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Fiber optic loop

  1. Mar 24, 2015 #1
    Imagine a closed loop of fiber optics, How long will a photon be able to stay inside the loop before dissipating all it's energy, or does it not dissipate?
  2. jcsd
  3. Mar 24, 2015 #2
    Absorption of light in glass is not zero, it depends on how many defects in the glass. The less defects in the fiber, the more light will keep its intensity. As for a single photon, the probability of absorption similarly depends on the purity of the glass. Fibers carry light accross oceans, and some lasers are created with fibers, so defects can be sufficiently reduced for a fiber to have many impressive applications.
  4. Mar 24, 2015 #3


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    Greetings Danyon

    a tiny fraction of a second before it is absorbed :smile:
  5. Mar 24, 2015 #4


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    Note that a single photon cannot give up part of its energy. It's all or nothing.
  6. Mar 25, 2015 #5


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    I believe a typical attenuation for a multimode fibre would be say 2dB per kilometre (factor of 1.5). So I think if you defined "dissipated" to be when the intensity is down to say 1/1000th (0.1%) of it's original value it would need to travel about 17km. You can work out how long it would take to travel 17km.

    Oops I was in a rush. Might be slightly out in my numbers.
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