QF50GTI by CDGM

$$n(\lambda) = \sqrt{1 + \frac{1.31146\,\lambda^2}{\lambda^2 - 0.00988577} + \frac{0.840047\,\lambda^2}{\lambda^2 - 102.88} + \frac{0.132407\,\lambda^2}{\lambda^2 - 0.0477528}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.74 \times 10^{-6} + 2(1.64 \times 10^{-8})\,\Delta T + 3(-5.12 \times 10^{-11})\,\Delta T^2 + \frac{8.26 \times 10^{-7} + 2(4.87 \times 10^{-10})\,\Delta T}{\lambda - 0.234}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$