Sparse-fast-Fourier-transform-based quick synchronization for optical direct detection orthogonal frequency division multiplexing systems

Orthogonal frequency division multiplexing (OFDM) has always been a promising candidate for optical access networks. However, it is very sensitive to synchronization errors and requires complex digital signal processing to eliminate this influence, thus increasing the computation complexity, delay, and system cost, which hampers its applications in cost-sensitive and low-latency scenarios of future optical access networks. To deal with this issue, a sparse-fast-Fourier-transform (FFT)-based quick synchronization algorithm for optical direct detection OFDM systems is proposed and demonstrated with greatly reduced computation complexity. Detailed simulations and experimental verifications along 50 km standard single-mode-fiber transmission prove the efficiency, accuracy, and feasibility of the sparse-FFT-based synchronization technique in cost- and delay-sensitive applications for next-generation optical access networks.