All-optical two-channel format conversion is proposed and experimentally demonstrated from a 40 Gbit/s polarization multiplexing(Pol-MUX) non-return-to-zero quadrature phase-shift keying(QPSK) signal to Pol-MUX binary phase-shift keying(BPSK) signals by using phase-doubled four-wave mixing effects with two polarization-angled pumps in a silicon waveguide. The eye diagrams and constellation diagrams of the original QPSK sequences and the converted BPSK sequences of each channel are clearly observed on the two polarization states. Moreover,the bit error rates(BERs) of the two converted idlers are measured. The power penalties of all these converted BPSK sequences on both X and Y polarization states are less than 3.4 dB at a BER of 3.8 × 10~(-3). All-optical two-channel format conversion is proposed and experimentally demonstrated from a 40 Gbit / s polarization multiplexing (Pol-MUX) non-return-to-zero quadrature phase-shift keying (QPSK) signal to Pol-MUX binary phase-shift keying (BPSK) signals by using phase-doubled four-wave mixing effects with two polarization-angled pumps in a silicon waveguide. The eye diagrams and constellation diagrams of the original QPSK sequences and the converted BPSK sequences of each channel are clearly observed on the Two polarization states. Both, the bit error rates (BERs) of the two converted idlers are measured. The power penalties of all these converted BPSK sequences on both X and Y polarization states are less than 3.4 dB at a BER of 3.8 × 10 ~ (-3).