Sapphire optical fiber blackbody cavity temperature measurement temperature sensor and preparation method thereof

Abstract

The invention provides a sapphire optical fiber blackbody cavity temperature measurement temperature sensor, which comprises a sapphire optical fiber temperature sensing probe, a thermal protection sleeve wrapping the outer surface of the sapphire optical fiber temperature sensing probe, an optical fiber patch cord, a photoelectric conversion device and a signal processing device, and is characterized in that the sapphire optical fiber temperature sensing probe comprises a blackbody cavity and a sapphire optical fiber with the length of L, the blackbody cavity wraps the outer surface of one end of the sapphire optical fiber, and the other end of the sapphire optical fiber is connected with one end of the optical fiber patch cord; the end face of the end, wrapping the blackbody cavity, of the sapphire optical fiber is a spherical end face, or the end, wrapping the blackbody cavity, of the sapphire optical fiber is provided with a drill hole Lgt with the length of L1 from the end face in the length direction of the sapphire optical fiber; l1gt; 0; the other end of the optical fiber patch cord is connected with the photoelectric conversion device, and the signal processing device processes electric signals converted by the photoelectric conversion device and calculates the measured temperature. The invention also provides a preparation method of the temperature sensor.

Description

Technical Field

[0001] The invention relates to optical fiber sensor technology, and in particular to a temperature sensor for measuring temperature in a sapphire optical fiber black body cavity and a preparation method thereof. Background Art

[0002] In the field of high temperature measurement, accurate and reliable temperature sensors are essential. Traditional temperature sensors, such as thermocouples and platinum resistance sensors, usually face some challenges in high temperature environments, including thermal drift of materials, insufficient stability, and long-term reliability issues in extreme environments. In order to improve the accuracy and reliability of temperature measurement, researchers and engineers are constantly exploring new sensor technologies.

[0003] As a high-performance optical fiber material, sapphire fiber is widely used in high-temperature measurement and sensor design under extreme conditions due to its excellent high-temperature stability, chemical inertness and radiation resistance. Sapphire fiber exhibits good optical properties and durability in high-temperature environments, but there are still certain challenges in practical applications. For example, existing sapphire fiber sensors may face the problem of insufficient temperature measurement accuracy, especially in high-temperature environments, where their optical response may be affected by a variety of factors.

[0004] The introduction of blackbody cavity design can significantly improve the accuracy and stability of temperature measurement. As an ideal radiation source, the blackbody cavity can provide uniform radiant heat, thereby effectively reducing the measurement error of optical fiber sensors in high temperature environments. It can realize the measurement of optical fiber sensors in ultra-high temperature environments such as high-temperature processes in aerospace. Among many factors, the intensity of the blackbody light source entering the fiber of the blackbody cavity is an important factor affecting the measurement accuracy and stability of the temperature sensor. Therefore, it is necessary to further study the intensity of the blackbody light source entering the fiber. Summary of the invention

[0005] The present invention provides a temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity and a preparation method thereof, which can increase the fiber-input intensity of a blackbody light source and further improve the temperature measurement performance of the temperature sensor.

[0006] In order to solve the above technical problems, the present invention provides a temperature sensor for measuring temperature in a sapphire fiber blackbody cavity, comprising a sapphire fiber temperature sensing probe, a heat protection sleeve wrapping the outer surface of the sapphire fiber temperature sensing probe, an optical fiber jumper, a photoelectric conversion device, and a signal processing device. The sapphire fiber temperature sensing probe comprises a blackbody cavity and a sapphire fiber with a length of L. The blackbody cavity wraps the outer surface of one end of the sapphire fiber, and the other end of the sapphire fiber is connected to one end of the optical fiber jumper; the end face of the end of the sapphire fiber wrapping the blackbody cavity is a spherical end face or the end of the sapphire fiber wrapping the blackbody cavity has a borehole with a length of L1 opened from the end face along the length direction of the sapphire fiber, L>L1>0;

[0007] The other end of the optical fiber jumper is connected to the photoelectric conversion device, and the signal processing device processes the electrical signal converted by the photoelectric conversion device to calculate the measured temperature.

[0008] In some embodiments, the first layer of the black body cavity material is metal molybdenum, and the second layer is boron nitride.

[0009] In some of the embodiments, the thickness of the metal molybdenum layer is 200-300 nm.

[0010] In some embodiments, the boron nitride layer has a thickness of 800-1000 nm.

[0011] In some embodiments, the diameter of the sapphire optical fiber is d, L1=10d.

[0012] In some of the embodiments, a fiber optic jumper base is further included, and the sapphire optical fiber is connected to the fiber optic jumper through the fiber optic jumper base.

