Widely Tunable Single Bandpass Microwave Photonic Filter Based on Phase Modulation and Stimulated Brillouin Scattering

We propose and demonstrate a widely tunable single bandpass microwave photonic filter (MPF) based on phase modulation (PM) and stimulated Brillouin scattering (SBS). The operation principle of the filter is based on the concept of using the Brillouin selective sideband amplification to achieve effective PM to amplitude modulation (AM) conversion. Only when one of the phase modulated sidebands lies in the SBS gain spectrum, can PM-to-AM conversion occur and the corresponding PM frequency be detected. Whereas the phase modulated sidebands lie out of the SBS gain spectrum, there is no RF signal obtained due to the -phase difference. As a result, a bandpass filter centered at a special frequency can be achieved. By adjustment of the Brillouin pump wavelength, tunable single bandpass MPF can be obtained. In the experiment, a microwave photonic filter with narrow bandwidth of about 35 MHz and a tuning range of 20 GHz has been obtained.