2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/93329The effects of dispersion in the communication channel on the secrecy of a quantum cryptosystem based on single photon states with different frequencies are studied. A maximum communication channel length which can still ensure the secrecy of the key generation procedure is found.6 pages, LaTex, no figures. Submitted to JETP LettersQuantum Physicstext