We measured the optical reflectivity of [001]-oriented n-doped Cd3As2 in a broad frequency range (50-22 000 cm-1) for temperatures from 10 to 300 K. The optical conductivity, σ(ω)=σ1(ω)+iσ2(ω), is isotropic within the (001) plane; its real part follows a power law, σ1(ω)ω1.65, in a large interval from 2000 to 8000cm-1. This behavior is caused by interband transitions between two Dirac bands, which are effectively described by a sublinear dispersion relation, E(k)|k|0.6. The momentum-averaged Fermi velocity of the carriers in these bands is energy dependent and ranges from 1.2×105 to 3×105 m/s, depending on the distance from the Dirac points. We detect a gaplike feature in σ1(ω) and associate it with the Fermi level positioned around 100 meV above the Dirac points.