Thunderbolt Interconnect—Opitcal and Copper

Abstract

Thunderbolt interconnect technology has adopted copper and optical cables. Single cable can support 2 × 20 Gb/s data rate, which is driven by 4K video. Future 8K video and virtual reality will push the bandwidth requirement even higher. Key technologies developed to enable this high data rate for consumer electronics are discussed, such as robust copper and optical cables, miniature optical engine, and 2 × 25.625 Gb/s low power integrated circuits for vertical cavity surface emitting laser based optical link. Copper and optical interconnect technologies are compared on the basis of cost, power, form factor, and scalability. Same circuit with four channels (4 × 25.625 Gb/s) can be used in 100G data center optical interconnect. Total power consumption is 146 mW for each 25.625 Gb/s optical link, which gives 5.69 mW/Gb/s. Among the commercially available optical ICs we evaluated at 25 Gb/s, this work has lowest power consumption and smallest die area in industry.