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Sapphire fiber based high temperature extensometer
New sapphire fiber based sensor structures for high temperature strain measurement are
proposed and studied in this report. The self-mixing interferometry has been studied and
tested. The advantage of this technique is the source coherence insensitivity and direction
distinguishment capability. Fringes of the self-mixing interferometer built with standard
multimode fiber and sapphire fiber were observed. The application of this technique to
static strain rneasurement seems difficult to stabilize, whereas its implementation to acoustic
sensing with single-mode fiber coil as the sensing component will be very interesting. The
approach by Moire interferometry and equal-path coherence matching interferometer are
two promising methods for high temperature displacement measurement. The advantages
of the Moire interferometer are source coherence independence and large measurement
range. The advantage of coherence matching absolute interferometer is its simplicity in
sensor structure. The structures of coherence matching methods and multiplexing
techniques are generalized. From this research, we can conclude that the sapphire fiber
based high temperature extensometer may be realized by different methods.