A graded index fiber has a core diameter of 45 µm. Core has a parabolic reflective profile. The fiber has NA of 0.22 and operating at a wavelength of 1.2 µm. Estimate total number of guided mode propagating in the fiber.

Mumbai University > Electronics and Telecommunication > Sem7 > Optical Communication and Networks

Marks: 5M

Year: May 2012

Given :

Core diameter = 45 µm

Core radius (a) = 22.5 µm

NA = 0.22

λ = 1.2 µm

To find : Total number of guided modes $(M_g)$= ?

Solution : For graded index fiber,

$$M_g= \frac{V^2}4$$

$$V= \frac{2π}λaNA$$

$$V= \frac{2π}{1.2×10^{-6} }.22.5×10^{-6}.0.22$$

$$∴V=25.918$$

$$M_g= \frac{{25.918}^2}4$$

$$∴ M_g=167.93 ≈168$$

Ans: The number of guided modes $M_g$=168