Sapphire fiber Bragg gratings for high temperature and dynamic temperature diagnostics

•Temperature sensing using Sapphire fiber Bragg gratings up to 1900 °C is shown.•For temperatures >1500 °C a temperature resolution of ±1 K was achieved.•High speed temperature monitoring at a rate of 20 Hz was demonstrated.•The temperature distribution in an inductive furnace at 1500 °C was determined.

This paper reports on a new kind of temperature sensor operating over an extremely large temperature range at high monitoring speeds. The sensor utilizes fiber Bragg gratings inscribed into multimode single crystalline Sapphire fibers, basically providing temperature control via an optical reflection signal. The gratings operate up to 1900 °C, which is the highest temperature determined using Bragg grating so far, and allow signal processing with a temperature resolution better than ±2 K. The sensor uniquely provides fast dynamic temperature monitoring at an unprecedented rate of 20 Hz. Overall, fiber Bragg grating inside Sapphire fibers provide a new base for precise high-temperature measurement with key advantages such as signal multiplexing, large temperature bandwidth and insensitivity to electromagnetic fields.