Atmospheric adversities impacts on the performance of free space optical (FSO) links, with turbulence-induced fading being the most prominent among them. Since FSO links involve transmission of optically modulated signal through atmosphere, it is crucial to have well defined mathematical model to understand and map association of atmospheric turbulence with channel link characteristics. To model a reliable optical wireless communication link, it is important to have an accurate probability density function (PDF) of received intensity, as it allows us to understand the atmospheric factors and magnitude of their impact that may lead to impairment of the link. It was observed that the variation in turbulence has a direct impact on channel behaviour and in turn affects the PDF of received intensity. This paper also analyses the performance of different channel models by contrasting their PDF for varying degrees of turbulence.