zahra mansouri

i placed a mode expansion monitor in the cross section of waveguide along the propagation direction for finding the T forward and T backward. the propagation direction is along the +z direction. my purpose is to find the how power tansmitted along waveguide lenght. i send my designed structure picture in fdtd. the biggest monitor is mode expansion monitor and the others are power monitors. the soucre is at the bottom of the waveguide. i think that the proper coupling doesnt occure . how can i know that my excitation is true?is it normal that t backward be larger than t forward?