An optical fiber is a glass or plastic medium that transmits information using light. Fiber-optic cable has one or more optical fibers enclosed in a sheath or jacket, as shown in the figure. Because it uses light to transmit signals, fiber-optic cable is not affected by EMI or RFI. All signals are converted to light pulses as they enter the cable, and converted back into electrical signals when they leave it. This means that fiber-optic cable can deliver signals that are clearer, can go farther, and have greater bandwidth than cable made of copper or other metals.

Fiber-optic cables can reach distances of several miles or kilometers before the signal needs to be regenerated. Either lasers or light emitting diodes (LEDs) generate the light pulses that are used to represent the transmitted data as bits on the media. Bandwidth reaches speeds of 100 Gb/s and increases as standards are developed and adopted.

The speed of data transmitted over fiber-optic cable is limited by the devices connected to the cable, as well as impurities within the fiber cable. Electronic semiconductor devices called photodiodes detect the light pulses and convert them to voltages that can then be reconstructed into data frames.

Fiber-optic cable is usually more expensive to use than copper cable, and the connectors are more costly and harder to assemble. Common connectors for fiber-optic networks are:

These three types of fiber-optic connectors are simplex, which allows data to flow in only one direction. Therefore, two cables are needed to provide data flow in both directions.

These are the two types of glass fiber-optic cable: