The response to temperature and refractive index (RI) of cascaded long period gratings operating at or near the phase matching turning point was studied. Temperature- and RI-induced changes of the phase of the channelled spectrum and wavelength shift of the long period grating’s resonance band envelope were observed for two conditions; when the length of fibre separating the long period gratings was perturbed and when the whole length of the device was perturbed. It is shown that when the central section of the device is perturbed the phase of the channelled spectrum changes and the envelope remains fixed, while when the entire device is perturbed the phase and central wavelength of the envelope shift at the same rate. Thus measurement of changes in the channelled spectrum with respect to the centre of the resonance band envelope offers a means for developing sensors whose response is compensated for temperature and RI.

Date Published: 2 June 2014
PDF: 4 pages
Proc. SPIE 9157, 23rd International Conference on Optical Fibre Sensors, 91574J (2 June 2014); doi: 10.1117/12.2059031

Published in SPIE Proceedings Vol. 9157:
23rd International Conference on Optical Fibre Sensors
José M. López-Higuera; Julian D. C. Jones; Manuel López-Amo; José Luis Santos, Editor(s)