CN117367512B - A method for measuring the sensitivity of a temperature and pressure optical fiber sensor - Google Patents

Abstract

The invention discloses a novel temperature and pressure optical fiber sensor based on MZ interference and F-P interference, a preparation method thereof and a sensitivity measurement method thereof, belonging to the technical field of optical fiber sensors, and comprising: an MZ interference structure and an F-P interference structure connected to each other, the MZ interference structure being used to measure temperature, and the F-P interference structure being used to measure pressure; the MZ interference structure comprising a tapered peanut hybrid optical fiber structure, the tapered peanut hybrid optical fiber structure comprising a peanut optical fiber structure and a tapered optical fiber structure fused together; the F-P interference structure comprising a fiber Bragg grating structure, the fiber Bragg grating structure being fused to an empty end of the peanut optical fiber structure in the tapered peanut hybrid optical fiber structure, the temperature and pressure measurements of the sensor do not interfere with each other, and creatively realizes high-precision measurement of temperature and pressure at the same time.

Description

A method for measuring the sensitivity of a temperature and pressure optical fiber sensor

Technical Field

The present invention relates to a sensitivity measurement method of a temperature and pressure optical fiber sensor, and in particular to a temperature and pressure optical fiber sensor based on MZ interference and F-P interference, a preparation method thereof, and a sensitivity measurement method thereof, and belongs to the technical field of optical fiber sensors.

Background technique

Optical fiber technology has gained more and more attention in the past few decades due to its unique working mechanism and wide application. They reduce transmission loss and are not affected by electromagnetic interference, which makes them more widely applicable. Optical fiber is now widely used in the field of sensing due to its lightness, sensitivity, resistance to strong electromagnetic interference, high temperature resistance, and low signal attenuation. Optical fiber is used for sensing, can be networked, and is easy to realize intelligence. It integrates information transmission and sensing, and can effectively solve measurement problems that conventional detection technology is difficult to fully handle.

The basic principle of the fiber optic sensing system is that the light wave parameters in the optical fiber, such as light intensity, frequency, wavelength, phase and polarization state, change with the external measured parameters. The purpose of detecting the external measured physical quantity is achieved by detecting the changes in the light wave parameters in the optical fiber.

Temperature and pressure are two very important physical parameters for materials. They are widely used in material health monitoring, medical testing, industrial production, and the normal operation of large-scale flight devices. There are more and more studies on temperature and pressure sensors. Traditional sensors only measure a single parameter. However, the actual environment is not like a laboratory where the change of a single parameter can be controlled. In order to adapt to the complex parameter changes in the real environment, the development of sensors that measure temperature and pressure at the same time is particularly important.

Summary of the invention

The present invention provides a temperature and pressure optical fiber sensor based on MZ interference and F-P interference, a preparation method thereof and a sensitivity measurement method thereof. A hybrid structure combining MZ interference and F-P interference is formed by combining a tapered structure, a peanut structure and an optical fiber Bragg grating. The temperature and pressure applied by the outside are changed by utilizing the principle that the tapered and peanut structures are sensitive to temperature and the Bragg grating is highly sensitive to external pressure, thereby causing the displacement of interference spectrum lines, which are used to measure temperature and pressure respectively. The hybrid structure interferometer obtained by this method creatively realizes high-precision measurement of temperature and pressure at the same time.

To achieve the above object, the present invention is implemented by adopting the following technical solutions.

In a first aspect, the present invention provides a temperature and pressure optical fiber sensor based on MZ interference and F-P interference, comprising: an MZ interference structure and an F-P interference structure connected to each other, wherein the MZ interference structure is used to measure temperature, and the F-P interference structure is used to measure pressure;

The MZ interference structure includes a tapered peanut hybrid fiber structure, and the tapered peanut hybrid fiber structure includes a peanut fiber structure and a tapered fiber structure fused together;

The F-P interference structure includes a fiber Bragg grating structure, and the fiber Bragg grating structure is fused to the empty end of the peanut fiber structure in the tapered peanut hybrid fiber structure.

