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A How can light propagate through Hollow optical fiber.

  1. Jul 25, 2017 #1
    Now I am studying a bit of optical fibers. And of course generally optical fiber works because of total reflection property of the light, which happens when the light from higher medium hits the lower medium material.

    However I recently found out that there also is a thing 'Hollow optical fiber' which the core is hollowed out, filled with an air. I think the propagation should not happen cuz total reflection won't work here, but it works perfectly fine. I've hit some papers and got some keywords like 'band gap waveguide', 'photonic crystal' etc... but still can not understand it.

    Can you give me a brief explanation, or just let me know where should I start with first?
  2. jcsd
  3. Jul 26, 2017 #2


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  4. Jul 26, 2017 #3


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    @KT KIM: How about a few references about this idea? If you've been reading then save us from having to search for what you're describing.

    The hollow fibre seems to avoid the path loss through the glass so, if reflections can be made to rival the efficiency of TIR, the net loss over a long path could be less. We tend to assume that TIR is the only reflection worth considering. The above link seems to stress the improved transmission speed so, perhaps it's not so much aimed at long distance paths but at local connections. 3.5dB per km is not going to take you across the Atlantic easily.
  5. Jul 26, 2017 #4

    Andy Resnick

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    It's not clear to me if you are talking about photonic bandgap fibers (which can have a cavity in the center) or some sort of hollow 'light pipe'.

    Photonic bandgap fibers are best analyzed in terms of wave optics, not ray optics. The interior is very inhomogeneous and is designed to allow only certain field modes to propagate. Having air (or vacuum) in the center is useful for high-power applications because there's no damage to the material.
  6. Jul 27, 2017 #5
  7. Jul 27, 2017 #6
    More exact to say, I wanted to talked about, Photonic crystal fiber (including photonic bandgap fiber), maybe 'hollow optical fiber' was not a good word choice, excuse me.
  8. Jul 28, 2017 #7

    Andy Resnick

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    Try starting with this:

    OPTICS LETTERS / Vol. 25, No. 2 / January 15, 2000
    Analysis of air-guiding photonic bandgap fibers
    Jes Broeng, Stig E. Barkou, Thomas Søndergaard, and Anders Bjarklev

    We present what is to our knowledge the first theoretical analysis of air-guiding photonic bandgap fibers. The
    fibers are characterized by a large hollow core and a microstructured cladding exhibiting photonic bandgap
    effects. Using an efficient, full-vectorial numerical method, we explain the operational principle of the fibers
    and obtain detailed information about the properties of the air-guided modes. This information includes
    accurate determination of the modes’ spectral extent, cutoff properties, and mode-field distributions.
  9. Jul 29, 2017 #8
    I presume the photonic action gives us a hollow tube with reactive walls, which therefore reflect nearly all the energy. It seems equivalent to a metal waveguide with deep corrugations.
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