Two-parameter sensing system based on optical fiber Fabry-Perot and inspection method and demodulation method thereof

Abstract

The invention provides a two-parameter sensing system based on optical fiber Fabry-Perot, and an inspection method and a demodulation method thereof. The two-parameter sensing system comprises a sensitive diaphragm, an optical element and at least one base component, a concave groove is formed in one side of the base part; the sensitive diaphragm is connected with the base component to form at least one optical fiber Fabry-Perot cavity which contains the groove and is used for measuring pressure, and an optical fiber Fabry-Perot cavity used for measuring temperature is formed between the upper surface and the lower surface of the sensitive diaphragm; and the optical element is used for emitting light and enabling the light to enter the optical fiber Fabry-Perot cavity for measuring the pressure and the optical fiber Fabry-Perot cavity for measuring the temperature. According to the invention, the measurement of two parameters of pressure difference and temperature can be realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of fiber optic sensing, and particularly to a dual-parameter sensing system based on fiber optic Fabry-Perot, and an inspection method and a demodulation method thereof. Background Art

[0002] Fiber optic sensors have increasingly become a research hotspot due to their advantages such as small size, light weight, high sensitivity, immunity to electromagnetic interference, and corrosion resistance. Fiber optic sensors transmit signals through optical fibers, enabling them to have unique advantages in measuring physical parameters over long distances and in complex environments. As an important type of fiber optic sensor, fiber optic Fabry-Perot sensors have the advantages of simple structure and convenient preparation, and have an important impact on the measurement of physical quantities such as temperature, pressure, and vibration. Sensors integrating multiple physical quantities based on the Fabry-Perot principle are an important research direction in the current sensor field.

[0003] A differential pressure sensor is a sensor used to measure the difference between two pressures. By measuring the pressure difference at different positions as an important reference index for evaluation, it has important applications in aerospace, petrochemical, civil water conservancy projects, and safety monitoring. The complexity of the environment in which differential pressure sensors are used, such as high temperature and low temperature, places higher requirements on the performance of the sensors. Electrical sensors are subject to electromagnetic interference, and physical quantities such as resistance change in high and low temperature environments, affecting the measurement accuracy.

[0004] Integrating temperature and pressure fiber optic sensors not only can reduce the manufacturing cost, but also can reduce the installation space. Therefore, it is necessary to develop a dual-parameter sensing system for differential pressure and temperature. Summary of the Invention

[0005] The present disclosure is completed in view of the above-mentioned prior art situations, and its purpose is to provide a dual-parameter sensing system based on fiber optic Fabry-Perot, and an inspection method and a demodulation method thereof.

[0006] To this end, the first aspect of the present disclosure provides a device including a sensitive diaphragm, an optical element, and at least one base component; a concave groove is provided on one side of the base component; the sensitive diaphragm is connected to the base component to form at least one fiber optic Fabry-Perot cavity for measuring pressure that includes the groove, and a fiber optic Fabry-Perot cavity for measuring temperature is formed between the upper surface and the lower surface of the sensitive diaphragm; the optical element is used to emit light and make the light enter the fiber optic Fabry-Perot cavity for measuring pressure and the fiber optic Fabry-Perot cavity for measuring temperature. It should be noted that when the fiber optic Fabry-Perot cavity for measuring pressure is a vacuum cavity, the measured pressure difference is the pressure difference between the pressure-sensitive surface and the vacuum environment, that is, the absolute pressure. When the fiber optic Fabry-Perot cavity for measuring pressure is a non-vacuum cavity, the measured pressure difference is the pressure difference between the pressure-sensitive surface and the standard atmospheric pressure, that is, the gauge pressure.

[0007] In the dual-parameter sensing system according to the first aspect of the present disclosure, optionally, the base member is provided with a pressure guiding hole, and the pressure guiding hole communicates the fiber optic Fabry-Perot cavity for measuring pressure with the outside. It should be noted that when the pressure guiding hole is provided, the measured pressure difference is the pressure difference between the pressure sensing surface and the pressure guiding hole.

[0008] In the dual-parameter sensing system according to the first aspect of the present disclosure, optionally, the base member includes an upper base and a lower base; the sensitive diaphragm is disposed between the upper base and the lower base, and both sides of the upper base and the lower base connected to the sensitive diaphragm have grooves; the fiber optic Fabry-Perot cavity for measuring pressure includes a first fiber optic Fabry-Perot cavity and a second fiber optic Fabry-Perot cavity. The upper base and the sensitive diaphragm are connected to form the first fiber optic Fabry-Perot cavity including the groove of the upper base, and the lower base and the sensitive diaphragm are connected to form the second fiber optic Fabry-Perot cavity including the groove of the lower base; the upper base is provided with a first pressure guiding hole, and the first pressure guiding hole communicates the first fiber optic Fabry-Perot cavity with an external pressure pipeline; the lower base is provided with a second pressure guiding hole, and the second pressure guiding hole communicates the second fiber optic Fabry-Perot cavity with another external pressure pipeline. It should be noted that in the dual-parameter sensing system based on fiber optic Fabry, the sensitive diaphragm deforms due to the differential pressure, and then the center of the sensitive diaphragm generates a displacement change, resulting in a change in the cavity lengths of the first fiber optic Fabry sensor and the second fiber optic Fabry sensor. Thus, the pressure difference can be measured by measuring the changes in the cavity lengths of the first fiber optic Fabry sensor and the second fiber optic Fabry sensor. In addition, the sensitive diaphragm will undergo thermal expansion in a high-temperature environment. By measuring and calculating the thickness of the sensitive diaphragm, that is, the cavity length of the third fiber optic Fabry cavity, the temperature of the environment where the dual-parameter sensing system based on fiber optic Fabry is located can be obtained. Thus, the acquisition of the dual parameters of pressure difference and temperature can be realized.

[0009] In the dual-parameter sensing system according to the first aspect of the present disclosure, optionally, the first pressure guiding hole is eccentrically disposed with respect to the center of the first fiber optic Fabry-Perot cavity, and the second pressure guiding hole is eccentrically disposed with respect to the center of the second fiber optic Fabry-Perot cavity. Thus, the influence of the pressure guiding hole on the measurement of the cavity length at the central position can be reduced.

[0010] In the dual-parameter sensing system according to the first aspect of the present disclosure, optionally, the first pressure guiding hole and the second pressure guiding hole are coaxially disposed, or the first pressure guiding hole and the second pressure guiding hole are non-coaxially disposed. Thus, the pressure guiding holes are located on both sides (not at the center), which can reduce the influence on the cavity length reading at the central position, and can facilitate the connection with different external pressure pipelines, which is beneficial to sensor packaging and engineering applications.

[0011] In the dual-parameter sensing system according to the first aspect of the present disclosure, optionally, one or more of the following requirements are satisfied: the fiber optic Fabry-Perot cavity for measuring pressure is cylindrical; the cavity length of the first fiber optic Fabry-Perot cavity and the second fiber optic Fabry-Perot cavity are both cylindrical; the grooves of the upper base and the grooves of the lower base are both cylindrical; the sum of the depths of the grooves of the upper base and the grooves of the lower base is equal to the sum of the cavity lengths of the first fiber optic Fabry-Perot cavity and the second fiber optic Fabry-Perot cavity; the central axes of the first fiber optic Fabry-Perot cavity, the second fiber optic Fabry-Perot cavity, and the third fiber optic Fabry-Perot cavity coincide; the upper base, the sensitive diaphragm, and the lower base are coaxially arranged; the light emitted by the optical element is perpendicular to the surface of the sensitive diaphragm; the light emitted by the optical element coincides with the central axes of the first fiber optic Fabry-Perot cavity, the second fiber optic Fabry-Perot cavity, and the third fiber optic Fabry-Perot cavity; an optical dielectric film is provided on at least one surface of the inner surface of the upper base, the upper surface and the lower surface of the sensitive diaphragm, the inner surface of the lower base, and the outer surface of the lower base.

[0012] In the dual-parameter sensing system according to the first aspect of the present disclosure, optionally, one or more of the following requirements are satisfied: the materials of the upper base, the lower base, and the sensitive diaphragm are independently selected from at least one of the following: quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide; the sensitive diaphragm is made of a transparent material; the optical dielectric film is made of at least one of the following materials: chromium, gold, copper, aluminum, titanium, platinum, silver, magnesium fluoride, silicon dioxide, aluminum oxide, titanium dioxide, silicon nitride, hafnium oxide, zirconium oxide..

