Scientists at Lucent Technologies Inc.'s Bell Labs have determined that a single strand of fiber-optic cable can carry 100 terabits of data per second, which is 10 times more than capacities achieved in lab tests and 50 times more than systems now in widespread use. At 100 terabits of data per second, a strand of fiber could carry 20 billion one-page E-mails at once, according to Bell Labs.

Scientists conducted the research to determine the theoretical capacity limit of fiber optics, the transmission medium of choice in nearly all modern communications networks. The researchers found that "these limits, although they do exist, are significantly beyond" those of current networks, says Partha Mitra, the Bell Labs physicist who led the research.

Current optical transmission equipment has a maximum capacity of 2 terabits per second; scientists have achieved capacities of 10 terabits per second in laboratory tests. The just-concluded Bell Labs research demonstrates that much higher capacities are possible using more advanced electronics to send optical signals across fiber circuits. According to Bell Labs, the research was difficult because the physical properties of the glass in a fiber-optic cable make light react in hard-to-predict ways.

But researchers overcame the challenge by looking at existing fiber-optic transmission systems. Based on the behavior of those systems, scientists calculated the optimal balance between the power of light signals, which travel faster at higher power, and the additional interference created as the power of signals increases. To achieve the higher capacities envisioned by the researchers, makers of fiber-optic transmission equipment will need to develop new modulation schemes to divide the optical signals within a circuit into even more separate beams, Mitra says.

The research shows that "there's room to grow by adding the right electronics," Mitra says, "and with this understanding, we can design better systems in the future."