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posted by martyb on Thursday May 11 2017, @11:03AM   Printer-friendly
from the low-fiber-diet dept.

John Cioffi, known as the "father of DSL", reckons we're nowhere near the limit of copper transmission speed, delivering a presentation claiming Terabit performance is feasible.

Feasible with a bunch of caveats, that is, the two most important of which are "if research delivers on theory", and "if it can be standardised".

The basis of Cioffi's proposal in this PDF presentation is that at high enough frequencies, signals in copper behave differently to at low frequencies.

At the kinds of frequencies we use for today's DSL, the signal is carried by the movement of electrons in the wires. If, however, the carrier frequency is high enough, the waves propagate in a "waveguide" mode – radio waves following the edge of the copper, rather than electrons oscillating inside it.

So far, so good: none of this is science fiction, and in fact, AT&T's fooling around with using wires as waveguides in its AirGig demonstration.

[...] If – and the more slides of the presentation you read, the more "ifs" there are – the carrier frequency in those waveguides is 300 GHz, and if those channels can carry 4096 tones, and if you can encode 2.5 bits per tone – then you get to a Terabit system that Cioffi reckons can operate at 100 metres; 100 Gbps at 300 metres; and 10 Gbps at 500 metres.


Original Submission

 
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  • (Score: 2) by Immerman on Friday May 12 2017, @04:14AM (1 child)

    by Immerman (3985) on Friday May 12 2017, @04:14AM (#508464)

    I'm not altogether certain the same reasoning applies: with VDSL you're still pushing electrons down the wire, which will generate a substantial electromagnetic field that in turn interacts with the fields generated by adjacent pairs, causing crosstalk between the channels.

    I'm speaking outside my expertise, but my intuition tells me that that situation might change radically if the wires were being used as waveguides rather than electron conductors. I'm pretty sure radio waves interact with each other far less than parallel electrical currents do.

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  • (Score: 2) by Scruffy Beard 2 on Friday May 12 2017, @05:44AM

    by Scruffy Beard 2 (6030) on Friday May 12 2017, @05:44AM (#508501)

    I peeked at TFA. It looks like they would have to pull new cable. The presentation slide shows 3, rather than 2, wires grouped together.