Apparatus and method for manufacturing optical fiber preform

A method for manufacturing an optical fiber preform, the method comprising

• using a combustion burner including a glass source material gas discharge nozzle and two combustion gas ports that are adjacent to each other and are arranged in the vicinity of the glass source material gas discharge nozzle, the two combustion gas ports including:
• a combustion gas port A which includes a plurality of supporting gas discharge nozzles with a small diameter arranged so as to be close to the glass source material gas discharge nozzle;
• and a combustion gas port B which does not include the supporting gas discharge nozzle, burning a mixed gas including a glass source material gas from the glass source material gas discharge nozzle, a combustion gas from the combustion gas ports, and a supporting gas from the supporting gas discharge nozzle to deposit glass particles on a periphery of a target member, and
• at least one of:
• a step α of when a mode is changed from a deposition mode in which the glass particles are deposited on the periphery of the target member to a non-deposition mode in which the glass particles are not deposited on the periphery of the target member, changing a gas discharged from the combustion gas port A from the combustion gas to a purge gas, while maintaining a pilot light of the combustion burner with the combustion gas from the combustion gas port B and maintaining a flow rate of the supporting gas discharged from the supporting gas discharge nozzles of the combustion gas port A to be equal to or greater than a flow rate at which a nozzle tip of the supporting gas discharge nozzles does not glow;
• and
• a step β of, when the mode is changed from the non-deposition mode in which the glass particles are not deposited on the periphery of the target member to the deposition mode in which the glass particles are deposited on the periphery of the target member, changing a gas discharged from the combustion gas port A from a purge gas to the combustion gas, while maintaining a pilot light of the combustion burner with the combustion gas from the combustion gas port B and maintaining the flow rate of the supporting gas discharged from the supporting gas discharge nozzles of the combustion gas port A to be equal to or greater than the flow rate at which the nozzle tip of the supporting gas discharge nozzles does not glow.