Stable soliton propagation in a system with spectral filtering and nonlinear gain

Stable soliton propagation in a system with linear and nonlinear gain and s pectral filtering is investigated. Different types of exact analytical solu tions of the cubic and the quintic complex Ginzburg-Landau equation (CGLE) are reviewed. The conditions to achieve stable soliton propagation are anal yzed within the domain of validity of soliton perturbation theory We derive an analytical expression defining the region in the parameter space where stable pulselike solutions exist, which agrees with the numerical results o btained by other authors. An analytical expression for the soliton amplitud e corresponding to the quintic CGLE is also obtained We show that the minim um value of this amplitude depends only on the ratio between the linear gai n and the quintic gain saturating term.