| 摘要 |
Provided is an optical fiber, having a depressed cladding structure including a silica glass core including chlorine and a first cladding and a second cladding of silica glass including fluorine, whereby it is possible to execute a single-mode propagation in a signal light wavelength. An optical fiber comprises a core, a first cladding, and a second cladding. The core is formed from silica glass including chlorine. The first cladding and the second cladding are formed from silica glass including fluorine. The refractive index of the first cladding is lower than the refractive index of the core. The refractive index of the second cladding is lower than the refractive index of the core, and higher than the refractive index of the first cladding. The second cladding is divided into an outer side region having a uniform refractive index and an inner side region having a higher refractive index than the refractive index of the outer side region. The difference &Dgr;P between the maximum refractive index of the inner side region and the refractive index of the outer side region is a relative refractive index with pure silica glass as a reference of 0.02-0.10%. The radial thickness R of the inner side region is 10-25μm. |
