PRODUCTION OF OPTICAL FIBER BASE MATERIAL

摘要

PROBLEM TO BE SOLVED: To obtain an optical fiber base material in good workability and in a good yield by uniformly controlling the temperature of a reaction oven main body, accumulating a clad portion on a starting core base material in the reaction oven and subsequently converting the obtained soot into sintered glass. SOLUTION: This method for producing an optical fiber base material comprises setting a core base material 3 welded to a dummy portion 11 in a reaction over main body 10, rotating the set core main material 3 with a rotation motor 7, charging oxygen gas, hydrogen gas and SiCl4 gas as a raw material into plural large oxyhydrogen flame burners 8 having large diameters, respectively, traversing the burners 8 in the longitudinal direction of the core base material 3 and simultaneously accumulating soot generated by the flame hydrolysis of the raw material gas. A jacket 1 for circulating a cooling medium is attached to the periphery of the reaction oven main body 10, and the cooling medium is circulated in the jacket. Thus, the temperature of a combustion gas is controlled at 50-120 deg.C to prevent the local thermal distortion of the reaction oven main body 10. The oxygen gas, hydrogen gas and the raw material gas can thereby be charged in large amounts, respectively, and the soot base material 4 can be accumulated at a high accumulation rate. The soot base material 4 is charged in a sintering oven and subsequently subjected to a dehydrative sintering glass- forming reaction to give an ingot in which foreign matters, bubbles, etc. are not recognized.