circuit detect fiber cut

[moh_monem43]

detect fibre cuts

i work in fiber NW, when fiber cut we take long time to find cut point
so need to build circuit can detect the fiber cut point.
my idea that we send laser signal in fiber, and we passes circuit on fiber long this circuit receive laser signal , at cut point this circuit miss the signal and give alarm.
any one can help me???
thanks

 

[tomic]

detect fiber cut

Maybe you could look at TDR or Time Domain Reflectometry. That's what is used to detect cuts along transmission lines.

Hope this helps.

Tomic

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www.tom-ic.com
Your reliable prototyping partner.

 

[Eugen_E]

how to detect fiber cut

You need an OTDR, which usually costs > 10000$.
If you just want to see if the fiber is cut, not to determine the exact position, you can use a LED source and optical power meter.

The OTDR it's too complicated to build yourself, it includes a high performance optical sistem, LASER and photodiode, and a precision timebase. The optical detector should have very high sensitivity, because the reflected power is very small compared to the transmitted power. Also it should have very high dynamic range.
The LASER and photodiode are coupled to the fiber using an optical directional coupler - another component impossible to get at the hobby level.