An O-type optical waveguide comprising a rod of fused silica having formed thereon a layer of doped fused silica having an index of refraction which is greater than that of the rod, and an outside layer of fused silica over the layer of doped fused silica. The surfaces between of doped silica, having...http://www.google.es/patents/US4088388?utm_source=gb-gplus-sharePatente US4088388 - O-Type optical waveguide
