[rescue] Fiber loop simulators?

[Chris Byrne]

Also that is point source attenuation on full strength clean signal.
Distance attenuation has entirely different characteristics as energy falls
off is exponential not linear. And theres jitter to take into account
(frequency shifts caused by refraction through a medium), which is different
from the frequency decomposition that James related below, and is made worse
by it.

The guy who sat next to me at storageway had a doctorate from UIUC in high
energy optical physics. We used to have some REALLY fun discussions on fiber
optics, high energy physics in general and lasers in particular, and deep
space optical telescopy.

Chris Byrne

> -----Original Message-----
> From: rescue-admin at sunhelp.org [mailto:rescue-admin at sunhelp.org]On
> Behalf Of James Lockwood
> Sent: 27 April 2002 08:12
> To: rescue at sunhelp.org
> Subject: Re: [rescue] Fiber loop simulators?
>
>
> On Thu, 25 Apr 2002, George Adkins wrote:
>
> > How about a little tiny box with a pair of ST mounts inside and
> a micrometer
> > screw  for distracting the ferrules from one another in order
> to diminish the
> > signal?
> >
> > or make a series of progressively darker glass windows that you
> could rotate
> > in between them to "Dial A Distance"
>
> This would factor in for attenuation, but not spread due to frequency.
> Remember that even a "square wave" pulse is really a set of sine waves
> after Fourier decomposition, and the speed of light in a medium varies
> depending on its frequency.
>
> Bottom line, your neat square waves:
>    ___     ___     ___
>   |   |   |   |   |   |
> __|   |___|   |___|   |__
>
> Get "smudged" after a few miles of fibre:
>     _       _       _
>   _/ \_   _/ \_   _/ \_
> _/     \_/     \_/     \_
>
> Bad ASCII representation, but you get the idea.
>
> -James
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