The following figure shows Q-factor vs. average fiber input power plots at 240-km transmission for this topology with linear and nonlinear DCF, with and without amplifier noise. As the launched power increases, the performance keeps on improving until the launched power becomes high enough to cause nonlinearities adversely dominate the overall link performance. For our topology, if we examine the curves corresponding to the cases with and without amplifier noise, we see that until the launched power is low enough, the link noise plays a dominant role. However, at higher launched powers, the nonlinearities dominate the performance impairments as compared to the influence of link noise. Because of the smaller core diameter of the DCF, optical intensities are enhanced thereby resulting in higher nonlinear effects in the DCF section. The nonlinearities in the DCF, as seen in the following figure, can deteriorate the Q-factor by 6 to 9 dB depending upon the launched power.