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A comment on How fast are those packets moving?. Parent comment

Re:How fast are those packets moving? by hansc on Friday November 24, 2017 @06:30AM (#15770554)
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+F...
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Re:How fast are those packets moving? by amazon_not on Friday November 24, 2017 @07:01AM (#15770633)
Single mode fiber isn't immune to dispersion or other impairments, it just does better than multimode.
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Re:How fast are those packets moving? by gsnedders on Friday November 24, 2017 @06:46AM (#15770596)
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.)
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Re:How fast are those packets moving? by amazon_not on Friday November 24, 2017 @07:05AM (#15770647)
> 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.

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Re:How fast are those packets moving? by rocqua on Friday November 24, 2017 @07:04AM (#15770643)
I believe the fiber acts as a waveguide, essentially keeping the wavefront perpendicular to the fiber at all times.
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