City of Light: The Story of Fiber Optics

THE LASER STIMULATES THE EMISSION OF NEW IDEAS 95
transmission medium; the eye could see it was clear, and it carried radio and
microwave signals easily.
Experiments soon revealed it wasn’t quite as simple as pointing the pencilthin
laser beam at a distant target. A couple of Bell Labs engineers hauled an
early ruby laser to the top of a microwave tower at Murray Hill, New Jersey,
and aimed it at the Holmdel lab 25 miles (40 kilometers) away, where a third
engineer watched a movie screen for signs of the red pulses. They hooked
up phone lines, and the two in the tower phoned their partner in Holmdel
each time they fired the laser. ‘‘He didn’t see the pulse very often,’’ recalls
one. 14
Helium-neon lasers followed as soon as they were available. Bell put one
on the roof of its main development building in Holmdel and another atop
the smaller and more research-oriented Crawford Hill Lab 1.6 miles (2.6 kilometers)
away. In clear weather, the red laser spot spread as wide as a diningroom
table on its journey and glowed like a fireplace. 15 Yet thick New Jersey
fogs blocked the beam when they rolled in from the shore. 16 So did rain, snow,
sleet, and haze. It should not have been a surprise, but no one had thought
about it. Reference books gave no warning because scientists always had
measured air transmission in clear weather. No one had systematically studied
how weather affected light transmission, much less laser beams, and most
Americans had yet to recognize air pollution.
Poor transmission in bad weather wasn’t a showstopper for all laser communications.
Some companies merely wanted to send laser beams between
buildings on opposite sides of a street; their signals didn’t have far to go, and
they could wait if they had to. Nor did it discourage NASA or the Air Force
from thinking of laser communications above the atmosphere. They had
money and energy to burn in the salad days of the space race, and hoped
tightly focused laser beams would be both more efficient and more secure
than microwaves. (They eventually proved too narrow to hit distant receivers
reliably.)
However, unreliable transmission was a big issue for phone companies that
made network reliability a matter of pride—especially when convincing regulators
to approve expensive new projects. AT&T wanted optical communication
systems to be out of service no more than one hour per year. 17 Early
tests showed that would not be easy in open air. Fog, rain, or snow could
attenuate a laser beam by more than a factor of one million over the 2.6
kilometers between Holmdel and Crawford Hill. 18
British engineers, accustomed to murky air, were quicker to recognize the
problem. One military engineer bluntly told a 1964 conference: ‘‘The atmosphere
is completely inimical to laser transmission systems.’’ 19
Bell Labs didn’t give up as easily on air. As soon as they got the first highpower
lasers, Bell researchers used them to burn holes through fog, but new
fog filled the holes as fast as the laser beam opened them. 20 Fortunately, the
telephone monopoly had vast resources and applied some of them to an alternative,
optical counterparts of microwave and millimeter waveguides.