Divergence and aperture angle of conical light guides

Relations derived for the angle of divergence and the aperture of hollow metallic or dielectric cones may not directly be assigned to dielectric core/cladding light guides. The accurate results for the angle of aperture and divergence are stated here under consideration of the total internal reflection at the junction of the core to the surroundings. Furthermore the full angle of the conical element, the geometrical length and the varying diameters, the refractive indices and non-axial ray entrance are considered. All derivations are made by means of geometrical optics for meridional rays.