dark fiber and sfp distance limitations

Mikael Abrahamsson swmike at swm.pp.se
Sat Jan 2 23:19:04 UTC 2010

On Sat, 2 Jan 2010, Justin M. Streiner wrote:

> Some OTDRs (or, more correctly, fiber test sets that include OTDR 
> capabilities) are multi-function devices that will show you the overall 
> length (assuming the span is not broken somewhere in the middle), of the 
> span, plus attenuation and reflections (spikes) at your desired wavelength in 
> one complete package.

Well, that I can understand, what I can't understand is why someone would 
*ONLY* do OTDR. Attenuation testing end-to-end (as opposed to classic OTDR 
that do the testing from single end) is needed for accurate measurements, 
and if it shows something strange, then it's warranted to break out the 
OTDR. If your equipment can do both in one go, fine.

> I'm a big believer in running my own tests when possible, and not just 
> relying on $provider's word.  It also allows me to verify what their 
> engineering reports tell me about the condition of a span.

I guess it's all a matter of how much effort you want to put into 
provisioning. Personally I'm happy enough if the DOM readings (indicating 
attenuation) on the optics seem reasonable considering the distance of the 
fiber. If they seem strange, then yes, by all means, break out the testing 

Mikael Abrahamsson    email: swmike at swm.pp.se

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