Soares, LilianaPérez Herrera, Rosa AnaNovais, SusanaFerreira, AntónioSilva, SusanaFrazão, Orlando2023-04-282023-04-282023Soares, L., Pérez-Herrera, R. A., Novais, S., Ferreira, A., Silva, S., & Frazão, O. (2023). Measurement of paracetamol concentration using an erbium-doped fiber ring cavity. Photonics, 10(1), 50. https://doi.org/10.3390/photonics100100502304-673210.3390/photonics10010050https://academica-e.unavarra.es/handle/2454/45191Process Analytical Technology (PAT) has been increasingly used in the pharmaceutical industry to monitor essential parameters in real-time during pharmaceutical processes. The concentration of Active Pharmaceutical Ingredients (APIs), such as paracetamol, is one of these parameters, and controlling its variations allows for optimization of the production process. In this study, a refractometric sensor, implemented by an interrogation system based on an Erbium-Doped Fiber Ring Cavity (EDFRC), was presented and experimentally demonstrated. The Cavity Ring proposed included a 1 × 3 coupler. One port of the coupler was used to increase the optical power of the system through a Fiber Bragg Grating (FBG), and the other two ports were used as sensing head and reference. The sensor detected variations of paracetamol concentration with a sensitivity of [(−1.00 ± 0.05) × 10−3] nW/(g/kg) and a resolution of 5.53 g/kg. The results demonstrate the potential of this technology as a possible non-invasive PAT tool.application/pdfeng© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.ConcentrationErbium-doped fiberParacetamolProcess analytical technologyRing cavityinfo:eu-repo/semantics/article2023-04-28info:eu-repo/semantics/openAccess