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Electrical and fibre optic .

  1. Feb 17, 2005 #1
    Electrical and fibre optic.....

    Why is it that a fibre optic cable must boosted less frequently than an electrical signal in a copper wire, I understand that there will be resistance in the wire and thus the voltage will drop the further you go, but surely there will still be the changes in voltage, and it is this which is important in the signal. Why do we not just wait till our destination before we amplify the electrical signal?

    Thanks. :smile:
  2. jcsd
  3. Feb 17, 2005 #2
    Actually, come to think of it, why do we amplify along the journey of the signal? Why not just amplify it at the end?

  4. Feb 17, 2005 #3


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    1) A fiber optic cable suffers less loss per foot than an electrical cable.

    2) Because while the noise stays the same magnitude at all places in the cable, the signal constantly decreases with distance. The signal-to-noise ratio gets smaller with distance. If you space your amplifiers further apart, the greater loss in SNR means that it's more difficult to separate the signal from the noise, so the separation is less perfect. (When the signal is roughly the same amplitude as the noise, the two are indistinguishable.) The signal thus loses fidelity by the time it reaches the receiver.

    - Warren
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