In this study we explain the optical bistability phenomena in a nonlinear fiber optic ring resonator which consists of a single microring resonator connecting to a single coupler to show the benefit of light propagating within a nonlinear medium. In such a way, nonlinear behaviors of the output signals from a fiber optic ring resonator such as the bistability have been investigated with an iterative method using an input Gaussian beam. Here, we present the dynamic simulation of light travelling in a fiber optic coupled with a Single coupler.