Schematic picture of the IC e^± cascade that develops within the jet volume (not to scale). The primary γ-ray photon, ϵ₀, is injected at the jet base located at z₀. The photon is absorbed in the synchrotron radiation of the inhomogeneous jet. The secondary e^± pair is created as a result of the absorption at a distance z_abs. This e^± pair is isotropized in the random component of the magnetic field of the jet. It is rather advected with the jet plasma. The e^± pair is cooled down, producing synchrotron radiation and secondary γ-ray photons in the IC process. These secondary photons, ϵ₁, created at a distance z_em, can be also absorbed or escape from the jet.