Patent ID: 8644664

Claim:
An optical fiber, comprising: a central core surrounded by an outer optical cladding, said central core having an outer radius r 1 and an alpha-index profile with respect to said outer optical cladding, said central core comprising a core matrix doped with at least fluorine and a dopant element that increases refractive index; an inner cladding positioned between said central core and said outer cladding, said inner cladding having (i) an outer radius r 2 , (ii) a width w 2 , and (iii) a refractive index difference Δn 2 with respect to said outer optical cladding; and a buried trench positioned between said inner cladding and said outer optical cladding, said buried trench having (i) an outer radius r 3 , (ii) a width w 3 of between about 2 microns and 10 microns, and (iii) a refractive index difference Δn 3 with respect to said outer optical cladding of between about −15×10 −3 and −6×10 −3 ; wherein, within said central core, the atomic ratio C F of fluorine to all of the constituents of said doped core matrix increases from the center of the optical fiber to said central core's outer radius r 1 ; and wherein, at said central core's outer radius r 1 , the atomic ratio C F of fluorine to all of the constituents of said doped core matrix has a maximum value C F,MAX of between about 8.5×10 −3 and 57×10 −3 .