Photonic generation of tunable wideband dual-chirp microwave waveform using frequency-scanning laser and polarization division multiplexing modulator

A photonic approach to generate tunable wideband dual-chirp microwave waveform (DCMW) using frequency-scanning (FS) laser and polarization division multiplexing (PDM) modulator is proposed and demonstrated. In the scheme, an optical signal from the FS laser is modulated by radio-frequency (RF) driving signals through a PDM modulator Then the modulated signal is sent to a polarization controller followed by a polarization delay module to obtain orthogonally polarized second-order sidebands and carrier with time delay. Finally, a tunable wideband DCMW can be generated after photoelectric balanced detection. In the simulation experiments, DCMW with central frequency of 30 GHz and bandwidth of 14 GHz is generated and its ambiguity function is investigated. Meanwhile, the influences of several non-ideal factors, such as the finite extinction ratio and direct-current bias drift of the PDM modulator, phase difference error between two RF driving signals, on the system performance are evaluated. Moreover, the tunability of the generated DCMW is also verified by simulation.