An optical wave guide comprises a cylindrical body which is made of a first transparent dielectric, and a second transparent dielectric which is concentrically formed on the outer periphery of the cylindrical body and which has an index of refraction lower than that of the first dielectric, the central...http://www.google.es/patents/US3973828?utm_source=gb-gplus-sharePatente US3973828 - Optical wave guide
