Area Lighting Systems

Figure 6-11.—Expanded-beam connector operation. can combine the optical signal from two or more fibers into a single fiber. Fiber-optic couplers can be either active or passive devices. The difference between active and passive couplers is that a passive coupler redistributes the optical signal without optical-to-electrical conversion. Active couplers are electronic devices that split or combine the signal electrically and use fiber-optic detectors and sources for input and output. Figure 6-12 shows the design of a basic fiber-optic coupler. A basic fiber-optic coupler has N input ports and M output ports. N and M ports typically range from 1 to 64. The number of input ports and output ports varies, depending on the intended application for the coupler. Types of fiber-optic couplers include optical splitters, optical combiners, X couplers, star couplers, and tree couplers. AREA LIGHTING SYSTEMS This section covers streetlighting, floodlighting, and security lighting systems. When properly constructed and installed, these original basewide lighting systems will provide years of trouble-free operation with a minimum of minor maintenance and bulb changing required to keep the system fully operational. Several factors can change the base requirements for area lighting. These factors include such changes as facility usage, updating of systems, changes in the base mission, or expanding existing systems. With the cost of energy rising daily, any system that can provide a higher level of efficiency for the energy used must be considered. The use of the newer high- pressure discharge systems for lighting seems to offer savings both in the lifespan of the bulbs and in the lumens per watt of energy used These systems are replacing the older incandescent systems in an ever- increasing pace. The higher initial cost of these systems is being offset by the efficiency of the energy used and savings of energy dollars. TERMINOLOGY AND DEFINITIONS You will need an understanding of lighting techniques and effects to understand the physical concepts and terminology involved in lighting systems. We will use both the American Standard (AS) and the metric system (SI) when discussing lighting concepts. The AS standards will be without brackets, whereas the SI terms will be noted in square brackets [ ]. The candlepower [candela], abbreviated cp [cd], is the unit of luminous intensity. It is comparable to the voltage in an electrical circuit and represents the force that generates the light you can see. An ordinary wax candle has a luminous intensity of approximately one Figure 6-12.—Basic passive fiber-optic coupler design. 6-11