Airborne laser-communication systems require special considerations in size, complexity, power, and weight. We reduce the variability of the received signal by implementing optimized multiple-transmitter systems to average out the deleterious effects of turbulence. We derive the angular laser-beam separation for various isoplanatic and uncorrelated (anisoplanatic) conditions for the phase and amplitude effects. In most cases and geometries, the angles ordered from largest to smallest are: phase uncorrelated angle (equivalent to the tilt uncorrelated angle), tilt isoplanatic angle, phase isoplanatic angle, scintillation uncorrelated angle, and scintillation correlation angle (𝜃𝜓𝑖𝑛𝑑>𝜃𝑇𝐴>𝜃0>𝜃𝜒𝑖𝑛𝑑>𝜃𝜒𝑐) . Multiple beams with angular separations beyond 𝜃𝜒𝑐 tend to reduce scintillation variations. Larger separations such as θTA reduce higher-order phase and scintillation variations and still larger separations beyond 𝜃𝜓𝑖𝑛𝑑 tend to reduce the higher and lower-order (e.g. tilt) phase and scintillation effects. Simulations show two-transmitter systems reduce bit error rates for ground-to-air, air-to-air, and ground-to-ground scenarios.
James A. Louthain and Jason D. Schmidt, "Anisoplanatism in airborne laser communication," Opt. Express 16, 10769-10785 (2008). https://doi.org/10.1364/OE.16.010769