Research on fiber grating sensing characters using fiber cavity ring down demodulation technique

An exploratory study on the temperature and strain sensor based on weak long period grating (LPG) and fiber ring is presented. This fiber ring-down (FRD) device consists of two matched fiber Bragg gratings, a section of single mode fiber, a weak long period grating, a pulsed laser source and a photodiode. The weak long period grating inserted in fiber ring cavity is used as sensing element which will cause additional loss is cavity. By measuring the fiber ring-down time in time domain, the temperature (0-100°C) and strain (0-l000με) sensing characteristics on weak long period grating are achieved. The demodulation wavelength range is 10 nm.