Temperature sensor probe, preparation method and temperature sensor

Abstract

The invention belongs to the technical field of optical fiber temperature sensors, and particularly relates to a temperature sensor probe, a preparation method and a temperature sensor.The temperature sensor probe comprises a seven-core optical fiber, a polymer base is arranged on the seven-core optical fiber, a polymer FPI is arranged at the center of the upper surface of the polymer base, and the polymer FPI is of a solid polymer column structure; an open cavity FPI is formed in the side part of the upper surface of the polymer base; one end, far away from the seven-core optical fiber, of the polymer FPI and the tangent plane of the seven-core optical fiber serve as two reflecting surfaces, an area between the two reflecting surfaces forms an interference area, and a cavity formed by the interference area forms an interference cavity in the double-FPI interference structure, namely a first sensing cavity; one end face, away from the seven-core optical fiber, of the open cavity FPI serves as a first reflecting face, the first reflecting face and the tangent plane of the seven-core optical fiber serve as two reflecting faces, and a cavity between the open cavity FPI and the tangent plane of the seven-core optical fiber forms the other interference cavity, namely a second sensing cavity, in the double-polymer interference structure. According to the invention, the requirement of ultrahigh sensitivity can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber temperature sensors, and in particular relates to a temperature sensor probe, a preparation method and a temperature sensor. Background Art

[0002] Temperature measurement plays a critical role in environmental monitoring, industrial processes, civil engineering, biomedical research, chemical analysis, aerospace technology, and other fields. Compared to other temperature sensors, fiber optic interferometry sensors offer advantages such as high stability, compactness, and strong resistance to electromagnetic interference. These sensors typically utilize fiber interferometers, fiber Bragg gratings, microfiber couplers, and fiber resonators. Among these sensors, the Fabry-Perot interferometer has emerged as a highly reliable temperature measurement solution.

[0003] To improve the sensitivity of temperature sensors and meet the demand for higher sensitivity, enhanced vernier effects have been applied to various sensor configurations. While this approach significantly improves sensitivity, it suffers from high technical complexity, poor repeatability, and excessively large device size, making it difficult to meet miniaturization requirements. To address this issue, the present invention proposes a temperature sensor probe, a preparation method, and a temperature sensor. Summary of the Invention

[0004] The object of the present invention is to provide a temperature sensor probe, a preparation method and a temperature sensor that can meet the requirements of ultra-high sensitivity.

[0005] The technical solutions adopted by the present invention are as follows:

[0006] A temperature sensor probe, characterized by comprising a seven-core optical fiber, a polymer base disposed on the seven-core optical fiber, a polymer FPI disposed at the center of the upper surface of the polymer base, the polymer FPI being a solid polymer column structure, and an open cavity FPI disposed on the side of the upper surface of the polymer base;

[0007] The end of the polymer FPI away from the seven-core optical fiber and the seven-core optical fiber cut surface serve as two reflection surfaces. The area between the two reflection surfaces constitutes an interference area. The cavity formed by this interference area constitutes an interference cavity in the dual-FPI interference structure, namely the first sensing cavity.

[0008] One end face of the open cavity FPI away from the seven-core optical fiber serves as a first reflection surface, the first reflection surface and the seven-core optical fiber cut surface serve as two reflection surfaces, and the cavity between the open cavity FPI and the seven-core optical fiber cut surface constitutes another interference cavity in the dual-polymer interference structure, namely the second sensing cavity.

[0009] Preferably, the core and cladding diameters of the seven-core optical fiber are 8 μm and 150 μm respectively, and the core spacing is 41.5 μm.

[0010] Preferably, the polymer FPI has a diameter of 15 μm and a length of 55 μm, and the refractive index of the polymer material after curing is about 1.58; the cavity length of the open cavity FPI is 70 μm.

[0011] Preferably, the cut surface of the seven-core optical fiber and the polymer / air interface and the corresponding interface of the open cavity FPI respectively serve as reflectors for generating interference resonance.

