Optical Review

, 15:84 | Cite as

Use of polyethylene glycol coatings for optical fibre humidity sensing

  • Sabriye Acikgoz
  • Bukem Bilen
  • Mustafa Muamer Demir
  • Yusuf Ziya Menceloglu
  • Yani Skarlatos
  • Gulen Aktas
  • Mehmet Naci InciEmail author
Regular Papers


Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystalline structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed.

Key words

humidity sensors plastic fibre optics polyethylene glycol 


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Copyright information

© The Optical Society of Japan 2008

Authors and Affiliations

  • Sabriye Acikgoz
    • 1
  • Bukem Bilen
    • 1
  • Mustafa Muamer Demir
    • 2
  • Yusuf Ziya Menceloglu
    • 3
  • Yani Skarlatos
    • 1
  • Gulen Aktas
    • 1
  • Mehmet Naci Inci
    • 1
    Email author
  1. 1.Department of PhysicsBogazici UniversityIstanbulTurkey
  2. 2.Department of ChemistryIzmir Institute of TechnologyIzmirTurkey
  3. 3.Faculty of Engineering and Natural SciencesSabanci UniversityIstanbulTurkey

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