A 4 km optical link consists of multimode step index fiber with core refractive index of 1.3 and a relative refractive index difference of 1%. Find the delay difference between the slowest and fastest modes at the fiber output.

Correct Answer: 0.173 μsec
The delay difference is given by δTs = Ln1/c Where δTs = delay difference n1 = core refractive index Δ = Relative refractive index difference c = velocity of light in vacuum.