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Posted by stephen on September 18, 2006, 6:55 pm
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Wrolf wrote:
> Can I calculate the maximum run length for 1000Base-SX based on:
>
> Max dB Loss (7.5dB) > # patch panels * loss per mated pair + distance
> attenuation
>
> Where loss per mated pair is nominally < .75 dB, but we test for < .3
> dB;
>
> and distance attenuation is 3 db / km
>
> And thus exceed 220 m over 62.5/125 µm?
the limit i learnt was 260m.
No - the limit isnt power loss, it is model dispersion (ie pulses go via
different paths thru the cable and overlap).
So it actually depends on your m/mode cable type - higher bandwidth /
distance product means you can stretch the limit.
1 easy way to get further is to use LX GBICs and mode conditioning patch
leads - that gives you 550m (the same as 50 um fibre).
Any more than that then you need a switch at an intermediate point, single
mode - or you just "wing" it and hope there is enough slack in the spec for
your install that it works.
FWIW i have seen 1200m work on old 50 u cable (over a decade ago now, when
we put the 1st Bay Networks layer 3 switches in - we didnt have the extra
slot for the single mode card).
>
> Do I count the switch to patch cable as a mated pair, or is that
> included within the
>
> How about modal dispersion? Is there a calculation for that?
>
> Or do I have to run replacement 50 µm fiber?
--
Regards
stephen_hope@xyzworld.com - replace xyz with ntl
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