Patent ID: 8285099

Claim:
An optical fiber amplifier comprising: an optical gain fiber for propagating a single mode, said optical gain fiber providing optical gain, said optical gain fiber comprising: (i) a cladding region comprising a plurality of cladding features disposed in a matrix, said plurality of cladding features having an average spacing, Λ, and an average size, d; and (ii) a core region surrounded by said cladding region, said plurality of cladding features substantially confining propagation of said single mode to said core region, said plurality of cladding features having (i) sufficient average spacing, Λ, to provide an increased effective core size, 2ρ, and (ii) a sufficient average size, d, to provide substantial confinement of light within said core region, wherein an inner portion of said cladding region defines said core region, said inner portion comprises a first plurality of said plurality of cladding features, and said average size, d, of said first plurality of cladding features is greater than about 60% of said average spacing, Λ, of said first plurality of cladding features.