A pressure and temperature distribution simultaneous measurement device and method based on microwave domain and light domain demodulation

Abstract

The application discloses a pressure and temperature distributed simultaneous measurement device and method based on microwave domain and light domain demodulation. The measurement device comprises a polarization maintaining output broadband light source, an electro-optic modulator, a vector network analyzer, a first radio frequency amplifier, a first erbium-doped fiber amplifier, an optical circulator, a 1*2 optical fiber coupler, a transmission optical fiber, a distributed sensing grating array, a photoelectric detector, a second radio frequency amplifier, a second erbium-doped fiber amplifier, an optical fiber grating demodulator and a computer. The application can realize distributed simultaneous measurement of pressure and temperature based on a single sensing optical fiber.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photoelectric testing, and particularly relates to a pressure and temperature distributed simultaneous measurement device and method based on microwave domain and light domain demodulation. BACKGROUND

[0002] Optical fiber sensing technology is a new type of sensing technology which uses optical fiber as a medium to perceive external information and can simultaneously transmit signals. The optical fiber sensor can measure many parameters such as pressure, stress, temperature, refractive index, voltage, current, acceleration, flow rate, displacement, etc. Due to its unique advantages such as good insulation, anti-electromagnetic interference, light weight, small size, etc. in the fields of chemistry, mechanics and electricity, it can work in harsh conditions such as high temperature, high pressure, high magnetic field, nuclear radiation and corrosion. For many years, it has been widely concerned and researched, and has been widely used in power systems, petrochemical industry, aerospace, civil engineering, biomedicine and other fields. So far, various optical fiber sensing technologies have been developed based on different measurement principles, and have developed from single-point measurement to multi-point quasi-distributed and full-distributed measurement. Among them, the sensing technology based on fiber Bragg grating (FBG) has become one of the most representative and promising optical fiber sensing technologies due to its integration, miniaturization, reusability and mature manufacturing process.

[0003] Pressure and temperature are important measurement parameters, and their full-distributed simultaneous measurement has important significance in existing practical application environments such as industrial production, oil and gas transportation, environmental monitoring and clinical trials. However, it is difficult to distinguish the drift of the FBG center wavelength caused by the external pressure and temperature changes of the FBG sensor, that is, there is a cross-sensitivity problem. The grating deformation caused by pressure and the thermal expansion effect caused by temperature will affect the grating pitch; and the photoelastic effect caused by pressure and the thermo-optic effect caused by temperature will cause the effective refractive index of the optical fiber core to change. In order to solve this problem and realize the simultaneous measurement of temperature and pressure, many solutions to the cross-sensitivity problem have been proposed by domestic and foreign researchers, including pressure-desensitized temperature sensing, temperature-compensated pressure sensing, double-wavelength matrix method, etc. However, these technologies are difficult to realize the simultaneous measurement of temperature and pressure based on the same FBG sensing unit on a single sensing optical fiber, and most of them are point or quasi-distributed measurement, which cannot realize the distributed simultaneous measurement of pressure and temperature. SUMMARY

[0004] The application aims to overcome the defects in the prior art, solve the problem that the existing fiber grating sensing technology is difficult to realize the distributed simultaneous measurement of pressure and temperature on a single sensing fiber, and provide a pressure and temperature distributed simultaneous measurement device and method based on microwave domain and optical domain demodulation, which can realize the distributed simultaneous measurement of pressure and temperature based on a single fiber.

[0005] The application aims to realize the above-mentioned purpose through the following technical solutions.

[0006] The application aims to realize the above-mentioned purpose through the following technical solutions.

