Modulation instability in an extended nonlinear Schrodinger equation

Abstract

Modulation instability is investigated in an extended nonlinear Schrodinger equation. This effect results in the instability of an initially cw optical beam. Here the effects of modulation instability in an optical fiber are investigated. The instability manifests itself through the appearance of new frequencies in the spectrum which give rise to a periodic temporal behavior of the optical beam. Besides the first-order dispersion and intensity-dependent index of refraction, higher-order dispersion terms, the time variation of the intensity of the slowly varying envelope of the electromagnetic field and retardation effects are considered. It is found that higher-order odd dispersion terms do not influence the frequency of the modulation instability. The time derivative of the intensity of the optical beam can restrict the parameters over which modulation instability occurs. Furthermore, the nonlinear retardation effect significantly alters the modulation instability.