Fiber-optic beam delivery is commonly used in industrial laser systems
. This article examines the conditions for the optimal propagation of
high power beams through optical fibers. Beam quality effects by step
and gradient index fibers of different lengths are considered. The dif
ferences between the diverging beam from a fiber and the beam at focus
and on the fiber face are illustrated. Estimates are provided of the
worst-case beam quality to be expected from fibers. Guidelines are als
o provided for the selection of beam delivery components based on the
limitations of the optical system and the tasks to be performed.