This Cisco 1000BASE-ZX GBIC operates on ordinary single-mode fiber optic link spans up to 43.4 miles (70 km) long. Link spans of up to 62 miles (100 km) are possible using premium single-mode fiber or dispersion shifted single-mode fiber. The GBIC provides an optical link budget of 23 dB - the precise link span length will depend on multiple factors such as fiber quality, number of splices, and connectors.