An optical waveguide comprises: a core for propagating light; a clad covering the core; and a line convex part extending along a line different from the core, the line convex part comprising a cavity used as a positioning mark inside the line convex part....http://www.google.ca/patents/US7539384?utm_source=gb-gplus-sharePatent US7539384 - Optical waveguide and method of manufacturing the same
