Systems of mutually coupled semiconductor lasers are widely used in optical chaos communication, spread spectrum communications and high power emissions. The chaos pass filtering effect and synchronization behaviors of mutually coupled semiconductor lasers are studied numerically in this paper. Single-mode rate equations are extended to two polarization modes. By selecting X-polarized mode for mutually coupling, not only chaotic dynamics and synchronization are obtained, but also Y-polarized modes are totally restrained, so pure polarization mode synchronization is realized. A frequency detuning is introduced to keep the first laser as a leader. Simulation results show that outputs of the leader and laggard lasers exhibit high frequency fluctuations in company with symmetry breaking and they are synchronous with a lag equal to the external delay. The system shows similar chaos pass filtering effect to unidirectionally coupled semiconductor lasers when the leader is modulated, while chaos pass filtering is bad when the laggard is modulated.