Optionally, the tapered fiber structure includes a section of single-mode fiber whose middle end is fused into a double cone, and the peanut fiber structure includes two sections of single-mode fiber with a microsphere structure at a single end, and the microsphere structures of the two sections of single-mode fiber are fused together.

Optionally, the fiber Bragg grating structure includes a section of grating optical fiber with laser interference fringes written in the fiber core, and the laser interference fringes are used to generate a periodic change of the refractive index along the axial direction of the fiber core.

Optionally, the Bragg equation of the FP interference structure is: λ _B =2n _eff Λ, wherein λ _B is the central wavelength, λ _B =1550 nm, n _eff represents the refractive index of the core mode, and Λ represents the grating period;

The calculation formulas for the interference intensity I and phase difference φ ^m of the MZ interference structure are:

Where, _I1 and _I2 are the light intensities of the core mode and cladding mode in the MZ interference structure, respectively, ^φm is the phase difference between the core mode and the cladding mode, is the effective refractive index RI difference between the core mode and the mth cladding mode, G is the interference length of the MZ interference structure, and λ is the input wavelength;

The calculation formula of the free spectral range FSR of the MZ interference structure is:

When the phase difference ^φm is equal to (2m+1)π, m=1, 2, 3…, the transmittance reaches a valley value at this wavelength, and the calculation formula for the central wavelength _λm of the mth order interference wave valley is:

In a second aspect, the present invention provides a method for preparing a temperature and pressure optical fiber sensor based on MZ interference and F-P interference, comprising:

Prepare tapered fiber structure, peanut fiber structure and fiber Bragg grating respectively;

The single-mode optical fiber SMF part of the tapered optical fiber structure and the single-mode optical fiber SMF part of the peanut optical fiber structure are fused together to obtain the MZ interference structure;

The SMF part of the peanut fiber structure at the empty end of the MZ interference structure is fused with the SMF part of the fiber Bragg grating to obtain the sensor.

Optionally, the preparation of the tapered optical fiber structure includes: placing a section of SMF with coating removed into a fusion splicer and discharging the SMF multiple times with an arc having a power of 80 bits and a discharge time of 2000 ms to obtain the tapered optical fiber structure.

Optionally, the preparation of the peanut optical fiber structure comprises:

A section of SMF is placed in a fusion splicer and an arc with a power of +80bit, a discharge time of 2000ms and a deviation of 25μm from the end face of the SMF is used to discharge the end face to form a microsphere cavity, thereby obtaining a single-mode optical fiber with a microsphere structure.

The peanut optical fiber structure is obtained by discharging and welding the microspheres of two sections of single-mode optical fibers with microsphere structures using an arc with a standard discharge power and a discharge time of 1000 ms.

Optionally, the preparing a fiber Bragg grating comprises:

A section of photosensitive optical fiber is placed close to a grating mask that can suppress zero-order diffraction and maximize first-order diffraction, and ultraviolet light is directly incident on the photosensitive optical fiber through the grating mask. Interference fringes generated by near-field diffraction of the phase grating mask are used to form a periodically disturbed refractive index in the optical fiber to obtain a fiber Bragg grating.

In a third aspect, the present invention provides a sensitivity measurement method of a temperature and pressure optical fiber sensor based on MZ interference and F-P interference, comprising:

A test environment for simultaneously measuring pressure and temperature through the sensor is established using a broadband light source BBS and an optical spectrum analyzer OSA;

Under the condition that the two variables of pressure and temperature are controlled simultaneously, the optical signal emitted by the broadband light source BBS is injected into the empty end of the F-P interference structure of the sensor, and the optical signal is transmitted through the F-P interference structure and the MZ interference structure to obtain a reflected light wave and a transmitted light wave;

Allowing the reflected light wave and the transmitted light wave to propagate into the optical spectrum analyzer OSA to obtain an F-P reflection spectrum and an MZ transmission spectrum;

The pressure sensitivity and temperature sensitivity of the sensor are obtained based on the changes of the F-P reflection spectrum characteristics and the MZ transmission spectrum characteristics with pressure and temperature.

