S-LAL7Q by Ohara

$$n(\lambda) = \sqrt{1 + \frac{0.905277\,\lambda^2}{\lambda^2 - 0.0155607} + \frac{0.777956\,\lambda^2}{\lambda^2 - 0.00284719} + \frac{1.18137\,\lambda^2}{\lambda^2 - 88.0738}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.2 \times 10^{-6} + 2(1.23 \times 10^{-8})\,\Delta T + 3(-8.73 \times 10^{-12})\,\Delta T^2 + \frac{4.14 \times 10^{-7} + 2(3.98 \times 10^{-10})\,\Delta T}{\lambda - 0.198}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$