Optical Network Design and Implementation

Optical-Cable Construction

The core is the highly refractive central region of an optical fiber through which light is transmitted. The standard telecommunications core diameter in use with SMF is between 8 μm and 10 μm, whereas the standard core diameter in use with MMF is between 50 μm and 62.5 μm. Figure 3-4 shows the core diameter for SMF and MMF cable. The diameter of the cladding surrounding each of these cores is 125 μm. Core sizes of 85 μm and 100 μm were used in early applications, but are not typically used today. The core and cladding are manufactured together as a single solid component of glass with slightly different compositions and refractive indices. The third section of an optical fiber is the outer protective coating known ...