S-NBH51 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.71204\,\lambda^2}{\lambda^2 - 0.0107724} + \frac{0.25599\,\lambda^2}{\lambda^2 - 0.0488594} + \frac{1.81457\,\lambda^2}{\lambda^2 - 136.359}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.65 \times 10^{-6} + 2(8.19 \times 10^{-9})\,\Delta T + 3(-2.95 \times 10^{-11})\,\Delta T^2 + \frac{7.55 \times 10^{-7} + 2(1.01 \times 10^{-9})\,\Delta T}{\lambda - 0.261}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$