Low-Complexity Nonlinear Tomlinson-Harashima Precoding Based on Absolute-Term for ZR Inter-DCI

Due to the sensitivity to cost and power consumption, the intensity modulation direct detection (IM/DD) transmission system attracts significant interest in inter-data center interconnections. In medium reach IM/DD transmission systems, chromatic dispersion caused power fading effect appears to be a major performance limiting problem for double sideband (DSB) signal. Tomlinson-Harashima Precoding (THP) is an effective method for compensating for the dispersion at the transmitter side. By incorporating nonlinear kernels into the transfer function, the nonlinear THP can compensate both the dispersion and the nonlinear distortion of the signal and improve the performance of the system. However, the added nonlinear kernels will significantly increase the complexity. To reduce the complexity of nonlinear THP, we propose a low-complexity absolute-term kernel based nonlinear THP scheme. Compared with the conventional Volterra kernel based THP scheme, the proposed methods can reduce the number of multipliers by 50%-60% without performance degradation. We successfully demonstrate a 70-km 40-Gbaud and a 90-km 30-Gbaud DSB PAM-4 C-band IM/DD transmission over dispersion-uncompensated links.