Reducing fiber scattering loss through hot-diffusion: a study on eliminating core–cladding interface defects

Currently, the loss of chalcogenide fibers is two or more orders of magnitude higher than theoretical predictions. A major factor contributing to this difference is the optical scattering caused by rough interfaces between the fiber core and cladding. We fabricate an optical fiber preform using the extrusion-assisted hot-diffusion method. The quality of the core-cladding interface and diffusion was characterized using scanning electron microscope (SEM)-energy-dispersive x-ray spectroscopy (EDS) and Raman spectroscopy. A diffusion depth of 40.5 μm was achieved in a hot-pressing environment at 320°C. The defect and diffusion layers were modeled to understand the impact of hot-diffusion on light scattering loss in the fiber. The chalcogenide fibers were drawn and analyzed, and the results confirmed that the hot-diffusion treatment was effective in reducing the loss of the fiber. The average fiber loss was reduced by 58%, from 4.5 to 1.88 dB/m in the 5-6 μm range, with a minimum loss of 0.68 dB/m at 2.64 μm.