Mixed structure sensor, preparation method thereof and sensitivity measurement method

Abstract

The invention discloses a mixed structure sensor, a preparation method thereof and a sensitivity measurement method in the field of optical fiber sensors. The optical fiber sensor comprises a Bragg grating and a double-peanut structure which are cascaded with each other, when a light beam transmitted in an optical fiber passes through the Bragg grating, whether the light beam meets a Bragg condition is judged, if the light beam meets the Bragg condition, the light beam is reflected, and the reflected light beam is used for monitoring temperature change; if the Bragg condition is not met, the light beam enters a double-peanut structure, and when the light beam passes through the first double-peanut structure, a part of the light beam is transferred to a cladding mode from a core mode of the optical fiber; and when the light beam passes through the second double-peanut structure, the light beam transferred to the cladding mode is coupled back into the core mode again, and the light beam which is coupled back into the core mode again and the original light beam in the core mode form Mach-Zehnder interference for monitoring the strain state of the optical fiber. The temperature change and the strain condition can be monitored at the same time, and the manufacturing process is simple.

Description

Technical Field

[0001] The invention relates to a hybrid structure sensor and a preparation method thereof and a sensitivity measurement method, belonging to the technical field of optical fiber sensors. Background Art

[0002] With the continuous development of science and technology, the demand for sensing technology is increasing in various fields, especially in scenarios that require multi-point and multi-parameter monitoring at the same time. Therefore, the research and development of sensors that can detect multiple parameters at the same time has become a key trend in the development of sensing technology. Compared with traditional electromagnetic sensors, fiber optic sensors have shown obvious advantages, such as small size, light weight, corrosion resistance, strong anti-electromagnetic interference ability, and easy reuse. These characteristics make fiber optic sensors widely used in various measurement fields such as temperature, humidity, strain, lateral pressure, pressure, etc., providing efficient and reliable monitoring solutions for many industries.

[0003] In the field of fiber optic sensor research, interferometric fiber optic sensors have attracted widespread attention due to their small size, high sensitivity, fast response speed and wide dynamic range. In order to realize the function of an inline interferometer within a single optical fiber, a special structural design is usually required. These designs use different waveguide structures to generate a specific phase difference between two light signals, thereby producing a stable interference spectrum. There are many ways to achieve this goal, including the use of cascaded long-period fiber gratings, core bias structures, connection of single-mode and multimode fibers, tapered structures, and specially designed optical fibers.

[0004] In addition, the research on fiber Bragg grating sensors is also deepening, especially Bragg gratings, which have been widely used in the manufacture of optical fiber filters, lasers, sensors and other equipment due to their simple manufacturing process, low cost and ability to accurately control specific wavelengths. Bragg gratings form grating structures by introducing periodic refractive index changes. When the wavelength of the incident light wave meets the Bragg condition, Bragg scattering occurs, which can selectively enhance or suppress light signals of specific wavelengths. Using this principle, a variety of new wavelength division multiplexing fiber Bragg grating temperature sensing systems and temperature-resistant fiber Bragg grating sensing systems based on wavelength demodulation have been developed. These systems have shown excellent performance in monitoring temperature changes. Summary of the invention

[0005] The purpose of the present invention is to provide a hybrid structure sensor and a preparation method thereof and a sensitivity measurement method, which can simultaneously monitor temperature and optical fiber strain, and the entire hybrid structure is simple and compact, which is conducive to making a miniature high-precision sensor.

[0006] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions.

[0007] On the one hand, the present invention provides a hybrid structure sensor, including a cascaded Bragg grating and a double peanut structure. When a light beam transmitted in an optical fiber passes through the Bragg grating, it is determined whether the light beam meets the Bragg condition. If the Bragg condition is met, the light beam is reflected in the light, and the reflected light beam is used to monitor the change of temperature; if the Bragg condition is not met, the light beam enters the double peanut structure; The double peanut structure includes a first peanut structure and a second peanut structure; when passing through the first peanut structure, a part of the light beam is transferred from the core mode of the optical fiber to the cladding mode; when passing through the second peanut structure, the light beam transferred to the cladding mode is coupled back to the core mode again, and the light beam coupled back to the core mode forms Mach-Zehnder interference with the original light beam in the core mode, which is used to monitor the strain state of the optical fiber.

[0008] In combination with the first aspect, further, the expression satisfying the Bragg condition is: ; in, represents the central wavelength of the Bragg grating; Represents the effective refractive index of the fiber core; represents the period of the fiber Bragg grating.

