METHOD FOR PRODUCING DOPING SILICA BODY

PROBLEM TO BE SOLVED: To provide a method for producing a silica body with impurities added. SOLUTION: A doping silica core region of a core rod for an optical fiber preform is protected from undesirable fluorine doping during the fluorine doping for an outer silica layer by selectively consolidating the core region before the fluorine doping. Soot in the core region is consolidated by a dopant in the core region before the soot in an outer non-doping region. This specific characteristic allows the whole core red to be heated before the fluorine doping to cause the selective consolidation.