MMI coupler_S parameter


I am trying to improve the example model with 2 output ports to calculate S parameter for single port.
But the S parameters look so weird, S21 is 0.51. S31 is 0.77. The transmission power from 2 ports is higher than input.

The original model is from
MMI_simple.lms (413.2 KB)

Could you please help me to modify my model?
Thank you very much!


Another issue is that the through powers are different. It doesn’t make sense.


Hi @qi.han.1

S parameters show the ratio of electric fields:

If you want to obtain transmission, you need to set the scalar operation to, say, abs(S21)^2.

Regarding your second inquiry, this is because the mode profile on the output waveguides are not the same:

Please make sure that you are choosing the proper mode in each waveguide.


Hi, bkhanaliloo
I figure it out, the default port activated the “use full simulation span” , I need to unclick it.
Thank you very much for your help!