hi atul sharma;
if you are using any optisytem version ,you may see that in layout we can set some data rate—>called the layout data rate
usually by default in any design the data rate in the PBRS at the transmitter end is written in script and is equal to the layout dat rate.
we can not sweep the layout data rate…but we can sweep the data rate in the PBRS…
hope you are clear in this
with regards