Sapphire optical fiber-based interferometer for high temperature environmental applications

Describes the development and testing of an extrinsic sapphire fiber-based sensor design intended for use in high-temperature environments, including the processing environments of advanced high-temperature materials and the in-situ operational environments of high-temperature adaptive materials and structures. In this sensor, a length of uncoated, unclad, single-crystal optical-quality multimode sapphire fiber is fusion-spliced to a single-mode silica fiber. Another sapphire fiber is placed end-to-end with the first sapphire fiber, so that the two adjacent end-faces of the sapphire fibers form a low-finesse Fabry-Perot cavity. This sensor is demonstrated to be useful for both strain and temperature measurement, with a 10-microstrain resolution over a range of 0-1150 microstrain, and a 3.5 degrees C temperature resolution over a range from 150 to 650 degrees C.