HEAT TREATMENT OF POROUS OPTICAL FIBER PREFORM

摘要

PROBLEM TO BE SOLVED: To decrease the process time of heat treatment required for a porous optical fiber preform. SOLUTION: Before a porous optical fiber preform 2 disposed in a furnace tube 9 is subjected to a required heat treatment, the whole body of the porous optical fiber preform 2 is preliminarily heated to a specified preheating temp. lower than the temp. of the required heat treatment. Then, in this state, the porous optical fiber preform 2 is subjected to the required heat treatment while the position in the optical fiber preform 2 heated from the preheated temp. to the temp. of the required heat treatment is moved along the longitudinal direction of the preform.