All-optical microwave bandpass filter with negative coefficients based on PM-IM conversion

A novel technique for obtaining negative coefficients for the implementation of all-optical microwave bandpass filters is presented. In the proposed approach, the negative coefficients are obtained by locating the optical carriers at the opposite slopes of the transfer function of an optical filter, to convert the phase-modulated signal to intensity-modulated signal, with phase inversion of the radio-frequency modulating signals. A two-tap microwave bandpass filter with negative coefficients is demonstrated.