[0013] The second aspect of the present disclosure provides an inspection method based on the dual-parameter sensing system according to the first aspect of the present disclosure, including: the pressure in the fiber optic Fabry-Perot cavity for measuring pressure acts on the sensitive diaphragm to cause deformation of the sensitive diaphragm, and temperature affects the sensitive diaphragm to cause expansion or contraction of the sensitive diaphragm; measuring the cavity length of the fiber optic Fabry-Perot cavity for measuring pressure, and obtaining the pressure difference between the fiber optic Fabry-Perot cavity for measuring pressure and the environment according to the corresponding relationship between the cavity length of the fiber optic Fabry-Perot cavity for measuring pressure and pressure; measuring the cavity length of the fiber optic Fabry-Perot cavity for measuring temperature, and obtaining the temperature of the fiber optic Fabry-Perot cavity for measuring temperature through the corresponding relationship between temperature and the cavity length of the fiber optic Fabry-Perot cavity for measuring temperature.

[0014] In the inspection method of the second aspect involved in the present disclosure, optionally, it includes: connecting an external pressure pipeline to the first pressure guiding hole of the upper base and the second pressure guiding hole of the lower base respectively, so that the external pressure acts on the sensitive diaphragm through the first pressure guiding hole and the second pressure guiding hole to cause deformation of the sensitive diaphragm; measuring the cavity lengths of the first fiber optic Fabry-Perot cavity and the second fiber optic Fabry-Perot cavity respectively, and calculating the pressure difference between the first fiber optic Fabry-Perot cavity and the second fiber optic Fabry-Perot cavity through the corresponding relationship between the cavity lengths of the first fiber optic Fabry-Perot cavity and the second fiber optic Fabry-Perot cavity and pressure; measuring the cavity length of the fiber optic Fabry-Perot cavity for measuring temperature, and obtaining the temperature of the fiber optic Fabry-Perot cavity for measuring temperature through the corresponding relationship between temperature and the cavity length of the third fiber optic Fabry-Perot cavity.

[0015] In the inspection method of the second aspect involved in the present disclosure, optionally, the corresponding relationship between the cavity lengths of the first fiber optic Fabry-Perot cavity and the second fiber optic Fabry-Perot cavity and pressure is: , , ; In the formula, represents the change amount of the cavity length of the first fiber optic Fabry-Perot cavity, represents the change amount of the cavity length of the second fiber optic Fabry-Perot cavity, represents the Poisson's ratio of the sensitive diaphragm, E represents the Young's modulus of the sensitive diaphragm, H represents the thickness of the sensitive diaphragm, R1 represents the radius of the first fiber optic Fabry-Perot cavity, R2 represents the radius of the second fiber optic Fabry-Perot cavity, P1 represents the pressure of the first fiber optic Fabry-Perot cavity, P2 represents the pressure of the second fiber optic Fabry-Perot cavity, represents the differential pressure; The corresponding relationship between the temperature and the cavity length of the third fiber optic Fabry-Perot cavity is: ; In the formula, △L represents the change amount of the cavity length of the third fiber optic Fabry-Perot cavity, H represents the thickness of the sensitive diaphragm, △T represents the temperature change, and α represents the thermal expansion coefficient of the sensitive diaphragm.

[0016] A spectral demodulation method for differential pressure and temperature based on an optical fiber Fabry-Perot dual-parameter sensing system provided by the third aspect of the present disclosure includes: forming reflective surfaces of optical fiber Fabry-Perot sensors on the inner surface of the upper base, the upper and lower surfaces of the sensitive diaphragm, and the inner and outer surfaces of the lower base. A first optical fiber Fabry-Perot sensor is formed between the inner surface of the upper base and the upper surface of the sensitive diaphragm, a second optical fiber Fabry-Perot sensor is formed between the inner surface of the lower base and the lower surface of the sensitive diaphragm, and a third optical fiber Fabry-Perot sensor is formed between the upper surface and the lower surface of the sensitive diaphragm. Interference occurs among the optical reflection signals of the inner surface of the upper base, the upper and lower surfaces of the sensitive diaphragm, and the inner surface of the lower base to generate a multi-cavity coupled spectrum. By performing a Fourier transform on the coupled spectrum, the cavity lengths of the first optical fiber Fabry-Perot sensor, the second optical fiber Fabry-Perot sensor, and the third optical fiber Fabry-Perot sensor are obtained respectively. Based on the corresponding relationships between the cavity lengths of the first optical fiber Fabry-Perot cavity and the second optical fiber Fabry-Perot cavity and pressure, the pressure difference between the first optical fiber Fabry-Perot sensor and the second optical fiber Fabry-Perot sensor is calculated. And based on the corresponding relationship between temperature and the cavity length of the third optical fiber Fabry-Perot cavity, the ambient temperature where the third optical fiber Fabry-Perot sensor is located is obtained.

[0017] In the spectral demodulation method of the third aspect involved in the present disclosure, optionally, the formula for the Fourier transform is as follows: , where F (j ) represents the Fourier transform of the interference spectrum; R FP (v) represents the interference spectrum of the sensor in the optical frequency domain; j represents the imaginary unit; e is the base of the exponential function, and the value of e is approximately 2.71828; represents the angular frequency; v represents the ratio of the speed of light to the wavelength, that is, the optical frequency; according to the angular frequency corresponding to the peak position, the corresponding cavity length is obtained: , where c is the speed of light and n represents the refractive index.

[0018] According to the optical fiber Fabry-Perot-based dual-parameter sensing system of the present disclosure, the sensitive diaphragm deforms due to the pressure difference, and then the center of the sensitive diaphragm generates displacement, resulting in a change in the cavity length of the optical fiber Fabry-Perot cavity. Thus, the pressure difference can be measured by measuring the change in the cavity length. In addition, the sensitive diaphragm undergoes thermal expansion in a high-temperature environment. By measuring and calculating the thickness of the sensitive diaphragm, that is, the cavity length of the optical fiber Fabry-Perot cavity used to measure temperature, the temperature of the environment where the optical fiber Fabry-Perot-based dual-parameter sensing system is located can be obtained. Therefore, the acquisition of the two parameters of pressure difference and temperature can be achieved. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of a fiber optic Fabry - Perot based dual - parameter sensing system without a pressure - guiding hole involved in the examples of the present disclosure.

[0020] Figure 2 It is a schematic structural diagram of a fiber optic Fabry - Perot based dual - parameter sensing system with a pressure - guiding hole involved in the examples of the present disclosure.

[0021] Figure 3 It is a schematic structural diagram of a fiber optic Fabry - Perot based dual - parameter sensing system with a first fiber optic Fabry - Perot cavity and a second fiber optic Fabry - Perot cavity involved in the examples of the present disclosure.

[0022] Figure 4 It is a schematic structural diagram of a fiber optic Fabry - Perot based dual - parameter sensing system with another form of optical element involved in the examples of the present disclosure.

[0023] Figure 5 It is a schematic structural diagram of a fiber optic Fabry - Perot based dual - parameter sensing system with yet another form of optical element involved in the examples of the present disclosure.

[0024] Figure 6 It is a schematic structural diagram of a fiber optic Fabry - Perot based dual - parameter sensing system with another form of first pressure - guiding hole and second pressure - guiding hole involved in the examples of the present disclosure.

[0025] Figure 7 It is a schematic process diagram of a fiber optic Fabry - Perot based dual - parameter sensing system involved in the examples of the present disclosure for measuring the cavity lengths of the first fiber optic Fabry - Perot cavity and the second fiber optic Fabry - Perot cavity respectively to calculate the pressure difference.

[0026] Figure 8 It is a schematic diagram of a fiber optic Fabry - Perot based dual - parameter sensing system involved in the examples of the present disclosure for measuring the cavity length of the third fiber optic Fabry - Perot cavity.

