Photonic generation of background-free binary phase-coded microwave pulses.

We report a photonic scheme to generate background-free frequency-doubled binary phase-coded microwave pulses. The key component is a dual-polarization dual-parallel Mach-Zehnder modulator that is used to realize phase modulation and carrier-suppressed double second-order sideband modulation at two orthogonal polarization states, respectively. The π phase jump of the frequency-doubled phase-coded microwave pulse is dependent on the polarity of the coding signal rather than its amplitude. Besides, the generated microwave pulses are free from the baseband-modulated signals, because the optical power launched to a photodetector (PD) keeps constant all the time. Since no electrical or optical filters are involved, the photonic generator can ensure a broad operation bandwidth and wide tunability. Our scheme is theoretically analyzed and experimentally verified. The 4 Gb/s at 16 GHz and 7 Gb/s at 28 GHz background-free frequency-doubled phase-coded microwave pulses have been successfully generated.