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Etched optical fiber immunosensors, with and without ITO nanodeposition, have been developed. The performance of these immunosensors has been assessed implementing an immunoassay. The sensitivity of the mmnunosensor increased by a factor of 4 with the ITO nanocoating, whereas the limit of the detection in both types of devices was 0.2 mg/L of antigens in solution. ; This work was supported in part by the Spanish Ministry of Education and Science-FEDER TEC 2016-78047 and by the Government of Navarre through its projects with references: 2017/PI008, 2016/PC025 and 2016/PC026. Besides, was supported in part by the Colombian Administrative Department of Science, Technology and Innovation - Colciencias, through the Program for national doctorates, calling 617 of 2013, and by the project 'Biosensores a fibra optica para la deteccion rapida de enfermedades' supported by the Universidad Nacional de Colombia (Hermes code 40834).

The performance of E-SMS (Etched Singlemode-Multimode-Singlemode) optical fiber structures as immunosensors has been assessed by the implementation of antibody/antigen immunoassays. Through this procedure it has been proven that E-SMS structures are effective and suitable optical platforms for label-free biosensing. Using the phase shift and tracking the wavelength response it was found that the fabricated E-SMS devices exhibited limits of detection (LOD) down up to concentrations of 0.2mg/L of antigens in solution. This was achieved by coating the E-SMS with an antibody-based biolayer (goat IgG) that is able to determine the presence of anti-goat IgG antigen. Both a wavelength detection and a fast Fourier transform (FFT) analysis technique were used to perform this analysis. The FFT method showed similar results to those observed with the most traditional wavelength analysis, but with the advantage of a simpler detection system that makes unnecessary the use of sophisticated optical interrogators. ; This work was supported in part by the Spanish Ministry of Education and Science - FEDER TEC 2016- 78047 and by the Government of Navarre through its projects with references: 2016/PI044, 2016/PC025 and 2016/PC026. This work was supported in part by the Colombian Administrative Department of Science, Technology and Innovation - Colciencias, through the Program for national doctorates, calling 617 of 2013, and by the project "BIOSENSORES A FIBRA ÓPTICA PARA LA DETECCIÓN RÁPIDA DE ENFERMEDADES" supported by the Universidad Nacional de Colombia (Hermes code 40834).

The development of an optical fiber refractometer by hydrogen fluoride etching and sputtering deposition of a thin-film of indium tin oxide on a single-mode-multimode-single-mode fiber structure has been analyzed with the aim of improving the sensitivity to the changes of the refractive index (RI) of the external medium. The device is sensitive to the RI changes of the surrounding medium, which can be monitored by tracking the spectral changes of an attenuation band or with a fast Fourier transform (FFT) analysis. By using an optical spectrum analyzer combined with a simple FFT measurement technique, the simultaneous real time monitoring is achieved. The results show that the sensitivity depends on the thin-film thickness. A maximum of 1442 nm/RIU (refractive index unit) in the 1.32–1.35RIUrange has been attained. In addition, a theoretical analysis has been performed, where simu lationsmatched with the experimental results. As a practical appli cation of the developed optical fiber structure, a °Brix (°Bx) sensor has been implemented with a sensitivity of 2.13 nm/°Bx and 0.25 rad/°Bx respectively for wavelength and phase shift detection. ; This work was supported in part by the Agencia Estatal de Investigacion, in part by Fondo Europeo de Desarrollo Regional (TEC2016-78047-R), in part by the Government of Navarre through its projects with references: 2016/PI008, 2016/PC025, and 2016/PC026, and in part by the Colombian Administrative Department of Science, Technology and Innovation—Colciencias, through the Program for national doctorates, calling 617 of 2013.

Trabajo presentado en la Eurosensors 2017 Conference. París, 3–6 de septiembre de 2017. ; An optical fibre refractometer has been developed by etching and deposition of a thin film of indium tin oxide (ITO) on a single-mode-multimode-single-mode (SMS) fibre structure. The interference between modes in this structure is sensitive to the refractive index changes of the surrounding medium, achieving sensitivities of up to 7000 nm/RIU in the 1.333–1.338 RIU range. A salinity sensor has been implemented as a practical application of this proposed structure. Fast Fourier transform (FFT) analysis and tracking of an interference dip were used to monitor the interference between modes obtaining sensitivities of 0.99 nm/PSU and 0.025 rad/PSU, respectively. ; This work was supported in part by the Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) (TEC2016-78047-R) and by the Government of Navarre through its projects with references: 2016/PI008, 2016/PC025 and 2016/PC026. As well, it was partially supported by the Colombian Administrative Department of Science, Technology and Innovation - Colciencias, through the Program for national doctorates, calling 617 of 2013.