[0027] Explanation of reference numerals: 800: Fiber Fabry-Perot based dual-parameter sensing system; 14: Base component; 1000: Fiber Fabry-Perot cavity for pressure measurement; 1: Upper base; 100: Inner surface of the upper base; 2: Sensing diaphragm; 200: Upper surface of the sensing diaphragm; 201: Lower surface of the sensing diaphragm; 3: Lower base; 300: Inner surface of the lower base; 301: Outer surface of the lower base; 4: Optical element; 40: Light; 5: First pressure guiding hole; 501: Central axis of the first pressure guiding hole; 6: Second pressure guiding hole; 601: Central axis of the second pressure guiding hole; 7: Mirror; 8: Groove of the upper base; 9: First fiber Fabry-Perot sensor; 900: First fiber Fabry-Perot cavity; 901: Central axis of the first fiber Fabry-Perot cavity; 10: Second fiber Fabry-Perot sensor; 12: Groove of the lower base; 101: Second fiber Fabry-Perot cavity; 102: Central axis of the second fiber Fabry-Perot cavity; 11: Third fiber Fabry-Perot sensor; 110: Third fiber Fabry-Perot cavity (i.e., fiber Fabry-Perot cavity for temperature measurement); H1: Depth of the groove of the upper base; H2: Depth of the groove of the lower base; L1: Cavity length of the first fiber Fabry-Perot cavity; L2: Cavity length of the second fiber Fabry-Perot cavity; L3: Cavity length of the third fiber Fabry-Perot cavity. Detailed implementation manners

[0028] Hereinafter, with reference to the drawings, the preferred implementation manners of the present disclosure will be described in detail. In the following description, the same reference numerals are assigned to the same components, and repeated descriptions are omitted. In addition, the drawings are only schematic diagrams, and the proportional relationship of the dimensions between components or the shape of components, etc. may be different from the actual ones.

[0029] It should be noted that the terms "include" and "have" in the present disclosure and any variations thereof, for example, a process, method, system, product or device including or having a series of steps or units do not necessarily have to be limited to those steps or units clearly listed, but may include or have other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] In addition, the subheadings and the like involved in the following description of the present disclosure are not intended to limit the content or scope of the present disclosure, and they only serve as a reading prompt. Such subheadings should neither be understood as being used to divide the content of the article, nor should the content under the subheadings be limited only within the scope of the subheadings.

[0031] The present disclosure provides a fiber Fabry-Perot based dual-parameter sensing system 800, Figure 1 which is a schematic structural diagram of the fiber Fabry-Perot based dual-parameter sensing system without a pressure guiding hole involved in the example of the present disclosure. As Figure 1 shown, the fiber Fabry-Perot based dual-parameter sensing system 800 may include: a sensing diaphragm 2, an optical element 4, and at least one base component 14.

[0032] As shown Figure 1 in FIG. 1, the number of the base member 14 is one, and a concave groove is provided on one side of the base member 14. The sensitive diaphragm 2 is connected to the base member 14 to form an optical fiber Fabry-Perot cavity 1000 for measuring pressure, which encloses the groove therein.

[0033] In some examples, the base member 14 is hermetically connected to the sensitive diaphragm 2 so that the corresponding space of the groove forms the optical fiber Fabry-Perot cavity 1000 for measuring pressure.

[0034] In some examples, the sensitive diaphragm 2 includes an upper surface 200 and a lower surface 201. An optical fiber Fabry-Perot cavity for measuring temperature, i.e., the third optical fiber Fabry-Perot cavity 110, is formed between the upper surface 200 and the lower surface 201.

[0035] In some examples, the optical element 4 is configured to emit light 40. The light 40 can enter the optical fiber Fabry-Perot cavity 1000 for measuring pressure and the optical fiber Fabry-Perot cavity 110 for measuring temperature (i.e., the third optical fiber Fabry-Perot cavity 110).

[0036] In some examples, the optical fiber Fabry-Perot cavity 1000 for measuring pressure may be in a cylindrical shape. The present disclosure is not limited thereto, and the optical fiber Fabry-Perot cavity 1000 for measuring pressure may also be in the shapes of a cone, a cuboid, a cube, a triangular prism, a hexagonal prism, etc.

[0037] In some examples, the optical fiber Fabry-Perot cavity 110 for measuring temperature may be in a cylindrical shape. The present disclosure is not limited thereto, and the optical fiber Fabry-Perot cavity 110 for measuring temperature may also be in the shapes of a cone, a cuboid, a cube, a triangular prism, a hexagonal prism, etc.

[0038] In some examples, the light beam emitted by the optical element 4 is perpendicular to the base member 14 or the sensitive diaphragm 2.

[0039] In some examples, the sensitive diaphragm 2 is made of a transparent material.

[0040] In some examples, the sensitive diaphragm 2 deforms when subjected to an external pressure.

[0041] In some examples, the sensitive diaphragm 2 expands or contracts when the temperature changes. In some examples, when the temperature changes, the thickness of the sensitive diaphragm 2 changes.

[0042] In some examples, when the temperature changes, the change in the thickness of the sensitive diaphragm 2 is equal on both sides of the sensitive diaphragm 2. For example, when the temperature changes, the amount of change in the thickness of the sensitive diaphragm 2 above the diaphragm and the amount of change in the thickness of the sensitive diaphragm 2 below the diaphragm are the same. Thus, the measurement of the cavity length difference is not affected, and further, the temperature does not affect the measurement of the pressure difference.

[0043] In some examples, the base member 14 and the sensitive diaphragm 2 can be used independently of each other, but are not limited to being made of any one of quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide, and ceramic materials. In other words, the base member 14 can be made of, but is not limited to, any one of quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide, and ceramic materials, and the sensitive diaphragm 2 can be made of, but is not limited to, any one of quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide, and ceramic materials. The materials of the base member 14 and the sensitive diaphragm 2 can be the same or different.

[0044] In some examples, the fiber optic Fabry - Perot cavity 1000 for measuring pressure can be a vacuum cavity or a non - vacuum cavity.

[0045] The present disclosure also provides a method for inspecting the pressure difference and temperature of the above - mentioned fiber optic Fabry - Perot - based dual - parameter sensing system 800.

[0046] In some examples, when the number of fiber optic Fabry - Perot cavities 1000 for measuring pressure in the fiber optic Fabry - Perot - based dual - parameter sensing system 800 is one, and the fiber optic Fabry - Perot cavity 1000 for measuring pressure is in a closed state (i.e., as shown in Figure 1 ), and the fiber optic Fabry - Perot cavity 1000 for measuring pressure is a vacuum cavity, the pressure difference between the pressure - sensing surface (i.e., the upper surface 200 of the sensitive diaphragm 2) and the vacuum environment can be measured, that is, the absolute pressure is measured.

[0047] In some examples, when the number of fiber optic Fabry - Perot cavities 1000 for measuring pressure in the fiber optic Fabry - Perot - based dual - parameter sensing system 800 is one, and the fiber optic Fabry - Perot cavity 1000 for measuring pressure is in a closed state (i.e., as shown in Figure 1 ), and the fiber optic Fabry - Perot cavity 1000 for measuring pressure is a non - vacuum cavity, the pressure difference between the pressure - sensing surface (i.e., the upper surface 200 of the sensitive diaphragm 2) and the standard atmospheric pressure can be measured, that is, the gauge pressure is measured.

[0048] Figure 2 FIG. shows the structural schematic diagram of the fiber optic Fabry - Perot - based dual - parameter sensing system 800 including a pressure - guiding hole 50 involved in the examples of the present disclosure.

[0049] As shown in Figure 2 , in some examples, the base member 14 can also be provided with a pressure - guiding hole 50.

[0050] In some examples, the pressure - guiding hole 50 communicates with the fiber optic Fabry - Perot cavity 1000 for measuring pressure. Through the pressure - guiding hole 50, the fiber optic Fabry - Perot cavity 1000 for measuring pressure can be communicated with the external pressure.

[0051] In some examples, when the number of fiber optic Fabry-Perot cavities 1000 for measuring pressure in the fiber optic Fabry-Perot based dual-parameter sensing system 800 is one, and the fiber optic Fabry-Perot cavity 1000 for measuring pressure is in a state of being connected to the outside world (that is, as shown in Figure 2 ), the fiber optic Fabry-Perot based dual-parameter sensing system 800 can measure the difference in pressure between the pressure sensing surface (that is, the upper surface 200 of the sensitive diaphragm 2) and the pressure tapping hole.

