The present disclosure relates to compositions that can be used for optical fibers and other systems that transmit light in the near-, mid- and/or far-ranges of the infrared spectrum, such as for example in the wavelength range of 1.5 μm to 14 μm. The optical fibers may comprise a light-transmitting chalcogenide core composition and a cladding composition. In some embodiments, the light-transmitting chalcogenide core composition has a refractive index n(core) and a coefficient of thermal expansion CTE(core), and the cladding composition has a refractive index n(cladding) and a coefficient of thermal expansion CTE(cladding), wherein n(cladding) is less than n(core) and in some embodiments wherein CTE(cladding) is less than CTE(core). In some embodiments, the chalcogenide glass core composition comprises a) sulfur and/or selenium, b) germanium, and c) gallium, indium, tin and/or one or more metal halides.

A hybrid mid-infrared-light transmitting glass fiber comprising a non-oxide infrared-light transmitting glass core, non-oxide glass inner cladding, and an oxide glass external cladding. In certain embodiments, the hybrid mid-infrared transmitting glass fiber is configured as a single mode fiber at a specific wavelength. In certain embodiments, the hybrid mid-infrared-light transmitting glass fiber is configured a polarization maintaining single mode fiber at a chosen specific wavelength.

The present disclosure relates to compositions that can be used for optical fibers and other systems that transmit light in the near-, mid- and/or far-ranges of the infrared spectrum, such as for example in the wavelength range of 1.5 m to 14 m. The optical fibers may comprise a light-transmitting chalcogenide core composition and a cladding composition. In some embodiments, the light-transmitting chalcogenide core composition has a refractive index n(core) and a coefficient of thermal expansion CTE(core), and the cladding composition has a refractive index n(cladding) and a coefficient of thermal expansion CTE(cladding), wherein n(cladding) is less than n(core) and in some embodiments wherein CTE(cladding) is less than CTE(core). In some embodiments, the chalcogenide glass core composition comprises a) sulfur and/or selenium, b) germanium, and c) gallium, indium, tin and/or one or more metal halides.