[0009] In combination with the first aspect, further, the light beam is reflected in the optical fiber, and the reflected light beam is used to monitor the change of temperature, including: Using a spectrometer to record the wavelength and intensity of the reflected light beam to form a reflection spectrum; By measuring the reflection spectrum, the temperature change experienced by the Bragg grating is determined.

[0010] In combination with the first aspect, further, the light beam coupled back into the fiber core again forms interference with the original light beam in the core mode to monitor the strain state of the optical fiber, including: When the light beam coupled back from the cladding mode meets the original light beam in the core mode in space, a phase difference is generated, and an interference spectrum is formed according to the phase difference, and a spectrometer is used to capture the position of a characteristic wavelength in the interference spectrum and measure the interference light intensity related to the characteristic wavelength; When the hybrid structure interference sensor is subjected to external strain, the refractive indexes of the core mode and the cladding mode change accordingly, thereby changing the phase difference between the light beam coupled back from the cladding mode and the original light beam in the core mode; According to the change of the phase difference, the characteristic wavelength in the interference spectrum moves and the corresponding interference light intensity distribution changes. By measuring the movement of the characteristic wavelength and the change of the interference light intensity, the strain of the optical fiber is obtained.

[0011] In combination with the first aspect, further, the interference light intensity associated with the characteristic wavelength is measured, and the expression of the interference light intensity is: ; in, Indicates the light intensity of the core mode; represents the light intensity of the cladding mode; Indicates the operating wavelength; represents the refractive index difference between the effective refractive index of the cladding mode and the effective refractive index of the core mode; L represents the distance between the two peanut-shaped structures; represents the interference light intensity; The relationship between the shift of the characteristic wavelength and the change of strain is: ; in, represents the applied stress change; It represents the difference between the effective refractive index of the core mode and the cladding mode; n represents the nth-order interference trough.

[0012] In a second aspect, a method for preparing a hybrid structure sensor is characterized by comprising: Prepare Bragg grating and double peanut structure respectively; The single-mode optical fiber portion of the first peanut structure is fused with the single-mode optical fiber portion of the second peanut structure to form a Mach-Zehnder structure; The single-mode optical fiber part of the Mach-Zehnder structure is fused with the left single-mode optical fiber end of the Bragg grating to obtain the hybrid structure interference sensor.

[0013] In combination with the second aspect, further, the preparing of the Bragg grating includes: Prepare femtosecond laser, phase mask and single-mode quartz optical fiber in advance; The light beam generated by the femtosecond laser is irradiated onto the phase mask to form periodic interference fringes, thereby generating a refractive index change on the core mode of the single-mode quartz optical fiber, and a Bragg grating is written according to the refractive index change.

[0014] In combination with the second aspect, further, the preparation of the double peanut structure comprises: Using an optical fiber fusion splicer, discharge the single-mode optical fiber portion of the first peanut structure and the single-mode optical fiber portion of the second peanut structure multiple times to form ellipsoidal shapes respectively; Manual discharge fusion splicing of two ellipsoidal single-mode optical fibers to form peanut-shaped structures; The two single-mode optical fiber sections of the peanut-shaped structure are fused again to form a series-connected double peanut structure.

[0015] In combination with the second aspect, further, the forming of the ellipsoidal shape satisfies the following conditions: Discharge time length of optical fiber fusion splicer: 2000ms±200ms; Discharge intensity of optical fiber fusion splicer: +60bit±5bit; Extension length beyond SMF: 50 -70 ; The formation of the peanut-like structure satisfies the following conditions: Discharge time length of optical fiber fusion splicer: 2000ms±200ms; Discharge intensity of optical fiber fusion splicer: +40bit±10bit; Fiber overlap: 40 -60 .

[0016] In a third aspect, a sensitivity measurement method of a hybrid structure sensor includes: Use the pre-built broadband light source and spectrum analyzer to build a test environment for measuring temperature and strain simultaneously through the sensor to be tested; The sensor to be tested is placed in a preset electric furnace and between two glass slides for testing. The response of the sensor to be tested to temperature and strain is determined by adjusting the temperature of the electric furnace and placing weights on the glass slides.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention combines the advantages of Bragg grating and double peanut structure, realizes the synchronous high-precision monitoring of temperature and optical fiber strain, and screens the incident light beam through the Bragg grating. Only the light beam of a specific wavelength that meets the Bragg condition will be reflected. This feature enables the sensor to accurately capture the signal of temperature change. The change of the reflected light beam is directly related to the temperature fluctuation, providing an effective means of temperature monitoring.

