Monocrystals of ${\mathrm{Ag}}_{1-x}{\mathrm{Tl}}_x{\mathrm{Br}}_{1-x}{\mathrm{I}}_x$ and ${\mathrm{Ag}}_{1-x}{\mathrm{Tl}}_x{\mathrm{Cl}}_y{\mathrm{I}}_z{\mathrm{Br}}_{1-y-z}$ for the spectral range from 2.0 to 40.0 μm with improved photostability were developed and grown. The grown crystals were used for fabrication of single-mode IR fibers. Experimental studies of optical properties of these fibers have confirmed their single-mode operation at ${\mathrm{CO}}_2$ laser wavelength and demonstrated wider mode field for microstructured fiber compared to fibers with conventional double-layered structure.