 if their initial requirement calls for the use of just a few. As requirements increase, the carrier will use additional fibers in the bundle. The term "dark fiber" is associated with unused fiber, while the term "lighted fiber" refers to fiber in use. In addition to the number of fibers within a cable, the bundled cable can vary according to the material used in its construction. Some individual and bundled cables are designed for general-pur- pose outdoor use, while other cable is designed for indoor use. In addition, you can obtain tactical cable designed for ruggedness required by the military forces as well as other types of specialized cable. Thus, there are literally hundreds of cables available for differ- ent applications. Now that we have a general understanding of the types of cable used, we will conclude this chapter by discussing another important cable- related topic: the fiber-optic connector. Chapter Three PVC Jacket Figure 3.14 Multiple-fiber cable. outer strength member Central Member cable with eight fibers This fiber bundle provides eight fiber cables, each with eight fibers, resulting in 64 fibers becoming available for use. Connectors A connector represents an important component of a fiber-optic trans- mission system. In addition to terminating cables, connectors are used to route an optical signal and represent an important component used for the cable reconfigurations required to satisfy changing organizational or customer requirements. The connector is a mechanical device physically connected to the end of a fiber-optic cable. This device is designed to mate with another device to provide attachment between cables, from a cable to a light source, or from a cable to a receiver. The attachment mechanism is referred to as the coupling method and warrants discussion. Because the coupling method is related to one or more connectors, we will examine both as a single entity. Coupling Method and Connectors Three basic types of coupling methods are used by connectors: threaded, bayonet, push-pull