Performance analysis of photon-limited PPM-FSO communications: SER under afterpulsing effect in practical...

The optical communication system using photon-counting receivers has attracted considerable attention as it enables high-speed data transmission at extremely low average signal power. This study develops a comprehensive analytical framework for modeling the statistical behavior of practical photon-counting receivers in pulse position modulation (PPM)-free-space optical (FSO) communications. Our analysis specifically explored the impacts of the dead time, lack of photon-number-resolving capability, and non-Markovian afterpulsing effect on photon counts and yielded a closed-form approximation for the photon count probability distribution. The accuracy of the proposed model is verified against exact results obtained from Monte Carlo simulations. Furthermore, based on the proposed statistical model and the soft-decision decoding, we provide a closed-form expression for the symbol error rate of high-order PPM signals. This work provides a reliable analytical model for evaluating the performance of photon-limited PPM-FSO systems employing practical receivers.