N-LASF45HT by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.8714\,\lambda^2}{\lambda^2 - 0.0112172} + \frac{0.267778\,\lambda^2}{\lambda^2 - 0.0505135} + \frac{1.7303\,\lambda^2}{\lambda^2 - 147.107}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.78 \times 10^{-6} + 2(8.73 \times 10^{-9})\,\Delta T + 3(-2.65 \times 10^{-11})\,\Delta T^2 + \frac{8.24 \times 10^{-7} + 2(1.15 \times 10^{-9})\,\Delta T}{\lambda - 0.255}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$