[0018] For beams that do not meet the Bragg condition, they enter the double peanut structure, and the two peanut-shaped structures are used to realize the transfer and re-coupling of the beams between the core mode and the cladding mode. When the beam passes through the first peanut structure, part of the beam is transferred to the cladding mode, and this process is very sensitive to the strain of the optical fiber. Subsequently, when these beams pass through the second peanut structure, they are coupled back to the core mode again, interfering with the original beams in the core mode to form a Mach-Zehnder interference pattern. This interference effect is extremely sensitive to small strain changes in the optical fiber, so that the strain state of the optical fiber can be accurately monitored. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. 1 is a schematic diagram of a hybrid structure interference sensor provided by an embodiment of the present invention; Figure 2 FIG. 1 is a schematic diagram of a femtosecond laser for preparing a Bragg grating provided by an embodiment of the present invention; Figure 3 It is a schematic diagram of the first welding of the double peanut structure provided by the embodiment of the present invention; Figure 4 It is a schematic diagram showing the current state of an ellipsoid formed after the first welding provided by an embodiment of the present invention; Figure 5 It is a schematic diagram showing the current state of double peanuts formed after the second welding provided by an embodiment of the present invention; Figure 6 Shown is a schematic diagram of a temperature measurement experimental device provided in an embodiment of the present invention; Figure 7 FIG. 1 is a schematic diagram of a strain measurement experimental device provided by an embodiment of the present invention; In the figure: 1. Bragg grating; 2. double peanut structure; 3. first peanut structure; 4. second peanut structure; 6. broadband light source; 7. spectrum analyzer; 8. electric furnace; 9. glass slide; 10. sensor to be detected; 11. femtosecond laser; 12. phase mask; 13. single-mode quartz optical fiber. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. The embodiments of the present invention and the technical features in the embodiments may be combined with each other unless there is a conflict.

[0021] The term "and / or" is only a description of the association relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " generally indicates that the related objects are in an "or" relationship. Example 1

[0022] See also Figure 1 This embodiment introduces a hybrid structure sensor, including a cascaded Bragg grating 1 and a double peanut structure 2. When a light beam transmitted in an optical fiber passes through the Bragg grating 1, it is determined whether the light beam meets the Bragg condition. If the Bragg condition is met, a light beam of a predetermined wavelength will be reflected, and the reflected light beam is used to monitor temperature changes.

[0023] The light beam that does not meet the Bragg condition continues to propagate through the optical fiber, enters the double peanut structure 2, and generates interference due to the coupled mode, wherein the double peanut structure 2 includes a first peanut structure 3 and a second peanut structure 4; when passing through the first peanut structure 3, a part of the light beam is excited from the core mode (central part) of the optical fiber to the cladding mode (peripheral part); when passing through the second peanut structure 4, the light beam transferred to the cladding mode is coupled back to the core mode of the optical fiber again, so that the light beam coupled back to the core mode forms Mach-Zehnder interference with the original core mode light beam, which is used to monitor the strain of the optical fiber.

[0024] The present invention can simultaneously measure temperature changes and optical fiber strain conditions by combining a cascade design of a Bragg grating 1 and a double peanut structure 2. Since the Bragg grating 1 (FBG) part is sensitive to temperature changes and the double peanut structure 2 is sensitive to optical fiber strain, the hybrid structure interference sensor can detect these two parameters with high precision. Example 2

[0025] See also Figure 1 When a light beam enters the optical fiber and encounters a Bragg grating 1, the grating will operate the light beam according to the Bragg condition. When the wavelength of the incident light matches the structure of the grating, a light beam of a specific wavelength will be reflected, and a spectrometer is used to record the wavelength and intensity of the reflected light beam to form a reflection spectrum. Since temperature changes can affect the reflection wavelength of the grating, the temperature changes experienced by the Bragg grating can be determined by measuring the reflection spectrum, that is, the temperature changes are monitored by the reflected light beam.

[0026] Furthermore, the expression that satisfies the Bragg condition is: (1) in, represents the central wavelength of the Bragg grating; Represents the effective refractive index of the fiber core; represents the period of the fiber Bragg grating.

