N-LASF46B by Schott

$$n(\lambda) = \sqrt{1 + \frac{2.17989\,\lambda^2}{\lambda^2 - 0.0125805} + \frac{0.306495\,\lambda^2}{\lambda^2 - 0.0567191} + \frac{1.56882\,\lambda^2}{\lambda^2 - 105.317}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[5.98 \times 10^{-6} + 2(1.3 \times 10^{-8})\,\Delta T + 3(-3.5 \times 10^{-12})\,\Delta T^2 + \frac{9.13 \times 10^{-7} + 2(1.24 \times 10^{-9})\,\Delta T}{\lambda - 0.267}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$