This paper mainly focuses on nonlinear pulse propagation and four-wave mixing (FWM) characteristics in semiconductor optical amplifiers (SOAs). For simulation, modified nonlinear Schrödinger equation (MNLSE) is used for the modelling of pulse propagation in SOA. In this model, we have included the gain dynamics and all nonlinear effects of the SOAs for simulation. Finite-difference beam propagation method is adopted to solve the MNLSE, obtained nonlinear pulse propagation and FWM characteristics in SOA. The nonlinear pulse propagation characteristics show that the output full width at half maximum (FWHM) is linearly increases with increase of input FWHM. Output pulse energy also increases with the increase of input pulse energy. There are some dips occur at the output spectrum which is due to the gain saturation and self-phase modulation (SPM) effects. The FWM conversion efficiency is good if the detuning is <;1 THz Finally, the FWM signal energy highly dependent on the input pump and probe energies. The FWM signal peak power increases exponentially with the increase of SOA length. Our simulation results are suitable for the design of SOAs those are using in high-speed communication systems and sensor network systems.
