VCSEL-Based Light Sources—Scalability Challenges for VCSEL-Based Multi-100- Gb/s Systems

Future high-performance computers require optical interconnects with aggregated Exa-Byte/s data transport. Densely packed arrays of vertical-cavity surface-emitting lasers (VCSELs) might present the only feasible technical solution. The high-speed properties of semiconductor lasers, however, are strongly affected by their operating temperature. Thermal crosstalk becomes dominant when densely packed arrays of high-speed VCSELs are required. In this paper, we derive the maximum bandwidth of future VCSEL-based optical interconnects from the influence of device heating occurring in high-speed VCSEL arrays. Furthermore, we estimate the scalability of this technology and address the challenges. From our calculations we obtain, that VCSEL arrays are scalable from a bandwidth density of 100 Gbps/mm² with today's devices up to a technological limit of 15 Tbps/mm².