S-BAL11 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{0.821314\,\lambda^2}{\lambda^2 - 0.00351436} + \frac{0.612586\,\lambda^2}{\lambda^2 - 0.0179762} + \frac{1.2486\,\lambda^2}{\lambda^2 - 133.457}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.44 \times 10^{-6} + 2(1.26 \times 10^{-8})\,\Delta T + 3(-4.45 \times 10^{-11})\,\Delta T^2 + \frac{5.04 \times 10^{-7} + 2(6.25 \times 10^{-10})\,\Delta T}{\lambda - 0.192}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$