OPTICAL FIBER PREFORM AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To prevent cracks from being generated at the time of performing a cut-off work of a front end part of a preform by using a specific optical fiber preform which has a core that is composed of a glass contg. added germanium and a clad that is formed on the periphery of the core and is composed of glass having a lower refractive index than that of a glass of a core. SOLUTION: This preform has a core that is composed of glass contg. added germanium and a clad that is formed on the periphery of the core and is composed of glass having a lower refractive index than that of the glass of the core. In the preform, a region having a reduced added germanium content as compared with that of the central part in the axial direction of the preform is placed in a front end part in the axial direction of the preform. At this time, as the preform, an optical fiber preform having such a region which has a reduced added germanium content and the length of which in the axial direction of the preform is preferably 0.1 to 1 time of the outer diameter of the preform, is preferred.