Modulational instability of optical waves in the high dispersive cubic-quintic nonlinear Schrodinger equation

The modulational instability of an extended nonlinear Schrodinger equation with the third and fourth-order dispersion and the cubic-quintic nonlinear terms, describing the propagation of extremely short pulses, is investigated. Two types of gains by modulational instability are found to exist in both the anomalous and normal dispersion regimes under some constraints among the model coefficients. The evolutions of modulational instability in both the anomalous and normal dispersion regimes are numerically investigated and the effects of the higher-order dispersion and nonlinear terms on the evolutions are examined. (C) 2002 Published by Elsevier Science B.V.