This paper investigates the performance of a two-tier AWGR-based Passive Optical Network (PON) data centre architecture against an AWGR-based PON data centre architecture by considering various scenarios involving link failures to evaluate the resilience of both designs. To optimize traffic routing under different failure scenarios, a Mixed Integer Linear Programming (MILP) model is developed and the power consumption and delay performance is assessed. The results demonstrate that the two-tier AWGR architecture reduced the power consumption and the delay compared to the AWGR-based architecture by up to 10% and 61%, respectively.
