Wireless optical communications is an attractive solution for the so-called "last-mile" problem due to the ever-increasing demand for highspeed communications, and the difficulty of installing cable and optical fiber. In the presence of atmospheric phenomena such as cloud, fog, and turbulence the wireless optical communications channel happens to be time varying and dispersive, required to be accurately modeled. In most of the previous works, Monte-Carlo Ray Tracing (MCRT) algorithm has been used to measure channel parameters, though this algorithm needs a high computational capacity and a long execution time. We show that by modeling the photon trajectory in space by a Markov chain, angular dispersion can be calculated via matrix multiplications. We show that Markov chain model produces values that are close to MCRT algorithm results.