Fiber Optic Perimeter Security Sytems

[Loopee]

I'm just getting in to a security upgrade for a client who now uses microwave tx/rx technology to protect against perimeter breaches. I see that there is now another technique used similarly that senses for a disturbance in the light sent through a fiber optic cable that would be attached to a perimeter fence.

Sophisticated algorithms analyze the light perturbations and filter out motions caused by wind, squirrels, etc.

If anyone has experience with a fiber optic perimeter system I'd love to hear how it did or is doing. Are the algorithms really effective in elimination normal background effects? Expense? Maintenance required?

Thanks,

Loopee

 

[itsmoked]

Not something you'd want to cobble up...

I suspect they work fine from whoever supplies them. It would take a bunch of study to get it right but that's what companies do.

I'd call a supplier and ask for references then talk to their users directly.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[CharlieGill]

Gee Keith, don't be a wet rag. This sounds interesting.
It's not clear to me whether the microwave technology is used to detect an intrusion or just relay the detection (by conventional sensors).
From my Navy days I know that fire control radar can track pelicans so I assume a millimeter band beam could detect a human body crossing a perimeter boundary.
Not sure about the fiber optic. I guess a multi-mode fiber might show detectable characteristic shifts when bent, but it doesn't impact normal data pulses.
I'd be interested in knowing the technology involved.
Charlie

 

[itsmoked]

The signal is altered as you compress, bend, or stretch any fiber. Communications is digital so as long as the injection power is great enough the data goes thru. However if you inject a fixed power you can see changes in the received power fairly obviously.

All you have to do is digitalized the output and analyze it. It's not hard, just tedious and very time consuming to get down all the various environmental disturbances.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jimkirk]

You could also do an optical TDR on the fiber. That will locate where, along the cable, a disturbance is. Characterize them to distinguish magnitude (human or squirrel, for example).

 

[VEBill]

I believe that JK is correct. Based on what I've read, they operate using fairly simple TDR techniques. Take a baseline and highlight the real-time deltas.