25-Gb/s Clocked Pluggable Optics for High-Density Data Center Interconnections

This brief presents a clocked pluggable optics suitable for high-density data center interconnections. The proposed architecture performs a SERDES function at the module side by exploiting a forwarded clock from the ASIC. Due to the relaxed channel loss of the ASIC-to-module interface, the use of power-hungry equalizers can be avoided. Based on an 850-nm multi-mode fiber interface, a 25-Gb/s link operation is demonstrated. A vertical-cavity surface-emitting laser-based transmitter outputs an optical modulation power of 0.6 mW. The optical receiver sensitivity is measured to be −7.5 dBm at 21.2 Gb/s with an optical excitation, and
$120~{\mu }\text{A}_{\text{pp}}$
at 25 Gb/s with an electrical excitation. The jitter tracking capability of the implemented clock and data recovery is evaluated in the presence of ±100-ppm frequency offsets and the measured jitter tolerance complies with the 100 GbE specification well. The optical transceiver is implemented in 65-nm CMOS technology and consumes 281 mW at 25 Gb/s, corresponding to the energy efficiency of 11.2 pJ/b.