frequency domain Fabry-Perot interference signal containing cavity length information.

[0058] Step S3: The frequency domain Fabry-Perot interference signal is transmitted to a time stretching element, which maps the frequency domain Fabry-Perot interference signal from the frequency domain to the time domain to obtain a time-domain broadened Fabry-Perot interference signal.

[0059] Step S4: Perform photoelectric conversion and acquisition on the time-domain Fabry-Perot interferometric signal to obtain the corresponding digital electrical signal.

[0060] Specifically, the cavity length of the fiber optic Fabry-Perot sensor can be demodulated by tracking the temporal position changes of the peaks or troughs of the time-domain Fabry-Perot interference signal.

[0061] Step S5: Process the digital electrical signal, track the time-domain characteristic changes of the time-domain Fabry-Perot interference signal, and demodulate the cavity length of the fiber optic Fabry-Perot sensor.

[0062] like Figure 1 As shown, this embodiment also provides a high-speed fiber optic Fabry-Perot sensor demodulation system for implementing the above method, characterized in that it includes: a pulse broadband light source, a fiber optic Fabry-Perot sensor, a time stretching element, a circulator, a photodetector, a data acquisition unit, and a processing unit.

[0063] The pulsed broadband light source is used to generate and output broadband pulsed optical signals. The pulsed broadband light source can be a pulsed laser with a high repetition rate or a pulsed laser with an adjustable repetition rate, and a higher demodulation rate can be obtained by changing the repetition rate of the pulsed laser.

[0064] The fiber optic Fabry-Perot sensor is connected to the output optical path of the pulsed broadband light source and is used to receive the broadband pulsed optical signal and generate a frequency domain Fabry-Perot interference signal.

[0065] The time stretching element is connected to the output optical path of the fiber optic Fabry-Perot sensor, and is used to receive the frequency domain Fabry-Perot interference signal and map it from the frequency domain to the time domain, and output the time domain Fabry-Perot interference signal.

[0066] The time stretching element can be a dispersion-compensating fiber, a chirped Bragg grating, or the like. In this embodiment, a dispersion-compensating fiber is used.

[0067] The circulator's first port is connected to the pulsed broadband light source, its second port is connected to the fiber optic Fabry-Perot sensor, and its third port is connected to the input of the time-stretching element. This is used to guide the broadband pulsed light signal emitted by the pulsed broadband light source to the fiber optic Fabry-Perot sensor and to guide the frequency domain Fabry-Perot interference signal generated by the fiber optic Fabry-Perot sensor to the time-stretching element.

[0068] The photodetector is connected to the output of the time stretching element and is used to receive the time-domain Fabry-Perot interference signal and convert it into an analog electrical signal.

[0069] The data acquisition unit is connected to the photodetector and is used to convert the analog electrical signal into a digital electrical signal.

[0070] The processing unit (host computer) is connected to the data acquisition unit and is used to process the digital electrical signal to demodulate the cavity length of the fiber optic Fabry-Perot sensor.

[0071] The implementation principle of the present invention will be further explained below through specific embodiments.

[0072] like Figure 1 As shown, the basic principle of this method and system is as follows: a pulsed laser emits a broadband pulsed optical signal, such as... Figure 1 As shown in (a), the signal is a pulse signal in the time domain and a broadband signal in the wavelength domain. The optical signal reaches the target (fiber optic Fabry-Perot sensor) through the circulator, is reflected back into the fiber by the target, and generates a wavelength domain interference signal, such as... Figure 1 As shown in (b), the signal remains a pulse signal in the time domain. The measurement signal passes through a circulator to the dispersion-compensating fiber, which has a photon time-stretching effect, enabling a one-to-one mapping from the wavelength domain to the time domain. At this point, the measurement signal is an interference signal in both the time and wavelength domains, as shown in (b). Figure 1 As shown in (c), the stretched time-domain interference signal is detected and acquired by the PD and DAQ, and then transmitted to the host computer for data processing. The specific implementation process is described below.

[0073] Let the broadband pulsed optical signal be I0. When the broadband pulsed optical signal reaches the fiber optic Fabry-Perot sensor under test, it generates a frequency-domain Fabry-Perot interference signal and returns to the optical path. The expression for the frequency-domain Fabry-Perot interference signal is:

[0074] (1)

[0075] in, The signal is a frequency domain Fabry-Perot interference signal, L is the length of the Fabry-Perot cavity to be measured, the interference optical path difference is 2L, ω is the angular frequency, ω=2πυ, υ is the optical frequency, φ1 is the initial phase, and ω0 is the center angular frequency.

