Patent ID: 8839645

Claim:
A method of manufacturing an optical fiber base material, comprising: forming a porous glass base material by depositing glass particles; providing a vessel at least partly made of quartz glass which contains an aluminum concentration equal to or less than 0.01 ppm; introducing dehydration reaction gas and inert gas into the vessel; heating a portion made of quartz glass which contains an aluminum concentration equal to or less than 0.01 ppm in the vessel containing the dehydration reaction gas and the inert gas; and inserting the porous glass base material into the heated vessel to dehydrate and sinter the porous glass base material, wherein the aluminum impurity concentration of less than 0.01 ppm is selected so that the optical fiber base material is capable of reducing the transmission loss at a wavelength equal to and shorter than 1310 nm such that a corresponding transmission loss is less than 0.34 db/km, and wherein the step of providing the vessel comprises providing a vessel having a thickness such that a total amount of time over which the vessel is subjected to a temperature exceeding 1,400 degrees Celsius is within a time period over which a glass layer remains in a depthwise direction in at least a part of the portion made of quartz glass which contains an aluminum concentration equal to or less than 0.01 ppm in the vessel and the time period is calculated by multiplying a thickness (mm) of the quartz glass which contains an aluminum concentration equal to or less than 0.01 ppm in the vessel by 1,500 hours.