title: Distributed Humidity Sensing in PMMA Optical Fibers at 500 nm and 650 nm Wavelengths.
abstract: Distributed measurement of humidity is a sought-after capability for various fields of application, especially in the civil engineering and structural health monitoring sectors. This article presents a method for distributed humidity sensing along polymethyl methacrylate (PMMA) polymer optical fibers (POFs) by analyzing wavelength-dependent Rayleigh backscattering and attenuation characteristics at 500 nm and 650 nm wavelengths. Spatially resolved humidity sensing is obtained from backscatter traces of a dual-wavelength optical time domain reflectometer (OTDR). Backscatter dependence, attenuation dependence as well as the fiber length change are characterized as functions of relative humidity. Cross-sensitivity effects are discussed and quantified. The evaluation of the humidity-dependent backscatter effects at the two wavelength measurements allows for distributed and unambiguous measurement of relative humidity. The technique can be readily employed with low-cost standard polymer optical fibers and commercial OTDR devices.
authors.affiliation: Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany. Sascha.Liehr@bam.de.
authors.forename: Sascha
authors.initials: S
authors.lastname: Liehr
authors.affiliation: Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany. mathias.breithaupt@bam.de.
authors.forename: Mathias
authors.initials: M
authors.lastname: Breithaupt
authors.affiliation: Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany. katerina.krebber@bam.de.
authors.forename: Katerina
authors.initials: K
authors.lastname: Krebber
keywords: OTDR; PMMA; Rayleigh scattering; backscatter measurement; distributed sensor; humidity sensor; optical fiber sensor; polymer optical fiber; spectral measurement