FPI optical fiber temperature sensor based on PDMS filling capillary glass tube

Abstract

The invention provides an FPI optical fiber temperature sensor based on a PDMS filled capillary glass tube, which comprises a capillary glass tube, one end of the capillary glass tube is filled with cured polydimethylsiloxane, the other end of the capillary glass tube is inserted with a single-mode optical fiber, in the capillary glass tube, the end surface of the polydimethylsiloxane is a concave surface, and the end surface of the single-mode optical fiber is a convex surface. The end face of the single-mode optical fiber is a plane, the end face of the polydimethylsiloxane and the end face of the single-mode optical fiber form two reflecting faces of the Fabry-Perot cavity, light input is carried out in the single-mode optical fiber, and light output is carried out in the Fabry-Perot cavity. Displacement of the end face of the polydimethylsiloxane as a function of a temperature change causes an interference wavelength in the Fabry-Perot cavity to be adjusted to map the temperature change. The invention provides the PDMS-filled SCT-based micro-air cavity FPI optical fiber sensor which is simple in structure, easy to manufacture, low in cost, small in size and ultrahigh in precision, and is used for high-precision temperature detection.

Description

Technical Field

[0001] This invention relates to the technical field of fiber optic temperature sensing, and more specifically, to an FPI fiber optic temperature sensor based on a PDMS-filled capillary glass tube. Background Technology

[0002] Temperature detection is widely needed in metallurgy, energy, chemical and other fields, and is a very basic and important measurement. In many application environments, such as petrochemical transportation pipelines, power switchgear and transformers, temperature monitoring is very important, and temperature sensors are required to have high insulation, corrosion resistance, electromagnetic interference resistance, high performance and small size.

[0003] Traditional electronic thermometers struggle to meet these requirements, while fiber optic temperature sensors have garnered significant attention due to their unique advantages, such as high sensitivity, small size, fast response, low cost, strong resistance to electromagnetic interference, and durability in harsh environments.

[0004] Among various fiber optic temperature sensors, fiber optic Fabry-Perot interferometer (FPI) temperature sensors have been widely studied by researchers due to their advantages such as good stability, convenient measurement, compact structure, and diverse and flexible manufacturing methods.

[0005] However, the temperature sensitivity of all-fiber FP temperature sensors is limited by the low thermo-optic coefficient and expansion coefficient of the fiber itself. Therefore, temperature-sensitive materials are usually introduced into the sensor to improve the sensitivity.

[0006] However, fiber optic FPI sensors based on temperature-sensitive materials have the potential for high-sensitivity temperature detection. Therefore, it is necessary to design an ultra-high sensitivity FPI fiber optic temperature sensor based on temperature-sensitive materials. Summary of the Invention

[0007] In view of this, the present invention proposes an FPI fiber optic temperature sensor based on PDMS-filled capillary glass tube to solve the problems existing in the prior art.

[0008] To achieve the above objectives, this invention proposes an FPI fiber optic temperature sensor based on a PDMS-filled capillary glass tube, comprising:

[0009] A capillary glass tube, wherein one end of the capillary glass tube is filled with cured polydimethylsiloxane, and the other end of the capillary glass tube is inserted with a single-mode optical fiber. An air microcavity is formed between the adjacent end faces of the single-mode optical fiber and the polydimethylsiloxane in the capillary glass tube. This air microcavity is a Fabry-Perot cavity. In the air microcavity, the end face of the polydimethylsiloxane is concave, and the end face of the single-mode optical fiber is planar. The end faces of the polydimethylsiloxane and the single-mode optical fiber form two reflecting surfaces of the Fabry-Perot cavity. Light is input into the single-mode optical fiber. In the Fabry-Perot cavity, the end face of the polydimethylsiloxane shifts according to temperature changes, causing the interference wavelength in the Fabry-Perot cavity to adjust to reflect the temperature change.

[0010] Optionally, the length of the air microcavity is determined based on the free spectral range of the Fabry-Perot cavity.

[0011] Optionally, once the cavity length of the air microcavity is determined, it can be encapsulated on one side of the single-mode fiber using ultraviolet colloid.

[0012] Optionally, it also includes a temperature detection experimental device, wherein the temperature detection experimental device includes a light source, a spectrometer, a constant temperature chamber, a thermometer, and a computer; the thermometer and the Fabry-Perot cavity are arranged in the constant temperature chamber, wherein the light source provides light input to the single-mode fiber, the spectrometer collects and analyzes the output light of the Fabry-Perot cavity, and the computer converts the analysis results from the spectrometer into temperature data, and compares and detects the temperature data with the thermometer data.

