Patent ID: 7623747

Claim:
An optical transmission fiber, comprising: a central core and an outer optical cladding, the central core having a first refractive index difference (Δn 1 ) as compared to the outer optical cladding; a first inner cladding immediately surrounding the core, the first inner cladding having a second refractive index difference (Δn 2 )as compared to the outer cladding; a second, buried, inner cladding disposed between the first inner cladding and the outer cladding, the second inner cladding having a third refractive index difference (Δn 3 ) as compared to the outer cladding, wherein the second refractive index difference (Δn 2 ) is between −1.2×10 −3 and 2.0×10 −3 , wherein the third refractive index difference (Δn 3 ) is less than −3×10 −3 , and wherein the second inner cladding contains Germanium in a weight concentration of between 0.5% and 7%.