Large-band periodic filters for DWDM using multiple-superimposed fiber Bragg gratings

The tight specifications of dense wavelength division multiplexing (DWDM) filters are challenging for any available technologies. In this letter, periodic transmission filters based on superimposed chirped fiber Bragg gratings are designed to have flat amplitude response and nearly constant in-band group delay. These filters should prove to be useful as interleavers and mux/demux filters in DWDM systems.