A Small-Area and Low-EPB Inductive-Peaking VCSEL Driver for a 65-nm CMOS Chip

With increasing data traffic in data centers, data capacity shortages and the increasing power consumption of network-switching systems have become serious issues. Co-packaged optics (CPO) modules using a multicore fiber and vertical-cavity surface-emitting laser (VCSEL) array are promising for addressing the above issues. Inductive peaking is an effective method for extending the frequency bandwidth of a VCSEL driver. However, it is difficult to integrate multiple VCSEL drivers on the limited chip area of the CPO module because the on-chip inductor occupies a large area. In this paper, we present a small-area and low-energy per-bit (EPB) VCSEL driver for a $65-\mathrm{nm}$ CMOS chip. We fabricated an inductive-peaking VCSEL driver using self-customized on-chip inductors. Eye opening was verified at $36 \mathrm{~Gb} / \mathrm{s}$ with a power consumption of 41.6 mW by on-wafer probing electrical measurements. We achieved an EPB of $1.16 \mathrm{pJ} / \mathrm{b}$, although the occupied core area is only $124 \times 309 \mu \mathrm{m}^{2}$.