Detector simulation in the O\textasciicircum 2 upgrade to the ALICE experiment

The ALICE experiment at the LHC is currently undergoing upgrades to prepare for Run 3 in 2020. One aspect of these upgrades is the ``Online - Offline computing system'' (O\textasciicircum 2), which is an upgrade to the computing facilities of ALICE as well as the underlying software to accommodate the high data rates and volumes. Part of the software upgrade involves creating models of the detector components, so that the collision events can be simulated. These simulations will help validate the detector's performance. This talk will present an overview of O\textasciicircum 2 as well as the modeling of the ALICE Fast Interaction Detector (FIT) in software.