Question

why step index fibers are more extensively used than the graded index fibers

Answer 1

Graded-Index Fiber, also known as G.651.1 under International Telecommunication Union (ITU) standards, is a type of fiber whose refractive index decreases gradually as the radial distance (distance to the core center) increases. In comparison, what we commonly have seen is G.652.D fiber which has a step-index refractive index profile. This article will compare graded-index multimode fiber with traditional step-index fiber, as well as its advantages when dealing with modal dispersion, a common signal distortion error.

The graph below shows the different refractive index profiles of the fiber core and cladding.