Photonic Generation of a Phase-Coded Chirp Microwave Waveform With Increased TBWP

Photonic generation of a phase-coded chirped microwave waveform with an increased time bandwidth product (TBWP) using a frequency-tunable optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The frequency-tunable OEO is implemented using a tunable laser source (TLS), a phase modulator (PM), a phase-shifted fiber Bragg grating, and a photodetector (PD), with the frequency tuning realized by tuning the wavelength of the TLS. A frequency-tunable optical sideband with a frequency that is equal to that of the optical carrier plus the OEO oscillation frequency is generated by the OEO, which is then orthogonally polarization multiplexed with the optical carrier from the TLS at a polarization beam combiner, and applied to a polarization modulator, to which a binary phase-coded parabolic electrical signal is applied. By beating the two orthogonally polarized optical signals at a PD, a phase-coded chirped microwave waveform is generated. The TBWP is significantly increased due to the increase of the temporal duration of the microwave waveform. The proposed approach is experimentally demonstrated. Two phase-coded chirped microwave waveforms with TBWPs of 58.5 and 80 000 using two phase coding signals corresponding to a 13 Barker code and a 20480-bit pseudorandom sequence are generated.