N-KZFS11 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.33222\,\lambda^2}{\lambda^2 - 0.00840298} + \frac{0.289242\,\lambda^2}{\lambda^2 - 0.034424} + \frac{1.15162\,\lambda^2}{\lambda^2 - 88.4311}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.34 \times 10^{-6} + 2(1.16 \times 10^{-8})\,\Delta T + 3(-1.8 \times 10^{-11})\,\Delta T^2 + \frac{6.32 \times 10^{-7} + 2(7.21 \times 10^{-10})\,\Delta T}{\lambda - 0.206}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$