The spectral sensitivity of long period gratings fabricated in elliptical core D-shaped optical fiber

Thomas D.P. Allsop, Timothy Earthgrowl, Helen Dobb, Vladimir Mezentsev, Andrew Gillooly, David J. Webb, Ian Bennion

Research output: Chapter in Book/Published conference outputConference publication


Long period gratings (LPGs) were written into a D-shaped optical fibre, which has an elliptical core with a W-shaped refractive index profile. The LPG's attenuation bands were found to be sensitive to the polarisation of the interrogating light with a spectral separation of about 15nm between the two orthogonal polarisation states. In addition, two spectrally overlapping attenuation bands corresponding to orthogonal polarisation states were observed; modelling successfully reproduced this spectral feature. The spectral sensitivity of both orthogonal states was experimentally measured with respect to temperature, surrounding refractive index, and directional bending. These LPG devices produced blue and red wavelength shifts of the stop-bands due to bending in different directions. The measured spectral sensitivities to curvatures, d?/dR , ranged from -3.56nm m to +6.51nm m. The results obtained with these LPGs suggest that this type of fibre may be useful as a shape/bend sensor. It was also demonstrated that the neighbouring bands could be used to discriminate between temperature and bending and that overlapping orthogonal polarisation attenuation bands can be used to minimise error associated with polarisation.
Original languageEnglish
Title of host publicationFiber optic sensor technology and applications III
EditorsMichael A. Marcus, Brian Culshaw, John P. Dakin
Place of PublicationPhiladelphia, PA (US)
Number of pages12
Publication statusPublished - 2004
EventConference on Fiber Optic Sensor Technology and Applications III - Philadelphia, United States
Duration: 26 Nov 200428 Nov 2004

Publication series

NameSPIE proceedings
ISSN (Electronic)0277-786X


ConferenceConference on Fiber Optic Sensor Technology and Applications III
Country/TerritoryUnited States

Bibliographical note

Thomas D. Allsop ; T. Earthrowl ; H. Dobb ; V. Mezentsev ; A. Gillooly ; D.J. Webb and I. Bennion "The spectral sensitivity of long-period gratings fabricated in elliptical core D-shaped optical fiber", Proc. SPIE 5589, Fiber Optic Sensor Technology and Applications III, 266 (December 14, 2004);

Copyright 2004 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.


  • long-period fibre gratings
  • temperature measurement
  • curvature measurement
  • d-shaped optical fibre


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