Two-layer chalcogenide-glass optical fibers with optical losses below 30 dB/km

Two-layer optical fibers have been fabricated from As-S chalcogenide glasses. The optical losses of these fibers are 23 ± 8 dB/km at a wavelength of 2.3 μm: a record low for IR optical fibers of this type. Between 1.3 and 2.7 μm, the optical losses do not exceed 100 dB/km. At the wavelength 2.94 μm of an Er:YAG laser, the losses do not exceed 350 dB/km. The far-zone numerical aperture of the fibers is 0.49 at the 90% power level.