A graded-index fiber has a core with parabolic refractive index profile of diameter of 30?m, NA=0.2, ?=1?m. Estimate the normalised frequency.

Question

Quizplus · Accepted Answer

The normalized frequency V of an optical fiber, also known as the V-number or V-parameter, can be calculated using the formula $V = \frac{2\pi a}{\lambda}NA$, where $a$ is the core radius, $\lambda$ is the wavelength of light in vacuum, and NA is the numerical aperture of the fiber. Given that the diameter of the core is 30μm, the radius $a$ is half of that, which is 15μm or 15x10^-6 m. The numerical aperture NA is given as 0.2, and the wavelength $\lambda$ is 1μm or 1x10^-6 m. Substituting these values into the formula gives $V = \frac{2\pi (15x10^{-6})}{1x10^{-6}}(0.2) = 18.84$.

A Graded-Index Fiber Has a Core with Parabolic Refractive Index