Design of training sequence based on IQ imbalance estimation in CO-OFDM system

Abstract:

In this paper, a new training sequence structure is proposed, which estimates the in-phase/quadrature (IQ) imbalance factor and channel information in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems with phase noise caused by laser linewidth. The given training sequence structure consists of four symbols. The first two training symbols have two subsets:a non-zero subset and a zero set mirror position subset. The non-zero subset is used to estimate the channel information, the mirror position subset is used to estimate the IQ imbalance factor, and the last two symbols are also used to estimate the IQ imbalance factor at the transmitter. This method can realize independent compensation for IQ imbalance and channel distortion, and improve the system performance when the data rate is 10 Gbit/s higher than the traditional method.