A Band-Folding Microwave Photonic Link With Inter-Band Image Rejection

We present a novel continuous-time microwave photonic link that translates eight contiguous folding bandwidths (FBW) to a single intermediate frequency (IF) bandwidth, with real-time discrimination of signals that are imaged or folded upon one another. A remote phase modulator imparts the source bandwidth of interest (BOI) onto the optical carrier, and one modulator of a dual-parallel Mach-Zehnder modulator (DPMZM) at the receiver imparts two local oscillator (LO) tones in parallel with the BOI. Third-order intermodulation distortion (IMD) between the LOs generates two more LOs, giving four LOs with eight FBWs downconverting to the IF band. A Hartley-type image rejection scheme discriminates between the upper and lower sideband images around each LO. Analysis shows the effects of different bias combinations or errors upon image rejection. Experimental results show up to at least 35dB of folded image rejection across 4GHz of original spectrum and the system successfully demodulated 64QAM signals, with almost no degradation, in the presence of a folded-image interferer.