Vapor phase deposition is a technique used to prepare pure optical glasses. It involves vaporizing inorganic compounds and dopants and depositing them as thin films on a substrate through chemical reactions, forming a porous soot preform. The preform is then consolidated through heating to become a solid glass cylinder that can be drawn into an optical fiber. Common vapor deposition methods include outside vapor phase oxidation, vapor axial deposition, modified chemical vapor deposition, and plasma-activated chemical vapor deposition. These processes allow producing silica-based fibers with very low light attenuation and optimal optical properties.