We investigated by H-2 NMR spectroscopy a ferroelectric liquid crystalline polysiloxane (poly11EB1M7-d(2)) derived from the mesogen (+)(S)4-[4'-(1-methylheptyloxy)]biphenyl 4-(10-undecenyloxy)benzoate-d(2) (11EB1M7-d(2)). The labelling on the phenyl fragment allowed us to study the orientational order of such unit. From the analysis of the deuterium lineshapes we could also determine the effect of the magnetic field on the mesogen alignment and the ferroelectric helix distortion. In particular, deuterium spectra showed a contribution due to aligned mesogens in addition to a "Pake-like" one. This was accounted for by considering isotropic distribution of helices, with possible helix distorsion.