We studied Čerenkov radiation generated in irradiated optical fibers and demonstrated a generic spectroscopic method for separation of Čerenkov radiation from the transmitted signal in fiber optic dosimetry based on the assumption that the recorded signal is a linear superposition of two basis spectra: Čerenkov radiation and characteristic luminescence of the phosphor medium. Experimentally, we evaluated thistechnique by using fiber optic probes irradiated by electron beams generated by a clinical linear accelerator. This method can be used for optical characterization of various scintillating materials, such as phosphor nanoparticles, in ionizing radiation fields of high energy. We performed MonteCarlo simulations of the Čerenkov radiation generated in the fiber and found astrong dependence of the recorded Čerenkov radiation on the numerical aperture of the fiber at shallow phantom depths; however, beyond the depth of maximum dose that dependency is minimal. Oursimulation results agree well withthe experimental results for Čerenkov radiation generated in fibers irradiated with 6 MeV electrons.