A Tunable Microwave Photonic Filter Based on an All-Optical Differentiator

A tunable microwave photonic filter with complex coefficients is presented. The complex coefficient is generated using an all-optical radio-frequency (RF) phase shifter, which contains an optical differentiator to realize phase modulation to intensity modulation conversion. The phase of the RF signal can be tuned continuously by simply controlling the optical power through changing variable optical attenuators. A two-tap tunable filter with one complex coefficient is experimentally demonstrated and a continuous tuning range of a half free spectral range is realized without changing the shape of the frequency response.