To date, most applications in security systems have used fiber optics as the transmission medium for data, control, and video. The decision to use fiber optics rests on a combination of economic, environmental, and physical limitations of the facility. In CCTV systems, fiber-optic cable provides for low loss, wide bandwidth transmission of video signals without the use of amplifiers and over longer distances than coaxial cable. It also eliminates hum bars and powerline phase problems. Fiber-optic cable systems also are being used as intrusion detection devices to increase perimeter security. A typical system consists of a transmitter, a receiver, cable, and connectors. In choosing a system, the engineer must decide on the following design elements: fiber versus metal cable; simplex, half-duplex, or full-duplex configuration; form of modulation; multiplexing strategy; wavelength of operation; choice of light source (laser or light-emitting diode); specification of fiber and cable; choice of connectors and splicing techniques; choice of detectors; and system configuration and final design. As technology improves and cost declines, the most significant disadvantage of fiber-optic systems will be interfacing them with existing nonfiber optic systems. 3 figures.