[0052] In some examples, when the number of fiber optic Fabry-Perot cavities 1000 for measuring pressure in the fiber optic Fabry-Perot based dual-parameter sensing system 800 is one, the corresponding relationship between the cavity length of the fiber optic Fabry-Perot cavity 1000 for measuring pressure and the pressure is: ; '; In the formula, represents the change in cavity length of the fiber optic Fabry-Perot cavity 1000 for measuring pressure (unit: mm, millimeter), represents the Poisson's ratio of the sensitive diaphragm 2, E represents the Young's modulus of the sensitive diaphragm 2 (unit: Pa, Pascal), H represents the thickness of the sensitive diaphragm 2 (unit: mm, millimeter), R represents the radius of the fiber optic Fabry-Perot cavity 1000 for measuring pressure (unit: mm, millimeter), P represents the pressure on the pressure sensing surface (that is, the surface of the sensitive diaphragm 2 close to the fiber optic Fabry-Perot cavity 1000 for measuring pressure) (unit: Pa, Pascal), P’ represents the pressure in vacuum, standard atmospheric pressure or at the pressure tapping hole (unit: Pa, Pascal). If the fiber optic Fabry-Perot cavity 1000 for measuring pressure is a vacuum cavity, then the value of P’ is 0; if the fiber optic Fabry-Perot cavity 1000 for measuring pressure is a non-vacuum cavity, then the value of P’ is the standard atmospheric pressure; represents the differential pressure; The corresponding relationship between temperature and the cavity length of the third fiber optic Fabry-Perot cavity 110 (or called: the fiber optic Fabry-Perot cavity 110 for measuring temperature) is: ; In the formula, represents the change in cavity length of the third fiber optic Fabry-Perot cavity 110 (unit: mm, millimeter), H represents the thickness of the sensitive diaphragm 2 (unit: mm, millimeter), represents the temperature change (unit: °C, degree Celsius), α represents the thermal expansion coefficient of the sensitive diaphragm 2 (unit: 1 / °C, per degree Celsius).

[0053] It should be noted that the temperature can be calculated not only from the deformation of the sensitive diaphragm 2 (i.e., the change in the cavity length of the third fiber Fabry-Perot cavity 110), but also from the change in the thickness of the base member 14, that is, it can be calculated from the change in the cavity length of the Fabry-Perot cavity formed between the two surfaces of the base member 14.

[0054] The present disclosure also provides a spectral demodulation method for a dual-parameter sensing system 800 based on the above-mentioned fiber Fabry-Perot, including: forming the inner surface of the base member 14, the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2 as the reflecting surfaces of the fiber Fabry-Perot sensor, the inner surface of the base member 14 and the upper surface 200 of the sensitive diaphragm 2 forming a fiber Fabry-Perot cavity 1000 for measuring pressure, and the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2 forming a third fiber Fabry-Perot cavity 110 (or referred to as: a fiber Fabry-Perot cavity 110 for measuring temperature); causing the optical reflection signals of the inner surface of the base member 14, the upper surface 200 and the lower surface 200 of the sensitive diaphragm 2 to interfere to generate a multi-cavity coupling spectrum, and by performing a Fourier transform on the coupling spectrum, respectively obtaining the cavity lengths of the fiber Fabry-Perot cavity 1000 for measuring pressure and the third fiber Fabry-Perot cavity 110, calculating the pressure difference between the fiber Fabry-Perot cavity 1000 for measuring pressure and the outside through the corresponding relationship between the cavity length of the fiber Fabry-Perot cavity 1000 for measuring pressure and the pressure; and obtaining the ambient temperature at which the third fiber Fabry-Perot cavity 110 is located through the corresponding relationship between the temperature and the third fiber Fabry-Perot cavity 110.

[0055] In some examples, the formula for the Fourier transform is as follows: , where F (j ) represents the Fourier transform of the interference spectrum; R FP (v) represents the interference spectrum of the sensor in the optical frequency domain; j represents the imaginary unit; e is the base of the exponential function, and the value of e is approximately 2.71828; represents the angular frequency (unit: rad / s, radians per second); v represents the ratio of the speed of light to the wavelength, that is, the optical frequency (unit: Hz, hertz); according to the angular frequency corresponding to the peak position the corresponding cavity length is obtained , in the formula, c is the speed of light (3×10 8 m / s), and n represents the refractive index.

[0056] The present disclosure also provides a dual-parameter sensing system 800 based on fiber Fabry-Perot for measuring the pressure difference on both sides of the sensitive diaphragm 2, its inspection method, and spectral demodulation method.

[0057] Figure 3 It is a schematic structural diagram of a fiber optic Fabry - Perot based dual - parameter sensing system 800 including a first fiber optic Fabry - Perot cavity 900 and a second fiber optic Fabry - Perot cavity 101 related to the examples of the present disclosure.

[0058] As Figure 3 shown, the number of fiber optic Fabry - Perot cavities 1000 for measuring pressure can be two. The base member 14 may include an upper base 1 and a lower base 3. The fiber optic Fabry - Perot based dual - parameter sensing system 800 may include: an upper base 1, a sensitive diaphragm 2, a lower base 3, and an optical element 4.

[0059] In some examples, the sensitive diaphragm 2 is disposed between the upper base 1 and the lower base 3.

[0060] In some examples, both sides of the upper base 1 and the lower base 3 connected to the sensitive diaphragm 2 have grooves.

[0061] In some examples, a groove 8 is provided on the side of the upper base 1 connected to the sensitive diaphragm 2, that is, the groove 8 of the upper base 1. The connection between the upper base 1 and the sensitive diaphragm 2 forms a first fiber optic Fabry - Perot cavity 900 including the groove 8 of the upper base 1.

[0062] In some examples, the inner surface 100 of the upper base 1 and the upper surface 200 of the sensitive diaphragm 2 form a first fiber optic Fabry - Perot sensor 9.

[0063] In some examples, a groove 12 is provided on the side of the lower base 3 connected to the sensitive diaphragm 2, that is, the groove 12 of the lower base 3.

[0064] In some examples, the connection between the lower base 3 and the sensitive diaphragm 2 forms a second fiber optic Fabry - Perot cavity 101 including the groove 12 of the lower base 3.

[0065] In some examples, the inner surface 300 of the lower base 3 and the lower surface 201 of the sensitive diaphragm 2 form a second fiber optic Fabry - Perot sensor 10.

[0066] In some examples, the inner surface 300 and the outer surface 301 of the lower base 3 are parallel.

[0067] In some examples, the inner surface 100 of the upper base 1 and the inner surface 300 of the lower base 3 are parallel.

[0068] In some examples, the upper base 1 is provided with a first pressure - guiding hole 5, and the first pressure - guiding hole 5 communicates with the first fiber optic Fabry - Perot cavity 900.

[0069] In some examples, the lower base 3 is provided with a second pressure - guiding hole 6, and the second pressure - guiding hole 6 communicates with the second fiber optic Fabry - Perot cavity 101.

[0070] In some examples, the first pressure tapping hole 5 and the second pressure tapping hole 6 are used to connect to external pressure pipelines respectively to test the differential pressure. The pressure difference between the first fiber optic Fabry-Perot sensor 9 and the second fiber optic Fabry-Perot sensor 10 can be regarded as the pressure difference between the two pressure tapping holes. Theoretically, the interconnected pressures should be the same.

[0071] In some examples, a third fiber optic Fabry-Perot cavity 110 is formed between the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2. The upper surface 200 and the lower surface 201 of the sensitive diaphragm 2 form a third fiber optic Fabry-Perot sensor 11.

[0072] In some examples, the sensitive diaphragm 2 divides the fiber optic Fabry-Perot sensor into a first fiber optic Fabry-Perot sensor 9 and a second fiber optic Fabry-Perot sensor 10. The first fiber optic Fabry-Perot cavity 900 of the formed first fiber optic Fabry-Perot sensor 9 and the second fiber optic Fabry-Perot cavity 101 of the second fiber optic Fabry-Perot sensor 10 are used for differential pressure measurement, and the third fiber optic Fabry-Perot cavity 110 of the third fiber optic Fabry-Perot sensor 11 is used for temperature measurement.

