Simultaneous generation of ultra-wideband LFM and phase-coded LFM microwave waveforms based on an improved frequency-sweeping OEO

Simultaneous generation of linear frequency-modulated (LFM) and phase-coded LFM microwave waveform with a large time-bandwidth-product (TBWP) based on an improved frequency-sweeping optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The key significance of the frequency-sweeping OEO is that a near-zero-dispersion single-mode-fiber (SMF) is introduced into the loop, which can not only avoid the limitation of high frequency oscillation caused by dispersion, but also construct long OEO delay loop to realize large temporal duration. A fiber-Bragg-grating Fabry–Perot (FBG-FP) with large reflection bandwidth is also adopted to construct microwave photonic filter (MPF) with wide tuning range of central frequency. Thus, the limitations on temporal duration and oscillation frequency are solved and a LFM microwave waveform with large TBWP can be generated. Simultaneously, by modulating the optical sideband from the MPF and beating the phase-modulated signal with a portion of frequency-sweeping laser light, a phase-coded LFM microwave waveform can be generated. In the experimental demonstration, a LFM microwave waveform with a chirp rate of 0.736 GHz∕μs and a large TBWP of 173,856 is generated, and reconfiguring central frequency and bandwidth is also completed. Simultaneously, a phase-coded LFM microwave waveform with a bandwidth of 8 GHz and a TBWP of 173,856 is also experimentally demonstrated.