[0007] The output end of the polarization maintaining output broadband light source is connected with the input end of the electro-optical modulator; the signal output end of the vector network analyzer is connected with the signal input end of the first radio frequency amplifier through a high-frequency cable; the signal output end of the first radio frequency amplifier is connected with the modulation signal input end of the electro-optical modulator through a high-frequency cable; the output end of the electro-optical modulator is connected with the input end of the first erbium-doped fiber amplifier; the output end of the first erbium-doped fiber amplifier is connected with the incident end of the optical circulator; the reflection end of the optical circulator is connected with the a port of the 1*2 optical fiber coupler; the c port of the 1*2 optical fiber coupler is connected with the transmission fiber; the transmission fiber is connected with the distributed sensing grating array; the output end of the optical circulator is connected with the incident end of the photodetector; the emission end of the photodetector is connected with the signal input end of the second radio frequency amplifier through a high-frequency cable; the signal output end of the second radio frequency amplifier is connected with the signal input end of the vector network analyzer through a high-frequency cable; the vector network analyzer is connected with the computer; the b port of the 1*2 optical fiber coupler is connected with the input end of the second erbium-doped fiber amplifier; the output end of the second erbium-doped fiber amplifier is connected with the input end of the fiber grating demodulator; the fiber grating demodulator is connected with the computer.

[0008] Further, the fiber core of the distributed sensing grating array is processed with continuous reflectors by femtosecond laser, and the fiber Bragg gratings FBG with different center wavelengths are respectively processed in the adjacent reflectors; wherein the optical path difference corresponding to the interval of the adjacent reflectors is greater than the coherence length of the polarization maintaining output broadband light source and less than the coherence length of the microwave sweep signal generated by the vector network analyzer; the reflectivity of the fiber Bragg grating FBG is less than the reflectivity of the reflector.

[0009] The application further provides a pressure and temperature distributed simultaneous measurement method based on microwave domain and optical domain demodulation, which comprises the following steps.

[0010] The light signal output by the polarization maintaining output broadband light source enters the electro-optic modulator; the microwave signal output by the vector network analyzer enters the electro-optic modulator after being amplified by the first radio frequency amplifier; the light signal modulated by the microwave signal is output from the electro-optic modulator and enters the first erbium-doped fiber amplifier, and is input to the optical circulator after being amplified by the first erbium-doped fiber amplifier; the light signal is output from the reflection end of the optical circulator and is input from the a port of the 1x2 optical fiber coupler after being output from the c port of the 1x2 optical fiber coupler, and enters the transmission optical fiber; the light signal enters the distributed sensing grating array after passing through the transmission optical fiber, the microwave signal loaded on the light signal is reflected by each reflector and meets at the interference point in the distributed sensing grating array to form a microwave interference signal; the microwave interference signal is output from the a port of the 1x2 optical fiber coupler and enters the reflection end of the optical circulator, and is output from the exit end of the optical circulator and enters the photodetector; the microwave interference signal is converted into an electrical signal by the photodetector and enters the second radio frequency amplifier for amplification; the amplified electrical signal is collected by the vector network analyzer; by sweeping the vector network analyzer, the microwave interference spectrum of the microwave reflection signal reflected by the reflector of the distributed sensing grating array is obtained; the spatial distribution information of the microwave reflection signal corresponding to the microwave interference spectrum is obtained by inverse Fourier transform, and then the adjacent two reflection signals are selected by using a window function and the microwave interference spectrum is reconstructed by Fourier transform; the light signal reflected by each fiber Bragg grating FBG of the distributed sensing grating array is output from the b port of the 1x2 optical fiber coupler and enters the second erbium-doped fiber amplifier, and is collected by the fiber grating demodulator (13) after being amplified by the second erbium-doped fiber amplifier; the reflection spectrum of each fiber Bragg grating FBG in the distributed sensing grating array is obtained by the fiber grating demodulator. The computer is used for controlling and collecting data of the vector network analyzer and the fiber grating demodulator, and processing and analyzing the collected data.

