1. Step index fiber is of two types viz; mono mode fiber and
multi mode fiber.
Graded index fiber is of only of one type that is multi mode
fiber.
2. The refractive index of the core of the step index fiber is
constant through out the core.
The refractive index of the core of the graded index fiber is
maximum at the center of the core and then it decreases towards
core-cladding interface.
3. Number of modes for step index fiber N = V2/2, where V is cut
off frequency or normalized frequency or V- number
Number of modes for graded index fiber is N = V2/ 4.
4. V number can be less that 2.405 or more that 2.405 for step
index fiber
V number is always more than 2.405 for graded index fiber.
5. Step Index Fiber is a fiber in which the core is of a uniform
refractive index and there is a sharp decrease in the index of
refraction at the cladding.
Graded Index Fiber is a type of fiber where the refractive index
of the core is lower toward the outside of the fiber. It 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.
