Optical heterodyne receiver design by nonlinear recursive estimation techniques

A generalized statistical model is developed for the intermediate frequency (IF) signal of an optical heterodyne receiver. The model considers inherent frequency modulation of the carrier and local oscillator and also amplitude and phase fluctuations of the received carrier as it passes through a turbulent atmosphere. The power spectral density of the frequency modulation of the lasers is modeled and corroborated by measurements. Computations of the power spectral density of the atmospheric fluctuations are also presented. A nonlinear recursive estimation technique is developed for estimating the phase of the IF signal. Simulation results are presented for two statistical models of the atmospheric fluctuations.