IRF-S Series Chalcogenide Mid-Wave Infrared (MWIR) Fiber (1.5 to 6.5µm)

Chalcogenide glass is based on the chalcogen elements (sulfur, selenium and tellurium) with the addition of other elements such as arsenic, antimony, or germanium. It offers promising properties such as transmission in mid and far infrared regions of spectra, lower values of phonon energies, high refractive index and very large nonlinearities as compared to silica. Chalcogenide glass fibers are the ideal candidates for mid-infrared applications that require high power laser delivery, chemical sensing, thermal imaging and temperature monitoring.

IRflex’s IRF-S Series mid-wave infrared (MWIR) fiber, made from extra high purity chalcogenide glass As2S3, is specially designed and manufactured to generate and/or guide mid-infrared wavelengths from 1.5 to 6.5µm with high transmission efficiency and nonlinearities about 100 times that of silica glass fiber.

IRF-S-100 and IRF-S-200 multimode fibers have typical optical loss of 0.05dB@2.8µm and 0.08dB@4.8µm wavelength, which are the lowest loss in the market. The IRF-S-100 fiber was initially designed to use in high-power infrared countermeasure (IRCM) lasers for missile defense.

IRF-S-6.5 and IRF-S-9 singlemode fibers have transmission range from 1.5-6.5µm and minimum transmission loss of approximately 0.1dB/m at 4.8µm.  Given their approximately 6.5 and 9µm core diameters, and 0.28 and 0.225 numerical aperture, the step-index fibers are truly single-mode for wavelengths larger than their 2.46 and 2.65µm cutoffs.  For wavelengths shorter than the cutoffs and with proper coupling, the transmitted beam could remain single-mode (or slightly multimode) over short length of fiber (< 2 m) for their entire fiber transmission range.

IRF-S-50 multimode fiber is developed to use for the fabrication of mid-infrared fused combiners.  The 50/85 µm core/clad design is ideal for making 7x1 fiber combiners having our IRF-S-100 as the output fiber.  But the 50/80µm core/clad structure will be too fragile to terminate with connectors and used as standalone fiber cable.

The fibers can be sold as bare fibers.  All bare fiber, except IRF-S-5 and IRF-S-50, can be terminated with connectors and sold as cables.

The standard fiber cables are terminated with FC/PC, FC/APC or SMA905 connectors with stainless steel ferrules.  IRflex's FC/B® connector - the FC connector at Brewster Angle enables perfect coupling without reflection with polarized laser beam, is also available upon request.

The protective jacket can be stainless steel, stainless steel with PVC or clear FEP sheathing, PVDF and PVC.  Other different cable assembling configurations are offered upon request.



  • Extra low loss, 0.05dB/m @2.8µm
  • High power handling strength, tested in house, 6.9W CW in a 9µm core diameter fiber (previous batch) for 30 minutes without damage or degradation
  • High mechanical flexibility


  • Mid-IR Laser beam delivery
  • IR spectroscopy
  • Chemical sensing
  • Scientific and medical diagnostics IR-imaging system
  • Nonlinear supercontinuum generation
  • Infrared countermeasure (IRCM)
Fiber Model Core/Clad/Coating Diameter (µm) Cutoff Wavelength (µm) Operation Wavelength (µm)*
IRF-S-6.5 6.5/125/300 2.46 1.5 – 4.15
IRF-S-9 9/170/330 2.65 1.5 – 5.3
IRF-S-50 50/85/275 - 1.5 – 6.5
IRF-S-100 100/170/340 - 1.5 – 6.5
IRF-S-200 200/250/470 - 1.5 – 6.5

Note:  * Operation Wavelength (µm) range is defined as >50% more light remaining inside of the core.


Technical Specifications

Transmission Range (µm) 1.5 – 6.5
Typical Optical Loss (dB/m) 0.05 @ 2.8μm
Glass Composition As2S3
Refractive Index 2.4
Numerical Aperture (NA) 0.30±0.02
Core Non-Circularity (%) <1
Core/Clad Concentricity Error (μm) <3
Tensile Proof Test (kpsi) >15

Chemical Resistance

Insoluble in water, concentrated hydrochloric acid, non-oxidizing acids, alcohol, acetone, gasoline, and toluene. Soluble in strong alkaline solutions, such as KOH.