The All-Optical Orthogonal Frequency-Division Multiplexing（AO-OFDM） technology is used to implement multicarriers and Optical Inverse Discrete Fourier Transform（OIDFT）/Optical Discrete Fourier Transform（ODFT） by way of optical processing

which has the advantages of improving the processing rate and reducing power consumption.By using the AO-OFDM technology in combination with the single-channel 100 Gbit/s DP-QPSK high-order modulation technology

we can realize a 400 Gbit/s transmission system with a spectral efficiency of 2.7 bit/s/Hz and when the chromatic dispersion is completely compensated

we achieve a transmission with the maximum Spectral Efficiency-Distance Product（SEDP） of 3 564 km·bit/s/Hz.With 12.5% Optical Cyclic Prefixes（OCPs） inserted

the system dispersion tolerance reaches 70 ps/nm.The experimental results show that using the AO-OFDM technology

the system has better performances and can be used as a practical application scheme for next generation 400 Gbit/s transmission systems.