Humidity Sensor Based on Bragg Gratings Developed on the End Facet of an Optical Fiber by Sputtering of One Single Material

Joaquin Ascorbe; Jesus M Corres; Francisco J Arregui; Ignacio R Matias

doi:10.3390/s17050991

Humidity Sensor Based on Bragg Gratings Developed on the End Facet of an Optical Fiber by Sputtering of One Single Material

Sensors (Basel). 2017 Apr 29;17(5):991. doi: 10.3390/s17050991.

Authors

Joaquin Ascorbe¹, Jesus M Corres², Francisco J Arregui³, Ignacio R Matias⁴

Affiliations

¹ Department of Electrical and Electronic Engineering, Public University of Navarra, Pamplona 31006, Spain. joaquin.ascorbe@unavarra.es.
² Institute of Smart Cities, Public University of Navarra, Pamplona 31006, Spain. jmcorres@unavarra.es.
³ Institute of Smart Cities, Public University of Navarra, Pamplona 31006, Spain. parregui@unavarra.es.
⁴ Institute of Smart Cities, Public University of Navarra, Pamplona 31006, Spain. natxo@unavarra.es.

Abstract

The refractive index of sputtered indium oxide nanocoatings has been altered just by changing the sputtering parameters, such as pressure. These induced changes have been exploited for the generation of a grating on the end facet of an optical fiber towards the development of wavelength-modulated optical fiber humidity sensors. A theoretical analysis has also been performed in order to study the different parameters involved in the fabrication of this optical structure and how they would affect the sensitivity of these devices. Experimental and theoretical results are in good agreement. A sensitivity of 150 pm/%RH was obtained for relative humidity changes from 20% to 60%. This kind of humidity sensors shows a maximum hysteresis of 1.3% relative humidity.

Keywords: diffraction gratings; fiber optics sensors; interference coatings; optical fiber humidity sensors; thin-film; transparent conductive coatings.