Overcoming Tap-Delay-Variation Induced Distortion in Microwave Photonic Filters

A new technique to realize a multiple-tap microwave photonic Alter that is free of the limitations of tap-delay-variation induced Alter distortion, which enables it to operate at high microwave frequencies, is presented. It is based on a technique using a wideband high-order dispersion compensator to cancel the group delay variations of the primary optical fiber dispersive delay line. The compensator, implemented using a programmable Fourier-domain dynamic wavelength processor incorporating liquid crystal on silicon pixels, provides a tailored optical phase profile to effectively cancel out the tap-delay variations originating from the primary fiber delay line. Experimental results verify the new technique and demonstrate a 20-tap microwave photonic bandpass filter obtained using a multi-frequency laser source with equally spaced lines, which operates to 20 GHz without any radio frequency distortion.