OPTICAL FIBER AND OPTICAL APPARATUS

PROBLEM TO BE SOLVED: To provide an optical fiber in which unnecessary excited light in a double clad fiber is removable with a simple configuration, and to provide an optical apparatus including the optical fiber. SOLUTION: The optical fiber includes: a core 11; a double clad fiber 1 including clads 12 and 13; and a single clad fiber 2 including a core 21 and a clad 22. The diameters of the cores 11 and 12, and the outer diameters of the clads 12 and 22 are so decided that the diameter of the core 21 is equal to or larger than the diameter of the core 11, and the outer diameter of the clad 22 is equal to or larger than the outer diameter of the clad 12. Further, NA of the clad 22 is decided to be equal to or larger than NA of the clad 12. A portion of excited light B which is made incident from the clad 12 to the clad 22 becomes deviant excited light C which is radiated to the outside through a coating 24 at the boundary face between the clad 22 and the coating 24. The rest of the excited light is reflected on the boundary face and becomes excited light D which propagates in the clad 22. COPYRIGHT: (C)2009,JPO&INPIT