Mode-coupling analysis in axisymmetric birefringent waveguides

Axisymmetric periodic media such as annular layers have axi-symmetric birefringence. I report the theoretical analysis of mode coupling in axisymmetric birefringent waveguides. Any of the LP11 modes in a perturbed system can couple with a corresponding LP11 mode that is orthogonal to the original mode with respect to both the polarization direction and the node line of an electric field. The coupling beat length depends on the amount of birefringence, which can be as short as 5 mm for a practical structure. (C) 1997 Optical Society of America.