[0027] Since the wavelength of the reflected light beam of the Bragg grating 1 is sensitive to temperature changes, the increase in temperature causes thermal expansion and thermo-optical effect of the material, thereby changing the refractive index of the core mode and cladding mode of the optical fiber, and the central wavelength of the Bragg grating 1 is shifted by the following formula (2): (2) in, is the thermal expansion coefficient of the Bragg grating material; represents the thermo-optic coefficient of the Bragg grating material; Indicates changes in temperature; Indicates the shift in the central wavelength.

[0028] The remaining light beam continues to propagate through the optical fiber. When the light beam in the core reaches the double peanut structure 2, mode coupling occurs. When a part of the light passes through the first peanut-shaped structure 3, it is coupled from the core mode to the cladding mode. Due to the particularity of the peanut-shaped structure, the propagation path of the light beam is changed. The light beam coupled to the cladding mode continues to propagate forward along the cladding. When this part of the light reaches the second peanut-shaped structure 4, it is coupled back to the core mode again, and MZ interference is generated with the light beam in the original core mode. The interference process includes: Step S41, when the light beam coupled back from the cladding mode meets the original light beam in the core mode in space, a phase difference is generated, and an interference spectrum is formed according to the phase difference; Step S42: using a spectrometer to capture the position of the characteristic wavelength in the interference spectrum and measure the interference light intensity related to the characteristic wavelength. The intensity of the light after interference is: (3) in, Indicates the light intensity of the core mode; represents the light intensity of the cladding mode; Indicates the operating wavelength; represents the refractive index difference between the effective refractive index of the cladding mode and the effective refractive index of the core mode; L represents the distance between the two peanut-shaped structures; represents the interference light intensity;

[0029] It should be noted that, at that time, the interference light intensity is the minimum value, and the expression of the working wavelength is: (4) Step S43, when the hybrid structure interference sensor is subjected to external strain, the refractive indexes of the core mode and the cladding mode change accordingly, thereby changing the phase difference between the light beam coupled back from the cladding mode and the original light beam in the core mode; Step S44: According to the change of the phase difference, the characteristic wavelength in the interference spectrum moves and the corresponding interference light intensity distribution changes. By measuring the movement of the characteristic wavelength and the change of the interference light intensity, the strain of the optical fiber is obtained.

[0030] Specifically, when subjected to external pressure, the difference between the effective refractive index of the cladding mode and the effective refractive index of the core mode changes, which in turn causes the characteristic wavelength in the interference spectrum to redshift (move to a longer wavelength) or blueshift (move to a shorter wavelength). This wavelength shift is detected and observed on a spectrometer, thereby measuring and displaying the wavelength and intensity of the light beam.

[0031] Furthermore, the relationship between the shift of the characteristic wavelength and the magnitude of the external environmental strain is: (5) in, represents the applied stress change; It represents the difference between the effective refractive index of the core mode and the cladding mode; n represents the nth-order interference trough. Example 3

[0032] A method for preparing a hybrid structure sensor, comprising: Prepare a Bragg grating 1 and a double peanut structure 2 respectively; The SMF (single mode fiber) portion of the first peanut structure 3 is fused with the SMF (single mode fiber) portion of the second peanut structure 4 to form a Mach-Zehnder structure; The SMF (single mode fiber) part on the left side of the Mach-Zehnder structure is fused together with the SMF (single mode fiber) end on the right side of the Bragg grating (1) to obtain a hybrid structure interference sensor.

[0033] See also Figure 2 , a process for preparing a Bragg grating 1, comprising: Prepare the femtosecond laser 11, phase mask 12 and single-mode quartz optical fiber 13 in advance The light beam emitted by the femtosecond laser 11 is irradiated onto the phase mask 12 to form interference fringes with a periodic structure, thereby generating a refractive index change on the core mode of the single-mode quartz optical fiber 13, thereby writing the Bragg grating 1.

[0034] Specifically, in the process of preparing the Bragg grating 1, the femtosecond laser 11 plays a key role. The ultrashort pulses it produces have extremely high energy and extremely short duration, about 10 to the negative 15th power of seconds. The characteristics of this laser enable it to produce high-density energy deposition in the optical fiber. When the femtosecond laser 11 is irradiated onto the phase mask 12, due to the special design of the phase mask 12, the 0th order diffraction light (i.e., the light that passes directly through the mask) is suppressed, while the ±1st order diffraction light (i.e., the light deflected to both sides) is enhanced, which results in the formation of two beams with a specific phase difference, and MZ interference occurs in their overlapping area, forming interference fringes with a periodic light intensity distribution.

