Joint Pre-Equalization and Digital Resolution Enhancer in Bandwidth-Limited and Low-Resolution Optical Transmission Systems

With the exponentially increasing demand on data traffic, transmission capacity of the optical communications grows continuously. The increase of transmission capacity inevitably encounters bandwidth limitation impairments due to the insufficient bandwidth of the devices. Pre-equalization is commonly used to compensate the bandwidth limitation impairments, but the increased peak-to-average power ratio caused by pre-equalization has more stringent demand on the resolution of digital-to-analog converter (DAC). In this paper, a joint pre-equalization and digital resolution enhancer (DRE) algorithm is proposed in a bandwidth-limited and low-resolution optical transmission system. For 100-Gbaud dual-polarization 16QAM transmission, the joint pre-equalization and DRE algorithm allows the DAC with 40-GHz 3-dB bandwidth and 4-bits physical number of bits. Simulation results reveal that after jointly optimizing the pre-equalization and DRE, approximately 2-dB optical signal-to-noise ratio improvement is obtained at the 7% forward error correction limit. The effective range of pre-equalization strength in joint pre-equalization and DRE can achieve more than four times of that in pre-equalization only, which shows the proposed algorithm has the superiority in robustness.