652 is the standard single-mode fiber used in access and metro networks, optimized for 1310 nm transmission with normal dispersion at 1550 nm, while G. Each fiber type is engineered with different refractive index profiles, dispersion properties, and bending performance to support specific applications—from long-distance. This article will focus on the simpler ITU-T G. 65x series is a commonly known single mode fiber standard category, which can be further divided into G. 655 are the two options commonly used. 653 (dispersion-shifted fiber), G.