[0013] In some embodiments, a stainless steel ring is further included, which is wrapped around one end of the thermal protection sleeve. The stainless steel ring is provided with a threaded hole, and the optical fiber jumper base is threadedly connected to the stainless steel ring to fix the optical fiber jumper base.

[0014] In some embodiments, the thermal protection sleeve is made of corundum.

[0015] In some embodiments, the outer surface of the portion of the sapphire optical fiber not wrapped in the black body cavity includes a thermal protection sleeve.

[0016] The present invention also provides a method for preparing the above-mentioned sapphire optical fiber blackbody cavity temperature sensor, which is characterized by comprising the following steps:

[0017] 1) Cut a section of sapphire optical fiber with a length of L, grind and polish both end surfaces of the sapphire optical fiber, and clean and dry the grinded sapphire optical fiber;

[0018] 2) heating one end of the sapphire optical fiber until it is melted, and then cooling it, so that the one end of the sapphire optical fiber is melted into a spherical shape or a hole with a length of L1 is processed along the length direction from the end face of the one end of the sapphire optical fiber;

[0019] 3) coating a black body cavity on the outer surface of one end of the sapphire optical fiber processed in step 2) by magnetron sputtering;

[0020] 4) Insert the sapphire optical fiber wrapped in the black body cavity into the heat protection sleeve, inject high temperature resistant glue at both ends and cure;

[0021] 5) Connect the other end of the sapphire optical fiber to the photoelectric conversion device through an optical fiber jumper, and connect the signal processing device to the photoelectric conversion device.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] By processing the end face of one end of the sapphire optical fiber, the end face of the end of the sapphire optical fiber wrapped in the black body cavity is made to be a spherical end face, or a hole with a length of L1 is opened from the end face along the length direction of the sapphire optical fiber at one end of the sapphire optical fiber wrapped in the black body cavity, L>L1>0, and the structure of the black body cavity on the outer surface of one end of the sapphire optical fiber is also changed accordingly, thereby improving the fiber-entry intensity of the black body light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a temperature sensor system according to Embodiment 1 of the present invention;

[0025] Figure 2 This is a component diagram of the back-end data processing circuit of the temperature sensor of Example 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the blackbody cavity structure with a spherical end surface in Example 1 of the present invention; Figure 4 This is a schematic diagram of back-end signal processing of a temperature sensor system according to Embodiment 1 of the present invention;

[0027] Figure 5 Comparison of the light receiving angles of flat-end optical fiber and spherical-end optical fiber;

[0028] Figure 6 This is a schematic diagram of a black body cavity structure with a drilled end face according to Embodiment 2 of the present invention;

[0029] Figure 7 Schematic diagram of incident light in a black body cavity with a drilled hole at the end face in Example 2.

[0030] 1. Black body cavity; 2. Sapphire optical fiber; 3. High temperature glue; 4. Heat protection sleeve; 5. Stainless steel ring 5; 6. SMA905 optical fiber jumper base; 7. SMA905 optical fiber jumper; 8. Photoelectric conversion device; 9. Signal processing device; 81. Photodiode; 82. Amplification-data acquisition circuit; 83. Circuit housing base; 84. Circuit housing. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "installed / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0034] Example 1

[0035] Reference Figure 1-Figure 5 , This embodiment provides a temperature sensor for measuring the temperature of a sapphire optical fiber 2 black body cavity 1, including a sapphire optical fiber 2 temperature sensing probe, a corundum heat protection sleeve 4, a stainless steel sleeve ring 5, an SMA905 optical fiber jumper base 6, an SMA905 optical fiber jumper 7, a photoelectric conversion device 8, and a signal processing device 9, wherein the signal processing device 9 is loaded with a host computer program;

[0036] The sapphire fiber 2 temperature sensing probe includes a sapphire fiber 2 with a length of L and a diameter of d, and a black body cavity 1 with a cavity length of 10d. The black body cavity 1 is wrapped around the outer surface of one end of the sapphire fiber 2. The outer surface of the part of the sapphire fiber 2 not wrapped with the black body cavity 1 includes a thermal protection sleeve 4, thereby exposing the black body cavity 1 outside the thermal protection sleeve, thereby improving the temperature measurement response speed.

[0037] like Figure 2As shown, the sapphire optical fiber 2 includes a black body cavity 1, one end of which is melted at high temperature and then cooled to form a spherical end face. The black body cavity 1 is sputtered with a first layer of metal molybdenum with a thickness of 200-300nm on one end of the spherical end face of the sapphire optical fiber 2 by a magnetron sputtering instrument using DC sputtering, and then a second layer of boron nitride with a thickness of 800-1000nm is sputtered to form a black body cavity 1 structure that matches the spherical end face.

