Supraluminal velocity of a pulse envelope maximum in amplifying optical fiber

Frequency-modulated Gaussian pulse propagation in an amplifying fiber is de scribed within the framework of a linear model with an allowance for the se cond-order dispersion effects. It is demonstrated that the presence of an i maginary part in the group velocity dispersion parameter of the single-mode optical fiber with luminous gain leads to the possibility of the pulse env elope at a supraluminal velocity. (C) 2001 MAIK "Nauka/Interperiodica".