METHOD FOR MANUFACTURING PREFORM FOR OPTICAL WAVEGUIDE

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing a preform for an optical waveguide to easily manufacture an optical waveguide. SOLUTION: The method for manufacturing a preform for an optical waveguide essentially comprising a quartz glass doped with nitrogen includes a step of supplying a mixture 25 of molecular gas effective substances containing nitrogen, oxygen and silicon atoms into a substrate tube 24, a step of exciting microwave discharge 27 in the mixture, and a step of depositing the reaction product produced in the mixture on the inner surface of the substrate tube 24. The molecular gas effective substances supplied into the substrate tube 24 is prepared by mixing in such a manner that less than five oxygen atoms are deposited on every silicon atom and that more than one nitrogen atoms are deposited in every 1000 oxygen atoms.