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A Gift From God

Development of "Ultra Low Attenuation Optical Fiber", the Symbol of Fujikuraism

Phase.3 Fujikura Rush

An ultra low attenuation fiber that approaches the logical limit was accomplished. Even the world leader, the Bell Telephone Laboratory, took off their hats, praising it as "a gift from God."

Researchers from all over the world visited Fujikura upon its development of "0.47dB/km ultra low attenuation optical fiber." Thanks to them, Fujikura was able to gather a constant stream of cutting-edge information from around the world with little effort. This spurred Fujikura's research & development efforts like a "God of technology" that had come down to encourage the research staff. And then, there was another flurry.

First, there was the development of the "optical fiber with a silicon buffer layer" which added momentum to practical applications. This has become engrained in the standard specifications of Nippon Telegraph and Telephone Public Corporation and is also used widely across the world. Then followed the publication of the theoretical grounding of low attenuation optical fiber in the "thesis on the clarification of loss factors" (December 1976). At that time, there existed quite a lot of misunderstanding. The common understanding was that it might be due to impure substances contained that prevented loss from being reduced, and that loss might be reduced if better quality materials were used. We proved that what reduced loss depended not only on those but also on the method of drawing fibers or the matter of structure, namely the "manufacturing method of fiber," and published the way this could be easily determined. This thesis made a substantial contribution to the later evolution of optical fiber. Invitations to lecture at academic conference poured in, and the "Fujikura theory & method" became popular and in considerable demand.

The global achievements of Fujikura also stimulated the joint research with Nippon Telegraph and Telephone Public Corporation. Momentum increased to step away from Bell Telephone Laboratory's MCVD method and establish a manufacturing method unique to Japan. This was the theme of the joint research. Finally, in March 1977, we succeeded in the development of the VAD method (Vapor-phase Axial Deposition method). Although this VAD method had more economic advantages, the amount of the hydroxyl residue was more than that in the MCVD method and thus expected to generate more loss. Consequently, it was said that draining water was the largest breakthrough point.

Fujikura showed its true ability again, "draining" the VAD method. We developed a method that realizes almost perfect anhydration, obtained a patent and introduced a fiber that contained almost no water. Fujikura, furthermore, prevailed over competitors in research to identify, for example, what should be done to ensure fiber maintains a stable performance against the ambient environment?in other words, under what conditions does fiber become weak or loss increase? In order to demonstrate our achievements, Fujikura developed the "Unit cable containing piano wire." This was to exhibit full power at the on-site testing of Nippon Telegraph and Telephone Public Corporation that started the next year in 1978.

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