We develop a general formalism for describing the polarization effects in stellar interferometers. We show that celestial field rotation and phase delays between the s and p fringe patterns are first order effects. Experiments in laboratory partially check our modeling and thanks to these measurements we optimize a field rotator to compensate the visibility losses due to celestial field rotation. Then we predict the visibility functions of the Grand Interferometre a 2 Telescopes (GI2T) of the Observatoire de la Cote d'Azur with its present beam combiner and with the future Recombinateur pour Grand Interferometre (REGAIN): the field rotator enables an increase in the observation time by more than 3 hours. Finally, we compare our results to observations done with the GI2T and we emphasize the importance of such calibrations with a polarimetric mode whose principle is validated.