Parameters
wo : radius of the incident beam waist in the XZ plane
M2 : M square factor (M2) of the gaussian beam
z : distance from the lens to the waist of the incident beam
lam : wavelength
fi : effective back focal length of the lens
Dfo : core diameter of the multimode fiber optic
NA : numerical aperture of the multimode fiber optic
T : transmission coefficient at the entrance of the fiber optic
zi : distance from the lens to the waist of the transmitted beam
C : coupling ratio