Ultraflat Widely Tuned Single Bandpass Filter Based on Stimulated Brillouin Scattering

A novel ultraflat widely tunable single bandpass filter based on processing carrier-suppressed upper and lower sidebands separately and stimulated Brillouin scattering (SBS) is analyzed and presented. The microwave photonic filter features continuous and enhanced tunability via mapping the frequency change of RF oscillation doubly onto the central frequency shifting of the RF filter. Theoretical analysis shows the filter's magnitude response depends on modulation index of electro-optic modulator and SBS gain. Experimental results demonstrate a microwave photonic filter that has a single bandpass response, a narrow bandwidth of about 20.6 MHz, and a tuning range of 20 GHz with over 30-dB out-of-band rejection ratio and less than ±1.2-dB amplitude fluctuation during tuning.