S-NBH53 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.65828\,\lambda^2}{\lambda^2 - 0.0113873} + \frac{0.263276\,\lambda^2}{\lambda^2 - 0.0522108} + \frac{2.10143\,\lambda^2}{\lambda^2 - 165.524}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.75 \times 10^{-6} + 2(9.12 \times 10^{-9})\,\Delta T + 3(-3.26 \times 10^{-11})\,\Delta T^2 + \frac{8.19 \times 10^{-7} + 2(1.05 \times 10^{-9})\,\Delta T}{\lambda - 0.264}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$