Study of chirped fiber Bragg gratings apodized with different apodization length ratios

Symmetrical apodization technique of the chirped fiber Bragg grating has the advantages of suppressing the sidelobes of reflection spectra and smoothing the curves of group delay. However, it shortens the bandwidth of the reflection spectrum markedly. Compared with symmetrical apodization method, the asymmetric method can increase the 3dB bandwidth by 64.08% without the change of group delay curves. The apodization simulation is implemented by using a rised cosine function with different apodization length ratios at both ends of the grating. There is a compromise between the bandwidth and the group delay ripple. The result shows that the grating with 30% apodization at the long wavelength end and 20% apodization at the short wavelength side can improve the reflection bandwidth effectively and depress the group delay ripple within the range of +/- 2 ps.