Abstract: The present invention relates to a new class of optical waveguides, in which waveguiding along one or more core regions is obtained through the application of the Photonic Bandgap (PBG) effect. The invention further relates to optimised two-dimensional lattice structures capable of providing complete PBGs, which reflects light incident from air or vacuum. Such structures may be used as cladding structures in optical fibers, where light is confined and thereby guided in a hollow core region. In addition, the present invention relates to designs for ultra low-loss PBG waveguiding structures, which are easy to manufacture. Finally, the present invention relates to a new fabrication technique, which allows easy manufacturing of preforms for photonic crystal fibers with large void filling fractions, as well as it allows a high flexibility in the design of the cladding and core structures.

Abstract: A micro-structured optical fibre having a cladding comprising a number of elements having a non-circular cross-section. Each element has at least one part extending outside a circle having the same cross-sectional area as the element. These extending parts are directed in the same direction. This cladding structure provides polarisation preserving properties to the optical fibre. Optical fibres using this technology may have claddings with elements placed non-periodically as well as in a two-dimensional periodic lattice-such as cladding providing Photonic Band Gap (PGB) effects.