From: jim bell <jimbell@pacifier.com>
Date: Wed, 24 Jul 1996 05:53:01 +0800
To: Rabid Wombat <wombat@mcfeely.bsfs.org>
Subject: Re: Bare fibers
Message-ID: <199607231824.LAA11873@mail.pacifier.com>
MIME-Version: 1.0
Content-Type: text/plain


At 05:19 PM 7/23/96 -0400, Rabid Wombat wrote:
 
>> It occurs to me that a bare fiber could actually be (randomly) hung across 
>> treetops, roofs, power lines, and various other structures, over a 
>> many-block distance in suburban areas.    Such a fiber wouldn't be 
protected 
>> very well, but it would probably last a few months.  It would also be 
>> exceedingly hard to find its terminations, and tracing it would be a real 
>> pain.  (It probably wouldn't be visible against a bright sky more than a 
>> meter or two away.)
>
>It also would have little structural integrity - if you attached it to
>trees, which sway in the wind, you'd have a broken fiber in a short time.
>(The fiber doesn't even need to break, per se; microscopic cracking,
>usually at the cladding, will ruin your fiber) (bird strikes would also be
>a big problem, mostly for the bird)

But how long?  I don't doubt that the effects you describe will occur, but 
I'm only talking about a _semi_-permanent installation.  My guesstimate 
(months) was based on the idea that the fiber would be short (say, less than 
a kilometer)enough so that even accelerated loss (microcracking) wouldn't 
appreciably degrade the transmission.  Also, I'm assuming that the fiber 
would be hung with enough slack so that swaying/growing trees wouldn't 
stretch the fiber appreciably.

>ob crypto/privacy: Anybody have a good idea for detecting a tap on 
>exterior fiber? I'd expect an attacker to have to interupt connectivity, 
>terminate both ends of a break, and insert an active device. Thoughts?

They can tap a fiber by bending it over a small radius, which causes leakage 
around the OD without appreciably interrupting the signal.  Changes are 
pretty good that this would b
e the technology used.
Jim Bell
jimbell@pacifier.com