Multimode interference-based strain sensing using micro dry-etched perfluorinated polymer optical fibers

This study explores the impact of a micro dry-etching technique on strain sensing based on multimode interference in a perfluorinated polymer optical fiber (POF). We demonstrate a drastic shift in strain sensitivity, from +34 nm/% in a non-etched POF to −981 nm/% in the etched POF. This notable change may be attributed to the excitation of the axially asymmetrical modes in the etched POF, which is confirmed through simulation on the stress distribution across the core. In addition, a critical wavelength for multimode interference is observed in a POF.