LITHOTEC-CAF2 by Schott

$$n(\lambda) = \sqrt{1 + \frac{0.617617\,\lambda^2}{\lambda^2 - 0.00275382} + \frac{0.421118\,\lambda^2}{\lambda^2 - 0.0105901} + \frac{3.79711\,\lambda^2}{\lambda^2 - 1182.67}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-3.18 \times 10^{-5} + 2(-2.31 \times 10^{-8})\,\Delta T + 3(4.13 \times 10^{-11})\,\Delta T^2 + \frac{3.35 \times 10^{-7} + 2(1.91 \times 10^{-10})\,\Delta T}{\lambda - 0.192}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$