Experimental Demonstration of 4-Port Photonic Reservoir Computing for Equalization of 4 and 16 QAM Signals

Abstract

We experimentally demonstrate the application of a passive 16-node photonic reservoir for analogue, hardware-based equalization of coherently modulated signals at 28 Gbaud. This integrated photonic network, termed the 4-port reservoir, replaces computationally expensive digital signal processing (DSP) procedures for both fiber impairment equalization, including chromatic dispersion, as well as for transceiver imbalance equalization. For full mitigation of transmission impairments, our photonic solution can seamlessly integrate with DSP blocks for frequency offset compensation and blind phase search, achieving bit error rates on-par with the legacy DSP blocks it replaces. The same reservoir is shown to successfully equalize both 4 and 16 QAM signals in a range of linear and nonlinear transmissions.