Law of the photon, article can be found in archives at....
forbes.com
Oct 6th issue.
Other articles of fiber optic interest in same issue: "Fast Faster Fastest" and "The Last Furlong".
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Fiber optics is going to make
communication so cheap that we will be
spending much more money on it than
we do today.
The law of the photon
By Howard Banks
MOORE'S LAW said that chip power
would double every 18 months. That's
plodding. The new law of the photon
says that bandwidth triples every year.
Have you ever given up on the Internet
because you got bored waiting for a
photograph to compose itself on your
screen? Your modem is not the main
villain. Your lack of bandwidth is. Even
with the fastest modem in the world, if
traffic is heavy that image is going to take
forever to arrive.
Bandwidth is the carrying capacity of a
communications line. It tells you whether
your telephone line is just good enough
for a plain old telephone call-or can give
you movies on demand, teleconferencing,
remote diagnostics, everything you ever
wanted from the Internet with no wait,
things that you can't even imagine today.
Triple every year? It was a wild claim
when silicon commentator George Gilder
first made it in 1993. Geometric growth
at that rate is rarely seen in human
activity. If anything keeps up that growth
pace, it grows a billionfold in 19 years.
Does anything grow that fast?
Fiber optics comes close. Experimenters
at Lucent Technologies' Bell Labs have
pushed the speed limits in the laboratory
up by a factor of nearly ten in the past
two years, to 3 trillion bits-3
terabits-per second. At the 28.8-kilobit
transmission speed of garden-variety
modems, that's enough for 100 million
simultaneous Internet connections.
In the space of two years MCI has raised
the bandwidth of its Internet backbone
by a factor of 8, to 1.2 gigabits per
second. But for a country where a million
homes want to see video on Web sites
and movies on demand, 1.2 gigabits
won't cut it. For them, those multiterabit
connections now on laboratory benches
at Lucent and elsewhere will be
necessary. When will terabit lines be
available? In not more than five years.
Making all this possible is photonics, the
science of sending data bits down pulses
of light carried on hair-thin glass fibers.
There is no official name for the law that
says how fast this science will carry us
into the next century. We could,
however, call it Payne's Law, in honor of
David Payne, a 53-year-old physicist at
Britain's University of Southampton.
Payne is perhaps the leading scientist
behind two key inventions in photonics
over the past decade and a half.
Significantly, both can be retrofitted onto
fiber already buried in the ground.
One is the optical fiber amplifier, an
ingenious device that makes it possible to
magnify the reach of a light pulse without
first converting that light to electrical
pulses and then back into light. That
amplifier is vital. Without it, photonics
would be advancing, but we wouldn't be
seeing any tripling of power every year.
Payne's second major contribution is an
enhancement to the amplifier that
corrects for the distortions in light
pulses-a smearing of the image, so to
speak-that occur when an optical signal
is pushed to the limits in bit speed and
distance between amplifiers.
At the same time that Payne was leading
the way with these two inventions, other
scientists were advancing a third
technology for expanding the capacity of
optical fibers. It is called wave-division
multiplexing. In plain English, it is a
method for simultaneously dispatching
laser pulses of different hues down the
same tiny fiber. Credit goes to hundreds
of scientists at half a dozen firms,
including Lucent, the Italian tire- and
cablemaker Pirelli, Corning Glass and
Ciena (see story, p. 70).
The world in general has yet to
appreciate the impact this science will
have on our daily lives. "We are really
only in the Stone Age of optical
communication," says Professor Payne.
William Gartner, Lucent's vice president
for optical networking products, talks
about the possibilities. "For businesses
and consumers, applications will emerge
that today we don't even dream about.
High-speed Internet access and video
interconnecting all homes will be a
reality, there's no question of that.
"People are exploring things like remote
surgery today. The need for bandwidth is
just dramatic there. Optics will allow
networking of huge bandwidth from
anywhere to anywhere, so it's maybe the
Mayo Clinic tied in with NYU, tied in
with the University of Houston, all
collaborating on this patient who's being
operated on in Argentina. Doctors don't
even fathom that today."
But they will soon. "Progress [in
opto-electronics] is faster even than
microchips were at the equivalent point in
their development," says Gerry Butters,
president of Lucent Technologies for the
North American region. Electronicast, a
San Mateo, Calif. market analyst, says
that sales of opto-electronic equipment
hit $4.5 billion in 1996 and will grow to
$34 billion by 2006.
After that? The sky's the limit. Two
avenues of current research in
optoelectronics could make the next 15
years as momentous for communications
science as the past 15. One is optical
switching. If amplifiers can be purely
optical, why not switches, the computers
that route all those phone calls and all
that Internet traffic among hundreds of
millions of endpoints?
Everything carried on optical fiber,
whether it's a phone call, a data file or
video, starts out as electrical impulses.
Before they can enter the fiber, they
have to be converted to optical form.
Today that's done at the local phone
company office, using a costly
computer-or switch-that modulates a
laser so that variations in the light carry
the signal (see diagram, p. 72). The
difficulty is separating those different
messages to deliver them to their ultimate
destination.
An optical switch would make the
transfer more reliable and cheaper.
Following a successful demonstration
program led by Darpa (the Defense
Advanced Research Projects Agency) in
late August, Hitachi Telecom (USA)
announced plans for a commercial trial of
an optical switching, or cross connect,
system on MCI's optical network in the
Dallas area. Lucent's Butters reckons that
all-optical devices allowing signals to be
cross-connected should be commercially
available by 1999.
The other glittering goal is so-called
digital optics. Scientists at British
Telecom and in many other labs around
the world are looking for a way to
manipulate light pulses as nimbly as they
manipulate the voltages of a transistor
circuit. "What's needed," says Payne, "is
the equivalent of the electronic world's
ability to take in a weak signal, reshape it
to its precise original form, eliminating
unwanted 'noise,' and then reamplify it
and send it on its way. Optics as yet can't
do this reshaping."
Terabit backbones, optical switches,
digital optics. Stir them together, allow a
decade or so for development and we
arrive at a stage where communication
will be priced in microcents per minute.
But this is a market that is highly
price-sensitive: The cheaper it gets, the
more of it people will use. So what if
your phone bill doubles or quadruples, so
long as the extra money brings you
first-run movies and all kinds of pleasures
and conveniences?
As competition grows in world
telecommunications and national
boundaries fall, Payne predicts, there will
be no cost difference between a call
around the world and one to the corner
grocery shop. By today's standards,
communication will be ridiculously
cheap. Which is precisely why we will be
spending more money on it than we do
today-and why the telecom business
can only grow and grow and grow. |