[0038] Furthermore, the stainless steel ring 5 is wrapped around one end of the thermal protection sleeve 4, and a threaded hole is provided on the stainless steel ring 5. The SMA905 fiber optic jumper base 6 is threadedly connected to the stainless steel ring 5 to fix the SMA905 fiber optic jumper base 6. The other end of the sapphire optical fiber 2 is connected to the SMA905 fiber optic jumper 7 through the SMA905 fiber optic jumper base 6, and the other end of the SMA905 fiber optic jumper 7 is connected to the photoelectric conversion device 8.

[0039] like Figure 3 As shown, the photoelectric conversion device 8 includes a photodiode 81, an amplifier-data acquisition circuit 82, a circuit housing base 83, and a circuit housing 84. The photodiode 81 and the amplifier-data acquisition circuit 82 are arranged on the circuit housing base 83, and the circuit housing 84 covers the circuit housing base 83.

[0040] like Figure 4 As shown, the photodiode 81 receives the optical signal from the optical fiber jumper and converts it into a current signal and outputs it to the amplifier-data acquisition circuit 82. The amplifier-data acquisition circuit 82 amplifies the current signal and converts it into a voltage signal and outputs it to the signal processing device 9. The host computer program processes the electrical signal converted by the photoelectric conversion device 8 through the multi-order fitting equation: t = a0 + a1u + a2u 2 +a3u 3 +…+a n u n (a n is a constant, t is a temperature value, and u is a collected voltage value) the collected voltage value is resolved into a temperature value; by collecting multi-point temperature values ​​at a certain sampling frequency, a temperature change curve over time is drawn.

[0041] The amplification-data acquisition circuit 82 is divided into an amplification circuit and a data acquisition circuit. The input end of the amplification circuit is connected to the output end of the photoelectric conversion device 8, and is used to amplify the current signal and convert it into a voltage signal; the input end of the data acquisition circuit is connected to the output end of the amplification circuit, and collects the voltage signal;

[0042] The host computer program collects signals from the data acquisition circuit and performs data processing to complete the visualization and recording of temperature data.

[0043] In this embodiment, the end face of the sapphire optical fiber 2 wrapping one end of the black body cavity 1 is a spherical end face, such as Figure 5 The spherical end face shown has a larger receiving aperture angle compared to the ordinary flat end face sapphire optical fiber 2, and can receive light incident from more angles, thereby improving the intensity of the black body light source entering the fiber.

[0044] The method for preparing the temperature sensor for measuring the temperature of the black body cavity 1 using the sapphire optical fiber 2 of the present embodiment comprises the following steps:

[0045] 1) Use a diamond cutting knife to cut a section of sapphire optical fiber 2 with a length of L and a diameter of d, and use a grinding disc to grind and polish both end faces of the sapphire optical fiber 2; clean and dry the ground sapphire optical fiber 2;

[0046] 2) using a plasma arc to heat one end of the sapphire optical fiber 2 for a time t in an argon atmosphere until it melts, and then cooling it at room temperature in the argon atmosphere to melt one end of the sapphire optical fiber 2 into a spherical shape;

[0047] 3) Wrap the sapphire optical fiber 2 with tin foil, exposing a length of about 10 d, and put it into a magnetron sputtering instrument through an optical fiber clamping device, and use DC sputtering to sputter metal molybdenum with a thickness of 200-300 nm, and use radio frequency sputtering to sputter boron nitride with a thickness of 800-1000 nm;

[0048] 4) Insert the optical fiber with the sputtered black body cavity 1 into the heat protection sleeve 4, and inject a certain amount of high temperature glue 3 at both ends; apply high temperature glue 3 on the inner ring surface of the stainless steel sleeve 5, and put it on the end of the heat protection sleeve 4 without the black body cavity 1; fine-tune the position of the optical fiber, insert the end of the sapphire optical fiber 2 without the black body cavity 1 into the SMA905 optical fiber jumper base 6, and fix the SMA905 optical fiber jumper base 6 through the threaded hole on the stainless steel sleeve 5. Put the assembled period into a tube furnace for heating and curing, and take it out after curing;

[0049] 5) Connect the photoelectric conversion device 8 via the SMA905 optical fiber jumper 7, and connect the photoelectric conversion device 8 to the signal processing device 9 equipped with the host computer program via a USB data cable.

[0050] Wherein, the signal processing device 9 adopts a computer;

[0051] The temperature regime for curing in step 4 includes: a heating stage, a constant temperature stage, an in-furnace curing stage, and a natural cooling stage.

