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√(2Δ))/V, where a is the core radius, Δ is the relative index difference, and V is the normalized frequency (V-number). For single-mode operation, V should be less than 2.405. Using the given values, the calculation shows that the cutoff wavelength is approximately 1.214 μm.

A Step-Index Fiber Has Core Refractive Index 1