[0011] Further, the reconstructed microwave interference spectrum will be frequency shifted due to the influence of external pressure and temperature change on the distributed sensing grating array; there is a corresponding relationship between the change amount of pressure and temperature and the change amount of optical path difference corresponding to the spacing of adjacent reflectors, and there is a corresponding relationship between the change amount of optical path difference corresponding to the spacing of adjacent reflectors and the frequency shift amount of the microwave interference spectrum, so as to obtain the relationship between the change amount of pressure and temperature and the frequency shift amount of the microwave interference spectrum;

[0012] At the same time, the change of grating pitch and refractive index caused by the change of pressure and temperature will cause the center wavelength of the fiber Bragg grating FBG reflection spectrum to shift, and there is a corresponding relationship between the change amount of pressure and temperature and the shift amount of the center wavelength of the fiber Bragg grating FBG reflection spectrum, so as to obtain the relationship between the change amount of pressure and temperature and the shift amount of the center wavelength of the fiber Bragg grating FBG reflection spectrum; the simultaneous measurement of pressure and temperature distribution is realized by solving the above two relationship formulas.

[0013] Further, two relationship expressions are respectively:

[0014] Delta f=k P1 Delta P+k T1 Delta T

[0015] Delta lambda=k P2 Delta P+k T2 Delta T

[0016] Wherein, Delta f represents microwave interference spectrum frequency shift amount;k P1 And k T1 Respectively represent the pressure sensitivity and temperature sensitivity coefficient based on microwave interference demodulation;Delta lambda represents the fiber Bragg grating FBG reflection spectrum center wavelength offset amount;k P2 And k T2 Respectively represent the pressure sensitivity and temperature sensitivity coefficient based on fiber Bragg grating FBG reflection spectrum demodulation;Delta P and Delta T represent the change amount of temperature and pressure respectively;

[0017] The simultaneous equations are written in matrix form as follows:

[0018]

[0019] Through pre-calibration, the sensitivity coefficients are obtained, and then the change amounts of pressure and temperature are solved by the above formula according to the measured microwave interference spectrum frequency shift amount and the offset amount of the fiber Bragg grating FBG reflection spectrum center wavelength, so as to realize the distributed simultaneous measurement of pressure and temperature.

[0020] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0021] 1. Distributed simultaneous measurement of pressure and temperature is realized: by using a distributed sensing grating array on a single sensing fiber, based on microwave photon technology, the light signal and microwave signal are demodulated from the light domain and microwave domain respectively, the distribution of pressure and temperature can be measured simultaneously, the problem of difficulty in distinguishing the fiber Bragg grating (FBG) center wavelength drift caused by temperature and pressure in the prior art is overcome, and the cross-sensitivity problem is solved.

[0022] 2. High precision and high sensitivity: advanced equipment such as polarization maintaining output broadband light source, vector network analyzer, fiber grating demodulator, etc. is used to ensure the high precision and high sensitivity of the measurement system. The microwave interference spectrum of all adjacent two reflectors is reconstructed, and the FBG of different wavelengths processed in the middle of the two reflectors is combined to realize the distributed measurement of pressure and temperature. And the length of the reflector and the grating can be flexibly set to meet the different sensing spatial resolution requirements, which has high flexibility. The fiber grating demodulator can accurately demodulate the pressure and temperature signals, and improve the reliability and accuracy of the measurement.

[0023] 3. Wide application range: Due to the good insulation, anti-electromagnetic interference ability, lightness, small size and other advantages of the optical fiber sensor, the application can work in harsh environments such as high temperature, high pressure, high magnetic field, nuclear radiation and corrosion, and is suitable for multiple fields such as power system, petrochemical industry, aerospace, civil engineering and biomedicine.

[0024] 4. Integration and miniaturization: Based on the fiber Bragg grating (FBG) technology, the application has the advantages of integration and miniaturization. The whole measuring device has a compact structure, is easy to install and maintain, and is suitable for use in space-limited environments.

[0025] 5. High reliability and durability: The optical fiber sensor and related equipment have good mechanical strength and durability, can maintain stable performance in long-term use, and reduce maintenance cost and frequency.

[0026] 6. Significant economic benefits: The application uses single-path sensing optical fiber for distributed measurement, which reduces wiring and equipment costs compared to multi-point measurement systems, improves economic benefits, and has a simple measurement method, which can be quickly deployed and applied. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a structural schematic diagram of the measuring device of the application.

