Abstract
Propelled by the rise of artificial intelligence (AI), cloud services and data center applications, next-generation low-power, local-oscillator-less, and DSP-free short-reach coherent optical communication has evolved into an increasingly prominent area of research in recent years. Here, we demonstrate DSP-free coherent optical transmission by analog signal processing in frequency synchronous optical networks (FSON) architecture, which supports polarization multiplexing and higher-order modulation formats. The FSON architecture allows that the numerous laser sources of optical transceivers within a data center can be quasi-synchronized by means of a tree-distributed homology architecture. In conjunction with our proposed novel pilot-tone assisted Costas Loop for an analog coherent receiver, we achieve a record dual-polarization 224-Gb/s 16-QAM 5-km mismatch transmission with reset-free carrier phase recovery in the optical domain. Our proposed DSP-free analog coherent detection system based on the FSON makes it a promising solution for next-generation low-power, high-capacity coherent data center interconnects (DCI).