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Soliton switching in triangular three-core nonlinear directional fiber coupler

We present an analytical investigation of the propagation and the switching of fundamental solitons in a triangular three-core nonlinear fiber coupler with a variational method using the Lagrangian density formulation. The analytical solutions were directly obtained from the coupled nonlinear Schrodinger equations. The transmission characteristics of first-order solitons obtained by the analytical procedure agree well with the results from numerical analysis. Taking into account the length of the coupler and the critical power a comparative study between this geometry and planar geometries were done. The triangular geometry has a shorter device length compared with planar geometries.