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I need to re-connect the network to a small old outbuilding that hasn't been used in several years. I have to use the existing 62.5um multi-mode fiber run. This end of the fiber is already connected. For the end in the building, I was looking at this pair:

http://www.tp-link.com/products/productDetails.asp?class=switch&content=spe&pmodel=TL-SM311LM http://www.tp-link.com/products/productDetails.asp?class=&content=spe&pmodel=TL-SL2210WEB

If you look at the sfp first (first link), it's listed at 1.25Gpbs. That's odd, because IIRC the fiber should really only do 1Gbps. It's also supposed to work with the switch I posted (2nd link), but the gbic port on the switch also only shows 1Gbps. What am I missing here?

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1 Answer 1

up vote 4 down vote accepted

afaik 1.25GBit/s is physical layer bit rate; you need to deduct from it error-correction overhead and you get 1Gbit/s of 'usable' bandwidth.

[ look here too ]

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Gigabit Ethernet uses 8b/10b encoding to maintain voltage balance and clock recovery. See the wiki article for more details, but sufficient to say you lose 25% baud to bandwidth: en.wikipedia.org/wiki/8b/10b_encoding –  Chris S Jun 15 '10 at 15:50

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