Maximum Length for 1000Base-SX

Sep 14, 2006 3 Replies
W

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 =B5m?



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 =B5m fiber?



TIA



Wrolf



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S

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).

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W

Turns out one run is 1500', with a single SC-SC patch panel at each end.

The other run is about 2000', with a single SC-SC patch panel at each end, and a pair of SC-SC panels in the middle. The patch panels will all be tested for maximum 0.3dB loss per mated pair.

Wrolf

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