P-LASF50 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.84911\,\lambda^2}{\lambda^2 - 0.00999235} + \frac{0.329829\,\lambda^2}{\lambda^2 - 0.0387438} + \frac{1.30401\,\lambda^2}{\lambda^2 - 95.8968}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[8.04 \times 10^{-6} + 2(1.2 \times 10^{-8})\,\Delta T + 3(-2.19 \times 10^{-11})\,\Delta T^2 + \frac{8.2 \times 10^{-7} + 2(9.08 \times 10^{-10})\,\Delta T}{\lambda - 0.209}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$