Reaching exabit/s·km data transmission

Jan. 28, 2014
And what exactly does exabit/s·km mean, anyway?
John Wallace 720

The data-carrying ability of a fiber-optic transmission system is often expressed as a capacity-distance product -- that is, in units of data rate times fiber length. For example, a 1 Tbit/s system based on a 10-km-long fiber has a capacity-distance product of 10 Tbit/s·km.

Thus, the capacity-distance product highlights not just the difficulty of achieving a high data rate, but of doing so over long distances. Keep in mind, though, that although the highest data rates tend to be achieved over shorter fiber lengths, you can't just take the above 10 Tbit/s·km system, shorten its fiber length to 1 m, and expect to get a 10 petabit/s (peta = 1015) data-transmission rate. Oh, well.

With this in mind, it is now time to revel in the news that a group of researchers at KDDI R&D Laboratories (Fujimino, Japan) and Furukawa Electric (Ichihara, Japan) has achieved a fiber-optic transmission of greater than an exabit/s·km (1.03 exabit/s·km, to be more exact; exa = 1018) by transmitting 140.7 Tbit/s over 7326 km of fiber.1

They do this with a combination of a seven-core fiber and ultradense wavelength-division multiplexing (WDM) using duobinary pulse shaping, seven-core erbium-doped fiber amplifiers (EDFAs) to keep the signal high, and other tricks to minimize intercore and intersignal interference.

Still, wouldn't it be great if you could take a pair of scissors and cut a 1 km section from this fiber and find that you could now transmit 1.03 exabit/s over it? Might that be possible? No?

Oh, well.


1. K. Igarashi et al., Opt. Exp., doi: 10.1364/OE.22.001220 (2014).

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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