Low Cutoff Optical Fiber and Cable Slack Management Scheme for Co-Packaged Optics in the O-Band

In current data-center switches, external fiber-optic connections are terminated in pluggable transceivers at the faceplate of the housing. The signals within the switch are transported electrically via copper traces on printed circuit boards. With increasing data rates, these electrical connections are becoming progressively more lossy, and increasing the electrical power to compensate for this loss negatively impacts the operational cost, electric power infrastructure, and waste heat management. To address these problems, the industry is envisioning placing the transceivers inside the housing very close to where the signals are generated: co-packaged with the switch ASIC. This approach effectively replaces the high-loss copper lanes with low-loss optical-fiber. However, to achieve this low-loss optical connectivity, the optical fibers must be single-mode for short similar to 0.5 m application lengths to avoid introducing signal impairments due to multi-path interference. It is also desirable that these fibers have good bend performance and mode-field diameters compatible with the installed base of single-mode fiber. In this paper, we will summarize the design of a new fiber optimized for these co-packaged applications and present data on developmental prototypes that demonstrates their suitability for use in short- length optical interconnects. We will also present a novel concept for management of the hundreds to thousands of fibers within the switch housing in which variable lengths of cable are neatly secured inside stackable accumulators. This tailoring of the length for each cable path results in no cable crossovers and will thus facilitate lower-cost and less error-prone assembly and easier maintenance of the switch.