Earlier this year we reported a low-reflectivity fiber-optic Fabry-Perot interferometer utilizing a thermometer element.1 Temperature change is converted to electrical phase difference with this system. In Ref. 1, the pseudoheterodyne approach is applied to phase detection to get high sensitivity and eliminate output error stemming from the instability of the interference contrast factor caused by polarization fluctuation or light source intensity fluctuation. The sensed output is obtained in analog form, and the resolution in its present state allows better than 10−3oC.
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