We proposed a novel extended semiconductor optical amplifier (SOA) model for applications in femtosecond pulse
transmission, in which the various ultra-fast nonlinear effects, such as gain dispersion, group velocity dispersion (GVD)
were taken into account. We use the extended SOA model to analyze the refractive index in response to variation of the
input current and the length of SOA. In addition, the impact of carrier density pulsation and carrier heating on the
refractive index dynamics of SOA was discussed respectively.
The refraction index dynamics that occur in bulk InGaAsP SOA in response to femtosecond pulse (Full width at half
maximum is 200fs) are studied numerically. We use the alpha factors (α-factors) to calculate the phase shift from the
gain variations, which are related to the refractive index changes. We have considered the effects of carrier heating (CH),
and spectrum hole burning (SHB) to analyze the impact of intra-band carrier dynamics on nonlinear refraction index. We
also consider the impact of the length of SOA and operation condition on the refraction dynamics.