Optionally, the changes of the F-P reflection spectrum characteristics and the MZ transmission spectrum characteristics with changes in pressure and temperature include:

When the temperature is constant, the relationship between the center wavelength drift Δλ _B of the reflected wave of the FP interference structure and the axial strain ε ₁ of the fiber Bragg grating is:

Δλ _B ＝λ _B (1-P _ε )ε ₁ ＝K _ε ε ₁ ,

Wherein, P _ε is the effective elastic-optic coefficient of the fiber Bragg grating, K _ε is the gauge coefficient pm/με of the fiber Bragg grating, K _ε =1.18pm/με, λ _B is the central wavelength, λ _B =1550nm;

When the pressure is constant, the relationship between the transmission wave valley displacement Δλ _m of the MZ interference structure and the applied temperature change ε ₂ is:

Where _λm is the central wavelength of the mth order interference trough, is the effective refractive index RI difference between the core mode and the mth cladding mode, T represents the temperature, ΔT represents the temperature change, ε ₂ is the rate of change of the effective refractive index RI difference between the core and the mth cladding mode with the temperature T, ε ₂ =dL ₂ /L ₂ , L ₂ represents the interaction length between the two tapered vertebrae.

Compared with the prior art, the present invention has the following beneficial effects: the present invention utilizes a method combining a Bragg grating structure, a taper structure and a peanut structure to produce a MZ and F-P interference hybrid structure, which can simultaneously achieve high-precision measurement of temperature and pressure; in the field of temperature measurement, the taper and peanut structures utilize the Mach-Zehnder interference principle and are often used to produce high-precision temperature sensors, and the sensitivity reaches an extremely high level; in the field of pressure measurement, the fiber Bragg grating forms an F-P interference structure, which is used to produce high-precision pressure sensors, and the sensitivity reaches an extremely high level The fiber taper structure can be obtained by discharging a single-mode optical fiber using a commercial fusion splicer, so it is simple and easy to manufacture; the peanut structure is formed by making spherical structures on two single-mode optical fibers, and fusing the spheres together, which is simple and easy to manufacture; the fiber Bragg grating structure can be manufactured by a phase mask method, where the photosensitive optical fiber is placed close to the phase grating mask, and the interference fringes generated by the near-field diffraction of the phase grating mask are used to form a periodically disturbed refractive index in the optical fiber, thereby forming a fiber grating, and the manufacturing process is also very simple; the combination of the three can be achieved by fusing single-mode optical fibers, which is very simple and conducive to production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram showing the preparation of a tapered structure in one embodiment of the present invention;

FIG2 is a schematic diagram of a taper structure in an embodiment of the present invention;

FIG3 is a schematic diagram showing the preparation of a single-mode optical fiber with a microsphere structure in an embodiment of the present invention;

FIG4 is a schematic diagram showing the structure of a single-mode optical fiber with a microsphere structure in one embodiment of the present invention;

FIG5 is a schematic diagram showing the preparation of a peanut structure in one embodiment of the present invention;

FIG6 is a schematic diagram of the structure of peanuts in one embodiment of the present invention;

FIG7 is a schematic diagram showing the preparation of an MZ interference structure in an embodiment of the present invention;

FIG8 is a schematic diagram of an MZ interference structure in an embodiment of the present invention;

FIG9 is a schematic diagram showing the preparation of a fiber Bragg grating in an embodiment of the present invention;

FIG10 is a schematic diagram of a fiber Bragg grating structure in an embodiment of the present invention;

FIG11 is a schematic diagram showing the preparation of a hybrid interference structure in an embodiment of the present invention;

FIG12 is a schematic diagram of a hybrid interference structure in an embodiment of the present invention;

FIG13 is a schematic diagram showing a light propagation mode in a hybrid interference structure in an embodiment of the present invention;

FIG14 is a schematic diagram showing an environment for measuring temperature sensitivity in an embodiment of the present invention;

FIG. 15 is a schematic diagram showing an environment for measuring pressure sensitivity in an embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

