City of Light: The Story of Fiber Optics

122 CITY OF LIGHT
A Budgetary Windfall
As Charles Kao preached the gospel of fiber optics, Dollis Hill blundered into
a bit of budgetary good fortune. American management consultants told the
Post Office that its telephone division wasn’t spending enough money on
research. That may seem preposterous in an era of corporate downsizing, but
the 1960s were flush with technological optimism. Management allocated an
extra £12 million for research. ‘‘Goodness knows how we are going to spend
it all,’’ Tillman confessed to Richard Dyott when he started work at Dollis Hill
on March 1, 1967. 26
The extra money gave Bray and Tillman the luxury of investing in wild
schemes, and the realists at Dollis Hill counted fiber optics among the wildest.
It would be nice to have a flexible waveguide to thread through convoluted
urban underground ducts, but it was not a pressing need. Tower-to-tower
microwave transmission worked well and avoided messy construction in developed
areas. Engineers saw millimeter waveguides as ‘‘the next logical step
from microwave towers for long-distance stuff.’’ 27 Fiber-optic communications
was a long shot, worth a small bet from the suddenly flush research budget
because it might solve some annoying problems.
Roberts gathered a small team to work on fibers and glass, and they collected
all the optical equipment they could find. He put George Newns in
charge of developing ultrapure glasses with low loss. Dyott headed a group
devoted to making fibers and studying their properties. Hugh Daglish was to
develop optical techniques to measure fiber properties, a critical concern for
a stickler like Roberts. Most of the team came from electronics or millimeter
waveguide development and were surprised to be assigned to the unfamiliar
world of light. 28
They started with minimal resources. Dyott sealed a thin rod of tungsten
glass inside a thick Pyrex tube, which had a lower refractive index, to make
a preform that could be stretched into single-mode fiber. He had no fiberdrawing
equipment, but his lab was long and narrow, so Dyott improvised.
‘‘We heated up the preform at one end of the lab and Jacqueline Viveash,
who by chance had a pair of tennis shoes handy, raced to the other end
carrying the end of the preform in a pair of tongs to the cry of ‘Run, Jacquie,
run.’ ’’ he recalls. 29 Jacquie’s dash yielded a fiber that carried a single mode
at the red helium-neon wavelength. Dyott was pleasantly surprised to find
that the fiber collected more than half the laser light focused into it through
a microscope objective. Unfortunately, the light didn’t go very far. The loss
was 30 decibels per meter—so high that less than 0.1 percent of the light
that entered the fiber on one side of a desk would emerge on the other.
Dyott also borrowed time on a university computer to solve the complex
equations that Snitzer had formulated for single-mode fiber. It was not an
easy task because input had to be submitted to the computer center punched
on five-hole paper tape, and a single mispunched hole could stop the program,
yielding only a cryptic error message hours later. Yet the results helped explain
how pulses spread along fibers.