Collimated beam diameter of a singlemode fiber
Beam path of a collimated beam exiting a single-mode fiber with angled connector FC APC.
The collimated beam diameter Øbeam is a function of the collimating focal length f’ and the numerical aperture NA of the single-mode fiber.
For a specified fiber NAe2, the beam diameter Øbeam (defined at its 1/e2-level) for a focal length f’ is given by:
Factor FNA depending on the nominal NA %-Level.
Beam diameter: f' = 12 mm
Effective numerical aperture of fiber: NAe2 = 0.08
Focal length: Øbeam= 2 ⋅12 mm ⋅ 0.082 = 1.92 mm