Nonuniformly spaced photonic microwave delay-line filter using a spatially discrete chirped fiber Bragg grating

A new technique to implement a nonuniformly-spaced photonic microwave delay-line filter using a spatially discrete chirped fiber Bragg grating (SD-CFBG) is proposed and investigated. It is different from a regular nonuniformly-spaced photonic microwave delay-line filter where a laser array with nonuniformly spaced wavelengths is used to provide nonuniformly-spaced filter taps, the proposed method employs a single incoherent broadband optical source. The SD-CFBG is acting as a multifunctional device, to slice the broadband spectrum to generate the required filter taps, to provide nonuniform time delays to the taps, and to tailor the weights of the filter taps. By properly designing the spectral response of the SD-CFBG, a photonic microwave delay-line filter with arbitrary magnitude and phase response can be implemented. Based on this concept, a nonuniformly-spaced photonic microwave delay-line filter with a flat-top bandpass magnitude response and a quadratic phase response is designed and analyzed. The use of the designed filter for chirped microwave pulse compression is investigated.