A polyimide resin layer is formed on an inner surface of a metal pipe or a non-metallic pipe having a metal thin film on an inner surface to provide an optical hollow waveguide. The polyimide resin layer is transparent relative to a wavelength band of a laser light transmitted through the optical...http://www.google.co.uk/patents/US5729646?utm_source=gb-gplus-sharePatent US5729646 - Optical hollow waveguide, method for fabricating the same, and laser transmission apparatus using the same 
