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I What's the mode of light in single-mode fiber?

  1. Dec 28, 2018 #1

    We talk about single-mode and multi-mode fiber and I assume they talk about the way of sending just one modes (TEM or TMmn or TEmn). Which mode is generally used for single-mode fiber? Is this set by the geometry of the single-mode fiber (especially the opening)? Also, this means that the source of light should have the same mode, right?
  2. jcsd
  3. Dec 29, 2018 #2


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    what research have you done so far and what has that reading told you?
    give some links you have read and let us know what bits you need clarification on :smile:
  4. Dec 31, 2018 #3
    Hi Thanks for the reply.

    I was just studying about single and multi-mode fiber online. Since it says single-mode fiber, I assumed that it sends only one of the modes of the electromagnetic wave, but don't know which one.
  5. Dec 31, 2018 #4


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    googling your question

    which mode is used in single mode optical fibre ?

    brings up many links ...


    go have a read and see if your question gets answered
    if you are still struggling, then give one of those links and tell us what part you don't understand :smile:

  6. Jan 1, 2019 #5


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  7. Jan 13, 2019 #6
  8. Jan 14, 2019 #7
    Single mode, in any optical context, always means the lowest order mode. In principle, thats the LP01 or gaussian mode. Whether a fiber is single mode or not depends strongly on the wavelength of the guided light, as the V number is inversely proportional to the wavelength. It's the same with laser light. If the beam is meant to be single mode its intensity profile is always gaussian. But as anything in the world, there is no 100% perfection. So even in single mode, some percentage of the light might be in higher order modes. But these percentage a in general negligible for dominant single mode opperation.
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