Optical fiber temperature sensor based on the upconversion fluorescence intensity ratio of NaYF₄:Er³⁺ excited by a 1525-nm laser

Remote and accurate temperature measurements in severe environments are of great importance. A 1525-nm wavelength located in the C band of optical fiber communication is used as a pumping light source for NaYF4:Er3+ phosphor possessing high upconversion efficiency. The upconversion luminescence characteristics were demonstrated in the temperature range of 160-400 K. Based on the thermal coupling energy level theory, the temperature measurement principle of the fluorescence intensity ratio is analyzed. The energy gap between the H-2(11/2) and (4)S(3/2 )energy levels of the Er3+ ions is approximately 787 cm(-1), which is appropriate for a temperature sensor. The experimental results indicated that its maximum temperature sensitivity was 0.00335 K-1. The proposed optical fiber temperature sensor indicates good hysteresis and repeatability and has potential applications in resisting electromagnetic interference and remote temperature sensing. (C) 2021 Optical Society of America