[0035] The uneven beam intensity distribution of the interference fringes irradiates the fiber core to varying degrees, and the thermal effect caused by the beam irradiation can change the refractive index of the core material, thereby forming a periodic refractive index change in the fiber, which is eventually permanently recorded in the fiber, forming a Bragg grating1.

[0036] It should be noted that the optical fiber of the embodiment of the present invention can be a step-index single-mode quartz optical fiber (SMF-28), which acts as a transmission medium and is characterized by having a step-change in the core and cladding refractive index, so that it can effectively transmit single-mode light.

[0037] Furthermore, the process of preparing the double peanut structure 2 comprises: See also Figure 3 and Figure 4 The SMF (single-mode fiber) part of the first peanut structure 3 and the SMF (single-mode fiber) part of the second double peanut structure 4 are respectively discharged multiple times using a fiber fusion splicer, the purpose of which is to heat the SMF (single-mode fiber) parts so that they form ellipsoidal shapes due to thermal melting.

[0038] It should be noted that the portion to be fused and heated is the tip of the optical fiber.

[0039] Furthermore, in the embodiment of the present invention, the ellipsoidal shape condition is set, including: Discharge time length of optical fiber fusion splicer: 2000ms; Discharge intensity of optical fiber fusion splicer: +60bit; Extension length beyond SMF: 50 .

[0040] See also Figure 5 , two ellipsoidal single-mode optical fibers are manually discharged and fused to form peanut-shaped structures, which meet the following conditions: Discharge time length of optical fiber fusion splicer: 2000ms; Discharge intensity of optical fiber fusion splicer: +40bit; Fiber overlap: 40 .

[0041] The two peanut-shaped single-mode optical fiber SMF parts are fused again to form a double peanut structure 2 connected in series. Example 4

[0042] A sensitivity measurement method for a hybrid structure sensor, comprising: A test environment for simultaneously measuring temperature and strain is established by using a pre-built broadband light source 6 and a spectrum analyzer 7 through a sensor to be detected 10; The sensor 10 to be tested is placed in turn between an electric furnace 8 and two glass slides 9 for testing. By adjusting the temperature of the electric furnace 8 and placing weights on the glass slides 9, the response of the sensor 10 to be tested to temperature and strain is determined.

[0043] For details, see Figure 6 , for temperature measurement: Light is emitted from a broadband light source 6, passes through a hybrid structure interference sensor placed in an electric furnace 8, and then enters a spectrum analyzer 7; The temperature in the electric furnace 8 is adjusted from 30° C. to 80° C. in steps of 10° C., and each time the transmission spectrum of the sensor 10 to be detected, ie, the spectral characteristics of the light transmitted through the sensor, is measured using the spectrometer analyzer 7 .

[0044] See also Figure 7 , for the measurement of strain: Light is emitted from a broadband light source 7, passes through a sensor 10 to be monitored placed between two glass slides 9, and applies a specific strain to the sensor 10 to be monitored. In order to ensure uniform force, a parallel single-mode optical fiber is placed next to the sensor to ensure uniform force, and then enters the spectrum analyzer; Weights are placed on the glass slide 9 from 0 g to 1000 g in steps of 50 g to apply different pressures, thereby generating different strains. The transmission spectra of the spectrometer under different strains are recorded to analyze the response of the sensor to the strain.

[0045] 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

1. A hybrid structure sensor, characterized in that: The invention comprises a Bragg grating (1) and a double peanut structure (2) which are cascaded with each other. When a light beam transmitted in an optical fiber passes through the Bragg grating (1), it is determined whether the light beam satisfies a Bragg condition. If the Bragg condition is satisfied, the light beam is reflected in the optical fiber, and the reflected light beam is used to monitor temperature changes. If the Bragg condition is not satisfied, the light beam enters the double peanut structure (2). The double peanut structure (2) comprises a first peanut structure (3) and a second peanut structure (4); when passing through the first peanut structure (3), a portion of the light beam is transferred from the core mode of the optical fiber to the cladding mode; when passing through the second peanut structure (4), the light beam transferred to the cladding mode is coupled back to the core mode again, and the light beam coupled back to the core mode forms Mach-Zehnder interference with the original light beam in the core mode, which is used to monitor the strain state of the optical fiber.

2. The hybrid structure sensor according to claim 1, characterized in that: The expression satisfying the Bragg condition is: ； in, represents the central wavelength of the Bragg grating; Represents the effective refractive index of the fiber core; represents the period of the fiber Bragg grating.

