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

TL;DR

This work demonstrates a tunable Power over Fiber (PoF) system that feeds a single optical power line into an Optical Power Converter (OPC) and a tunable DC-DC boost stage to power SiPMs and cold electronics at cryogenic temperatures, down to 4.6 K. By adjusting laser input power, the SiPM bias can be tuned without additional fibers, achieving comparable signal-to-noise performance to copper cabling while enabling operation in harsh cryogenic and high-voltage environments. The study confirms OPC operation at 4.6 K with about 29% efficiency and shows that the Cryo-PoF approach can support scalable photodetector arrays (e.g., 20–80 SiPMs) with tunable bias and acceptable noise levels, broadening PoF applicability beyond LN2 and into demanding cryogenic applications.

Abstract

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.

Figures (15)

• Figure 1: Left up: sketch of the laser characterization test stand at room temperature to evaluate $P_{ref}$. Left bottom: sketch of the laser characterization test stand at room temperature to evaluate $P_{fiber}$. Right: power loss evaluated for each optical fiber tested using eq. \ref{['eq::fiber']}. The red triangles correspond to Fiber I, the blue squares to Fiber II and the green dots to Fiber III.
• Figure 2: Linear relationship between the input voltage and the output laser power.
• Figure 3: Laser power stability at fixed input power of P$_{0}$$\sim$ 1 W. $(P_{max}-P_{min})/P_{0} \sim 5.7\%$, with an average deviation from P$_{0}$ of = 17.1 mW, where P$_i$ is the power measured at time $i$. Excluding the first 30 minutes of operation, during which higher instability is observed, we obtain $(P_{max}-P_{min})/P_{0} \sim 0.96\%$ and $\langle P_{0} - P_i \rangle = 15.9$ mW (see text for details) cryo_pof_creta.
• Figure 4: IV curves for the OPC at room (top) and liquid nitrogen temperature (77 K -- bottom).
• Figure 5: Maximum current delivered by the OPC at different laser powers (top) and OPC efficiency as a function of the laser power (bottom). Error bars are included but hidden by the data points. In each plot, the red dots correspond to measurements at room temperature, while blue dots correspond to measurements at 77 K.