In the recent years the ultra distance optical links is very paid attention in the world. Non linear interference is a important indicator in the ultra distance optical links. Understand that the accumulation of Non linear interference in optical fiber transmission can improve performance better. In this thesis, We studied the characteristics of nonlinear interference noise (NLIN) in fiber-optic communication systems with large cumulative dispersion. Frequency domain and time domain analysis were published, which attributed very different attributes to NLIN. After reviewing the two methods, we have identified some reasonable assumptions that are key to the GN model derivation and are reasonable.