Low Complexity Carrier Recovery System Design for Baudrate Sampled Coherent Datacenter Interconnects

Abstract

A novel low complexity carrier recovery system for baudrate sampled coherent datacenter links is presented. By separating the phase contributions from residual frequency offset and laser phase noise, this system reduces the required number of complex multiplications for frequency recovery by 50% and for phase recovery by 81.2%. The design incorporates a multi-stage serialized blind phase search to estimate the average phase within a processing block, while another parallel branch estimates the total phase drift across a digital signal processing (DSP) block. This feed-forward structure enables highly parallelized DSP implementation while maintaining robustness against large carrier frequency offsets and cycle slips. The method is validated through both simulation and measurements for QPSK and 16QAM, demonstrating large power savings and improved tolerance for frequency offset compared to state-of-the-art techniques.