The optical fiber preform is manufactured through a two-step process of VAD (Vapor Axial Deposition) core rod and OVD (Outside Vapor Deposition) cladding. The main component of the preform is SiO₂ but mixed with F and Ge in specific areas. The preform with diameter 130-150mm is used for drawing SMF(single-mode optical fiber) that meet the standards of ITU-T G.652.B/D and ITU-T G.657.A1/A2/B3, etc.