Esteban Martínez, ÓscarNavarrete Fernández, María CruzGonzález Cano, AgustínBernabeu Martínez, Eusebio2023-06-202023-06-201999-09-011559-128X10.1364/AO.38.005267https://hdl.handle.net/20.500.14352/59242© Optical Society of America. We wish to thank to R. Alonso, C. Cosculluela, J. Pelayo, and F. Villuendas of the Department of Applied Physics, University of Zaragoza, Spain, for their support and for providing us with the sensors used for this work. This research has been supported by the European Union under Project SOFIE (spectroscopy using optical fibers in the marine environment), number MAS3-CT97-0157.A fiber-optic sensor based on surface-plasmon resonance for the determination of the refractive index is used for measuring the degree of salinity of water. The transducing element consists of a multilayer structure deposited on a side-polished monomode optical fiber. Measuring the attenuation of the power transmitted by the fiber shows that a linear relation with the refractive index of the outer medium of the structure is obtained. The system is characterized by use of a varying refractive index obtained with a mixture of water and ethylene glycol. Experimental results show that the sensor can be used as a salinity-degree measurement device with environmental applications.engjournal articlehttp://dx.doi.org/10.1364/AO.38.005267http://www.opticsinfobase.orgopen access535OpticsÓptica (Física)2209.19 Óptica Física