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back to article Fibre system reach doubled in university study

Today's optical fibre systems have twice the theoretical capacity currently attributed to them, according to research from the University of Tel Aviv. The study, published on Arxiv, is part of the widespread academic interest in studying the channel capacity of fibre optic systems. Over long distances, and particular where …

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    Doubling? —Not really

    They don't seem to have taken into account that binomial resonance increases with the square of wavelength. It seems unlikely therefore that anywhere near a doubling of capacity would be seen outside of a lab. Not to mention Truscott's theorem!

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    1. Anonymous Coward
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      Facepalm

      Re: Doubling? —Not really

      Truscott was an optimist!

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  3. James 51

    Do submarine optical cables have repeaters? I can see how land based systems could be upgraded to take advantage of this but there might be a bit of a lag in adding it to global networks.

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  4. Schultz

    So XPM look like noise...

    but is not really noise (unpredictable randomness). It's instead a predictable phase modulation that can be mathematically described. Nice to see entropy reduced.

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  5. Kernel

    Re James 51

    "Do submarine optical cables have repeaters? I can see how land based systems could be upgraded to take advantage of this but there might be a bit of a lag in adding it to global networks."

    Modern submarine cables have analogue amplifiers as their submerged plant - they are protocol agnostic and so long as the signal fits within the amplifier's gain band they will work.

    What this means is that in order to increase a cable's capacity you just need to replace the landing station equipment - and if you're lucky this might mean no more than replacing a transponder with a higher capacity one working on the same grid spacing (50GHz between lambdas) eg., replace a 2.5Gb/s transponder with a 10, 40 or 100Gb/s one.

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  6. John Smith 19 Gold badge
    Meh

    Unfortunately submarine FO cables do use laser amplifiers

    So while the process avoids the need for photo/electric/photo conversion it's not clear if you can retrofit this to the shore stations only.

    I'd say the juries still out. It sounds like a good idea.

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