S-NBH57 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.92026\,\lambda^2}{\lambda^2 - 0.0118468} + \frac{0.371535\,\lambda^2}{\lambda^2 - 0.0532105} + \frac{2.55206\,\lambda^2}{\lambda^2 - 204.549}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.2 \times 10^{-6} + 2(8.85 \times 10^{-9})\,\Delta T + 3(-1.11 \times 10^{-11})\,\Delta T^2 + \frac{8.68 \times 10^{-7} + 2(1.05 \times 10^{-9})\,\Delta T}{\lambda - 0.282}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$