City of Light: The Story of Fiber Optics

230 CITY OF LIGHT
was selling fiber to many developing countries, including India, Brazil, Argentina,
Mexico, Thailand, and Indonesia. 11
Even undersea cable engineers, the most cautious of the traditionally conservative
telephone engineers, embraced fiber. Before TAT-8 was up and running
at 1.3 micrometers, they signed contracts for more submarine cables
operating at 1.55 micrometers. Satellite circuits were relegated to transmitting
the growing volume of data and other signals not sensitive to delays. It
seems years since I’ve recognized the delays of an overseas satellite circuit.
The Problem of the Future
This future has not been what the establishment expected. Thirty years ago,
Picturephone and the millimeter waveguide were the future of telecommunications.
The vision shifted continually. Fiber came and conquered, but the
logical compromise of graded-index fibers turned out to be a dead end. Stew
Miller looked back in retirement and wrote in the introduction to a massive
1988 book he edited on fiber optics, ‘‘Perhaps the least predicted trend in the
last six years is the rapidity of the movement to single-mode fibers as the
medium of choice.’’ 12 Yet that shift was a compellingly logical one, too, once
engineers solved the daunting but unglamorous problem of coupling light into
single-mode fibers. The huge capacity of single-mode fiber pipes gave phone
companies room for future upgrades without the high cost of installing new
fibers. Using a single type of fiber throughout the whole network greatly
simplified maintenance.
Miller was not an expressive man, but he must have been glad to see fibers
succeed. Little legacy remains from other projects that occupied his 40 years
at Bell Labs. Millimeter waveguides and hollow light pipes had gone down
the tubes. His pet brainchild, integrated optics, has remained in the laboratory
for decades. But fibers were a brilliant success. In February 1989, the Optical
Society of America gave him the John Tyndall award for his contributions to
fiber optics. He died a year later in New Jersey at 71.
As Miller’s career shows, predicting the course of technology is no easy
task. Fatal flaws can lurk deep inside the hearts of bright ideas. New concepts
can outflank logical extrapolations of established knowledge, as the optical
fiber beat out the millimeter waveguide. A pure and elegant idea can trump
a technological compromise, as single-mode fiber proved far superior to
graded-index fiber. Experts enamored of their own approaches can completely
miss other possibilities, as Bell did when it ignored Charles Kao to concentrate
on hollow optical waveguides. And as Kao showed when he asked about glass
transmission, fundamental limits can be far more important than the state of
the art.
Yet you can twist those conclusions the other way by citing other examples.
Many fundamental limits are out of reach; many technological compromises
yield workable and economic products. Most mistaken forecasts of
trends in fiber technology made eminent sense at the time. Single-mode fiber