Wave optics simulation study of multiple Gaussian beam transmitters for free space optical transmission through turbulence

The use of multiple, mutually incoherent beams for a laser link through turbulence can reduce the effects of scintillation at the receiver. A recent approach involving an array of parallel propagating beams in a circle pattern has been presented in the literature and studied to determine the best beam spacing for the lowest scintillation effects. This approach has the disadvantage of reduced irradiance at the receiver as the beam separation increases. To remove this constraint, we present a modified approach where the multiple beams are individually aimed at the receiver. A wave (physical) optics simulation was applied to study the performances of 2-, 3-, 4-, and 5-beam transmitter sources. The mean irradiances I and scintillation indices σI2 are examined for some specific link geometries and fluctuation strengths and the results are compared with those of the original method. For evaluation, we also employ a recently proposed performance metric that incorporates both I and σI2 to indicate the near-optimal beam separation for the cases studied. Finally, we examine the probability of fade for our selected cases the modified approach has improved performance.