Example 1

The present embodiment provides a temperature and pressure optical fiber sensor based on MZ interference and F-P interference, comprising: an MZ interference structure and an F-P interference structure connected to each other, the MZ interference structure is used to measure temperature, and the F-P interference structure is used to measure pressure; the MZ interference structure comprises a tapered peanut hybrid optical fiber structure, the tapered peanut hybrid optical fiber structure comprises a peanut optical fiber structure and a tapered optical fiber structure fused together; the F-P interference structure comprises a fiber Bragg grating structure, the fiber Bragg grating structure is fused to the empty end of the peanut optical fiber structure in the tapered peanut hybrid optical fiber structure, as shown in FIG12 , the left end is a fiber Bragg grating structure, the middle is a peanut structure, and the right end is a tapered structure, forming an MZ/F-P hybrid interference.

By utilizing the temperature sensitivity of the cone and peanut structures, the temperature can be measured by causing the displacement of the interference spectrum. When the laser passes through the Bragg grating, it will be reflected, and the reflected light will cause F-P interference with the incident light. When external pressure is applied, the wavelength of the reflected light from the grating will change slightly, which will have a certain impact on the relevant characteristics of the interference. The Bragg grating is highly sensitive to external pressure, so the pressure can be measured according to this principle. By combining the Bragg grating structure, the cone structure and the peanut structure to form a hybrid interference structure, high-precision measurement of temperature and pressure is creatively achieved at the same time.

Example 2

Based on Example 1, this example also makes the following design.

As shown in FIG13 , when light passes through the fiber Bragg grating from left to right, the two coherent light beams reflected by the grating will interfere with each other. At the same time, the two coherent light beams will be energy coupled to form a reflected light wave of a specific wavelength. The Bragg equation of the FP interference structure obtained by the wavelength matching condition δβ＝0 is: λ _B ＝2n _eff Λ, where λ _B is the center wavelength, λ _B ＝1550nm, and n _eff represents the refractive index of the core mode. δ is the phase difference between the forward propagating LP mode and the backward propagating LP mode, β is the mode propagation constant,/> Λ is a constant, representing the grid period.

The transmitted light of the grating continues to propagate, and the first excitation occurs at the peanut structure. Part of the core mode light is excited to the cladding mode, and the remaining light continues to propagate along the core. Then the cladding mode and core mode light are coupled at the tapered structure to form MZ interference. When it is propagated to the optical spectrum analyzer OSA, an MZ transmission spectrum and an F-P reflection spectrum can be obtained. The arc arrow in Figure 13 represents the working condition of the F-P mode, and the straight arrow represents the working condition of the MZ mode. The temperature is measured by the transmission spectrum, and the formulas for the relevant parameters of the transmission spectrum are as follows.

The calculation formulas for the interference intensity I and phase difference φ ^m of the MZ interference structure are:

Where, _I1 and _I2 are the light intensities of the core mode and cladding mode in the MZ interference structure, respectively, ^φm is the phase difference between the core mode and the cladding mode, is the effective refractive index RI difference between the core mode and the mth cladding mode, G is the interference length of the MZ interference structure, and λ is the input wavelength.

The calculation formula of the free spectral range FSR of the MZ interference structure is:

FSR increases with the decrease of interference length G. When the phase difference ^φm is equal to (2m+1)π, m=1, 2, 3…, the transmittance reaches the valley value at this wavelength. The calculation formula of the central wavelength _λm of the mth order interference valley is:

Example 3

This embodiment provides a method for preparing a temperature and pressure optical fiber sensor based on MZ interference and F-P interference, comprising the following steps.

The preparation materials require single-mode optical fiber (SMF-28, Corning) and multi-mode optical fiber (MMF, this article uses nineteen-core four-mode), and the equipment required includes optical fiber fusion splicer (80S, Fujikura), spectrum analyzer (AQ6370D, Yokogawa, Optical Spectrum Analyzer, OSA), broadband light source (Benchtop Broadband Source, BBS), optical fiber cutting knife (CKFC-1, CommKing), micro-displacement platform, optical fiber clamp, and microscope.

