Influence of cores' shape on the coupling length of dual-core fiber

The deviation of cores' shape in dual-core fiber may affect the coupling characteristics between the two cores. For the same given cores' area in three kinds of dual (circular, elliptical, egg-shaped) core fiber, the relationship of the coupling length with the cores' shape is calculated at different wavelength It is found the coupling length of dual-circular-core fiber is the longest and dual-elliptical-core fiber is the shortest while dual-egg-shaped-core fiber is in the middle.