Investigation of coating impact on OFDR optical remote fiber-based sensors performances for their integration in high temperature and radiation environments

The response of optical frequency-domain reflectometry-based temperature sensors is here investigated in harsh environments (high temperature, high radiation dose) focusing the attention on the impact of the fiber coating on the sensor performances in such conditions. Our results demonstrate that the various coating types evolve differently under thermal treatment and/or radiations, resulting in a small (<5%) change in the temperature coefficient of the sensor. The identified procedure, consisting of a prethermal treatment of the fiber at its maximum coating operating temperature, is here verified up to 150 °C for higherature acrylate and up to 300 °C for polyamide coating. This method allows a stabilization of the temperature coefficients. Finally, we show that radiation does not affect scattering phenomenon, temperature coefficients ( $C-Ts$) remain identical within 1% fluctuations up to 10 MGy dose, and that permanent radiation-induced attenuation reached values stands for the development of high-spatial resolved distributed temperature for harsh environment associated with high temperature (up to 300 °C) and ionizing radiation up to the MGy dose level.