D-ZPK1A by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.723325\,\lambda^2}{\lambda^2 - 0.00288946} + \frac{0.863552\,\lambda^2}{\lambda^2 - 0.0142439} + \frac{0.985077\,\lambda^2}{\lambda^2 - 116.597}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.27 \times 10^{-5} + 2(7.36 \times 10^{-9})\,\Delta T + 3(-1.75 \times 10^{-13})\,\Delta T^2 + \frac{4.58 \times 10^{-7} + 2(2.54 \times 10^{-10})\,\Delta T}{\lambda - 0.183}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$