A Silicon Microring Optical 2 $\times$ 2 Switch Exploiting Orbital Angular Momentum for Interconnection Networks up to 20 Gbaud

The orbital angular momentum (OAM) of light can be exploited as an additional switching domain together with more traditional switching domains as wavelength, space, and time to implement multilayer interconnection networks with high capacity, low power consumption, and fast reconfiguration time. In this study, we propose a two-layer optical interconnection network exploiting OAM and wavelength as switching domains. The key component of the interconnection network is the OAM-based switching element, here implemented on a silicon-on-insulator chip exploiting microrings. This implementation allows fast tuning (down to nanosecond range) and low power consumption (a few tens of milliwatt per microring). We report the first implementation of an OAM-based 2 × 2 switch exploiting a dual-grating microring. The measurements are taken for OOK and 16QAM input signals modulated up to 35 Gbaud. A bit error rate below the forward error correction threshold is demonstrated up to 20 Gbaud for all the switching scenarios, with power penalty <; 1 dB with respect to the back-to-back. A characterization of the integrated microring is carried out also in terms of beam divergence for different radii and emitted OAM orders. The characterization has brought to an empirical model, which can aid the microring design in order to optimize the collimation of the OAM beams through the interconnection network.