S-NBH8 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.61344\,\lambda^2}{\lambda^2 - 0.0106387} + \frac{0.257296\,\lambda^2}{\lambda^2 - 0.0487072} + \frac{1.98364\,\lambda^2}{\lambda^2 - 159.784}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.76 \times 10^{-7} + 2(9.72 \times 10^{-9})\,\Delta T + 3(-3.07 \times 10^{-11})\,\Delta T^2 + \frac{8.22 \times 10^{-7} + 2(9.16 \times 10^{-10})\,\Delta T}{\lambda - 0.251}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$