Guilin Sun
Ansys Employee

Is there any gap between the fiber and the edge coupler?

a mode can only be supported inside a waveguide or fiber.

If the field needs a certain propagation distance before coupling, you can use the import source from the first simulation. If they are end-to-end coupling without gap, it is better to have the fiber in the simulation.

I do not know the configuration of your device so just give you some general suggestions.