Handling rack vibrations in FSO-based data center architectures

To overcome the shortcomings of traditional static (wired) data center (DC) architectures, there have been recent proposals of fully-wireless and reconfigurable architectures, e.g., FireFly, ProjecTor, based on Free-Space Optical (FSO) wireless links. However, there are significant challenges that need to be addressed to make the vision of FSO-based DC architectures a compelling reality. While some of these scientific challenges have been addressed in recent works, one key challenge that has yet to be addressed is how to handle FSO link misalignments due to DC rack vibrations (where the FSO transceivers are placed). The focus of this paper is to comprehensively address this challenge. Particularly, in this work, we present measurement results of a thorough study conducted over a live DC to characterize rack vibrations, and design a novel tracking and pointing (TP) system that is based on received power feedback and has a zero exposed-footprint on the deployment platform (racks). We develop and test a reconfigurable FSO link with our designed TP system and evaluate it over expected rack vibrations; our evaluation results demonstrate the effectiveness of our TP system.