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Proceedings Paper

Humidity sensor based on optical fiber coated with agarose gel
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Paper Abstract

A reflective fiber optic sensor based on multimode interference for the measurement of relative humidity (RH) is proposed and experimentally demonstrated. The proposed probe is fabricated by fusion-splicing, approximately 30 mm long coreless fiber section to a single mode fiber. A hydrophilic agarose gel is coated on the coreless fiber, using the dip coating technique. When the incident light comes from the SMF to the CSF, the high-order modes are excited and propagate within the CSF. These excited modes interfere with one another as they propagate along whole CSF length, giving rise to a multimode interference (MMI). Since the effective refractive index of the agarose gel changes with the ambient relative humidity, as the environmental refractive index changes, the propagation constants for each guided mode within the CSF will change too, which leads to shifts in the output spectra. The proposed sensor has a great potential in real time RH monitoring, exhibiting a large range of operation with good stability. For RH variations in the range between 60 %RH and 98.5 %RH, the sensor presents a maximum sensitivity of 44.2 pm/%RH, and taking in consideration the interrogation system, a resolution of 1.1% RH is acquired. This sensor can be of interest for applications where a control of high levels of relative humidity is required.

Paper Details

Date Published: 11 April 2019
PDF: 7 pages
Proc. SPIE 11028, Optical Sensors 2019, 110281K (11 April 2019); doi: 10.1117/12.2520572
Show Author Affiliations
Susana Novais, Univ. de Aveiro (Portugal)
Marta S. Ferreira, Univ. de Aveiro (Portugal)
João L. Pinto, Univ. de Aveiro (Portugal)

Published in SPIE Proceedings Vol. 11028:
Optical Sensors 2019
Francesco Baldini; Jiri Homola; Robert A. Lieberman, Editor(s)

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