Application of gain flattening filters in Erbium-doped fiber source

The output spectrum of Erbium-doped fiber source has two unsymmetrical peaks.The application of fiber source usually requires flat gain.Based on the gain flattening technologies of erbium doped fiber amplifier(EDFA),the working principle and its characteristics of several gain flattening filters were discussed.They were dielectric thin film filters,fiber gratings filters,Mach-Zehnder interferometer filters,photonic crystal fiber grating filters and high birefringence fiber loop mirror filters.The paper pointed out that the long-period fiber gratings and the dielectric thin film filters are currently proper filters for fiber source.In the end,the gain flattening experiments of C-band fiber source based on dielectric thin film filter were showed.The output performances of fiber source before and after filtering were given and analyzed.The results show that gain flattened spectrum of fiber source is obtained using filter.