Sapphire-ruby single-crystal fibre for application in high temperature optical fibre thermometers: studies at temperatures up to 1500 °C

In this work, a study of a fibre optic ruby crystal probe exposed to high temperatures has been carried out for the first time, and annealing' effects have been considered and reported upon. The work has enabled the device to be studied at temperatures up to 1500°C to test its survivability': the results show that a single-crystal probe is able to operate continuously at temperatures up to 1400 C, and can reliably cover a wide temperature measurement range from 0°C to 1400 °C. Uncertainties in the measurement of, at worst, approximately ±7°C result after many hundreds of hours of temperature cycling of the probe.