Optimal wavelength pair selection and accuracy analysis of dual fiber grating sensors for simultaneously measuring strain and temperature

We investigate the wavelength selection of dual fiber grating sensors for strain and temperature measurements. Temperature and strain coefficients of fiber gratings are measured in the wavelength range of 600 to 1600 nm in Corning Flexcor-980™ fiber. Theoretical fits are estimated using Ghosh's temperature-dependent refractive index model for optical fiber glasses. Moreover, the effect of apparent thermal strain due to the structural thermal expansion on the temperature coefficient in a surface-bonded fiber grating sensor is investigated, and numerical re- sults for the accuracy of temperature and strain are presented. It is shown that the structural thermal properties have a large influence on the resolution and measurement accuracy of dual fiber grating sensors.