Patent ID: 7555186

Claim:
An optical fiber, comprising: a central core surrounded by an outer optical cladding, said central core (i) including at least two core dopants, wherein the radial concentration of at least one of said core dopants varies substantially continuously over said central core, and (ii) having a radius r 1 that is between about 3.5 microns and 4.5 microns and a positive refractive index difference Δn 1 with said outer optical cladding of between about 4.2×10 −1 and 6.2×10 −3 ; a first inner cladding positioned between said central core and said outer optical cladding, said first inner cladding having a radius r 2 that is between about 7.5 microns and 14.5 microns and a refractive index difference Δn 2 with said outer optical cladding of between about −1.2×10 −3 and 1.2×10 −3 ; and a depressed, second inner cladding positioned between said first inner cladding and said outer optical cladding, said second inner cladding having a radius r 3 that is between about 12.0 microns and 25.0 microns and a refractive index difference Δn 3 with said outer optical cladding of between about −15×10 −3 and −3×10 −3 .