In this paper, analytical forms of the Jones matrix of a polarization-maintaining (PM) optical fiber have been obtained, taking into account a slight deviation of the real fiber of this type from its ideal representation by the linear phase plate model. The derivation was made within the framework of the polarization element model with phase anisotropy. The features of using different variants of matrices in simulation were considered. The results could be used to describe practical fiber-optic circuits with PM fibers, simulate their signal, and analyze the effect of polarization mismatches in the circuits’ work. The experiments revealing deviations of the parameters of the polarization modes of real PM fibers from the idealized model and allowing estimation of the level of this deviation were performed.