Patent ID: 8839646

Claim:
A method for producing an optical fiber preform, comprising: a rod formation step of forming a glass rod composed of a silica glass containing an alkali metal element, the average concentration of the alkali metal element being 5 at·ppm or more; a heat treatment step of heat-treating the glass rod; a core part formation step of forming an alkali metal element-free silica glass layer having a chlorine concentration of 6000 at·ppm or more around the perimeter of the glass rod heat-treated in the heat treatment step to form a core part including the glass rod and the silica glass layer; and a cladding part formation step of forming around the perimeter of the core part a cladding part composed of a silica-based glass having a lower refractive index than the core part, wherein in the heat treatment step, the glass rod is heat-treated at a temperature higher than 800° C. and 1400° C. or lower.