Process for fabricating a optical fiber preform.

摘要

A first process of the invention comprises impregnating a solution while controlling the concentration in response to a quantity of a transmitted laser beam through a soot-like core glass (26), by which the doping concentration is ensured independently of the density of the soot-like core glass. A second process of the invention comprises repeating formation of a soot-like core glass (26) at different temperatures, by which a distribution of a doping concentration along the radial direction of the core can be arbitrarily set. A third process of the invention comprises forming two constricted portions (28) at a quartz reaction tube (4), charging a solution of a compound of a rare earth element as a solution into the section between the constricted portions (28) for doping. By this, the doping concentration becomes uniform along the length of an optical fiber preform (30) with defects being rarely produced. This process does not involve any complicated operation. <IMAGE>