Fiber Optic Refractive Index Distributed Multi-Sensors by Scattering-Level Multiplexing with MgO Nanoparticle-Doped Fibers

In this work, we present the architecture of a multiplexed refractive index (RI) sensing system based on the interrogation of Rayleigh backscattering. The RI sensors are fabricated by fiber wet-etching of a high-scattering MgO nanoparticle-doped fiber, without the need for a reflector or plasmonic element. Interrogation is performed by means of optical backscatter reflectometry (OBR), which allows a detection with a millimeter-level spatial resolution. Multiplexing consists of a simultaneous scan of multiple fibers, achieved by means of scattering-level multiplexing (SLMux) concept, which uses the backscattered power level in each location as a diversity element. The sensors fabricated have sensitivity in the order of 0.473-0.568 nm/RIU (in one sensing point) and have been simultaneously detected together with a distributed temperature sensing element for multi-parameter measurement. An experimental setup has been prepared to demonstrate the capability of each sensing region to operate without cross-talk, while operating multi-fiber detection.