Patent ID: 6892018

Claim:
An optical fibre for transmitting light, said optical fibre having an axial direction and a cross-section perpendicular to said axial direction, said optical fibre comprising: a core region, and a micro-structured cladding surrounding said core region, wherein the cladding comprises a number of successive concentric cladding regions encompassing said core region, each of said concentric cladding regions having inner and outer boundaries of substantially similar cross-sectional shape and a substantially constant background refractive index, a first plurality of the concentric cladding regions being of a low index type, each of said first cladding regions comprising a plurality of spaced apart first cladding features elongated in the fibre axial direction, each of said first cladding feature having a refractive index being lower than the background refractive index of the cladding region comprising the cladding feature, and each said first cladding feature having a largest cross-sectional dimension being smaller than or equal to the distance between the inner and the outer boundary of the cladding region comprising the cladding feature, whereby the geometrical index of a cladding region of the first type is lowered, a second plurality of the concentric cladding regions being of a high index type having a geometrical index being higher than the geometrical index of each of the first plurality of cladding regions, said high index type and low index type cladding regions being alternating arranged so that each low index region at its outer boundary is encompassed by a high index region, and wherein the arrangement of cladding features in relation to the micro-structured cladding as a whole is a non-periodic arrangement in the cross-sectional plane.