EDFA gain flattening using phase-shifted long-period grating

The design of an erbium-doped fiber amplifier (EDFA) gain-flattening fiber filter, based on a cascade of phase-shifted long-period grating (LPG), and normal LPG, was presented. The phase-shifted LPG were written by using two kinds of techniques such that the amplitude mask technique and UV post-exposure technique. The results showed that the 3-dB bandwidth of the flattened EDFA was increased to 46 nm from 18 nm for an unequalized spectrum and the gain ripple over that bandwidth was reduced to 0.9 dB.