Absolute pressure sensor based on f-p cavity structure and air pressure detection method

Abstract

This application provides an absolute pressure sensor with an F-P cavity structure and a method for detecting air pressure. The absolute pressure sensor includes: a light source module for linearly modulating the received external sawtooth wave modulation signal to output continuous laser light; an optical fiber transmission module for unidirectional transmission of the continuous laser light to block the reflected light of the continuous laser light from returning to the light source module; an F-P interference cavity including an exit surface of an optical fiber collimator coated with a low-reflectivity film and a total reflection mirror fixed on a pressure-sensitive elastic element. The pressure-sensitive elastic element senses changes in air pressure and deforms, causing the total reflection mirror to shift. The continuous laser light is reflected on the exit surface and the total reflection mirror to form coherent light, generating a beat frequency optical signal carrying air pressure information; a photoelectric detection module for processing the beat frequency optical signal carrying air pressure information transmitted via the optical fiber transmission module to obtain an electrical signal that meets demodulation requirements; and a signal demodulation module for processing the electrical signal that meets demodulation requirements to obtain the air pressure value.

Description

Technical Field

[0001] This application relates to the field of absolute gas pressure measurement technology, and in particular to an absolute pressure sensor based on an FP cavity structure and a gas pressure detection method. Background Technology

[0002] The demand for high-precision and high-stability absolute pressure measurement is becoming increasingly urgent in fields such as atmospheric physics detection and monitoring of minute atmospheric pressure fluctuations (micro-pressure fluctuations). However, the electrical sensor hardware for high-precision absolute pressure measurement is expensive and has poor resistance to electromagnetic interference and corrosion, making it difficult to meet the application requirements of large-scale networking and complex environments.

[0003] Fiber optic Fabry-Perot (FP) pressure sensors have become the preferred alternative in absolute pressure measurement due to their advantages of electromagnetic interference resistance, corrosion resistance, small size, and controllable manufacturing costs. Among related technologies, demodulation methods have significant technical limitations in absolute pressure detection applications, failing to simultaneously meet the core requirements of high accuracy and low cost: intensity demodulation systems are simple in structure and low in cost, but the measurement results are easily affected by external factors such as fluctuations in light source power and changes in ambient temperature and humidity, resulting in large demodulation errors; while spectral peak tracking demodulation offers excellent stability and resolution, it requires an expensive spectrometer, significantly increasing the overall system cost. Summary of the Invention

[0004] In view of this, this application provides an absolute pressure sensor and a pressure detection method based on an FP cavity structure, which at least partially solves the above-mentioned technical problems.

[0005] One embodiment of this application provides an absolute pressure sensor with an FP cavity structure, comprising: a light source module for linearly modulating a received external sawtooth wave modulation signal to output continuous laser light; an optical fiber transmission module for unidirectional transmission of the continuous laser light to block the reflected light of the continuous laser light from returning to the light source module; an FP interferometer cavity including an exit surface of an optical fiber collimator coated with a low-reflectivity film and a total reflection mirror fixed on a pressure-sensitive elastic element, the pressure-sensitive elastic element for sensing changes in air pressure and deforming to drive the total reflection mirror to shift, the continuous laser light being reflected on the exit surface and the total reflection mirror to form coherent light, generating a beat frequency optical signal carrying air pressure information; a photoelectric detection module for processing the beat frequency optical signal carrying air pressure information transmitted via the optical fiber transmission module to obtain an electrical signal that meets demodulation requirements; and a signal demodulation module for processing the electrical signal that meets demodulation requirements to obtain an air pressure value.

[0006] According to an embodiment of this application, the pressure-sensitive elastic element includes a vacuum diaphragm, and the axial deformation of the vacuum diaphragm is linearly related to the trend of pressure change.

[0007] According to embodiments of this application, the number of vacuum diaphragms is one or more, and the sensitivity and resolution of the FP interferometer cavity are related to the number of vacuum diaphragms.

[0008] According to an embodiment of this application, the precision of the FP interferometer cavity is positively correlated with the reflectivity of the low-reflectivity film, which has a reflectivity of 0.05 to 0.3.

