In this work, we have investigated the thermal properties and temperature sensing ability of an Er 3+ -doped fluorotellurite glass. From differential scanning calorimetry (DSC), and based on Hruby criterion, we have demonstrated that this glass is stable against crystallization in the range of temperature measurement. Using fluorescence intensity ratio (FIR), we have studied the photoluminescence behavior under down-conversion process in a large temperature range going from 83 to 833 K. We have shown that excitation wavelength has only slight effect on the sensing properties. As compared to others systems, we have proved that our glass has convenient thermal stability for fiber drawing, a maximum sensitivity of nearly 0.0072 K −1 at a temperature of 550 K and relatively low values for measurement resolution Δ T . Therefore, we may suggest that this glass is very suitable for optical temperature sensing. [ABSTRACT FROM AUTHOR]