Fiber optic temperature sensor utilizing thin PMF based Sagnac loop

Abstract A fiber optic temperature sensor utilizing a thin polarization maintaining fiber (PMF) based Sagnac loop is proposed and experimentally demonstrated. A Sagnac loop consisting of a thin PMF has a large fringe visibility of up to 46.16 dB. Except polarization eigen modes, cladding modes are excited owing to fiber mismatch to enhance the temperature sensitivity. The resonant dips of the wavelength spectrum are utilized to investigate the temperature characteristics. Experimental results show that the excited cladding modes in the thin PMF can improve the sensitivity. The temperature sensitivity of the sensor is enhanced by exciting more cladding modes, and it reaches as high as -1.55 nm/°C and the corresponding linearity is 99.96%. The sensor is anticipated to has promising prospects in temperature measurement for harsh environment.