All optical two channel polarization multiplexing format conversion from QPSK to

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 effect