Improved layer peeling algorithm to realize FBG non-uniform strain sense demodulation

Layer peeling algorithm is a common method of fiber Bragg grating(FBG) parameter reconstruction, which can be used to demodulate the inhomogeneous strain applying on FBG. The study found that conventional layer peeling algorithm cannot figure out the exact value of complex coupling coefficient, to increase the non-uniform strain demodulation precision, a improved layer peeling algorithm called complex coupling coefficient amplitude correction method was proposed. The improved method retained the phase of coupling coefficient, corrected the amplitude of coupling coefficient, and used the modified complex coupling coefficient on layer peeling calculation of the reflection spectrum. The following 4 reflection spectrums of FBG were obtained by the transfer matrix simulating method: without strain, strain increasing linearly, strain decreasing linearly and strain of quadratic curve, the strain results were calculated by both the conventional method and the improved method. The experiment shows that the strain results of the improved method are consistent with the input strain; With different theoretical strains, mean of the largest error of improved method is about 1/5 of conventional method, the mean of root mean square error is about 1/7 of the conventional one, the error is obviously much smaller.