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
z : distance from the lens to the waist of the incident beam
lam : wavelength
fi : back focal length of the lens
wf : mode radius of the fiber optic
T : transmission coefficient at the entrance of the fiber optic
dx : lateral shift of the fiber optic along X axis
dy : lateral shift of the fiber optic along Y axis
dz : defocus of the the fiber optic along Z axis
tiltx : tilt of the fiber optic around the X axis
tilty : tilt of the fiber optic around the Y axis
zix : distance from the lens to the waist in the XZ plane of the refacted beam (which is also the distance from the lens to the fiber optic entrance without misalignments )
C : coupling ratio