Method, apparatus and burner for fabricating an optical fiber preform

An optical fiber preform fabrication burner for decomposing a glass raw material in a flame to synthesize fine glass particles, where raw material and flame-forming gases are flowed in a downstream direction to provide said fine glass particles, comprising:

• means defining an inner raw material supply orifice for supplying said glass raw material;
• means defining a plurality of flame forming orifices disposed around said raw material supply orifice concentrically for forming a plurality of flames;
• means defining an outer raw material supply orifice interposed between said plurality of flame forming orifices for supplying said glass material;
• the tip of one of said plurality of flame forming orifices, which is inside said raw material supply orifice, being located on the upstream side of the tip of the outer flame forming orifice outwardly surrounding said one flame forming orifice;
• each of said plurality of flame forming orifices comprising means defining a fuel gas supply orifice and means defining an oxygen-containing auxiliary gas supply orifice;
• and
• the tip of the inner raw material supply orifice being located on the upstream side of the tips of said combustible gas supply orifice and said auxiliary gas supply orifice of the flame forming orifice surrounding said inner raw material supply and the tip of the outer raw material supply orifice being located on the upstream side of the tips of said combustible gas supply orifice and said auxiliary gas supply orifice of the flame forming orifice surrounding said outer raw material supply.