[0009] According to an embodiment of this application, the FP interferometer cavity further includes: an FP cavity mounting frame; a collimator mounting hole installed at one end of the FP cavity mounting frame; a fiber collimator coated with a low reflectivity film installed in the collimator mounting hole; a pressure-sensitive elastic element installed at the other end of the FP cavity mounting frame; and a total reflection mirror installed at the center of the pressure-sensitive elastic element. The surface of the total reflection mirror is perpendicular to the output optical axis of the fiber collimator coated with a low reflectivity film and parallel to the output surface of the fiber collimator coated with a low reflectivity film.

[0010] According to an embodiment of this application, the light source module includes: a distributed feedback laser, the center wavelength of which needs to match the optical fiber transmission band, and the working mode is set to external modulation mode; the distributed feedback laser is connected to an external digital signal generator through a shielded cable.

[0011] According to an embodiment of this application, the optical fiber transmission module includes: a 1×3 port optical fiber circulator, with the first port connected to the output optical fiber of the light source module, the second port connected to the input optical fiber of the FP interferometer cavity, and the third port connected to the input optical fiber of the photoelectric detection module.

[0012] According to an embodiment of this application, the photoelectric detection module includes: a photoelectric detector for converting a beat frequency optical signal carrying air pressure information into an electrical signal; and a signal amplification circuit for amplifying the electrical signal to obtain an electrical signal that meets demodulation requirements.

[0013] According to an embodiment of this application, the signal demodulation module includes: an analog-to-digital converter for converting an electrical signal that meets demodulation requirements into a digital beat frequency signal; an embedded demodulation unit for generating an orthogonal cosine signal and an orthogonal sine signal based on the digital beat frequency signal; mixing the digital beat frequency signal with the orthogonal cosine signal and the orthogonal sine signal respectively to obtain a first mixed signal and a second mixed signal; applying a low-pass filter with a cutoff frequency lower than the sawtooth wave modulation frequency to the first mixed signal and the second mixed signal respectively to filter out high-frequency noise and retain the baseband component carrying phase information to obtain a first filtered signal and a second filtered signal; determining the interference phase value of the FP interferometer based on the first filtered signal and the second filtered signal; and determining the air pressure value based on the interference phase value.

[0014] Another embodiment of this application provides a barometric pressure detection method based on the absolute pressure sensor of this application. The barometric pressure detection method includes: activating a light source module to perform frequency linear modulation on a received external sawtooth wave modulation signal and output continuous laser; transmitting the continuous laser unidirectionally to an FP interferometer cavity through an optical fiber transmission module, so that the continuous laser is reflected on the exit surface and the total reflection mirror to form coherent light, generating a beat frequency optical signal carrying barometric pressure information; processing the beat frequency optical signal carrying barometric pressure information transmitted through the optical fiber transmission module using a photoelectric detection module to obtain an electrical signal that meets the demodulation requirements; and processing the electrical signal that meets the demodulation requirements using a signal demodulation module to obtain a barometric pressure value.

[0015] The absolute pressure sensor and pressure detection method based on the FP cavity structure provided in this application have at least the following technical advantages:

[0016] A frequency-modulated continuous wave (FM) interferometer cavity is formed by an optical fiber collimator exit surface coated with a low-reflectivity film and a total reflection mirror fixed on a pressure-sensitive elastic element. Continuous laser light modulated by the light source module is reflected at the two reflective surfaces of the FM interferometer cavity to form coherent light, generating a beat-frequency optical signal carrying pressure information. This method of pressure detection using FM continuous wave interferometry combined with an optical fiber FM absolute pressure sensor eliminates the need for expensive spectrometers, significantly reducing system hardware costs and achieving a balance between high precision and low cost.

[0017] A vacuum diaphragm is used as a pressure-sensitive elastic element. By sensing changes in external absolute air pressure and generating axial deformation, it drives the total reflection mirror to shift, thereby changing the cavity length of the FP cavity and realizing the conversion of the air pressure signal into an interference light phase modulation signal. Furthermore, by selecting a single vacuum diaphragm or a diaphragm group composed of multiple vacuum diaphragms connected in series as the pressure-sensitive elastic element, the sensor sensitivity can be flexibly adjusted.

