This paper discusses a model of a stellar interferometer based on a mu
ltimode optical fiber of low modal composition, using a broad-band sou
rce. The visibility of the fringes obtained as a result of an incohere
nt model superposition was measured for various sizes of the source an
d states of the atmosphere. The effect of external perturbations on th
e visibility function was also studied. (C) 1996 The Optical Society o
f America.