Fiber coupling can be accomplished by fusion splicing. Fusion splicing creates permanent fiber coupling with low insertion loss, high strength and smaller size. However, for temporary connections optical connectors are used to produce quick connections and disconnections. Fibers are used instead of metal wires because signals travel along them with less loss and are immune to electromagnetic interference. They support high-speed, interference-resistant communication and are particularly effective in applications that require high bandwidth, low latency, and strong signal integrity. They have a central core surrounded by a concentric cladding with slightly lower (by ≈ 1%) refractive index.