Collisions of optical ultra-short vector pulses

Asymptotic two-pulse solutions of a modified (via attaching a nonlinear derivative term) vector nonlinear Schrodinger equation (MVNSE) are analyzed using the Hirota (bilinearization) method. This equation is known to describe the propagation of ultra-short optical pulses in nonlinear fibers (in particular, in the optical-crystal fibers). Some pulse-parameter regimes of applicability of the solutions to study the pulse collisions are estimated. It is found, for these regimes, that the collision of ultra-short vector pulses of almost equal velocities results in a transformation of their polarizations similar as that of the Manakov solitons whenever the pulse-interaction effects can be neglected.