Fiber-optic cable consists of a silicon glass core that conducts light, rather than electricity, as in coaxial cables and twisted pair wiring. The core is surrounded by cladding and then a plastic jacket. Fiber-optic cables have the highest data-carrying capacity of any wired medium. The data rate for years has been much higher than the speed at which standard electronics could load the fiber. This mismatch between fiber and nodal electronics speed has been called the “electronic bottleneck.” Decades ago the situation was reversed, links were slow, and nodes were relatively fast. This paradigm shift has led to a redesign of protocols. Two major types of fiber exist: multi-mode and single mode. Pulse shapes are more accurately preserved in single-mode fiber, lending to a higher potential data rate.