100BASE-FX uses multi-mode fiber optic cable and is designed for medium-distance data transmission suitable for lengths of up to 2 kilometers, which falls within the requirement of 1.5 kilometers. This standard supports data rates of up to 100 Mbps, fulfilling the client’s speed requirement. Using a fiber optic solution is essential for this distance as copper cables like Cat 5e and Cat 6 would suffer from signal degradation and are not rated for such distances. 1000BASE-T, on the other hand, is intended for copper and supports gigabit speeds but is limited to 100 meters, making it unsuitable for this scenario.