Joint Channel and Carrier Frequency Offset Estimation and Correction for Coherent Optical FBMC/OQAM System

Chromatic dispersion and laser frequency offset have serious impact on coherent optical filter bank multicarrier systems with offset quadrature amplitude modulation (CO-FHMC/OQAM system). Preamble-based joint estimation and correction algorithm of channel and carrier frequency offset (CFO) in CO-FHMC/OQAM system is investigated. The channel transmission model of CO-FHMC/OQAM system is theoretically elaborated, and the preamble structure is deliberately designed and optimized to suppress the impact of inherent imaginary interference (IMI). In order to reduce the noise impact, an estimation method based on inter-frame averaging is proposed. In this method, the cross-correlation function within multiple frames is averaged and the laser frequency offset according to the phase of this average is estimated. Finally, we get the final channel response by averaging channel estimation results within multiple frames. The error amplitude vector and error rate of the system arc numerically demonstrated through 1500 km standard single-mode fiber transmission with different CFO values. The results show that the proposed method can suppress the influence of chromatic dispersion and laser frequency offset, and significantly enhance transmission performance in the back-to-back scenario or after 1500 km optical fiber transmission.