Testing of Fiber-Optic Lines for Quantum Key Distribution

The paper describes a technique for measuring an optical noise in a fiber-optic channel using quantum key distribution equipment. The equipment under investigation is placed on different sides of the communication channel and consisted of client and server. The client and server can distribute the quantum key using phase-time encoding protocol. They are controlled by computer via ethernet switch. A special software is developed to synchronize the client with server and measure the optic noise in cannel. The described technique allows, on the one hand, to determine the optical noise in units of a single-photon-detector counts, on the other hand, it allows to understand the applicability of this equipment on this optical communication channel.