Abstract: One embodiment provides a porous glass body which is obtained by depositing plural deposited layers of glass fine particles on a starting material in a layered manner by relatively reciprocating a burner for glass-fine-particle synthesis and the starting material. In the porous glass body, a porosity in a layer at the deposited layers falls within a range of 40% to 90%, and the porosity in the layer decreases from a central side toward an outer side in a radial direction thereof.

Abstract: One embodiment provides a porous glass body which is obtained by depositing plural deposited layers of glass fine particles on a starting material in a layered manner by relatively reciprocating a burner for glass-fine-particle synthesis and the starting material. In the porous glass body, a porosity in a layer at the deposited layers falls within a range of 40% to 90%, and the porosity in the layer decreases from a central side toward an outer side in a radial direction thereof.

Abstract: According to one embodiment, there is provided a method of manufacturing a glass preform, including: obtaining a glass-fine-particle deposit by a VAD process; and heating the obtained glass-fine-particle deposit at a high temperature, thereby manufacturing a transparent glass preform, wherein, while depositing glass fine particles, in addition to monitoring a deposition shape of the glass-fine-particle deposit and controlling a pull-up rate of the glass-fine-particle deposit, there is controlled at least any of: flow rates of glass starting gases to be charged into glass-fine-particle producing burners; flow rates of flame forming gases to be charged into the glass-fine-particle producing burners; and positions of the glass-fine-particle producing burners relative to the glass-fine-particle deposit, so that the deposition shape may become a target shape, and wherein the deposition of the glass fine particles is stopped in a case where the deposition shape deviates from the target shape.