Distortion-tolerated high-speed FBG demodulation method using temporal response of high-gain photodetector

A distortion-tolerated fiber Bragg grating (FBG) demodulation method for high-gain or high-speed sensing is proposed. The temporal response of photodetector (PD) on FBG reflection spectrum for different electric gains and wavelength scanning frequencies is investigated theoretically and experimentally. Simulation results show that high electric gains and high wavelength scanning frequencies will induce a tailed distortion on the right side of the FBG reflection peak output by the PD. A temporal response function of PD is presented to fit the peak with distortion and determine the peak position on FBG reflection spectrum. Experiments with varying degrees of FBG acquisition distortion are carried out. Compared with the traditional Gaussian fitting method, the measurement error of the temporal-response based method is limited within ±1.777 pm and the standard deviation is less than 0.940 pm, which are respectively improved by 6.87 times and 4.38 times at least.