You can either use the default source pulse or create your own: https://optics.ansys.com/hc/en-us/articles/360034383114-Creating-a-custom-source-time-signal-for-an-FDTD-source
example:
https://optics.ansys.com/hc/en-us/articles/360042800113-Group-delay-analysis
But for the waveguide delay, you can accurately use FDE to get:
https://optics.ansys.com/hc/en-us/articles/360042800453-Waveguide-FDE
You are navigating away from the AIS Discovery experience