A temperature sensor based on a Fabry-Perot interferometer addressed by low coherent light

This contribution describes an optical fibre temperature sensor which is robust enough for encapsulation into concrete used as a backfill in a landfill site. The sensing element is a Fabry-Perot cavity specifically designed to operate from 20 to 110°C with long lengths of optical fibre cable (up to 600 m). The sensor has been tested in a pressure chamber up to 10 bars and subjected to vibration in a 145 kV circuit breaker, it showed no degradation in performance. The sensor also demonstrated good stability during extended temperature cycling tests and during prolonged drift tests. The accuracy of the sensor is 2% with a resolution 0.5%. The optical support system for the sensor was a stabilised white light source and an optoelectronic detection system which optically compresses the modulated polychromatic signal representing it as a single number. This number is calibrated against temperature. The sensing system can support up to eight different or similar sensors simultaneously providing cost benefits for industrial applications