Microwave Photonic Time-Frequency Analysis Based on Period-One Oscillation and Phase-Shifted Fiber Bragg Grating

A low-cost and simplified microwave photonic time-frequency analysis (TFA) scheme based on period-one (P1) oscillation in a semiconductor laser and phase-shifted fiber Bragg grating (PS-FBG) is proposed. A high-speed and wideband linear frequency-sweep optical signal is generated using a semiconductor laser operating in the P1 oscillation state and then modulated at a Mach-Zehnder modulator by the electrical signal under test (SUT). The ultranarrow transmission peak in the notch of the transmission spectrum of a PS-FBG is used as a bandpass filter to implement the frequency-to-time mapping (FTTM) of the signal. The optical signal from the PS-FBG is converted to electrical pulses through low-speed photodetection and further processed to obtain the time-frequency information of the SUT. Since high-frequency electrical signals and a complicated pump-probe structure are not used, the system exhibits significantly reduced cost and complexity in comparison to the reported approaches. TFA of various RF signals is experimentally performed within a 10-GHz bandwidth.