To achieve site-to-site replication using Fibre Channel over a distance of 10 kilometers, single-mode fiber optic cable is required. Single-mode fiber optic cables are designed for long-distance communication and can maintain a stable signal over distances much greater than 10 kilometers. Multimode fiber optic cables, on the other hand, are generally used for shorter distances. Flex fiber cables and polymer optical fiber cables are not suitable for this application.