An optical fiber that includes a core containing a first concentration of germanium, an inner cladding arranged on the core, the inner cladding containing a second concentration of germanium and having a first diffusion coefficient, and an outer cladding arranged on the inner cladding, the outer cladding...http://www.google.de/patents/US7346258?utm_source=gb-gplus-sharePatent US7346258 - Optical fiber and optical fiber coupler, erbium-doped optical fiber amplifier, and optical waveguide using the same
