Triple-layer hybrid optical OFDM scheme for passive optical network

Orthogonal frequency division multiplexing (OFDM) based on intensity modulation and direct detection (IM/DD) is a promising candidate for future passive optical network (PON). As the IM/DD system requires the output to be unipolar, a direct current (DC) is required but with a reduced energy efficiency. Asymmetrically clipped optical OFDM (ACO-OFDM) has been proposed to improve the energy efficiency at the cost of a lower spectral efficiency. With infinite layers’ superimposition, layered ACO-OFDM (LACO-OFDM) can significantly improve the spectral efficiency while the computation complexity is very high. In this paper, we propose a triple-layer hybrid optical OFDM (THO-OFDM) scheme for PON, which combines N-point ACO-OFDM, N/2-point ACO-OFDM and N/2-point PAM-DMT signals for simultaneously transmission. Compared with LACO-OFDM, the proposed THO-OFDM offers better spectral and energy efficiency, reduced peak-to-average power ratio and computation complexity. The simulation results show that the transmitted THO-OFDM-PON can attain a ∼1.2 dB power gain compared with the LACO-OFDM-PON over 20 km fiber link.