Multiband Microwave Photonic Filters with Tunability and Programmability via Optical Frequency Comb Shaping

We present the development of tunable programmable multiband microwave photonic filters with an arbitrary number of passbands, which open a new route to integrate several communication function modules into one multifunctional communication terminal. The complex coefficient multi-tap microwave photonic filters providing flexible multiband filter characteristics can be realized by programming the amplitude and phase of dual optical frequency combs via a line-by-line optical pulse shaper in an interferometric scheme. Since the microwave photonic link implemented with an electro-optic optical frequency comb offers outstanding noise characteristics, robustness, and flexibility in the filter response, we apply the combs as a multi-tap optical source in the microwave photonic filters. We experimentally implement microwave photonic filters containing four passbands with a tunable center frequency up to 43.9 GHz and programmable bandwidth of up to 3.5 GHz at 3 dB. The number of passbands is set by the number of continuous wave lasers and linear phases applied to the corresponding shaped comb windows, while the tuning and programming of passbands are implemented by changing the coefficient of linear phase and Gaussian window via optical pulse shapers.