A microstructured fibre having a cladding comprising a number of elongated features that are arranged to provide concentric circular or polygonial regions surrounding the fibre core. The cladding comprises a plurality of concentric cladding regions, at least some of which comprising cladding features. Cladding regions comprising cladding features of a relatively low index type are arranged alternatingly with cladding regions of a relatively high index type. The cladding features are arranged in a non-periodic manner when viewed in a cross section of the fibre. The cladding enables waveguidance by photonic bandgap effects in the fibre core. An optical fibre of this type may be used for light guidance in hollow core fibres for high power transmission. The special cladding structure may also provide strong positive or negative dispersion of light guided through the fibre - making the fibre useful for telecommunication applications.
