On June 29, 2026, our research team, led by Professor Xingjun Wang and Researcher Haowen Shu, in collaboration with Peng Cheng Laboratory and Beijing Information Science and Technology University, published a research article entitled “Ultra-fast co-packaged optical wireless link for wireless-assisted data center interconnection” in PhotoniX. The researchers developed a four-channel optical wireless transceiver module based on 850 nm vertical-cavity surface-emitting lasers. Over a 0.5 m free-space link, the module achieved 160 Gb/s PAM-4 transmission per channel and an aggregate rate of 640 Gb/s across four channels, providing an experimental approach to short-reach data-center interconnection.
Servers, switching chips, and computing accelerators within data centers need to exchange large volumes of data. As equipment density increases, cabling, maintenance, and reconfiguration using copper cables and optical fibres become more complex. Optical wireless communication transfers information through free-space optical beams and can supplement some short-reach wired connections, but practical transmission rates are jointly limited by device bandwidth, packaging parasitics, channel variations, and nonlinear distortion.
Our research team designed the complete transceiver link. The transmitter uses a laser array and high-speed driver circuits, while the receiver combines a PIN photodetector array with transimpedance amplifiers; the two ends are connected through a free-space optical path. For the high-speed interfaces among the chips, bond wires, and printed circuit boards, the researchers established an equivalent model, optimized the transmission-line design, and adopted a dual-bond-wire structure to reduce equivalent interface inductance and improve impedance continuity and frequency response.
Figure 1. Schematic of the four-channel optical wireless interconnect and transceiver modules for data centers
Building on the hardware optimization, the study applied offline third-order Volterra nonlinear equalization to the acquired signals to compensate for intersymbol interference caused by bandwidth limitations and nonlinearities. At a transmission distance of 0.5 m, the module achieved 100 Gb/s non-return-to-zero (NRZ) and 160 Gb/s four-level pulse-amplitude modulation (PAM-4) transmission per channel, with an aggregate four-channel PAM-4 rate of 640 Gb/s. The results show how packaging-interface design and digital equalization can jointly improve link performance.
The researchers also tested transmission distance using the representative channel Ch1. At free-space distances of 0.5, 1, and 2 m, the bit-error rate of the 100 Gb/s NRZ signal remained below the hard-decision forward-error-correction threshold, while the 160 Gb/s PAM-4 signal met the soft-decision forward-error-correction threshold. These tests demonstrate the distance margin of the current optical configuration; the four-channel 640 Gb/s result corresponds specifically to the 0.5 m test condition.
The work demonstrates a high-speed optical wireless link that combines commercially available optoelectronic devices, standard packaging processes, and nonlinear equalization. It may inform board-to-board, intra-rack, and locally reconfigurable connections. Practical data-center deployment will require further optimization of beam alignment, channel consistency, and real-time equalization. Peng Yan, Shenghui Wu, and Yunhao Zhang are the co-first authors. Lei Wang, Haowen Shu, and Xingjun Wang are the co-corresponding authors. The study was supported by the National Natural Science Foundation of China.
Original article: https://doi.org/10.1186/s43074-026-00259-x
