The optical transmission characteristics of G. 652 fibers are defined to ensure low-loss signal propagation primarily at 1310 nm and 1550 nm wavelengths, with attenuation coefficients not exceeding 0. It details the fiber's geometrical, optical. There are three wavelength windows for 10G optical module communication applications, namely the 850nm window, 1310nm window, and 1550nm window. Each corresponds to specific fiber types, reach classes, and application environments such as short-reach data center links, campus backbones, metropolitan aggregation, or long-haul transmission. dispersion wavelength around 1310 nm. D is the International Telecommunication Union's (ITU‑T) standard for single‑mode fiber (SMF) — the type used for long‑distance and high‑capacity optical communication.