Tunable single passband microwave photonic filter based on DFB-SOA-assisted optical carrier recovery

A tunable single passband microwave photonic filter (MPF) based on a distributed-feedback semiconductor optical amplifier (DFB-SOA) is proposed and experimentally demonstrated in this paper. The fundamental principle is to recover the suppressed optical carrier from a passband optical filter by the wavelength-selective amplification of the DFB-SOA. A microwave signal is then generated by beating the recovered optical carrier with the phase modulated lower sideband and thus a MPF is achieved with the shape of the passband optical filter which is mapped from optical domain to electrical domain. By tuning the central wavelength of the passband optical filter, a single passband MPF with frequency tuning range from 5 to 35 GHz is obtained. The 3-dB bandwidth and the out-of-band suppression ratio are measured to be 4 GHz and 20 dB, respectively.