S-BAM3 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.36955\,\lambda^2}{\lambda^2 - 0.00941331} + \frac{0.0853826\,\lambda^2}{\lambda^2 - 0.0504359} + \frac{1.1616\,\lambda^2}{\lambda^2 - 130.549}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.69 \times 10^{-6} + 2(1.28 \times 10^{-8})\,\Delta T + 3(-3.68 \times 10^{-11})\,\Delta T^2 + \frac{6.28 \times 10^{-7} + 2(7.06 \times 10^{-10})\,\Delta T}{\lambda - 0.238}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$