As the 100Gbit/s Ethernet (100GbE) has gradually become a commercial reality, the next step of migration is toward 1Tbit/s Ethernet transport.Coherent optic al orthogonal frequency division multiplexing (CO-OFDM) has recently drawon muc h attention to improve system capacity and transmission distance over fiber for its superior performance in spectrum efficiency,robust chromatic dispersion (CD) tolerance,receiver sensitivity,and polarization mode diversity (PMD) resilience ,which has also been considered as a promising candidate for long-haul transmis sions.In conventional optical OFDM systems,analog-to-digital converter (ADC) a nd digital-to-analog converter (DAC) are needed at transmitter and receiver,re spectively.However,the radio frequency (RF) bandwidths and sampling rates of ADC and DAC are limited by current manufacturing.To overcome this problem,an 8×112Gbit/s all-optical OFDM transmission system is proposed in this paper.A sing le laser source is utilized to generate frequency comb source as the sub-carrie rs of the proposed all-optical OFDM system with frequency spacing of 28GHz by differential Mach-Zehnder external modulator.Each of 8carriers of the comb sou rce is encoded with 112Gbit/s polarization division multiplexing quadrature phase shift keying (PDM-QPSK).At the receiver,optical fast Fourier transform (FFT) is performed by cascaded Mach -Zehnder delay interferometers (MZDIs) to de-multiplex the all-optical OFDM s ignal into 8lower bit rate sub-carrier tributaries which can then be individua l ly processed electronically.The back-to-back simulation results show that the optical signal-to-noise ratio (OSNR) penalty of 8×12Gbit/s all-optical OFDM is about 9dB compared with 112Gbit/s single carrier system at bit error rate (BER) of 10－3,and its is available to update the current single car rier system using all-optical OFDM and common coherent optical receiver while w ithout introducing signal impairment.