All-optical switching based on polarization rotation in SOAs could achieve a fast rate of femto-seconds. The extinction ratio of switching is another important factor. The optical switching operation is realized by the different s of injecting SOAs, and the performance of this optical switching is also influenced by the current selected. We analyzed the relationship between polarization rotation and the current. In our experiments, we realized an optical switching with high extinction ratio of 32dB by the way of increasing the current and optical power injected.