S-FSL5Y by Ohara

$$n(\lambda) = \sqrt{1 + \frac{0.97741\,\lambda^2}{\lambda^2 - 0.00557649} + \frac{0.210951\,\lambda^2}{\lambda^2 - 0.0177} + \frac{1.37143\,\lambda^2}{\lambda^2 - 149.211}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-6.38 \times 10^{-6} + 2(1.6 \times 10^{-8})\,\Delta T + 3(-3.75 \times 10^{-11})\,\Delta T^2 + \frac{3.18 \times 10^{-7} + 2(4.69 \times 10^{-10})\,\Delta T}{\lambda - 0.19}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$