City of Light: The Story of Fiber Optics

BREAKTHROUGH 137
moved a baffle, the vacuum sucked air down the tube, spreading soot along
the inside surface.
The vacuum didn’t survive the nasty mixture of chemicals in the burner
exhaust, but it did achieve a breakthrough. The pair had learned how to
deposit glass inside a tube. Making uniform deposits required air-flow equipment
more precise than an old vacuum cleaner, but that was fine tuning.
They had developed an important new way to make a fiber preform, called
inside vapor deposition because it deposited the core glass on the inside of the
tube that became the cladding. The next step was to heat the preform, melt
the fluffy soot to coat the inside of the tube, and draw it out into a fiber.
Keck hauled the preform to Zimar’s lab, where he and Zimar mounted it
vertically, with the lower end in the furnace. The heat first melted the soot,
then softened the whole tube. Pulling on the bottom stretched the glass into
a fiber, closing the central hole. After Zimar drew a short length of fiber, Keck
snipped off a bit and hustled back to his laboratory to measure its core diameter
through a microscope. Then he went back to Zimar’s lab and adjusted
temperature and drawing speed to get closer to the desired diameter.
They carried out a series of experiments, making preforms and drawing
fibers from them in various ways. They carefully measured fiber properties to
see what happened as they changed things. Between experiments, Keck and
Schultz analyzed their findings and devised the next round of trials. It was a
pattern common to every lab trying to make low-loss fibers: design an experiment,
perform it, measure the results, deduce what happened, then design a
new experiment. They cycled through the process again and again. The results
didn’t always improve, but like every experimenter they sought to learn
something each time. Maurer strategized, Zimar drew fibers, and Kapron and
others contributed ideas. Bit by bit, the Corning team worked out the details
of making single-mode fibers.
Working Out the Process
Corning didn’t reveal much to the outside world, although Roberts paid a
visit and Maurer spoke with some British Post Office researchers. However,
Maurer had progress to share whenever time came to report to Armistead.
Lucy went on the road, hunting outside support for Corning’s fiber research
and help with other aspects of fiber communications. AT&T showed no interest,
so he went overseas. He lured money from a few makers of copper
cable—Siemens in Germany, Pirelli in Italy, and BICC in England. He worked
out agreements with French government labs and with Furukawa Cable in
Japan. It helped keep the project going. 19
Through the hot, humid summer of 1969, they drew fibers in Zimar’s
laboratory. ‘‘It was hotter than Hades’’ with the furnace running, Keck recalls.
20 They wound fibers of various sizes onto 2-foot (60-centimeter) diameter
cardboard drums used to ship raw materials to the glass lab, a step
beyond oatmeal cartons. The drums spun about once every two seconds,