  Our aim is to demonstrate the limitations of using a single component model
to study the magnetic field of an active region filament. For that we have
analyzed the polarimetric signals of the He I 10830 A multiplet acquired with
the infrared spectrograph GRIS of the GREGOR telescope (Tenerife, Spain). After
a first analysis of the general properties of the filament using Hazel under
the assumption of a single component model atmosphere, in this second part we
focus our attention on the observed Stokes profiles and the signatures which
cannot be explained with this model. We have found an optically thick filament
where the blue and the red components have the same sign in the linear
polarization as an indication of radiative transfer effects. Moreover, the
circular polarization signals inside the filament show the presence of strong
magnetic field gradients. We have also shown that even a filament with such
high absorption still shows signatures of the circular polarization generated
by the magnetic field below the filament. The reason is that the absorption of
the spectral line decays very quickly towards the wings, just where the
circular polarization has a larger amplitude. In order to separate both
contributions, we explore the possibility of a two component model but the
inference becomes impossible to overcome as a high number of solutions is
compatible with the observations.