[0012] Preferably, the open cavity FPI is designed as a prism. This prism-like design avoids multiple Fabry-Perot resonances, ensuring that the interference resonance primarily originates from the intended two reflected light beams. This makes the measured interference spectrum clearer and more accurate, facilitating subsequent research and analysis of spectral characteristics. Furthermore, it optimizes the interference effect. Based on the principle of interference, the prism-like structure alters the propagation path and reflection of light, resulting in more distinct and stable interference fringes when the two reflected light beams interfere.

[0013] Preferably, the seven-core optical fiber is connected to a seven-core fan-in fan-out device, through which the single-cavity spectrum can be measured separately, thereby calculating the amplification factor of the temperature sensor.

[0014] A method for preparing a temperature sensor probe, wherein the temperature sensor probe is prepared by a temperature sensor probe preparation method based on 3D printing, wherein the temperature sensor probe preparation method comprises the following specific steps:

[0015] S1: Select a suitable seven-core optical fiber; the seven-core optical fiber used is MC1010-A, which has a core cladding diameter of 8μm and 150μm and a core spacing of 41.5μm. Use professional cutting tools to cut it to the appropriate length, and then carefully clean the optical fiber surface with a cleaning agent such as alcohol to remove impurities and oil stains to ensure that the optical fiber surface is clean. After cleaning, firmly install the optical fiber on the optical fiber bracket.

[0016] S2: Prepare ATE-Dip-1.52 photoresist solution with a refractive index of 1.52, fix the holder containing the optical fiber on the 3D translation stage using air pressure, and adjust the position to ensure that the tip of the optical fiber is in the appropriate printing position;

[0017] S3: Using a 40× magnifying lens (NA = 1.3) and an oil-immersion objective lens, a femtosecond laser with a central wavelength of 515 nm was accurately focused on the fiber end. A pre-designed 3D file containing the polymer base, polymer FPI, and open-cavity FPI structure was imported into the laser writing device. The laser power was set to 1 mW, the slice spacing was 500 nm, and ultra-high-speed mode was selected to begin layer-by-layer printing. For the first few layers, the printing depth was controlled to ensure that the print reached the seven-core fiber to enhance the mechanical strength of the structure.

[0018] S4: After printing is completed, the fiber tip is rinsed with acetone and isopropyl alcohol in sequence to completely remove the uncured photoresist, obtaining the final temperature sensor probe based on 3D printed fiber tip integrated FPI.

[0019] The temperature sensor comprises: a wide-spectrum light source, a spectrometer, a fiber optic circulator, and a temperature sensor probe, wherein the wide-spectrum light source is connected to the first port of the fiber optic circulator, the spectrometer adopts the spectrum demodulator, the spectrometer is connected to the third port of the fiber optic circulator, and the optical fiber cable in the temperature sensor probe is connected to the second port of the fiber optic circulator;

[0020] In the temperature sensor, a broadband light source is used to emit a broadband spectrum, and a fiber circulator is used to isolate the broadband spectrum signal emitted by the broadband light source from the composite envelope interference spectrum signal output by the sensor probe. The broadband spectrum emitted by the broadband light source passes through the fiber circulator and then through a seven-core fan-in / fan-out device before being input into the temperature sensor probe. The seven-core optical fiber in the temperature sensor probe, along with a first cavity (polymer Fabry-Perot cavity) and a second cavity (open Fabry-Perot cavity) form a vernier unit. The broadband spectrum input into the sensor probe generates dual-beam interference under the action of the vernier unit, forming an interference spectrum. The interference spectrum is transmitted via optical fiber cable to the seven-core fan-in / fan-out device and then back to the spectrometer through the fiber circulator for spectral demodulation.

[0021] The technical effects achieved by the present invention are:

[0022] 1. This application is based on the enhanced vernier effect. The interference spectra of the polymer FPI and the open-cavity FPI exhibit different trends when the temperature changes. This difference makes the spectral envelope more sensitive to temperature changes. When the temperature changes, the interference spectra of the polymer FPI and the open-cavity FPI shift in opposite directions. By superimposing and analyzing these two spectra, the resulting resonant wavelength changes in the spectral envelope can more significantly reflect temperature changes. This spectral adjustment method not only improves the temperature sensitivity of the sensor, but also makes the measurement results more intuitive and easier to analyze.

