Single bandpass microwave photonic filter based on weak optical injection

Strong optical injection into a distributed feedback (DFB) semiconductor is a method to realize a single bandpass microwave photonic filter (MPF). But the out of band suppression ratio (OSSR) is limited by the four wave mixing (FWM) effect, and the 3 dB bandwidth is too large for microwave signals. To improve the OSSR and narrow the 3 dB bandwidth of the MPF, a novel single bandpss MPF based on weak optical injection is proposed and demonstrated in this paper. Experiment results shown that reduce the optical injection power can eliminate the FWM effect and improve the OSSR and narrow the 3 dB bandwidth of the MPF. In addition, reduce the power of a microwave sinusoidal signal which come from the vector network analyser (VNA) can also narrow the 3 dB bandwidth of the MPF.