Switchable and Tunable Microwave Photonic Brillouin-Based Filter

A new structure that realizes a switchable microwave photonic filter, which can be readily switched between a bandpass filter and a notch filter, is presented. It is based on optical processing the sidebands of the RF-modulated signal that is obtained after a dual-drive Mach-Zehnder modulator (DDMZM), using stimulated Brillouin scattering (SBS) effects. Switching of the filter function is simply and conveniently obtained by changing the dc bias to the DDMZM. In addition, the center frequency of the switchable filter can be tuned over a wide frequency range. A detailed analysis and simulation of the DDMZM operation in conjunction with the SBS technique is presented in order to obtain the required optimum bias conditions for the DDMZM for realizing the switching action between the single-band-pass filter and the notch filter and also to select the optimum pump power for the SBS operation. Experimental results demonstrate the ability of this structure to switch between a high-resolution bandpass filter and a high-resolution notch filter, with Q values around 400-500, and the ability to operate over a frequency range of 2-20 GHz.