Optical gain fiber doped with rare earth ions

Abstract

An optical gain fiber of the present invention is doped with rare earth ions for improving a gain efficiency of a certain transition of the rare earth ions by inhibiting an undesirable amplified spontaneous emission. The optical gain fiber for amplifying an optical signal, includes a core doped with a first rare-earth ion in a portion thereof for amplifying the optical signal, and a clad doped with a second rare earth ion for absorbing an undesirable amplified spontaneous emission (ASE) emitted from the first rare earth ion, wherein the portion of the core and the potion of the clad are separated by the remaining portions of the core and the clad.

Dependencies are inferred from the claim text.