Research and optimization of FBG apodization technic based on Double-exposure method

The reflection spectral influence of fiber Bragg gratings (FBG) caused by refractive index of DC component was analyzed. FBG with double exposure apodized by raised cosine beam, was found the best way to eliminate reflection sidelobe among three beams (raised-cosine, Gaussian and cosine beam).Through adjusting Full Width Half Maximum (FWHM) parameter in the best double-exposure apodising function, the optimal apodising function was obtained with its sidelobe suppression value 35dB.