[0023] 2. The temperature sensor of the present application utilizes the different response characteristics of polymer FPI and open cavity FPI to temperature to achieve higher temperature sensitivity. When the temperature changes, the optical properties of polymer FPI and open cavity FPI will change accordingly, causing the interference spectrum to shift. The temperature sensitivity of the sensor was measured to be 21.01nm / ℃, which means that for every 1℃ change in temperature, the wavelength of the interference spectrum will change significantly by 21.01nm. Compared with traditional temperature sensors, this sensitivity can more accurately capture subtle temperature fluctuations. At the same time, the experimental system used in this application, including a broadband light source and a spectrum analyzer, can perform high-precision detection and analysis of the spectrum. The broadband light source provides spectral information, and the spectrum analyzer can accurately measure the wavelength changes of the interference spectrum. Its wavelength accuracy of 0.05nm ensures the accurate capture of tiny spectral shifts caused by temperature changes.

[0024] 3. From the perspective of structural design, the present application integrates the polymer FPI and the open cavity FPI at the tip of the seven-core optical fiber. This integrated structural design enhances the overall stability of the sensor. The seven-core optical fiber provides stable physical support for the internal FPI structure, reducing the risk of structural deformation due to external vibration or displacement. At the same time, the relative positions of the polymer FPI and the open cavity FPI at the tip of the optical fiber are fixed. During temperature changes, the interaction and relative displacement between the two are extremely small, ensuring the stability of the interference spectrum, and thus ensuring the stability and reliability of the temperature measurement results. During long-term use, this stable structure can effectively avoid measurement errors caused by loose or displacement of components and maintain the high performance of the sensor. In terms of manufacturing process, the precise control of parameters such as laser power and slicing space during the 3D printing process, as well as the operation of printing the first few layers into the silicon fiber to enhance mechanical strength, have greatly improved the stability of the sensor. Precise printing parameters ensure the consistency and accuracy of the FPI structure, and the performance of each sensor can be highly consistent, reducing performance fluctuations caused by differences in the manufacturing process. The enhanced mechanical strength enables the sensor to maintain structural integrity when subjected to a certain degree of external impact, vibration or sudden temperature change, avoiding the impact of structural damage on measurement results and ensuring the sensor's ability to work stably for a long time in complex environments.

[0025] 4. The sensor of this application uses 3D printing technology to integrate two types of FPIs at the tip of a seven-core optical fiber, resulting in a compact overall structure. The seven-core optical fiber itself is relatively small, with core and cladding diameters of 8μm and 150μm, respectively, and a core spacing of 41.5μm. Combined with the polymer FPI and open-cavity FPI integrated via 3D printing, the volume of the entire sensor is kept to a very small range. This compact structure facilitates installation in various complex environments and confined spaces. Compared to traditional temperature sensors, its significant size advantage makes it more versatile and flexible in application scenarios.

[0026] 5. The 3D printing production process adopted in this application has significant advantages. The entire process is digitally controllable. By importing the designed 3D file into the device, the layer-by-layer printing process can be precisely controlled. This digital production method greatly improves the flexibility and precision of production. The structural parameters of the sensor, such as the diameter and length of the polymer column and the cavity length of the open cavity FPI, can be quickly adjusted according to different application requirements. In addition, the ultra-high-speed mode is used in the printing process, combined with the optimized laser power of 1mW and the slice space of 500nm, which greatly shortens the production time and improves production efficiency. In addition, the post-processing steps in the production process are simple and effective. The fiber tip is rinsed with acetone and isopropyl alcohol to remove uncured photoresist. These two organic solvents have good solubility for photoresist and can completely remove residual photoresist to ensure the cleanliness and optical performance of the sensor surface. The entire production process does not require complex equipment and cumbersome operating steps, which reduces production costs and technical barriers.

