Ultra-low-power 10 to 28.5 Gb/s CMOS-driven VCSEL-based optical links [Invited]

We report three 850 nm, vertical-cavity surface-emitting laser (VCSEL)-based optical links using 90 nm complementary metal-oxide-semiconductor (CMOS) circuits that achieve new records in speed and power efficiency. Two receiver (RX) circuit designs explore the tradeoffs between speed, power, and silicon area. The two RXs are first tested with a simple transmitter (TX), delivering full-link power efficiencies of 1.37 pJ/bit at 15 Gb/s and 3.6 pJ/bit at 25 Gb/s. An improved TX using feed-forward equalization (FFE) and an advanced VCSEL is then introduced. The link using the FFE TX achieves full-link power efficiencies of 1.5, 2.0, and 3.8 pJ/bit at 22.5, 25, and 28.5 Gb/s, respectively.