Solution:

λ = 850 nm

σ = 45 nm

pulse broadening due to material dispersion is given by,

$\sigma_m=\sigma L M$

$\text { Material dispersion constant } D_{\text {mat }}=\frac{-\lambda}{c} \cdot \frac{d^2 n}{d \lambda^2}$

For LED sources operating at 850 nm,

$\left|\lambda^2 \frac{d^2 n}{d \lambda^2}\right|=0.025$

$ …