  Coupling efficiencies of an electromagnetic field with a Kolmogorov phase
statistics into a step-index fiber in its monomode regime of wavelengths are
computed from the overlap integral between the phase screens and the far-field
of the monomode at infrared wavelengths. The phase screens are composed from
Karhunen-Loeve basis functions, optionally cutting off some of the eigenmodes
of largest eigenvalue as if Adaptive Optics had corrected for some of the
perturbations. The examples are given for telescope diameters of 1 and 1.8 m,
and Fried parameters of 10 and 20 cm. The wavelength of the stellar light is in
the J, H, or K band of atmospheric transmission, where the fiber core diameter
is tailored to move the cutoff wavelength of the monomode regime to the edges
of these bands.
