PWM Fibre Optic Signal Transmission Help

Discussion in 'Homework Help' started by Volt, Mar 15, 2009.

  1. Volt

    Thread Starter Member

    Nov 28, 2008
    24
    0
    Hello,

    I am currently writing a lab report and i'm trying to figure this out...

    I have used pulse width modulation to convert an AC sine wave signal into digital and then back using a filter after it has been transmitted through 1m of optic fibre cable.

    The decoded signal was 110 nano seconds behind the original signal.

    Why is this? is it the time it takes to travel through the cable or the time it takes to decode?

    Any help is much appreciated!

    Thanks in advance!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    Look up the subject "propagation delay". It simply takes some time for the signal to pass through all those components.
     
  3. Volt

    Thread Starter Member

    Nov 28, 2008
    24
    0
    Thanks for the quick reply, that helped alot, one more question....

    If i sent an AC signal down through a fibre optic cable and studied the end of the cable as I increased the voltage, why is it that the light at the end gets brighter?

    Thanks
     
  4. bertus

    Administrator

    Apr 5, 2008
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    2,347
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    This is just a guess, as you have not given any details about how you
    .

    If you are just passing the signal through a limiting resistor and LED, then more voltage means more current, and so a brighter LED.
     
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