PHOTONIC CRYSTAL FIBER FOR OPTICAL AMPLIFICATION

PROBLEM TO BE SOLVED : To reduce a connection loss in the case of connecting another fiber to a PCF. SOLUTION : In an optical propagation area 14, a core 12 added with an additive consisting of rare earth elements is formed. When the ratio refractive index difference between the core 12 and the optical propagation area 14 surrounding the core is designated to be Δ(%) and the thin hole pitch of a porous part 16 are designated to be Λ(μm), the thin hole pitch Λ is not larger than 9μm, and the ratio refractive index difference Δ and the thin hole pitch Λ meet following two relational expression Δ≤0.265 Λ2-2.35Λ+5.20Δ≤0.05Λ2-0.46Λ+0.93.