  We propose a fiber-based environmental sensor that exploits the reflection
phase shift tunability provided by the use of layered coatings composed of
dielectric slabs spaced by conducting membranes. A transfer matrix study is
done in a simplified theoretical model, for which an enhanced sensitivity of
the reflection interference pattern to the output medium is demonstrated, in
the typical refractive index range of liquid media. An experimental
configuration using a cascaded Fabry-Perot microcavity coated by a graphene
oxide/polyethylenimine (GO/PEI) multilayered structure is demonstrated. Its
cost effective chemical production method makes graphene oxide-based hybrid
coatings excellent candidates for future real-life sensing devices.
