Tunable multitap microwave photonic filter with all complex coefficients.

Architecture for the implementation of a tunable multitap microwave photonic filter (MPF) with all complex coefficients is proposed and demonstrated. The complex coefficients are realized by 360° tunable photonic microwave phase shifters based on single-sideband polarization modulation. The polarization modulator, wavelength-division multiplexers, polarizer, and photodetector required for achieving the tunable phase shift are shared by all taps. Only a polarization controller is required in each tap to adjust each phase shift independently, making the system simple and compact. A proof-of-concept experiment is performed. A four-tap MPF with full free spectral range tunability and adjustable filter shape is realized.