FIELD: physics.
SUBSTANCE: invention relaters to fibre-optic communication systems and specifically to single-mode double-layered crystalline infrared light-guides for the 2-50 mcm spectral range. The light-guide comprises a core and a cladding. The 10-250 mcm diameter core is made of silver bromide-based crystals containing a solid solution of monovalent thallium bromide-iodide, with the following ratio of components, wt %: silver bromide 98.8-65.0; solid solution 1.2-35.0. The 0.6-1.1 mm diameter cladding is made of crystals based on the same material, with the following ratio of components, wt %: silver bromide 99.0-69.5; solid solution 1.0-30.5.
EFFECT: expanding the operating spectral range of the light-guide in the long-wave region to 50 mcm and high light resistance.