A large-signal dynamic travelling optical flux analysis of a GaAs/AlGaAs monolithic active integrated-optic waveguide (AIOW) is presented. The model uses a combination of numerical and analytical techniques to solve the photon flux and carrier density conservation equations in time, the longitudinal dimension and optical wavelength. An analysis of the fundamental and harmonic frequency response of the waveguide is obtained, along with pulse and sinusoidal modulation response. This analysis is compared with a small signal analysis of the guide, and the two models are found to be in extremely close agreement for the limiting case of a small signal input applied to the large signal model.