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Here is a suspicion I have, can someone who has experience in the field shed some light on this?: In addition to the refraction index, you’d expect fibre optic

Here is a suspicion I have, can someone who has experience in the field shed some light on this?: In addition to the refraction index, you’d expect fibre optics to have another limiting factor: scatter. As light bounces off the side of the fibre, it gets scattered back and forth. I.o.w.: you’d expect a single, “perfect” pulse to eventually reach the other end as a slightly drawn out pulse (with its intensity spread out over a bell curve?). Is that true? If so, does that mean that in fibre optics , the longer the cable, the lower the frequency at which you can send pulses, to avoid “bleeding” from one into the next? And is it true radio doesn’t have that? Or does fibre not work that way?

hansc 9y ago
This is the case in Multimode fiber, which is used for short distances (meters). For anything longer, single mode fiber is used and the core of the fiber guides the light. See https://garyherlache.wikispaces.com/Digital+Communications+Fall+2009+Fiber+basics https://garyherlache.wikispaces.com/Digital+Communications+F...
- gsnedders 9y ago
  That looks like single mode fiber never refracts… Surely it can't go round any bend, then, though? (And I'm probably missing something obvious. It's been a while since I've done optics of any sort.)
  - rocqua 9y ago
    I believe the fiber acts as a waveguide, essentially keeping the wavefront perpendicular to the fiber at all times.
  - amazon_not 9y ago
    > That looks like single mode fiber never refracts… No, it does. > Surely it can't go round any bend, then, though? No, if you bend the fiber too much the light leaks out into the cladding.
- amazon_not 9y ago
  Single mode fiber isn't immune to dispersion or other impairments, it just does better than multimode.
amazon_not 9y ago
> In addition to the refraction index, you’d expect fibre optics to have another limiting factor: scatter. Fiber optics have lots of limiting factors: power limits, chromatic and polarization mode dispersion, spectral attenuation, manufacturing imperfections, crosstalk, ... Fiber optics are just better than a lot of other mediums, but that does not mean there aren't limitations.
topranks 9y ago
Good overview below: https://youtu.be/_KFpXuHqHQg https://youtu.be/_KFpXuHqHQg https://www.nanog.org/sites/default/files/Steenbergen.Everything_You_Need.pdf https://www.nanog.org/sites/default/files/Steenbergen.Everyt...

hansc 9y ago

This is the case in Multimode fiber, which is used for short distances (meters). For anything longer, single mode fiber is used and the core of the fiber guides the light. See https://garyherlache.wikispaces.com/Digital+Communications+Fall+2009+Fiber+basics https://garyherlache.wikispaces.com/Digital+Communications+F...

gsnedders 9y ago
That looks like single mode fiber never refracts… Surely it can't go round any bend, then, though? (And I'm probably missing something obvious. It's been a while since I've done optics of any sort.)
- rocqua 9y ago
  I believe the fiber acts as a waveguide, essentially keeping the wavefront perpendicular to the fiber at all times.
- amazon_not 9y ago
  > That looks like single mode fiber never refracts… No, it does. > Surely it can't go round any bend, then, though? No, if you bend the fiber too much the light leaks out into the cladding.
amazon_not 9y ago
Single mode fiber isn't immune to dispersion or other impairments, it just does better than multimode.

amazon_not 9y ago

> In addition to the refraction index, you’d expect fibre optics to have another limiting factor: scatter. Fiber optics have lots of limiting factors: power limits, chromatic and polarization mode dispersion, spectral attenuation, manufacturing imperfections, crosstalk, ... Fiber optics are just better than a lot of other mediums, but that does not mean there aren't limitations.

topranks 9y ago

Good overview below: https://youtu.be/_KFpXuHqHQg https://youtu.be/_KFpXuHqHQg https://www.nanog.org/sites/default/files/Steenbergen.Everything_You_Need.pdf https://www.nanog.org/sites/default/files/Steenbergen.Everyt...