A new model of analysis of semiconductor laser dynamics under strong optical feedback in fiber communication systems

We report on a new model of analysis of semiconductor laser dynamics under strong optical feedback (OFB) in fiber communication systems. The model treats the optical feedback due to reflection of the laser light on an external fiber grating as a time-delayed optical-field injected to the laser cavity. The model is versatile applicable to an arbitrary strength of optical feedback ranging from weak to strong. The model is applied to stimulate output characteristics and intensity noise in InGaAs lasers pumping fiber amplifiers in a wavelength of 980 run. Influence of intrinsic fluctuations in the intensity and optical phase of the Wing field on the laser dynamics is taken into account. The time-varying trajectories of the output power are presented over a wide range of the injection current. The simulation results indicted that the laser mainly operates in pulsation under strong optical feedback. Counting the intrinsic fluctuations was found to reduce the OFB-induced instabilities so as to. bring the laser faster to its steady state operation. The optical feedback noise is found to be as low as the quantum noise level when the laser is injected well above its threshold level.