| 摘要 |
The present invention can easily realize an optical fiber and an optical transmission line that can propagate a light in a single mode while lowering a macro-bending loss against a small-diameter bending. An optical fiber 1 according to the present invention includes a first cladding region 3 having a refractive index lower than a refractive index of a core region 2 on outer circumference of the core region 2 . Sub-medium regions 5 a to 5 f , 6 a to 6 f are arranged in multilayer in the first cladding region 3 , which have a refractive index lower than a refractive index of a main-medium region of the first cladding region 3 . The sub-medium regions 5 a to 5 f having a circular shape with a lateral cross section of a diameter d 1 is arranged in an inner cladding area 3 a of the first cladding region 3 , and the sub-medium regions 6 a to 6 f having a circular shape with a lateral cross section of a diameter d 2 (>d 1 ) is arranged in an outer cladding area 3 b of the first cladding region 3.
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