Reply To: Question on S matrix and mode overlap in FDE

[Guilin Sun]

This is a more theoretical question than simulation. The published result is optimized to excite only one mode, so using the above definition is correct. When you have higher transmission efficiency, it may indicate that high modes are excited and somehow the higher order modes convert to the fundamental modes, during their propagation through the taper. I would suggest that you do more mode analysis, and also using higher order modes to test the taper its self to see its conversion. Please make sure the mode source is not truncated by the applied boundaries.