  Radio over Fiber (RoF) Systems exploiting a direct modulation of the laser
source are presently utilized within important Radioastronomic scenarios. Due
to the particular operating conditions of some of these realizations, the
phenomena which typically generate nonlinearities in RoF links for
telecommunications applications can be here regarded as substantially harmless.
However, these same operating conditions can make the RoF systems vulnerable to
different kinds of nonlinear effects, related to the influence of the Rayleigh
Backscattered signal on the transmitted one. A rigorous description of the
phenomenon is performed, and an effective countermeasure to the problem is
proposed and demonstrated, both theoretically and experimentally.
