High accurate and modulation transparent frequency offset compensation scheme using data-aided feedback structure in coherent optical communication systems

The high-order modulation format has the advantages of high spectral efficiency and large system capacity. However, the traditional frequency offset estimation and compensation algorithms, such as fast Fourier transform-based frequency offset estimation (FFT-FOE) that relies on a large number of complex FFT operations and differential frequency offset estimation (Diff-FOE) that relies on finite phase difference between adjacent symbols, are difficult to meet the frequency offset estimation requirements for any high-order modulation format. In this work, a novel FOE scheme using QPSK training symbols aided feedback structure is proposed. The performance of the proposed FOE scheme is evaluated in a polarization multiplexing QPSK-aided 32/64-quadrature amplitude modulation (QAM) simulation platforms with a symbol rate of 28 GBaud. The results show that has the technical advantages of low complexity, suitable for arbitrarily high-order modulation, tolerance for laser phase noise and wide tracking frequency offset range.