Fiber loop resonator sensor achieved by high-scattering MgO nanoparticle-doped fibers

A Sagnac loop-based fiber sensor has been built using a special MgO-based nanoparticle doped fiber. The fiber presents a backscattering of 39.5 dB higher with respect to a standard SMF-28 telecom fiber. The backscattering properties of the fiber, combined with a locally stable polarization pattern, have fostered a clear interferometer pattern in middle point of the loop, presenting a backscattering peak roughly 78 dB higher with respect to a standard SMF-28 telecom fiber. The interferometer spectrum, showing a noisy nature given by the presence of the NP-doped fiber element, is clearly detectable. The loop-based sensor has been investigated by changing temperature and strain. The interferometer spectrum shows a shift, detectable with peak tracking and/or correlation method, toward the longer wavelength when temperature and applied strain increase. The measured coefficient of temperature and strain are respectively 1.75 p.m./°C and 1.93 p.m./με. This system shows interesting perspective for combining different optical fiber devices, in order to achieve simultaneous detection and discrimination of temperature and strain.