[0076] Then, the frequency-domain Fabry-Perot interference signal is transmitted to the time-stretching element. In this embodiment, the time-stretching element is a dispersion-compensating fiber. The dispersion-compensating fiber utilizes group velocity dispersion to map the frequency-domain Fabry-Perot interference signal from the optical frequency domain to the time domain, such as... Figure 2 As shown, the mapped signal has a time-domain broadening effect, and tracking the phase change of the time-domain interference signal can improve measurement sensitivity.

[0077] The expression for the frequency domain Fabry-Perot interference signal after photon time stretching is:

[0078] (2)

[0079] in, The signal is the frequency domain Fabry-Perot interference signal after photonic time stretching, where β2 is the second-order group dispersion coefficient of the time-stretching element, and L... DCF The length of the stretching element is determined by time.

[0080] According to equation (2), the output time-domain Fabry-Perot interference signal is obtained through inverse Fourier transform, and its expression is:

[0081] (3)

[0082] Where t is time.

[0083] According to equation (3), the relationship between angular frequency and time is:

[0084] (4)

[0085] Figure 3 This is a Fabry-Perot interference signal diagram before and after photon time stretching in this embodiment. Figure 3 (a) shows the wavelength-domain Fabry-Perot interference signal before photon time stretching; Figure 3 (b) shows the time-domain Fabry-Perot interference signal after photon time stretching. In this embodiment, L = 800 μm, β2 = 21.35 ps 2 / km, L DCF=40 km, ω=1204.4~1227.8 THz∙rad.

[0086] When the length of the Fabry-Perot cavity under test changes, the time-domain position change of the interference trough can be tracked to achieve cavity length demodulation. For example, when the length of the Fabry-Perot cavity under test changes, the position of the trough near the -2 ns location can be tracked. Figure 4 As shown, the sensitivity reaches 13×10 -4 s / m.

[0087] Suppose that the distance vibrates in the form of a sinusoidal signal to simulate a motion pattern in which velocity and acceleration change instantaneously. The expression for distance in this case is:

[0088] (5)

[0089] Where L(t) is the distance, L0 is the initial distance, A is the vibration amplitude, and f L The frequency is the vibration frequency.

[0090] Figure 5 This is the simulation demodulation result diagram in this embodiment (f) L =2 kHz, A=3 μm, L0=800 μm). When the repetition frequency of the pulse broadband light source, i.e. the measurement rate, is 2.5 MHz, the change of the time-domain interference spectrum trough in the tracking formula (3) is as follows. Figure 5 As shown in (a). By combining the measurement sensitivity and the initial distance, the change in distance can be demodulated, as shown in (a). Figure 5 As shown in Figure 5(b), the demodulation error is shown in Figure 5(c).

[0091] To achieve high-speed dynamic demodulation of fiber optic Fabry-Perot sensors, this invention proposes a novel high-speed fiber optic Fabry-Perot sensor demodulation method and system based on photonic time stretching. This invention innovatively applies time stretching to the field of fiber optic Fabry-Perot sensor demodulation, employing a broadband pulsed laser to increase the demodulation rate to the laser's repetition frequency. The time-stretching element then maps the frequency-domain Fabry-Perot interference signal to the time domain after the sensing process, avoiding Doppler errors during dynamic sensing. Therefore, this invention combines the advantages of high-speed time-domain acquisition and high-precision frequency-domain interferometric demodulation, possessing both the high precision of frequency-domain interferometric demodulation and the high speed of time-domain acquisition, demonstrating strong practicality and broad application prospects.

[0092] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0093] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0094] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0095] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A demodulation method for a high-speed fiber optic Fabry-Perot sensor based on photon time stretching, characterized in that, Includes the following steps: Step S1: Emit broadband pulsed light signals through a broadband pulsed light source; Step S2: The broadband pulsed optical signal is transmitted to the fiber optic Fabry-Perot sensor, which senses physical quantities and generates a frequency domain Fabry-Perot interference signal containing cavity length information. Step S3: The frequency domain Fabry-Perot interference signal is transmitted to a time stretching element, which maps the frequency domain Fabry-Perot interference signal from the frequency domain to the time domain to obtain a time-domain broadened Fabry-Perot interference signal; Step S4: Perform photoelectric conversion and acquisition on the time-domain Fabry-Perot interferometric signal to obtain the corresponding digital electrical signal; Step S5: Process the digital electrical signal, track the time-domain characteristic changes of the time-domain Fabry-Perot interference signal, and demodulate the cavity length of the fiber optic Fabry-Perot sensor.

2. The high-speed fiber optic Fabry-Perot sensor demodulation method based on photon time stretching according to claim 1, characterized in that, In step S1, the demodulation rate of the demodulation method is the repetition frequency of the pulse broadband light source. A higher demodulation rate can be obtained by increasing the repetition frequency of the pulse broadband light source.

3. The high-speed fiber optic Fabry-Perot sensor demodulation method based on photon time stretching according to claim 1, characterized in that, In step S3, the time stretching element utilizes the group velocity dispersion effect to map the frequency domain Fabry-Perot interference signal from the frequency domain to the time domain.

