Accurate Analysis of Crosstalk Between LP$_{11}$ Quasi-Degenerate Modes Due to Offset Connection Using True Eigenmodes

Linearly polarized (LP) modes in few-mode fibers are not true eigenmodes but approximated modes constituting of linear combinations of true eigenmodes. Therefore, the vector field profile in a few-mode fiber must be expressed in terms of the true eigenmodes with complex amplitudes involving a phase difference corresponding to the propagation distance. Owing to this property of LP mode propagation, the propagation characteristics of few-mode fibers cannot be accurately analyzed using conventional LP modes. In this study, the crosstalk between LP
₁₁
quasi-degenerate modes due to offset connection is accurately analyzed using matrix formalism expressing the linear combination of true eigenmodes. The difference in the analytical results between the LP modes and the eigenmodes revealed that the propagation of few-mode fibers should be analyzed using true eigenmodes.