[0027] 6. In this application, a seven-core fan-in and fan-out device of a spectrometer is connected after the seven-core optical fiber. During fan-out, each core of the seven-core optical fiber is output as a single-mode optical fiber. The spectrum results of a single fiber core can be viewed by connecting the single-mode optical fiber to an optical circulator and then outputting it to the spectrometer. The sensor actually only uses the middle core and one side core of the seven-core optical fiber. When the temperature changes, the spectral shift directions of the two interferometers are opposite. The signal distribution and merging of the fan-in and fan-out devices significantly enhance the cursor effect, thereby greatly improving the sensitivity. At the same time, the single-core spectrum can also be measured by the seven-core optical fiber fan-in and fan-out device, and the amplification factor of the sensor for temperature change measurement can be calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is an overall schematic diagram of the temperature sensor of the present invention;

[0029] Figure 2 It is an overall schematic diagram of a temperature sensor probe of the present invention;

[0030] Figure 3 This is the differential composite vernier interferometer cavity spectrum obtained by the temperature sensor of the present application under the conditions of 22℃-34℃;

[0031] Figure 4 This is a temperature calibration test data chart obtained by the temperature sensor of this application under the conditions of 22℃-34℃.

[0032] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0033] 1. Broad-spectrum light source; 2. Spectrometer; 3. Fiber circulator; 4. Fiber optic cable; 5. Seven-core fan-in / fan-out device; 6. Seven-core optical fiber; 7. Polymer base; 8. Polymer FPI; 9. First reflective surface; 10. Open-cavity FPI. DETAILED DESCRIPTION

[0034] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the following examples. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection of the present invention.

[0035] Example 1:

[0036] like Figures 1-4 As shown, a temperature sensor probe includes a seven-core optical fiber 6, a polymer base 7 is provided on the seven-core optical fiber 6, a polymer FPI 8 is provided at the center of the upper surface of the polymer base 7, and an open cavity FPI 10 is provided on the side of the upper surface of the polymer base 7;

[0037] The end of the polymer FPI 8 away from the seven-core optical fiber 6 and the cut surface of the seven-core optical fiber 6 serve as two reflection surfaces. The area between the two reflection surfaces constitutes an interference area. The cavity formed by this interference area constitutes an interference cavity in the dual-FPI interference structure, namely the first sensing cavity.

[0038] One end face of the open cavity FPI10 away from the seven-core optical fiber 6 serves as the first reflection surface 9, and the first reflection surface 9 and the cut surface of the seven-core optical fiber 6 serve as two reflection surfaces. The cavity between the open cavity FPI10 and the cut surface of the seven-core optical fiber 6 constitutes another interference cavity in the dual-polymer interference structure, namely the second sensing cavity.

[0039] Preferably, the core and cladding diameters of the seven-core optical fiber 6 are 8 μm and 150 μm respectively, and the core spacing is 41.5 μm.

[0040] Preferably, the polymer FPI8 has a diameter of 15 μm and a length of 55 μm, and the refractive index of the polymer material after curing is about 1.58; the length of the open cavity FPI10 is 70 μm.

[0041] Preferably, the cut surface of the seven-core optical fiber 6 and the polymer / air interface and the corresponding interface of the open cavity FPI 10 serve as reflectors respectively for generating interference resonance.

[0042] Preferably, the open cavity FPI10 is designed in a prism shape. This prism design can avoid multiple Fabry-Perot resonances, ensuring that the interference resonance mainly comes from the expected two beams of reflected light, making the measured interference spectrum clearer and more accurate, facilitating subsequent research and analysis of spectral characteristics. It also optimizes the interference effect. From the perspective of interference principles, the prism structure changes the propagation path and reflection of light, allowing the two beams of reflected light to produce more obvious and stable interference fringes when interfering.

[0043] Preferably, the seven-core optical fiber 6 is connected to a seven-core fan-in fan-out device 5, through which the single-cavity spectrum can be measured separately, thereby calculating the amplification factor of the temperature sensor.

