Performance analysis of WDM-free-space optical transmission system with M-QAM modulation under atmospheric and optical nonlinearities

In this paper, we have studied the performance of M-QAM based free-space optical link (FSO) integrated with Wavelength-division multiplexing (WDM) in the presence of both optical nonlinearity and atmospheric turbulence. Our analysis shows that joint effect of optical and FSO channel nonlinearity degrades the transmission performance link performs in terms of BER and EVM. The optimization in terms of optical modulation index (OMI) to mitigate the above detrimental factors is also presented.