As a basic physical parameter for high-frequency measurement,temperature is of great guiding significance in the fields of production,medicine,national defense,and scientific research.The modern and complicated monitoring environment requires the temperature measurement system to have the characteristics of high accuracy,fast response,safety,and use in special environment.Compared with traditional temperature sensors,fiber-optic temperature sensing systems have gradually entered into the field of scientific researchers with the advantages of optical signal transmission,anti-electromagnetic interference and long-distance transmission.Among them,the optical fiber temperature sensing system based on fluorescence intensity ratio technology(FIR)uses the fluorescence intensity area ratio between the thermal coupling energy levels of rare earth ions to establish a correspondence relationship with temperature,which can reduce system errors due to power fluctuations and improve temperature measurement accuracy,which has become a common technique for temperature sensing.So far,due to the nature of optical fibers,fiber optic temperature sensing systems commonly use glass fibers as temperature probes,and relatively few studies have been conducted on fluorescent powder materials as temperature probes.Therefore,this paper is based on the fluorescence intensity ratio(FIR)technology,using phosphor powder temperature-sensitive materials as the research object,regulating the spectral performance and temperature sensing performance,solving the technical difficulties of coupling with the optical fiber,evaluating the temperature measurement capability of the optical fiber temperature measurement system and exploring potential commercial prospects for fiber optic temperature measurement systems.A pure hexagonal NaYF4 phosphor co-doped with Er3+/Yb3+ions was synthesized by hydrothermal method.By monitoring the green up-conversion luminescence of the NaYF4 phosphor,the up-conversion luminescence mechanism of the Er3+-Yb3+ion pair in the phosphor was analyzed according to the correspondence between the up-conversion luminous intensity and the pump power of the excitation light source.An all-fiber temperature sensing system was established using NaYF4phosphor as a temperature probe.In the temperature range of 258-423 K,real-time up-conversion spectra were recorded to investigate the dependence of FIR value on temperature.The experimental results show that when the temperature is 258 K,the maximum relative temperature sensitivity of the system is 1.68%K-1,the absolute error is±1 K,the temperature uncertainty is 0.187 K,and the relative standard deviation is 0.133%.The high sensitivity and small temperature uncertainty prove the reliability of the optical fiber temperature sensor,which shows that this optical fiber temperature sensor based on FIR technology has certain practical value in actual temperature measurement.Er3+/Yb3+co-doped Sr Mo O4 phosphors were prepared by solid-phase method.The effects of heterovalent metal ion doping(Li+and Ga3+ions)on the crystal structure and growth process of Sr Mo O4 phosphors were studied in detail.The effects of heterovalent ion doping on the photoluminescence properties of Eu3+ions and the local symmetry of rare earth were analyzed.The measurement results show that the lifetime of Eu3+ions is prolonged,and the changes in photoluminescence and relative intensity are significantly enhanced,which indicates that the local symmetry around Eu3+ions is greatly reduced due to the doping of isovalent metal ions.Designing doped heterovalent metal ions reduces the local symmetry of Er3+ions to obtain temperature-sensitive materials with high spectral intensity and high sensitivity.When the excitation power is 30 m W,the green up-conversion luminous intensity of Er3+ions is increased by 255 times,and the temperature sensitivity is also significantly improved.Sr Mo O4:Er3+/Yb3+/Li+/Ga3+phosphor was selected as the temperature measurement probe of the all-fiber temperature measurement system,which achieved a high absolute sensitivity(0.0166 K-1)at 423 K.The temperature measurement capability of the fiber optic temperature measurement system was evaluated to obtain small temperature uncertainty(0.091 K),absolute error(0.5-0.3 K),and good repeatability(<1%).Excellent results prove that the platform can find potential applications in harsh environments and small spaces. |