Co/Ti multilayered films (MLF) (d(Co) = 1,2, 2.5, 3.3 and 4 nm, d(Ti) = 2.5 nm) were prepared at room temperature by a computer-controlled double-pair-target face-to-face sputtering technique. The optical conductivity (OC) and the equatorial Kerr effect (EKE) were measured at room temperature in a spectral range of 1-5 eV as well as the magnetic properties. In addition, the theoretical simulations for the EKE and OC spectra were carried out by solving exactly a multireflection problem with a matrix method, assuming either sharp interfaces or mixed (alloyed) interfaces of various thickness between sublayers. The agreement between the experimental and simulated OC spectra was improved when intermixed layers of 0.6 nm thick were assumed between the sublayers. The atomic and magnetic structures of the Co/Ti MLF with a CO sublayer thickness above and below a critical value were also investigated, The significant difference in the experimental and simulated EKE spectra below the critical thickness was analyzed in terms of a polycrystalline-to-nanocrystalline (or amorphous) structural transition of Co sublayers.