Layered Antisymmetry-Constructed Clipped Optical OFDM for IM/DD Systems

In this paper, antisymmetry-constructed clipped optical OFDM (AC-OFDM) is proposed for intensity modulation with direct detection (IM/DD) systems, in which an antisymmetry property is imposed directly in time domain. AC-OFDM has the same spectral efficiency as traditional asymmetrically clipped optical OFDM (ACO-OFDM) but is less complex to implement. Layered AC-OFDM (LAC-OFDM) is then proposed as an extension to further improve spectral efficiency, where different layers of AC-OFDM signals are added in the time domain and transmitted simultaneously. Computational complexity analysis and numerical results show that LAC-OFDM has the same spectral efficiency as layered asymmetrically clipped optical OFDM (LACO-OFDM) and enhanced unipolar OFDM (eU-OFDM) but is less complex in terms of both the number of real multiplications and real additions required. Specifically, LAC-OFDM requires less than half the multiplication and addition operations compared to the comparable LACO-OFDM scheme. Monte Carlo simulation results show that LAC-OFDM has the same bit error rate (BER) performance as LACO- and eU-OFDM.