[0018] The absolute pressure sensor's modules are connected by optical fibers, making it small and compact. The low-precision FP cavity consists of a collimator and a reflector fixed on the diaphragm, which is simple to manufacture and does not require complex micro-machining processes. The detection method uses an embedded demodulation unit to achieve integrated algorithm operation, enabling portable deployment and facilitating large-scale application in scenarios such as meteorological observation networks and field environmental monitoring. Attached Figure Description

[0019] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0020] Figure 1 The diagram illustrates the structure of an absolute pressure sensor based on an FP cavity structure according to an embodiment of this application.

[0021] Figure 2A schematic diagram of an absolute pressure sensor based on an FP cavity structure according to another embodiment of this application is shown.

[0022] Figure 3 A schematic diagram of the FP interference cavity according to an embodiment of this application is shown.

[0023] Figure 4 A schematic diagram illustrating a portion of the signal involved in a frequency-modulated continuous wave interference signal according to an embodiment of this application is shown.

[0024] Figure 5 A schematic diagram illustrating the principle of air pressure detection according to an embodiment of this application is shown. Detailed Implementation

[0025] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0026] This application provides an absolute pressure sensor and detection method based on an FP cavity structure, achieving low-cost, high-precision absolute pressure measurement. This meets the needs of micro-pressure fluctuation detection in fields such as atmospheric physics and environmental monitoring, and resolves the accuracy-cost trade-off in fiber optic Fabry-Perot absolute pressure sensor demodulation methods. Specific embodiments are described below.

[0027] Figure 1 The diagram illustrates the structure of an absolute pressure sensor based on an FP cavity structure according to an embodiment of this application.

[0028] like Figure 1 As shown, the absolute pressure sensor based on the FP cavity structure in this embodiment may include a light source module, an optical fiber transmission module, an FP interferometer cavity, a photoelectric detection module, and a signal demodulation module.

[0029] The light source module is used to linearly modulate the received external sawtooth wave modulation signal to output continuous laser light.

[0030] The fiber optic transmission module is used to transmit continuous laser light in one direction, thereby blocking the reflected light from returning to the light source module.

[0031] The FP interferometer cavity includes an output surface of an optical fiber collimator coated with a low-reflectivity film and a total reflection mirror fixed on a pressure-sensitive elastic element. The pressure-sensitive elastic element is used to sense changes in air pressure and generate deformation, which drives the total reflection mirror to move. Continuous laser light is reflected on the output surface and the total reflection mirror to form coherent light, generating a beat frequency light signal carrying air pressure information.

[0032] The photoelectric detection module processes the beat frequency optical signal carrying air pressure information transmitted via the optical fiber transmission module to obtain an electrical signal that meets the demodulation requirements.

[0033] The signal demodulation module is used to process electrical signals that meet demodulation requirements to obtain air pressure values.

[0034] Figure 2 A schematic diagram of an absolute pressure sensor based on an FP cavity structure according to another embodiment of this application is shown.

[0035] like Figure 2 As shown, in some embodiments, the light source module may include a distributed feedback laser (DFB).

[0036] The center wavelength of DFB 1 must match the fiber optic transmission band. It receives sawtooth wave modulated signals and outputs a linearly modulated continuous laser to provide a stable detection light source for the entire sensing system. DFB 1 operates in external modulation mode. DFB 1 is connected to an external digital signal generator via shielded cable to ensure stable transmission of the modulated signal and avoid electromagnetic interference that could cause frequency modulation nonlinearity.

[0037] For example, the optical fiber transmission band can be 1550nm, DFB 1 receives sawtooth wave modulation signals to achieve frequency linear modulation, the sawtooth wave modulation frequency is 1 kHz, and the laser modulation bandwidth is 10 GHz.

[0038] Continue reading Figure 2 In some embodiments, the fiber optic transmission module includes a 1×3-port optical circulator (OC). OC 2 includes three ports.

[0039] The first port connects to the output fiber of the light source module, the second port connects to the input fiber of the FP interferometer cavity, and the third port connects to the input fiber of the photodetector module. Both the output and input fibers can be single-mode fibers. Fiber optic connections between modules use FC / APC connectors. During connection, ensure the fiber end faces are clean to minimize connection loss.

[0040] Figure 3 A schematic diagram of the FP interference cavity according to an embodiment of this application is shown.

