Preparation and use method of portable down-conversion tellurate optical fiber temperature sensor

Abstract

The invention belongs to the field of fluorescent optical fiber sensors, and particularly relates to a preparation and use method of a portable down-conversion tellurate optical fiber temperature sensor. At present, most (doped) tellurate optical fibers based on the fluorescence intensity ratio technology are upconversion materials and are difficult to couple with multimode optical fibers, the sensitivity needs to be improved when the (doped) tellurate optical fibers serve as temperature sensors, and laser exciters large in weight and size are needed. Aiming at the problems in the prior art, TeO2, ZnO, Bi2O3 and Er2O3 are adopted to prepare the down-conversion rare earth doped tellurate optical fiber, and the coupling performance is good when the down-conversion rare earth doped tellurate optical fiber is welded with a multimode optical fiber; the prepared temperature sensor is high in sensitivity and good in stability; and an ultraviolet lamp is adopted for pumping, so that temperature monitoring is facilitated.

Description

Technical Field

[0001] The invention belongs to the field of fluorescent optical fiber sensors, and in particular relates to a preparation and use method of a portable down-conversion tellurite optical fiber temperature sensor. Background Art

[0002] As a special matrix material, tellurite fiber has the characteristics of low phonon energy, low melting point, high rare earth solubility and high upconversion efficiency, making it an ideal choice for upconversion fluorescent materials and can be used as a sensitive element for temperature sensors. However, the upconversion tellurite fiber (and doped tellurite fiber) temperature sensors based on fluorescence intensity ratio technology and their manufacturing methods still have some shortcomings: (1) Coupling difficulties: Due to the differences in melting temperature, thermal expansion coefficient and diameter of (doped) tellurite fiber and multimode fiber, it is difficult to accurately couple them; inaccurate coupling will lead to greater insertion loss and increase the occurrence of reflection and scattering phenomena; (2) Sensitivity: The sensitivity of temperature sensors based on (doped) tellurite fiber upconversion fluorescent materials has encountered a bottleneck and basically remains at 0.012K. -1 There is still much room for improvement in sensitivity, and a high-sensitivity fiber-optic temperature sensor is urgently needed; (3) Current up-conversion-based temperature sensors require excitation from a 980nm semiconductor laser, which is heavy and bulky, and is difficult to carry for temperature monitoring. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a method for preparing and using a portable down-conversion tellurite optical fiber temperature sensor, which has good coupling, simple structure and high sensitivity.

[0004] The method for preparing the portable down-conversion tellurite optical fiber temperature sensor of the present invention comprises the following steps:

[0005] Step 1: Preparation of rare earth doped tellurite optical fiber liquid

[0006] The optical fiber mixture is heated to obtain a molten, clear, light red optical fiber liquid, and after shaking, a rare earth-doped tellurite optical fiber liquid is obtained; the heating temperature is 950° C., and the heating time is 75 min; the optical fiber mixture includes the following components and molar ratios: TeO2:ZnO:Bi2O3:Er2O3=84.8:10:5:0.2.

[0007] Step 2: Preparation of rare earth doped tellurite optical fiber preform

[0008] The clarified rare earth-doped tellurite optical fiber liquid obtained in step 1 is poured into a copper cylindrical mold for annealing at a temperature of 325° C. for a time of 210 min to obtain a rare earth-doped tellurite optical fiber preform;

[0009] The copper cylindrical mold is preheated in advance at a temperature of 325° C., which is consistent with the annealing temperature. The preheating temperature should be lower than the glass transition temperature of the optical fiber preform. The preheating operation is performed in a muffle furnace.

[0010] Step 3: Prepare the Tellurite Fiber Temperature Sensor

[0011] (1) Drawing rare earth-doped tellurite optical fiber: After a rare earth-doped tellurite optical fiber preform rod with a smooth surface is drawn into an optical fiber with a diameter of 130 μm, a rare earth-doped tellurite optical fiber is obtained;

[0012] The rare earth doped tellurite optical fiber is a down-conversion fluorescent material and has no cladding structure;

[0013] (2) Fusion splicing of rare earth doped tellurite fiber and multimode fiber:

[0014] The rare earth-doped tellurite optical fiber obtained in step 3(1) is cut into 3 cm long bare optical fibers, and coupled with multimode optical fibers to obtain the portable down-conversion tellurite optical fiber temperature sensor of the present invention;

[0015] The coupling refers to the welding of the rare earth doped tellurite bare optical fiber and the multimode optical fiber, and the welding conditions are as follows: the welding discharge time is 200ms, the welding discharge intensity is 20bit, the pre-melting time is 160ms, and the secondary discharge time is 0ms; the welding end face is not at the discharge center, and the motor distance on the multimode optical fiber side is set to 3600-3800nm, so that the welding end face is away from the multimode optical fiber end and close to the rare earth doped tellurate optical fiber end, and the welding end faces of the multimode optical fiber and the rare earth doped tellurate optical fiber are as close as possible and try to be on the same axis.

