Tunable multi-tap microwave photonic filter with complex coefficients using a dual-parallel Mach-Zehnder modulator

We propose and demonstrate a tunable multi-tap microwave photonic filter (MPF) with complex coefficients. It is based on addition of carrier suppressed single sideband (CS-SSB) signal and phase-controllable optical carrier. Instead of using the technique of optical filtering, the CS-SSB signal is generated by a dual-parallel Mach-Zehnder modulator (DPMZM) in our scheme. Frequency tuning of the filter is achieved by changing the phase of the optical carrier, which can be controlled by a variable optical delay line (VDL). The proposed structure features high flexibility and wideband RF response, and the experimental results demonstrate that it can be tuned continuously over one free spectral range (FSR) without changing the spectral shape of the filter.