[0052] The temperature regime in the heating stage is: heating from room temperature to 100°C, and heating from 100°C to 150°C.

[0053] The temperature regime in the constant temperature stage is: 100° C. for 120 min, and 150° C. for 120 min.

[0054] Example 2

[0055] Reference Figure 6-7 As shown, the difference between this embodiment and embodiment 1 is that, in this embodiment, a hole of length L1 is opened from the end face of the sapphire fiber 2 wrapping the black body cavity 1 along the length direction of the sapphire fiber 2, where L1 = 10d. A first layer of metal molybdenum with a thickness of 200-300nm is sputtered on the outer surface of the end of the sapphire fiber 2 with a hole by a magnetron sputtering instrument, and then a second layer of boron nitride with a thickness of 800-1000nm is sputtered to form a black body cavity 1 structure that matches the end face of the hole. Figure 7 As shown, the drilled end face increases the absorption rate of the black body cavity 1 to light by causing the incident light to be absorbed-reflected-absorbed multiple times in the cavity, thereby increasing the intensity of the black body light source entering the fiber.

[0056] Meanwhile, the method for preparing the temperature sensor of this embodiment is different from that of Embodiment 1 in that step 2) is to use a femtosecond laser to process a hole with a length of 10d at one end of the sapphire optical fiber 2 along the length direction.

[0057] The above description is only a preferred specific implementation mode of the present invention, and does not limit the patent scope of the present invention. Any technical equivalent changes made using the contents of the present invention specification shall fall within the protection scope of the present invention.

Claims

1. A temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity, comprising a sapphire optical fiber temperature sensing probe, a heat protection sleeve wrapping the outer surface of the sapphire optical fiber temperature sensing probe, an optical fiber jumper, a photoelectric conversion device, and a signal processing device, characterized in that: The sapphire fiber temperature sensing probe comprises a black body cavity and a sapphire fiber with a length of L, wherein the black body cavity is wrapped around the outer surface of one end of the sapphire fiber, and the other end of the sapphire fiber is connected to one end of the fiber jumper; the end face of the end of the sapphire fiber wrapped around the black body cavity is a spherical end face, or the end of the sapphire fiber wrapped around the black body cavity is provided with a hole with a length of L1 from the end face along the length direction of the sapphire fiber, L>L1>0; The other end of the optical fiber jumper is connected to the photoelectric conversion device, and the signal processing device processes the electrical signal converted by the photoelectric conversion device to calculate the measured temperature.

2. The temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to claim 1, characterized in that: The first layer of the black body cavity material is metal molybdenum, and the second layer is boron nitride.

3. The temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to claim 2, characterized in that: The thickness of the metal molybdenum layer is 200-300nm.

4. The temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to claim 2, characterized in that: The boron nitride layer has a thickness of 800-1000 nm.

5. The temperature sensor for measuring temperature using a sapphire optical fiber blackbody cavity according to claim 1, characterized in that: The diameter of the sapphire optical fiber is d, L1=10d.

6. The temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to claim 1, characterized in that: It also includes an optical fiber jumper base, and the sapphire optical fiber is connected to the optical fiber jumper through the optical fiber jumper base.

7. The temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to claim 6, characterized in that , also includes a stainless steel ring, which is wrapped around one end of the thermal protection sleeve, and the stainless steel ring is provided with a threaded hole. The optical fiber jumper base is threadedly connected to the stainless steel ring to fix the optical fiber jumper base.

8. The temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to claim 1, characterized in that: The thermal protection sleeve is made of corundum.

9. The temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to claim 1, characterized in that: The outer surface of the sapphire optical fiber that is not wrapped in the black body cavity includes a thermal protection sleeve.

10. A method for preparing a temperature sensor for measuring temperature in a sapphire optical fiber blackbody cavity according to any one of claims 1 to 9, characterized in that: The following steps are involved: 1) Cut a section of sapphire optical fiber with a length of L, grind and polish both end surfaces of the sapphire optical fiber, and clean and dry the grinded sapphire optical fiber; 2) heating one end of the sapphire optical fiber until it is melted, and then cooling it, so that the one end of the sapphire optical fiber is melted into a spherical shape or a hole with a length of L1 is processed along the length direction from the end face of the one end of the sapphire optical fiber; 3) coating a black body cavity on the outer surface of one end of the sapphire optical fiber processed in step 2 by magnetron sputtering; 4) Insert the sapphire optical fiber wrapped in the black body cavity into the heat protection sleeve, inject high temperature resistant glue at both ends and cure; 5) Connect the other end of the sapphire optical fiber to the photoelectric conversion device through an optical fiber jumper, and connect the signal processing device to the photoelectric conversion device.

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