Multimode Graded Index Fiber

• Graded Index Fiber is a type of fiber where the refractive index of the core is lower toward the outside of the fiber.
• The core in a graded-index fiber has an index of refraction that radially decreases continuously from the center to the cladding interface.
• As a result, the light travels faster at the edge of the core than in the center as shown in Figure. Different modes travel in curved paths with nearly equal travel times.
• This greatly reduces modal dispersion in the fiber.

Grade-index-multimode-fiber

• Graded-index fibers bends the rays inward and also allows them to travel faster in the lower index of refraction region. This type of fiber provides high bandwidth capabilities.
• As a result, graded-index fibers have bandwidths which are significantly greater than step-index fibers, but still much lower than single-mode fibers.
• Typical core diameters of graded-index fibers are 50, 62.5 and 100 µm.
• The main application for graded-index fibers is in medium-range communications, such as local area networks.