Supermode analysis of fibre transmission

An analysis is presented of propagation along practical, single-mode matched-cladding and depressed-cladding slab waveguides and fibres using the bound modes of the entire core-cladding-coating-air cross-section, instead of the usual bound-radiation-mode model of a finite core and unbounded cladding. The model readily quantifies the spatial transient in terms of modal absorption and scattering in the coating, and also displays leaky-mode behaviour, as well as the characteristic transmission dips associated with the fundamental mode beyond its cutoff wavelength in a depressed-cladding fibre