Propagation characteristics of an optical waveguide with a diffused core boundary

When a unimode glass-fibre optical waveguide is produced by the double-crucible process, diffusion between core and cladding glasses is known to occur. The refractive-index profiles are determined theoretically in the letter for different rates of diffusion, under the assumption of infinite cladding radius. Subsequently the propagation characteristics of the dominant HE11 mode have been computed by means of a stratification approximation to the continuous refractive-index profile. Only at high diffusion rates is the predicted increase in electromagnetic dispersion unacceptable.