May 2001

The Next Generation of Optical Fibers

Novel "photonic-band-gap materials" promise to light up the pipes of the telecom network. Their breakthrough? They carry signals through air rather than glass.

By Philip Ball

At first sight, these new materials are simply odd: thin as a hair, transparent and full of holes. Like the optical fibers that are the mainstay of the telecommunications industry, they're made of glass. But there the similarities with conventional materials come screeching to a halt.

The center of each of these novel fibers-which are made at the University of Bath, in England-is hollow. In existing optical fibers, light is transmitted through a glass core. In the fibers made at Bath, light travels unhindered through air. The light beam is confined to the hollow core by the holes in the surrounding glass material, which looks like a honeycomb in cross section and creates a strictly no-go region for light. The ability to confine light in air this way, says Philip Russell, a Bath physicist, "could completely revolutionize telecommunications."

The reason for the excitement is that, in principle at least, sending light through air rather than through glass could greatly increase the efficiency and capacity of today's high-speed telecom networks. These new materials, called photonic crystal fibers, should "leak" less light and carry more intense light pulses without distortion, reducing the need to constantly boost a signal-an expensive chore in today's optical networks. Photonic crystal fibers should be able to convey much more information along fiber-optic networks while lowering installation and maintenance costs. They will be to existing fibers as a 10-lane freeway is to a country lane. Not only will they take more traffic, but the journey will be smoother and there will be less need for refueling.

It is still early in the development of this new generation of optical fibers. Even the most advanced of the new materials remain several years from widespread commercial use. But with so much at stake-optical telecommunications is a multibillion-dollar business-several industrial labs, including Corning and a handful of startups, are in hot pursuit of their own versions of photonic fibers. While it's too soon to predict which will prevail, rival approaches developed at the University of Bath and at MIT are already competing head-to-head to become the optical fiber of tomorrow.

These efforts may bear fruit just in time for the telecommunications industry. The huge expansion of long-distance optical data transmission in recent years, fed by the growth of the Internet and its bandwidth-hogging applications, has led researchers to find ways to shoot more light and more complex signals through optical fibers (see "Wavelength Division Multiplexing," TR March/April 1999). But many experts believe that in the coming decades it will become impossible to squeeze any more performance out of the current generation of glass fibers. Although it's difficult to predict exactly when the roadblock will be reached, Jim West, a scientist at Corning's research laboratories in New York, definitely believes "we'll run into those limits." And that's when the next generation of fiber optics will become crucial in feeding the world's apparently endless appetite for bandwidth.