Efficient Optical Communication in a Turbulent Atmosphere

Given a transmitter that radiates an electromagnetic light field, we assume that the resulting field at the plane of the receiver aperture is log-normal with some coherence properties. Various representations of the field a r e discussed: aperture sampling, plane-wave decomposition, and Karhunen-Logve expansion. The statistical properties of the coefficients in these representations a r e investigated by analytical, simulation, and experimental methods. Based on these representations the problem of optimum detection of an orthogonal signal set , subject to distortion and noise in the atmosphere, is investigated. The optimum receiver and its performance a r e evaluated and discussed in the cases of log-normal and Gaussian statistics, classical and quantum models, large and small apertures, and strong, weak o r absent background noise.