| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to enhance lateral excitation efficiency by forming a scattering means for scattering the skew component of the exciting light made incident on the inside of a second core formed on the outer periphery of a first core at the second core. SOLUTION: The optical fiber 11 for amplification comprises the first core 2, the second core 4 and a clad 6. A different nature part 8 having the refractive index different from the refractive index of the second core 4 is embedded in the second core 4. The different nature part 8 is a scattering means for scattering the skew component of the exciting light made incident on the second core 4. The light of the skew component swirling along the circumferential direction in the second core 4 is refracted in the different nature part 8 at the time of passing the part and is changed in the pass direction and, therefore, the probability of the light intersecting with the first core 2 is increased. The different nature part 8 does not, however, induce the refraction of the light to the light of the skew component on the side outer than the different nature part 8 and does not contribute to the lateral excitation and therefore, the different nature part 8 may be preferably disposed in the position near the clad 6 as far as possible. |