[0073] In some examples, for the fiber optic Fabry-Perot based dual-parameter sensing system 800 of the present disclosure, the cavity lengths of the first fiber optic Fabry-Perot cavity 900, the second fiber optic Fabry-Perot cavity 101, and the third fiber optic Fabry-Perot cavity 110 can be read by using one optical fiber as the optical element 4. Thereby, it is beneficial to reduce the volume of the sensor, reduce its weight, and simplify the structural complexity of the fiber optic Fabry-Perot sensor.

[0074] In some examples, by providing the first pressure tapping hole 5 on the upper base 1 and the second pressure tapping hole 6 on the lower base 3 respectively on both sides of the sensitive diaphragm 2, it is convenient to connect to different external pressure pipelines respectively, which is beneficial to sensor packaging and engineering applications.

[0075] In some examples, for the fiber optic Fabry-Perot based dual-parameter sensing system 800 of the present disclosure, signal transmission is performed through the optical element 4, and the cavity lengths of the first fiber optic Fabry-Perot cavity 900 of the first fiber optic Fabry-Perot sensor 9, the second fiber optic Fabry-Perot cavity 101 of the second fiber optic Fabry-Perot sensor 10, and the third fiber optic Fabry-Perot cavity 110 of the third fiber optic Fabry-Perot sensor 11 can be read simultaneously, realizing simultaneous measurement of the dual parameters of temperature and differential pressure.

[0076] Figure 6 FIG. shows a schematic structural diagram of a fiber optic Fabry-Perot based dual-parameter sensing system 800 having another form of the first pressure tapping hole 5 and the second pressure tapping hole 6 involved in the examples of the present disclosure. The fiber optic Fabry-Perot based dual-parameter sensing system 800 of the present disclosure, as Figure 3 and Figure 6As shown, the first pressure guiding hole 5 is eccentrically arranged with respect to the center of the first fiber optic Fabry-Perot cavity 901, and the second pressure guiding hole 6 is eccentrically arranged with respect to the center of the second fiber optic Fabry-Perot cavity 101. Thus, it is beneficial to avoid the influence of the pressure guiding holes on the measurement of the cavity length at the center position of the first fiber optic Fabry-Perot cavity 901 or the second fiber optic Fabry-Perot cavity 101.

[0077] Figure 4 FIG. 4 is a schematic structural diagram of a fiber optic Fabry-based dual-parameter sensing system 800 having an optical element 4 in another form according to an example of the present disclosure. Figure 5 FIG. 5 is a schematic structural diagram of a fiber optic Fabry-based dual-parameter sensing system 800 having an optical element 4 in yet another form according to an example of the present disclosure.

[0078] As Figure 4 shown, taking the central axis 901 of the first fiber optic Fabry-Perot cavity 900 as the center of the first fiber optic Fabry-Perot cavity 900 and the central axis 102 of the second fiber optic Fabry-Perot cavity 101 as the center of the second fiber optic Fabry-Perot cavity 101, the first pressure guiding hole 5 is eccentric with respect to the central axis 901 of the first fiber optic Fabry-Perot cavity 900 and is arranged on the right side, and the second pressure guiding hole 6 is eccentric with respect to the central axis 102 of the second fiber optic Fabry-Perot cavity 101 and is arranged on the right side. In some examples, as Figure 3 shown, the first pressure guiding hole 5 and the second pressure guiding hole 6 are coaxially arranged, that is, the central axis 501 of the first pressure guiding hole 5 and the central axis 601 of the second pressure guiding hole 6 coincide.

[0079] In other examples, as Figure 6 shown, the first pressure guiding hole 5 and the second pressure guiding hole 6 can be non-coaxially arranged, that is, the central axis 501 of the first pressure guiding hole 5 and the central axis 601 of the second pressure guiding hole 6 do not coincide, and there is a certain distance between them. For example, the first pressure guiding hole 5 and the second pressure guiding hole 6 can be arranged on different sides (for example, the first pressure guiding hole 5 is on the left side and the second pressure guiding hole 6 is on the right side), or arranged on the same side but the central axes do not coincide.

[0080] In some examples, as Figures 3 to 6 shown, in the fiber optic Fabry-based dual-parameter sensing system, the upper base 1, the sensitive diaphragm 2, and the lower base 3 are coaxially arranged.

[0081] In some examples, grooves are provided on one side of the upper base 1 and the lower base 3 connected to the sensitive diaphragm 2, which are groove 8 and groove 12 respectively. After the upper base 1 and the lower base 3 are connected to the sensitive diaphragm 2, the first fiber optic Fabry-Perot cavity 900 and the second fiber optic Fabry-Perot cavity 101 are respectively formed by the grooves of the upper base 1 and the lower base 3. The first fiber optic Fabry-Perot cavity 900 includes the groove 8 of the upper base 1, and the second fiber optic Fabry-Perot cavity 101 includes the groove 12 of the lower base 3.

[0082] In some examples, asFigure 6 As shown, the depth of the groove 8 of the upper base is H1, and the depth of the groove 12 of the lower base is H2. The cavity length of the first fiber optic Fabry-Perot cavity 900 is L1, and the cavity length of the second fiber optic Fabry-Perot cavity 101 is L2. The thickness of the sensitive diaphragm 2 is H3, and the cavity length of the third fiber optic Fabry-Perot cavity 110 is L3.

[0083] In some examples, the cavity length L1 of the first fiber optic Fabry-Perot cavity 900 refers to the distance between the upper base 1 and the sensitive diaphragm 2 at the central position of the first fiber optic Fabry-Perot cavity 900.

[0084] In some examples, the cavity length L2 of the second fiber optic Fabry-Perot cavity 101 refers to the distance between the lower base 3 and the sensitive diaphragm 2 at the central position of the second fiber optic Fabry-Perot cavity 101.

[0085] In some examples, the cavity length L3 of the third fiber optic Fabry-Perot cavity 110 refers to the thickness at the central position of the sensitive diaphragm 2.

[0086] In some examples, the central axis 901 of the first fiber optic Fabry-Perot cavity 900 coincides with the central axis 102 of the second fiber optic Fabry-Perot cavity 101.

[0087] In some examples, the central axis 901 of the first fiber optic Fabry-Perot cavity 900, the central axis 102 of the second fiber optic Fabry-Perot cavity 101, and the central axis of the third fiber optic Fabry-Perot cavity 110 all coincide.

[0088] In some examples, the central axes of the upper base 1, the lower base 3, and the sensitive diaphragm 2 all coincide.

[0089] In some examples, H1 + H2 = L1 + L2.

[0090] Figure 7 It is a schematic diagram showing the process of the fiber optic Fabry-Perot-based dual-parameter sensing system 800 involved in the examples of the present disclosure measuring the cavity lengths of the first fiber optic Fabry-Perot cavity 900 and the second fiber optic Fabry-Perot cavity 101 respectively to calculate the pressure difference. Figure 8 It is a schematic diagram showing the fiber optic Fabry-Perot-based dual-parameter sensing system 800 involved in the examples of the present disclosure measuring the cavity length of the third fiber optic Fabry-Perot cavity 110.

[0091] In some examples, when the sensitive diaphragm 2 is subjected to an external pressure, it will deform (refer to Figure 7 )

[0092] In some examples, when the sensitive diaphragm 2 is not subjected to an external pressure, H1 = L1 and H2 = L2.

[0093] In some examples, when the temperature changes, the sensitive diaphragm 2 will expand or contract (refer to Figure 8). In some examples, when the temperature changes, the thickness of the sensitive diaphragm 2 changes.

[0094] In some examples, when the temperature changes, the change in the thickness of the sensitive diaphragm 2 is equal on both sides of the sensitive diaphragm 2. For example, when the temperature changes, the amount of thickness change of the sensitive diaphragm 2 above the diaphragm and the amount of thickness change below the diaphragm are the same. Thus, it does not affect the measurement of the cavity length difference, and furthermore, the temperature does not affect the measurement of the pressure difference.

[0095] In some examples, in the dual-parameter sensing system 800 based on fiber optic Fabry-Perot of the present disclosure, the upper base 1 and the lower base 3 can be respectively prepared with grooves through wafer processing. It can also be prepared from one wafer and another wafer with grooves or through holes.

