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

A step-index fiber has core refractive index 1.46 and radius 4.5μm.

1.	A step-index fiber has core refractive index 1.46 and radius 4.5μm. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.
A.	1.326μm
B.	0.124μm
C.	1.214μm
D.	0.123μm
Answer» D. 0.123μm