[0041] like Figure 2 and Figure 3 As shown, in some embodiments, the pressure-sensitive elastic element includes a vacuum diaphragm 6, and the axial deformation of the vacuum diaphragm 6 is linearly related to the pressure change trend. The vacuum diaphragm 6 can be made of a metal material with stable elastic modulus and low creep (such as 316L stainless steel). The diaphragm is evacuated to below 1 Pa to achieve absolute pressure detection. For example, when external absolute pressure acts on the vacuum diaphragm 6, the vacuum diaphragm 6 undergoes axial elastic deformation under the action of the pressure difference, and its center displacement is linearly related to the pressure. Since the total reflection mirror 7 is fixed on the vacuum diaphragm 6, the deformation of the vacuum diaphragm 6 will drive the total reflection mirror 7 to move synchronously, thereby changing the cavity length of the FP cavity 3. According to the principles of material mechanics, the axial displacement of the vacuum diaphragm 6... With air pressure A linear relationship exists:

[0042]

[0043] in, The linear coefficient is determined by comprehensively considering the elastic modulus, diameter, thickness, and corrugated structure of the membrane material.

[0044] Cavity length of FP interferometer cavity 3 :

[0045]

[0046] in, Let be the initial cavity length of FP interferometer cavity 3.

[0047] The laser beam is reflected at the two reflective surfaces of the FP interferometer cavity 3 to form two coherent beams. The change in cavity length is reflected in the phase difference between the two coherent beams, forming a frequency-modulated continuous wave interference beat frequency light signal.

[0048] Furthermore, the phase difference is:

[0049]

[0050] in, For the refractive index of the gas, Let FP be the cavity length, and c be the speed of light in vacuum. This is the center wavelength of the laser.

[0051] air pressure With phase Relationship

[0052]

[0053] in, , The coefficients, which are related to the structure, material, and size of the FP cavity, can be determined through calibration.

[0054] Furthermore, the number of vacuum diaphragm cells 6 can be one or more, and the sensitivity and resolution of the FP interferometer cavity 3 are related to the number of vacuum diaphragm cells 6. That is, vacuum diaphragm cells 6 can be used individually or in series to adapt to measurement requirements with different sensitivity and resolution.

[0055] Furthermore, the precision of the FP interferometer cavity 3 is positively correlated with the reflectivity of the low-reflectivity film, which has a reflectivity of 0.05 to 0.3.

[0056] For example, the fineness F of the FP interferometer cavity can meet the following requirements. The cavity surface reflectivity R is selected in the low reflectivity range, so that the FP interferometer cavity 3 degenerates into a two-beam interferometer cavity, reducing clutter interference from multi-beam interference and improving the accuracy of phase demodulation.

[0057] Continue reading Figure 3 The FP interference cavity 3 may also include an FP cavity fixture 8 and a collimator mounting hole 9.

[0058] The collimator mounting hole 9 is installed at one end of the FP cavity mounting bracket 8. A fiber optic collimator coated with a low-reflectivity film is installed inside the collimator mounting hole 9. A vacuum diaphragm box 6 is installed at the other end of the FP cavity mounting bracket 8. A total reflection mirror 7 is installed at the center of the vacuum diaphragm box 6, with its surface perpendicular to the output optical axis of the low-reflectivity film-coated fiber optic collimator and parallel to its output surface.

[0059] For example, the total reflection mirror 7 is made of an optical glass substrate coated with a high-reflectivity film (reflectivity ≥99%), and is fixed to the center of the vacuum film box with epoxy resin. When fixing, the surface of the mirror is perpendicular to the output optical axis of the collimator and parallel to the output surface of the collimator, forming an FP cavity with an initial cavity length in the range of 3 cm to 5 cm.

[0060] Continue reading Figure 2 In some embodiments, the photodetector module includes a photodetector 4 (PD) with a built-in signal amplifier. The photodetector converts the beat frequency optical signal carrying air pressure information output from the FP interferometer 3 into an electrical signal. A signal amplification circuit amplifies the electrical signal to obtain an electrical signal that meets demodulation requirements.

