Abstract

Optical fibers doped with rare-earth ions, such as erbium and neodymium, have attracted considerable attention in view of their applications in light-wave communications and mode-locked lasers. Such doped fibers can be modeled by the Maxwell-Bloch equations, commonly used for two-level atoms, generalized to include the effects of group-velocity dispersion and self-phase modulation induced by the host fiber. This paper discusses optical instabilities inherent in doped fiber amplifiers by considering the steady state solution of the Maxwell-Bloch equations and investigating its stability through a linear stability analysis. Particular attention is paid to the modulation instability occurring even in undoped fibers. Numerical simulations are used to study the growth of perturbations in the nonlinear regime, where the linear stability analysis becomes invalid. The results have implications for mode-locked fiber lasers.

© 1992 Optical Society of America