Modal dispersion curves of an optical waveguide with a core cross-section partially bounded by one turn of an equiangular spiral under weak guidance approximation

In this paper, we present a theoretical analysis of propagation of electromagnetic waves through a fiber with a spiral shape core cross-section with two cases. In one case the remaining unbounded part closed by a straight line and in other case remaining part not bounded by well defined line. Using Goell's point matching method under weak guidance condition modal characteristic equations for the lowest order modes are derived. The comparison of dispersion curves for two cases is also shown and interpreted.