Operation of a tunable Power over Fiber system for light detectors down to 4.6 K

The Power over Fiber (PoF) technology delivers electrical power by transmitting laser light through a lightweight, non-conductive fiber optic cable to a remote photovoltaic optical converter, which in turn powers sensors or electrical devices. Among the several advantages offered by this solution are spark-free operation in the presence of electric fields, elimination of noise induced by power lines, immunity to electromagnetic interference, and high robustness in hostile environments. The R\&D for the application of PoF in cryogenic environments started at FNAL and BNL (USA) in 2020 to power the Photon Detection System of the DUNE Vertical Drift module. This paper presents the results obtained in the framework of Cryo-PoF project where we developed a single-laser input line system to power an electronic amplifier and the photosensors at cryogenic temperatures. Unlike the DUNE solution, our system allows tuning of the photosensor bias by adjusting the input laser power. We also demonstrate the operation of the optical converter at temperatures down to 4.6 K, opening the possibility of using this technology in a much broader range of applications.