Design Of Erbium Doped Fiber Fluorescence High Temperature Sensing System And Research On Its Characteristics

Temperature is a very important physical quantity in natural science and engineering technology.The application requirements of high temperature measurement technology in extreme environments such as metallurgical industry,aerospace field and fire temperature monitoring have attracted widespread attention in recent years.The fiber optic sensor has low cost,compact structure,corrosion resistance,strong antielectromagnetic interference ability,and shows unique advantages in the field of high temperature sensing.Among them,rare earth doped optical fiber has rich energy level transition channels,strong light absorption ability,high luminous efficiency,and high coupling with communication optical fiber.It has good application prospects in the field of fluorescence high temperature sensing.This paper aims to realize high temperature sensing and monitoring,and based on the theoretical basis of fluorescence temperature quenching.The sensing law of erbium-doped fiber in temperature testing is explored by building an erbium-doped fiber fluorescence high-temperature sensing system.The upper limit of temperature measurement of the sensing system was improved through the heat treatment.The temperature sensitivity was improved by using ytterbium ions as sensitizers.For the refinement and optimization of the sensing system,we introduced half-wave peak broadening model,centroid wavelength drift model and fluorescence intensity ratio data processing model.The main work and innovations of the paper are as follows:(1)The fluorescence emission mechanism of rare-earth doped fiber was elucidated.Taking erbium-doped fiber as the research object,based on the principle of temperature quenching,we designed a rare-earth erbiumdoped fiber fluorescence high-temperature sensing system.The sensor belongs to an all-fiber structure,has a compact structure and high coupling efficiency,can realize single-ended signal detection,and has a good application prospect in the field of high temperature detection.(2)The temperature measurement methods of fluorescence lifetime type and fluorescence intensity type were compared and analyzed.The down-conversion fluorescence spectrum generated by spontaneous emission of erbium-doped fiber was analyzed,and the influence of excitation light intensity,rare-earth doping concentration,and length of rare-earth-doped fiber on the fluorescence emission spectrum was explored,and the optimized design parameters of the sensing probe and the working parameters of the excitation light source were tested.The system can detect from 20°C to 800°C with a sensitivity of 1.4(d Bm nm)/°C,a repeatability error of 1.65%,and a high-temperature stability error of 0.64%.(3)The erbium-doped fiber temperature sensing system was optimized,and it is proposed to use the high-temperature annealing process to heat the erbium-doped fiber to increase the glass transition temperature of the erbium-doped fiber,in this way,the upper limit of temperature measurement of temperature sensor is increased by 300℃.Using the ytterbium as a sensitizer in the co-doped fiber,the temperature sensitivity of rare-earth-doped fiber was increased by 49.1%.Besides,the half-wave peak broadening model,the centroid wavelength shift model and the fluorescence intensity ratio data processing model were introduced.By comparing the temperature sensing performance under different models,the optimal analysis model under different working parameters of excitation light source was determined.