An all-dielectric coaxial waveguide comprising a dielectric core region; an annulus of dielectric material, surrounding the core region, in which electromagnetic radiation is confined; and an outer region of cylindrically coaxial dielectric shells of alternating indices of refraction surrounding the...http://www.google.com.au/patents/US6573813?utm_source=gb-gplus-sharePatent US6573813 - All-dielectric coaxial waveguide with annular sections
