Joint Estimation Algorithm of Time Offset and Channel Response for Coherent Optical FBMC-OQAM Systems

An innovative joint estimation algorithm for coherent optical filter bank-based multicarrier systems with offset quadrature amplitude modulation was proposed. The training sequence design enables simultaneously time synchronization and channel estimation. Thus, the proposed algorithm effectively improves spectral efficiency. First, the conjugate symmetry condition of the time domain waveform was derived from the system model. Based on the derived condition, a time synchronization method was proposed. The proposed method combines the pseudo-random sequence with conjugate symmetry to improve time synchronization accuracy. Then, channel estimation was performed based on the principle of dual-dependent pilots. The method avoids the impact of intrinsic imaginary interference and maintains the conjugate symmetry of the time domain waveform. Finally, numerical simulations were performed to investigate the system's transmission performance. The simulation results demonstrate that the proposed algorithm can effectively accomplish joint estimation of the time offset and channel response.