| 摘要 |
PROBLEM TO BE SOLVED: To achieve an optical fiber capable of suppressing heat generation of a second clad due to excitation light without significantly influencing on core properties.SOLUTION: An optical fiber (1) includes, between a first clad (21) and a second clad (23), a low refractive index layer (22) with an intermediate refractive index. A clad diameter of the first clad (21) is greater than or equal to 2.5 times of an MFD (mode field diameter) of a fluorescent wavelength in a fundamental mode of an active element of a core (10). A layer thickness of the low refractive index layer (21) is greater than or equal to an absorption wavelength of the active element.SELECTED DRAWING: Figure 1 |
