Guided modes and loss in Bragg fibres

In this paper we investigate Bragg fibres and compare calculations on the exact fibre structures with calculations based on band diagrams and a simplified model involving multilayers. We show how the number of layers and the core size affect the wavelengths guided, the loss and the effective singlemodedness. An approximate relation between the real and imaginary parts of the effective mode indices is derived. The general design considered has a TE mode as the least lossy mode providing effectively single polarisation non-degenerate mode guidance.