Effects of high temperature heat treatment on Nd3+-doped optical fibers for use in fluorescence intensity ratio based temperature sensing

The effect of very high-temperature exposure on the measurement properties of a fluorescence intensity ratio based optical fiber temperature sensor, using Nd[SUP3+]-doped fiber as the sensing material, has been investigated. The results obtained indicate that exposing the sensor material to 750°C for 100 h improves the accuracy of the fluorescence intensity ratio versus temperature characteristics from approximately 2.5 to approximately 1.3°C. Measurements of the refractive index profiles of Nd[SUP3+]-doped fiber samples prior to and after exposure to 750°C indicate that such exposure results in small but measurable changes in the refractive index profil