ABSTRACT
All deviations from the ideal channel such as loss, chromatic dispersion, polarization mode dispersion and nonlinearities are usually called transmission impairments. In a dielectric medium like fused silica, nonlinear effects are weak and can be treated as perturbation. The term nonlinear refers to the wave equation that becomes nonlinear when the transmission medium characteristics become signal-dependent. The nonlinear Schrodinger equation describes that birefringent-independent unidirectional propagation of light in single-mode fibre. The system of coupled equations described in is extremely challenging to solve in practice because the nonlinear terms depends on the phase difference between modes which evolves rapidly due to modal dispersion. In long-haul systems where amplified spontaneous emission (ASE) noise accumulates along the link, the contribution of ASE noise to nonlinear effects may become non-negligible. Kerr-induced signal distortions can be described as an additive noise term referred to as nonlinear-induced interference noise.
