Patent ID: 6892019

Claim:
A method of making an optical fiber preform comprising: a synthesizing step of depositing a glass fine particle onto an outer periphery of a core preform including at least a core region, so as to synthesize a glass fine particle layer to become the outermost cladding layer in one or a plurality of layers of cladding in a cladding region disposed at an outer periphery of said core region; a dehydrating step of dehydrating said synthesized glass fine particle layer upon heating; and a consolidating step of consolidating said dehydrated glass fine particle layer upon heating so as to form said outermost cladding layer, thus forming an optical fiber preform having said core region and said cladding region having said one or plurality of layers of cladding; wherein, before consolidating said glass fine particle layer upon heating, doping said glass fine particle layer with fluorine and eliminating a part of doped fluorine from an outer peripheral part including an outer periphery thereof.