By the time you read half of this article, an amount of information comparable to the print holdings of the Library of Congress will have streamed across the major lines of the nation's communications network.

As more advanced generations of light-carrying optical fibers arrive over the next few years, that amount of information will course through the network in the time that it takes you to read this sentence's last three words.

What's the big hurry?

Something historic is happening. The mix of traffic on the network is morphing from mainly voice traffic via telephones, which traditionally has traveled along copper wires in electrical bursts, to mainly digital data traffic between computers and other digital devices.

That rapid-fire chatter of ones and zeros -- in the form of current peaks and lows in traditional wires, or pulses of light and darkness in optical fibers -- now encodes everything from written words to military targeting coordinates to financial records to moving images.

The shift is one of those hidden historic milestones, like the one in 1979 when the volume of plastic production in the United States overtook the volume of steel production for the first time.

Keeping communications lines open has become to society what keeping blood vessels flowing is to you. And growing each year is a hunger for more bandwidth, industry-speak for the number of bits (digital data in the form of ones and zeros) a communications system can transfer each second.

To Donald Keck of Corning Inc., in upstate New York, it's another round of deja vu. He was fresh out of graduate school in the mid-1960s when he found himself confronted with a challenge at what then was called Corning Glass Works.

"The number of phone calls was going up increasingly, and people were beginning to worry that copper wires were not going to be to able carry the amount of traffic," recalls Keck, a 1993 inductee to the National Inventors Hall of Fame.

For one thing, there wasn't much more room for big copper cables. City streets already were stuffed to the manholes with communications and electrical cables, steam and water pipes, subways and sundry other space-taking items.

Engineers knew it was possible to send much more information over wires by increasing the frequency of the electrical waves carrying the signals. Frequency is the number of waves per second; increasing frequency is like reducing type size so you can pack more words on a page.

But with electrical waves on wires, the higher the frequency, the quicker the signal weakens into static. So in the 1960s, any plan for dramatically increasing bandwidth on an all-copper network had to include expensive, clunky items such as "signal boosters" every few thousand feet or so.

That's why Keck and others were looking for something that could leapfrog copper's limitations. The world's first laser beam in 1960 began lighting a way to a solution. "We began to say, `Well, gee, because of the high frequency of optical waves, we should be able to carry much, much, much, much more information over a light beam than we could over electrical waves on wires,' " Keck says.

Instead of electrical frequencies in the thousands (3.3 kilohertz, or thousands of cycles per second, for phone lines), optical frequencies were millions and billions of times faster. Trouble was, light wasn't going anywhere over copper wires.

That puzzle thrust Keck and two fellow researchers at Corning into a technological breakthrough that would change the world. The researchers were Robert Maurer, a physicist and group leader, and Peter Schultz, a materials expert.

They knew about earlier failures to steer light through the air using mirrors, which Alexander Graham Bell had tried in Washington in 1880, through pipes fitted with lenses and mirrors and even through crude glass fibers [see timeline above]. All had proved too clumsy, expensive or unreliable to compete with good old copper.

By 1970, the Corning team had succeeded where these others had failed by devising a remarkable glass-in-glass fiber 1 million times more transparent than the clearest glass known.

The key to the invention was to use two kinds of glass. For the light-carrying core, so thin that a few dozen could bundle inside a human hair, they used silica glass -- basically, glass made from molten sand -- deliberately spiced with titanium atoms.

That smidgeon of atomic dirt, chosen specifically so it would not absorb light, makes the core a wee bit less pure than the second kind of ultra-pure "cladding" glass used to surround the core like a sleeve.

Good Reflections

To light traveling down the core, the cladding behaves like a cylindrical mirror -- light can ricochet off the cladding and back into the core, but it cannot leak out of the fiber, that is, the minimum amount of information is lost.

The Corning researchers and other colleagues spent a decade readying the fibers for prime time by developing better manufacturing methods and toughening cables so they could be handled in the field without breaking.

Then, Keck says, "the major telephone companies came in and began ordering large quantities of fiber. MCI [now MCI WorldCom] placed the first large order with us, and that for us kicked off the whole revolution."

That would be the optical communications revolution. Since that first big order, the world has been wired with more than 140 million miles of optical fiber, essentially all of it based on the design of the Corning trio. A mile's worth of new fiber is installed every second, Keck says.

The first wave of fibers went into long-haul "trunks" between cities, across countries and, beginning in 1988, under oceans. Their capacity was amazing. One fiber could carry 80,000 phone calls using a single infrared wavelength of light (1310 nanometers, or billionths of a meter). It could take bundles of copper wires as thick as an arm to handle the same volume.

