Refractive index sensing properties of long-period fibre grating with sol-gel derived coatings

Edward Davies, Lin Zhang, Ian Bennion, Reeta Viitala, Mikko Salomäki, Sami Areva

Research output: Contribution to journalArticlepeer-review


Long-period fibre gratings (LPGs) have previously been used to detect quantities such as temperature, strain and refractive index (RI). The responsivity to surrounding refractive index means that, potentially, LPGs could be realised as optical biosensors for applications in biochemical and biomedical application areas. We report here to our best knowledge the first investigation on refractive index sensing properties of LPGs with sol-gel derived titanium and silicon oxide coatings. It is revealed that the RI sensitivity of an LPG is affected by both the thickness and the index value of the coating; the coating with higher index and thickness will enhance the LPG RI sensitivity significantly. The surrounding refractive index induced LPG resonance shift has been evaluated over the LPGs’ most sensitive RI region from 1.42 to 1.44. We have identified that, in this region, the uncoated LPG has an RI sensitivity of (-673.0±0.4)nm/uri (unit of refractive index) while the LPG coated with titanium oxide exhibits a sensitivity as high as (-1067.15±0.04)nm/uri.
Original languageEnglish
Pages (from-to)286-289
Number of pages4
JournalIEEE Sensors Proceedings
Publication statusPublished - 26 Oct 2008

Bibliographical note

7th IEEE SENSORS Conference, Lecce (IT), 26-29 October 2008.


  • photonics
  • sensing
  • fibre-grating
  • sol-gel
  • diffraction gratings
  • fibre optic sensors
  • refractive index measurement
  • SiO2
  • TiO2
  • biochemical application
  • long-period fibre gratings
  • optical biosensors
  • silicon oxide coatings
  • sol-gel derived titanium oxide coatings


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