FCD100 by Hoya

$$n(\lambda) = \sqrt{2.04822 - 0.00432112\,\lambda^2 + 0.00618268\,\lambda^{-2} + 3.14115 \times 10^{-5}\,\lambda^{-4} + 3.53708 \times 10^{-6}\,\lambda^{-6} - 1.66945 \times 10^{-7}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-2.11 \times 10^{-5} + 2(-8.57 \times 10^{-9})\,\Delta T + 3(2.98 \times 10^{-11})\,\Delta T^2 + \frac{2.78 \times 10^{-7} + 2(2.18 \times 10^{-10})\,\Delta T}{\lambda - 0.201}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$