Cryogenic temperature 3D mapping via a distributed temperature sensor with centimeter resolution

We conduct 3D mapping of cryogenic temperatures via a Raman-based distributed temperature sensor, employing standard telecom single-mode fibers and polarization-independent superconducting nanowire single photon detectors (SNSPDs). By coiling a test fiber around various stages of a liquid helium cooled cryostat, our device demonstrates a lower temperature sensing limit of (48 ± 2) K, below the nitrogen boiling point. This achievement is made possible by the low dark count rates of SNSPDs, as validated by theoretical simulations. Furthermore, we utilize our device to map cryogenic temperatures on the 350 cm² surface of a specially designed hollow cylindrical aluminum sample, accommodating approximately 2 m of standard single-mode optical fiber. During nitrogen cooling, we monitor the temporal evolution of the spatially dependent temperature gradient on the metallic sample with a temporal sampling down to one minute. Fiber-based distributed temperature sensing with centimetric spatial resolution can be effectively applied for 3D mapping at cryogenic temperatures of superconducting, quantum computing and aerospace instrumentation.