| 摘要 |
PROBLEM TO BE SOLVED: To provide a Yb-doped optical fiber which features a low loss and has excellent photo-darkening resistance.SOLUTION: A core having Yb, Al, and Ge added to a Yb-doped optical fiber and a clad provided around an outer circumference of the core are provided so that the number NA of apertures of the core is 0.05 or more and 0.15 or less. The mol ratio of Al to Yb contained in the core is controlled to be 1.2 or more and 40 or less, the mol ratio of Al to Ge contained in the core is controlled to be 0.9 or more and 15 or less, and the mol ratio of Ge to Yb contained in the core is controlled to be 0.01 or more and 10 or less. |
