By means of differential thermal analysis the new AgBr – TlI system phase equilibrium diagram, including phase transition temperatures and crystal system for TlI modifications, has been studied. The stable substitutional solid solution existence region was then determined. Maximum solubility of TlI in AgBr proved to be 25 wt. %. The eutectic of the above system melts at 160 oC and contains 60 wt. % of TlI and 40 wt. % of AgBr. The eutectic position was also confirmed by virtue of Tammann's triangle built by using the peak heights characterizing the solid solution thermal effects for the system under investigation. Improved apparatus KPC-02 for crystal growth implements vertical Bridgman technique with low-frequency axial vibrations being introduced into the melt. It is characterized by the stability of temperature gradient supported, increased grown crystal size, and wide growth rate variation range. The chemical and mechanical treatment method for extrusion billet is also improved, which helps to get rid of undesirable fiber impurities due to reaction atmosphere created in extrusion container. We worked out the growth modes for photostable crystals which the nanocrystalline IR fibers for the widespread use are extruded from. For operating at CO 2-laser wavelength single-mode IR fibers were produced on the basis of structure simulating by Matlab SMTP [1] and fundamental characteristic theoretical calculations. It was found that new single-mode nanostructured IR fibers possess wide transparency range (2.0 – 40.0 μm), increased photostability, in comparison with AgBr – AgCl system, low optical losses in the infrared, high plasticity, non-hygroscopicity and radiation resistance. Properties above are largely due to monovalent thallium iodide introduction into parent silver bromide crystal lattice allowing grain recrystallization of the IR fiber obtained to be blocked.