communicatiom between external board running CDR and FPGA

hello

if i want to change the transmitter to transmit at data rate compatible with the SERDES like 1.25 Gbps because it 10 * 125 MHZ which is my ref clock .

what i have to do to achieve the TX 1.25 is in side Startix GX FPAG and in the other side and RX anther board with Startix GX .

these tow boars connected through optical link.

??

thanks