An optical fiber temperature sensor based on fluorescence intensity ratio in Er3+/Yb3+ co-doped Gd2O3 phosphors

A simple optical fiber temperature sensing system based on up-conversion luminescence of Er3+/Yb3+ co-doped Gd2O3 phosphors is proposed and demonstrated for the first time. The Gd2O3: 1 mol% Er3+, 1 mol% Yb3+ phosphors are synthesized by traditional sol-gel method. A sandwich structure fabricated by two fiber connectors, one of which is deposited the fluorescent material cured with ultraviolet adhesive on the surface, is used as the sensing probe. Temperature measurement is achieved using the two green emissions, generated by Gd2O3: 1 mol% Er3+, 1 mol% Yb3+ phosphors, based on the fluorescence intensity ratio (FIR) technique. When the Gd2O3: 1 mol% Er3+, 1 mol% Yb3+ phosphor is excited by the 980 nm laser with the output power of 73 mW, the intense green emissions are observed and change with temperature. The temperature sensing characteristics are experimentally studied in the temperature range from 253 to 413 K, with the maximum absolute sensitivity of 4.15% K−1 at 413 K, the maximum relative sensitivity of 2.28% K−1 at 253 K and the maximum relative error of 0.43%. The proposed optical fiber temperature sensor not only offers excellent reversibility and stability, but also significantly contributes to accurate and remote temperature measurement in harsh environments.