High Precision Fiber Loop Ringdown Chemical Corrosion Sensors

High precision control of single-mode fiber tapering processing, such as chemical corrosion, physical polishing, thermal tapering, etc. is challenging due to the fragility and microdimensions of the fiber. We introduce a new method based on the fiber loop ringdown (FLRD) technique to conduct real-time, on-line monitoring of the fiber etching process by using 48% hydrofluoric acid solutions. The corrosion process of the cladding of single-mode fibers (SFM-28) was monitored using the FLRD technique and the corroded surfaces of the fiber were visualized by Scanning Electron Microscopy with a resolution of 5 nm at an accelerating voltage of 1 kV. The corrosion processes monitored by the FLRD technique have a precision of 0.1 μs in terms of ringdown time, which corresponds to a 0.5 μm precision in fiber dimensions. This method can be further developed to monitor and control a chemical corrosion process, in realtime, on-line, and with high precision in many applications.