Development of methods for increasing the length of a fiber-optical communication channel of a quantum-cryptographic system

The article discusses the method for increasing the length of the fiber-optic communication channel of a quantum-cryptographic system. The article also discusses the technical side of the physical limitation of the length of the fiber-optic communication line: calculation, analysis and visualization in the form of graphs of the key dependences of the visibility and quantum error rate on the length of the fiber communication line were carried out. The installation of the quantum repeater in a quantum cryptosystem is considered as the method to increase the length of the fiber-optic communication channel.