Psuedo-Heterodyne, Optical-Fiber Thermometer Using Fabry-Perot Interferometer

A fiber optic Fabry-Perot interferometer composed of a certain length of a single mode fiber the surfaces of both ends of which are optically polished and coated with a reflecting film is utilized to measure the temperature.[1] The intensity of the output light transmitted through the Fabry-Perot interferometer alternately becomes strong and weak every time the fiber length varies λ /2 due to some cause such as temperature change. In Ref. 2, the analogue measuring method of output light intensity for this type of thermometer is demonstrated. It achieves high temperature sensitivity.