Fiber Grating Sensor Signal Demodulation Technique

In this paper, we mainly used both interferometric demodulation technique and a matched grating-pair demodulation technique for demodulating the wavelength-coded signal of the fiber Bragg grating sensor element.Within the interferometric demodulation scheme, an unbalance wavelength scanning Michelson interferometer was introduced to transpose the strain induced wavelength-shifts signal into phase-shifts signal. With a phase-meter, the measured strain can be achieved by monitoring the value of the phase-shifts. The sensing resolution of this fiber Bragg grating sensor system was demonstrated to be 5.5 ne, to our knowledge, which is the highest one. The sensing sensitivity of this system was observed to be 1.80 Deg/ns experimentally.A tunable reference grating was employed in the matched grating-pair demodulation approach. The value of the measured strain can be judged by observing the maximum value of the reflected power of the system and the corresponding flexibility of the employed cantilever beam. Experiment demonstrated that the sensing resolution of this system is 8.2 ue , sensing sensitivity is 5.34 um/ue. This flexible scheme is desired and simple, it is a more perfect demodulation technique.