Hello Gustas,
Modal injection into tapered fibers is a tricky thing as the mode profile is dependent on position in the taper and depending on the rate of the taper you can have really unexpected results. To this end by default you cannot selected tapered waveguides for modal injection. There are 2 solutions:
- Have a small section of linear waveguide with the same profile as the start of your taper and setup the modal injection on this.
- The newer product provides the option for a “cross section slice” which uses the refractive index along the input plane for the modal calculation regardless of what is setting the refractive index along those points. Overall I would recommend checking out the evaluation of the product as it has gone through some significant updates since that free version was split off and made available.