Patent ID: 8356494

Claim:
A process for producing a porous quartz glass body, comprising: hydrolyzing a metal dopant precursor and an SiO 2 precursor in a flame of a burner to form glass fine particles; and growing the glass fine particles on a base material, wherein the burner has at least two nozzles comprising a first nozzle and a second nozzle, and the hydrolyzing comprises feeding a first gas through the first nozzle and feeding a second gas through the second nozzle, the first gas comprises a mixed gas comprising (A) a metal dopant precursor gas, (B) an SiO 2 precursor gas, (C) one gas of H 2 and O 2 , and (D) one or more gases selected from the group consisting of a rare gas, N 2 , CO 2 , a hydrogen halide and H 2 O, the one or more gas gases (D) are included in the mixed gas in an amount of from 5 to 70 mol %, and the second gas comprises (E) one gas of H 2 and O 2 which is different from the gas (C).