Method of making a single-mode optical fiber with multiple concentric core portions by using an outside vapor deposition process

摘要

The present invention relates to a single-mode optical fiber having a configuration which enables lowering of dispersion slope while securing a sufficient MFD. This single-mode optical fiber has a refractive index profile in which an indent with a sufficient width is provided at the center of its core region. In particular, this indent satisfies the following relationship:when the first core portion in the single-mode optical fiber has a mean relative refractive index difference of DELTAn1 with respect to the cladding portion and an outer diameter of a while the second core portion has a mean relative refractive index difference of DELTAn2 with respect to the cladding portion and an outer diameter of b.