PURPOSE: To reduce the cost of a device and produce a preform for an optical fiber with a high productivity by subjecting a porous preform to hydration and transparent vitrification while supporting a supporting member inserted in a hole part formed at one end part of the porous preform.
CONSTITUTION: A seal tape 13 is wrapped around a joining area of a rubber mold for molding 11 and an under cap 12. A granulated powder 14 of silica powder is packed into this rubber mold 11, and after attaching an upper cap 15, the seal tape 13 is wrapped around the joining area of the rubber mold 11 and the upper cap 15. Then, after pressure-molding this rubber mold 11, a porous preform 16 is taken out. A through hole 17 passing through the center in a radial direction is formed at one end part of the preform 16, and a supporting member 18 such as a string made of a high purity carbon which withstand to high temp. chlorine atmosphere is attached. While supporting surely the preform 16 by this supporting member 18, the preform is subjected to defatting treatment under an oxygen-containing nitrogen atmosphere, dehydration and purification, then subjected to transparent verification.
SATO TSUGIO
YOSHIDA KAZUAKI
Next Patent: PRODUCTION OF PREFORM FOR OPTICAL FIBER