[0044] Example 2:

[0045] A method for preparing a temperature sensor probe, wherein the temperature sensor probe is prepared by a temperature sensor probe preparation method based on 3D printing, wherein the temperature sensor probe preparation method comprises the following specific steps:

[0046] S1: Select a suitable seven-core optical fiber 6; the seven-core optical fiber 6 used is MC1010-A, with a core cladding diameter of 8μm and 150μm and a core spacing of 41.5μm. Use professional cutting tools to cut it to the appropriate length, then carefully clean the optical fiber surface with a cleaning agent such as alcohol to remove impurities and oil stains to ensure that the optical fiber surface is clean. After cleaning, firmly install the optical fiber on the optical fiber holder.

[0047] S2: Prepare ATE-Dip-1.52 photoresist solution with a refractive index of 1.52, fix the holder containing the optical fiber on the 3D translation stage using air pressure, and adjust the position to ensure that the tip of the optical fiber is in the appropriate printing position;

[0048] S3: Using a 40× magnifying glass (NA=1.3) oil-immersion objective, a femtosecond laser with a central wavelength of 515 nm is accurately focused on the fiber end. The pre-designed 3D file containing the polymer base 7, polymer FPI 8, and open cavity FPI 10 structure is imported into the laser writing device. The laser power is set to 1 mW and the slice space is set to 500 nm. The ultra-high-speed mode is selected to start layer-by-layer printing. During the first few layers of printing, the printing depth is controlled so that it prints into the seven-core optical fiber 6 to enhance the mechanical strength of the structure.

[0049] S4: After printing is completed, the fiber tip is rinsed with acetone and isopropyl alcohol in sequence to completely remove the uncured photoresist, obtaining the final temperature sensor probe based on 3D printed fiber tip integrated FPI.

[0050] Example 3:

[0051] like Figures 1-4 As shown, the temperature sensor includes: a wide-spectrum light source 1, a spectrometer 2, a fiber optic circulator 3, and a temperature sensor probe, wherein the wide-spectrum light source 1 is connected to the first port of the fiber optic circulator 3, the spectrometer 2 adopts the spectrum demodulator, the spectrometer 2 is connected to the third port of the fiber optic circulator 3, and the optical fiber cable 4 in the temperature sensor probe is connected to the second port of the fiber optic circulator 3;

[0052] In the temperature sensor, a broadband light source 1 is used to emit a broadband spectrum, and a fiber circulator 3 is used to isolate the broadband spectrum signal emitted by the broadband light source 1 from the composite envelope interference spectrum signal output by the sensor probe. The broadband spectrum emitted by the broadband light source 1 is input into the temperature sensor probe through the fiber circulator 3 and then through the seven-core fan-in / fan-out device 5. The seven-core optical fiber 6 in the temperature sensor probe forms a vernier unit with the first cavity, which is a polymer Fabry-Perot cavity, and the second cavity, which is an open Fabry-Perot cavity. Under the action of the vernier unit, the broadband spectrum input into the sensor probe generates dual-beam interference to form an interference spectrum. The interference spectrum is transmitted via the optical fiber cable 4 to the seven-core fan-in / fan-out device 5, and then transmitted back to the spectrometer 2 through the fiber circulator 3 to achieve spectral demodulation.

[0053] like Figures 1-4 As shown, in order to verify the temperature sensitivity performance of the temperature sensor of the present application, the present application conducted a temperature calibration test on the temperature sensor obtained in this embodiment, and the test results are shown in FIG. Figure 4 As shown. Figure 4 It can be seen that the temperature sensitivity of the temperature sensor obtained in this embodiment is 21.01 nm / ° C. In this embodiment, the spectrum demodulator used is AQ6375, and the demodulation accuracy of the spectrometer 2 is 0.05 nm.

[0054] like Figures 1-4 As shown, in addition, the present application also adopts a method of obtaining temperature by using interference spectrum demodulation to demodulate the data collected by the spectrum demodulator. Starting from measuring the ambient temperature, the moving trajectory of the composite envelope in the interference spectrum output by the sensor is continuously locked and tracked to determine the accurate envelope interference spectrum for temperature calculation; then, the corresponding temperature value is calculated based on the peak wavelength of the determined envelope interference spectrum. Specifically, starting from the initial temperature, the moving path of the envelope interference spectrum is continuously tracked. After determining the target envelope, the envelope wavelength value (peak or trough) in the spectrum analyzer data is extracted, and the actual temperature value is calculated based on the pre-calibrated envelope wavelength-temperature correspondence.

