Selection Transmit Diversity for FSO Links Over Strong Atmospheric Turbulence Channels

In this letter, transmit laser selection for multiple-input–single-output free-space optical communication systems with intensity modulation and direct detection over strong atmospheric turbulence channels is analyzed. Assuming channel side information at the transmitter and receiver, a transmit diversity technique based on the selection of the optical path with a greater value of scintillation has shown to be able to extract full diversity as well as providing better performance compared to other alternatives recently proposed such as orthogonal space–time block codes and repetition codes. Simulation results are further demonstrated to confirm the analytical results obtained for a diversity order of two.