The attachment is my design. I am trying to use Physical optics propagation to find out the output beam size, but POP result is weird when I include a paraxial lens (surface 1) into the propagation and set the gaussian beam waist to be the beam size of the input fiber waist. But when I exclude the paraxial lens(start propagation from surface 2) and set the gaussian beam waist to be the beam width after the paraxial lens, the result becomes more reasonable. 

1. Does POP accept paraxial surface? 


2. When I define the gaussian beam waist in POP, is the waist location always assume to be at the starting surface?

Thanks!