Paving the way for a terabit future

Article By : Rick Merritt

Terabit DSL is a breakthrough in the pursuit of ultra high speed over copper, researchers say.

« Previously: DSL pioneer shoots for terabit future

When cut sideways, a typical bundle of twisted pair lines looks a Swiss cheese. Terabit DSL (TDSL) uses those gaps to send wireless signals. Wires don’t carry signals directly but act as waveguides for them.

Because the gaps are so small, the signals need to use tiny wavelengths. “We used 50GHz to 500-600GHz, it’s not all going to work on any one cable,” John Cioffi, a professor emeritus at Stanford and chairman of Adaptive Spectrum and Signal Alignment (ASSIA), said of models he developed with colleagues at ASSIA.

“Instead of injecting current in the wires, we foresee putting almost microscopic antennas like a donut or bowtie around the wire—not touching it,” Cioffi explained. “Shooting an IR laser at those elements creates a millimetre wave similar to what’s done in coherent optics, but we use a different frequency and an array of signals instead of just one used in optics."

TDSL_antenna_02 (cr)
Figure 1: TDSL antennas may look like bow ties or donuts. (Source: John Cioffi)

The array of antennas applies concepts well studied in MIMO wireless and vectored-DSL wired systems for “steering messy, multi-dimensional channels,” he said.

The good news is adequate silicon support is here or on the horizon. Existing 120GHz ADCs and cost reduced versions of today’s 16nm GPUs could handle the electronics, he estimated. Nevertheless, much work is still ahead.

“At these speeds devices to get signals in and out of the Swiss cheese will be expensive to develop…it’s a multi-million project for someone to measure” the TDSL effects with high accuracy, he said. “I’m trying to encourage as many large service providers and big network equipment providers to validate [the work] and add their own contributions,” he added.

“If there’s a motivated entity, this can be done in two to three years, it’s a matter of someone believing they will get a return and making it happen in a way that can be mass reproduced…[but] it’s too early to project the best business models,” said Cioffi who in the 1990s formed Amati, a start-up that made ADSL chips and was ultimately acquired by Texas Instruments.

At a time when companies across the industry are collaborating to spend hundreds of millions of dollars on 5G cellular, “I’d love to see that investment and intensity here, the return could be even larger when you consider delivering bandwidth to every cell site, let alone home,” he said.

First published by EE Times U.S.

« Previously: DSL pioneer shoots for terabit future

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