The paper describes an optical interferometer realized at INRiM, which works as pressure standard based on a well-known phenomenon of light-matter interaction: the dependence of refractive index with pressure (density) of a gas. The realization of a pressure standard via optical method requires a combined approach of high accurate refractive index measurements (sub-nanometer and sub-millikelvin metrology) with ab-initio quantum calculation of molar refractivity, paving the way for a quantum-based standard. The paper reports recent development concerning a new layout of the system, currently focused to improve the temperature measurement and stability. The developed system is a preliminary achievement towards a quantum-based pressure standard in the range between 100 Pa and 150 kPa.