PURPOSE: To prevent the Ge contained in a side core layer appearing on the surface of the core layer, when the core layer is etched.
CONSTITUTION: A silica layer-forming burner 8 except a center core burner 3 and a side core burner 4 is employed in a reaction vessel 2 to form a silica layer 1c on the outer periphery of a porous side core layer 1b in a ratio of 1:≥1.4 between the outer diameter of the side core layer 1b and the outer diameter of the silica layer 1c. The core layer 1 obtained thus is dehydrated in an electric oven into a transparent glass layer. The silica layer 1c of the produced transparent glass part is etched, and a porous clad layer is formed on the outer periphery of the etched silica layer 1c, followed by dehydrating the porous clad layer into a transparent glass layer.
KUWABARA MASAHIDE
OGURA KUNIO
