On Wed, 5 Apr 2006 12:56:35 -0700, "Joel Kolstad"
wrote:

Richard,

Having done it often, I can say it is far, far simpler than that. It
is obtained through the evanescent mode and optical couplers just like
RF couplers work on the exactly the same principle.

I'm told that this approach is relatively easy to detect in that it requires a
fair amount of mechanical motion to achieve.

Hi Joel,

You mean the actual abrasion preceding the bonding?

Single-mode fiber is often used
to detect minute changes in, e.g., bridges,

Yes, I am very familiar with those applications. They are wholly
devoted to that use, not data.

and the idea is that -- while
there may be other causes of significant mechanical motion to a fiber --
detecting it in the case of a secure line is cause for investigation.

You are describing paranoia. Somehow, I think in the heady dot.com
days when 95% of this stuff was put into surplus, absolutely no one
worried about this. OK, maybe someone, no one here knows who they
are.

I've also been told, however, that you can use completely non-invasive
(mechanically) techniques to sniff fiber... something involving the
back-scatter of neutrons or somesuch. Don't know how much of that was
science-fiction vs. readily doable with the funding of a major government,
though.

Heh heh, that was probably dreamt up by the paranoid ones. Experience
has always shown that "security experts" (those who roll their own)
are the most vulnerable. You don't need advanced degrees in
interstellar physics to read their mail. Simply look at the DVD
encryption model. It was busted by 35 lines of code. Look at
Homeland Security, and then think Katrina.

73's
Richard Clark, KB7QHC