Patent ID: 7116472

Claim:
An optical fiber comprising: a silica core region doped with at least one rare earth element, a cladding region adjacent said core region, characterized in that said core region is doped with erbium so as to amplify an optical signal propagating therein at a center wavelength in the approximate range of 1525 nm to 1610 nm in response to an optical pump signal applied thereto at a center wavelength of approximately 1000 nm or 1500 nm and at a power level of at least about 100 mW, the composition of said core region includes aluminum with a mole fraction of about 8–20 mole %, germanium with a mole fraction of about 0.1–5 mole %, and fluorine with a mole fraction of about 0.5–5 mole %, said core region composition producing a flatter gain spectrum within said wavelength range and a higher power conversion efficiency at pump powers above about 100 mW than fibers having different composition, and said core and cladding regions are configured so that said fiber has a numerical aperture of less than approximately 0.20.