KEYWORDS: Digital signal processing, Design and modelling, Modulation, Receivers, Single mode fibers, Modulators, Vertical cavity surface emitting lasers, Data centers, Optical interconnects, Electronic design automation
Capacity demand for network connections within and between datacenters is increasing relentlessly, fueling the need for deployment of new and improved optical communications equipment. Confronted with the task of developing innovative solutions to address this challenge, engineers must deal with and consolidate countless design choices that are influenced by a large variety of constraints. To name just a few, an optimum solution may depend on technological requirements such as minimum data rate, maximum latency, electrical and optical bandwidth, link distance, upgradability (to higher speeds and/or other/more wavelengths), as well as the need to comply with standards and how these evolve. In this sense, automated design tools for simulating and comparing alternative solutions are indispensable. We present design examples at the system- and component-levels, illustrating the challenges in modeling, analyzing and optimizing technology choices and equipment parameters of optical interconnects for intra- and inter-datacenter applications. Of critical importance for tuning the performance of transceiver components is the integrated co-design of the corresponding electronic and optical parts. We demonstrate a seamless design flow linking simulations of the electronic circuits at the transmitter/receiver (such as serialization/deserialization, DAC/ADC, driver amplifier/TIA, etc.) with simulations of the optical fiber link, enabling investigation and optimization of the overall system performance. Further, we compare advantages and challenges of multimode infrastructure solutions utilizing, for instance, PAM4 modulation of multimode VCSELs with transmission over wide-bandwidth multimode fibers, and single-mode solutions employing Mach-Zehnder modulators with tunable DFB lasers in WDM operation over SMF-links.