3. The hybrid structure sensor according to claim 1, characterized in that: The light beam is reflected in the optical fiber, and the reflected light beam is used to monitor the change of temperature, including: Using a spectrometer to record the wavelength and intensity of the reflected light beam to form a reflection spectrum; By measuring the reflection spectrum, the temperature change experienced by the Bragg grating is determined.

4. The hybrid structure sensor according to claim 1, characterized in that: The light beam coupled back into the fiber core again forms interference with the original light beam in the core mode, which is used to monitor the strain state of the optical fiber, including: When the light beam coupled back from the cladding mode meets the original light beam in the core mode in space, a phase difference is generated, and an interference spectrum is formed according to the phase difference, and a spectrometer is used to capture the position of a characteristic wavelength in the interference spectrum and measure the interference light intensity related to the characteristic wavelength; When the hybrid structure interference sensor is subjected to external strain, the refractive indexes of the core mode and the cladding mode change accordingly, thereby changing the phase difference between the light beam coupled back from the cladding mode and the original light beam in the core mode; According to the change of the phase difference, the characteristic wavelength in the interference spectrum moves and the corresponding interference light intensity distribution changes. By measuring the movement of the characteristic wavelength and the change of the interference light intensity, the strain of the optical fiber is obtained.

5. The hybrid structure sensor according to claim 4, characterized in that: The interference light intensity associated with the characteristic wavelength is measured, and the expression of the interference light intensity is: ； in, Indicates the light intensity of the core mode; represents the light intensity of the cladding mode; Indicates the operating wavelength; represents the refractive index difference between the effective refractive index of the cladding mode and the effective refractive index of the core mode; L represents the distance between the two peanut-shaped structures; represents the interference light intensity; The relationship between the shift of the characteristic wavelength and the change of strain is: ； in, represents the applied stress change; It represents the difference between the effective refractive index of the core mode and the cladding mode; n represents the nth-order interference trough.

6. A method for preparing a hybrid structure sensor as claimed in claims 1 to 5, characterized in that: include: Prepare Bragg grating (1) and double peanut structure (2) respectively; The single-mode optical fiber portion of the first peanut structure (3) is fused with the single-mode optical fiber portion of the second peanut structure (4) to form a Mach-Zehnder structure; The single-mode optical fiber portion of the Mach-Zehnder structure is fused together with the single-mode optical fiber end of the Bragg grating (1) to obtain the hybrid structure interference sensor.

7. The method for preparing the hybrid structure sensor according to claim 6, characterized in that: The method for preparing a Bragg grating (1) comprises: Prepare a femtosecond laser (11), a phase mask (12), and a single-mode quartz optical fiber (13) in advance; The light beam generated by the femtosecond laser (11) is irradiated onto the phase mask (12) to form periodic interference fringes, thereby generating a refractive index change on the core mode of the single-mode quartz optical fiber (13), and a Bragg grating (1) is inscribed according to the refractive index change.

8. The method for preparing the hybrid structure sensor according to claim 6, characterized in that: The method for preparing the double peanut structure (2) comprises: Using an optical fiber fusion splicer, discharge the single-mode optical fiber portion of the first peanut structure (3) and the single-mode optical fiber portion of the second peanut structure (4) multiple times to form ellipsoidal shapes respectively; Manual discharge fusion splicing of two ellipsoidal single-mode optical fibers to form peanut-shaped structures; The two single-mode optical fiber sections of the peanut-shaped structure are fused again to form a series-connected double peanut structure (2).

9. The method for preparing the hybrid structure sensor according to claim 8, characterized in that: The ellipsoidal shape is formed to meet the following conditions: Discharge time length of optical fiber fusion splicer: 2000ms±200ms; Discharge intensity of optical fiber fusion splicer: +60bit±5bit; Extension length beyond SMF: 50 -70 ; The formation of the peanut-like structure satisfies the following conditions: Discharge time length of optical fiber fusion splicer: 2000ms±200ms; Discharge intensity of optical fiber fusion splicer: +40bit±10bit; Fiber overlap: 40 -60 .

10. A sensitivity measurement method of a hybrid structure sensor according to any one of claims 1 to 5, characterized in that: include: A test environment for simultaneously measuring temperature and strain is established by using a pre-built broadband light source (6) and a spectrum analyzer (7) through a sensor to be detected (10); The sensor (10) to be tested is placed in a preset electric furnace (8) and between two glass slides (9) for testing, and the response of the sensor (10) to temperature and strain is determined by adjusting the temperature of the electric furnace (8) and placing weights on the glass slides (8).

Images