Fibre Tip Sensors for Localised Temperature Sensing Based on Rare Earth-Doped Glass Coatings

We report the development of a point temperature sensor, based on monitoring upconversion emission from erbium: ytterbium-doped tellurite coatings on the tips of optical fibres. The dip coating technique allows multiple sensors to be fabricated simultaneously, while confining the temperature-sensitive region to a localised region on the end-face of the fibre. The strong response of the rare earth ions to changing temperature allows a resolution of 0.1-0.3 degrees C to be recorded over the biologically relevant range of temperatures from 23-39 degrees C.