The ATLAS Forward Proton physics program at CERN aims at studying soft and hard diffractive events from ATLAS proton collisions. Time-of-Flight (ToF) system is used to reduce the background from multiple proton-proton collisions. In this presentation, we describe technical details of the Fast Cherenkov model of photons generation and transportation through the optical part of the ToF detector. This Fast simulation uses Python programming language and Numba (high performance compiler). It is about 200 times faster than Geant4 simulation already implemented, and provides similar results concerning length and time distributions of photons. Moreover, this Fast simulation allows computing easily the time resolution of the different bars of ToF detector.