A step-index fiber has core refractive index 1.46 and radius 4.5?m. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.

Question

Quizplus · Accepted Answer

The cutoff wavelength for single mode operation in a step-index fiber is given by the formula λc = 2πa(NA)/V, where NA is the numerical aperture and V is the normalized frequency. Given the core refractive index and relative index difference, we can calculate NA and then use the fiber radius to find the cutoff wavelength. The correct calculation leads to 1.214 μm.

A Step-Index Fiber Has Core Refractive Index 1