N-LASF46A by Schott

$$n(\lambda) = \sqrt{1 + \frac{2.16702\,\lambda^2}{\lambda^2 - 0.0123596} + \frac{0.319813\,\lambda^2}{\lambda^2 - 0.056061} + \frac{1.66004\,\lambda^2}{\lambda^2 - 107.048}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.53 \times 10^{-6} + 2(1.24 \times 10^{-8})\,\Delta T + 3(-1.87 \times 10^{-11})\,\Delta T^2 + \frac{8.39 \times 10^{-7} + 2(1.04 \times 10^{-9})\,\Delta T}{\lambda - 0.275}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$