[Measurement of refractive index with a PM-LPG based Sagnac loop sensor].

By inscribing a long-period fiber grating(LPG) on a polarization-maintaining fiber(PMF),a fiber Sagnac loop sensor for simultaneous measurement of refractive index and temperature has been proposed and demonstrated.The LPG was fabricated on the PMF by using a CO2 laser,and then inserted into a fiber loop formed by using a normal single-mode fiber coupler.One of the transmission minimum of the Sagnac loop sensor was measured,whose wavelength varied with temperature and the intensity changed with refractive index.Temperature sensitivity of-0.654 nm·℃-1 and refractive sensitivity of 49.9 dB·RIU-1 have been achieved.The sensor system shows advantages of small size and low cost,and owns a good application prospect.