What type of fiber has a core with multiple layers of glass, each with a lower index of refraction?

The type of fiber that features a core with multiple layers of glass, each having a lower index of refraction, is the multi-mode graded-index fiber. In this design, the core is composed of a series of concentric layers, each with a gradually decreasing refractive index as one moves outward from the center. This gradation allows for improved light transmission and reduced modal dispersion compared to fibers with a uniform refractive index.

In multi-mode graded-index fibers, light rays that enter at shallow angles are bent more gradually than those entering at steeper angles, allowing multiple paths of light to travel through the fiber and effectively reducing the distortion of the signal over longer distances. This design is particularly advantageous in applications where high bandwidth and high data rates are needed, but over shorter distances typically found in local area networks or within buildings.

In contrast, single-mode graded-index fibers have a core that is designed to support only a single mode of light propagation and do not utilize multiple layers with varying indices of refraction. The multi-mode step-index fiber has a uniform core refractive index and a distinct transition to a lower refractive index in the cladding, leading to more significant modal dispersion. The hybrid multi-mode fiber may incorporate aspects of both multi-mode and single-mode