Abstract

By using Gaussian approximation, the modal spot size equation of a weakly guiding double-clad elliptical (DCE) fiber has been numerically solved. The variations of both the spot size and the field intensity with core ellipticity are examined. The results show that, compared with single-clad elliptical fibers, a smaller spot size and a more confined field distribution can be obtained. The polarization properties are also examined and presented as curves in terms of the three parameters: major/minor core axis ratio, inner cladding and core index difference, and inner cladding/core radius ratio. The curves of birefringence as a function of normalized frequency for the different parameters show that high bire-fringence can be obtained within the single-mode region by using DCE fibers.

© 1989 Optical Society of America