Optical properties of Sn-doped {\text{In}}_{\text{2}}{\text{O 3}}_{} (ITO) have been studied in the optical range of 0.4–12\mu \text{m} . A deposition has been made on BK7 glass, magnesium fluoride, sapphire, and zinc sulfide substrates. The layers have been characterized by their optical properties, DC electrical sheet resistivity, and Hall mobility. Sheet resistivity lies in the range of 6.8–318\mathrm{\Omega }/\mathrm{s}\mathrm{q} for thicknesses between 16 and 280\text{\hspace{0.17em} nm} . The best carrier mobility is obtained on BK7 and sapphire substrates, up to \sim 50{\text{cm}}^{\text{2}}/\text{V \hspace{0.17em} s} . The material shows good infrared transparency in the 3–5\mu \text{m} range on magnesium fluoride and 0.4–4\mu \text{m} on sapphire, and it is usable for practical applications up to 12\mu \text{m} on zinc sulfide. Simulations have been carried out for optical indices and spectra calculations. The Drude model has been used to exploit the results in either direction: from electrical measured data to the simulation of optical spectra and indices, and from measured optical spectra to simulated optical indices and electrical parameters (mobility, carrier density). Hall mobility is considered a worthy and convenient material quality criteria for materials aimed at optics.