City of Light: The Story of Fiber Optics

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