A theoretical model of a dual-channel polarization optical transmission system is analyzed,using two semiconductor optical amplifiers (SOAs) to achieve all-optical polarization modulations with two input data streams.In this model,the signal polarization modulation is completed by utilizing the cross polarization modulation (XPolM) effect in the SOA.A rate equation of the tensile-strained bulk SOA is adopted in the model.With this model,the dynamic characteristics of the system in respects of the amplification and the phase difference of the probe light in SOAs,signal polarization multiplexing and demultiplexing are investigated numerically.The simulated and experimental results are well consistent.