Bell Labs Reports the First Long Distance Transmission of 1 Terabit per Second; Then it Doubles the Speed 4 Years Later

In 1998 Bell Laboratories reported the first long-distance transmission of one terabit (trillion bits) of data per second over a single strand of optical fiber. Then on March 25, 2002 Bell labs reported that it doubled the distance and the speed at which data could be sent over long-haul telecommunications networks.

"Bell Labs said that, in a demonstration, it sent a massive 2.56 terabits of data per second over a distance of 2,500 miles, the equivalent of sending the contents of 2,560,000 novels every second across the United States. One terabit is a little over 1 trillion bits of data. The previous record was 1.6 terabits per second over 1,250 miles, or half the distance.

"Bell Labs achieved the 2.56 terabit-per-second speed by sending 40 gigabits-per-second of data over each of 64 separate channels in fiber optic cable, which uses light waves to carry data. It used dense wave division multiplexing, a technology that allows service providers to push bigger chunks of data onto a single strand of optical fiber.

"The capacity and distance improvement was made possible by use of a coding scheme called differential phase shift keying, which Bell Labs has developed for high-capacity communications. Lucent’s long distance networking product, LambdaExtreme, cannot support the higher data speeds" (, accessed 9-2020).

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