How to get 1 or 2Km of optical fiber?

David Landry dlandry at byu.net
Mon Mar 18 12:24:22 MDT 2013


On Mon, Mar 18, 2013 at 11:50 AM, Steve Alligood <steve at betterlinux.com>wrote:

>
> On Mar 18, 2013, at 11:18 AM, David Landry wrote:
>
> > On Mon, Mar 18, 2013 at 10:15 AM, Steve Alligood <steve at betterlinux.com
> >wrote:
> >
> >> naw, you can get 32+ colors on a pair of single mode fiber, it just
> isn't
> >> cheap and has problems with different colors at different distances.
> >>
> >
> > Maybe you can, but a single mode waveguide is designed to allow
> propagation
> > of a single mode at a particular wavelength. That wavelength of that mode
> > can be adjusted by changing core diameter and the index of refraction
> > profile [0].
> >
> > I suppose you could couple other wavelengths into an evanescent mode
> along
> > the cladding over a short enough distance, though. Are you referring to
> > some particular product?
>
> no, most dwdm and cwdm systems work with multiple colors across SMF.
>
> I have a set of Cienna chassis with four colors each from Provo to SLC
> across a pair of SMF, and a passive WDM system (optics on their own colors,
> with a shelf that is basically just a prism combining them) that goes the
> same distance across a pair of SMF.
>
> As far as I know, SMF is the norm for most of my vendor's waves they sell
> us across the country.  MMF just doesn't make sense for the distances.
>
> I am not an expert on how they combine, or the issues they have amplifying
> the different colors, etc.
>
Thanks for clarifying. Thinking about it some more, I realized I misspoke.
Keeping other things constant, you should be able to transmit wavelengths
at least up to the V < 2.4 cutoff (above that, you might still be able to
transmit, but it would definitely not be multi-mode anymore). I suppose the
hard cutoffs are material-based.

> BTW, anyone wanting to know more about fiber, read this:
>
>
> http://www.nanog.org/meetings/nanog48/presentations/Sunday/RAS_opticalnet_N48.pdf


+1

Nice set of slides, though I cringed a little where he said that
"intensity" and "power" were the same; intensity has units of power per
area (e.g. W/m^2).
---
David Landry


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