City of Light: The Story of Fiber Optics

A DEMONSTRATION FOR THE QUEEN 171
potentially vast transmission capacity. However, optical fibers were looking
better, and he conceded that they ‘‘may satisfy a demand for much smaller
capacities much sooner.’’ 71 By the time Kompfner retired at 64 the following
summer, hollow optical waveguides were essentially dead. 72 Research management
changed as John Pierce also retired to join the faculty at Caltech.
A New Process Explodes at Bell Labs
Bell finally started to make progress on fiber fabrication in the winter of 1972,
after France published Corning’s application for a fiber patent. 73 Bill French,
who had worked with Dave Pearson at Murray Hill, saw a translation and
wondered if a similar process, chemical vapor deposition, would work for
fibers. He suggested the idea to another Murray Hill scientist, John Mac-
Chesney, who had used chemical vapor deposition to make other types of
silica.
To see if it would work, they flowed silicon tetrachloride, titanium tetrachloride,
and oxygen through a hot glass tube. The gases reacted, depositing
glassy soot inside the tube, which they then melted and drew into a fiber.
‘‘The experiment worked the first time, largely for the wrong reasons, but
that didn’t matter,’’ MacChesney recalls. 74 Further experiments reduced fiber
loss. 75
Another Bell glass specialist, Ray Jaeger, realized that a dash of boron
would reduce silica’s refractive index. That boron-doped glass could serve as
a low-index cladding on a core of nearly pure silica, avoiding the need to add
dopants to the light-carrying core. MacChesney used that trick to make fibers
with loss of only 5.5 decibels per kilometer, a breakthrough for Bell. 76,77 By
1974 they reduced loss to four decibels per kilometer at 900 nanometers,
and to just over two decibels at 1060 nanometers. 78
Refining the process took time and countless experiments. MacChesney
veritably mass-produced preforms, which he sent to another lab that drew a
few hundred meters of fiber for measurements. Sometimes he let deposition
run unattended overnight; it speeded research but was risky with volatile
chemicals. One Saturday night an oxygen line broke, fueling a fire so hot it
melted window glass and sealed the lab door shut. Firemen needed much
time and even more water to quench the inferno, which devastated Mac-
Chesney’s lab and flooded one Paul Lazay ran downstairs. 79
It was the second lab MacChesney melted, but the fire didn’t diminish his
stature at Bell. It was the sort of occupational hazard that comes with hightemperature
chemistry; Southampton also burned down a lab. 80 The occasional
fire was a small price to pay for a process that worked, and Mac-
Chesney’s did. It became AT&T’s standard way to make fiber.
Others developed their own vapor deposition processes. In England, Southampton
doped fiber cores with phosphorus to make fibers with minimum loss
of 2.7 decibels per kilometer at 830 nanometers. 81 There was room for some