Ultrasensitive Cryogenic Temperature Sensor Based on a Metalized Optical Fiber Fabry-Perot Interferometer

Cryogenic technologies are becoming essential in future applications in aerospace, quantum computing, cryogenic computing, and superconducting research. A highly sensitive temperature sensor is critical for such cryogenic applications. In this paper, we propose an extrinsic Fabry–Perot interferometer (EFPI) for cryogenic temperature measurement, leveraging the high thermal deformation of the copper sleeve to overcome the sensitivity drop issue in temperatures below 50 K for conventional cryogenic temperature sensors. Experimental results exhibit a temperature sensitivity of 2.836 nm/K throughout a temperature range of 5 K-50 K with a 15.82 μm long EFPI cavity, which is over three orders higher than the recently reported metal-coated FBG. The high sensitivity holds for the entire temperature range from 5 K to 295 K with excellent sensing repeatability. Our device, featuring a compact structure, and capability for multiplexing, is with great promise in cryogenic applications.