Hi Shahid, Now that you want to use different bit rates for the upstream and downstram, you can set the bit rate in the global parameters to 2.5 Gbps and then go to the second tab (PRBS) in the WDM Transmitter, change the value of Bit rate to “Bit rate/2” in script mode. This way, the upstream bit rate will be 2.5/2=1.25Gbps and whenever you change the downstream Bit rate, the upstream bit rate will automatically be set as half the value of the downstream.