METHOD FOR EVALUATING LOSS OF SINGLE MODE OPTICAL FIBER AND SINGLE MODE OPTICAL FIBER

摘要

PROBLEM TO BE SOLVED: To provide a method for evaluating the loss of a single mode optical fiber in a wavelength region of 1380 nm band and to provide a single mode optical fiber in which increase of loss due to diffusion of hydrogen can be reduced using that method for evaluating the loss. SOLUTION: A quartz rod comprising a core 1 and a first clad 2 is applied externally with microparticles of SiO2 to produce a glass preform in which a second clad 3 is formed and then the glass preforms are spun to produce an optical fiber. When an increase of loss in the wavelength of 630 nm band caused by bonding defect of silicon and oxygen in the quartz glass is limited to 4 dB/km or less, an increase of loss in the wavelength of 1380 nm band caused by the diffusion of oxygen into the quartz glass can be limited to 0.1 dB/km or less.