N-LASF46 by Schott

$$n(\lambda) = \sqrt{1 + \frac{2.18074\,\lambda^2}{\lambda^2 - 0.0125642} + \frac{0.298979\,\lambda^2}{\lambda^2 - 0.05647} + \frac{1.6219\,\lambda^2}{\lambda^2 - 105.663}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.6 \times 10^{-6} + 2(1.2 \times 10^{-8})\,\Delta T + 3(-2.68 \times 10^{-11})\,\Delta T^2 + \frac{8.42 \times 10^{-7} + 2(1.15 \times 10^{-9})\,\Delta T}{\lambda - 0.272}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$