[0096] In some examples, the first fiber optic Fabry-Perot cavity 900 can be in a cylindrical shape. In some examples, the second fiber optic Fabry-Perot cavity 101 can be in a cylindrical shape. The present disclosure is not limited to this, and the first fiber optic Fabry-Perot cavity 900 or the second fiber optic Fabry-Perot cavity 101 can also be in the shapes of a cone, a cuboid, a cube, a triangular prism, a hexagonal prism, etc. In some examples, both the upper base 1 and the lower base 3 are provided with grooves, and the fiber optic Fabry-Perot cavity is formed by the grooves of the upper base 1 and the lower base 3; wherein, the diameter of the groove is equal to the diameter of the first fiber optic Fabry-Perot cavity 900 or the diameter of the second fiber optic Fabry-Perot cavity 101.

[0097] In some examples of the present disclosure, the grooves can be processed by methods such as MEMS, CNC, etching, and engraving.

[0098] In some examples, the inner surface 100 of the upper base 1, the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2, and the inner surface 300 and the outer surface 301 of the lower base 3 are all parallel to each other between every two surfaces.

[0099] In some examples, the light (or light beam) emitted by the optical element 4 passes through all the fiber optic Fabry-Perot cavities. In some examples, the light (or light beam) emitted by the optical element 4 passes through the fiber optic Fabry-Perot cavity 1000 for measuring pressure and the fiber optic Fabry-Perot cavity 110 for measuring temperature, or the light (or light beam) emitted by the optical element 4 passes through the first fiber optic Fabry-Perot cavity 900, the second fiber optic Fabry-Perot cavity 101, and the third fiber optic Fabry-Perot cavity 110.

[0100] In some examples, the light (or light beam) emitted by the optical element 4 is perpendicular to the inner surface 300 of the lower base 3.

[0101] In some examples, such as Figure 3As shown, the optical element 4 is arranged perpendicular to the lower base 3. By arranging the optical element 4 perpendicular to the lower base 3, the light (or light beam) emitted by the optical element 4 can effectively measure the cavity lengths of the first fiber Fabry-Perot cavity 900 and the second fiber Fabry-Perot cavity 101.

[0102] In some examples, as Figure 4 shown, the optical element 4 is arranged horizontally with respect to the lower base 3, and the end face of the optical element 4 forms a mirror 7. Through the mirror 7, the light (or light beam) emitted by the optical element 4 can effectively measure the cavity lengths of the first fiber Fabry-Perot cavity 900 and the second fiber Fabry-Perot cavity 101.

[0103] In some examples, as Figure 5 shown, the optical element 4 is arranged horizontally with respect to the lower base 3, and a mirror 7 is placed. The light (or light beam) emitted by the optical element 4 can effectively measure the cavity lengths of the first fiber Fabry-Perot cavity 900 and the second fiber Fabry-Perot cavity 101.

[0104] It should be noted that although Figure 3 、 Figure 4 and Figure 5 illustrate several setting methods of the optical element 4, the setting method of the optical element 4 is not limited to this. For example, Figure 4 the optical element 4 in

[0105] is also arranged closely against the outer surface 301 of the lower base 3 to reduce the installation space.

[0106] In some examples, the light (or light beam) of the optical element 4 coincides with the central axis of the fiber Fabry-Perot cavity 1000 for measuring pressure and the central axis of the third fiber Fabry-Perot cavity 110 (or referred to as: the fiber Fabry-Perot cavity 110 for measuring temperature).

[0107] In some examples, the light (or light beam) of the optical element 4 coincides with the central axis 901 of the first fiber Fabry-Perot cavity 900 and the central axis 102 of the second fiber Fabry-Perot cavity 101.

[0108] The light (or light beam) of the optical element 4 coincides with the central axis 901 of the first fiber Fabry-Perot cavity 900, the central axis 102 of the second fiber Fabry-Perot cavity 101, and the central axis of the third fiber Fabry-Perot cavity 110.

[0109] In some examples, an optical dielectric film (not shown in the drawings) can be provided on the surface of the base member 14 and the surface of the sensitive diaphragm 2.

[0110] In some examples, optical dielectric films may be provided on the inner surface 100 of the upper base 1, the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2, and the inner surface 300 and the outer surface 301 of the lower base 3.

[0111] In some examples, the optical dielectric film may be formed by at least one of the following methods: physical vapor deposition, chemical vapor deposition, ion beam assisted deposition, multi-layer film stacking technology, sol-gel method, electrochemical deposition, magnetron sputtering, molecular beam epitaxy, self-assembly method, and spraying.

[0112] In some examples, the optical dielectric film includes an anti-reflection film and an anti-reflection film.

[0113] In some examples, the material of the optical dielectric film may include at least one of the following: chromium, gold, copper, aluminum, titanium, platinum, silver, magnesium fluoride, silicon dioxide, aluminum oxide, titanium dioxide, silicon nitride, hafnium oxide, zirconium oxide. Thus, the transmission or reflection of light can be increased by the optical dielectric film.

[0114] In some examples, an anti-reflection film may be provided on the inner surface 100 of the upper base 1, the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2, and the inner surface 300 of the lower base 3. The material of the anti-reflection film may include at least one of the following: chromium, gold, copper, aluminum, titanium, platinum, silver. The anti-reflection film may be formed by at least one of the following methods: physical vapor deposition, chemical vapor deposition, sol-gel method, spraying method, spin coating method, dipping method, ion beam assisted deposition, self-assembly method, electrochemical deposition, multi-layer film stacking technology.

[0115] In some examples, an anti-reflection film may be provided on the outer surface 301 of the lower base 3. The material of the anti-reflection film may include at least one of the following: magnesium fluoride, silicon dioxide, aluminum oxide, titanium dioxide, silicon nitride, hafnium oxide, zirconium oxide. The anti-reflection film may be formed by at least one of the following methods: physical vapor deposition, chemical vapor deposition, sol-gel method, spraying method, spin coating method, dipping method, ion beam assisted deposition, self-assembly method, electrochemical deposition, multi-layer film stacking technology. By providing an anti-reflection film on the outer surface 301 of the lower base 3, the transmittance of the light beam emitted by the optical element 4 can be increased, which is beneficial to improving the measurement accuracy of the fiber optic Fabry-Perot based dual-parameter sensing system 800.

[0116] In some examples, as Figures 3 to 6 shown, the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2 are arranged in parallel so that the fiber optic Fabry-Perot based dual-parameter sensing system can accurately measure the change in the cavity length of the third fiber optic Fabry-Perot cavity 110.

[0117] In some examples, the upper base 1, the lower base 3, and the sensitive diaphragm 2 are connected by any one of high-temperature bonding, anodic bonding, welding, and gluing. Connecting the upper base 1, the sensitive diaphragm 2, and the lower base 3 together in the above manner can meet the measurement requirements of the fiber optic Fabry-Perot-based dual-parameter sensing system under different environments such as high temperature, low temperature, and normal temperature.

[0118] In some examples, the upper base 1, the lower base 3, and the sensitive diaphragm 2 can each be independently used but are not limited to being made of any one of quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide, and ceramic materials. In other words, the upper base 1 can be made of but is not limited to any one of quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide, and ceramic materials, the lower base 3 can be made of but is not limited to any one of quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide, and ceramic materials, the sensitive diaphragm 2 can be made of but is not limited to any one of quartz, silicon, sapphire, magnesium oxide, silicon carbide, gallium arsenide, and ceramic materials, and the materials of the upper base 1, the lower base 3, and the sensitive diaphragm 2 can be the same or different.

[0119] In some examples, the upper base 1, the sensitive diaphragm 2, and the lower base 3 can all be independently prepared using MEMS (Micro-Electro-Mechanical Systems) wafer-level processing.

[0120] As Figure 7 shown, the present disclosure provides a differential pressure inspection method for a fiber optic Fabry-Perot-based dual-parameter sensing system 800, including: Connecting the external pressure pipeline to the first pressure guiding hole 5 of the upper base 1 and the second pressure guiding hole 6 of the lower base 3 respectively, so that the external pressure acts on the sensitive diaphragm 2 through the first pressure guiding hole 5 and the second pressure guiding hole 6, causing deformation of the sensitive diaphragm 2; Measuring the cavity length L1 of the first fiber optic Fabry-Perot cavity 900 and the cavity length L2 of the second fiber optic Fabry-Perot cavity 101, and calculating the pressure difference between the first fiber optic Fabry-Perot sensor 9 and the second fiber optic Fabry-Perot sensor 10 through the corresponding relationship between the cavity length L1 and the cavity length L2 and the pressure.

