Optical Fiber Temperature Sensor Based On NaYF₄:Er³⁺/Yb³⁺ Nano-fluorescent Material And Its Temperature Characteristics

Optical fiber fluorescent temperature sensing is a new type of sensing technology based on optical fiber and fluorescent temperature measurement.Compared with traditional temperature sensing,it has the advantages of high sensitivity and resolution,strong anti-electromagnetic interference and long service life.It has strong application value in aerospace,environmental monitoring,human health monitoring and other fields.The work of this thesis is to fill the Na YF₄:Er³⁺/Yb³⁺nano fluorescent material into the air hole of the hollow-core fiber and encapsulate it into a new type of optical fiber fluorescence temperature sensor.The temperature measurement is achieved by measuring the fluorescence peak intensity and the fluorescence peak intensity ratio and other parameters.The temperature characteristics of the sensor are analyzed.The specific research content and results are as follows:1.Nano-sized Na YF₄:Er³⁺/Yb³⁺fluorescent materials were prepared by thermal co-precipitation method,and a set of variable temperature fluorescence spectroscopy experimental system was built to study the fluorescence temperature characteristics of Na YF₄:Er³⁺/Yb³⁺nano-fluorescent materials.2.Proposed a multimode-fiber hollow-core-fiber multimode-fiber（MMF-HCF-MMF,MHM）structure,and constructed the MHM sensing structure model.The optical field distribution of the MHM sensing structure was simulated by Rsoft software,and the influence of the length,inner diameter of the hollow core fiber and the refractive index of the filling material on the optical coupling efficiency of the MHM sensing structure was analyzed.3.A method for preparing liquid core optical fiber is proposed.The capillary effect of the hole at the rear end of the hollow core fiber is used to fill the Na YF₄:Er³⁺/Yb³⁺nano fluorescent solution,and the hole of the hollow core fiber is encapsulated to form a liquid core fiber.The prepared liquid core fiber was subjected to a variable temperature experiment,and the temperature sensitivity of the ratio of the fluorescence peak intensity and the peak intensity of the thermal coupling energy level was measured to be 111.78 counts/K and 0.00636/K,respectively.4.In order to overcome the easy flow characteristics of the rare earth nano fluorescent solution,a solid core fiber filled with Na YF₄:Er³⁺/Yb³⁺nano fluorescent solution and PDMS glue was produced,which reduces the difficulty of the sensor preparation process and further improves the stability.The prepared solid-core optical fiber temperature sensor was subjected to variable temperature experiments,and the temperature sensitivity of the fluorescence peak intensity and peak intensity ratio was83.4 counts/K and 0.0067/K,respectively,and its linearity was significantly higher than that of the temperature sensor filled with fluorescent nanoparticle aqueous solution,Repeatability and stability have also been greatly improved.The optical fiber fluorescence temperature sensor based on Na YF₄:Er³⁺/Yb³⁺nano fluorescent solution and PDMS glue mixed and filled is easier to mass produce.