Simultaneous ICI and SSBI suppression in microwave photonic SEFDM transmission links using an iterative algorithm with random displacement of constellations

An iterative algorithm is proposed to simultaneously eliminate both the inter-carrier interference (ICI) and the signal-signal beat interference (SSBI) in the microwave photonic spectrally efficient frequency-division multiplexing (SEFDM) transmission systems. The received signal is iteratively modified to minimize the distortion. In each iteration, the modified signal undergoes the fast Fourier transform and the decoding process to obtain the bit information, which is then corrected and remapped into quadrature-amplitude modulation (QAM) symbols again to reconstruct the SEFDM signal for the signal modification in the next iteration. To enhance the performance of SSBI elimination and ICI compensation, random displacement is introduced to the QAM symbols before demapping, which can prevent the iteration from getting trapped in the local optimum. Experiments are conducted under different conditions, which indicate that the proposed method exhibits enhanced capabilities in interference cancellation and signal recovery compared to the conventional methods. Furthermore, the performance of the proposed algorithm in fiber transmission scenarios is experimentally verified. A 16-QAM SEFDM signal with a bandwidth compression ratio of 0.85 is successfully transmitted through a 25.2-km standard single-mode fiber with an error vector magnitude of 5.8 %.