Abstract
The propagation and switching of short optical pulses in a three-core nonlinear fiber coupler have been investigated with a variational method within the framework of the Lagrange equation. The analytical solutions were directly obtained from the coupled nonlinear Schrodinger equations. It is shown that the soliton switching behavior predicted by our analytical method agrees well with results from numerical analysis. In addition, the coupling length and the switching threshold of solitons in a nonlinear coupler were obtained.