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Fibre optics and multipath disspersion

  1. Apr 1, 2015 #1
    Hey
    I don't understand why multipath disspersion doesn't occur still when monochromatic lights are directed at a fibre obtic. (For example sending dozens of infrared waves at the same time). Wouldn't they still overlap and perhaps superpose?
     
  2. jcsd
  3. Apr 1, 2015 #2
    My understanding of the term "dispersion" is that the propagation time varies with wavelength (or frequency). If we use only one wavelength, then there is no dispersion. However, even with one wavelength in use, multiple transmission paths still can occur and will result in echoes or blurring of a received pulse and create inter symbol interference.
     
  4. Apr 1, 2015 #3
    Thanks for your reply but I am still confsed. The below picture attemps to describe 'multipath disspersion'. If we send monochromatic lights into the fibre, they will still cause blurring as they will interfere, what I understand is that the text below is tellling that monochromatic lights are sent not the white light. At the end of the first paragraph it says: "It would merge with the next pulse" if lights entered are not monochromatic, but wouldn't they still merge if there were many monochromatic lights entering the fibre?
     

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  5. Apr 1, 2015 #4
    Reread the passage. The second bullet says that monochromatic light will disperse if the core is too large. The bottom paragraph talks about an additional effect that occurs when multicolored light is used. Monochromatic light can still have dispersion; just not from this effect.
     
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