| 摘要 |
PROBLEM TO BE SOLVED: To achieve a single mode optical fiber where the mode field diameter is large and the bending loss is low.SOLUTION: This single mode optical fiber has: a clad part 10 where the refractive index is uniform, a first core part 21 that is arranged at the center of the clad part 10 and where the specific refractive index difference to the clad part 10 is Δ and the radius is a1; a second core part 22 that is arranged on the outer periphery of the first core part and where the refractive index is equivalent to that of the clad part and the radius including the first core part is a2; and a third core part 23 that is arranged on the outer periphery of the second core part and where the specific refractive index difference to the clad part is Δ1 and the radius including the first core part and second core part is a. The radius a is 9.7-18.6 μm, the specific refractive index difference Δ is 0.15-0.40%, the ratio Ra1 of the radius a1 to the radius a is 0.38-0.44, the ratio Ra2 of the radius a2 to the radius a is 0.60-0.74, and ratio RΔ of the specific refractive index difference Δ1 to specific refractive index difference Δ is in each range of -0.60 to -1.60. |