4. The high-speed fiber optic Fabry-Perot sensor demodulation method based on photon time stretching according to claim 3, characterized in that, The time stretching element is a dispersion-compensating fiber or a chirped Bragg grating.

5. The high-speed fiber optic Fabry-Perot sensor demodulation method based on photon time stretching according to claim 1, characterized in that, In step S4, the cavity length of the fiber optic Fabry-Perot sensor is demodulated by tracking the temporal position changes of the peaks or troughs of the time-domain Fabry-Perot interference signal.

6. The high-speed fiber optic Fabry-Perot sensor demodulation method based on photon time stretching according to claim 1, characterized in that, set up The broadband pulsed optical signal is I0. When the broadband pulsed optical signal reaches the fiber optic Fabry-Perot sensor under test, it generates a frequency-domain Fabry-Perot interference signal and returns to the optical path. The expression for the frequency-domain Fabry-Perot interference signal is: (1) in, The signal is a frequency domain Fabry-Perot interference signal, L is the length of the Fabry-Perot cavity to be measured, the interference optical path difference is 2L, ω is the angular frequency, ω=2πυ, υ is the optical frequency, φ1 is the initial phase, and ω0 is the center angular frequency. Then, the frequency-domain Fabry-Perot interference signal is transmitted to a time-stretching element, which uses group velocity dispersion to map the frequency-domain Fabry-Perot interference signal from the optical frequency domain to the time domain; the expression for the frequency-domain Fabry-Perot interference signal after photon time stretching is: (2) in, The signal is the frequency domain Fabry-Perot interference signal after photonic time stretching, where β2 is the second-order group dispersion coefficient of the time-stretching element, and L... DCF The length of the stretching element is determined by time; According to equation (2), the output time-domain Fabry-Perot interference signal is obtained through inverse Fourier transform, and its expression is: (3) Where t is time; according to equation (3), the relationship between angular frequency and time is: (4) When the length of the Fabry-Perot cavity under test changes, the change in the time-domain position of the interference trough can be tracked to achieve cavity length demodulation; specifically: If the distance oscillates in the form of a sinusoidal signal, then the expression for the distance is: (5) Where L(t) is the distance, L0 is the initial distance, A is the vibration amplitude, and f L The vibration frequency; When the repetition frequency of the pulse broadband light source, i.e., the measurement rate, is determined, the tracking formula is used. The changes in the valleys of the time-domain interference spectrum can be observed, thus demodulating the changes in distance and achieving cavity length demodulation.

7. A high-speed fiber optic Fabry-Perot sensor demodulation system based on photonic time stretching for implementing the method as described in any one of claims 1-6, characterized in that, include: A pulsed broadband light source is used to generate and output broadband pulsed light signals; A fiber optic Fabry-Perot sensor is connected to the output optical path of the pulsed broadband light source and is used to receive the broadband pulsed optical signal and generate a frequency domain Fabry-Perot interference signal. A time-stretching element is connected to the output optical path of the fiber optic Fabry-Perot sensor, used to receive the frequency-domain Fabry-Perot interference signal and map it from the frequency domain to the time domain, and output a time-domain Fabry-Perot interference signal; A photodetector, connected to the output of the time stretching element, is used to receive the time-domain Fabry-Perot interference signal and convert it into an analog electrical signal; A data acquisition unit, connected to the photodetector, is used to convert the analog electrical signal into a digital electrical signal; The processing unit, connected to the data acquisition unit, is used to process the digital electrical signal to demodulate the cavity length of the fiber optic Fabry-Perot sensor.

8. The high-speed fiber optic Fabry-Perot sensor demodulation system based on photon time stretching according to claim 7, characterized in that, The demodulation system further includes a circulator, with a first port connected to the pulsed broadband light source, a second port connected to the fiber optic Fabry-Perot sensor, and a third port connected to the input of the time stretching element. The circulator is used to guide the broadband pulsed light signal emitted by the pulsed broadband light source to the fiber optic Fabry-Perot sensor and to guide the frequency domain Fabry-Perot interference signal generated by the fiber optic Fabry-Perot sensor to the time stretching element.

9. The high-speed fiber optic Fabry-Perot sensor demodulation system based on photon time stretching according to claim 7, characterized in that, The pulsed broadband light source is a pulsed laser with an adjustable repetition frequency. The repetition frequency is the demodulation rate of the demodulation method. The pulsed laser can obtain a higher demodulation rate by changing the repetition frequency.

10. The high-speed fiber optic Fabry-Perot sensor demodulation system based on photon time stretching according to claim 7, characterized in that, The time stretching element is a dispersion-compensating fiber or a chirped Bragg grating.

Images