[0061] The photodetector 4 can be a photodetector with a response band that matches the center wavelength of the laser and has an amplification function. The amplification circuit uses a low-noise operational amplifier to amplify the weak photocurrent signal to a voltage range (e.g., 0~5 V) that can be recognized by the analog-to-digital converter.

[0062] Continue reading Figure 2 In some embodiments, the signal demodulation module 5 (UC) may include an analog-to-digital converter and an embedded demodulation unit.

[0063] An analog-to-digital converter (ADC) is used to convert electrical signals that meet demodulation requirements into digital beat frequency signals. An embedded demodulation unit is used to generate quadrature cosine signals and quadrature sine signals based on the digital beat frequency signals; mix the digital beat frequency signals with the quadrature cosine signals and quadrature sine signals respectively to obtain a first mixed signal and a second mixed signal; apply low-pass filters with cutoff frequencies lower than the sawtooth wave modulation frequency to the first and second mixed signals respectively to filter out high-frequency noise and retain the baseband components carrying phase information, obtaining a first filtered signal and a second filtered signal; determine the interference phase value of the FP interferometer cavity based on the first and second filtered signals; and determine the air pressure value based on the interference phase value.

[0064] The analog-to-digital converter (ADC) must have a sampling rate of at least 1MHz and a quantization bit depth of at least 14 bits to ensure the sampling accuracy of the digital signal. The embedded demodulation unit can be a microcontroller, FPGA, or industrial control computer, with a built-in digital mixing phase demodulation algorithm program. It transmits data with the ADC to achieve real-time reception and demodulation of the digital beat frequency signal.

[0065] Figure 4 A schematic diagram illustrating a portion of the signal involved in a frequency-modulated continuous wave interference signal according to an embodiment of this application is shown.

[0066] Figure 5 A schematic diagram illustrating the principle of air pressure detection according to an embodiment of this application is shown.

[0067] like Figure 4 and Figure 5 As shown, the sawtooth wave modulated signal passes through the distributed feedback laser 1, and under the modulation voltage 10 of the DFB laser, it undergoes linear frequency modulation to output continuous laser light. The linearly modulated laser light output from the laser is transmitted through an optical fiber to the FP interferometer cavity 3, where it is reflected at the collimator exit surface and the surface of the total reflection mirror, forming two coherent beams. The optical path difference between the two beams is twice the cavity length of the FP interferometer cavity 3. (where n is the refractive index of the gas inside the cavity), changes in the optical path difference will cause synchronous changes in the phase difference of the interference light, and the relationship between the phase difference and the cavity length satisfies This modulates the change in cavity length (i.e., the change in air pressure) into a phase change in the interference light.

[0068] Any modulation period Internal beat frequency signal strength

[0069]

[0070] in, and These are the initial light intensities of the two beams, This refers to the beat frequency signal frequency.

[0071] Embedded demodulation unit for digital beat frequency signal The execution of the digital mixing phase demodulation algorithm specifically includes:

[0072] Orthogonal signal generation: The digital beat frequency signal 11 in a pre-acquired static state is used to obtain the frequency corresponding to its spectral maximum through Fast Fourier Transform (FFT), and this frequency is used as the beat frequency signal frequency. approximation The generation frequency is Orthogonal signal group 12:

[0073]

[0074] Digital mixing: The digital beat frequency signal 11 is multiplied and mixed with the orthogonal cosine signal and the orthogonal sine signal respectively to realize the spectrum shift of the beat frequency signal, and the characteristic frequency component is down-converted to the baseband zero frequency to obtain the first mixing signal and the second mixing signal.

[0075] Low-pass filtering: Low-pass filters with a cutoff frequency less than 1kHz of the sawtooth wave modulation frequency are applied to the two mixed signals after mixing to filter out high-frequency noise and retain the baseband component carrying phase information. The first and second filtered signals are as follows:

[0076]

[0077] Phase extraction: Divide the two filtered baseband components by 15 arctangents and 16 to extract the interference phase value corresponding to the cavity length of the FP interferometer cavity 3;

[0078]

[0079] Combined with the pre-calibrated pressure-phase linear relationship The demodulation result 17 is obtained, which is the absolute air pressure value.

[0080] Based on the above-mentioned absolute pressure sensor, embodiments of this application also provide a method for detecting air pressure.

