Polymer based FP cavity on a SMF fiber tip: a fabrication strategy for repeatable cavity length

A fiber-based Fabry–Perot (FP) optical sensor is well-suited for the rapid and selective detection of gas molecules, including volatile organic compounds (VOC), explosive analytes, etc. The sensing probe of a fiber-based Fabry–Perot (FP) sensor is achieved through the deposition of a thin vapor-sensitive material on a cleaved fiber end-face, primarily using the dip-coating method. Because the sensitivity of the FP sensor is closely tied to its cavity length, it is crucial for the coating mechanism to consistently create FP cavities of the same length and thickness. The paper details a process for the controlled deposition of polymer onto an optical fiber, achieved through dip coating. The determination of the shape, size, and other properties of the polymer-based FP cavity involved a comprehensive analysis of the coating steps. Fabricated sensors were further used to evaluate the temporal progression of acetone sensing experiments in response to VOC. Taken as a whole, the outcomes outlined in this paper underscore the potential for achieving consistent coating/cavity thickness in a single-mode fiber.