Fluorescence intensity ratio and whispering gallery mode techniques in optical temperature sensors: comparative study

The thermal sensing capabilities of different morphologies (microsphere, fiber, and bulk glass) of an Er3+ doped oxyfluoride glass were characterized in order to determine the most suitable material to be developed as a temperature sensor. For the microsphere and fiber, the displacements of the whispering gallery mode peaks were correlated with the temperature change. The thermal expansion and thermo-optic coefficient of the bulk glass were measured for the numerical simulations of the WGM shift with temperature. On the other hand, a fluorescence intensity ratio technique was used to estimate the temperature of the bulk glass. In order to compare the sensor performance of each sample, the relative sensitivity and temperature uncertainty were determined.