Patent ID: 8396340

Claim:
An optical fiber comprising: a core having an outer diameter of greater than or equal to 8.2 μm and less than or equal to 10 μm; a first cladding surrounding the core, having a lower refractive index than the core, and having an outer diameter of greater than or equal to 30 μm and less than or equal to 40 μm; a second cladding surrounding the first cladding, having a lower refractive index than the first cladding, and having a thickness of greater than or equal to 7.4 μm and equal to or less than 22.5 μm; and a support layer surrounding the second cladding, wherein a relative refractive index difference which is a ratio of a difference between a refractive index of the support layer and a refractive index of the second cladding to the refractive index of the support layer is greater than or equal to 0.5% and equal to or less than 1.65%, and the first cladding is doped with light attenuating dopant so that a concentration of the light attenuating dopant in the first cladding increases from an inner surface of the first cladding to an outer surface of the first cladding.