Cryogenic Temperature Sensor Based on Fresnel Reflection From a Polymer-Coated Facet of Optical Fiber

We report a fiber-optic sensor based on Fresnel reflection for real-time monitoring of cryogenic temperatures. Coating highly thermo-sensitive polymers on the facet of optical fiber, we obtain average measurement sensitivity 0.04 dB/K in temperature range of 90–298 K. We show theoretical background of polymer’s thermo-optic response and the experimental results performed with two kinds of coating polymers, epoxy resin, and polymethyl methacrylate. The experimental results confirm the suitability for cryogenic temperature sensing applications, such as superconducting lines and magnets with simple and cost-effective sensor structure and signal processing.