Method and apparatus of producing optical fiber preform

A method of producing optical fiber preform, the method comprising:

• preparing a flaming burner configured to include a glass source material gas discharge nozzle, a seal gas discharge nozzle disposed outside the glass source material gas discharge nozzle, a plurality of supporting gas discharge nozzles arranged separately from the seal gas discharge nozzle, and a flaming gas port disposed outside the seal gas discharge nozzle so as to include the supporting gas discharge nozzles, the supporting gas discharge nozzles having a small hole diameter;
• forming a deposited layer by depositing glass particles on a periphery of a target element in a deposition mode in which the glass particles are deposited on the periphery of the target element by performing traverse of the flaming burner two or more times in an axial direction of the rotated target element while burning a mixed gas containing a glass source material gas, a flaming gas, and a supporting gas by use of the flaming burner;
• maintaining a state where the supporting gas flows at a flow velocity greater than or equal to a flow velocity at which a nozzle end of the supporting gas discharge nozzles does not glow while maintaining a pilot burner by allowing the flaming gas to flow to the seal gas discharge nozzle after a seal gas is replaced with the flaming gas in a case where a mode is changed from the deposition mode to a non-deposition mode in which the glass particles are not deposited on the periphery of the target element;
• and
• replacing the flaming gas flowing to the flaming gas port with a purge gas.