But no one in the 1980s anticipated how an Internet would burst out of its humble beginnings within the Department of Defense and become a society-transforming force in the 1990s.

With millions of computers stuffing previously unanticipated Amazon Rivers of data through the network and people yakking on the phone more than ever, the amount of overall traffic -- voice and data -- began surging like never before. Even the capacity of optical fibers began to seem limited.

One annoying problem was that the light signal eventually deteriorated as it bounced its way along even the most transparent of fibers. As a result, light pulses had to be boosted or "amplified" at intervals in long-haul optical lines.

Network engineers had been installing bulky and expensive "optoelectronic" repeaters every 35 to 60 miles. Each of those electronics-filled repeaters detects waning incoming optical signals, converts them into electrical signals, boosts the electrical signals much as a home stereo amplifier builds up an FM radio signal and then converts them back again into strong laser pulses.

The rejuvenated light pulses then are injected into the next segment of fiber and travel to the next repeater. That complicated conversion process takes a toll on the original signals.

More and Faster

That's why researchers at Bell Laboratories (now Lucent Technologies' Bell Labs) in Murray Hill, N.J., and elsewhere were happy to find some optical rabbits to pull of their hats. Key among them was the "erbium-doped fiber amplifier," or EDFA.

By peppering the core of an optical fiber with atoms of erbium, an obscure silver-gray metal a bit lighter than platinum, researchers could build a new kind of light-booster inside the fiber itself.

First, a "pump" laser injects energy into erbium atoms. Then, Keck explains, "as the information-carrying beam passes through the fiber, it extracts energy from the pump beam and becomes amplified" [see illustration below].

But there was a rabbit inside this rabbit.

"The remarkable thing about these amplifiers is they can amplify a broad range of wavelengths, many different colors of light," Keck says. "And that meant it became practical to send many, many laser beams, each at a slightly different color, through the very same fiber."

In techno-speak, it's called "wavelength division multiplexing," or WDM for short. And it's how you make one fiber already in place do the work of many.

One of the premier WDM companies in the world is Ciena Corp., based in Linthicum, Md.

"If you use WDM, you have the opportunity of loading onto that fiber 16 or 40 or more different frequencies of light," says Andrei Csipkes, who oversees Ciena's manufacturing processes at the company's facilities in Savage, Md. "They're all packed together, racing together, in a composite signal."

Ciena's high-end WDM system can handle 96 channels, each capable of transmitting 2.5 billion bits of data per second. By comparison, the fastest conventional dial-up modems that connect you to the Internet carry about 50,000 bits per second.

It takes eight bits to represent one letter. At an average of six letters per word, that's nearly 1,000 words a second.

Other companies are offering systems of as many as 160 channels. And there's more to come, because researchers are always pushing the envelope.

In 1997, researchers at Lucent Technologies sent 100 wavelengths of laser light, each pulsing at a rate of 10 billion bits (10 gigabits) per second, down a single fiber 250 miles long.

When that technology finds its way into the commercial network, lines should be able to transmit a terabit (one trillion bits) per second. That amounts to about 12 million simultaneous phone conversations or the information equivalent of all the printed material in the Library of Congress every few minutes.

Of course, even that rate might seem sluggish in the coming century. So researchers are working on fibers that can carry 10,000 channels, Keck says.

Attractive and useful technology that becomes less expensive as it gets becomes better and more powerful is a proven formula for changing the world.

COSTS PLUNGING

"Transistors are now a billion times cheaper than they were in 1950," says David Bishop, head of group working on new switching devices for optical communications systems at Lucent Technologies.

Transmission capacity of optical fiber systems is becoming better and cheaper even faster than that, Bishop adds almost breathlessly. In 10 years, it ought to cost about one-thousandth as much to transmit 1,000 times as much information.

"There just aren't many things in our lives for which we see the cost drop so rapidly," he says. "Chickens don't do that, and automobiles and toasters and newspapers don't do that."

When the cost of powerful technology plunges, the technology reaches so many more people with their own ideas that there's no telling what forms the technology will assume.

Bishop, for one, can't quite overstate the possibilities: "The ability to move terabits of information around inexpensively and quickly is going to have as important an impact on society as the ability to make steel or electronic integrated circuits. It will be as important to society as running water."

The least it might do is slow the rising household cost for information. "By the time you add in your regular land line [phone], cable and cellular telephones, newspapers and magazines, many American households spend more on information than they do on food," says Bishop, who admits that his household is one of them.

Bishop and Keck say the greatest changes probably will sweep through developing nations.

"We in the United States think nothing of internet communications today," Keck says. "But if you look out in the world, one-half of the world has yet to make their first telephone call, and 50 percent of them would have to walk eight miles to the nearest phone."

