BAFN10 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.60477\,\lambda^2}{\lambda^2 - 0.00947022} + \frac{0.123762\,\lambda^2}{\lambda^2 - 0.045164} + \frac{1.07271\,\lambda^2}{\lambda^2 - 108.539}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[2.57 \times 10^{-6} + 2(9.79 \times 10^{-9})\,\Delta T + 3(-4.07 \times 10^{-11})\,\Delta T^2 + \frac{5.54 \times 10^{-7} + 2(6.69 \times 10^{-10})\,\Delta T}{\lambda - 0.248}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$