[0013] Optionally, the corresponding preparation steps include:

[0014] The single-mode optical fiber and capillary glass tube are cut;

[0015] Polydimethylsiloxane was prepared and then drawn into the capillary glass tube for curing.

[0016] Connect the single-mode fiber to the spectrometer, insert the single-mode fiber into the end of the capillary glass tube away from the polydimethylsiloxane, adjust the insertion depth of the single-mode fiber, and observe the spectrum collected by the spectrometer. Based on the collected spectrum, fix and encapsulate the single-mode fiber with UV adhesive.

[0017] Optionally, the capillary glass tube is a quartz capillary glass tube.

[0018] Optionally, polydimethylsiloxane is prepared by crosslinking a prepolymer and a curing agent at a weight ratio of 10:1.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This sensor exhibits a sensitivity more than 120 times higher than that of traditional all-fiber FPI temperature sensors and the most common FBG fiber temperature sensors (approximately 10 pm / ℃). Compared to other PDMS cavity-based fiber FPI temperature sensors, it overcomes the offsetting effect of wavelength shift caused by the increase in cavity length and decrease in refractive index due to PDMS expansion, resulting in a significant improvement in sensitivity. While existing temperature sensors also achieve considerable sensitivity, their fabrication processes require delicate and complex operations, increasing the difficulty of fabrication. The sensor proposed in this invention has a very simple fabrication process, which is conducive to mass production. In addition, the materials used in this sensor are very inexpensive, and expensive equipment is not required in the probe production process, resulting in a significant cost-effectiveness. Since the cavity length of the sensing cavity can be flexibly adjusted, the sensitivity and detection range of the sensor can be customized according to actual needs in the future. Attached Figure Description

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings:

[0022] Figure 1 This is a schematic diagram of the micro-air cavity FPI fiber optic temperature sensor structure based on PDMS-filled SCT in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of a micro-air cavity FPI fiber optic temperature sensor based on PDMS-filled SCT in an embodiment of the present invention.

[0024] Figure 3 This is a spectral diagram of a micro-air cavity FPI fiber optic temperature sensor based on PDMS-filled SCT in an embodiment of the present invention.

[0025] Figure 4 The diagram below is a schematic diagram of the device in an embodiment of the present invention; wherein, (a) is an image of the FP air microcavity of the sensor under a microscope; and (b) is a schematic diagram of the temperature detection experimental device.

[0026] Figure 5 The image shows the spectrum of the probe at different temperatures in the temperature measurement experiment of this invention.

[0027] Figure 6 This is a temperature sensitivity fitting graph from the temperature measurement experiment in this embodiment of the invention;

[0028] Figure 7 This is a schematic diagram illustrating the repeatability of probe temperature measurement in an embodiment of the present invention;

[0029] Figure 8This is a schematic diagram of the hysteresis characteristics of the probe temperature measurement in an embodiment of the present invention;

[0030] Figure 9 This is a schematic diagram illustrating the stability of probe temperature measurement time in an embodiment of the present invention;

[0031] Figure 10 This is a diagram of the equipment used for flat end face cutting in an embodiment of the present invention. Detailed Implementation

[0032] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] This embodiment presents an ultra-high sensitivity, simple fabrication, and low-cost FPI fiber temperature sensor based on a PDMS-filled capillary glass tube. The sensor is constructed by filling one end of a 150µm inner diameter quartz capillary glass tube with polydimethylsiloxane (PDMS) and curing it, while inserting a single-mode fiber (SMF) into the other end, forming a microcavity with controllable length. Due to the relatively long PDMS filling length, the two reflecting surfaces of the FP are mainly formed by the SMF end face and its proximal polymer concave surface. When the temperature rises, the PDMS expands, causing the length of the FP cavity to decrease, resulting in a blue shift of the interference wavelength in the FP spectrum. Experimental results show that the sensor has a temperature sensitivity as high as -12.678nm / ℃ in the range of 23℃-26℃, a limit of measurement (LOD) of 0.00158℃, and exhibits good linearity, stability, reversibility, and repeatability. The sensitivity of this sensor is more than 120 times higher than that of traditional all-fiber cavity FP temperature sensors (approximately 10pm / ℃). This structure boasts superior performance, is simple to prepare, and is inexpensive, making it a promising candidate for applications in pharmaceutical transportation, biological culture, and other fields requiring ultra-high precision temperature control.