1. Production of taper structure

As shown in Figures 1 and 2, in the optical fiber, the tapered structure can effectively excite the light in the core into the cladding. As shown in Figure 1, the manufacturing process of the structure is as follows: the first step is to fix a section of SMF with the coating removed in the optical fiber fusion splicer; the second step is to discharge the SMF with the coating removed multiple times with an arc power of 80 bits and an arc discharge time of 2000ms to form a tapered structure in order to ensure that the middle end of the SMF is melted to form the expected taper.

2. Production of Peanut Structure

As shown in Figure 3 and Figure 4, first, a section of single-mode optical fiber is placed in the optical fiber fusion splicer. The arc with an arc power of +80bit and a discharge time of 2000ms is used to discharge the end face of the single-mode optical fiber to form a microsphere cavity. To ensure that the end face of the optical fiber is melted into a silicon microsphere, the arc deviates from the end face of the optical fiber by 25μm. Since the discharge position is located at the center of the display screen of the fusion splicer, the end face of the optical fiber can be accurately adjusted to the position of the electrode in manual mode. Use a ruler to measure the diameter of the enlarged optical fiber, and use a proportional relationship to measure it to be 25μm. During the discharge process, the optical fiber is placed vertically (the fusion splicer is placed vertically) to ensure that the center of the microsphere is located on the axis of the optical fiber. As shown in Figure 3.

As shown in Figures 5 and 6, the above steps are repeated twice to obtain two sections of single-mode optical fiber with microsphere structures, which are then fused in pairs. When two microspheres are fused, a discharge time of 1000ms and a standard discharge power are used, as shown in Figure 4, to obtain a peanut structure.

3. Fabrication of MZ interferometer structure

After the peanut structure is made, the SMF part of the taper structure and the SMF part of the peanut structure are directly fused together using a fiber fusion splicer, and discharge is performed to complete the fusion, as shown in FIG7 , thereby forming a complete MZ interference structure, as shown in FIG8 .

4. Fabrication of Fiber Bragg Grating Structure

At present, the main method for making Bragg gratings is the phase mask method, that is, using the interference fringes generated by the near-field diffraction of the phase grating mask to form a periodically disturbed refractive index in the optical fiber. The key component of this production method is the phase mask template, which is a phase diffraction element precisely etched under computer control. As shown in Figure 9, the zero-order fringes of the normally incident ultraviolet light are suppressed (3%) after diffraction by the mask template, and the ±1-order fringes reach the maximum (35%) respectively, and the interacting incoming interference fringes expose the doped optical fiber core immediately behind them, forming a FBG with a phase grating period of 1/2 of the phase template period, forming an F-P interference structure, as shown in Figure 10. If the phase template and the optical fiber are placed at a certain angle, FBGs with different periods and Bragg wavelengths can be made.

5. Fabrication of hybrid interference structure

As shown in FIG. 11 and FIG. 12 , after the fiber Bragg grating is manufactured, the SMF part of the fiber Bragg grating and the SMF part of the peanut structure are automatically fused together using a fiber fusion splicer in the same manner as before, and discharge is performed to complete the fusion.

Example 4

This embodiment provides a sensitivity measurement method of a temperature-pressure optical fiber sensor based on MZ interference and F-P interference, which includes the measurement of temperature sensitivity and the measurement of pressure sensitivity respectively.

The device for measuring temperature is shown in Figure 14 below. Light is emitted from a light source BBS and enters an adjustable temperature box in which a prepared hybrid interference structure is placed. The temperature in the box ranges from 20°C to 100°C. The transmission spectrum in the optical spectrum analyzer OSA is measured every 10°C for about 10 minutes to obtain the temperature sensitivity of the hybrid interference structure.

