These non-linearities can be generally categorized as either scattering effects (stimulated Brillouin scattering and stimulated Raman scattering) or effects related to the fibre's intensity dependent index of refraction (self-phase modulation, cross-phase modulation, modulation. These non-linearities can be generally categorized as either scattering effects (stimulated Brillouin scattering and stimulated Raman scattering) or effects related to the fibre's intensity dependent index of refraction (self-phase modulation, cross-phase modulation, modulation. Fiber optic communications provides an enormous bandwidth for high speed data transmission. Optical fiber is an excellent transmission medium due to its robustness and low losses. We focus sion domin licable which assumes the nonlinear istortion obtain the varian e of. In this paper, three nonlinear effects such as Self-Phase Modulation (SPM), Cross-Phase Modulation (XPM) and Four-Wave Mixing (FWM) are studied when the light signal passes through both single mode and nonlinear optical fibers. Consequently, non-linear fibre behaviour has emerged as an important consideration both in high capacity. Nonlinear effects in optical fiber communication systems arise due to the dependence of a fiber's refractive index on the intensity of the light propagating through it. Deterministic algorithms based on approximating the nonlinear.