[0034] The ultra-high sensitivity FPI fiber temperature sensor based on PDMS-filled capillary glass tube proposed above consists of single-mode fiber (SMF), capillary glass tube (SCT), and polydimethylsiloxane (PDMS). A section of polydimethylsiloxane is filled into the capillary glass tube using capillary action, and a single-mode fiber is inserted at the other end as an introduction fiber.

[0035] Specifically, the air microcavity, composed of a concave polydimethylsiloxane surface and the end face of a single-mode optical fiber, can have its cavity length L precisely controlled by a micro-displacement platform. After selecting a suitable cavity length, it is encapsulated with UV adhesive.

[0036] Specifically, polydimethylsiloxane is a thermosensitive material that is easy to prepare, inexpensive, and has good thermo-optical properties. It exhibits a high coefficient of thermal expansion (9.6 x 10⁻⁶) within a temperature range of -55°C to 220°C. -4 / ℃) and thermo-optical system (-5.0x10 -4 ( / °C), which is very suitable for temperature sensing.

[0037] Specifically, UV adhesive is a heat-resistant (-50-120°C) and moisture-resistant ultraviolet curing agent. Encapsulation with it can increase the stability of sensing performance.

[0038] Specifically, the working principle of the aforementioned sensor is that when light passes through a single-mode optical fiber, part of it is reflected by the end face of the single-mode optical fiber, and the other part of the light passes through the air cavity to reach the polydimethylsiloxane interface and is reflected, resulting in multiple internal reflections.

[0039] The light beams reflected from the single-mode fiber-air interface and the air-polydimethylsiloxane interface form an optical path difference (OPD), and interference occurs when the optical path differences are superimposed. Since the filling length of polydimethylsiloxane is relatively long, only the reflection at the polydimethylsiloxane interface near the single-mode fiber needs to be considered.

[0040] Since optical fibers and polydimethylsiloxane have relatively low reflectivity, the effects of multiple reflections can be ignored, simplifying the system to a two-beam interference.

[0041] Specifically, the temperature detection experimental device consists of a C+L band light source (1520nm-1620nm), an OSA spectrometer with a wavelength resolution of 0.02nm, a constant temperature chamber, a thermometer, a computer (equipped with spectrometer software), and a temperature sensing probe.

[0042] Specifically, the fabrication process of the temperature sensor probe structure includes:

[0043] 1) Cut one end of a standard single-mode fiber (Corning SMF-28, 8um / 125um) and both ends of a section of quartz capillary glass tube (150um / 300um) with a fiber optic cleaver to make the end face as flat as possible. The capillary glass tube section is about 18mm long.

[0044] 2) Polydimethylsiloxane is prepared by crosslinking prepolymer and curing agent at a weight ratio of 10:1. A capillary glass tube is inserted into polydimethylsiloxane and drawn in about 2 mm through capillary action, and then cured at room temperature for 24 h.

[0045] 3) Connect the single-mode fiber to the spectrometer, insert it from the other end of the capillary glass tube and observe the spectrum. After obtaining a spectrum with good contrast, fix and encapsulate the single-mode fiber with UV glue to obtain the final sensing probe.

[0046] The ultra-high sensitivity FPI fiber optic temperature sensor based on PDMS-filled capillary glass tubes is described in detail below:

[0047] To overcome the problems existing in related technologies, this invention aims to propose a micro-air cavity FPI fiber optic sensor based on PDMS-filled SCT that is simple in structure, easy to manufacture, low in cost, small in size, and ultra-high in precision. It is used for high-precision temperature detection, offsetting the negative impact of the decrease in refractive index during PDMS expansion on sensitivity, and improving detection sensitivity.