[0121] In some examples, the corresponding relationship between the cavity length of each of the first fiber optic Fabry-Perot cavity 900 and the second fiber optic Fabry-Perot cavity 101 and the pressure is: , , ; In the formula, represents the change in the cavity length of the first fiber optic Fabry-Perot cavity 900 (unit: mm, millimeter), represents the change in the cavity length of the second fiber optic Fabry-Perot cavity 101 (unit: mm, millimeter), denotes the Poisson's ratio of the sensitive diaphragm 2, E denotes the Young's modulus of the sensitive diaphragm 2 (unit: Pa, Pascal), H denotes the thickness of the sensitive diaphragm 2 (unit: mm, millimeter), R1 denotes the radius of the first fiber optic Fabry-Perot cavity 900 (unit: mm, millimeter), R2 denotes the radius of the second fiber optic Fabry-Perot cavity 101 (unit: mm, millimeter), P1 denotes the pressure of the first fiber optic Fabry-Perot cavity 900 (unit: Pa, Pascal), P2 denotes the pressure of the second fiber optic Fabry-Perot cavity 101 (unit: Pa, Pascal), denotes the differential pressure on both sides (unit: Pa, Pascal).

[0122] Such as Figure 8 shown, the present disclosure provides a temperature detection method based on the fiber optic Fabry-Perot dual-parameter sensing system 800, including: Parallelly arrange the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2, measure the cavity length L3 of the third fiber optic Fabry-Perot cavity 110, and obtain the ambient temperature where the third fiber optic Fabry-Perot sensor 11 is located through the corresponding relationship between the temperature and the cavity length L3 of the third fiber optic Fabry-Perot cavity.

[0123] The temperature detection method of the fiber optic Fabry-Perot dual-parameter sensing system of the present disclosure utilizes the fact that the sensitive diaphragm 2 will undergo thermal expansion in a high-temperature environment. By measuring and calculating the change in the thickness of the sensitive diaphragm 2, that is, the change in the cavity length L3 of the third fiber optic Fabry-Perot cavity 110, the temperature of the environment where the fiber optic Fabry-Perot-based dual-parameter sensing system 800 is located is obtained, so that the differential pressure and temperature dual-parameters can be obtained through the fiber optic Fabry-Perot-based dual-parameter sensing system 800.

[0124] In some examples, the corresponding relationship between the temperature and the cavity length of the third fiber optic Fabry-Perot cavity is: ; In the formula, denotes the change in the cavity length of the third fiber optic Fabry-Perot cavity 110 (unit: mm, millimeter), H denotes the thickness of the sensitive diaphragm 2 (unit: mm, millimeter), T denotes the temperature change (unit: °C, degree Celsius), and α denotes the thermal expansion coefficient of the sensitive diaphragm 2 (unit: 1 / °C, per degree Celsius).

[0125] It should be noted that the temperature can be calculated not only from the deformation amount of the sensitive diaphragm 2 (that is, the change amount of the cavity length of the third fiber optic Fabry-Perot cavity 110), but also from the change amount of the thickness of the base component 14, that is, it can be calculated from the change amount of the cavity length of the Fabry-Perot cavity formed between the two surfaces of the upper base 1 (or the lower base 3). The present disclosure provides a spectral demodulation method for the differential pressure and temperature of the fiber optic Fabry-Perot dual-parameter sensing system 800, including: The inner surface 100 of the upper base 1, the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2, and the inner surface 300 and the outer surface 300 of the lower base 3 all constitute the reflecting surfaces of the fiber optic Fabry-Perot sensor. The inner surface 100 of the upper base 1 and the upper surface 200 of the sensitive diaphragm 2 form the first fiber optic Fabry-Perot sensor 9. The inner surface 300 of the lower base 3 and the lower surface 201 of the sensitive diaphragm 2 form the second fiber optic Fabry-Perot sensor 10. The upper surface 200 and the lower surface 201 of the sensitive diaphragm 2 form the third fiber optic Fabry-Perot sensor 11; Interference occurs among the optical reflection signals of the inner surface 100 of the upper base 1, the upper surface 200 and the lower surface 201 of the sensitive diaphragm 2, and the inner surface 300 of the lower base 3 to generate a multi-cavity coupled spectrum. By performing Fourier transform on the multi-cavity coupled spectrum, the cavity lengths of the first fiber optic Fabry-Perot sensor 9, the second fiber optic Fabry-Perot sensor 10, and the third fiber optic Fabry-Perot sensor 11 are obtained respectively. Based on the corresponding relationships between the cavity lengths of the first fiber optic Fabry cavity 900 and the second fiber optic Fabry cavity 101 and the pressure, the pressure difference between the first fiber optic Fabry-Perot sensor 9 and the second fiber optic Fabry-Perot sensor 10 is calculated; and based on the corresponding relationship between the cavity length of the third fiber optic Fabry cavity 110 and the temperature change, the ambient temperature where the dual-parameter sensing system 800 based on fiber optic Fabry is located is obtained.

[0126] In some examples, the actual spectrum can be obtained through Fourier transform as follows: , where is the angular frequency (unit: rad / s, radians per second), v is the ratio of the speed of light to the wavelength (unit: Hz, hertz). According to the angular frequency corresponding to the peak position, the corresponding cavity length (unit: m, meter) can be calculated. , where c is the speed of light (3×10 8 m / s), and n is the refractive index.

[0127] In the dual-parameter sensing system 800 based on fiber optic Fabry of the present disclosure, pressure is transmitted to the sensitive diaphragm 2 through the first pressure guiding hole 5 and the second pressure guiding hole 6. The pressure difference causes a change in the displacement of the sensitive diaphragm 2, resulting in a change in the cavity lengths of the first fiber optic Fabry cavity 900 and the second fiber optic Fabry cavity 101. The pressure difference is obtained from the cavity length change. A change in the ambient temperature where the sensor is located will cause a change in the thickness of the sensitive diaphragm 2, resulting in a change in the cavity length of the third fiber optic Fabry cavity 110 formed by the upper and lower surfaces of the sensitive diaphragm 2. Through the mutual relationship between the cavity length change, the temperature change, and the coefficient of thermal expansion of the material, the measurement of the change in the ambient temperature where the sensor is located can be achieved.

[0128] In the present disclosure, the cavity lengths of multiple Fabry cavities can be read by one optical fiber, which is beneficial to reducing the volume of the sensor, reducing the weight, and reducing the complexity of the sensor structure.

[0129] In the present disclosure, the pressure tapping holes are located on both sides, facilitating connection with different external pressure pipelines, which is beneficial to sensor packaging and engineering applications. By integrally integrating an optical fiber Fabry-Perot sensor for measuring temperature and differential pressure, not only can the manufacturing cost of the sensor be reduced, but also the installation space of the dual-parameter sensing system 800 based on optical fiber Fabry-Perot can be reduced.

[0130] The above are only the preferred embodiments of the present disclosure and are not used to limit the present disclosure. For those skilled in the art, the present disclosure can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

[0131] Although the present disclosure has been specifically described above in conjunction with the accompanying drawings and embodiments, it can be understood that the above description does not limit the present disclosure in any form. Those skilled in the art can make deformations and changes to the present disclosure according to needs without departing from the essence and scope of the present disclosure, and these deformations and changes all fall within the scope of the present disclosure.

Claims

1. A dual-parameter sensing system based on optical fiber Fabry-Perot, characterized in that: comprising a sensitive membrane, an optical element and at least one base component; A concave groove is provided on one side of the base component; The sensitive membrane is connected to the base component to form at least one optical fiber Fabry-Perot cavity for measuring pressure, which includes the groove, and an optical fiber Fabry-Perot cavity for measuring temperature is formed between the upper surface and the lower surface of the sensitive membrane; The optical element is used for emitting light and allowing the light to enter the optical fiber Fabry-Perot cavity for measuring pressure and the optical fiber Fabry-Perot cavity for measuring temperature.

