Excitation and propagation of modes of a multilayer fibre

The excitation and propagation characteristics of the lowest-order modes of a glass-fibre waveguide are determined without recourse to approximations concerning the core or cladding radii. Although under unfavourable circumstances higher modes may be strongly excited, by applying a lossy coating to the exterior surface of the fibre, these modes may be strongly attenuated. However, the layer has negligible influence on the attenuation of the dominant mode.