Аннотация:We consider possible ways to recognize multi-photon entangled states in experiment. A commonly used technique is to measure higher-order multi-photon correlation functions and their dependence on certain phase delays (multi-photon interference). Theoretically and experimentally, we show that multi-photon interference can have very high visibility for classical sources: up to 81.8% in the three-photon case and up to 94.4% in the four-photon one. Therefore, the visibility of multi-photon interference should not be used as a criterion of multi-photon entangled states generation. Instead, we suggest to characterize multi-photon entanglement by the photon-number dependence of the normalized correlation functions.