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Light Traveling in both Directions in a fiber optic cable

  1. Jan 10, 2012 #1
    We have a spectrometer in our lab that collects light through a fiber optic cable, however it also sends a 532nm laser down this fiber optic cable.

    My background isn't in optics, and it would seem to me that the returning light (which is typically around 694 nm) would interfere with each other. Why would this not be the case?
  2. jcsd
  3. Jan 10, 2012 #2
    Okay, so it probably actually would be the case, this spectrometer actually uses two separate cables that are just bound in the same tube so it was hard to tell that is what is going on.
  4. Jan 11, 2012 #3
    Actually it wouldn't. Think about it. If I'm on the right end of a room looking at you and you're on the left end of the room looking at me we can see each other fine despite the fact that your light and mine travel through the same space in opposite directions.
  5. Jan 11, 2012 #4

    Ken G

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    Gold Member

    It might also help to consider the "principle of superposition", which applies to light in any application other than nonlinear optics. This priinciple means that you can analyze each source of light separately, and just add up all the results at the end. In regions where the light from both sources overlaps, you can get "interference", but that doesn't mean the propagation of one is inhibiting the propagation of the other, because you can still just add up the net results of both anywhere they don't overlap (like in your eyes or my eyes).
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