OPTICAL FIBER FABRICATION METHOD

摘要

An object of the present invention is to provide a method by which a fictive temperature can be sufficiently lowered and a low-loss optical fiber can be manufactured with high productivity. When Tf(n) is a fictive temperature of a core at a position n in a drawing step or a slow cooling step, Tf(n+1) is a fictive temperature of the core after the elapse of a unit time ”t, and Ä(T(n)) is a structural relaxation constant of a material of the core at a target temperature T(n) for the position n, a temperature of a heating furnace 20 is set such that in at least 70% of a region from a first position at which a glass outer diameter of the optical fiber becomes less than 500% of a final outer diameter to a second position at which a temperature T of the optical fiber becomes 1400°C, a difference with respect to the target temperature T(n) for each position n is within ±100°C, the target temperature T(n) being a temperature at which Tf(n+1) determined by calculation using the recurrence formula "Tf(n+1) = T(n) + (Tf(n)-T(n))exp(-”t/Ä(T(n)))" starting from a fictive temperature Tf(0) of the optical fiber at the first position n = 0 is lowest.