METHOD AND DEVICE FOR QUANTUM KEY DISTRIBUTION WITH CONTROL OF QUANTUM CHANNEL PARAMETERS Russian patent published in 2025 - IPC H04L9/08 

FIELD: quantum cryptography.

SUBSTANCE: device has a module for measuring the length of an optical fibre, which includes a first FWDM filter, a second optical circulator, a second radiation source, a device for detecting optical pulses, a second FWDM filter and a first mirror. Polarization controller output is connected by fibre to FWDM filter pass output, which output com is made with possibility of connection to external fibre communication line, in its turn output ref of FWDM filter is connected in port II of second optical circulator, to port I of which a radiation source is connected at a wavelength different from the FWDM filter, optical pulse recorder is connected to port III. FWDM filter pass output is connected to the input of the third fibre beam splitter, a fibre mirror is connected to the ref output, and the com output is configured to be connected to an external fibre communication line.

EFFECT: providing control of the length of a fibre-optic communication line between spatially remote modules of a quantum key distribution device and high rate of generating and distributing a secret key in conditions of variable length of the fibre-optic communication line.

2 cl, 2 dwg