QF70GFI by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.15952\,\lambda^2}{\lambda^2 - 0.03736} + \frac{1.18949\,\lambda^2}{\lambda^2 - 0.00785047} + \frac{0.983674\,\lambda^2}{\lambda^2 - 119.949}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.36 \times 10^{-6} + 2(1.67 \times 10^{-8})\,\Delta T + 3(-3.12 \times 10^{-11})\,\Delta T^2 + \frac{6.68 \times 10^{-7} + 2(3.97 \times 10^{-10})\,\Delta T}{\lambda - 0.216}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$