Symmetry and degeneracy in microstructured optical fibers

The symmetry of an optical waveguide determines its modal degeneracies. A f iber with rotational symmetry of order higher than 2 has modes that either are nondegenerate and support the complete fiber symmetry or are twofold de generate pairs of lower symmetry. The latter case applies to the fundamenta l modes of perfect microstructured optical fibers, guaranteeing that such f ibers are not birefringent. me explore two numerical methods and demonstrat e their agreement with these symmetry constraints. America.