[0028] Figure 2 is an example diagram of the distributed sensing grating array in the measuring device of the application.

[0029] Reference signs: 1-polarization maintaining output broadband light source, 2-electro-optic modulator, 3-vector network analyzer, 4-first radio frequency amplifier, 5-first erbium-doped fiber amplifier, 6-optical circulator, 7-1×2 optical fiber coupler, 8-transmission optical fiber, 9-distributed sensing grating array, 10-optoelectronic detector, 11-second radio frequency amplifier, 12-second erbium-doped fiber amplifier, 13-optical fiber grating demodulator, 14-computer. DETAILED DESCRIPTION

[0030] The application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0031] The embodiment provides a pressure and temperature distributed simultaneous measurement device based on microwave domain and light domain demodulation, which comprises a polarization maintaining output broadband light source 1, an electro-optic modulator 2, a vector network analyzer 3, a first radio frequency amplifier 4, a first erbium-doped fiber amplifier 5, an optical circulator 6, a 1x2 optical fiber coupler 7, a transmission optical fiber 8, a distributed sensing grating array 9, a photodetector 10, a second radio frequency amplifier 11, a second erbium-doped fiber amplifier 12, an optical fiber grating demodulator 13 and a computer 14.

[0032] The output end of the polarization maintaining output broadband light source 1 is connected with the input end of the electro-optic modulator 2; the signal output end of the vector network analyzer 3 is connected with the signal input end of the first radio frequency amplifier 4 through a high-frequency cable; the signal output end of the first radio frequency amplifier 4 is connected with the modulation signal input end of the electro-optic modulator 2 through a high-frequency cable; the output end of the electro-optic modulator 2 is connected with the input end of the first erbium-doped fiber amplifier 5; the output end of the first erbium-doped fiber amplifier 5 is connected with the incident end of the optical circulator 6; the reflection end of the optical circulator 6 is connected with the a port of the 1x2 optical fiber coupler 7; the c port of the 1x2 optical fiber coupler 7 is connected with the transmission optical fiber 8; the transmission optical fiber 8 is connected with the distributed sensing grating array 9; the output end of the optical circulator 6 is connected with the incident end of the photodetector 10; the emission end of the photodetector 10 is connected with the signal input end of the second radio frequency amplifier 11 through a high-frequency cable; the signal output end of the second radio frequency amplifier 11 is connected with the signal input end of the vector network analyzer 3 through a high-frequency cable, and the vector network analyzer 3 is connected with the computer 14. The b port of the 1x2 optical fiber coupler 7 is connected with the input end of the second erbium-doped fiber amplifier 12; the output end of the second erbium-doped fiber amplifier 12 is connected with the input end of the optical fiber grating demodulator 13; and the optical fiber grating demodulator 13 is connected with the computer 14.

[0033] In specific implementation, continuous reflectors are processed in the fiber core of the distributed sensing grating array 9 by femtosecond laser, and FBGs with different center wavelengths and equal length to the interval of adjacent reflectors are processed in the interval between adjacent reflectors; wherein the optical path difference corresponding to the interval of adjacent reflectors is greater than the coherence length of the polarization maintaining output broadband light source 1 and less than the coherence length of the microwave sweep signal generated by the vector network analyzer 3; and the reflectivity of the FBG is less than the reflectivity of the reflector.

[0034] Preferably, the embodiment further provides a pressure and temperature distributed simultaneous measurement method based on microwave domain and light domain demodulation, which is implemented in the pressure and temperature distributed simultaneous measurement device based on microwave domain and light domain demodulation and is implemented by the following steps.

