LF5G19 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.34611\,\lambda^2}{\lambda^2 - 0.00971744} + \frac{0.142428\,\lambda^2}{\lambda^2 - 0.0501912} + \frac{0.900477\,\lambda^2}{\lambda^2 - 111.96}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-8.15 \times 10^{-6} + 2(1.34 \times 10^{-8})\,\Delta T + 3(-9.22 \times 10^{-12})\,\Delta T^2 + \frac{8.57 \times 10^{-7} + 2(8.26 \times 10^{-10})\,\Delta T}{\lambda - 0.243}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$