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 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 used, 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. Plugging these values into the formula gives:$$V = \frac{2\pi (15x10^{-6})}{1x10^{-6}}(0.2) = 2\pi(15)(0.2) = 6\pi(3) \approx 18.84$$Therefore, the normalized frequency V is approximately 18.84.

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