[0081] The barometric pressure detection method may include: activating the light source module to linearly modulate the received external sawtooth wave modulation signal to output continuous laser light; transmitting the continuous laser light unidirectionally to the FP interferometer cavity through the fiber optic transmission module, causing the continuous laser light to be reflected on the exit surface and the total reflection mirror to form coherent light, generating a beat frequency optical signal carrying barometric pressure information; processing the beat frequency optical signal carrying barometric pressure information transmitted through the fiber optic transmission module using the photoelectric detection module to obtain an electrical signal that meets the demodulation requirements; and processing the electrical signal that meets the demodulation requirements using the signal demodulation module to obtain the barometric pressure value.

[0082] For example, firstly, sensor assembly and debugging: Assemble each module according to the assembly requirements described above, and connect the optical fibers and circuits between the modules. Start the light source module, adjust the signal generator to generate a sawtooth wave modulation signal, and observe the modulation voltage waveform of the laser using an oscilloscope to ensure that the waveform is distortion-free. Adjust the FP cavity mounting bracket to align the collimator and the reflector, and observe the interference signal intensity using a photodetector. When the signal intensity reaches its maximum value, fix the FP cavity structure to complete the optical path debugging.

[0083] Secondly, interference signal acquisition: The laser is reflected by the two reflective surfaces of the FP cavity to form coherent light, generating a beat frequency optical signal carrying air pressure information. The beat frequency optical signal is transmitted to the photodetector via an optical fiber circulator, converted into an analog electrical signal, amplified by a signal amplification circuit, and then converted into a digital beat frequency signal by an analog-to-digital converter at a set sampling rate, which is then transmitted to the embedded demodulation unit in real time.

[0084] Next, please continue reading. Figure 4 Signal demodulation and phase output:

[0085] Orthogonal signal generation: The demodulation unit performs FFT analysis on the acquired digital beat frequency signal to determine the characteristic frequencies corresponding to the spectral maxima. This generates orthogonal cosine and sine signals at that frequency;

[0086] Digital mixing: The digital beat frequency signal is multiplied with two orthogonal signals respectively to achieve spectrum shifting, so that the characteristic frequency components are down-converted to the baseband;

[0087] Low-pass filtering: The two mixed signals are subjected to low-pass filtering to remove high-frequency noise and retain the baseband components.

[0088] Phase extraction: Perform arctangent operation on the filtered baseband components to extract the interference phase value. .

[0089] Next, sensor calibration: Place the sensor on a controllable positive and negative pressure test platform and connect a high-precision reference absolute pressure gauge (accuracy not less than 0.05% FS). Within the sensor's measurement range (recommended 0~120 kPa), select no fewer than 10 standard pressure points at even intervals, and sequentially stabilize the air pressure within the test platform at each standard pressure point. Record the interference phase value output by the embedded demodulation unit at each pressure point. A linear fitting method was used to establish a linear correlation model between phase and air pressure. The model parameters are then entered into the demodulation unit to complete the calibration.

[0090] Finally, the pressure output is as follows: the extracted phase value is substituted into the calibrated pressure-phase linear relationship. The absolute air pressure value is calculated and transmitted to the display device or data storage module through the output interface of the demodulation unit.

[0091] It should be noted that for details not covered in the barometric pressure detection embodiment section, please refer to the absolute pressure sensor embodiment section; specific details will not be repeated here.

[0092] The embodiments of this application have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of this application. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this application is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this application, and all such substitutions and modifications should fall within the scope of this application.

Claims

1. An absolute pressure sensor based on F-P cavity structure, characterized in that, The application relates to a gas pressure sensor, which comprises the following parts: a light source module for frequency linear modulation of an external sawtooth wave modulation signal to output continuous laser; a fiber transmission module for one-way transmission of the continuous laser to block the reflection of the continuous laser from returning to the light source module; an F-P interference cavity comprising a fiber collimator exit surface coated with a low reflectivity film and a total reflection mirror fixed on a gas pressure sensitive elastic element, the gas pressure sensitive elastic element is used for sensing the change of the gas pressure and generating deformation to drive the displacement of the total reflection mirror, the continuous laser is reflected on the exit surface and the total reflection mirror to form coherent light, and beat frequency light signals carrying the gas pressure information are generated; a photoelectric detection module for processing the beat frequency light signals carrying the gas pressure information transmitted through the fiber transmission module to obtain electrical signals meeting the demodulation requirement; and a signal demodulation module for processing the electrical signals meeting the demodulation requirement to obtain the gas pressure value. The gas pressure sensitive elastic element comprises a vacuum film box, and the axial deformation of the vacuum film box is linearly related to the change trend of the gas pressure. The number of the vacuum film boxes is one or more, and the sensitivity and resolution of the F-P interference cavity are related to the number of the vacuum film boxes. The precision of the F-P interference cavity is positively related to the reflectivity of the low reflectivity film, and the reflectivity of the low reflectivity film is 0.05-0.

