Diversity Combining in Layered Asymmetrically Clipped Optical OFDM

We describe a new receiver for layered asymmetrical clipped optical orthogonal frequency-division multiplexing (LACO-OFDM) in which diversity combining is used at each layer to improve the performance. In each layer of LACO-OFDM, some subcarriers carry data and others carry only the components which result from clipping. In the new receiver at each layer, a nonlinear process is used to recover this clipped signal and use it for diversity combining. Simulation results show that the new receiver outperforms a conventional receiver by up to 2 dB when two layers are used. The performance of LACO-OFDM with diversity combining is compared with other forms of optical OFDM. The results show that at high bit rates LACO-OFDM with diversity combining is the most power efficient system, while ACO-OFDM with diversity combining but without layering is the best for low bit rates. In addition, the diversity combining receiver is compared to the recently proposed receiver for LACO-OFDM based on the noise cancellation. Results show that the diversity combining and noise cancellation have the same performance over flat channels. However, over frequency selective channels, the diversity combining receiver has better performance.