| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical fiber capable of facilitating manufacture and exhibiting stable and excellent optical characteristics, and to provide a manufacturing method thereof.SOLUTION: An optical fiber 1 includes a core region 2 and a cladding region 5 provided around the core region 2 and having a refractive index lower than that of the core region 2. The cladding region 5 includes a depressed layer 3 adjacent to the core region 2 and a jacket layer 4 provided on an outer circumference of the depressed layer 3. The depressed layer 3 has a refractive index lower than that of the jacket layer 4, and a difference A [%] of a relative refractive index difference in the depressed layer 3 which is defined as "&Dgr;n3a (a relative refractive index difference at the innermost circumference of the depressed layer 3)-&Dgr;n3b (a relative refractive index difference at the outermost circumference of the depressed layer 3)" satisfies -0.02≤A<0. |
