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/gamm
a ray source coupled with a cold accretion disk. The source radiates by inv
erse Compton process. We show that very low optical depths (tau similar to
5.10(-4)) are required for the 2nd Compton order to be negligible. Such opt
ical depths can be reached only if the source is very close to the disk (co
rona-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 strong
ly angle dependent spectrum with a reflection component much stronger than
in standard isotropic models, leading to unobserved reflection dominated sp
ectra at low inclination.