Systematic Analysis of Crosstalk Noise in Folded-Torus-Based Optical Networks-on-Chip

Photonic devices are widely used in optical networks-on-chip (ONoCs) and suffer from crosstalk noise. The accumulative crosstalk noise in large scale ONoCs diminishes the signal-to-noise ratio (SNR), causes severe performance degradation, and constrains the network scalability. For the first time, this paper systematically analyzes and models the worst-case crosstalk noise and SNR in folded-torus-based ONoCs. Formal analytical models for the worst-case crosstalk noise and SNR are presented. The crosstalk noise analysis is hierarchically performed at the basic photonic device level, then at the optical router level, and finally at the network level. We consider a general 5 × 5 optical router model to enable crosstalk noise and SNR analyses in folded-torus-based ONoCs using an arbitrary 5 × 5 optical router. Using the general optical router model, the worst-case SNR link candidates, which restrict the network scalability, are found. Also, we present a novel crosstalk noise and loss analysis platform, called CLAP, which can analyze the crosstalk noise and SNR of arbitrary ONoCs. Case studies of optimized crossbar and Crux optical routers using recent photonic device parameters are presented. Moreover, we compare the worst-case crosstalk noise and SNR in folded-torus-based and mesh-based ONoCs using optimized crossbar and Crux optical routers. The quantitative simulation results show the critical behavior of crosstalk noise in large scale ONoCs. For example, in folded-torus-based ONoCs using the Crux optical router, the noise power exceeds the signal power for network sizes larger than 12 × 12; when the network size is 20 × 20 and the injection signal power equals 0 dBm, the signal power and noise power are -9.4 dBm and -6.1 dBm, respectively.