Not if you are in the business of spying! grin It takes a machine that
can penetrate or couple to the fiber without damaging its throughput
(much). I mean given that fiber splicing uses a pretty expensive machine
itself I doubt am eavesdropping device would be much harder to
manufacture... Your next big expense is to sort through the reams of
data that pass through the link!

Do you see it as being viable for amateur radio hobbyists or was your
post for general technical interest only? Perhaps I am missing some
possibilities here..

Cheers Bob

Marco Licetti wrote:
OK. Just one comment: intercepting fiberoptics is more complicated/costly
than metal "wires"

On Sun, 02 Apr 2006 22:31:06 -0500, Bob Bob wrote:

It takes a machine that
can penetrate or couple to the fiber without damaging its throughput
(much).

Hi Bob,

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. You simply abrade
the surfaces of two conjoined lengths of fiber optic; mate them like
snakes along their length; and wah-lah as the French would say.

73's
Richard Clark, KB7QHC

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

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.

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

Howdy!

A few comments on fiber:

1 - we cannot confuse bandwidth (MHz) with bitrate (Mbps or Gbps). Two
different monsters. Currently CATV uses fiber optics to transmit TV
signals over RF, also called analogue video. You will need, of
course, a transceiver on both ends, which will be powered by
electricity that will then "power" an antenna. That would be an
awesome solution (if economically feasible for HAMs) in places with
lots of lightning storms (e.g. Florida). If a lightning hits an
antenna the only things fried would be the antenna itself and the
transceiver. Since fiber is dielectric (assuming the use of an
all-dielectric cable also) the radio would be fine if not surge came
through the power line. Fiber optics can have (depending on the
type) TeraHertz in terms of bandwidth and transmit TeraBits of
information per second using techniques such as Dense Wavelength
Division Multiplexing, which is simply sending multiple colors (or
wavelengths) through it.

2 - tapping into fiber. Not so easy as mentioned above.
Transmitters can be equipped with optical power variation detection and
the system themselves can also detect variation in the BER (bit error
rate) that would raise if someone tries to tap into fiber. Those two
controls make fiber virtually impossible to undetected tapping.
"Shaving" fiber by eroding its coating will only make the intrusion
even more noticeable since there will be a big optical power loss in a
certain point of the link. That point can be precisely detected
within a few feet range by using an OTDR (optical time domain
reflectometer) that can locate the failure in seconds and, depending on
security level of the link, let the security personell take
"appropriate care" of the "spy". So, do not try this at home.

It is easier to hack into someone's network via computer code than via
the optical physical medium.

Cheers!