S-NSL5 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.04575\,\lambda^2}{\lambda^2 - 0.00585232} + \frac{0.239613\,\lambda^2}{\lambda^2 - 0.0236859} + \frac{1.15907\,\lambda^2}{\lambda^2 - 131.329}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.14 \times 10^{-6} + 2(1.21 \times 10^{-8})\,\Delta T + 3(-4.3 \times 10^{-11})\,\Delta T^2 + \frac{3.41 \times 10^{-7} + 2(5.9 \times 10^{-10})\,\Delta T}{\lambda - 0.272}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$