DETECTION OF CRACKING OF OVEN CORE TUBE IN PROCESS FOR SINTERING OPTICAL FIBER BASE MATERIAL AND PRODUCTION OF OPTICAL FIBER BASE MATERIAL

摘要

PROBLEM TO BE SOLVED: To minimize the contamination of an optical fiber base material with impurities by always measuring the concentration of leaked He in a gas in an electric oven in a process for sintering the optical fiber base material and subsequently judging that a crack is generated in an oven core tube, when the concentration of the leaked He reaches a prescribed value or larger. ;SOLUTION: This device for sintering an optical fiber base material is provided with an oven core tube 3 for receiving a soot 2 (optical fiber base material) supported on a support bar 1 and with an electric oven 5 which has a heater 4 disposed on the outer periphery of the oven core tube 3 and whose inner space is filled with a sealing N₂ gas atmosphere. He gas, Cl₂ gas, etc. are charged from the lower gas-charging port 6 of the oven core tube 3 and subsequently discharged from the upper gas-discharging port 7. A He leak detector 10 for sucking the gas from the electric oven 5 is further disposed, and the concentration of leaked He is always measured. The generation of a crack in the oven core tube is judged, when the concentration of the leaked He reaches a prescribed value or larger. The sintering of the optical fiber base material is always carried out in a state where the concentration of the leaked He is smaller than the prescribed value. Thus, the optical fiber base material having a high quality is obtained.;COPYRIGHT: (C)1999,JPO