How does BER compare between different 10GbE physical media?

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http://serverfault.com – I am under the impression that you should use optical for 10GbE networking because of a BER (bit error rate) several orders of magnitude lower than copper. I'm pretty sure I previously found documentation stating so, but for the life of me I just cannot find it. I'd like to see documentation on typical BER (in general, if such a thing exists) for: 10GBase-T ports (with Cat6a cabling) 10GBase-CX4 ports 10GBase-T SFP+ modules (Cat6a cabling) Fiber SFP+ SR modules DAC SFP+ modules (HowTos)