Patent ID: 7805038

Claim:
An elongate waveguide for guiding light, comprising: a core region, comprising an elongate region of relatively low refractive index; and a cladding region, comprising elongate regions of relatively low refractive index interspersed with elongate regions of relatively high refractive index, including, in a transverse cross-section of the waveguide, a relatively high refractive index boundary region that surrounds the core region, wherein the boundary region comprises a plurality of relatively high refractive index boundary veins joined end-to-end around the core region at boundary nodes, each boundary node being joined between two boundary veins and to at least one relatively high refractive index region of the cladding region, wherein the boundary region has at most two-fold rotational symmetry at least in part due to one or more boundary veins having different properties than other boundary veins or at least in part due to one or more boundary nodes having different properties than other boundary nodes.