AbstractThe impact of major nonlinearities in optical fiber such as SRR (Stimulated Raman Scattering) and Four Wave Maxing (FWM) in cascaded amplifier Dense Wavelength Division Multiplexing optical long reach and high speed data rate transmission scheme have been investigated at different data rates. Pulse walk off effect is considered for the purpose of calculating Stimulated Raman Scattering (SRS) nonlinear factor. Examination has been accomplished to assess signal to noise ratio thinking about the consolidated impact of SRS and FWM within the sight of amplified spontaneous emission noise to achieve minutest noise at altered data rates.