| 摘要 |
PROBLEM TO BE SOLVED: To enable a rare-earth element doped optical fiber 1 doped with a rare-earth element to increase the output of an optical amplifier, fiber laser, etc., while the fiber 1 is made to obtain high-quality output light. SOLUTION: Only a doped section 2a provided in the central part of the core 2 of the optical fiber 1 is doped with are-earth elements. The diameter of the doped section 2a is set at the diameter D corresponding to the position of the intersection between both graphically represented light intensity distribution curves indicating the correlation between the distances from the center of the core 2 and the ratios of light intensity at the distances to the maximum light intensity in modes LP01 and LP11 or smaller. |
