A Roadmap for Gigabit to Terabit Optical Wireless Communications Receivers

Published in MDPI Sensors. It builds on the SimSPAD paper, using Monte Carlo simulation to ask what future SiPM receivers could offer.

Abstract

Silicon photomultipliers’ relatively large areas and ability to detect single photons make them attractive as receivers for optical wireless communications. In this paper, the relative importance of the non-linearity and width of SiPMs’ fast output in their performance in receivers is investigated using Monte Carlo simulations. Using these results, the performances of receivers containing different SiPMs are estimated. This is followed by a discussion of the potential performances of arrays of existing SiPMs. Finally, the possible dramatic improvements in performance that could be achieved by using two stacked integrated circuits are highlighted.

Key Findings

SiPMs with narrow output pulses are the better choice for VLC and optical wireless (OWC) receivers. The irradiance needed for a given BER rises quickly once the bit time is shorter than the output pulse width. Non-linearity still matters, and a SiPM should run at less than 40% of its maximum count rate. A larger SiPM needs less irradiance for a given data rate, but a larger device of the same type also has wider pulses. Using diodes to add the outputs of parallel SiPMs avoids that trade-off, but would be expensive at scale. Moving the transmitter from 405 nm to 850 nm brings only small benefits. Stacked arrays of single-photon avalanche diodes (SPADs) could outperform existing fiber-optic receivers at 25.78 Gbps, and go faster still.