[0048] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0049] The structural schematic diagram of the reported fiber optic temperature sensor is shown below. Figure 1 As shown, the sensor consists of a single-mode fiber (SMF), a capillary glass tube (SCT), and polydimethylsiloxane (PDMS). A section of PDMS is filled into the capillary glass tube using capillary action, and the other end is inserted into the SCF as the feed fiber. The FPI cavity is an air microcavity composed of the concave surface of the PDMS and the end face of the single-mode fiber. The cavity length L can be precisely controlled using a micro-displacement platform, and after selecting a suitable cavity length, it is encapsulated with UV adhesive. Polydimethylsiloxane is an easily prepared, inexpensive, and thermo-optically effective thermosensitive material with a high coefficient of thermal expansion (9.6 x 10⁻⁶) over a temperature range of -55°C to 220°C. -4 / ℃) and thermo-optical system (-5.0x10 -4 ( / °C), making it ideal for temperature sensing. UV adhesive is a UV curing agent that is resistant to temperature (-50-120°C) and moisture; encapsulation with it can increase the stability of sensing performance.

[0050] The length of the air cavity is controlled by a micro-displacement platform, primarily determined by the insertion length of the single-mode fiber. The micro-displacement platform controls and cuts the single-mode fiber to insert it into the capillary glass tube. Related equipment is involved. Figure 10 As shown, the process involves using wire strippers to strip the fiber sheath. A fiber clamp is then used to secure the fiber. Tension is applied to the single-mode fiber using pulleys and weights. The single-mode fiber (SMF) is then precisely positioned on a micro-displacement platform. Finally, the fiber is cut with a cleaver to obtain a flat end face.

[0051] Furthermore, the working principle of the sensor is as follows: Figure 2 As shown. When light passes through a single-mode fiber, part of it is reflected by the end face of the single-mode fiber, and the other part passes through the air cavity to the polydimethylsiloxane interface and is reflected, resulting in multiple internal reflections. The beams reflected from the single-mode fiber-air interface and the air-polydimethylsiloxane interface form an optical path difference (OPD), and interference is generated after the optical path differences are superimposed. The filling length of polydimethylsiloxane is relatively long, so only the reflection at the polydimethylsiloxane interface near the single-mode fiber needs to be considered. Since the reflectivity of the fiber and polydimethylsiloxane is relatively low, the influence of multiple reflections can be ignored, and the system can be simplified to a two-beam interference. The reflected light intensity I of FP is shown in formula (1):

[0052] (1)

[0053] Where I1 is the light intensity reflected from the single-mode fiber-air interface; I2 is the light intensity reflected from the air-polydimethylsiloxane interface; and δ represents the phase difference. =4ΠnL / λ is the OPD of the two beams, L is the cavity length of the FP air microcavity, n is the refractive index of air, λ is the wavelength of the incident light, Π represents the proportionality coefficient of the wavelength-phase relationship, and π. When the wavelength satisfies 4ΠnL / λ=2Πm (m is any integer), resonance occurs. Therefore, the resonant wavelength λm and the free spectral range (FSR) are as shown in formulas (2) and (3):

[0054] λm=2nL / m (2)

[0055] FSR=(λmλm+1) / 2L (3)

[0056] As shown in equation (2), the position of the resonant wavelength is affected by the FP cavity length and refractive index. When the temperature around the sensor increases, the PDMS expands due to heat, increasing its volume radially along the capillary. Since the single-mode fiber is fixed, the FP air microcavity is compressed, and the change in air refractive index is negligible, resulting in a shorter cavity length and a blue shift in the resonant wavelength. The interference spectrum of the fabricated sensor at room temperature is as follows: Figure 3 As shown, the sensor has a large FSR (27.44 nm) and a significant extinction ratio (10 dB), which is beneficial for spectral demodulation. The theoretical L can be calculated as 44.76 μm according to formula (3). The actual cavity length observed by optical microscopy is 45 μm, which is basically consistent with the theoretical calculation result.

[0057] Furthermore, the overall temperature detection device, such as Figure 4 As shown, Figure 4 (a) in the figure refers to the sensor mentioned above, and the temperature detection experimental apparatus is as follows: Figure 4As shown in (b), the system consists of a C+L band light source (1520nm-1620nm), an OSA spectrometer with a wavelength resolution of 0.02 nm, a constant temperature chamber, a thermometer, a computer (equipped with spectrometer software), and a temperature sensing probe. The temperature is set in the constant temperature chamber, which is then heated. When the temperature displayed on the thermometer inside the chamber remains almost constant, the spectrum is recorded.