[0055] In the embodiment, the sensor probe is first placed in a constant temperature water bath, and the interference spectrum is obtained by a spectrum analyzer. The peak or trough value of the envelope interference spectrum is extracted as a calibration reference; then the water bath temperature is changed and the above steps are repeated to obtain multiple sets of "temperature-envelope wavelength" calibration data, and finally a linear relationship between temperature and wavelength is fitted ( Figure 4 ). During actual temperature measurement, the sensor is placed in the environment to be measured, and the actual temperature can be inverted by combining the envelope wavelength value obtained in real time with the fitting formula.

[0056] In summary, the spectrum analyzer detects changes in the interference spectrum in real time and records the resonant wavelength of the spectrum envelope. The recorded data is analyzed, and a curve is drawn showing the relationship between the resonant wavelength of the spectrum envelope and the temperature. The linear relationship between wavelength and temperature is obtained through linear fitting, and the corresponding temperature is obtained. Starting from the starting temperature, the changes in the resonant wavelength of the spectrum envelope are continuously measured and tracked. The changing characteristics of the resonant wavelength of the spectrum envelope when the temperature changes are utilized to avoid other interference factors and achieve accurate temperature measurement. Compared with traditional methods, this method avoids the problem of temperature jumps caused by multi-envelope interference by continuously tracking the moving trajectory of the envelope spectrum. Since the ambient temperature usually changes continuously and slowly, the system can effectively eliminate the interference of other envelopes by recording the changing trend of the envelope wavelength in real time, thereby achieving high-precision and continuous temperature measurement.

[0057] 1. This application is based on the enhanced vernier effect. The interference spectra of polymer FPI8 and open cavity FPI10 exhibit different trends when the temperature changes. This difference makes the spectral envelope more sensitive to temperature changes. When the temperature changes, the interference spectra of polymer FPI8 and open cavity FPI10 will shift in opposite directions. By superimposing and analyzing these two spectra, the resonant wavelength changes of the spectral envelope can more significantly reflect the temperature changes. This spectral adjustment method not only improves the temperature sensitivity of the sensor, but also makes the measurement results more intuitive and easier to analyze.

[0058] 2. The temperature sensor of the present application utilizes the different response characteristics of polymer FPI8 and open cavity FPI10 to temperature to achieve higher temperature sensitivity. When the temperature changes, the optical properties of polymer FPI8 and open cavity FPI10 will change accordingly, causing the interference spectrum to shift. The temperature sensitivity of the sensor was measured to be 21.01nm / ℃, which means that for every 1℃ change in temperature, the wavelength of the interference spectrum will change significantly by 21.01nm. Compared with traditional temperature sensors, this sensitivity can more accurately capture subtle fluctuations in temperature. At the same time, the experimental system used in this application, including a broadband light source and a spectrum analyzer, can perform high-precision detection and analysis of the spectrum. The broadband light source provides spectral information, and the spectrum analyzer can accurately measure the wavelength changes of the interference spectrum. Its wavelength accuracy of 0.05nm ensures the accurate capture of tiny spectral shifts caused by temperature changes.

[0059] 3. From a structural design perspective, the present application integrates the polymer FPI8 and the open cavity FPI10 at the tip of the seven-core optical fiber 6. This integrated structural design enhances the overall stability of the sensor. The seven-core optical fiber 6 provides stable physical support for the internal FPI structure, reducing the risk of structural deformation due to external vibration or displacement. At the same time, the relative positions of the polymer FPI8 and the open cavity FPI10 at the tip of the optical fiber are fixed. During temperature changes, the interaction and relative displacement between the two are extremely small, ensuring the stability of the interference spectrum and, in turn, ensuring the stability and reliability of the temperature measurement results. During long-term use, this stable structure can effectively avoid measurement errors caused by loose or displacement components and maintain the high performance of the sensor. In terms of manufacturing process, the precise control of parameters such as laser power and slicing space during the 3D printing process, as well as the operation of printing the first few layers into the silicon fiber to enhance mechanical strength, have greatly improved the stability of the sensor. Precise printing parameters ensure the consistency and accuracy of the FPI structure, and the performance of each sensor can be highly consistent, reducing performance fluctuations caused by differences in the manufacturing process. The enhanced mechanical strength enables the sensor to maintain structural integrity when subjected to a certain degree of external impact, vibration or sudden temperature change, avoiding the impact of structural damage on measurement results and ensuring the sensor's ability to work stably for a long time in complex environments.

