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Power efficient and cost-effective solutions for optical OFDM systems using direct detection

In this paper, we present optical orthogonal frequency division multiplexing (O-OFDM) systems using direct detection (DD), suitable for cost-effective applications. A scheme based on discrete Hartley transform (DHT) is proposed and compared to standard O-OFDM implementation. Both asymmetrically clipped (AC) and DC-biased solutions are analyzed for intensity-modulated DD systems. We show that AC is a power efficient technique that can be implemented without Hermitian symmetry constraint. The use of DHT for OFDM modulation/demodulation results in a simpler system using real constellation with lower size. The same performance as FFT-based O-OFDM is achieved.