er in the form of on and off light pulses, somewhat similar, in theory, at least, to the operation of signaling lamps that were commonly used in the Navy to transmit Morse code messages. Although fiber-optic cabling has many advantages for high-traffic areas, the speci- fications for fiber connections are more exacting, and the fiber itself requires more care in handling and installation. For example, it is less flexible than copper and cannot be bent around tight corners. However, given its greater capacity and cost savings in ongoing maintenance, carriers install fiber in the majority of new apartment buildings and office complexes. There are two reasons why fiber is typically more expensive than copper to install. The electronics (multiplexers and lasers) to convert electrical signals to opti- cal signals, and vice versa, are costly. Specialized technicians, paid at higher levels, are required to work with and test fiber cabling. In addition, the multiplexers and interfaces to copper cabling in the customer's facility requires local power. This adds a point of vulnerability in the event of a power outage. Fiber-optic cable is made of ultra-pure strands of glass. The narrower the core that carries the signals, the faster and farther a light signal can travel without errors or the need for repeaters. The cladding surrounding the core keeps the light contained to prevent the light signal from dispersing; that is, spreading over time, with wavelengths reaching their destination at different times. Finally, there is a coating that protects the fiber from environmental hazards such as rain, dust, scratches, and snow. Another benefit of fiber-optic cabling is that eavesdropping is more difficult because the strands have to be physically broken and listening devices spliced into the break. A splice is a connection between cables. Splices in fiber-optic cables are easily detected. Network Cabling Single-Mode versus Multi-Mode Fiber There are two main types of fiber: single-mode and multi-mode. Single-mode fiber is smal