Multi-channel parallel free-space VCSEL optoelectronic interconnects for digital data transmission and processing

A free-space integrated optoelectronic interconnect was built to explore parallel data transmission and processing. This interconnect comprises an 8x8 substrate-emitting 980-nm InGaAs/GaAs quantum-well vertical-cavity surface-emitting laser (VCSEL) array and an 8x8 InGaAs/InP P-I-N photodector array. Both VCSEL, and detector arrays were flip-chip bonded onto the complimentary metal-oxide-semiconductor (CMOS) circuitry, packaged in pin-grid array (PGA) packages, and mounted on customized printed circuit boards. Individual data rates as high as 1.2 Gb/s on the VCSEL/CMOS transmitter array were measured. After the optical alignment, we carried out serial and parallel transmissions of digital data and live video scenes through this interconnect between two computers. Images captured by CCD camera were digitized to g-bit data signals and transferred in serial bit-stream through multiple channels in this parallel VCSEL-detector optical interconnect. A data processing algorithm of edge defection was attempted during the data transfer. Final images were reconstructed back from optically transmitted and processed digital data. Although the transmitter and detector offered much higher data rates, we found that the overall image transfer rate was limited by the CMOS receiver circuits. A new design for the receiver circuitry was accomplished and submitted for fabrication.