Dual-Stage Cascaded Frequency Offset Estimation for Digital Coherent Receivers

Frequency offset estimation is a key function in carrier phase recovery to enable digital coherent reception. We propose a novel, feed-forward, dual-stage frequency offset estimator, and demonstrate its performance through both simulation and experiment. Our simulation results show that the estimation range can be as large as ± 9 GHz for a 10.7-GBaud polarization-multiplexed (PolMux) quadrature phase-shift keying (QPSK) system. In addition, the widest range of ±0.5 times the system symbol rate is achieved for the first time in an experimental 42.8-Gb/s coherent PolMux QPSK receiver.