PURPOSE: To obtain a parent material for single mode optical fiber with low loss, by forming a porous glass layer for a cylindrical core by using D2-O2 flame, depositing fine particles of SiO2 on its outer periphery, and making the layer into transparent glass in an atmosphere containing a fluoride.
CONSTITUTION: Gaseous-phase raw material SiCl4 is subjected to flame hydrolysis reaction by the use of D2-O2 flame to form fine particles of SiO2, which is jetted towards a target and deposited on it to form a porous glass layer for a cylindrical core in such a way that the density is ≥2.0g/cm3. Fine particles of SiO2 formed by flame hydrolysis reaction of SiCl4 by H2-O2 flame is piled on the outer periphery of the porous glass layer, to form a porous glass layer for clad having 0.2W0.3g/cm2 density. The porous parent material is supported in an atmosphere containing a fluorine under heating, and made into transparent glass, to give a parent material for single mode optical fiber.
ORIMO KATSUMI
OGURA KUNIO
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