Optical fiber gas sensors based on hydrophobic alumina thin films formed by the electrostatic self-assembly monolayer process

Optical fiber gas sensors have been fabricated by deposition of Al₂O₃ and polymer ultra-thin films on the ends of optical fibers using the electrostatic self assembly monolayer process. These sensors are designed to operate at the standard transmission wavelengths with no cross sensitivity to temperature from at least 10 to 70°C. Experimental results of the response of these sensors to organic volatile compounds such as acetone, dichloromethane, or ethanol, are presented. In addition, a thermal curing process is proposed for achieving a humidity cross sensitivity of less than 1.4% from 11% to 85% of relative humidity, this cross sensitivity was still negligible after one year of the thermal curing process.