Tunable and reconfigurable microwave photonic filter implemented by cascaded Mach-Zehnder modulators and a dispersive medium

Abstract

A novel tunable and reconfigurable microwave photonic filter based on two cascaded Mach-Zehnder modulators (MZMs) and a dispersive medium is presented, theoretically discussed and experimentally demonstrated. A single-wavelength laser diode (LD) and the first MZM are used to obtain a multi-wavelength optical source, and the second MZM is modulated with the signal to be processed. The dispersive medium provides the time delay for different taps, since different wavelength experiences different time delay, when it travels in the optical fiber. By adjusting the modulation frequency and the bias voltage on the first MZM, the wavelength spacing and the relative amplitude of the optical tones after the first MZM can be changed, thus making the filter tunable and reconfigurable. The presented microwave photonic filter has been implemented in the experiment. The experimental results agree well with the simulation results, and show that the present microwave photonic filter has good tunability and reconfigurability. The mainlobe-to-sidelobe ratio (MSR) of around 25dB is achieved for the presented filter in the experiment.