| 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 and a PMD at the same time. An optical fiber 1 according to the present invention includes a cladding region 8 having a refractive index lower than that of a core region 2 on outer circumference of the core region 2 . The cladding region 8 includes a first cladding region 3 in which a plurality of sub-medium regions 5 a to 5 d and 6 a to 6 h are arranged in multilayer. For instance, the sub-medium regions 5 a to 5 d having a refractive index lower than that of a main-medium region of the first cladding region 3 are arranged at each of four folds in the first cladding region 3 rotationally symmetric centering on the core region 2 in an inner cladding area 3 a of the first cladding region 3 , and the sub-medium regions 6 a to 6 h having a refractive index lower than that of the main-medium region of the first cladding region 3 are arranged at each of four folds in the first cladding region 3 rotationally symmetric centering on the core region 2 in an outer cladding area 3 b.
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