Dear Mohamed,
please refer to Figure 1 in the Global Parameters Reference Guide document that you may access it from the following link for guidance.
You could set the proper parameters for the samples/bit, sequence length which will affect the time window and frequency window as explained in the reference guide.
If you’d like to get arbitrary pulses (On/Off) then use PRBS generator component, else use the User-defined bit sequence generator and choose Alternating zeros and ones.
C:\Program Files\Optiwave Software\OptiSystem 17\documentation
Regards,
Ahmad