A gift from God

The completion of an extremely low-loss fiber approaching the theoretical limit. Even the world-renowned Bell Labs praised it as a "gift from God" and bowed their heads in admiration at the miraculous achievement.

Researchers from around the world visit Fujikura to study the development of "extremely low-loss Optcal Fiber with 0.47 dB/km." These visits to Fujikura allow cutting-edge information from around the world to be gathered effortlessly. Thus, as if the "god of technology" had descended upon the heads of Fujikura's researchers, research and development gains momentum. And an even stronger tailwind begins to blow.

First, he developed "Optcal Fiber with a silicon buffer layer," which gave a boost to practical use. This became the standard specification of Nippon Telegraph and Telephone Public Corporation and came to be widely used internationally. He then published the theoretical basis for low-loss Optcal Fiber in "A paper on elucidating the causes of loss" (December 1976). At the time, many people had misconceptions about fiber. The common understanding was that the reason loss did not decrease was because there were a lot of impurities, and that loss would decrease if better quality materials were used. However, he proved that loss reduction was also determined by issues of drawing and structure, in other words, the "manufacturing method of the fiber," and published a method to understand this in an easy-to-understand way. This paper made a huge contribution to the subsequent evolution of Optcal Fiber. He received invitations to give lectures at academic conferences around the world, and "Fujikura Theory and Method" was in high demand.

VAD

Fujikura's world-class achievement thus gave impetus to joint research with Nippon Telegraph and Telephone Public Corporation. There was a growing feeling that it was time to break away from Bell Labs' method (MCVD method) and establish a manufacturing method unique to Japan, and this was made the theme of the joint research. In March 1977, they succeeded in developing the VAD method (vapor phase axial deposition method). Although the VAD method was an economically advantageous method, it was predicted that the amount of residual hydroxyl groups would be greater than in the MCVD method, and that there would be large losses. Therefore, removing the water was considered to be the biggest breakthrough point.

Fujikura also demonstrated its capabilities in "water removal" using the VAD method. It developed a method for almost complete dehydration, obtained a patent for it, and announced a fiber that actually contained almost no water. Fujikura was also a leader in research into "how to ensure that fiber maintains stable performance regardless of the surrounding environment...in other words, under what conditions does fiber become weak or loss increase?" and as proof of its success, it developed a "unit cable with piano wires." This would prove extremely effective in the field tests by Nippon Telegraph and Telephone Public Corporation that began the following year in 1978.