Efficient sub-harmonic phase-screen generation for modelling of free-space laser communications

Particularly in rural settings, laser based free-space communications channels hold promise to provide the last-mile link for a multitude of applications, including delivery of high-speed internet to the home. Work by Grant et al [1], have demonstrated that scintillation noise is an important factor in optical atmospheric transmission systems, which serves to disperse, deviate, and degrade the laser beam. A powerful numerical method to describe this behaviour generates phase-screens to represent the scintillation, and then propagates the simulated optical beam between the phase-screens. The introduction of subharmonic effects to these phase-screens has been shown to improve accuracy of the models. This paper reports on an efficient algorithm to generate the subharmonic phase-screens for use in such a model.