Tuesday, December 17, 2013

Photons vs. Electrons

At ten gigabits ethernet over copper cable really struggles. Everything has to be just right and even well terminated twisted pair cable is on the hairy-edge.

On the job that I've just finished had a lot of fibre and copper data and the time to test (on a per circuit basis) is much higher for copper than fibre. With OM3 fibres so long as you have an acceptable sub-3dBs of attenuation at 850nM ten gigs is a doddle. We had to re-terminate maybe half a dozen circuits and using our INNO core-alignment splicer it takes no time. On the other hand getting the copper data cables right is a mission with Near-end cross-talk, alien cross-talk and return loss all having the be measured across four pairs. The output (above) is from our Fluke DTX-1800 analyser.

As an aside, one of the freelancers I use a lot showed me a brilliant trick with fibre panels); the BT standard for core-order involves having the coloured and striped cores 12 couplers away from each other in a 24-port panel. The better way is to put the coloured and striped cores next to each other in the same duplex pair so that if you make a mistake it's easily rectified at test-time.

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