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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A CRITICAL INSIGHT 47<br />
Born at the close <strong>of</strong> the nineteenth century, both men were in their early<br />
fifties, near the peaks <strong>of</strong> eminent careers. Although not close friends, they<br />
shared the camaraderie <strong>of</strong> long-time workers in the same small field. When<br />
van Heel toured American optics labs, it was natural for O’Brien to invite<br />
him for dinner at his large two-story house, build just before World War I<br />
and tastefully fitted with mahogany furniture and heirloom oriental rugs. 2<br />
<strong>The</strong>y expected to relax and chat about optics in postwar Europe and America.<br />
<strong>The</strong> Cold War military research that deeply involved both men also was<br />
on the agenda. <strong>The</strong> West was in a technological arms race with the Soviet<br />
Union, still ruled by Josef Stalin. Holland was trying to rebuild a submarine<br />
fleet that had been among the world’s largest before World War II, and they<br />
wanted better periscopes. <strong>The</strong> German companies that had supplied Holland<br />
before the war lay in ruins; America and Britain wanted to keep their latest<br />
technology for their own subs. Knowing how curved glass or plastic rods<br />
could carry light, van Heel thought a bundle <strong>of</strong> thin fibers might relay the<br />
image in a periscope. 3<br />
Van Heel’s assistant Willem Brouwer had suggested that fiber bundles<br />
could scramble images as well as transmit them—an idea that excited the<br />
Dutch security agency. As for image transmission, the fibers first would be<br />
aligned to form the same pattern at both ends. <strong>The</strong> trick was to scramble the<br />
fibers in the middle, fix them in place with glue, then cut the bundle in half<br />
at the scrambled point. Each half would convert an image into an unintelligible<br />
pattern, but mating the severed halves properly would reassemble<br />
the image. You could encode a message by taking a photograph through one<br />
half <strong>of</strong> a scrambler, because only the person with the matching half could<br />
decode it.<br />
<strong>The</strong> ideas sounded good, but van Heel was making little progress. <strong>The</strong><br />
Dutch government asked its American allies to recommend a well-qualified<br />
and highly cleared US scientist who could help. 4 American <strong>of</strong>ficials picked<br />
O’Brien, whose work on military optics during the war had earned him the<br />
Medal for Merit, the nation’s highest civilian award, from President Harry<br />
Truman. 5 It was a singularly prescient choice.<br />
Van Heel explained that bare glass fibers didn’t work well. If two fibers<br />
touched, light leaked between them because total internal reflection didn’t<br />
work. <strong>The</strong> fiber surface scratched easily, causing even more losses. Plastic<br />
fibers suffered the same problems. Seeking an alternative to total internal<br />
reflection, van Heel coated fibers with a reflective silver film. Yet almost no<br />
light emerged from the bundle <strong>of</strong> silver-coated fibers he showed to O’Brien. 6<br />
O’Brien was surprised van Heel was working on light guides, but was not<br />
surprised his approach didn’t work. <strong>The</strong> American was studying single fibers<br />
himself and knew metal coatings would not work. A shiny metal surface<br />
always absorbs a little incident light, and losses build up with each reflection.<br />
Bounce light 100 times <strong>of</strong>f a 99 percent reflective surface, and only 36.6<br />
percent <strong>of</strong> the light remains; after 1000 reflections, only 0.0043 percent is<br />
left. You might think so many reflections unlikely, but the thinner the fiber,<br />
the more times light bounces <strong>of</strong>f its walls—and you need thin fibers to carry