Wiring the rest of the world with high-capacity communications lines could shrink space and time far more than jet travel has. Millions, perhaps billions, of people will be able telecommute anywhere in the world.

project oxygen

The most ambitious project to globalize the availability of communications capacity is called Project Oxygen, implying that information has become as fundamental to modern life as oxygen always has been.

When the project's first phase is completed by mid-2003, it will have taken $10 billion to install more than 100,000 miles of new WDM fiber optic cable, almost all of it on the ocean floor.

The undersea cables will emerge from the sea at 96 points in 75 countries where their 2.56-terabit capacity will flow. Phase II will extend the network in ways to be specified in coming years. A consortium of several dozen telecommunications companies has joined to finance the network's construction after which the companies will be co-owners, users and sellers of the new capacity.

The business opportunities seem unlimited. But for some, like Keck, the humanitarian opportunities may be more astonishing.

"One of the great benefits I see from all of this over the years," he says, "is hopefully increasing the quality of life around the world simply because we can communicate and get information in everybody's hands."

Ivan Amato is author of Stuff: The Materials the World is Made Of (1997).

A History of Communicating With Light

1854 John Tyndall, an English scientist, shows that a stream of water emerging from a hole in a tank will trap light inside the tank as the water bends downward. As he put it: "The light upon reaching the limiting surface of air and water was totally reflected and seemed to be washed downward by the descending liquid, the latter being thereby caused to present a beautiful illuminated appearance."

1880 Alexander Graham Bell tests his invention, the photophone, by sending beams of light between two rooftops. Talking into a cone makes a thin mirror vibrate. A beam of sunlight is reflected off the mirror to the receiver, which converts the light into electrical currents. One big show stopper: clouds.

1881 William Wheeler, an engineer in Concord, Mass., applies for a patent on a system of pipes with reflective interiors to distribute light from a central source to other locations in a building. The advent of electricity and incandescent lighting stranded his idea.

1930 Inventors in the United States and Britain find that they can use fibers of solid glass or quartz to transmit images. An early application: internal medical observations.

1934 Norman French, an engineer with AT&T, proposes a network of "light cables" made

of "solid glass, quartz or a similar material" that would carry voice traffic on wavelengths of light. At that point, however, no one has made a cable in which any kind of light would travel even a few feet.

1950s Internal reports at AT&T predict that light-based communication is a bad bet unless something like a laser -- that is, a source of intense light of essentially a single wavelength -- could be invented.

1960 The first working laser is built, using a ruby rod, by Theodore Maiman of Hughes Research Laboratories.

1963 Elias Snitzer of American Optical proposes that, if lasers and optical fibers could be made transparent enough, they would provide a great way to communicate.

Mid-1960s Frustrated that the best glass fibers of the day are gobbling up too much light, researchers at Bell Laboratories return to Wheeler's 1881 idea. They build a system of pipes that are filled with gas and then locally heated. That creates a lensing effect that refocuses the gas along the pipe's length.

1966 Researchers at Standard Telecommunications Laboratories report in an article that losses of light traveling in glass fibers were due mostly to impurities in the glass and not to some fundamental limitation.

1970 Donald Keck, Robert Maurer and Peter Schultz, shown below, invent the first optical fiber capable of transmitting light efficiently enough for communications.

Lines of Light

Communication begins with the fabrication of optical fiber. One initially popular method (right) involved drawing components from each of two crucibles of molten glass. Newer methods build up fibers by vaporizing glass and letting the "soot" settle onto forms.

The end result is a central strand surrounded by a "cladding" layer a bit thicker than a human hair (below). Light waves traveling down the inner strand bounce off the boundary between the two glass types in a process called "total internal reflection."

Eventually, the light signal weakens. It can be amplified using glass doped with the rare-earth element erbium (below). A tiny "pump" laser excites the erbium atoms, which store the laser energy. As the weak signal waves pass through the erbium area, they pick up the stored energy and leave the amplifier thousands of times stronger.

More than 90 percent of long distance and international voice and Internet traffic is carried by optical fiber. Most cable TV is distributed by optical fiber. More than 25 million miles of fiber is already installed in the United States, enough to circle the Earth and equator 1,000 times. About 50 million more miles are installed outside the United States. By 2005, the length of fiber linking continents under the seas will reach 360,000 miles, enough to circle the globe nearly 15 times. Optical fiber for communications is being installed worldwide at a rate of 3,000 feet every second, or 2,000 mph. This rate is more than twice the speed of sound.

SOURCES: Optical Society of America; Corning Inc.