Patent ID: 7894697
Filing Date: 2011-02-22
Classification: C03B,G02B

Abstract:
1. An optical fiber mainly composed of silica glass, said optical fiber comprising a core region extending along a designated axis, a depressed region provided on an outer periphery of said core region, a ring region provided on an outer periphery of said depressed region, and a cladding region provided on an outer periphery of said ring region and doped with F, wherein as compared with a refractive index of pure silica glass, a relative refractive index difference of said core region is greater than 2% but less than 3%, a relative refractive index difference of said depressed region is −1% or more but −0.5% or less, a relative refractive index difference of said ring region is 0.01% or more but 0.24% or less, and a relative refractive index difference of said cladding region is −0.3% or more but −0.1% or less, wherein a ratio Ra (= wherein the outside diameter