Resonant couplings in U-shaped fibers for biosensing

U-shaped tight curvatures in optical fibers lead to resonant couplings between the fundamental and higher order modes that are sensible different parameters, such as strain or temperature, for example. The response of sensor consists on shift wavelength coupling. In case singlemode fibers, coupling involves a so-called “cladding mode” and, due its evanescent field, curved region will be changes external medium, well. this paper, we present fabrication characterization robust, easy-to-make, fiber based telecom application biosensing. nature sensing mechanism presents advantage large dynamic ranges RI variations without ambiguity other techniques interferometry. We studied performance bending radii, optimize sensitivity detection limit at 1550 nm operation wavelength, well effect temperature response. was measured detail function within range [1.33-1,37]; established (3.71±0.03)×10 -5 RIU. Furthermore, device successfully tested proof concept biosensor, using system model antigen-antibody (BSA-aBSA.)