A Fiber Bragg Grating Sensing System Using Tunable Demodulator

This paper presents a novel sensing system that enhances the measurability of the strain applied to a fiber Bragg grating (FBG) sensor by exploiting a tunable demodulator (TD). The system is simple and composed of a broadband light source (BLS), a circulator, an FBG sensor, and a TD. The light from the BLS is first fed into the FBG sensor through the circulator. Then, a portion of the incident light will be reflected and transmitted to the TD through the same circulator. Depending on the strain applied to the FBG sensor, the reflected light will experience a corresponding shift in its wavelength and variation in its power. Through the experiment, this study discovered and demonstrated that the power of the reflected light can be adjusted by the TD. Hence, for a fixed strain on the FBG sensor, the power variation in the reflected light can be maximized by tuning the TD properly. In this way, the power resolution of the FBG sensor can be equivalently improved.