[0060] 4. The sensor of this application uses 3D printing technology to integrate two FPIs at the tip of the seven-core optical fiber 6, and the overall structure is compact. The seven-core optical fiber 6 itself is relatively small in size, with core and cladding diameters of 8μm and 150μm respectively, and a core spacing of 41.5μm. Combined with the polymer FPI8 and open cavity FPI10 integrated by 3D printing, the volume of the entire sensor is controlled within an extremely small range. This compact structure is easy to install in various complex environments and small spaces. Compared with traditional temperature sensors, its obvious size advantage makes it more extensive and flexible in application scenarios.

[0061] 5. The 3D printing production process adopted in this application has significant advantages. The entire process is digitally controllable. By importing the designed 3D file into the device, the layer-by-layer printing process can be precisely controlled. This digital production method greatly improves the flexibility and precision of production. The structural parameters of the sensor, such as the diameter and length of the polymer column and the cavity length of the open cavity FPI10, can be quickly adjusted according to different application requirements. In addition, the ultra-high-speed mode is used in the printing process, combined with the optimized laser power of 1mW and the slice space of 500nm, which greatly shortens the production time and improves production efficiency. In addition, the post-processing steps in the production process are simple and effective. The fiber tip is rinsed with acetone and isopropyl alcohol to remove uncured photoresist. These two organic solvents have good solubility for photoresist and can completely remove residual photoresist to ensure the cleanliness and optical performance of the sensor surface. The entire production process does not require complex equipment and cumbersome operating steps, which reduces production costs and technical barriers.

[0062] 6. In this application, a seven-core fan-in and fan-out device 5 is connected after the seven-core optical fiber 6. During fan-out, each core of the seven-core optical fiber 6 is output as a single-mode optical fiber. By connecting the single-mode optical fiber to an optical circulator and then outputting it to the spectrometer 2, the spectrum results of a single core can be viewed. The sensor actually only uses the middle core and one side core of the seven-core optical fiber 6. When the temperature changes, the spectral shift directions of the two interferometers are opposite. The signal distribution and merging of the fan-in and fan-out devices significantly enhance the cursor effect, thereby greatly improving the sensitivity. At the same time, the single-core spectrum can also be measured by the fan-in and fan-out device of the seven-core optical fiber 6, and the amplification factor of the sensor for temperature change measurement can be calculated.

[0063] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained herein shall, unless otherwise specified or limited, be implemented in accordance with conventional means in the art.

Claims

1. A temperature sensor probe, characterized in that: The invention comprises a seven-core optical fiber (6), wherein a polymer base (7) is provided on the seven-core optical fiber (6), a polymer FPI (8) is provided at the center of the upper surface of the polymer base (7), the polymer FPI (8) is a solid polymer column structure, and an open cavity FPI (10) is provided on the side of the upper surface of the polymer base (7); One end of the polymer FPI (8) away from the seven-core optical fiber (6) and the cut surface of the seven-core optical fiber (6) serve as two reflection surfaces, and the area between the two reflection surfaces constitutes an interference area. The cavity formed by the interference area constitutes an interference cavity in the double FPI interference structure, namely, the first sensing cavity; An end face of the open cavity FPI (10) away from the seven-core optical fiber (6) serves as a first reflection surface (9), the first reflection surface (9) and the cut surface of the seven-core optical fiber (6) serve as two reflection surfaces, and the cavity between the open cavity FPI (10) and the cut surface of the seven-core optical fiber (6) constitutes another interference cavity in the dual-polymer interference structure, namely, a second sensing cavity.