[0016] The method for using the portable down-conversion tellurite optical fiber temperature sensor of the present invention comprises the following contents:

[0017] The rare earth doped tellurite fiber in the tellurite fiber temperature sensor is used as the receiving end to receive the temperature signal. At the same time, the receiving end is subjected to 23.65mW / cm 2 The multimode optical fiber end of the temperature sensor is connected to a spectrometer, and the other end of the spectrometer is connected to a computer, so that the temperature signal can be converted into spectral data output through the rare earth doped tellurite optical fiber temperature sensor prepared by the present invention.

[0018] The temperature to be measured can be calculated according to the following formula: T = -(FIR-A) / B;

[0019] Where T represents the temperature to be measured, FIR represents the fluorescence intensity ratio at 530nm and 545nm; A = 4.20324, which represents the parameter related to the material performance of the temperature sensor; B = 0.01778℃-1 , indicating the sensitivity of the temperature sensor.

[0020] The rare earth-doped tellurite optical fiber prepared by the present invention is a bare optical fiber, which does not have the core and cladding structure of a traditional optical fiber, has a wider operating wavelength range and a higher optical signal transmission efficiency, and enhances the advantages of a temperature sensor; after the optical fiber preform is drawn into an optical fiber of a size that meets the requirements, no annealing treatment is required, and the process method is simple; the optical fiber is a down-conversion fluorescent material, and an ultraviolet lamp with higher energy can be used to excite the optical fiber to generate pure green down-conversion fluorescence for temperature measurement, thereby improving the fluorescence conversion efficiency of the optical fiber and further improving the sensitivity of the temperature sensor; and the ultraviolet light source is small in size, light in weight, and easy to carry, successfully solving the problem that a 980nm semiconductor laser exciter is difficult to carry.

[0021] The rare earth doped tellurite optical fiber receiving the temperature signal in the temperature sensor prepared by the present invention has good coupling performance. After the optical fiber is fused with the multimode optical fiber by manual cleaning discharge of the fusion splicer, the loss is small, the sensitivity is high, and the repeated use effect is good, which can meet the temperature monitoring needs in complex environments. The temperature sensor is a down-conversion fluorescent material, which has broad application prospects in the fields of electromagnetic interference, biomedicine, material science, environmental monitoring, etc. It uses the fluorescence intensity ratio technology of down-conversion fluorescence generated by the thermal coupling energy level of rare earth elements. By measuring its fluorescence intensity ratio at different temperatures and establishing the relationship between temperature and fluorescence intensity ratio, it can accurately demodulate the temperature change in the environment, realize accurate monitoring and analysis of temperature changes in complex environments, and provide strong support for scientific research and technological innovation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an end face view of the rare earth-doped tellurite optical fiber prepared in Example 1;

[0023] Figure 2 This is a schematic diagram of the structure of the temperature sensor prepared in Example 1;

[0024] Figure 3 This is a physical schematic diagram of the relative position relationship between the two optical fibers and the electrode center after fusion splicing in a fusion splicer. The left side is a multimode optical fiber, the right side is a rare-earth-doped tellurite optical fiber, the dotted line in the middle is the electrode center, and the white light on the right is the fusion end face of the two optical fibers;

[0025] Figure 4 A graph showing the fluorescence spectrum of the temperature sensor prepared in Example 1 changing with temperature in the wavelength range of 500-580 nm (the axis of 0.0 to 1.0 represents the normalized relative intensity of the fluorescence spectrum at different temperatures);

[0026] Figure 5 A graph showing the relationship between the temperature measured by the temperature sensor prepared in Example 1 and the fluorescence intensity ratio corresponding to the temperature;

[0027] Figure 6 This is a graph showing the stability measurement results of the temperature sensor prepared in Example 1 at 30°C to 90°C. The fluorescence intensity ratio at wavelengths of 530nm and 545nm when a certain temperature is tested for the first time is recorded as #1. The same temperature is tested 7 times, and so on. The fluorescence intensity ratios of the repeated tests are recorded as #2 to #7, respectively. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be further described below in conjunction with the embodiments of the present invention and the accompanying drawings.

