Improve output signal quality from Stratix IV GT transceiver

Hi All

I am evaluating 10G gigabit ethernet transceiver (using ALTGX macro) on Stratix IV GT FPGA (EP4S40G5H40I1).

I did the test on FPGA board by loopback (port itself and between ports) at SFP.

I just achieved bandwdith 10000Mbps in each port while my target is 10312.5 Mbps.

Now I want to improve the output signal quality from FPGA pins to SFP connector by setting the analog parameters of ALTGX macro in MegaWizard but I don't unsderstand the analog deeply.

Could you give me some tips for setting these parameters or show me some ways to improve the output signal quality from transceiver?

Thanks

Thuyet