Fundamental mode propagation on dielectric fibres of arbitrary cross-section

The behaviour of the propagation constants of the fundamental modes on dielectric fibres of arbitrary cross-section is studied by means of a variational formulation of an integral equation for the electric field. The approximate eigenvalue equation which results from the use of a constant trial field within the core is used to generate dispersion curves for several cross-sectional shapes, including rectangular, elliptical and triangular. Agreement with results computed by other methods, where available, is quite good in the single-mode regime.