Esteban Martínez, ÓscarNavarrete Fernández, María CruzGonzález Cano, AgustínBernabeu Martínez, Eusebio2023-06-202023-06-201999-09-011. J. Dankin, Optical Fiber Sensors (Artech House, Norwood, Mass., 1989). 2. S.-M. Tseng, C.-L. Chen, “Side-polished fibers”, Appl. Opt. 31, 3438–3447 (1992). 3. R. Alonso, F. Villuendas, J. Tornos, J. Pelayo, “New ‘in-line’ optical-fibre sensor based on surface plasmon excitation”, Sens. Actuators A 37–38, 187–192 (1993). 4. D. Marcuse, “Investigation of coupling between a fiber and an infinite slab”, J. Lightwave Technol. 7, 122–130 (1989). 5. A. Tz. Andreev, K. Panajotov, “Distributed single-mode fiber to single-mode planar waveguide coupler”, J. Lightwave Technol. 11, 1985–1989 (1993). 6. R. Alonso, “Estudio teórico y experimental de dispositivos ópticos basados en el acoplamiento entre el modo guiado por una fibra óptica y estructuras multicapa incluyendo medios metálicos”, Ph.D. dissertation (Universidad de Zaragoza, Spain, 1995). 7. K. S. Shifrin, Physical Optics of Ocean Water (American Institute of Physics, New York, 1988). 8. X. Quan, E. S. Fry, “Empirical equation for the index of refraction of seawater”, Appl. Opt. 34, 3477–3480 (1995).1559-128X10.1364/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