Porous optical fiber base materials, optical fiber base materials and methods for producing them

Abstract

There is disclosed a method for producing a porous optical fiber base material comprising depositing fine glass powder on a rotating member, wherein pore size of the deposited fine glass powder is controlled, and preferably, mode of the pore size is controlled to be 0.1 to 1 &mgr;m, or wherein a total amount of absorbed H2O amount and OH group amount on the fine glass powder per square meter of fine glass powder surface area is controlled to be 3.5×10−5 to 7.5×10−5 g. Such porous optical fiber base materials have an improved weight of fine glass powder deposited on the member per batch, or an improved fine glass powder deposit efficiency, which may greatly contribute to improvement of production ability and reduction of production cost. Further, there is disclosed a method for producing a porous optical fiber base material comprising depositing fine glass powder on a rotating member, wherein, as for the deposited fine glass powder, pore volume of pores having a pore size of 10 &mgr;m or more is controlled to be 1% by volume or less relative to the total pore volume. Such a porous optical fiber base material can markedly decrease air bubbles in an optical fiber base material after the fusion vitrification.