Patent ID: 8488931

Claim:
An optical fiber comprising: an optical core surrounded by an outer optical cladding, said optical core comprising from its center to its periphery a central core and a depressed inner cladding, said central core having a radius r 1 , and a refractive index difference Δn 1 with respect to the outer optical cladding, and said depressed inner cladding comprising at least a first and a second portion; wherein said first portion is adjacent to the central core and has a radius r 2 , and a refractive index difference Δn 2 with respect to the outer optical cladding that is negative; wherein said second portion is adjacent to the first portion having a radius r 3 , and a refractive index difference Δn 2 with respect to the outer optical cladding that is negative; wherein the refractive index difference Δn 3 is more negative than the refractive index difference Δn 2 ; wherein the outer radius of the depressed inner cladding is between 28 and 40 μm; wherein the LP 01 mode leakage losses at a wavelength of 1550 nm are less than 0.01 dB/km; and wherein the cable cut-off wavelength is less than 1530 nm.