[0035] The light signal output by the polarization maintaining output broadband light source 1 enters the electro-optic modulator 2; the microwave signal output by the vector network analyzer 3 enters the electro-optic modulator 2 after being amplified by the first radio frequency amplifier 4; the light signal modulated by the microwave signal is output from the electro-optic modulator 2 and enters the first erbium-doped fiber amplifier 5, and is input to the optical circulator 6 after being amplified by the first erbium-doped fiber amplifier 5; the light signal is output from the a port of the 1x2 optical fiber coupler 7 after being output from the reflection end of the optical circulator 6, and enters the transmission optical fiber 8 after being output from the c port of the 1x2 optical fiber coupler 7; the light signal enters the distributed sensing grating array 9 after passing through the transmission optical fiber 8, the microwave signal loaded on the light signal is reflected by each reflector and interferes at the meeting place to form a microwave interference signal; the microwave interference signal is output from the a port of the 1x2 optical fiber coupler 7 and enters the reflection end of the optical circulator 6, and is output from the exit end of the optical circulator 6 and enters the photodetector 10; the microwave interference signal is converted into an electrical signal by the photodetector 10 and enters the second radio frequency amplifier 11 for amplification; the amplified electrical signal is collected by the vector network analyzer 3; by sweeping the vector network analyzer 3, the microwave interference spectrum of the microwave reflection signal reflected by the reflector of the distributed sensing grating array 9 can be obtained; the spatial distribution information of the microwave reflection signal corresponding to the microwave interference spectrum is obtained by inverse Fourier transform, and then the adjacent two reflection signals are selected by using a window function and the microwave interference spectrum is reconstructed by Fourier transform; the light signal reflected by each fiber Bragg grating FBG of the distributed sensing grating array 9 is output from the b port of the 1x2 optical fiber coupler 7 and enters the second erbium-doped fiber amplifier 12, and is collected by the fiber grating demodulator 13 after being amplified by the second erbium-doped fiber amplifier 12; the reflection spectrum of each fiber Bragg grating FBG in the distributed sensing grating array 9 is obtained by the fiber grating demodulator 13. The computer 14 is used for controlling and collecting data of the vector network analyzer 3 and the fiber grating demodulator 13, and processing and analyzing the collected data.

[0036] The distributed sensing grating array 9 is affected by external pressure and temperature changes, and the length and refractive index of the grating at the corresponding position will change, thereby changing the optical path difference of the light signal modulated by the microwave signal reflected by adjacent reflectors, and further causing the reconstructed microwave interference spectrum to be frequency shifted; the changes in pressure and temperature correspond to the change in optical path difference, and the change in optical path difference corresponds to the frequency shift of the microwave interference spectrum, and thus the relationship between the changes in pressure and temperature and the frequency shift of the microwave interference spectrum can be obtained. At the same time, the changes in grating pitch and refractive index caused by changes in pressure and temperature will also cause the center wavelength of the fiber Bragg grating FBG reflection spectrum to shift, and the changes in pressure and temperature correspond to the shift of the center wavelength of the fiber Bragg grating FBG reflection spectrum, and thus the relationship between the changes in pressure and temperature and the shift of the center wavelength of the fiber Bragg grating FBG reflection spectrum can be obtained. By solving these two relationships, the pressure and temperature distribution can be simultaneously measured.

[0037] In particular implementation, the two relational expressions are:

[0038] Δf=k P1 ΔP+k T1 ΔT

[0039] Δλ=k P2 ΔP+k T2 ΔT

[0040] Wherein, Δf represents the microwave interference spectrum frequency shift amount; k P1 and k T1 respectively represent the pressure sensitivity and temperature sensitivity coefficients based on microwave interference demodulation; Δλ represents the fiber Bragg grating (FBG) reflected spectrum center wavelength shift amount; k P2 and k T2 respectively represent the pressure sensitivity and temperature sensitivity coefficients based on fiber Bragg grating (FBG) reflected spectrum demodulation; ΔP and ΔP respectively represent the temperature and pressure change amount.

[0041] The two relational expressions are written in matrix form as follows:

[0042]

[0043] Through pre-calibration, the sensitivity coefficients are obtained, and then according to the measured microwave interference spectrum frequency shift amount and the fiber Bragg grating (FBG) reflected spectrum center wavelength shift amount, the pressure and temperature change amount can be solved through the above formula, so as to realize the distributed simultaneous measurement of pressure and temperature.

