D-ZK79-25 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.754687\,\lambda^2}{\lambda^2 - 0.00315353} + \frac{0.788729\,\lambda^2}{\lambda^2 - 0.0162518} + \frac{1.10214\,\lambda^2}{\lambda^2 - 112.786}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[6.7 \times 10^{-7} + 2(1.89 \times 10^{-8})\,\Delta T + 3(-2.68 \times 10^{-10})\,\Delta T^2 + \frac{2.21 \times 10^{-7} + 2(1.09 \times 10^{-9})\,\Delta T}{\lambda - 0.312}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$