Shaimerdenova, MadinaAyupova, TakhminaSypabekova, MarzhanTosi, Daniele2021-02-172021-02-172020-10-30Shaimerdenova, M., Ayupova, T., Sypabekova, M., & Tosi, D. (2020). Fiber Optic Refractive Index Sensors Based on a Ball Resonator and Optical Backscatter Interrogation. Sensors, 20(21), 6199. https://doi.org/10.3390/s202161991424-8220https://www.mdpi.com/1424-8220/20/21/6199https://doi.org/10.3390/s20216199http://nur.nu.edu.kz/handle/123456789/5312In this work, we introduced fabrication and interrogation of simple and highly sensitive fiber-optic refractive index (RI) sensors based on ball resonators built on the tip of single-mode fibers. The probes have been fabricated through a CO2 fiber splicer, with a fast (~600 s) and repeatable method. The ball resonator acted as a weak interferometer with a return loss below −50 dB and was interrogated with an optical backscatter reflectometer measuring the reflection spectrum. The ball resonators behaved as weak interferometers with a shallow fringe and a spectrum that appeared close to a random signal, and RI sensitivity could be measured either through wavelength shift or amplitude change. In this work, we reported four samples having sensitivity ranges 48.9–403.3 nm/RIU and 256.0–566.2 dB/RIU (RIU = refractive index unit). Ball resonators appeared as a sensitive and robust platform for RI sensing in liquid and can be further functionalized for biosensing. View Full-Text Keywords: optical fiber sensors; optical resonators; refractive index sensors; optical backscatter reflectometry; ball resonatorenAttribution-NonCommercial-ShareAlike 3.0 United Statesoptical fiber sensorsoptical resonatorsrefractive index sensorsoptical backscatter reflectometryball resonatorResearch Subject Categories::TECHNOLOGYArticle