N-LASF41 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.86348\,\lambda^2}{\lambda^2 - 0.00910368} + \frac{0.413307\,\lambda^2}{\lambda^2 - 0.0339247} + \frac{1.35785\,\lambda^2}{\lambda^2 - 93.3581}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.03 \times 10^{-6} + 2(1.04 \times 10^{-8})\,\Delta T + 3(-1.3 \times 10^{-11})\,\Delta T^2 + \frac{6.62 \times 10^{-7} + 2(7.82 \times 10^{-10})\,\Delta T}{\lambda - 0.209}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$