Thanks for reading my problem. Recently I was measuring the transmission at the through port of a ring resonator. The ring’s x span is 0, so it doesn’t overlap with the waveguide. But when I changed the mesh order of the purple ring in the figure, and remained other parameters totally the same, it showed a very different spectrum in the through port.
I was very puzzled because I thought mesh order served no role for objects which do not overlap. So where the problem is?