In two level atoms with doubly degenerated lower levels ($ \ lambda $ - configuration), transitions from the upper level to the lower sublevels correspond to left or right polarization of the light. When relative population of lower sublevels is different, propagation of optical pulses in such medium is followed by polarization switching. This polarization switching occurs randomly in the presence of spatial inhomogeneity of the relative population of the lower sublevels. Maxwell-Bloch equation describing interaction of ultra-short electromagnetic pulses with such atomic system is known to be integrable. Integrality of Maxwell-Bloch equation allows to obtain analytic description for statistical properties of polarization switching. Analytic results are verified by direct numerical simulations