What do 10GBase-SR and 10GBase-LR interfaces have in common?

10GBase-SR (Short Reach) and 10GBase-LR (Long Reach) are both standards for 10 Gigabit Ethernet, and the "Base" in their names signifies that they operate over baseband, meaning they use a single frequency for data transmission. The "R" indicates they use 64B/66B encoding. Crucially, both "SR" and "LR" variants are designed to operate exclusively over fiber optic cabling. 10GBase-SR uses multimode fiber for shorter distances, while 10GBase-LR uses single-mode fiber for longer distances. Therefore, while their fiber types differ, the fundamental requirement for fiber optic cabling is common to both. UTP cabling is used for copper-based Ethernet standards like 10GBase-T, not these fiber-based ones.