2. A temperature sensor probe according to claim 1, characterized in that: The core and cladding diameters of the seven-core optical fiber (6) are 8 μm and 150 μm respectively, and the core spacing is 41.5 μm.

3. A temperature sensor probe according to claim 2, characterized in that: The polymer FPI (8) has a diameter of 15 μm and a length of 55 μm, and the refractive index of the polymer material after curing is about 1.58; the cavity length of the open cavity FPI (10) is 70 μm.

4. The temperature sensor probe according to claim 3, characterized in that: The cut surface of the seven-core optical fiber (6) and the corresponding interfaces of the polymer / air interface and the open cavity FPI (10) serve as reflectors respectively for generating interference resonance.

5. The temperature sensor probe according to claim 4, characterized in that: The open cavity FPI (10) is designed in a prism shape.

6. The temperature sensor probe according to claim 5, characterized in that: The seven-core optical fiber (6) is connected to a seven-core fan-in and fan-out device (5).

7. A method for preparing a temperature sensor probe according to any one of claims 1 to 6, characterized in that: The temperature sensor probe is prepared by a temperature sensor probe preparation method based on 3D printing, wherein the temperature sensor probe preparation method includes the following specific steps: S1: Select a suitable seven-core optical fiber (6); use a professional cutting tool to cut it to a suitable length, then carefully clean the surface of the optical fiber with alcohol or other cleaning agents to remove impurities and oil stains. After cleaning, firmly install the optical fiber on the optical fiber bracket; S2: Prepare ATE-Dip-1.52 photoresist solution with a refractive index of 1.52, fix the holder containing the optical fiber on the 3D translation stage using air pressure, and adjust the position to ensure that the tip of the optical fiber is in the appropriate printing position; S3: Using a 40× magnifying glass and an oil-immersion objective lens, a femtosecond laser with a central wavelength of 515 nm is accurately focused on the end of the optical fiber; a pre-designed 3D file containing a polymer base (7), a polymer FPI (8), and an open cavity FPI (10) structure is imported into the laser writing device, the laser power is set to 1 mW, the slice space is set to 500 nm, and the ultra-high-speed mode is selected to start layer-by-layer printing; when printing the first few layers, the printing depth is controlled so that it is printed into the seven-core optical fiber (6); S4: After printing is completed, the fiber tip is rinsed with acetone and isopropyl alcohol in sequence to completely remove the uncured photoresist, obtaining the final temperature sensor probe based on 3D printed fiber tip integrated FPI.

8. Temperature sensor, characterized in that: include: A wide-spectrum light source (1), a spectrometer (2), an optical fiber circulator (3), and a temperature sensor probe, wherein the temperature sensor probe is the temperature sensor probe according to any one of claims 1 to 7; the wide-spectrum light source (1) is connected to the first port of the optical fiber circulator (3), the spectrometer (2) adopts the optical spectrum demodulator, the spectrometer (2) is connected to the third port of the optical fiber circulator (3), and the optical fiber cable (4) in the temperature sensor probe is connected to the second port of the optical fiber circulator (3); In the temperature sensor, a wide-spectrum light source (1) is used to emit a broadband spectrum, and an optical fiber circulator (3) is used to isolate the broadband spectrum signal emitted by the wide-spectrum light source (1) and the composite envelope interference spectrum signal output by the sensor probe. The broadband spectrum emitted by the wide-spectrum light source (1) is input into the temperature sensor probe through the optical fiber circulator (3) and then through the seven-core fan-in fan-out device (5). The seven-core optical fiber (6) in the temperature sensor probe forms a vernier unit with the first cavity as a polymer Fabry-Perot cavity and the second cavity as an open Fabry-Perot cavity. The broadband spectrum input into the sensor probe generates a double-beam interference under the action of the vernier unit to form an interference spectrum. The interference spectrum is transmitted to the seven-core fan-in fan-out device (5) via the optical fiber cable (4), and then transmitted back to the spectrometer (2) through the optical fiber circulator (3) to achieve spectral demodulation.

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