  We experimentally investigate a nonlinear switching mechanism in a dual-core
highly nonlinear optical fiber. We focus the input beam of femtosecond pulses
on one core only, to identify transitions between inter-core oscillations,
self-trapping in the cross core, and self-trapping of the pulse in the straight
core. A model based in the system of coupled nonlinear Schrodinger equations
provides surprisingly good agreement with the experimental findings.
