Timing Recovery for 400G P2MP Optical Networks Using Coherent Digital Subcarrier Multiplexing

Point-to-multi-point (P2MP) optical networks using coherent digital subcarrier multiplexing (DSCM) can offer a better match to the hub-and-spoke traffic pattern. To reduce the computational complexity of the digital signal processing at the leaf nodes, the hub-site chromatic dispersion (CD) pre-compensation can be adopted but the residual CD will affect the timing recovery (TR). In this paper, we present a CD-tolerant TR algorithm for 400Gb/s P2MP optical networks using coherent DSCM over 320 km transmission. The experimental results of the 400Gb/s P2MP optical networks show that the proposed leaf-node TR can tolerate a residual CD up to ~5600 ps/nm after hub-site CD pre-compensation. The timing phase can be maintained accurately by the proposed CD-tolerant TR algorithm under the timing errors of phase offset, frequency offset, and jitter. Moreover, TR for P2MP optical networks using coherent DSCM with lower baud rate subcarrier has more robustness against CD.