Method of processing optical fiber and method of estimating therefor

A method of processing an optical fiber, comprising:

• a preparation step of preparing an optical fiber that comprises a core and a cladding surrounding the core and that is made of a silica-based glass;
• a determination step of determining at least an ambient temperature of conditions of a diffusion treatment that causing the optical fiber to be subjected to an non-oxygen bridging atmosphere not including an oxygen bridging element, the determination step comprising:
• a first step of estimating an amount of Non-Bridging Oxygen Hole Centers in the entire optical fiber and estimating an amount of the oxygen bridging element required for processing the Non-Bridging Oxygen Hole Centers in the entire optical fiber;
• a second step of determining correlation that is based on a diffusion model of gaseous molecules of an oxygen bridging element, is related to the oxygen bridging element supplied to the optical fiber, and is between an exposure ambient temperature at which the optical fiber is subjected to the non-oxygen bridging atmosphere, an exposure time at which the optical fiber is subjected to the non-oxygen bridging atmosphere in an exposure period in which the optical fiber is subjected to the non-oxygen bridging atmosphere, and the amount of the oxygen bridging element in the optical fiber;
• and
• a third step of determining, based on the correlation determined by the second step, the exposure ambient temperature at which the optical fiber is subjected to the non-oxygen bridging atmosphere;
• an exposure step of exposing the optical fiber to a gas including an oxygen bridging element that is capable of processing the Non-Bridging Oxygen Hole Centers by being bonded to a non-bridging oxygen in the optical fiber, and causing the oxygen bridging element to infiltrate into the optical fiber;
• and
• a diffusion step of subsequently causing the optical fiber to be subjected to the non-oxygen bridging atmosphere in the exposure ambient temperature which is determined by the third step of the determination step and at which the optical fiber is subjected to the non-oxygen bridging atmosphere, and thereby diffusing the oxygen bridging element into the optical fiber.