Design and analysis of a multilayer cladding large-mode-area optical fibre

We present a large-mode-area optical fibre design consisting of a multilayer cladding. The cladding is formed by alternate high and low index regions specially designed to strip-off higher-order modes, while causing a nominal loss to the fundamental mode. The fibre is analysed by the transfer matrix method and the leakage losses of the modes are calculated. A high differential leakage loss between the first two modes ensures single-mode operation. With the proposed design a fibre with 30 µm core diameter and 0.16 numerical aperture can exhibit single-mode operation at 1550 nm wavelength. Such a large-core fibre can suppress the nonlinear effects and should be useful for high power applications, including fibre lasers and optical communication systems employing DWDM.