[0058] Further, the fabrication process of this probe structure is as follows: 1) One end of a standard single-mode fiber (Corning SMF-28, 8um / 125um) and both ends of a section of quartz capillary glass tube (150um / 300um) are cut with a fiber optic cleaver to make the end faces as flat as possible. The capillary glass tube section is approximately 18 mm long; 2) Polydimethylsiloxane is prepared by crosslinking a prepolymer and a curing agent at a weight ratio of 10:1. The capillary glass tube is inserted into the polydimethylsiloxane and drawn in approximately 2 mm through capillary action, and then cured at room temperature for 24 hours; 3) The single-mode fiber is connected to a spectrometer. The spectrum is observed by inserting the capillary glass tube from the other end. After obtaining a spectrum with clear peaks and valleys and good contrast, the single-mode fiber is fixed and encapsulated with UV glue to obtain the final sensing probe. A photograph of the FP air microcavity sensing area under a microscope is shown below. Figure 2 As shown in (a), the length of the FP air cavity is 45 μm.

[0059] Furthermore, the temperature response of the probe was investigated. As the temperature gradually increased from 23.399℃ to 25.385℃, the sensor's spectrum underwent a blue shift. A linear fit was performed on the trough wavelength and temperature, and the resulting fitting graph is shown below. Figures 5-6 As shown, within this measurement range, the sensor exhibits a temperature sensitivity as high as -12.678 nm / ℃, with R² = 0.9991, demonstrating good linearity. Since the spectrometer has a resolution of 0.02 nm, the probe's temperature measurement limit can be as low as 0.00158℃.

[0060] Furthermore, heating and cooling tests were conducted on the sensor probe to investigate its hysteresis characteristics. Linear fitting was performed on the heating and cooling processes separately, and the results are as follows: Figure 7 As shown, finally, the temperature of the constant temperature chamber was set to 23.644℃ for time measurement stability test, and continuous monitoring was carried out for 39 minutes.

[0061] To explore the potential of this temperature sensing probe in practical applications, other characteristics of the probe were tested, including measurement repeatability, reversibility, and stability. Repeatability is crucial for practical applications; it is the most fundamental parameter of a sensor, referring to the consistency of results obtained from the same measurements under identical experimental conditions. Three temperature sensing experiments were conducted on the probe under the same conditions, and the results are as follows: Figure 7As shown, the temperature sensitivities of the three measurements were -12.73 nm / ℃, -12.776 nm / ℃, and -12.679 nm / ℃, respectively, indicating that the temperature sensitivities were very close. Furthermore, the data points from the three experiments largely overlapped, with a maximum relative deviation of less than 2%, demonstrating that the sensor exhibits good repeatability.

[0062] Heating and cooling tests were conducted on the sensor probe to investigate its hysteresis characteristics. Linear fitting was performed on the heating and cooling processes separately, and the results are as follows. Figure 8 As shown, the linear fitting curves for the heating and cooling processes basically overlap. The temperature sensitivity during the heating process is -12.678 nm / ℃, and the temperature sensitivity during the cooling process is -12.615 nm / ℃. These results indicate that the sensitivities during the heating and cooling processes are approximately the same, thus demonstrating that the sensor exhibits good hysteresis characteristics.

[0063] Finally, the temperature of the constant temperature chamber was set to 23.644℃ for time-measured stability testing, and continuous monitoring was performed for 39 minutes.

[0064] At this time, the monitored interference wavelength is 1585.504 nm. Due to the working mechanism of the constant temperature chamber, such as... Figure 9 As shown, the temperature in the constant temperature chamber fluctuates around 23.644℃. Ignoring the temperature drift factor, the temperature sensor probe exhibits good time measurement stability. In summary, besides its extremely high sensitivity and detection accuracy, this sensor also demonstrates good repeatability, reversibility, and temperature measurement stability, which is beneficial for practical applications.

[0065] The sensor we report is compared with existing sensors, as shown in Table 1. The sensitivity of this sensor is more than 120 times higher than that of traditional all-fiber FPI temperature sensors and the most common FBG fiber temperature sensors (approximately 10 pm / ℃). Compared to other PDMS cavity-based fiber FPI temperature sensors, it overcomes the offsetting effect of wavelength shift caused by the increase in cavity length and decrease in refractive index due to PDMS expansion, resulting in a significant improvement in sensitivity. While some existing structures also achieve considerable sensitivity, their fabrication processes require delicate and complex operations, increasing the difficulty of fabrication. The sensor we report, however, has a very simple fabrication process, which is conducive to mass production. In addition, the materials used in this sensor are very inexpensive, and expensive equipment is not required in the probe production process, resulting in a significant cost-effectiveness. Since the cavity length of the sensing cavity can be flexibly adjusted, the sensitivity and detection range of the sensor can be customized according to actual needs.

