In this work, we studied the optical bistability of Fiber Bragg Grating (FBG) under nonlinear regime, considering three increasing and decreasing profiles of nonlinearity: linear, quadratic and exponential. We varied the nonlinearity range in each profile, and obtained different curves of bistability and reflectivity. We analyzed the powers [Formula: see text] and [Formula: see text], as well as the width of the photonic band gap ([Formula: see text] of each device under different nonlinearity profiles, and we observed the changes in reflectivity of the FBG. The power intensities [Formula: see text] and [Formula: see text] obtained for the bistability of decreasing profiles were lower than those obtained for the increasing profiles, and the values of [Formula: see text] were also lower in decreasing profiles, which is useful for optical switching applications.