In 1966, Kao proposed that it would be possible to make a low-loss optical fiber using impurity-free silica glass (SiO2). (1) After subsequent technological develop-ments, a low loss of 17 dB/km was demonstrated by Keck et al. Losses can be introduced by various means such as intrinsic material absorption, scattering, bending, connector loss and more. It traces OFC's. Development of Optical Fiber Communication Univ. 1980). We have been producing pure-silica core fibers that enable low-loss transmission since as early as 1980s, contributing to the development of submarine optical cable networks through continuous reduction in transmission loss and nonlinearity of fiber. We have succeeded in further reducing the.