Removing the Directional Degeneracy of Mode in a Fused-Type Mode Selective Coupler

摘要

The removal of polarization and modal degeneracy in the excitation of higher order modes is realized in all-fiber mode-selective weakly fused couplers by controlling the coupler geometry. Experiments carried out with short couplers showed strong polarization dependence, while long couplers with a slow varying cross section have shown to remove polarization and spatial degeneracy in the first high-order mode.