[0066] Table 1

[0067] structure Sensitivity Fiber Bragg gratings (FBGs) coated with PDMS 42 pm / ℃ Fiber Bragg gratings (FBGs) coated with polytetrafluoroethylene (PTFE). 300 pm / ℃ All-Fiber Fabry-Perot Interferometer (FPI) 9.42 pm / ℃ Fabry-Perot Interferometer Based on PDMS Cavity 2.2 nm / ℃ Microfiber Fabry-Perot interferometers (FPIs) encapsulated in PDMS 11.86 nm / ℃ Hollow capillary Fabry-Perot interferometer (FPI) filled with a very small amount of PDMS 2.62 nm / ℃ Fabry-Perot interferometer (FPI) based on PDMS-filled SCT 12.678 nm / °C

[0068] In summary, this invention proposes a micro-air cavity FPI fiber optic temperature sensor based on a PDMS-filled SCT, enabling high-precision temperature detection. This sensor only requires inserting an SMF (Superficial Microfiber) into an SCT containing PDMS to form an air microcavity, making its fabrication simple and inexpensive. Experiments show that the sensor can reach a temperature of -12.678 nm / ℃, with a LOD (Level of Detection) of 0.00158℃, and exhibits good linearity, stability, reversibility, and repeatability. In the future, the sensitivity and detection range of this temperature sensor can be customized by adjusting the cavity length. Due to its ultra-high detection accuracy, ease of manufacture, simple structure, low cost, and small size, this probe is expected to find practical applications in medical transportation, biological culture, and other fields requiring ultra-high temperature control precision.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An FPI fiber optic temperature sensor based on a PDMS-filled capillary glass tube, characterized in that, include: A capillary glass tube, wherein one end of the capillary glass tube is filled with cured polydimethylsiloxane, and the other end of the capillary glass tube is inserted with a single-mode optical fiber. An air microcavity is formed between the adjacent end faces of the single-mode optical fiber and the polydimethylsiloxane in the capillary glass tube. This air microcavity is a Fabry-Perot cavity. In the air microcavity, the end face of the polydimethylsiloxane is concave, and the end face of the single-mode optical fiber is planar. The end faces of the polydimethylsiloxane and the single-mode optical fiber form two reflecting surfaces of the Fabry-Perot cavity. Light is input into the single-mode optical fiber. In the Fabry-Perot cavity, the end face of the polydimethylsiloxane shifts according to temperature changes, causing the interference wavelength in the Fabry-Perot cavity to adjust to reflect the temperature change.

2. The temperature sensor according to claim 1, characterized in that, The length of the air microcavity is determined based on the free spectral range of the Fabry-Perot cavity.

3. The temperature sensor according to claim 2, characterized in that, Once the cavity length of the air microcavity is determined, it is encapsulated on one side of the single-mode fiber using ultraviolet colloid.

4. The temperature sensor according to claim 1, characterized in that, It also includes a temperature detection experimental device, wherein the temperature detection experimental device includes a light source, a spectrum analyzer, a constant temperature chamber, a thermometer, and a computer; the thermometer and the Fabry-Perot cavity are set in the constant temperature chamber, wherein the light source provides light input to the single-mode fiber, the spectrum analyzer collects and analyzes the output light of the Fabry-Perot cavity, and the computer converts the analysis results from the spectrum analyzer into temperature data, and compares and detects the temperature data with the data from the thermometer.

5. The temperature sensor according to claim 1, characterized in that, The corresponding preparation steps include: The single-mode optical fiber and capillary glass tube are cut; Polydimethylsiloxane was prepared and then drawn into the capillary glass tube for curing. Connect the single-mode fiber to the spectrometer, insert the single-mode fiber into the end of the capillary glass tube away from the polydimethylsiloxane, adjust the insertion depth of the single-mode fiber, and observe the spectrum collected by the spectrometer. Based on the collected spectrum, fix and encapsulate the single-mode fiber with UV adhesive.

6. The temperature sensor according to claim 1, characterized in that, The capillary glass tube is a quartz capillary glass tube.

7. The temperature sensor according to claim 1, characterized in that, Polydimethylsiloxane is prepared by crosslinking a prepolymer and a curing agent at a weight ratio of 10:1.

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