Sorry for the delay. As I understand it, you are observing the loopback test with optical module seems unable to receive data correct at data rate >7Gbps. Lower than 7Gbps, there is no issue. This seems to be trending to signal integrity issue. To further narrow down, just wonder if you have had a chance to test enabling internal serial loopback and test at data rate >7Gbps to see if data can be received correctly. This would be helpful to narrow down to signal integrity issue.