3. The F-P interference cavity further comprises an F-P cavity fixing frame, a collimator placing hole installed at one end of the F-P cavity fixing frame, a fiber collimator coated with a low reflectivity film installed in the collimator placing hole, a gas pressure sensitive elastic element installed at the other end of the F-P cavity fixing frame, and a total reflection mirror installed at the central position of the gas pressure sensitive elastic element, the surface of the total reflection mirror is perpendicular to the exit optical axis of the fiber collimator coated with a low reflectivity film and parallel to the exit surface of the fiber collimator coated with a low reflectivity film. The light source module comprises a distributed feedback laser, the central wavelength of the distributed feedback laser needs to match the fiber transmission wave band, and the working mode is set as an external modulation mode; and the distributed feedback laser is connected with an external digital signal generator through a shielding cable.

2. The absolute pressure sensor of claim 1, wherein, The fiber transmission module comprises a 1*3 port fiber ring resonator, a first port of the fiber ring resonator is connected with an output fiber of the light source module, a second port of the fiber ring resonator is connected with an input fiber of the F-P interference cavity, and a third port of the fiber ring resonator is connected with an input fiber of the photoelectric detection module.

3. The absolute pressure sensor of claim 2, wherein, The photoelectric detection module comprises a photoelectric detector for converting the beat frequency light signals carrying the gas pressure information into electrical signals; and a signal amplification circuit for amplifying the electrical signals to obtain electrical signals meeting the demodulation requirement.

4. The absolute pressure sensor of claim 1, wherein, The signal demodulation module comprises an analog-digital converter for converting the electrical signals meeting the demodulation requirement into digital beat frequency signals.

5. The absolute pressure sensor according to any one of claims 1 to 4, characterized in that ​ ​ ​ ​ ​ ​ 6. The absolute pressure sensor of claim 1, wherein, ​ ​ ​ 7. The absolute pressure sensor of claim 1, wherein, ​ ​ 8. The absolute pressure sensor of claim 1, wherein, ​ ​ ​ 9. The absolute pressure sensor of claim 1, wherein, ​ ​ An embedded demodulation unit is configured to generate an orthogonal cosine signal and an orthogonal sine signal based on the digital beat frequency signal; mix the digital beat frequency signal with the orthogonal cosine signal and the orthogonal sine signal respectively to obtain a first mixed signal and a second mixed signal; apply low-pass filtering with a cutoff frequency lower than the sawtooth wave modulation frequency to the first mixed signal and the second mixed signal respectively to filter out high-frequency noise and retain the baseband component carrying phase information to obtain a first filtered signal and a second filtered signal; determine the interference phase value of the FP interferometer based on the first filtered signal and the second filtered signal; and determine the air pressure value based on the interference phase value.

10. An air pressure detecting method characterized by comprising: The pressure detection method is implemented based on the absolute pressure sensor according to any one of claims 1 to 9, and the pressure detection method includes: The light source module is activated to perform frequency linear modulation on the received external sawtooth wave modulation signal and output continuous laser. The continuous laser is transmitted unidirectionally to the FP interferometer cavity through the fiber optic transmission module, so that the continuous laser is reflected on the exit surface and the total reflection mirror to form coherent light, generating a beat frequency optical signal carrying air pressure information. The photoelectric detection module processes the beat frequency optical signal carrying air pressure information transmitted through the optical fiber transmission module to obtain an electrical signal that meets the demodulation requirements. The electrical signal that meets the demodulation requirements is processed using a signal demodulation module to obtain the air pressure value.

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