In this paper we drive a numerical model, based on physical principles, for asymmetric multiple quantum well (AMQW) lasers, as one of the key elements of optical communication systems. AMQW lasers can exhibit broad net gain profile for improved wavelength tuning. The spectra and gain characteristics were investigated for an AMQW laser with two wide and two narrow QWs. The physical effects of carrier transport on the threshold current, transient response and specifically wavelength chirp of two different AMQW structures are modelled by means of finite difference method and compared with a conventional MQW structure. This numerical model calculates the time-dependent variations of optical output phase, photon densities and carrier densities in the SCH, QW and the barrier regions, self-consistently. The exact carrier dependence of the linewidth enhancement factor and the gain function for the QW laser are included. © 2008 IEEE.