Method of producing optical fiber preform and optical fiber

A method of producing an optical fiber, the method comprising drawing an optical fiber preform produced by a method of producing an optical fiber preform, the method of producing an optical fiber preform including:

• a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion;
• an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal around the silica glass body such that the alkali-metal-doped silica glass body contacts the silica glass body, wherein the alkali-metal-doped silica glass body is formed by:
• synthesizing an alkali-metal-doped silica soot doped with the alkali metal by using the outside vapor deposition (OVD) method, and
• a step of vitrifying the alkali-metal-doped silica soot such that a dehydration step in a chlorine-based gas atmosphere is not performed in the vitrification step, but only a sintering step as heat treatment in a non-chlorine-based atmosphere is performed;
• a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment and
• after the diffusing, a grinding and removing step of removing the alkali-metal-doped silica glass body by grinding, wherein:
• the silica glass body forming step comprises forming a silica glass rod having a first outer diameter,
• the alkali-metal-doped silica glass body forming step comprises forming an alkali-metal-doped silica glass body having a second outer diameter, and
• the grinding and removing step comprises removing the entire alkali-metal-doped silica glass body and an outer portion of the silica glass rod such that a remaining portion of the silica glass rod has a third outer diameter which is less than the first outer diameter.