Comparison of Passive Photonic Reservoir Computing Architectures for Signal Equalization of Future Generation Intra-DCN and Mobile Fronthaul Systems

In this paper, we compare the equalization performance of three different passive reservoir computing architectures using micro-ring resonators as reservoirs. The architectures consist of four resonators, arranged in a parallel $4 \times 1$, sequential $1 \times 4$ and deep $2 \times 2$ configuration. The reservoirs are simulated using the two-dimensional finite-difference time-domain method and are fed with simulation data from a comprehensive simulation setup with realistic component characteristics. We show, that the parallel architecture outperforms both the sequential and the deep micro-ring resonator configurations. Moreover, the parallel structure with a linear readout outperforms state-of-the-art digital signal processing in terms of bit error ratio by up to an order of magnitude. This passive reservoir computing architecture could pave the way to more energy-efficient and high symbol rate intra-DCN and mobile fronthaul systems.