“…Moreover, FBG has many changeable structural parameters, such as period, apodization function, length and chirp, which make it more flexible for spectral shaping. Some inverse engineering algorithms, including Fourier transform method based on first-order Born approximation [12,13], solving Gel'fand-Levitan-Marchenko (GLM) integral equation [14], layer-peeling method [15] and genetic algorithm [16] and so on, have also been known and they can be implemented to obtain easily the eminent design of complex FBG.…”