Abstract
This letter investigates the performance of amplify-and-forward multi-hop free-space optical (FSO) system with radio frequency (RF) backup link over gamma-gamma turbulence channels in the presence of path loss and pointing errors. We exploit the relay-assisted technique to mitigate the effect of path loss, pointing errors, and atmospheric turbulence. In addition, RF backup link is employed to increase the availability and reliability of the system. We consider various weather conditions to investigate their effects on the system's performance. An expression for the ergodic capacity of the considered system is derived. Results show how the hybrid FSO/RF communication system is able to adapt to different atmospheric impairments, and thus improve the performance considerably, especially at low SNR.