Asymmetrically Clipped Optical Fast OFDM Based on Discrete Cosine Transform for IM/DD Systems

We propose an asymmetrically clipped optical fast orthogonal frequency-division multiplexing (ACO-FOFDM) based on discrete cosine transform for intensity-modulated and directdetection systems. We demonstrate that the asymmetrically clipped technique can be applied to FOFDM, and derive a statistical characterization of clipped FOFDM. The key parameters of ACOFOFDM, including spectral efficiency, complexity, bit-error-rate (BER) performance, and power efficiency, are analyzed. Compared with ACO-OFDM based on fast Fourier transform, for the same spectral efficiency, ACO-FOFDM has the same power efficiency and BER performance but a lower computational complexity for digital signal processing. Compared with pulse-amplitude modulation (PAM) and DC-biased optical FOFDM (DCO-FOFDM), ACOFOFDM offers superior power efficiency for a bit rate/normalized bandwidth of less than 5. When the bit rate/normalized bandwidth is 2, the required ratio of optical energy per bit to a single-sided noise power spectral density (E
_b(opt)
/N
₀
) for a BER of 10
^-3
in ACO-FOFDM is approximately 5 dB less than that in PAM or in DCO-FOFDM with a 7-dB DC bias. Moreover, ACO-FOFDM is more cost effective and better suited to adaptive systems because no DC bias is needed. Finally, we demonstrate a transmission experiment using a 50-km standard single-mode fiber to verify the feasibility of ACO-FOFDM.