Self-Stabilized 50 Gb/s Silicon Photonic Microring Modulator Using a Power-Independent and Calibration-Free Control Loop

This paper demonstrates the possibility of automatically stabilizing the working condition of an integrated Silicon Photonics microring modulator with a novel dithering-based control scheme. The proposed feedback strategy leverages a realtime acquisition of the modulator non-linear transfer function (TF) and operates by setting the target locking point to the zero of the TF second derivative, i.e. where the ring slope is maximum. This results in a control algorithm that is both power-independent and calibration-free. The paper shows that the operating point identified in this way has a negligible difference with respect to the optimum working condition of minimum Transmitter Penalty normally targeted and that the employed dithering signal does not affect the modulation quality. The control performances, made possible by an FPGA-based platform ensuring a 30 ms response time, are assessed in a 50 Gbit/s routing scenario, demonstrating effective compensation of wavelength and thermal variations and successful transmission even in demanding environments.