We present a novel model for calculating the bit error rate in optical communication systems in the case of on–off keying intensity modulation and optically preamplified direct detection. The model accounts for the intersymbol interference and is based on the Laguerre photon-count probability distribution predicted by photodetection theory. For a non-return-to-zero modulation format an accurate value of the sensitivity for a quantum-limited receiver of 33.9 photons/bit is obtained.
© 2004 Optical Society of America
Paolo Martelli, *Silvia M. Pietralunga, Dario Nicodemi, and Mario Martinelli*, "Accurate sensitivity in optically preamplified direct detection," Opt. Lett. 29, 1473-1475 (2004)