Patent ID: 7894698

Claim:
An optical fiber, comprising: a core surrounded by an outer cladding, said core (i) including at least two core dopants, wherein the radial concentration of at least one of said core dopants varies continuously over said core, and (ii) having a radius r 1 and a refractive index difference Δn 1 with said outer cladding; a first inner cladding positioned between said core and said outer cladding, said first inner cladding having a radius r 2 and a refractive index difference Δn 2 with said outer cladding, wherein the maximum refractive index difference between said core and said first inner cladding (Δn 1 -Δn 2 ) is between about 3.0×10 −3 and 7.4×10 −3 ; and a depressed, second inner cladding positioned between said first inner cladding and said outer cladding, said second inner cladding having a radius r 3 and a refractive index difference Δn 3 with said outer cladding of less than −3×10 −3 .