The GLC-ZX-SM, 1000BASE-ZX SFP operates on ordinary single-mode fiber optic link spans of up to 70 kilometers (km) in length. Link spans of up to 100 km are possible using premium single-mode fiber or dispersion-shifted single-mode fiber. The SFP 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.