2. The dual parameter sensing system according to claim 1, characterized in that: The base component is provided with a pressure-introducing hole, and the pressure-introducing hole enables the optical fiber Fabry-Perot cavity for measuring pressure to communicate with the outside world.

3. The dual parameter sensing system according to claim 2, characterized in that: The base component includes an upper base and a lower base; The sensitive membrane is arranged between the upper base and the lower base, and the upper base and the lower base both have grooves on one side connected to the sensitive membrane; The optical fiber Fabry-Perot cavity for measuring pressure comprises a first optical fiber Fabry-Perot cavity and a second optical fiber Fabry-Perot cavity, wherein the upper base is connected to the sensitive diaphragm to form the first optical fiber Fabry-Perot cavity including the groove of the upper base, and the lower base is connected to the sensitive diaphragm to form the second optical fiber Fabry-Perot cavity including the groove of the lower base; The upper base is provided with a first pressure-introducing hole, which connects the first optical fiber Fabry-Perot cavity with an external pressure pipeline; the lower base is provided with a second pressure-introducing hole, which connects the second optical fiber Fabry-Perot cavity with another external pressure pipeline.

4. The dual parameter sensing system according to claim 3, characterized in that: The first pressure-introducing hole is eccentrically arranged relative to the center of the first optical fiber Fabry-Perot cavity, and the second pressure-introducing hole is eccentrically arranged relative to the center of the second optical fiber Fabry-Perot cavity.

5. The dual parameter sensing system according to any one of claims 3 to 4, characterized in that: Meet one or more of the following requirements: The optical fiber Fabry-Perot cavity for measuring pressure is cylindrical; The cavity length of the first optical fiber Fabry-Perot cavity and the second optical fiber Fabry-Perot cavity are both cylindrical; The groove of the upper base and the groove of the lower base are both cylindrical; The sum of the depth of the groove of the upper base and the depth of the groove of the lower base is equal to the sum of the cavity length of the first optical fiber Fabry-Perot cavity and the cavity length of the second optical fiber Fabry-Perot cavity; The central axes of the first optical fiber Fabry-Perot cavity, the second optical fiber Fabry-Perot cavity, and the third optical fiber Fabry-Perot cavity all coincide with each other; The upper base, the sensitive membrane and the lower base are coaxially arranged; The light emitted by the optical element is perpendicular to the surface of the sensitive film; The light emitted by the optical element coincides with the central axes of the first fiber Fabry-Perot cavity, the second fiber Fabry-Perot cavity, and the third fiber Fabry-Perot cavity; An optical medium film is provided on at least one of the inner surface of the upper base, the upper surface and the lower surface of the sensitive film, and the inner surface of the lower base and the outer surface of the lower base.

6. The dual parameter sensing system according to claim 5, characterized in that: Meet one or more of the following requirements: The materials of the upper base, the lower base, and the sensitive membrane are independently selected from at least one of the following: quartz, silicon, sapphire, magnesium oxide, silicon carbide, and gallium arsenide; The sensitive membrane is made of transparent material; The optical medium film is made of at least one of the following materials: chromium, gold, copper, aluminum, titanium, platinum, silver, magnesium fluoride, silicon dioxide, aluminum oxide, titanium dioxide, silicon nitride, hafnium oxide, and zirconium oxide.

7. A testing method based on the dual parameter sensing system according to any one of claims 1 to 6, characterized in that: include: The pressure in the optical fiber Fabry-Perot cavity for measuring pressure acts on the sensitive diaphragm to cause the sensitive diaphragm to deform, and the temperature affects the sensitive diaphragm to cause the sensitive diaphragm to expand or contract; Measuring the cavity length of the optical fiber Fabry-Perot cavity for measuring pressure, and obtaining the pressure difference between the optical fiber Fabry-Perot cavity for measuring pressure and the environment according to the corresponding relationship between the cavity length of the optical fiber Fabry-Perot cavity for measuring pressure and the pressure; The cavity length of the optical fiber Fabry-Perot cavity for measuring temperature is measured, and the temperature of the optical fiber Fabry-Perot cavity for measuring temperature is obtained through the corresponding relationship between the temperature and the cavity length of the optical fiber Fabry-Perot cavity for measuring temperature.

8. The inspection method according to claim 7, characterized in that: include: Connecting an external pressure pipeline to the first pressure-introducing hole of the upper base and the second pressure-introducing hole of the lower base respectively, so that the external pressure acts on the sensitive diaphragm through the first pressure-introducing hole and the second pressure-introducing hole to cause the sensitive diaphragm to deform; measuring the cavity lengths of the first fiber Fabry-Perot cavity and the second fiber Fabry-Perot cavity, and calculating the pressure difference between the first fiber Fabry-Perot cavity and the second fiber Fabry-Perot cavity through the corresponding relationship between the cavity lengths and pressures of the first fiber Fabry-Perot cavity and the second fiber Fabry-Perot cavity; Measuring the cavity length of the optical fiber Fabry-Perot cavity for measuring temperature, and obtaining the temperature of the optical fiber Fabry-Perot cavity for measuring temperature through the corresponding relationship between the temperature and the cavity length of the third optical fiber Fabry-Perot cavity; The corresponding relationship between the cavity length and pressure of the first fiber Fabry-Perot cavity and the second fiber Fabry-Perot cavity is: , , ； in, represents the change in the cavity length of the first optical fiber Fabry-Perot cavity, represents the change in the cavity length of the second optical fiber Fabry-Perot cavity, represents the Poisson's ratio of the sensitive diaphragm, E represents the Young's modulus of the sensitive diaphragm, H Indicates the thickness of the sensitive membrane, R 1 represents the radius of the first optical fiber Fabry-Perot cavity, R 2 represents the radius of the second optical fiber Fabry-Perot cavity, P 1 represents the pressure of the first optical fiber Fabry-Perot cavity, P 2 represents the pressure of the second optical fiber Fabry-Perot cavity, Indicates differential pressure; The corresponding relationship between the temperature and the cavity length of the third optical fiber Fabry-Perot cavity is: ； in, L represents the change in the cavity length of the third optical fiber Fabry-Perot cavity, H Indicates the thickness of the sensitive membrane, Indicates temperature change, α It represents the thermal expansion coefficient of the sensitive membrane.

9. A spectral demodulation method of pressure difference and temperature based on the dual parameter sensing system according to any one of claims 3 to 6, characterized in that: include: The inner surface of the upper base, the upper surface and the lower surface of the sensitive membrane, and the inner surface and the outer surface of the lower base all constitute the reflection surface of the optical fiber Fabry-Perot sensor; the inner surface of the upper base and the upper surface of the sensitive membrane form a first optical fiber Fabry-Perot sensor; the inner surface of the lower base and the lower surface of the sensitive membrane form a second optical fiber Fabry-Perot sensor; the upper surface of the sensitive membrane and the lower surface of the sensitive membrane form a third optical fiber Fabry-Perot sensor; The optical reflection signals of the inner surface of the upper base, the upper surface and the lower surface of the sensitive diaphragm, and the inner surface of the lower base are interfered to generate a multi-cavity coupling spectrum, and the cavity lengths of the first fiber Fabry-Perot sensor, the second fiber Fabry-Perot sensor, and the third fiber Fabry-Perot sensor are obtained by Fourier transforming the coupling spectrum, and the pressure difference between the first fiber Fabry-Perot sensor and the second fiber Fabry-Perot sensor is calculated based on the corresponding relationship between the cavity lengths of the first fiber Fabry-Perot cavity and the second fiber Fabry-Perot cavity and the pressure; And the ambient temperature of the third optical fiber Fabry-Perot sensor is obtained through the corresponding relationship between the temperature and the cavity length of the third optical fiber Fabry-Perot cavity.

10. The spectrum demodulation method according to claim 9, characterized in that: The formula for the Fourier transform is as follows: ,in, F (j ) represents the Fourier transform of the interference spectrum, R FP (v) represents the interference spectrum of the sensor in the optical frequency domain, j represents the imaginary unit, e is the base of the exponential function, and the value of e is approximately 2.71828. represents the angular frequency, v represents the ratio of the speed of light to the wavelength, that is, the optical frequency; according to the angular frequency corresponding to the peak position Get the corresponding cavity length : Where c is the speed of light and n is the refractive index.

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