Tuning the dispersion and single/multi-modeness of a hole-assisted fiber by the hole's geometrical parameters

Using a vectorial finite element mode solver developed earlier, we studied a hole-assisted multi-ring fiber. We report the role of the hole’s geometrical parameters in tuning the waveguide dispersion and the single/multi-modeness of the particular fiber. By correctly selecting the hole’s size and position, a single-mode fiber with a relatively flat and low dispersion in the S-band of the ITU grid was obtained. We also report the observation of a mode type which has never been reported before for ordinary fibers, which we label as a ‘ring’ mode. This mode exists as a consequence of structural symmetry breaking due to the inclusion of the microstructural holes.