PURPOSE: To prevent the contamination of recovered soot with impurities, by using an exhaustion pipe and a dry dust-collector made of a silicon-based material, and collecting the soot failed to deposit on the porous preform and exhausted from a bell-jar.
CONSTITUTION: In a vapor-phase axial deposition process (VAD process), the soot composed of fine particles of metallic oxide, etc. synthesized by the flame hydrolysis reaction in a synthetic torch 2 is exhausted through the exhaustion pipe 4 from the bell-jar 1 without depositing to the porous glass preform 3. The exhausted soot is collected by a dry dust-collector 5. The exhaustion pipe 4 and the dust-collector 5 are made of quartz, a material coated with quartz, or a material coated with metallic silicon. Soot free from impurities can be recovered by this recovering process.
ORIMO KATSUMI
KAWAZOE HIDEYO
IINO AKIRA
