A novel Optical Orthogonal Frequency-Division Multiplexing（O-OFDM）scheme is proposed for Intensity-Modulated Direct-Detection（IM/DD）systems named Hartley Polar O-OFDM（HP-OFDM）.A large amount of operation time and memory can be saved for the system based on Fast Hartley Transform（FHT）when compared with conventional Cooley-Tukey Fast Fourier Transform（FFT）

which is especially suitable for hardware implementation.It is also noted that the unipolar process of OFDM can be performed in polar coordinate.The simulation results show that the HP-OFDM can provide better BER and Peak-to-Average Power Ratio（PAPR）performances than ACO-OFDM under the same spectral efficiency condition.