Graded index fiber
Graded index fiber is another type of optical fiber in which the core of the fiber is modified in such a way that the refractive index at the high value at the core of the fiber and falls off with the radial distance from the axis. The refractive index decreases with distance from the core axis, so the light ray bent by refraction and curved inward towards the axis. The ray undergoes total internal reflection at a specific layer, so the rays launched at different angles have different curvature. The graded-index fiber is used for multi-mode transmission.
Difference between step-index fiber and graded-index fiber
In step-index fiber, the refractive index of the core is uniform throughout after fiber and undergoes an abrupt change at the core-cladding boundary. In graded-index fiber, the refractive index of the core is made to vary gradually in such a way that the refractive index is maximum at the core. In step-index fiber, the path of light is in a zig-zag manner, whereas in graded-index fiber, the path of light propagation in a helical manner. Step-index fiber has lower bandwidth where are graded-index fiber has higher bandwidth.