RING LASER CONFIGURATION STUDIED BY COLLECTIVE COORDINATES

A perturbed nonlinear Schrodinger equation is used to model an optical laser fiber ring for generation of femtosecond optical pulses. The ri ng is built from a nonlinear laser fiber joint together with a passive nonlinear fiber. We assume that the optical pulses are solitons pertu rbed by loss and gain. Starting from the single-soliton solution of th e nonlinear Schrodinger equation, we use a collective coordinate appro ach to derive a Lagrangian as a function of the collective coordinates . The evolution equations for the collective coordinates emerge from t he Lagrange equations, including the associated generalized forces tha t result from the perturbations. Remarkably good agreement is obtained between the collective coordinate approach and the full numerical sim ulations of the fiber ring laser.