Scientists Raise Fiber-Optic Limits

Scientists at Lucent Technologies Inc.'s Bell Laboratories say they've found the upper limit of how much information can be transmitted over a fiber-optic line. It's 10 times what was previously believed at roughly 100 terabits of data per second in a single strand of fiber. That's equivalent to 20 billion one-page E-mails or 2 billion phone calls.

Current fiber-optic systems can send information at a rate of about 2 terabits per second, and rates as high as 10 terabits have been achieved in a laboratory. But no one has ever really known just what the limits of fiber-optic transmission are. The complicated behavior of light and the unique physical properties of glass required an infinite number of variables to create an equation to figure out the limit.

But Bell Labs scientists took a new approach to the quandary. "What we did is simplify the problem by bringing techniques from quantum physics and information theory," says Partha Mitra, a physicist who led the Bell Labs research team. That let them come up with a model and figure out the ultimate capacity of a fiber.

The discovery shows that optical fiber networks will not only be able to meet the needs of increasingly high-speed, bandwidth-gobbling technologies, but have potential far beyond that. "The fact that you know networks can be scaled in this way means optical fiber is a good way to grow your system," Mitra says. "It shows that fiber optics is really a smart choice."