Digital baseband predistortion for SSII cancellation in EAM-based direct-detection OFDM systems

To increase the available bandwidth of electro-absorption modulator (EAM)-based direct-detection orthogonal frequency division multiplexing (DD-OFDM) systems, which suffers from dispersion- and chirp-induced power fading, the multiband subcarrier allocation scheme and adaptive modulation formats are adopted. However, the subcarrier-to-subcarrier intermixing interference (SSII) would degrade signal-to-noise ratio on the increased bandwidth and become a bottleneck of the multiband systems. In this paper, a novel digital baseband predistortion is proposed to minimize the penalty of SSII. The experimental results show that a 30 Gbps EAM-based DD-OFDM system with the proposed technique could improve ~3 dB receiver sensitivity compared with the system without the technique over 100 km long single mode fiber transmission and only decreases ~1.0 dB in comparison with the back-to-back situation.