While the yellow sheath of SMF signifies single-mode transmission for long-distance applications, the orange sheath of MMF represents multi-mode transmission for shorter distances. It is commonly used in long-haul. The core: made of silica, molten quartz, or plastic, in which optical waves propagate. 5µm for multimode fiber and 9µm for single-mode. Sheathing typcially has a larger bend radius, which protects the fibers from breaking. The outer sheath of single mode fiber optic patch cord is usually yellow, with small fiber core diameter and dispersion, allowing only one. The design of fiber optic cable jackets is influenced by the mode of fiber they protect: single-mode or multi-mode. ② transmission distance:.