New all-optical radio-frequency notch filters with frequency response equivalent to two-tap negative tap notch filters are presented. Two topologies are described, based on a dual-output electrooptic modulator that undergoes double-pass modulation, and whose phase difference of the modulated signals at the outputs are used to obtain equivalent negative tap behavior in the notch filter response. Results are presented for the novel structures, which demonstrate the realization of an equivalent negative tap notch filter response, and which also show the important advantages of eliminating coherence and phase noise limitations in the operation of the processors.
Chan, E. H. W., & Minasian, R. A. (2004). Novel all-optical RF notch filters with equivalent negative tap response. IEEE Photonics Technology Letters, 16(5), 1370-1372. https://doi.org/10.1109/LPT.2004.825982