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


Long period gratings (LPGs) were written into a D-shaped optical fibre that has an elliptical core with a W-shaped refractive index profile and the first detailed investigation of such LPGs is presented. The LPGs’ attenuation bands were found to be sensitive to the polarisation of the interrogating light with a spectral separation of about 15 nm between the two orthogonal polarisation states. A finite element method was successfully used to model many of the behavioural features of the LPGs. 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 and bending. These LPG devices produced blue and red wavelength shifts depending upon the orientation of the bend with measured maximum sensitivities of -3.56 and +6.51 nm m, suggesting that this type of fibre LPG may be useful as a shape/bend orientation sensor with reduced errors associated with polarisation dependence. The use of neighbouring bands to discriminate between temperature and bending was also demonstrated, leading to an overall curvature error of ±0.14 m-1 and an overall temperature error of ±0.3 °C with a maximum polarisation dependence error of ±8 × 10-2 m-1 for curvature and ±5 × 10-2 °C for temperature.

Uncontrolled Keywords: Long-period fibre gratings, Optical fibre devices, temperature measurement, curvature measurement, D-shaped optical fibre
Publication ISSN: 0030-4018
Last Modified: 23 Oct 2019 10:41
Date Deposited: 13 Dec 2010 12:44
Published Date: 2006-03
Authors: Allsop, Thomas D.P.
Dobb, Helen L.
Mezentsev, Vladimir
Earthgrowl, T.
Gillooly, Andrew M.
Webb, David J.
Bennion, Ian


Item under embargo.

Export / Share Citation


Additional statistics for this record