Performance of two dimensional asymmetrically clipped optical OFDM

In this paper, the technique of asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM) has been extended to a two dimensional (2D) optical communication system. Simulation results for the performance of 2D spatial ACO-OFDM (SACO-OFDM) in the presence of additive white Gaussian noise (AWGN) are presented. The bit error rate (BER) and optical power efficiency of SACO-OFDM are investigated for 4, 16 and 64-QAM constellations. It is shown that SACO-OFDM with 16-QAM modulation has the same spectral efficiency as 2D spatial DC biased OFDM (SDCO-OFDM) system with 4-QAM but requires 4.5 dB less optical power for a given BER. It is also shown that the use of a cyclic prefix makes the new system tolerant to spatial misalignment between transmitter and receiver.