OPTICAL FIBER PREFORM PRODUCING METHOD, OPTICAL FIBER PRODUCING METHOD, AND OPTICAL FIBER

摘要

A method for producing a preform of an optical fiber having a complex structure with high precision, a method for producing an optical fiber, and an optical fiber are disclosed. The method for producing a preform of an optical fiber comprising a center core portion disposed in the center of the optical fiber and having an index of refraction the maximum value of which is Nc, a depressed portion disposed outside the center core portion and at least having an index of refraction the minimum value of which is Nd, a ring portion having an index of refraction the minimum value of which is Nr, and an outer cladding layer having an index of refraction the maximum value of which is No, the relationship between the indexes of refraction being Nc >= Nr > No > Nd. The method comprises a glass rod producing step of inserting a rod including at least the center core portion into a pipe including at least the depressed portion and integrating them into one piece by collapsing to produce a glass rod, a glass pipe producing step of producing a glass pipe having a ring portion, and an integrating step of inserting the glass rod into the glass pipe and then integrating them into one piece by collapsing to produce a glass body.