The negative impact of anode resistance on SiPMs as VLC receivers

Presented at PRIME 2022, the 17th Conference on Ph.D. Research in Microelectronics and Electronics. It was my first in-person conference, after the earlier ones ran under COVID restrictions, and I really enjoyed it. I met some fantastic people and saw how others use photodetection in their own fields.

Abstract

The process used to detect individual photons in passively quenched Silicon Photomultipliers (SiPMs) creates a nonlinear response. A model is presented to show this nonlinearity is an unavoidable consequence of microcells recharging after a detection. However, results are presented which show the nonlinearity is increased by the inclusion of an anode readout resistor. Removal of this resistor improves ambient light performance of communication links by a factor of 1.9 under 300 mW/m $^2$ of total 405 nm irradiance.

Key Findings

The paper looks at how anode resistance affects a SiPM’s fast output. With ambient light reduced by filters, lower anode resistance gives a shorter recharge time, more bandwidth, better saturation performance and a higher time-averaged PDE. The same board design lets several SiPMs be combined into a larger device without increasing the output pulse width. The non-linearity caused by microcells recharging remains, and it matters for both OOK and OFDM. Understanding it is the route to pre- and post-equalisation that keeps high-speed VLC working in difficult lighting.