WDM-Based Silicon Photonic Multi-Socket Interconnect Architecture With Automated Wavelength and Thermal Drift Compensation

Abstract

A silicon photonic circuit comprising all the building blocks necessary to demonstrate optical communication between two sockets interconnected through an Arrayed Waveguide Grating Router is reported. The paper focuses on the robustness of the interconnection scheme to the unavoidable wavelength and thermal fluctuations observed in real datacenter environments. To improve the reliability of the system, a feedback control mechanism, based on ContactLess Integrated Photonic Probes and heater actuators, is added to the interconnection to monitor in parallel the working point of each sensitive device and keep it locked in real-time. Experimental results demonstrate successful operations in a 30 Gbit/s data routing scenario at 5 • 10 −11 bit error rate, irrespective of sudden wavelength shifts of up to 200 pm or of iterated thermal variations in a 10°C temperature range, with a recovery time of around 30 ms. These results prove that AWGR-based interconnections equipped with real-time drift compensation systems can be a viable option in multi-socket layouts even in highly demanding environments. Index Terms-Silicon photonics, thermal drift compensation, CLIPP sensor, wavelength division multiplexing, AWGR-based interconnect I. INTRODUCTIONWith the demand for data traffic capacity in intra datacenter applications roughly doubling every year [1], novel techniques must be developed to cope with traffic growth. Two key problems that arise when scaling up capacity are the increased power consumption of the processors and the latency in the communication between them. These problems have driven research interest on novel multi-socket-boards (MSB), that integrate several processor sockets on a single board interconnected with a low latency interface. Schemes as Intel's QPI [2] can offer glue-less interconnection but are limited to

Low-Noise Mixed-Signal Electronics for Closed-Loop Control of Complex Photonic Circuits

“…The effectiveness of this approach has been experimentally demonstrated on a photonic chip featuring all the necessary building blocks to demonstrate optical communication between two transmitting sockets and a receiving one (Fig. 4a) [22]. A 30 Gbit s −1 modulated laser signal was injected into the system and monitored at the output to obtain both eye diagrams and BER measurements, while a second laser served as a crosstalk source.…”

Zero-Change Monolithic Integration of CMOS Electronics in Silicon Photonics

“…A multiplexer is a key enabling component for the control of high density integrated photonic systems, where a high number of sensors and actuators are required to monitor and actively set the working point of each optical element. This feedback-based approach is mandatory to counteract the sensitivity of photonic devices to temperature variations and fabrication tolerances [23][24][25][26][27][28][29][30], that would otherwise make it impossible to operate optical architectures in thermally-unstable environments.…”

“…With this approach, the goal of electronics should not be high-speed processing but rather to ensure reliable optical operations, thus targeting accurate calibration, reconfiguration and robust stabilization of the photonic functionality against thermal instabilities. The control action is currently obtained by implementing a low-speed (sub-MHz range) electronic feedback loop for each photonic device, by means of external circuitry connected to on-chip light sensors and actuators [23][24][25][26][27][28][29][30][31].…”

Electronics-photonics co-design for robust control of optical devices in dense integrated photonic circuits

“…Complex photonic circuits usually made by combining elementary building blocks to obtain the desired optical functionality. One of the photonic components most commonly used to implement routers and filters [13,35] is the micro-ring resonator (Fig. 11a), a device able to steer the input light from one output port (THROUGH) to another (DROP) if the circumference length is an integer multiple of the wavelength, condition indicated as resonance.…”

“…By carefully co-designing the electronics and the photonics (Fig. 1), this interplay can be optimized to perform advanced operations like reconfigurable routing schemes [12], wavelength-division multiplexing (WDM) [13] or optical mode manipulation and unscrambling in mode division multiplexing (MDM) systems [14]. These achievements potentially allow a cost and size reduction of optical components and an improvement of the capacity of optical networks.…”