Effects of pointing errors and channel fading on the performance of free-space optically-preamplified PPM systems

In this paper, we study the impact of pointing errors and channel fading on the performance of free-space, optically preamplified, M-ary PPM systems. We consider two types of free-space optical links: (i) inter-satellite links and (ii) inter-building links. For inter-satellite links, only pointing error is considered. Starting with a Rayleigh model for the pointing error angle, we derive analytically the PDF for the pointing error parameter and for the signal-to-noise ratio (SNR) per bit. For inter-building links, we derive the density function for the SNR per bit that includes the combined effects of pointing errors and channel fading, assuming Rayleigh-distributed pointing errors. The channel fading models considered in this study for inter-buildings links are the log-normal and gamma-gamma models. We provide the error probability as a function of the average SNR per bit for both types of links. To cover systems with and without forward error correction, we compute the average SNR per bit required to achieve a bit error rate of 10(-4) and 10(-9). The corresponding power penalties are computed for different symbol sizes, scintillation indexes, and pointing jitters. Copyright (c) 2016 John Wiley & Sons, Ltd.