Study of the sensitivity to water vapor of apolymer blend film coated on a waveguide

Abstract

Ablend of Polyvinyl pyrrolidone (PVP) and Polyethylene glycol (PEG) film was coated on an optical fiber using dip coating technique. The use of this film as a water vapor sensor was studied. The hydrogen fluoride (HF) acid was used to remove part of the fiber surface.  The fiber corrosion and the interaction between the acid and the fiber was controlled optically by a laser diode at 635nm. The sensor is based on the effect of the surrounding water vapor on the film refractive index, thus the wave guiding condition in the fiber. the sensor was operational for values of water vapor ratio extending from 65% to 95%, with a sensitivity of 0.0934 dB/RH. The sensor was found to be linear for this interval with . The use of this sensor  respiration monitoring was verified experimentally and the response time was estimated  to be 0.033 s/RH%.