City of Light: The Story of Fiber Optics

THE LASER STIMULATES THE EMISSION OF NEW IDEAS 93
generate a very ‘‘clean’’ signal. To realize the tremendous theoretical capacity
of optical communications, you need an oscillator that generates light. Back
in 1951, Bell Labs had concluded that the only way optics could match the
capacity of the millimeter waveguide was with a coherent light source. 3 With
no coherent light in sight, Bell Labs pursued the millimeter waveguide. The
emergence of the laser got Bell Labs and many others to take optical communications
seriously.
First-Generation Lasers
The laser was years in the making, and like many other new ideas of the
time, it grew from microwave research. Charles H. Townes, then a physics
professor at Columbia University, took the first step in 1951 when he realized
how to make a new type of coherent microwave oscillator. He called it the
‘‘maser,’’ for microwave amplification by the stimulated emission of radiation.
4 His idea was to collect a group of molecules excited so that they possessed
extra energy, and stimulate them to emit that extra energy in the form
of microwaves. Three years later, he had a working maser.
Other masers followed, and Townes realized he could expand the principle
to make an optical oscillator. He teamed with his brother-in-law Arthur L.
Schawlow, 5 then working at Bell Labs, to work out the details. Their theoretical
proposal 6 started a race to build the device, later christened the laser.
On May 16, 1960, Theodore Maiman won the race by firing pulses of red
light from a small ruby cylinder at Hughes Research Laboratories in Malibu,
California. 7 After the editors of Physical Review Letters summarily rejected
Maiman’s paper reporting his discovery, 8 he fired a 300-word letter to Nature, 9
and Hughes called a press conference on July 7. Some observers were skeptical,
but Schawlow soon duplicated Maiman’s feat from newspaper accounts.
The laser era was off and running.
Electronics magazine put communications at the top of its list of potential
uses for the new invention. 10 Laser beams were focused much more tightly
than microwaves (a consequence of their shorter wavelength), so they looked
promising for sending signals long distances through space or the atmosphere.
Rudolf Kompfner, head of transmission research and director of Bell’s Crawford
Hill Laboratory, was quick to see the possibilities. In October, Electronics
showed two Bell Labs scientists firing their new ruby laser through 25 miles
(40 kilometers) of clear air. 11 In reality, the laser fired only one pulse at a
time, so it could not send useful information, but the experiment showed that
the potential was there. So was the demand for communications, as the microwave
spectrum and existing cables were filling. Millimeter waveguides
were set to be the next technological generation, but lasers might follow them
on the ground, and perhaps replace microwave links in space. Looking farther
into the future, Townes suggested interstellar communications might be possible
with highly directional, high-power laser beams. 12
First, however, scientists needed better lasers.