Beam divergence of a single-mode fiber
Beam path of a collimated beam exiting a single-mode fiber with angled connector FC APC.
From principle, a collimated beam has a divergence greater than zero, i.e. the beam diameter varies with distance A from the fiber collimator. The beam divergence θ depends (for large distances of A) on the beam diameter Øbeam at the position of the fiber collimator and on the wavelength λ.
Wavelength λ = 660 nm
Focal length f’ = 12 mm
Numerical aperture NAe2 = 0.08
Beam diameter Øbeam = 1.92 mm
Beam divergence θ = 0.22 mrad