[0029] Example 1

[0030] Step 1: Preparation of rare earth doped tellurite optical fiber liquid

[0031] At room temperature, weigh TeO2, ZnO, Bi2O3, and Er2O3 in a molar ratio of 84.8:10:5:0.2, with a total sample of 0.5 mol, mix them in a grinding mortar and grind them manually for 30 minutes, use a medicine spoon to take an appropriate amount of the glass mixture and put it into a corundum crucible prepared in advance, cover the crucible, and then transfer it to a muffle furnace and heat it for 75 minutes at a heating temperature of 950°C. In this way, a molten light red rare earth doped tellurite optical fiber liquid is obtained. Open the muffle furnace, remove the crucible cover with a crucible tongs, take out the corundum crucible, and shake it well to obtain the clarified rare earth doped tellurite optical fiber liquid described in the present invention.

[0032] Step 2: Preparation of rare earth doped tellurite optical fiber preform

[0033] The clarified optical fiber liquid in a molten state is poured into a copper cylindrical mold for annealing treatment, thereby removing the stress generated during the cooling process of the tellurite optical fiber liquid and forming an optical fiber preform, and then the furnace heating switch is turned off to allow the glass in the muffle furnace to cool naturally to room temperature, thereby obtaining the rare earth doped tellurite optical fiber preform of the present invention. The copper cylindrical mold is preheated in advance, and the preheating temperature is 325°C, which is consistent with the annealing temperature, and the preheating temperature should be ensured to be lower than the glass transition temperature of the optical fiber preform, and the preheating operation is performed in the muffle furnace.

[0034] Step 3: Prepare the Tellurite Fiber Temperature Sensor

[0035] (1) Drawing rare earth-doped tellurite optical fiber: Use fine sandpaper to polish the surface of the rare earth-doped tellurite optical fiber preform rod to make it smooth, put the preform rod into the optical fiber drawing tower, and gradually heat and pull it with a graphite furnace. By controlling the drawing speed and tension, the preform rod is gradually elongated while maintaining the uniformity and stability of the material to form the desired shape and size. Figure 1The coreless rare earth doped tellurite optical fiber with a diameter of 130 μm is shown. The drawn rare earth doped tellurite optical fiber is cut into bare optical fibers with a length of 3 cm by a cutting device, and its end face is shaped and polished by grinding and polishing processes so as to better connect with multimode optical fibers and transmit optical signals.

[0036] (2) Fusion splicing of rare earth doped tellurite fiber and multimode fiber: The rare earth doped tellurite fiber and multimode fiber (cladding diameter 125 μm, core diameter 62.5 μm) are manually coupled using the clean discharge of the fusion splicer to obtain the present invention. Figure 2 The portable down-conversion tellurite fiber temperature sensor shown. The program settings of the fusion splicer are as follows: the fusion cleaning discharge time is 200ms, the fusion cleaning discharge intensity is 20bit, the pre-melting time is 160ms, and the secondary discharge time is 0ms. Since the melting temperature of the coreless rare earth doped tellurite fiber is around 300°C, its position needs to be manually adjusted to keep its end face away from the discharge center, and the motor distance on the multimode fiber side is controlled to be 3740nm, so that the fusion end faces of the two optical fibers are as close as possible and away from the multimode fiber end and close to the rare earth doped tellurite fiber end, and try to be on the same axis to ensure that the two can contact and reach the best optimization state before manual fusion cleaning discharge coupling. The relative positions of the multimode fiber, electrode, and rare earth doped tellurate fiber during fusion splicing according to the above method are as follows Figure 3 shown.

[0037] The method of using the portable down-conversion tellurite optical fiber temperature sensor of the present invention is as follows:

[0038] When measuring temperature, the multimode fiber end of the temperature sensor prepared above was connected to a small ocean fiber spectrometer, and the rare earth doped tellurite fiber was used as the receiving end to receive the temperature signal. At the same time, the receiving end was heated with 23.65 mW / cm 2 The power of the UV lamp pump forms a temperature sensor-UV lamp-spectrometer signal collection system. A small marine fiber optic spectrometer is used to collect the spectral data of the temperature sensor, and then output it to the computer connected to the other end of the spectrometer. In the test temperature range of 30℃ to 90℃, green down-conversion fluorescence with a certain intensity is generated at wavelengths centered at 530nm and 545nm. The fluorescence spectrum of the temperature sensor changes with temperature as shown in the following figure: Figure 4 As shown in the figure, the functional relationship between the measured temperature and the fluorescence intensity ratio is fitted as follows: Figure 5As shown, T = -(FIR-4.20324) / 0.01778 (FIR is the ratio of the fluorescence intensity at 530nm to the fluorescence intensity at 545nm, and the slope of the fitting curve 0.01778 is the sensitivity of the sensor). Therefore, in actual temperature measurement, the corresponding temperature to be measured can be demodulated by the fluorescence intensity ratio according to this functional relationship to achieve temperature measurement. Each temperature measurement point is repeatedly monitored 7 times with a temperature sensor, and the fluorescence intensity ratio after each test is calculated. The overlap rate of the fluorescence intensity ratio when the same temperature is repeatedly tested is observed to test the repeatability of the temperature sensor, and the stability of the temperature sensor is judged based on the repeatability. Figure 6 As shown, the fluorescence intensity ratio coincidence rate is good when repeated tests are performed at different temperatures to be measured, so the temperature sensor has good stability when measuring temperature.

