Rare-Earth Optical Temperature Sensors

A recently developed type of fiber-optic temperature sensor utilizes narrow-band near-infrared radiation emitted by rare-earth ions. These sensors are suitable for use in harsh environments at temperatures above the maximum (1,700 °C) that Pt/Rh thermocouples can withstand. The maximum operating temperature for these optical temperature sensors can equal or exceed 2,000 °C, the exact values depending on the choice of fiber-optic and rare-earth-containing radiative materials. The minimum temperature measurable by use of a sensor of this type, related to the minimum detectable radiation, has been found to be ≈700 K (≈427 °C).