Step-index multimode fibers operate on the principle of total reflection and allow traveling of light across the fiber/core axis in a zigzag pattern. The fiber core is often quite large — for some large-core fibers not much smaller than the whole fiber (see Figure 1). At the same time, the numerical. In optical fibers, a step-index fiber is a fiber where a uniform refractive index exists within the core and a sharply decreased refractive index exists in the core-cladding interface because of the lower refractive index in cladding. These fibers are still widely use for LAN and enterprise applications. Step ind x MMF are characterized by significant number of modes propagating through fiber. Multi-mode links can be used for data rates up to 800 Gbit/s.
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