Claims

1. A method for preparing a portable down-conversion tellurite optical fiber temperature sensor, characterized in that: The following steps are involved: Step 1: Preparation of rare earth doped tellurite optical fiber liquid The optical fiber mixture is heated to obtain a molten optical fiber liquid, that is, a rare earth doped tellurite optical fiber liquid; the optical fiber mixture comprises the following components: TeO2, ZnO, Bi2O3, and Er2O3; Step 2: Preparation of rare earth doped tellurite optical fiber preform The rare earth-doped tellurite optical fiber liquid obtained in step 1 is poured into a copper cylindrical mold for annealing to obtain a rare earth-doped tellurite optical fiber preform; Step 3: Prepare the Tellurite Fiber Temperature Sensor (1) Drawing rare earth-doped tellurite optical fiber: Drawing the rare earth-doped tellurite optical fiber preform obtained in step 2 into an optical fiber with a diameter of 130 μm, that is, obtaining a rare earth-doped tellurite optical fiber; (2) Fusion splicing of rare earth doped tellurite fiber and multimode fiber: The rare earth doped tellurite fiber and the multimode fiber are fusion spliced ​​and coupled, and the fusion end face is not at the discharge center. The motor distance on the multimode fiber side is set to 3600-3800nm, so that the fusion end face is away from the multimode fiber end and close to the rare earth doped tellurite fiber end. After fusion coupling, the portable down-conversion tellurite fiber temperature sensor is obtained.

2. The method for preparing the portable down-conversion tellurite optical fiber temperature sensor according to claim 1, characterized in that: The welding conditions of step 3(2) are as follows: welding discharge time is 200ms, welding discharge intensity is 20bit, pre-melting time is 160ms, and secondary discharge time is 0ms.

3. The method for preparing the portable down-conversion tellurite optical fiber temperature sensor according to claim 1, characterized in that: The molar ratio of each component in the optical fiber mixture in step 1 is TeO2:ZnO:Bi2O3:Er2O3=84.8:10:5:0.

2.

4. The method for preparing the portable down-conversion tellurite optical fiber temperature sensor according to claim 1, characterized in that: The rare earth-doped tellurite optical fiber described in step 3(1) is a down-conversion fluorescent material with no cladding structure.

5. The method for preparing the portable down-conversion tellurite optical fiber temperature sensor according to claim 1, characterized in that: The heating temperature in step 1 is 950° C. and the heating time is 75 min. The annealing temperature in step 2 is 325° C. and the annealing time is 210 min.

6. The method for preparing the portable down-conversion tellurite optical fiber temperature sensor according to claim 1, characterized in that: The copper cylindrical mold described in step 2 is preheated before annealing, and the preheating temperature is the same as the annealing temperature and is lower than the glass transition temperature of the optical fiber preform.

7. A method for using the portable down-conversion tellurite optical fiber temperature sensor prepared according to claim 1, characterized in that: Includes the following: The rare earth doped tellurite optical fiber in the tellurite optical fiber temperature sensor is used as a receiving end to receive the temperature signal. At the same time, the receiving end is subjected to a 23.65 mW / cm 2 The temperature sensor is pumped by an ultraviolet lamp, the multimode optical fiber end of the temperature sensor is connected to a spectrometer, and the other end of the spectrometer is connected to a computer, so that the temperature signal can be converted into spectral data output through the rare earth doped tellurite optical fiber temperature sensor.

8. The method for using the portable down-conversion tellurite optical fiber temperature sensor according to claim 7, characterized in that: The temperature to be measured can be calculated according to the following formula: T = -(FIR-A) / B; Wherein, T represents the temperature to be measured, FIR represents the fluorescence intensity ratio at wavelengths of 530nm and 545nm; A = 4.20324, represents a parameter related to the material properties of the temperature sensor; B = 0.01778°C -1 , indicating the sensitivity of the temperature sensor.

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