One Lane, Two Lanes, Red Lanes, Blue Lanes

One of the radical realizations of quantum physics was that electrons sometimes behave like particles and sometimes like waves. Mathematically speaking, the best way to think of them will depend on the situation.

Engineers are now discovering that information is similar. In some situations, information is best conceptualized as consisting of discrete particles called bits. Other times it is best thought of as a continuous flow of light. This second way of thinking of information may revolutionize computer networking just as the wave-particle theory did physics.

A singular insight that has powered the last 30 years of technical innovation is that all information can be represented digitally--that is, all information can be chopped up into ones and zeros.

Representing data digitally makes it much easier to manipulate. Pictures can be stored and transmitted in the same format used for computer data or voice; video can be compressed and added into the digital mix. Thinking of all information as bits allows you to largely ignore what the bits represent. Bits are bits.

But just as Newtonian physics starts to break down as you approach the speed of light, thinking in terms of bits becomes awkward as networks become faster and faster. This is partly because when there are 40 billion bits being sent every second, it’s easier to treat the information as a single flow rather than thinking of it bit by bit.

And it’s partly because, although bits are bits, how they are represented depends on their speed. The faster the bits must be sent, the shorter the electrical pulse. That means every time you increase the speed of the network, you need to put in all-new components that know to look for, and can manipulate, these shorter pulses. That gets expensive when it needs to be done every year.

Solving both these shortcomings is the great promise of photonics, which treats information as waves of light rather than electrical bits. And it’s a promise that will soon be fulfilled. Everyone in the optical-networking industry that I spoke with agreed that the pace of development has sharply accelerated in just the last six months. After two decades of being relegated to the lab, real photonic products are coming to market this year.

Already you can find the first, primitive versions of these products on the highest-volume links of carriers such as MCI, AT&T; and WorldCom. These links, which carry both data and voice, are now providing more capacity at less cost. This trend is only going to continue as the big carriers fight to keep up with the onslaught of Internet traffic and as photonic technology advances to meet the challenge.

Contributing to this sudden acceleration of interest in optical networking is Ciena Corp.’s February initial public offering. Not only was it the most successful IPO ever for a start-up, giving the small maker of optical-networking gear a market capitalization of $3.4 billion after the first day of trading, it also represented the coming of age of wave division multiplexing (WDM).

The WDM products sold by Ciena and others dramatically increase the amount of information that can be squeezed down a fiber-optic cable by treating information as a light wave. Rather than increasing bandwidth by sending information faster--using shorter bits--WDM increases the number of “lanes” on the fiber-optic freeway.

You can think of WDM conceptually as sending some information as a red light wave, some as an orange, some as a yellow and some as a blue. This quadruples the amount of information that can be sent down the pipe.

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Now we’re about to enter the next stage of optical networking by combining the multiple lanes of WDM and a new generation of optical components that are far simpler and more versatile than their predecessors.

Companies such as Ciena, Lucent Technologies and Alcatel are racing to bring optical “add-drop multiplexers” to the market. This innovation will fundamentally change the structure of our information networks.

Today information is shunted from line to line by powerful computers called switches or routers. Data that needs to go from San Francisco to New York might first get switched to Denver and then to Chicago before reaching its destination. Optical add-drop multiplexers will eliminate the need for many of these expensive electrical switches.

Instead, information that needs to go from San Francisco to Chicago will travel in the blue lane, while information that needs to go from San Francisco to New York will travel in the red lane. Instead of having electrical devices that examine the data en route and determine where it needs to go, optical add-drop devices will be configured to strip off the correct color wavelengths at their destination. And they will work no matter what the network’s speed.

While it’s clear that we are headed toward an all-optical network, nobody is sure what the implications will be. More bandwidth, certainly. But new types of service offerings may be possible as well. Rod Alferness, head of photonic networks research at Lucent, suggests the possibility that network providers will start leasing wavelengths so that a company could rent the indigo lane and run it at whatever speed it chooses. But by reducing the network to “dumb” pipes, network providers may find themselves in a very different business.

After all, points out Alan Huang, former department head at AT&T; Bell Laboratories, “telephone companies will tell you that they have always sold switching, not bandwidth. Optical networking is going to force them to come up with a totally new model.”

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Steve G. Steinberg (steve@steinberg.org) is a contributing editor at Wired magazine and a technology consultant for a New York investment firm.