  We developed a non-linear Monte Carlo code based on the LP method proposed by
Stern et al (1995). We use it to simulate an extended non-thermal X/gamma ray
source coupled with a cold accretion disk. The source radiates by inverse
Compton process.
  We show that very low optical depths are required for the 2nd Compton order
to be negligible. Such optical depths can be reached only if the source is very
close to the disk (corona-like geometries). And even in this configuration, 2nd
Compton order is negligible only for the hardest observed spectral slopes. We
also account for Compton reflection on the disk. This kind of coupling leads to
a strongly angle dependent spectrum with a reflection component much stronger
than in standard isotropic models, leading to unobserved reflection dominated
spectra at low inclination.
