Single-mode 9/125um fiber cables are recommended for Fast, Gigabit, 10G Ethernet, SONET OC3-OC192. 40G and 100G Ethernet rate optical connections. Single-mode fiber is perfect for long-haul connections (hundreds of kilometers). Low prices make the 9/125um fiber attractive for in-building projects too, because of the reliability and choice of using a single-strand of fiber for same communications (simplex cords are used on Bi-Directional data links). Moreover, CWDM/DWDM technologies are easily implemented over single mode fiber circuits.