Spectrum-Sliced Microwave-Photonic Filter Based on Fourier Transform of Modified Optical Spectrum

A new technique is presented to reconfigure the dispersion-induced RF fading in a spectrum-sliced microwave photonic filter to an arbitrary spectral shape, including the flat-top response with rectangular shape and operating frequencies beyond conventional baseband. The technique is based on the Fourier transform of the modified optical source power spectrum, which is realized by applying a designed optical amplitude and phase manipulation using a diffraction-based spectral pulse shaper to the ports of a dual-output Mach-Zehnder electro-optic modulator in combination with a broadband light source. This scheme is fundamentally different from earlier finite-impulse-response-based spectrum-sliced microwave-photonic filters that require specific slicing elements for optical taps, but offers the same flexibility in realizing various filter passband characteristics with the added benefit of widely shape-invariant tuning and a single passband response. Experimental results verify the technique and demonstrate a continuously tunable dispersion-induced RF fading up to 20 GHz, exhibiting shape invariance and a flat-top response.