Average BER analysis of SCM-based free-space optical systems by considering the effect of IM3 with OSSB signals under turbulence channels

In this paper, we derive the average bit error rate (BER) of
subcarrier multiplexing (SCM)-based free space optics (FSO) systems
using a dual-drive Mach-Zehnder modulator (DD-MZM) for optical
single-sideband (OSSB) signals under atmospheric turbulence channels. In
particular, we consider the third-order intermodulation (IM3), a significant
performance degradation factor, in the case of high input signal power
systems. The derived average BER, as a function of the input signal power
and the scintillation index, is employed to determine the optimum number
of SCM users upon the designing FSO systems. For instance, when the user
number doubles, the input signal power decreases by almost 2 dBm under
the log-normal and exponential turbulence channels at a given average BER.