A novel twin-core fiber grating sensor system and its applications

We demonstrated a novel twin-core fiber grating sensor system for accurate and simultaneous measurements of temperature and strain. Specifically, we designed two cores with custom index and dopant profiles such that the gratings in these two cores have different temperature coefficients, but almost same strain coefficients. Our data also showed that both gratings had almost the same wavelength shift at the same deuterium concentration level in the fiber. This, together with the strain characteristics of the gratings, enables us to isolate the temperature measurement when strain, temperature and gaseous diffusion all apply to the sensor simultaneously. It makes our grating sensor extremely useful for hydrothermal down-hole temperature mapping applications.