Temperature testing was carried out in a computer-controlled high-temperature oven in which the temperature was also monitored by a thermocouple. Both long-term temperature stability and temperature sensitivity were tested using a fiber optic interrogator to monitor sensors as they were cycled from room temperature to 1000 °C. The characteristic spectral dip wavelength shifts to the red by approximately 1.3 nm as the temperature is raised by 100 °C. The figure below shows the wavelength of the transmission dip of a chiral fiber versus temperature. The temperature was cycled five times from 700 °C to 1000 °C in the course of 24 hours, dwelling for 3 hours at these temperatures. The inset shows the temperature variations. As seen in the figure below, the HTS-1000 is capable of reliably measuring temperature up to 1000 °C with better than 1% accuracy. Drift measured over more than 1400 hours at 900 °C was 0.0005 °C/hr. The sensor is recommended for continuous monitoring to 900 °C with excursion to 1000 °C.