Аннотация:The two-frequency wave function of biphotons generated in the processof spontaneous four-wave mixing in a photonic crystalfiber is studied. A method for estimating the degree of entanglement ofbiphotons by time-frequency variables is presented and tested experimentally. The degree of spectral anti-correlation of a two-photon wave packet, which can be used as an alternative to the Schmidt and Fedorovparameters for estimating spectral entanglement, is revealed. The results on two-photon interference in aMach–Zehnder interferometer are used to determine the parameter of spectral anticorrelation for the stategenerated in the four-wave mixing process in the photonic crystalfiber.