| 摘要 |
A photonic band gap fiber comprises a first core having a refractive index equal to or lower than that of a clad, a second core surrounding the first core and having a refractive index lower than that of the first core, the clad surrounding the second core, and a periodic structure part provided to the clad near the second core and so constituted that a high refractive index portion having a refractive index higher than that of the clad forms a periodic structure. The periodic structure part functions as a wavelength filter. As a result, the propagation loss of the transmitted wavelength is small, and that of the cut-off wavelength is large. |
