ssociated with the cabling plant can be expected to provide service for the projected future. Plastic Optical Fiber (POF) technology is making fiber even more affordable and easier to install. Because the core is plastic instead of glass, terminating the cable is easier. The trade-off for this lower cost and ease of installation is shorter distance capabilities and bandwidth limitations. 2.0 Fiber Construction Fiber optic cabling has the following components (starting in the center and working out): core, cladding, coating, strength member, and jacket. The design and function of each of these will be defined. The core is in the very center of the cable and is the medium of propagation for the signal. The core is made of silica glass or plastic (in the case of POF) with a high refractive index. The actual core is very small (compared to the wire gauges we are used to). Typical core sizes range from 8 microns (millionth of a meter) for single mode silica glass cores up to 1000 microns for multi mode POF. The cladding is a material of lower index of refraction which surrounds the core. This difference in index forms a mirror at the boundary of the core and cladding. Because of the lower index, it reflects the light back into the center of the core, forming an optical wave guide. This is the same effect as looking out over a calm lake and noting the reflection, while looking straight down you see through the water. It is this interaction of core and cladding that is at the heart of how optical fiber works. The coating (also referred to as buffer or buffer coating) is a protective layer around the outside of the cladding. It is typically made of a thermoplastic material for tight buffer construction and a gel material for loose buffer construction. As the name implies, in tight buffer construction, the buffer is extruded directly onto the fiber, tightly surrounding it. Loose buffer construction uses a gel filled tube which is l...
