The increasing demands for emerging high-volume and latency-constrained applications, such as artificial intelligence, autonomous vehicles, and augmented/virtual reality, are imposing stringent requirements on data center network capacity, latency, energy consumption, and guaranteed delivery. Current data center interconnects with static node configurations are being pushed to their limits by the diverse demands of this set of applications. Flexible architectures that match their capacity to an application's traffic pattern can deliver optimized connectivity while eliminating over-provisioned resources. Transparent optical switches are the key enablers. However, as short-reach interconnects approach petabit-scale capacity with massively parallel wavelengths, switching at the wavelength granularity is becoming vital.
The multi-dimensional switch developed within PUNCH offers reconfigurable interconnects from all-to-all links, to imbalanced group-to-group traffic by bandwidth steering. A space-and-wavelength switch fabric forms the core for arbitrarily routing any combination of wavelengths from any input to any output. An extra key lies in the ultra-fast reconfigurability, which is a cornerstone that enables unparalleled dynamics by multiplexing in the time domain. The combination of photonic switching in the space, wavelength and time domains holds great promise for agile, adaptive, and deterministic data center networks.
To ensure low cost per port, optical switching technologies must demonstrate a path towards high-volume manufacturing. Silicon photonics has been identified as a key enabling technology, providing a high-level of integration and compatibility with CMOS processes. However, large-scale switch fabrics pose huge challenges in terms of optical and electrical packaging. Furthermore, insertion loss is limiting commercial uptake, motivating the integration of semiconductor optical amplifiers (SOA) to provide on-chip gain.
Within PUNCH, full thermal, electrical, and optical packaging solutions are incorporated, leveraging semiconductor packaging technology compatible with high-volume manufacturing. The development of a III-V foundry process for micro-transfer-printing compatible semiconductor optical amplifiers enables lossless optical switching on the silicon photonics platform. Custom designed electronic ICs to actuate, control, and power-monitor scaled switch fabrics are densely integrated with the photonic ICs into a heterogeneous fanout wafer-level package (FOWLP), processed on a 200 mm reconstructed wafer platform. In addition, the optical interfacing to the photonic ICs is accomplished using an optical redistribution layer, providing an optical fanout on organic IC-substrates, and allowing for a scalable optical fiber packaging solution.
The novel integration and packaging processes will also be applied for manufacturing optical transceivers providing the interface between optical switches and electronic resources (compute, memory, and storage). Finally, the optical switch and transceiver prototypes will be demonstrated in a 5G RAN Transport Network, for Time-Sensitive Networking Fronthaul applications and for memory disaggregation in data centers.
