A method of treating an optical fiber, comprising:
- preparing an optical fiber that comprises a core and a cladding surrounding the core and that is made of a silica-based glass;
- determining an exposure ambient temperature that causes the optical fiber to be subjected to a non-oxygen bridging atmosphere not including an oxygen bridging element by:
- estimating an amount of Non-Bridging Oxygen Hole Centers (NBOHC) in the entire optical fiber based on a correlation between an amount of NBOHC in the entire optical fiber corresponding to previously manufactured optical fibers and an amount of NBOHC in the core, and based on an estimated amount of NBOHC in the core;
- estimating an amount of the oxygen bridging element required for treating the NBOHC in the entire optical fiber based on the estimated amount of NBOHC in the entire optical fiber;
- determining a correlation between an exposure ambient temperature, an exposure time, and the amount of the oxygen bridging element in the optical fiber, based on a diffusion model of gaseous molecules of an oxygen bridging element supplied to the optical fiber;
- and
- then determining the exposure ambient temperature at which the optical fiber is subjected to the non-oxygen bridging atmosphere, based on the determined correlation, the exposure time, and the amount of oxygen bridging element in the optical fiber;
- exposing the optical fiber to a gas including an oxygen bridging element that is capable of treating the NBOHC 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
- subsequently treating the optical fiber by subjecting the optical fiber to the non-oxygen bridging atmosphere with the determined exposure ambient temperature and thereby diffusing the oxygen bridging element into the optical fiber;
- wherein the exposure time is estimated by:
- estimating an NBOHC absorption loss in the core at a wavelength of near 630 nm by obtaining transmission loss measurement data of the optical fiber before the exposing of the optical fiber;
- and
- determining the exposure time for the optical fiber based on a peak transmission loss from the estimating the NBOHC absorption loss and a correlation between the exposure time and the peak transmission loss at the wavelength of near 630 nm for a specific set of manufacturing conditions;
- wherein the estimating the NBOHC absorption loss comprises:
- externally fitting wavelength region data of the transmission loss measurement data, which avoids an absorption peak due to the NBOHC, at a wavelength region in which the absorption peak exists,
- determining a transmission loss at the absorption peak due to the NBOHC, and
- estimating the amount of NBOHC in the core based on the transmission loss at the absorption peak due to the NBOHC,
- wherein the estimating the amount of NBOHC in the core is based on the transmission loss measurement data, which is associated with a short-wavelength λ with respect to a transmission loss in which the wavelength λ of the optical fiber is less than or equal to 1000 nm is converted into λ−4, loss data of a wavelength region including a region other than a wavelength region in which λ−4 is 4 to 8 and including at least a region in which λ−4 is 2 to 3 that is subjected to linear approximation,
- wherein a difference between a transmission loss value of near 630 nm on an extension line of the linear approximation and a measured transmission loss value of near 630 nm is defined as a transmission loss due to the NBOHC, and
- wherein the amount of NBOHC in the core is estimated based on the transmission loss due to the NBOHC and a peak transmission loss of the core is determined due to the NBOHC.