Thermal annealing can be used to induce a permanent negative Bragg wavelength shift for polymer fibre grating sensors and it was originally used for multiplexing purposes. Recently, researchers showed that annealing can also provide additional benefits, such as strain and humidity sensitivity enhancement and augmented temperature operational range. The annealing process can change both the optical and mechanical properties of the fibre. In this paper, the annealing effects on the stress and force sensitivities of PMMA fibre Bragg grating sensors are investigated. The incentive for that investigation was an unexpected behaviour observed in an array of sensors which were used for liquid level monitoring. One sensor exhibited much lower pressure sensitivity and that was the only one that was not annealed. To further investigate the phenomenon, additional sensors were photo-inscribed and characterised with regard their stress and force sensitivities. Then, the fibres were annealed by placing them in hot water, controlling with that way the humidity factor. After annealing, stress and force sensitivities were measured again. The results show that the annealing can improve the stress and force sensitivity of the devices. This can provide better performing sensors for use in stress, force and pressure sensing applications.
|Conference||6th European Workshop on Optical Fibre Sensors|
|Abbreviated title||EWOFS 2016|
|Period||31/05/16 → 3/06/16|
A. Pospori ; C. A. F. Marques ; D. Sáez-Rodríguez ; K. Nielsen ; O. Bang and D. J. Webb, "Sensitivity enhancement using annealed polymer optical-fibre-based sensors for pressure sensing applications", Proc. SPIE 9916, Sixth European Workshop on Optical Fibre Sensors, 99160E (May 30, 2016).
Copyright 2016 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.
Funding: EU 7FP (FP7/2007-2013, REA grant agreement No. 608382) People Programme (Marie Curie Actions); and EU 7FP (projects PIEF-GA-2013-628604 and PIEF-GA-2011-302919) Marie Curie Intra European Fellowships.