When the pressure is constant and the temperature changes are applied to the Mach-Zehnder sensing part, the modal index and the fiber length will change, resulting in the displacement of the spectral trough. The relationship between the displacement of the transmission wave trough Δλ _m of the MZ interference structure and the applied temperature change rate ε ₂ is:

Where _λm is the central wavelength of the mth order interference trough, is the effective refractive index RI difference between the core mode and the mth cladding mode, T represents the temperature, ΔT represents the temperature change, ε ₂ is the rate of change of the effective refractive index RI difference between the core and the mth cladding mode with the temperature T, ε ₂ =dL ₂ /L ₂ , L ₂ represents the interaction length between the two tapered vertebrae.

As shown in Figure 15, which is a schematic diagram of measuring pressure, the prepared hybrid interference structure is pressed between two glass slides, and a single-mode optical fiber is placed parallel to the sensor as a reference to ensure that the sensor is evenly stressed. Light is emitted from the light source BBS, passes through the circulator, and one end is connected to the hybrid interference structure and the other end is connected to the spectrum analyzer OSA. Weights are added to the glass slide in steps of 50g, increasing from 0g to 1000g, and the movement of the spectrum lines on the spectrum analyzer is recorded to obtain the pressure sensitivity of the hybrid interference structure.

When the temperature is constant and only the axial strain ε of the grating is considered, the relationship between the drift Δλ _B of the reflected wave center wavelength of the FP interference structure and the axial strain ε ₁ of the fiber Bragg grating is:

Δλ _B ＝λ _B (1-P _ε )ε ₁ ＝K _ε ε ₁ ,

Wherein, P _ε is the effective elastic-optic coefficient of the fiber Bragg grating, K _ε is the gauge coefficient pm/με of the fiber Bragg grating, K _ε =1.18 pm/με, λ _B is the central wavelength, λ _B =1550 nm.

The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims (8)

