| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical coupler in which the signal light amplification function of an optical fiber for amplification works effectively over a longer distance, without applying a thermal load causing damage on an optical fiber for optical amplification, and the high energy of a fiber laser is achieved by increasing the excitation light.SOLUTION: The numerical apertures of a plurality of optical fibers for excitation light used in an optical coupler are not identical entirely, but the numerical apertures of some optical fibers for excitation light are differentiated from those of other optical fibers for excitation light. Consequently, the place where the excitation light passes through the core of an optical fiber for amplification for the first time, and the number of times passing through the core are changed. |
