Problem with eye diagram noisy

hi!

I current testing my transmitter with I/O LVDS interface. One weird thing when i run with input 1 Gbps , the output eye diagram is very nice but when i run with input 600 mbps, the output eye diagram become very noisy. What would be the course ? Is it impedance matching issue or related to quality of PCB board?

Tx for your reply.

usually, your amplifier need larger bandwidth

"Is it impedance matching issue or related to quality of PCB board?"

Shouldn't be neither of those two options, since you're evaluating your circuit at lower bit rate. Sounds strange...

Please explain your circuit and test method further.