Distributed acoustic sensing (DAS) is one of the latest and prominent measuring instruments based on the development of laser technology. DAS has a wide range of application domains, from geophysics to biology and natural sciences. DAS has gained increasing interest in geophysics during the last decade and the research on it is continuously growing. It has been successfully applied in Vertical Seismic Profile (VSP) for both reservoir and CO2 monitoring. Amplitude-Versus-Offset (AVO) analysis on DAS data may also be beneficial to CO 2 monitoring. Another opportunity is the application of FWI on DAS data. Either for FWI or CO2 monitoring with AVO analysis, the precision of DAS data, in terms of both phase and amplitude, should meet a high standard. DAS is actively researched in project-team Makutu Inria and TotalEnergies for the purpose of seismic imaging and CO2 geological storage monitoring. In the ongoing research, we compare three DAS formulae analytically and numerically. On one hand, this comparison is necessary to validate our numerical tools for DAS simulation; on the other hand, a quantitative study on the precision of DAS simulation will help us ensure a good DAS data quality during a FWI workflow.