A type of multimode fiber which used a graded profile of refractive index in the core material to correct for dispersion. An optical fiber with a core having a refractive index that decreases with increasing radial distance from the fiber axis. The most common refractive index profile for a graded index fiber is very nearly parabolic. The parabolic profile results in continual refocusing of the rays in the core, and compensates for multimode distortion. Has greater bandwidth than step index fibre, but less bandwidth than single mode fiber.