Advances in Optical Microfibers: From Fabrication to Functionalization and Sensing Applications

Currently, optical fibers play a leading role in telecommunications, serve as special transmission components for industrial applications, and form the basis of highly sensitive sensor elements. One of the most commonly used modifications is the reduction in the initial dimensions of the cladding and core to a few or several micrometers, allowing the evanescent wave emerging from the tapered region to interact with the surrounding environment. As a result, the microfiber formed in this way is highly sensitive to any changes in its surroundings, making it an ideal sensing element. This article primarily focuses on reviewing the latest trends in science involving various types of optical microfibers, including tapers, rings, loops, coils, and tapered fiber Bragg gratings. Additionally, it discusses the most commonly used materials for coating fiber optic elements-such as metals, oxides, polymers, organic materials, and graphene-which enhance sensitivity to specific physical factors and enable selectivity in the developed sensors.