Sensitive, high-speed thermometry using optical fibers

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Abstract
The use of aluminum-jacketed optical fibers for sensitive, high-speed thermometry is demonstrated. Sensitivity of the fiber to thermal variations is observed at frequencies up to 30 kHz. Although the presence of configuration-dependent mechanical resonances between 10 and 22 kHz precludes a simple analysis of the thermal response at these frequencies, the response between 5 Hz and 4 kHz is in reasonable agreement with analytic results. Assuming a minimum-detectable phase change of 10−6 rad, the observed sensitivity at 4 kHz corresponds to a minimum-detectable temperature variation of 1 μK for a 1-cm length of fiber. This performance represents orders-of-magnitude improvement in both sensitivity and frequency response relative to those of commercially available temperature-measuring systems.