Fiber preform method with a hot drill-in step for a Ge-doped tube and an F-doped rod

摘要

A tube-shaped, GeO2-doped silica glass pipe having a high refractive index is prepared (step S2), a cylindrical silica glass rod doped with F element is inserted inside the GeO2-doped silica glass pipe (step S3), and the GeO2-doped silica glass pipe and silica glass rod in thus inserted state are heated so as to be unified (step S4). Further, thus formed assembly is inserted inside the a pure silica glass pipe (step S5), and they are heated so as to be unified (step S6), whereby an optical fiber preform is manufactured.