More than 60 percent of today’s optical fibers are made with a mass production process called vapor-phase axial deposition (VAD). It was invented in 1977 by IEEE Life Fellow Tatsuo Izawa, a researcher at Nippon Telegraph and Telephone Corp. (NTT), in Tokyo.
A DELICATE PROCESS
Optical fibers are used to transmit light for all manner of digital telecommunications over longer distances and with higher bandwidths than copper cables. Individual optical fibers are made of glass about an eighth of a millimeter wide—about the width of a human hair. Manufacturing begins with a solid glass cylinder, known as a preform. The preform is lowered into a fiber-drawing tower, then heated to 1,900 °C until the tip begins to melt and drip. The drip is then made to form a long continuous thread, or fiber. As it cools, the fiber is wound around a spool and placed in a protective tube. Later the fibers are collected into multifiber cables.
As fiber-optic networks expanded, these cables had to cover much longer distances, and manufacturers struggled to produce enough optical fibers to meet the demand. Today, fibers as long as 100 kilometers are not uncommon.
In 1975, four Japanese wire and cable manufacturers—Fujikura, Furukawa Electric, NTT, and Sumitomo Electric—partnered to figure out how to mass-produce optical fibers. Two years later, Izawa came up with a way to produce longer fiber-optic threads. In his method, fine glass particles were synthesized and deposited onto a rod of silica. Gas vapors were then conducted to the inside of the silica rod in a lathe—a machine tool that rotates the rod on its axis. As the lathe turns, a torch is moved up and down the outside of the tube, causing silicon dioxide and germanium dioxide deposits on the inside of the tube to fuse together and form glass.
Izawa called this process vapor-phase axial deposition. It was more suitable for mass production than earlier methods because the rotating silica rod caused glass particles to grow and expand away from the center, forming a larger preform to begin with and hence longer threads. The process became commercially available in 1983 and is still used to make more than half of today’s optical fibers.
A ceremony honoring the new IEEE Milestone was held on 21 May. A plaque was mounted on the wall of the reception area of NTT Research Laboratories, in Tokyo. It reads:
In 1977, Dr. Tatsuo Izawa of Nippon Telegraph and Telephone Corp. (NTT) invented the vapor-phase axial deposition (VAD) method suitable for the mass production of optical fiber. NTT, Furukawa Electric, Sumitomo Electric, and Fujikura collaboratively investigated the fabrication process. The technology successfully shifted from research and development to commercialization. The VAD method contributed greatly to the construction of optical-fiber networks.