City of Light: The Story of Fiber Optics

68 CITY OF LIGHT
A Problem with Image Scramblers
When progress stalled at American Optical in the fall of 1956, the company
started looking for alternatives. Lee Upton, an AO glass specialist, had worked
in a plant that collapsed glass tubes onto electrical components to insulate
them, and he suggested adapting that idea to making fibers. In October, Steve
MacNeille brought in an outside consultant, a retired MIT professor named
Frederick H. Norton. Norton first proposed coating bare fibers with molten
glass, but later also suggested a rod-in-tube approach. 32
Norton also borrowed an idea from ancient makers of miniature glass
portraits. They stacked rods of colored glass in the desired pattern, heated the
assembly until the edges of the rods melted together, and stretched the bundle
into a single fused cylinder. Slicing the fused rod like a salami yielded disks
bearing portraits or abstract patterns. The method is called millefiori, for
‘‘thousand flowers,’’ and is still used today to make paperweights. Norton
realized that many clad fibers could be assembled together in the same way
and stretched into a rigid ‘‘multifiber.’’ This avoided the need to draw many
fine, separate fibers and assemble them into a bundle, because a single operation
stretched all the fibers at once. The trade-off was the loss of flexibility;
the many fibers emerged fused together in a solid rod. That rigidity made
them useless for gastroscopes but was fine for image scramblers, which were
much fatter and thus needed many more fibers.
It took Hicks time to assemble the equipment he needed to test the new
ideas. The big company’s advantage in resources was more than offset by its
ponderous bureaucracy. By November, Hicks had found thin-walled tubing
but not rods of high-index glass suitable for the core of the fiber. American
Optical had the right kind of glass, but it came in rectangular blocks, and
Hicks couldn’t persuade anyone at AO to grind them down to the cylindrical
shape that he needed. He finally ordered polished cylinders from another company.
While he waited for the rods to arrive, he hand-built a glass-melting
furnace in the AO shop, because he couldn’t get the company to pay its
machinists to do the job for him. It was January 1957 before Hicks had the
equipment to try Upton’s approach to drawing glass-clad fiber.
By this time, development of the Todd-AO optical system was winding
down, and American Optical was shifting some of those engineers to the fiber
project. However, they and Hicks faced tough problems debugging fiber production.
Contaminants from mechanical polishing remained at the corecladding
interface, causing troublesome losses that made the glass-clad AO
fibers poorer than those Curtiss drew from fire-polished rods. These problems
helped keep plastic-clad fibers alive at American Optical; although they transmitted
less light than good glass-clad fibers, loss was not as critical for short
image scramblers as it was for longer gastroscopes.
Hicks’s group made a demonstration scrambler by looping single fibers
many times around a drum, gluing one region, and sawing through that
spot. After they showed that the flexible bundle could transmit an image, they
scrambled the loose fibers in the middle, glued them, and sawed through that