Hi, I run your code and can duplicate your result, except the multiplier issue mentioned somewhere else.
FDE solver somehow interpolates the refractive index of the fiber and the taper, this is why we got riedge waveguide profile + fiber. If you only want to analyze mode properties using FDE, a simple way is to modify the x position of FDE:
for fiber, set x=-1um; for taper set x=1um. With those modifications I got two results for the two waveguides:fiber and the taper.