Simultaneous four-channel thermal adaptation of polarization insensitive silicon photonics WDM receiver.

We propose a novel approach to demonstrate simultaneous multi-wavelength locking during temperature changes in a silicon photonic polarization insensitive microring-based wavelength division multiplexing (WDM) receiver. The DC component of a single monitoring photodetector at the through port of the microring filter array is exploited as a feedback signal with no additional power consumption. This feedback signal is used in control circuitry to properly tune the microring filters using ohmic heating, thus creating a feedback loop for thermal adaptation. We describe the necessary information, specifically each microring filter's room temperature resonant wavelength and tunability, which can be used to calibrate and achieve proper wavelength configurability and locking. In addition, we describe a simple control algorithm based on an adaptive gradient method often used in machine learning, allowing the receiver to endlessly demultiplex at different temperatures. We successfully achieve thermal adaptation over a temperature range >37°C and demultiplex a 4 × 25 Gb/s on-off-keying signal of 150 GHz channel spacing, all while the polarization is scrambling.