A Demodulation Scheme for High-sensitivity Temperature Sensing Based on Long Period Fiber Grating

Long Period Fiber Grating (LPFG) sensors have wide range of potential applications; low-cost and high-sensitivity demodulation technology is the key of its practical applications. In this paper, an interferometer is comprised of an all-fiber loop mirror and two identical LPFGs, a tunable F-P filter is used to perform wavelength scanning one of the interference peaks, two negative pulse interval formed by signal light in the drive signal period are measured by means of detector and oscilloscope to realize signal demodulation. This demodulation system was used to detect the temperature parameter. The results showed that the sensing sensitivity of this system was demonstrated to be 0.08349 ms/degrees C, experimentally, which was 2.3 times higher than a single LPFG using the same demodulation technology.