1. A method for measuring the sensitivity of a temperature and pressure optical fiber sensor, characterized in that: The sensor comprises an MZ interference structure and an F-P interference structure connected to each other, wherein the MZ interference structure is used to measure temperature, and the F-P interference structure is used to measure pressure; The sensitivity measurement method comprises the following steps: A test environment for simultaneously measuring pressure and temperature through the sensor is established using a broadband light source BBS and an optical spectrum analyzer OSA; Under the condition that the two variables of pressure and temperature are controlled simultaneously, the optical signal emitted by the broadband light source BBS is injected into the empty end of the F-P interference structure of the sensor, and the optical signal is transmitted through the F-P interference structure and the MZ interference structure to obtain a reflected light wave and a transmitted light wave; Allowing the reflected light wave and the transmitted light wave to propagate into the optical spectrum analyzer OSA to obtain an F-P reflection spectrum and an MZ transmission spectrum; Obtaining the pressure sensitivity and temperature sensitivity of the sensor based on the changes of the F-P reflection spectrum characteristics and the MZ transmission spectrum characteristics with changes in pressure and temperature; The changes of the F-P reflection spectrum characteristics and the MZ transmission spectrum characteristics with changes in pressure and temperature include: When the temperature is constant, the relationship between the center wavelength drift Δλ _B of the reflected wave of the FP interference structure and the axial strain ε ₁ of the fiber Bragg grating is: Δλ _B ＝λ _B (1-P _ε )ε ₁ ＝K _ε ε ₁ , Wherein, P _ε is the effective elastic-optic coefficient of the fiber Bragg grating, K _ε is the gauge coefficient pm/με of the fiber Bragg grating, K _ε =1.18pm/με, λ _B is the central wavelength, λ _B =1550nm; When the pressure is constant, the relationship between the transmission wave valley displacement Δλ _m of the MZ interference structure and the applied temperature change rate ε ₂ is: Where _λm is the central wavelength of the mth order interference trough, is the effective refractive index RI difference between the core mode and the mth cladding mode, T represents the temperature, ΔT represents the temperature change, ε ₂ is the rate of change of the effective refractive index RI difference between the core and the mth cladding mode with the temperature T, ε ₂ =dL ₂ /L ₂ , L ₂ represents the interaction length between the two lumbar vertebrae of the tapered structure; Wherein, the MZ interference structure includes a tapered peanut hybrid fiber structure, and the tapered peanut hybrid fiber structure includes a peanut fiber structure and a tapered fiber structure fused together; The F-P interference structure includes a fiber Bragg grating structure, and the fiber Bragg grating structure is fused to the empty end of the peanut fiber structure in the tapered peanut hybrid fiber structure. 2. The sensitivity measurement method of the temperature and pressure optical fiber sensor according to claim 1 is characterized in that the tapered optical fiber structure includes a section of single-mode optical fiber with the middle end fused into a double cone, and the peanut optical fiber structure includes two sections of single-mode optical fiber with a microball structure at a single end, and the microball structures of the two sections of single-mode optical fiber are fused together. 3. The sensitivity measurement method of the temperature and pressure optical fiber sensor according to claim 1 is characterized in that the optical fiber Bragg grating structure includes a section of grating optical fiber with laser interference fringes written in the core, and the laser interference fringes are used to produce periodic changes in the refractive index along the axial direction of the core in the core. 4. The sensitivity measurement method of the temperature and pressure optical fiber sensor according to claim 1, characterized in that the Bragg equation of the FP interference structure is: λ _B =2n _eff Λ, wherein λ _B is the center wavelength, λ _B =1550nm, n _eff represents the refractive index of the core mode, and Λ represents the grid period; The calculation formulas for the interference intensity I and phase difference φ ^m of the MZ interference structure are: Where, _I1 and _I2 are the light intensities of the core mode and cladding mode in the MZ interference structure, respectively, ^φm is the phase difference between the core mode and the cladding mode, is the effective refractive index RI difference between the core mode and the mth cladding mode, G is the interference length of the MZ interference structure, and λ is the input wavelength; The calculation formula of the free spectral range FSR of the MZ interference structure is: When the phase difference ^φm is equal to (2m+1)π, m=1, 2, 3…, the transmittance reaches a valley value at this wavelength, and the calculation formula for the central wavelength _λm of the mth order interference wave valley is: 5. The sensitivity measurement method of the temperature and pressure optical fiber sensor according to any one of claims 1 to 4, characterized in that the preparation method of the sensor comprises: Prepare tapered fiber structure, peanut fiber structure and fiber Bragg grating respectively; The single-mode optical fiber SMF part of the tapered optical fiber structure and the single-mode optical fiber SMF part of the peanut optical fiber structure are fused together to obtain the MZ interference structure; The SMF part of the peanut fiber structure at the empty end of the MZ interference structure is fused with the SMF part of the fiber Bragg grating to obtain the sensor. 6. The sensitivity measurement method of the temperature and pressure optical fiber sensor according to claim 5 is characterized in that the preparation of the tapered optical fiber structure includes: placing a section of SMF with the coating removed into a fusion splicer and discharging the SMF multiple times with an arc with a power of 80 bits and a discharge time of 2000 ms to obtain the tapered optical fiber structure. 7. The sensitivity measurement method of the temperature and pressure optical fiber sensor according to claim 5, characterized in that the preparation of the peanut optical fiber structure comprises: A section of SMF is placed in a fusion splicer and an arc with a power of +80bit, a discharge time of 2000ms and a deviation of 25μm from the end face of the SMF is used to discharge the end face to form a microsphere cavity, thereby obtaining a single-mode optical fiber with a microsphere structure. The peanut optical fiber structure is obtained by discharging and welding the microspheres of two sections of single-mode optical fibers with microsphere structures using an arc with a standard discharge power and a discharge time of 1000 ms. 8. The sensitivity measurement method of the temperature and pressure optical fiber sensor according to claim 5, characterized in that the preparation of the optical fiber Bragg grating comprises: A section of photosensitive optical fiber is placed close to a grating mask that can suppress zero-order diffraction and maximize first-order diffraction, and ultraviolet light is directly incident on the photosensitive optical fiber through the grating mask. Interference fringes generated by near-field diffraction of the phase grating mask are used to form a periodically disturbed refractive index in the optical fiber to obtain a fiber Bragg grating.