All-Optical Multiorder Distortion Elimination in a Phase-Modulated Microwave Photonic Link

We experimentally demonstrate an all-optical architecture for the linearization of a phase-modulated interferometrically detected microwave photonic link. We couple off a small part of the phase-modulated signal and combine it with a pump lightwave to produce a comb of idlers in a cascaded four-wave mixing process. The phase-matching requirement of the cascaded process ensures that integer multiples of the original signal's temporal phase modulate each of the idlers. We accomplish the linearization by filtering, scaling, and recombining a subset of the idlers. To the best of our knowledge, this is the first demonstration of a simultaneous third-order, fifth-order, and all even-order distortion free links in either intensity or phase-modulated architectures. We experimentally measure a 108.8-dB SFDR for the conventional link, 116.1 dB for the third-order distortion-free link, and 116.9 dB for the third-order and fifth-order distortion-free links, each in a 1-Hz bandwidth. We show that the experimentally measured SFDR improvement is primarily limited by an increased phase noise on the correction lightwaves. Specifically, we measure a 24.2-dB noise figure for the conventional link, 38.7 dB for the third-order distortion-free link, and 45 dB for the third-order and fifth-order distortion-free links. We discuss the source of this added noise and methods for mitigation in the future work, which could lead to a 134.8-dB SFDR in a 1-Hz bandwidth for a shot noise limited link with ~1 mA per photodiode.