Quantifying the Impact of Frequency Comb Distillation on Comb-Based Optical Communications Systems

Microring resonators (MRR) can be used as a selective filter for amplified optical frequency combs, to reduce the impact of broadband noise. This approach, called comb distillation, could be useful when amplifying low-power microcombs. Comb distillation can substantially reduce the required comb line optical-carrier-to-noise ratio (OCNR) needed to support optical communications. However, the understanding of noise characteristics after comb distillation in a communications system has not been thoroughly established. In this paper, we find closed form solutions for noise after distillation, and directly link this to achievable system signal-to-noise ratio (SNR), providing a method to assess the expected system performance when the distilling MRR device resonance bandwidth and coupling loss are changed. This can be used to predict the distillation-enabled increase in the number of usable lines of microcombs for superchannel transmission, and/or the number of spatial modes for space-division-multiplexing (SDM) systems based on a distilled microcomb.