| 摘要 |
PROBLEM TO BE SOLVED: To make excitation efficiency higher than conventional in a double core type of optical fiber that is constituted by forming a second core on the outer periphery of a first core. SOLUTION: A long period grating 8 that introduces excitation light propagating in a second core 4 into a first core 2 is formed in the first core 2. Consequently, in a double core type of optical fiber, the excitation light propagating in the second core is introduced along an axial direction of the first core by mode coupling of the long period grating, so that excitation in the axial direction is possible, and excitation efficiency is made higher than conventional. |
