A 4-Ch × 64 Gb/s/Ch NRZ VCSEL-Based Co-Packaged Fiber-Terminated Optical TX and 80-Gb/s Optical Driver

This article introduces a four-channel (4-Ch) multi-mode (MM) vertical-cavity surface-emitting laser (VCSEL)-based co-packaged optical transmitter (TX), integrating a VCSEL array, a VCSEL driver (VCDRV) IC, an electrical TX IC, and optical fiber termination within a single package. A complex-zero continuous-time linear equalizer (CZ-CTLE) is proposed to effectively equalize the complex-pole response of the VCSEL, improving in-band gain/group delay (GD) flatness and extending bandwidth (BW). To enhance link energy efficiency and jitter margin, resonant clocking techniques are proposed, including a transmission-line-based resonant global clock distribution and a wide-tuning-range coupled-resonator-based quadrature generation. A low-power electrical TX architecture employing an NMOS-over-NMOS (N/N) voltage-mode driver with eye symmetry correction is introduced to further improve the energy efficiency and link margin. The optical TX prototype, implemented in a 22-nm FinFET process, achieves an aggregate non-return-to-zero (NRZ) data rate of 256 Gb/s with an energy efficiency of 1.3 pJ/b. This work outperforms previous optical TXs by >2.2× in optical modulation amplitude, achieving 1.4× (7.6×) greater eye width (EW) eye height (EH), with 14% higher per-channel baud rate and 11% better energy efficiency. The direct-drive optical driver achieves 80-Gb/s NRZ operation, demonstrating a 13% higher data rate and 25× better energy efficiency than prior art. This work also marks the first successful demonstration of more than 50-Gb/s VCSEL-based co-packaged optical TX topology at a 6.4× higher rate than the previous efforts.