Method for producing glass preform for optical fiber.

摘要

Fluorine is selectively added to a cladding portion of a glass preform by producing a soot preform which comprises a core portion (9) and a cladding portion (10) under such conditions that an additive concentration or a bulk density of the outermost part (11 B) of the core portion (9) is to be larger than that of the inner part thereof and heating the soot preform in an atmosphere containing fluorine or a fluorine-containing compound at least in some period to obtain a transparent glass preform.