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