Performance of high-speed reconfigurable free-space card-to-card optical interconnects under air turbulence

Free-space based optical interconnects are promising candidates for the prevision of parallel, high-speed, densely integrated and reconfigurable card-to-card interconnectivities in data centers and for high-performance computing clusters. However, air turbulence due to high temperature of electronic components and heat dissipation fans typically results in degradation of system performance through effects such as signal scintillation, beam broadening and beam wander. In this paper, the impact of air turbulence on our recently proposed reconfigurable free-space card-to-card optical interconnect scheme is investigated. Experiments are carried out with lab-emulated moderate and comparatively strong turbulence and results show that the bit-error-rate (BER) performance of proposed interconnect scheme is degraded. A power penalty of ∼ 0.5 dB is observed at BER of 10-9 in emulated moderate turbulence, and in emulated comparatively strong turbulence the BER performance suffers power penalties of ∼ 1.6 dB. It should be noted that a BER of 10-9 is not sufficient for typical card-to-card optical interconnects and FEC should be employed to improve the BER performance at the cost of some overhead. Nevertheless, experimental results show that our proposed 3×,3 10 Gb/s reconfigurable optical interconnects with card-to-card spacing of up to 30 cm is still achieved even under considerably strong turbulence.