In this paper we drive a numerical model for a separate confinement heterostructure quantum well (SCH-QW) laser, as one of the key elements of photonic communications systems and networks. The physical effects of Deep Level Traps (DLTs) and carrier transport on the threshold current, turn-on delay, steady state time, transient response and wavelength chirp of a SCH-QW laser are modeled by means of finite difference method. This numerical model calculates the time-dependent variations of optical output phase, photon density and carrier densities in the SCH layer and QW region, self-consistently. These equations are also coupled with the trap density equation. The exact carrier dependence of the linewidth enhancement factor and the gain function for the QW laser are included. ©2009 IEEE.