TYPES of Optical Fiber Part2:-

(b) Graded Index:-

b1)Graded Index Multi-mode Fiber:-

• It exhibits non-uniform refractive index to reduce inter-model dispersion. through transit time equalization.
• The refractive index profile is non- uniform i.e maximum at core axis and reduce towards the radical distance to the cladding. Hence, the mode travelling near the core axis will be slow as compared the mode travelling near the cladding. Hence, the transit time of fastest mode i.e mode near the core the core will increase and the transit time of slowest mode i.e mode travelling Zig-Zag with will decrease , Hence, ∂T=Tmax-Tmin will reduced and this is known as Transit time equalization. Hence, the inter modal dispersion will reduce.

Note:- Step index multi mode fibers the modes travel through reflection where as in graded index multi-mode fiber the modes travel through refraction.

Number of modes,

M= (α/α+2)(v²/2) α =2; Parabolic ; M= v² /4 α =1; Triangular; M= v² /6 α =Index Profile Parameter