[0044] The above-described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The above embodiments and drawings are only used to illustrate the technical solutions of the present application and are not limited to the present application. The preferred embodiments of the present application are described in detail, and those skilled in the art should understand that the changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present application do not deviate from the purpose of the present application, and should also belong to the protection scope of the claims of the present application.

Claims

1. A pressure and temperature distribution simultaneous measurement device based on microwave domain and optical domain demodulation, characterized in that, The application relates to a polarization maintaining output broadband light source (1), an electro-optical modulator (2), a vector network analyzer (3), a first radio frequency amplifier (4), a first erbium-doped fiber amplifier (5), an optical circulator (6), a 1*2 optical fiber coupler (7), a transmission optical fiber (8), a distributed sensing grating array (9), a photoelectric detector (10), a second radio frequency amplifier (11), a second erbium-doped fiber amplifier (12), a fiber grating demodulator (13) and a computer (14). The output end of the polarization maintaining output broadband light source (1) is connected with the input end of the electro-optical modulator (2); the signal output end of the vector network analyzer (3) is connected with the signal input end of the first radio frequency amplifier (4) through a high-frequency cable; the signal output end of the first radio frequency amplifier (4) is connected with the modulation signal input end of the electro-optical modulator (2) through a high-frequency cable; the output end of the electro-optical modulator (2) is connected with the input end of the first erbium-doped fiber amplifier (5); the output end of the first erbium-doped fiber amplifier (5) is connected with the incident end of the optical circulator (6); the reflection end of the optical circulator (6) is connected with the a port of the 1*2 optical fiber coupler (7); the c port of the 1*2 optical fiber coupler (7) is connected with the transmission optical fiber (8); the transmission optical fiber (8) is connected with the distributed sensing grating array (9); the output end of the optical circulator (6) is connected with the incident end of the photoelectric detector (10); the ejection end of the photoelectric detector (10) is connected with the signal input end of the second radio frequency amplifier (11) through a high-frequency cable; the signal output end of the second radio frequency amplifier (11) is connected with the signal input end of the vector network analyzer (3) through a high-frequency cable; the vector network analyzer (3) is connected with the computer (14); the b port of the 1*2 optical fiber coupler (7) is connected with the input end of the second erbium-doped fiber amplifier (12); the output end of the second erbium-doped fiber amplifier (12) is connected with the input end of the fiber grating demodulator (13); the fiber grating demodulator (13) is connected with the computer (14); the fiber core of the distributed sensing grating array (9) is processed with continuous reflectors by femtosecond laser, and different center wavelength fiber Bragg gratings FBGs are processed in the middle of adjacent reflectors.

2. The pressure and temperature distribution simultaneous measurement device based on microwave and optical demodulation according to claim 1, characterized in that, The interval of the adjacent reflectors corresponds to an optical path difference which is greater than the coherence length of the polarization maintaining output broadband light source (1) and is less than the coherence length of the microwave sweep signal generated by the vector network analyzer (3); the reflectivity of the fiber Bragg grating FBG is less than the reflectivity of the reflector.

