Integrated photonics approach to radio-frequency self-interference cancellation

Abstract

An integrated photonics based scheme for radio-frequency self-interference cancellation is proposed and demonstrated. It is achieved using a dual-parallel Mach-Zehnder modulator that eliminates the interference signal in the optical domain. The output of the modulator is a carrier suppressed double-sideband waveform that contains only the signal of interest. Finally, the signal of interest is recovered by combining the modulator output with a local optical carrier and detecting it at a high-speed photodetector. We present a detailed theoretical analysis and derive the optimal condition for self-interference cancellation for small modulation indices. The modulators were designed and fabricated on IMEC’s Silicon-on-Insulator iSiPP50G platform. Using this technique, we experimentally obtain a cancellation depth of 30 dB and a signal to interference ratio of 25 dB for frequencies up to 20 GHz, limited only by the equipment used. This is the first demonstration of self-interference cancellation on a silicon photonics platform and a further expansion of the functionalities offered by integrated microwave photonics.