Apodization of Fiber Bragg Grating Based on Moiré Effect

The changes of reflection spectrum and dispersion of fiber Bragg grating (FBG) apodized by moire effect are analyzed theoretically. It is pointed that the apodization of the fiber grating by using Moire effect is a pure apodization because the Moire effect makes the index modulation amplitude in both positive and negative sides and keeps the average index unchanged. However, there exist some side lobes in short wavelength side of Bragg peak when the fiber Bragg grating was apodized by conventional raise cosine function because of the F-P effect. Experimentally apodized FBG by using Moire effect was obtained with a side mode suppression 6 dB better than conventional FBG without apodization.