3. A method for pressure and temperature distributed simultaneous measurement based on microwave and optical demodulation, based on the pressure and temperature distributed simultaneous measurement device of any one of claims 1-2, characterized in that, The application relates to a polarization maintaining output broadband light source (1), an electro-optical modulator (2), a vector network analyzer (3), a first radio frequency amplifier (4), a first erbium-doped fiber amplifier (5), an optical circulator (6), a 1*2 optical fiber coupler (7), a transmission optical fiber (8), a distributed sensing grating array (9), a photoelectric detector (10), a second radio frequency amplifier (11), a second erbium-doped fiber amplifier (12), a fiber grating demodulator (13) and a computer (14). The light signal output by the polarization maintaining output broadband light source (1) enters the electro-optical modulator (2); the microwave signal output by the vector network analyzer (3) enters the electro-optical modulator (2) after being amplified by the first radio frequency amplifier (4); the light signal modulated by the microwave signal is output from the electro-optical modulator (2) and enters the first erbium-doped fiber amplifier (5), and is input to the optical circulator (6) after being amplified by the first erbium-doped fiber amplifier (5); the light signal is output from the a port of the 1×2 optical fiber coupler (7) after being reflected by the reflection end of the optical circulator (6), and enters the transmission optical fiber (8) after being output from the c port of the 1×2 optical fiber coupler (7); the microwave signal loaded on the light signal is reflected by each reflector and meets at the interference point in the distributed sensing grating array (9) to form a microwave interference signal; the microwave interference signal is output from the a port of the 1×2 optical fiber coupler (7) and enters the reflection end of the optical circulator (6), and is output from the exit end of the optical circulator (6) and enters the photodetector (10); the microwave interference signal is converted into an electrical signal by the photodetector (10) and enters the second radio frequency amplifier (11) for amplification; the amplified electrical signal is collected by the vector network analyzer (3); by sweeping the vector network analyzer (3), the microwave interference spectrum of the microwave reflection signal reflected by the reflector of the distributed sensing grating array (9) is obtained; the spatial distribution information of the microwave reflection signal corresponding to the microwave interference spectrum is obtained by inverse Fourier transform, and then the adjacent two reflection signals are selected by using a window function and the microwave interference spectrum is reconstructed by Fourier transform; The light signal reflected by each fiber Bragg grating FBG of the distributed sensing grating array (9) is output from the b port of the 1×2 optical fiber coupler (7) and enters the second erbium-doped fiber amplifier (12), and is collected by the fiber grating demodulator (13) after being amplified by the second erbium-doped fiber amplifier (12); the reflection spectrum of each fiber Bragg grating FBG in the distributed sensing grating array (9) is obtained by the fiber grating demodulator (13); the computer (14) is used for controlling and collecting data of the vector network analyzer (3) and the fiber grating demodulator (13), and processing and analyzing the collected data.

4. The method according to claim 3, wherein, The reconstructed microwave interference spectrum will be frequency-shifted due to the influence of external pressure and temperature change on the distributed sensing grating array (9); there is a corresponding relationship between the change of pressure and temperature and the change of optical path difference corresponding to the distance between adjacent reflectors, and there is a corresponding relationship between the change of optical path difference corresponding to the distance between adjacent reflectors and the frequency shift amount of the microwave interference spectrum, so as to obtain the relationship between the change of pressure and temperature and the frequency shift amount of the microwave interference spectrum. Meanwhile, the changes of the grating pitch and the refractive index caused by the changes of the pressure and the temperature will cause the center wavelength of the fiber Bragg grating (FBG) reflection spectrum to shift, and the change amount of the pressure and the temperature has a corresponding relationship with the shift amount of the center wavelength of the fiber Bragg grating (FBG) reflection spectrum, so that a relationship between the change amount of the pressure and the temperature and the shift amount of the center wavelength of the fiber Bragg grating (FBG) reflection spectrum is obtained; the simultaneous measurement of the pressure and the temperature distribution is realized by solving the above two relationship equations.

5. The method of claim 4, wherein the method is a microwave and optical domain based simultaneous measurement of pressure and temperature distribution. The two relationship equations are respectively: ； wherein, Δf represents the microwave interference spectrum frequency shift amount; k P1 and k T1 respectively represent the pressure sensitivity and temperature sensitivity coefficients based on microwave interference demodulation; Δλ represents the fiber Bragg grating FBG reflected spectrum center wavelength shift amount; k P2 and k T2 respectively represent the pressure sensitivity and temperature sensitivity coefficients based on fiber Bragg grating FBG reflected spectrum demodulation; ΔP and ΔT respectively represent the temperature and pressure change amounts; The two relationship equations are written in a matrix form as: ； The sensitivity coefficients are obtained through pre-calibration, and then the change amount of the pressure and the temperature is solved by the above equation according to the measured microwave interference spectrum frequency shift amount and the shift amount of the center wavelength of the fiber Bragg grating (FBG) reflection spectrum, so that the simultaneous measurement of the pressure and the temperature distribution is realized.

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