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Shannon Limit: Boosting Capacity of Existing Cable is Limited

By Dick Weisinger

Our increasing consumption of data for Netflix, Zoom meetings, and hundreds of other network services is putting a strain on the cables through which all that data flows.

There is a maximum upper-limit capacity for a data channel. It’s called Shannon’s Limit, and it is controlled by the amount of bandwidth and noise. Laying new cable is expensive: digging holes in metropolitan areas and laying across ocean seabeds cost many hundreds of thousands of dollars.

Scientists are doing all they can to squeeze more data through existing cables within the constraints of Shannon. Last year, engineers in the UK set a new capacity record for transmitting data. The speed is close to the upper limit set by Shannon.

Dr Lidia Galdino, lecturer at the University College London, said that “while current state-of-the-art cloud data-center interconnections are capable of transporting up to 35 terabits a second, we are working with new technologies that utilize more efficiently the existing infrastructure, making better use of optical fiber bandwidth and enabling a world record transmission rate of 178 terabits a second.”

Rob Shore, senior vice president of marketing for Infinera, said that “there’s a limit to the amount of information versus the noise, the optical noise, that you get on a signal. Really the idea with digital signal processors is, they’ve enabled us to really come closer and closer to that limit by filtering out as much of the noise as we possibly can. And there is just a real theoretical limit there. In more advanced modulation schemes, things like that, will continue to get you closer and closer to Shannon, but you can never get past it.”

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