Parameters
wx : half width of the incident beam waist in the XZ plane
wy : half width of the incident beam waist in the YZ plane
M2x : M square factor (M2) of the elliptical beam in the XZ plane
M2y : M square factor (M2) of the elliptical beam in the YZ plane
lam : wavelength
fi1 : effective back focal length of the first lens
fi2 : effective back focal length of the second 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
C : coupling ratio