A new kind of MZM and EDF-loop based flat microwave photonic filter

A new microwave photonic filter (MPF) hybrid of MZM and fiber loop that can realize both multiple taps and flat response is presented. Based on the phase character of Mach-Zehnder modulator (MZM) and the fiber loop with some length of erbium-doped fiber (EDF), a two taps finite impulse response (FIR) filter and a high Q filter are got respectively. Combining the two filters, the flat bandpass or bandstop response is realized by changing the coupler´s factor k or the gain of the EDF g . Optimizing the system parameters, a flat bandpass response with amplitude depth being more than 40dB is got at k1 = 0.5, k3 = 0.4, g = 2 and a flat bandstop response is also obtained at k1 = 0.4, k3 = 0.5, g = 2.